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Creative Virtual Collaboration - Fostering Creativity and Innovation in Remote and Hybrid Work Environments (2026)
Gebbing, Pia
This dissertation investigates creativity and collaboration across different levels of virtuality, including remote, hybrid, and in-person environments. It applies a user-centered Design Science Research approach, incorporating qualitative techniques such as diary studies, expert interviews, and prototype assessments to analyze performance satisfaction, preferences, and team dynamics. The academic contribution features a conceptual framework that identifies and prioritizes creativity drivers, while practical design principles are refined and tested through remote and hybrid design thinking sessions. The results indicate that supporting creative processes involves adapting environments to match task needs, based on divergent and convergent thinking. Social and environmental affordances must balance social presence, anonymity, and accountability to maintain creative momentum within virtual teams. Additionally, a functional environment combined with effective technology management is key to fostering a flow state for creativity. As a practical outcome, recommendations for improving idea sharing and development in remote and hybrid teams assist organizations in navigating digital transformation and sustainably enhancing innovation processes.
Coupled Structural and Dynamical Responses in Organic Semiconductors Probed by Time and Frequency-Resolved Spectroscopy (2026)
Ranga, Ayush Kant
Photovoltaics are a key technology in the transition toward renewable energy. Among emerging materials, poly(3-hexylthiophene) (P3HT) offers an attractive alternative to silicon owing to its solution processability, mechanical flexibility, and tunable optoelectronic properties. This thesis investigates how electric fields, mechanical deformation, and processing conditions influence the structural and photophysical properties of P3HT and the flexible substrate poly(ethylene terephthalate) (PET) using complementary time and frequency domain spectroscopic techniques. Femtosecond transient absorption pump-probe spectroscopy demonstrates that below-band-gap excitation directly generates polaron pairs (PPs) in P3HT. The transient response comprises fast PP and slower delocalized polaron pair (DPP) contributions. External electric fields modify the competition between DPP recombination and bimolecular annihilation, while uniaxial stretching up to 7% redistributes PP and DPP populations through polymer chain alignment. Above this strain, the transient response becomes increasingly complex owing to efficient strain transfer and microcrack formation. Raman and ultraviolet–visible spectroscopy correlate mechanical deformation with structural and optical changes. P3HT and PEDOT:PSS/P3HT films retain an essentially constant optical band gap up to approximately 7% strain, followed by a slight widening at 10%, indicating the onset of electronically significant deformation. Analysis of the Raman C=C and C–C stretching modes shows that variations in band position and full width at half maximum distinguish temperature-induced morphological changes from mechanically induced chain alignment. PET exhibits increased optical absorption and irreversible Raman spectral changes above approximately 5% strain, indicating molecular reorganization.
Layer-Resolved Spectroscopic Study of Tensile Strain Effects in Flexible Organic Electronic Structures (2026)
Ghorab, Mahya
This thesis investigates how uniaxial tensile strain affects the optical and molecular properties of polymer thin films used in flexible organic electronics. It focuses on poly(ethylene terephthalate) (PET) as a flexible substrate and poly(3-hexylthiophene-2,5-diyl) (P3HT) as a semiconducting polymer. The materials are examined as single layers and in PET/P3HT and PET/PEDOT:PSS/P3HT stacks at room temperature. Strain is applied reproducibly using a custom-built stretching setup. Ultraviolet–visible spectroscopy is used to track changes in optical response and band gap, while Raman spectroscopy reveals chain reorientation, conformational changes, and defect formation during and after deformation. For PET, tensile strain causes progressive optical degradation, including increased absorption across the ultraviolet and visible regions. Above ≈5% strain, the changes become irreversible and are accompanied by evidence of permanent structural modification. This identifies two regimes: elastic behavior at low strain and irreversible deformation at higher strain. For P3HT, the optical band gap remains stable up to 7% strain, regardless of annealing temperature or stack configuration. At 10% strain, a reproducible increase of about 4–5 meV appears, indicating onset of measurable electronic perturbation. Raman results show that P3HT strain response depends strongly on thermal history. Unannealed films mainly deform through reversible chain alignment. Films annealed at 50 °C show a mixed response with greater microstructural heterogeneity, while films annealed at 75 °C exhibit more constrained deformation and stronger defect accumulation. A PEDOT:PSS interlayer improves strain transfer, reduces strain localization, and enhances mechanical tolerance, especially in highly ordered films. Overall, the work defines experimentally grounded strain limits for flexible devices and clarifies how processing history and stack architecture govern mechanical and optoelectronic behavior.
Three Essays in Accounting and Taxation: Integrating Discipline-Specific Language through Digital Technologies (2026)
Schmidt, Lukas
This dissertation examines how digital technologies can support the integration of discipline-specific language in accounting and taxation. Across three essays, it analyzes the acquisition, application, and analysis of specialized terminology. Essay I investigates a wiki-based collaborative glossary in introductory accounting education and shows that it improves students' academic performance and engagement with accounting terminology, while also revealing challenges related to coordination and content reliability. Essay II uses dictionary-based text analysis to create a cross-country dataset on corporate environmental tax legislation and finds that such taxes are shaped more by institutional and political factors than by environmental risks. Essay III develops and applies a domain-specific large language model to qualitative corporate tax disclosures, demonstrating that specialized LLMs outperform general-purpose models and traditional text analysis methods. Overall, the dissertation shows that digital technologies can enhance the acquisition, application, and analysis of specialized language in accounting and taxation. It contributes to accounting education, tax policy research, and methodological debates on the use of natural language processing in discipline-specific contexts.
The Schmetterling Program: An Integrative, Evidence-Based Intervention for Autism Targeting Nutritional, Motor & Psychophysiological Dysregulation (2026)
Hassany Bajaa, Sofya
Children with Autism Spectrum Disorder (ASD) often experience difficulties in sensory processing, motor coordination, behavioral regulation, and adaptive functioning, which can limit participation in daily activities such as eating and social interaction. Selective eating is highly prevalent and may lead to nutritional and developmental challenges. The Schmetterling Program was developed as an integrative, sequential intervention targeting selective eating, motor skills, and stress regulation in children with ASD. Inspired by the concept of the “butterfly effect,” the program assumes that small, individualized therapeutic changes can produce meaningful developmental improvements. It combines established behavioral strategies such as shaping, imitation chaining, and guided modeling within a sensory-motor framework. This dissertation evaluates the effectiveness of the Schmetterling Program through three studies involving children aged 2–6 years with ASD. The first study examined the Nutritional Behavior Intervention (NBI) across three families and found improvements in dietary flexibility and adaptive behavior. The second study compared 24 children with a control group and showed reductions in selective eating, improvements in autism symptom severity, and enhanced autonomic regulation measured by heart rate variability (HRV). The third study assessed the Motor Treatment (MT) component using a multiple-baseline design and demonstrated improvements in motor coordination, sensorimotor integration, and social communication. Overall, the findings suggest that the Schmetterling Program may improve eating behavior, motor functioning, and psychophysiological regulation in children with ASD. The results support the effectiveness of integrative, individualized, and ecologically grounded interventions. Further research is required to confirm long-term outcomes and underlying neurophysiological mechanisms.
Global Bourdieu and Nigeria – Studying African Perspectives on (In)Security (2026)
Klaassen, Jan Folkert
(In)security in Africa influences African societies, geopolitics, and geoeconomics. Yet African perspectives on (in)security are rarely sought, and how African states shape their security policies remains unclear: conventional internal/external, domestic/foreign, and secure/insecure distinctions are outdated, while Western/Northern-centric social sciences and African Studies/IR literatures remain trapped in essentialisms, stereotypes, and mono-causal explanations. This thesis argues for new analytical devices to study African security policies in less essentialist and more context-sensitive ways by understanding the practice turn and appropriating Pierre Bourdieu's reflexive, practice-theoretical, and field-analytical sociology through an in-depth sociospatial reading. This helps interpret his concepts as global, interrelated thinking tools for African social formations, against a superficial Bourdieusian International Studies literature. Taking Nigeria as exploratory case study, the thesis traces how field and habitus intersect, develops a Field of Nigerian Security Policy (FNSP) as object and tool, and treats habitus and capital primarily as outcomes of the analysis. It asks how Nigeria shapes its security policy towards Boko Haram as a contemporary space of (in)security, drawing on almost four months of self-reflexive, ethnographic fieldwork. It combines sociological discourse analysis of textual sources with interviews with leading Nigerian experts and practitioners. It reveals how a FNSP is constituted by diverse agents, relations of (informal) cooperation, competition, domination, and transversality, a dual habitus of problems/scarcities and aspirations/necessities, and multiple (including negative) kinds of capital—and how agents' classificatory practices ultimately produce Nigeria's security policy towards Boko Haram. The thesis thereby advances African International Relations theoretically and offers deep practical insights into Nigeria's political space.
Planetary Surface and Subsurface Processes: Landform Detection, Radar Analysis, and Deep Learning Applications in Geosciences (2026)
Nodjoumi, Giacomo
The study of pits, skylights, and sinkholes on terrestrial bodies is vital for mapping subsurface voids, geological evolution, and potentially habitable zones. Feature identification remains constrained by sensor resolution and the complexities of radar analysis. This research explores deep learning computer vision to automate landform mapping and evaluates detecting subsurface voids using orbital radar. To address mapping challenges, this work introduces DeepLandforms, a toolkit developed to automate detection using You Only Look Once (YOLO), Detectron 2, and the Segment Anything Model (SAM). Built on Docker, it includes modules for data preparation, training, and inference, generating outputs compatible with GIS software. Validation against a dataset from the Mars Global Cave Candidate (MGC³) catalog demonstrates capacity for consistent, large-scale surveys. This research also introduces EchoTerraeTrace, an all-in-one toolkit providing workflows for SHARAD (Mars Reconnaissance Orbiter) and MARSIS (Mars Express) data. During validation North-West of Ascraeus Mons, three unmapped volcanic vents were identified, and the regional paleotopography was refined. Finally, this research assesses planetary software against FAIR principles. A web-based service built on a dockerized JupyterHub was developed as an all-in-one environment for standardized data processing. This service provides scalability without requiring local high-end resources, supporting reproducible research by moving the code to the data rather than the data to the code.
Privacy-Preservation in Set-Based Processing (2026)
Dawoud, Mohammed Mahmoud Said
In intelligent and autonomous systems, users must often share private data with external platforms to enable advanced functionalities. A key challenge in this process arises when the data to be protected is not a single, precise value, but is instead inherently uncertain or represents a range of possible values. This thesis addresses the privacy of such uncertain data, which is formally represented and processed using set-based methods. We review existing privacy-preserving techniques and introduce new mechanisms to safeguard this data during processing on untrusted platforms, exploring both cryptographic and non-cryptographic approaches. Specifically, the thesis presents novel privacy-preserving mechanisms for set-based data processing, categorized by the data type within the sets. For sets of real-valued data, we introduce a differential privacy mechanism for set-based estimation in linear and non-linear dynamical systems. This approach protects the sensitive information contained within sets, such as zonotopes that model system uncertainties, while minimizing the loss of utility for the estimation process. For sets of discrete, binary data, we propose a mechanism that uses Fast Fully Homomorphic Encryption to ensure privacy. This method allows for the secure processing of sets represented as logical zonotopes in untrusted environments, maintaining computational practicality. The evaluations demonstrate the effectiveness and practicality of the proposed mechanisms across various applications in autonomous and intelligent systems.
Collective patterns on graphs (2026)
Haj Ali, Selim
Understanding how collective patterns emerge on graphs is a fundamental challenge across disciplines, from biological and ecological networks to computational and physical systems. This thesis explores the interplay between network topology and emergent dynamics using minimal models and spectral graph techniques. A first investigation focuses on network inference, showing that Turing patterns encode structural information about the underlying graph, which we use to infer missing links. The second study investigates multistability in reaction-diffusion networks, showing how local spectral gaps influence the attractor landscape of Turing patterns using a heuristic binary classification algorithm. Finally, the third study applies the sandpile model to soil erosion processes, bridging concepts from self-organised criticality and connectivity-based geomorphology to investigate the role of minimal models in empirical research. This thesis combines theoretical analysis, computational modelling and empirical validation to highlight how structure shapes dynamics across different contexts and illustrate the potential of minimal models as predictive, explanatory and exploratory tools for complex systems.
Biogeochemical Fractionation of Rare Earth Elements within Aquatic Organisms and a Natural Freshwater Ecosystem (2026)
ZHANG, Keran
Rare earth elements (REE, or REY including yttrium) are widely used in modern technologies and are increasingly released into aquatic environments. Their environmental behaviour and bioaccumulation in aquatic ecosystems remain poorly understood. This thesis investigates the bioavailability, bioaccumulation, and trophic transfer of both geogenic and anthropogenic REY using aquatic organisms and environmental samples from European freshwater and marine systems. Shells of three invasive freshwater bivalves (Corbicula fluminea, Dreissena polymorpha, and Dreissena bugensis) collected from seven major European rivers show strong REY bioaccumulation, with concentrations up to five orders of magnitude higher than in ambient water. Anthropogenic lanthanum contamination from the Rhine River was recorded in mussel shells, whereas no enrichment of anthropogenic gadolinium from MRI contrast agents was observed, suggesting its stability in freshwater systems. Further analyses of freshwater (Anodonta anatina) and marine (Mytilus edulis) mussels reveal higher REY concentrations in internal organs than in muscle tissues and shells, while biological processes exert only minor influence on REY fractionation. A trophic-level study along the Rhine River shows a general biodilution trend from primary producers to fish, while shale-normalised REY patterns remain consistent across trophic levels. These results indicate that mussels can serve as effective biomonitors for environmental REY contamination.
The Influence of Digital Transformation on well-being – analysis of life stages and business sectors (2026)
Helms, Maximilian
The accelerating pace of digital transformation (DT) is profoundly reshaping the world of work, placing new demands on employees and affecting their well-being. As employee well-being is closely linked to engagement and performance, this PhD project investigates how organizations can engage employees during DT, with particular consideration of their well-being. The Self-Determination Theory (SDT) serves as the kernel theory in this research for understanding well-being, expanded to include physical health. Furthermore, both different working conditions and various life stages of employees are incorporated in order to capture the dynamic nature of well-being. However, promoting well-being requires a comprehensive understanding of its multifaceted effects, both positive and negative, on employees, a challenge further intensified by the ongoing DT. While many companies recognize the benefits of DT, they often struggle with its implementation and the associated impacts on the workforce. Maturity models are a common tool to provide guidance during DT by serving as frameworks for assessing and developing organizational capabilities. In practice, maturity models are often too strategic, inflexible, and insufficiently user-centered. Furthermore, social aspects such as employee well-being have so far been largely neglected. To close this gap, an adaptable human-centered maturity model focusing on well-being was designed and empirically validated within the framework of this cumulative dissertation consisting of six papers, following the Design Science Research (DSR) approach. The model uniquely integrates basic psychological needs, physical health, and life stage perspectives, dimensions largely absent in existing DT maturity models. Overall, this PhD project advances the human-centered discourse on well-being by providing a practice-oriented maturity model that supports organizations in identifying the effects of DT on well-being and deriving appropriate courses of action.
Using Markov Decision Process Model for Sustainable Assessment in Industry 4.0 (2026)
Sodachi, Majid
This thesis investigates the integration of sustainability assessment considering Industry 4.0 technologies and the use of Markov Decision Process capabilities. The manufacturing industry is facing increasing pressure to improve sustainability assessment performance, and Industry 4.0 technologies like Digital Twins, Internet of Things, Big Data Analytics, Cloud Computing, Machine Learning, and Artificial Intelligence have the potential to support these efforts. However, effectively integrating sustainability assessment goals and Industry 4.0 technologies within manufacturing systems can be challenging. The research addresses this challenge by developing a framework for optimizing the flow of operations in a manufacturing system while incorporating sustainability assessment and Industry 4.0 technologies effectively. The framework utilizes the Markov Decision Process to model the decision-making process of the manufacturing system and its decision-makers. From the other side, it includes sustainability assessment goals as constraints or objectives in the Markov Decision Process model. The use of Industry 4.0 technologies is integrated into the framework to gather data and optimize the decision-making process based on that data. The thesis begins by reviewing the literature on sustainability assessment, Industry 4.0 technologies, and their impacts with regard to manufacturing systems. The proposed framework is then presented, and its capabilities are demonstrated through case studies of single and multiple agents on a shop floor. The trend in pioneer manufacturing firms is to implement new technological applications on their shop floor to agile their Manufacturing Execution System. The findings from the case study indicate that the proposed framework can effectively support decision-making at the top-tier level of the enterprise by integrating sustainability assessment and the Industry 4.0 paradigm.
AI-Driven Real-Time Data and Neural Synthesis in German Transport (2026)
Yelikbayeva, Aigul
This research paper investigates the advanced Artificial Intelligence (AI) architecture underpinning Germany's multimodal transportation ecosystem, drawing from the author's year-long immersive professional experience. The study shifts the focus from traditional physical logistics to the efficiency of data processing throughput, characterizing the transport network as a dynamic information organism. The author analyzes the integration of Edge Computing and IoT sensors through the MQTT protocol, facilitating resilient data transmission in unstable environments. Furthermore, the paper details the implementation of Real-time Stream Processing using Apache Kafka and Redis, alongside the application of LSTM (Long Short-Term Memory) neural networks for high-precision delay forecasting. A significant technical analysis is provided on Neural Text-to-Speech (NTTS) synthesis for passenger notifications, emphasizing its role in enhancing user experience (UX) through natural language generation. Beyond technical frameworks, the author addresses critical infrastructure security via TLS 1.3 and PKI, ensuring compliance with GDPR standards. The paper concludes that the success of modern transport lies in its "algorithmic soul"—a data-driven approach that prioritizes reliability and transparency. Ultimately, the author advocates for the strategic transfer of these AI-integrated architectures to Kazakhstan’s "Smart City" initiatives, suggesting that such digital transformation will serve as a catalyst for the broader technological evolution of the national economy.
An Intelligent learning management platform for Data-Driven course improvement (2026)
Bekmoldayeva, Assel
Modern online courses often replicate traditional instruction as static artifacts, failing to reveal the cognitive causes of learner errors. This paper proposes a self-improving educational ecosystem integrating interactive modules, diagnostic assessments, and AI-driven analytics in a closed feedback loop. The model is implemented on a real platform using WordPress as a flexible application framework. Each module combines theory, interactive practice (H5P), and diagnostic assessment. Natural-language queries to an AI assistant serve as diagnostic signals, revealing hidden cognitive barriers. A three-level management model separates operational support (AI tutor), pedagogical quality assurance, and strategic product development. Continuous improvement follows a four-stage cycle: signal collection, pattern analysis, targeted instructional adjustments, and impact verification. This approach demonstrates that intelligent, evidence-based learning management can transform courses into self-correcting systems, where each cohort improves the experience for the next.
The Human Factor in Digital Transformation: An Employee-Centered Change Management Maturity Model for the AI Era (2026)
Bosbach, Julia
Digital transformation (DT) fundamentally reshapes organizational structures and work processes. Despite its strategic importance, up to 70% of DT initiatives fail, primarily due to insufficient consideration of human factors. This cumulative dissertation addresses this gap by developing and validating a human-centered Change Management Maturity Model that systematically integrates employee needs into digital transformation processes, with particular emphasis on the AI-driven third phase of DT. Existing DT maturity models predominantly focus on technological, strategic, and organizational aspects while neglecting human-centered dimensions such as employee motivation, psychological well-being, and change readiness. Likewise, established change management frameworks tend to operate either at the organizational level (e.g., McKinsey 7S) or the individual level (e.g., ADKAR), without systematically integrating both perspectives. To address this limitation, this dissertation proposes a comprehensive maturity model comprising nine dimensions across three categories: Motivation & Leadership Behavior, Dealing with Change, and Well-being & Health. The research follows an echeloned Design Science Research (eDSR) approach and is structured as a cumulative dissertation consisting of six research papers. The model is grounded in multiple kernel theories, including Self-Determination Theory, Herzberg’s Two-Factor Theory, Maslow’s Hierarchy of Needs, the Dynamic Capabilities Framework, and established change management models. Empirical validation was conducted in the skilled trades sector and across industries in the retail sector, demonstrating the model’s applicability across organizational contexts and its practical relevance for managing AI-driven transformation initiatives.
Trends in the Development of Digital Tools for Inclusive Early Childhood Education with a Focus on Social Skills (2026)
Arzymbetova, Sholpan
Digital tools are increasingly used in inclusive early childhood education and care (ECEC) to support children’s social skills — especially communication, emotion recognition, self-regulation, prosocial behavior, and peer interaction. Across Europe, policy momentum for inclusive digital education is accelerating, while research is expanding from general “screen time” debates toward evidence-based, developmentally appropriate, educator-mediated designs. This paper synthesizes current trends, highlights the European and German context, and proposes a feasible mixed-method study plan to evaluate digital social-skills interventions in inclusive ECEC settings. The review maps tool categories (tablet apps, serious games, social robots, multimodal platforms, and digital assessment/screening), describe equity and accessibility design principles, and identify evidence gaps (long-term outcomes, implementation fidelity, child-led vs. adult-guided interaction, and inclusion of multilingual/migrant families). We propose a pragmatic evaluation framework aligned with European priorities for accessibility, quality, and teacher capacity-building.
Mathematical Modeling and Process Optimization of Composite Polymer Stabilizers (2026)
Artykova, Zhadyra
This paper examines current mathematical modeling methods used for the development and optimization of composite polymer stabilizers. A review of key challenges related to the stability of polymer materials is provided, along with a discussion of modern computational approaches, including molecular dynamics, finite element analysis, thermodynamic modeling, and machine learning. The necessity of an interdisciplinary approach integrating chemistry, materials science, and computational technologies is justified. Perspectives on the further development of modeling methods to enhance the efficiency and stability of polymer stabilizers are presented.
AI Integration in Education: Opportunities and Challenges (2026)
Amdamova, Raviya ; Aitmetova, Sholpan
The research essay examines the opportunities and barriers to implementing artificial intelligence (AI) in the education system of the Republic of Kazakhstan based on a comparative analysis of the experience of Germany. The aim of the work is to identify key factors influencing the successful integration of AI tools into educational practice, including regulatory, methodological, technological and personnel aspects. The paper analyzes international and national strategies for regulating AI, features of the legal framework of Kazakhstan and the European Union, as well as models of teacher training. Special attention is paid to the issues of academic integrity, ethics, personal data protection and overcoming the digital divide. Based on the German experience, we formulate systematic recommendations for Kazakhstan aimed at developing institutional teacher training, reforming the assessment system and forming national AI sovereignty in education. The forecast of AI development in the educational system of Kazakhstan until 2029 is made, emphasizing the need to move from fragmented technology implementation to a sustainable, ethically verified and inclusive model of digital education.
AI tutors: replacing or supporting human teachers (2026)
Sambetova, Meruyert ; Khudaibergenova, Zhanar
This essay examines the role of artificial intelligence tutors in Kazakhstan's education system, addressing whether AI-based tools replace teachers or serve as supportive instruments that enhance teaching practice. Against the backdrop of ongoing digital transformation in education, the central thesis argues that AI tutors do not replace teachers but function as complementary tools that assist with specific tasks such as assignment evaluation, progress monitoring, and personalized feedback. While AI systems offer significant advantages — including personalized learning pathways, expanded access to educational resources in underserved rural areas, and reduced administrative burden for teachers — they cannot substitute essential pedagogical elements such as human interaction, emotional intelligence, cultural awareness, and moral guidance. The analysis draws on theoretical frameworks from UNESCO and OECD, examining both the potential and limitations of AI integration within Kazakhstan's educational context, where regional disparities in infrastructure and digital literacy create uneven implementation. Through comparative insights from Germany's education system, the essay demonstrates how AI tutors can be effectively integrated as supportive tools while preserving the teacher's central role in pedagogical decision-making and student development. The findings emphasize that successful AI integration requires maintaining human oversight, addressing the digital divide, and ensuring that teachers retain professional autonomy in shaping educational outcomes.
Integration of Artificial Intelligence in Education: Opportunities and Challenges (2026)
Bakhtiyarova, Gulzhan ; Pshkeyeva, Darkhan
This paper examines the integration of artificial intelligence (AI) into the education system, focusing on its key opportunities and challenges in the context of the Fourth Industrial Revolution. Artificial intelligence has become an important tool for modernizing education, enhancing learning quality, supporting personalized instruction, and improving educational management processes. The study is based on a comparative analysis of the experiences of Germany and Kazakhstan in implementing AI in education. The German model emphasizes strategic planning, teacher training, and ethical and legal regulation, while Kazakhstan’s approach focuses on accessibility and rapid implementation through widely used EdTech platforms. The findings indicate that the effective use of artificial intelligence depends not only on technological infrastructure but also on teacher readiness, data security, and ethical responsibility. The paper highlights the potential of AI to transform education and identifies the key conditions for its sustainable and balanced integration.
Robust Underwater Perception: Using Multimodal and 3D Visual Cues to Boost Machine Learning Frameworks in Marine Applications (2026)
Gomez Chavez, Arturo
Underwater robots need reliable perception for navigation, mapping, diver interaction, and manipulation, yet vision is degraded by wavelength-dependent attenuation, scattering, and variable water optics. These effects reduce contrast, distort color, and destabilize visual cues, so perception must be tailored to underwater image formation and field reliability constraints. This thesis develops multimodal, 3D-aware perception for adverse marine and deep-sea conditions, based on experiments and integration within the EU projects MORPH, CADDY, and DexROV. By combining complementary sensors (2D imagery, stereo 3D structure, inertial and acoustic cues) with learning pipelines, the approaches compensate for individual sensor weaknesses. First, it enriches 2D perception with 3D context and underwater-specific enhancement. Contributions include terrain-complexity estimation from texture metrics and stereo geometry to adapt AUV speed during surveys, plus color restoration/image enhancement to improve detection and pose estimation. For human-robot interaction, it introduces diver detection and pose estimation that merge stereo point-cloud descriptors with recurrent neural networks to handle low-contrast imagery. Second, it presents end-to-end systems, including the CADDY underwater stereo-vision dataset for gesture-based communication and a gesture-recognition pipeline that blends classical learning, deep detectors, and a grammar-guided human-in-the-loop design for safer diver and AUV communication. Finally, for deep-sea intervention, it proposes a simulation-in-the-loop validation to reduce sim-to-real gaps and an adaptive localization framework fusing dense 3D reconstruction, planar geometry, image-quality cues, and visual odometry to maintain accurate navigation in low visibility. The methods are validated on real data and integrated into autonomous demonstrators for safety-critical missions during field trials.
Digital Competence Framework for Teachers: Implementation Gap (2026)
Abatova, Zhadyra ; Kenesbay, Gulnur ; Bauzhanova, Nassima
This technical report provides a comprehensive analysis of the process of digital transformation in the education system of Kazakhstan, particularly in the context of the implementation gap between the standards of digital competence and the current state of the education system. The research is based on the application of two main methodological models for the evaluation of the level of educator competence, in which the European Framework for the Digital Competence of Educators is considered the scientific basis for the analysis of the areas of professional growth, while the TPACK model is applied to evaluate the efficiency of the educational process in the context of the intersection of technology, pedagogy, and subject matter content. The analysis of the empirical data of the TALIS-2024 study allows for the qualitative comparison of the current state of the education system in Kazakhstan with the global trends in the context of OECD countries. It is stated that the educators of Kazakhstan exhibit a high level of "Digital Optimism," in which the level of teacher confidence in the level of technological knowledge is recorded at 75.12 points, which is significantly higher than the OECD average of 70.1. However, it is important to note that, in spite of the high level of self-assessment, there is a significant need for professional growth, in which 46.59% of educators require the acquisition of basic ICT skills. The progress in the development of the education system is limited by the "infrastructure ceiling," in which there is a lack of digital resources in 22.83% of the schools and unstable internet access in 22.69% of the educational environment. The research also further highlights how Kazakhstan’s most important asset in this process of change is its already existing culture of professionalism and mutual support. It has also been recommended that, while systemic changes are necessary at a national level, teachers themselves need to take an active role in developing their own personal Digital Roadmap. This involves a systematic process of self-assessment through the DigCompEdu SELFIE tool, with a further need for teachers to develop their Technological Knowledge (TK) in order to more effectively integrate this into TPACK. In conclusion, it has been established how Kazakhstan already has a robust foundation of digital optimism, with a world-class culture of teacher support. By closing the already existing infrastructure gap, it is considered that the potential for digital excellence within schools throughout Kazakhstan is limitless.
Personalized learning based on AI and gamification: comparing the experience of Germany and Kazakhstan (2026)
Makhambetova, Gaziza ; Duisenbekova, Makpal
Artificial intelligence (AI) and gamification are becoming important tools in modern education. Gamification uses elements such as points, rewards, and challenges to increase student motivation and engagement. However, its effectiveness depends on learners’ interests, abilities, and the quality of game design. Personalized learning aims to adapt content and tasks to individual student needs, but teachers often struggle to do this in traditional classrooms due to limited time and large class sizes. AI can support personalization by analyzing student performance, participation, and learning difficulties. Based on this data, AI systems can recommend appropriate materials, adjust task difficulty, and create individual learning paths. This article compares educational platforms in Germany and Kazakhstan. Germany is well prepared to integrate AI into education and widely uses AI-based personalization and gamification. In contrast, many Kazakhstani platforms rely mainly on video lessons with limited interactive features. The article also presents the educational chatbot “Help YOU!” for schools in Kazakhstan. By combining AI and gamification, the chatbot provides personalized student support and reduces teachers’ workload, demonstrating the potential of these technologies to improve education.
Integrating EdTech and Artificial Intelligence into School Education through the Lens of Strategic Management: The Experience of Developed Countries and Kazakhstan (2026)
Bekmoldayeva, Assel ; Yelikbayeva, Aigul
This longitudinal research paper investigates digital transformation of the traditional education sector of Kazakhstan as it pertains to Edtech (educational technologies) and progressive use of artificial intelligence (AI) in classrooms by developing a strategic approach to the creation of an eco-system of education on a national level. The focus of the study is to investigate the barriers that need to be addressed to enable Kazakhstan to achieve its goal of transitioning to an eco-system of education. Research Problem: The current situation in Kazakhstan is that billions of dollars have been invested in the creation of a digital infrastructure to support the implementation of digital initiatives throughout the country. However, the country has been unable to bring its diverse digital initiatives together into a cohesive programme due to the fact that there is still a gap between the ability of the country to implement technology and the improvement of educational outcomes of its students. The primary hindrance to bringing together the successful use of all of the technologies being implemented is due to a lack of a comprehensive strategy to integrate and govern the use of technology in education. Methodology: To develop the recommendations for transitioning Kazakhstan to the creation of an eco-system of education, the researchers utilised a comparative analysis of three strategic models of Edtech governance from leading educational systems of Singapore, Finland, and Germany. The rationale for choosing these three countries is based on the differences in their methods of implementation in education.
Internal Governance and Performance of Universities in the Context of New Public Management and Stratification of Higher Education (2026)
Platonova, Daria
In this thesis, I examine the relationship between internal governance and university performance within the context of Russian higher education from 2012 to 2020, a period marked by the prominent application of New Public Management (NPM) instruments. This study investigates several dimensions of internal governance and its connection to university performance. First, how do internal governance characteristics - such as centralization, stakeholder involvement, external communication, and strategic orientation - relate to university performance? Second, is there a relationship between institutional strategy adoption and university performance from the perspective of university department heads? Additionally, I explore the institutional structures and governance arrangements in Russian higher education, with particular attention to two interrelated developments: the adoption of NPM instruments and system stratification. The study draws on data from a national-level survey of university leaders and administrators, complemented by statistical information. Depending on the data structure and variable characteristics, various quantitative methods - from simple difference tests to conditional efficiency estimations - will be applied to address the research questions.
Identification and characterization of small molecules targeting the E. coli AcrAB-TolC efflux pump (2026)
Szal, Tania
This dissertation focuses on the identification and characterization of efflux pump inhibitors targeting the main tripartite efflux pump in Escherichia coli, AcrAB-TolC. Tripartite efflux pumps are integral membrane complexes that confer antimicrobial resistance to Gram-negative bacteria by extruding antibiotics. Inhibiting efflux systems with small molecules represents a promising strategy for extending the spectrum of antibiotics, and restoring antibiotic susceptibility in multidrug-resistant bacteria. However, no efflux pump inhibitors have been approved for clinical use so far. Two substances, LP-115 and carmofur, that represent a basis for the development of novel efflux pump inhibitors were discovered, while postulated AcrA inhibitors were shown to be non-specific binders. LP-115 was identified employing an in silico repurposing screen targeting the outer membrane factor TolC followed by microbiological validation and deconstruction of a hit compound into fragments. Binding to TolC and AcrB was confirmed using MST, and a ligand-induced destabilization of the efflux pump complex assembly was observed using dynamic light scattering. Cryo-EM provided detailed molecular insights into the binding site at the AcrA-TolC interface. Our results suggest that LP-115 is an efflux pump inhibitor with a novel mechanism of action that consists of disrupting the AcrAB-TolC efflux pump assembly. Carmofur was identified employing a microbiological repurposing screen focusing on antimicrobial potentiating effects, followed by microbiological and biophysical characterization of the interaction with the isolated efflux pump subunits using microscale thermophoresis, nano differential scanning fluorimetry, and dynamic light scattering. The synergistic activity of carmofur in combination with an AcrAB-TolC substrate was TolC-dependent and specific binding to TolC was observed. Thus, carmofur could be used as starting point for the development of novel efflux pump inhibitors.
Rare Earth Elements in the Environment and Their Transfer Across the Hydrosphere-Biosphere Interface: Examples from Freshwater and Marine Systems (2025)
Zocher, Anna-Lena
Our modern society relies heavily on the availability and utilisation of rare earth elements and yttrium (REY) for high-tech products and processes, which provokes a growing release of these metals into the environment and draws attention to biological and ecotoxicological consequences of their increasing concentrations in the environment. However, research has long neglected the environmental behaviour of REY. Coupled with publications including incomplete REY sets or data of questionable analytical quality, many open questions remain. This dissertation investigates samples from the biosphere and from the hydrosphere to shed light on the REY transfer at their interface. Duckweeds, widely occurring small water plants, and Norwegian fjord waters together with Baltic Sea outflow samples were chosen as main study objects from the biosphere and the hydrosphere, respectively. The findings of the biosphere-focused part improve the characterisation of the duckweed reference material BCR-670 (Lemna minor) and highlight the necessity of comparable sample processing for validation of data quality. All naturally grown duckweeds investigated are REY quasi-hyperaccumulators and share similarly shaped, mildly fractionated shale-normalised REY patterns without positive anthropogenic Gd anomalies, regardless of whether they grew in waters with or without anomalous Gd enrichment. The hydrosphere-focused part presents the first evidence for constant anthropogenic Gd input into the Baltic Sea outflow. The data combined with literature data further suggest that this signal is transported to southern Norway. In future, it may reach fjord waters further north along the Norwegian coast. Overall, this dissertation provides important new information about the fate of geogenic and anthropogenic REY at the hydrosphere-biosphere interface and highlights the relevance of basic research as the basis for understanding the complex REY transfer mechanisms across environmental compartments.
Microbial insights into ocean alkalinity enhancement: Bacterial community risk assessment and the benefit of increasing research on carbonic anhydrase (2025)
Antoni, Dominik
Climate change driven by anthropogenic CO₂ emissions requires effective mitigation strategies. Negative emission technologies (NETs), particularly ocean alkalinity enhancement (OAE), are promising because they increase ocean alkalinity and promote CO₂ sequestration. This dissertation examines how marine molecular biology can help assess ecological risks and the overall efficacy of OAE. It presents two risk assessments on bacterial community responses to alkalinity exposure and develops a framework for a novel biological proxy for monitoring, reporting, and verification (MRV) in OAE. Chapter 1 provides a general introduction. Chapter 2 investigates how gradually increased alkalinity affects pelagic bacterial communities using a mesocosm experiment with 16S rRNA gene sequencing and flow cytometry. Results show high structural resilience, but quantitative shifts in bacterial abundance linked to phytoplankton dynamics indicate indirect ecological effects of OAE. Chapter 3 expands this work by comparing two OAE strategies: olivine dissolution and direct dissolved alkalinity addition. A mesocosm experiment assessed microbial responses in seawater and oyster gills (Ostrea edulis). Olivine increased pollution-tolerant and biofilm-forming taxa, while dissolved alkalinity caused minimal change. These findings suggest that dissolved alkalinity below 500 µmol L⁻¹ is a relatively safe OAE approach. Chapter 4 proposes carbonic anhydrase (CA), a key enzyme in marine carbon cycling, as a biological proxy for evaluating OAE performance. Structured hypotheses outline how CA expression and activity assays could support future OAE MRV systems. The chapter recommends shifting resources from broad bacterial community assessments toward investigating how alkalization affects CA.
Simultaneous Localization and Mapping (SLAM) as a Core Component for Open and Affordable Autonomous Underwater Vehicles (AUV) (2025)
Hansen, Tim
Mapping challenging confined underwater environments pushes the boundaries of what is possible for state-of-the-art robotics. Current state-of-the-art high-performance equipment allows already for accurate mapping in such scenarios. However, these systems are often expensive. Affordable underwater robotic systems and sensors come with significantly reduced capabilities. Especially sonars are necessary for mapping unknown environments, due to cluttered water resulting in bad visibility for vision based sensors. Yet, affordable sonar sensors suffer from higher noise levels, reduced accuracy, and limited coverage. Consequently, developing methods to achieve reliable and accurate mapping of challenging environments with affordable hardware remains an open research question. This thesis presents a Fourier-SOFT in 2D (FS2D) registration method for robust matching of high-noise 2D sonar scans. A Simultaneous Localization and Mapping (SLAM) framework designed to the unique challenges of affordable Mechanical Scanning Sonars (MSS) is presented, integrating this FS2D registration method. In the context of the digitization of cultural heritage, the Bunker Valentin Memorial in Bremen is surveyed, and maps of its multiple basins are generated. Additionally, this thesis contributes an open dataset with accurate ground truth for development and benchmarking 2D sonar navigation, mapping, and SLAM algorithms. Overall, this thesis demonstrates that, when the unique characteristics of affordable hard ware are considered correctly, and the methods are designed accordingly, affordable underwater robots can effectively map and explore challenging, unknown environments. The BlueAUV design, the FS2D registration method, SLAM framework for affordable hardware, and an openly available dataset provide a foundation for advancing robust mapping of challenging underwater environments within the research community.
Towards a Data Driven, Scalable and Intelligent Industrial Demand Response: AI, Automation, and the Computing Continuum (2025)
Bashyal, Atit
Industrial Demand Response (IDR) systems have emerged as a key enabler for enhancing grid flexibility, particularly as industries face increasing pressure to optimize energy consumption and integrate with renewable energy sources. However, despite their potential, the adoption and scalability of IDR solutions are limited by a range of technical, infrastructural, and organizational challenges. This dissertation investigates how emerging digital technologies—namely, Artificial Intelligence/Machine Learning (AI/ML) and the computing continuum (edge, fog, and cloud computing)—can be leveraged to overcome these limitations and enable scalable, intelligent, and interoperable IDR architectures. The study addresses three core research questions. First, it develops a taxonomy of barriers to IDR adoption, distinguishing between technological and non-technological constraints. Second, it explores how distributed computing paradigms can mitigate these challenges by enabling real-time, privacy-aware, and latency-sensitive decision-making across industrial sites. Third, it examines the synergistic integration of AI/ML within the computing continuum, emphasizing methods such as federated learning, transfer learning, and multi-agent reinforcement learning to overcome issues related to data sparsity, system complexity, and semantic heterogeneity. A reference architecture for IDR aggregators is proposed, combining layered intelligence, semantic interoperability, and orchestration mechanisms. This architecture is mapped to real-world cloud and open-source platforms to demonstrate its practical applicability. The findings confirm that the integration of AI/ML and distributed computing is not only feasible but essential for advancing the resilience, autonomy, and responsiveness of future industrial energy systems.
Automation of error reporting processing based on stack trace analysis (2025)
Khvorov, Aleksandr
The rapid growth of large-scale software systems has led to the adoption of automatic error reporting platforms collecting millions of crash reports from real users. Central to these reports is the stack trace — a record of function calls leading to failure — which serves as a crucial diagnostic resource. However, the sheer volume, diversity, and redundancy of reports create bottlenecks: developers are overwhelmed by duplicates and highly variable submissions from the same defect, impeding efficient issue resolution. Existing deduplication and triage solutions in industry and academia mainly rely on string-matching, information retrieval, or graph-based heuristics. While efficient, string and IR methods often miss semantic and contextual nuances; graph-based models lose detail about individual reports, reducing accuracy. These limitations cause missed linkages between related errors and fragmentation of bug databases. The lack of scalable algorithms, real-world benchmarks, and advanced learning methods further restricts current tools. This dissertation advances automation of error report processing via stack trace analysis. It introduces (1) hybrid similarity metrics extending traditional techniques, (2) deep learning models for robust similarity estimation, (3) aggregation strategies leveraging group-level information, (4) scalable solutions for industrial use, (5) the first models for automated developer assignment in stack trace–centered triage, and (6) methods for interpreting and highlighting the most informative stack frames. The research is validated on multiple proprietary and open datasets, including new benchmarks released as part of this work. Together, these contributions provide a unified, reproducible foundation for scalable, accurate, and actionable error report deduplication, grouping, assignment, and tooling in real-world software engineering.
Synthesis and Characterization of Dimethylarsinate-Functionalized Reduced Polyoxometalates (2025)
Siby, Vinaya
This dissertation presents the synthesis of novel reduced POMs functionalized with dimethylarsinate groups. Chapter 1 introduces POMs, emphasizing polyoxomolybdates. Chapter 2 reviews organofunctionalized POMs and the rationale for this study, building on prior work with dimethylarsinate-functionalized molybdenum POMs. Chapter 3 covers experimental methods, characterization techniques, and synthesis of heterophosphonic and arsonic acid ligands. Chapter 4 describes the synthesis and characterization of eight dimethylarsinate-functionalized phosphomolybdates(V), [RPMoV6O15(OH)3{AsO2(CH3)2}3]2− (R = H, HO, CH3, HO2CCH2, HO2CC2H4, C6H5, 4-FC6H4, 4-F3COC6H4), the monoanionic mixed-valent heptamolybdate [HOMoVIMoV6O15(OH)3{AsO2(CH3)2}3]−, and d-block metal-substituted analogues [MPMoV6O15(OH)3{AsO2(CH3)2}3]2− (M = Fe2+, Ni2+, Mn2+). Chapter 5 focuses on the synthesis, structural features, and antibacterial properties of eleven dimethylarsinate-functionalized arsenomolybdates(V), [RAsMoV6O15(OH)3{AsO2(CH3)2}3]2− (R = HO, CH3, C2H5, C6H5, 3,5-(HOOC)2C6H3, 4-FC6H4, 4-F3CC6H4, 4-F3COC6H4, 4-BrC6H4 and 4-N3C6H4) and [AsIIIMoV6O15(OH)3{AsO2(CH3)2}3]3−. All compounds were synthesized in aqueous media and characterized in the solid state by single-crystal X-ray diffraction, TGA, elemental analysis, FT-IR, and PXRD, while their stability in solution and the gas phase was probed using multinuclear NMR (1H, 31P, 19F, 13C), ESI-MS, ion mobility MS, and MS/MS. Chapter 6 describes the synthesis and characterization of a novel heterometallic, dimethylarsinate-capped wheel-type POM, MoV12WVI18O84{AsO2(CH3)2}18]18− (Mo12W18), prepared under mildly acidic aqueous conditions, with alternating MoV2 and WVI3 units forming a ring with a ~1.5 nm central cavity. Its solid-state and solution behavior were probed using single-crystal XRD, IR, TGA, elemental analysis, MAS and CPMAS NMR, multinuclear solution NMR (1H, 13C, 183W, DOSY), UV-Vis, Raman spectroscopy, and SAXS.
Digitalization and Lean Management as Tools for Increasing Efficiency in the Transport Industry (2025)
Saukhimov, Askar ; Omarova, Aliya
The essay explores the integration of digitalization and Lean management in the transport industry, emphasizing their combined role in enhancing efficiency, flexibility, and sustainability. It outlines the origins of Lean management in the Toyota Production System and its adaptation to logistics and transport through practices such as 5S, Kaizen, and Just-in-Time. The paper highlights successful examples from global companies like DHL, UPS, Delta Airlines, and DB Schenker, demonstrating measurable improvements in productivity and cost reduction. Digital technologies—including the Internet of Things, Artificial Intelligence, Big Data, and digital twins—strengthen Lean principles by enabling real-time data analysis, automation, and predictive decision-making. The essay also examines Germany’s leadership in transport digitalization and describes practical observations from the Mercedes-Benz plant in Bremen. Finally, it discusses challenges such as cybersecurity, integration complexity, and ethical concerns, concluding that the synergy between Lean and digitalization forms the foundation for the future of transport—making it smarter, greener, and more resilient in the global economy.
Consistent Scalable Processing of Data Streams in a Distributed Environment (2025)
Trofimov, Artem
This thesis investigates consistency challenges in distributed stream processing systems. Prior work on this topic has made significant progress, with many ideas being implemented in state-of-the-art Stream Processing Engines (SPEs). In this thesis, we focus on formal modeling to better characterize existing problems and explore potential improvements. We introduce a formal model of delivery guarantees and show that deterministic SPEs can theoretically achieve lower latency than non-deterministic ones for exactly-once guarantee. This is supported by experimental results demonstrating that a novel deterministic implementation performs better than current alternatives. The thesis also presents a formal model for substream management, identifying a lower bound on the additional network traffic required for detecting substream termination. A corresponding framework is implemented that meets this bound and demonstrates improved performance over existing approaches. These results contribute formal foundations and practical techniques for improving the performance and predictability of distributed stream processing systems.
Sustainable Wastewater Phycoremediation, Resource Recovery and Bioproduct Development towards a circular economy. (2025)
Dey, Rohit
Rapidly expanding anthropogenic activities are generating increasing volumes of wastewater globally each year, the majority of which remains inadequately treated before being released into aquatic ecosystems. Microalgal technologies offer a promising alternative for nutrient recovery in wastewater treatment, demonstrating significant advantages over conventional methods that are often energy-intensive and costly. Inadequate treatment not only leads to environmental pollution but also results in the irreversible loss of valuable nutrients, thereby disrupting the nutrient cycle. In recent years, the extraction of bioactive compounds from microalgae has attracted substantial attention. However, much of the research has remained confined to laboratory-scale studies with a focus on either energy efficiency or bioproduct synthesis, limiting their practical applicability. A major bottleneck in the scalability of algal-based systems is the energy- and cost-intensive nature of biomass harvesting, which can contribute up to 20–30% of total downstream processing costs. Additionally, the dependence on sunlight and large land areas further restricts the feasibility of microalgae-based wastewater treatment technologies in diverse environments. This study addresses three critical challenges associated with algae-based wastewater treatment. First, an innovative cultivation approach was developed to enable continuous wastewater treatment across two contrasting seasonal conditions—summer and winter. Second, the characteristics of wastewater post-treatment were analysed to identify fouling factors affecting the harvesting process. Third, a novel strategy was implemented to induce “hyper compensation” and “luxury uptake” of inorganic phosphorus by microalgae, achieving an exceptional phosphorus recovery rate of nearly 96%. To fully capitalize on the treated biomass, a novel bioplastic/bio-composite was developed by combining polylactic acid with phosphorus-enriched microalgae.
Minimal models of dynamics on graphs to study generic structural-functional connectivity relationships (2025)
Voutsa, Venetia
The relationship between network structure (structural connectivity, SC) and network representations of dynamics (functional connectivity, FC) is a topic of high scientific interest both for advancing theoretical understanding of complex systems and for its relevance to a wide range of applications. In this thesis, correlations between structural and functional connectivity were investigated distinguishing between synchronous and sequential activity of the nodes. The primary analysis encompasses applying different dynamical models to network architectures to explore how SC/FC correlations are shaped by variations in network topology, coupling strength, and intrinsic system parameters across excitable, chaotic, and oscillatory dynamics. A more detailed investigation was conducted on regular graphs of coupled logistic maps. Symbolic encoding of the initial dynamics was used to construct equivalent cellular automaton models, followed by an analysis of the structure of their resulting attractors. The influence of noise on SC/FC correlations was also explored. Finally, SC and the two types of FC were conceptualized in a hydrological case study. Structural and functional networks were constructed from data collected in the Walnut Gulch Experimental Watershed (Arizona, USA). SC/FC correlations served as metrics to describe event-level hydrological responses of the watershed after various rainfall events, and their relationships to hydrological quantities were analyzed.
Engineering Plasma Membrane Transporters to Improve Organic Acid Production (2025)
Rendulić, Toni
Succinic acid (SA) is one of the most promising bio-based platform chemicals, as it can serve as a precursor in the synthesis of many industrially relevant chemicals and polymers. Yeasts are particularly desirable microbial hosts for SA production because they tolerate low environmental pH, allowing the direct production of the undissociated form of the acid, which results in a significantly simpler and more cost-effective overall process. The fermentation performance of yeast cell factories heavily depends on the activity of membrane transporters responsible for substrate import, metabolite exchange between intracellular compartments, and SA export from the cell. As such, membrane transporters represent key targets in metabolic engineering efforts and are the primary focus of this work. The first part of this thesis provides new insights into plasma membrane transporters from the acetate uptake transporter (AceTr) family, namely Ato1 and SatP, by identifying amino acid residues critical for their specificity and activity. This includes the engineering and characterisation of Ato1 and SatP variants capable of transporting SA in S. cerevisiae. The impact of these transporter variants on extracellular SA accumulation is assessed and compared with that of Dct-02, a known fungal SA exporter, revealing that AceTr homologues and Dct-02 have opposing effects on SA production in S. cerevisiae under industrially relevant conditions. The second part of this thesis optimizes SA production from glycerol via the CO₂-fixing reductive TCA pathway in S. cerevisiae. To increase carbon flux through this cytosolic pathway, mitochondrial membrane transporters are identified as particularly attractive engineering targets. Overall, this work expands the understanding of membrane transporters relevant for SA production and improves the fermentation performance of existing SA-producing yeast cell factories.
The human cytomegalovirus (HCMV) glycoprotein US6 inhibits the cytosolic DNA-induced type I interferon response (2025)
GHANWAT, SWAPNIL SUBHASH
The innate immune response is the first line of defense against viral infection. Host pattern recognition receptors (PRRs) detect pathogen-associated molecular patterns (PAMPs) and trigger several signaling pathways following viral infections. One such pathway, the cGAS-STING pathway, detects cytosolic DNA to induce the production and secretion of type I interferons. The cGAS-STING pathway is activated by the presence of cytosolic DNA. cGAS (cGMP-AMP synthase), a cytosolic DNA detector, binds double-stranded DNA, dimerizes, and catalyzes the production of the second messenger cyclic GMP-AMP (cGAMP) from GTP and ATP. STING, an ER adaptor protein, binds to cGAMP and becomes activated through dimerization, which results in its trafficking from the ER to the Golgi. At the Golgi, STING recruits the kinase TBK1 and the transcription factor IRF3. TBK1 phosphorylates STING, itself, and IRF3. Phosphorylation activates IRF3, causing its translocation to the nucleus, where it induces the production of type I interferons. To counteract the host immune response, human cytomegalovirus (HCMV) encodes several immunoevasin proteins. HCMV glycoproteins such as US6 inhibit antigen presentation by blocking peptide transport via the transporter associated with antigen processing (TAP). The region spanning amino acids 89–108 of US6 was identified as responsible for TAP inhibition. Our studies have identified a novel interaction and function of US6. For the first time, we show that US6 interacts with the host p24 proteins TMED2 and TMED10. US6 inhibits the cytosolic DNA-triggered cGAS-STING pathway and reduces the production of IFNβ1. We have discovered a correlation between the binding of US6 to TMED2 and TMED10 and its ability to inhibit the production of type I interferons. Using sequential mutants, we show that US6 possesses two distinct and separable regions responsible for its functions. Microscopy reveals that US6 delays STING trafficking from the ER to the Golgi.
Physical aspects of symmetry breaking in Bose gases at thermal equilibrium (2025)
Schelle, Alexej
The theory of non-interacting Bose gases is supplemented by a numerical quantum field description with a two-dimensional non-local order parameter that allows the modeling of wave-like atomic correlations and interference effects in the limit of low atomic densities. From the present model, it is possible to explain symmetry aspects of non-interacting and very weakly interacting Bose gases in the limit of fluctuating particle numbers, like the forward propagation of time and the relation to the breaking and preservation of phase gauge symmetry in solids. In the present formalism, the propagation of one-directional time arises from the pre-defined and equivalent convergence of independent quantum fields towards the Boltzmann equilibrium, and it is shown that Glauber coherent states are related to the definition of the quantized field. Coherently coupling condensate and non-condensate parts as a direct consequence of the increasing quantum coherence time between the different quantum field components in the Bose gas from cooling to below the critical temperature, the present model describes symmetry breaking, which is originally known from the definition of a specific gauge field from Elitzur’s theorem for local gauge fields, as a global physical rather than a purely formal mathematical process.
Causal AI for Smart Decision-Making: Driving Sustainability in Urban Mobility and Industry (2025)
Fekete, Tamas
The transition toward sustainable urban mobility and industrial efficiency requires decision-making tools that go beyond correlation-based analysis to uncover true cause-and-effect relationships. Traditional machine learning models, while effective for prediction, often act as "black boxes," lacking interpretability and failing to reveal the mechanisms underlying complex systems. To address these limitations, this dissertation introduces a modular Causal AI framework for smart decision-making, integrating causal discovery and inference with structured domain knowledge to enhance sustainability outcomes. The framework is validated across three key domains: (1) urban CO2 emissions, (2) shared mobility demand, and (3) SME energy use. The first case study analyzes over 500,000 vehicles to uncover how engine performance and maintenance drive urban emissions. The second study examines shared bike systems, identifying causal impacts of weather patterns, station topology, and temporal demand fluctuations, supporting more adaptive fleet operations. The third applies the framework in a manufacturing SME, identifying the root causes of energy inefficiency and enabling targeted interventions to improve operational performance without compromising productivity. This research advances the interpretability and actionability of AI in sustainability contexts by replacing opaque predictive models with transparent, evidence-based causal reasoning. Algorithms such as PC, FCI, GES, and DirectLiNGAM are employed alongside domain ontologies to uncover valid causal relationships and support decision-making. A hybrid approach also addresses feature selection, dimensionality reduction, and model explainability, making the methodology broadly applicable across diverse sustainability challenges. While the framework demonstrates strong applicability, future work may focus on enhancing real-time scalability, adaptive ontology integration, and broader validation across domains such as electric mobility and smart energy systems. Overall, this thesis contributes a generalizable, interpretable Causal AI framework that enhances systemic understanding and supports sustainable transformation in policy, planning, and industrial decision-making.
Unveiling Retail Dynamics: "Mining Predictive Insights and Customer Segmentation from Online Retail Data" (2025)
Ansari, Mustafa ; Schelle, Alexej
As e-commerce continues to grow at a rapid pace, the ability to comprehend, segment, and predict customer behavior has become the core of business success. The objective of this project report is to study customer segmentation and predictive modeling using data mining methods on real-life online retail datasets. Exploiting Recency-Frequency-Monetary (RFM), K-Means Clustering, and Predictive Modeling (Logistic Regression, RandomForest, XGBoost, Deep Learning), the investigation explores novel customer segments. It assesses model performance demanding high value from customers. Findings indicate useful implications for segment behavior with the Deep Learning model giving outstanding performance in this case (accuracy up to 87.4% and ROC AUC of 0.932). The RFM-KMeans segmentation approach exposes tactical marketing opportunities in different customer groups, such as Champions, At-Risk Customers, and Big Spenders. This paper proposes a pipeline for scalable and interpretable analyses that combine unsupervised/supervised learning methods to support targeted marketing, retention forecasting, and long-tail customer value maximization in digital retail environments.
An interoperable knowledge enabler for smart energy management systems in the sustainability paradigm using Web 3 technologies (2025)
Mofatteh, Mohammad Yaser
Energy management and sustainability have become critical global priorities in response to growing environmental concerns and the need to optimize resource consumption. As industries expand and technological advancements continue to shape modern societies, energy demands are rapidly rising. This leads to escalating levels of carbon emissions and resource depletion, negatively impacting the environment and the economy. The thesis proposes an innovative approach to addressing energy management and sustainability complexities. The research focuses on developing a framework for smart energy systems that can autonomously improve their performance through knowledge sharing and semantic interoperability. The core idea behind this thesis is to enable smart energy systems to self-develop their knowledge models through decentralized technologies, particularly blockchain while ensuring peer-to-peer semantic interaction and collaboration across different environments and supply chains. A key innovation of this thesis is the use of blockchain technology as the underlying platform for achieving semantic interoperability and knowledge exchange among smart systems. By leveraging blockchain’s decentralized nature, a peer-to-peer semantic interaction framework is established. The research introduces a smart contract mechanism and a token-based economic model to incentivize stakeholders within the blockchain network, ensuring that participants align with the sustainability goals of the network. The thesis presents a novel approach to storing and exchanging knowledge models on the blockchain using the InterPlanetary File System (IPFS). This enables real-time updates to smart systems' knowledge models, allowing them to adapt and respond dynamically to changing environmental conditions and data inputs. Through the proposed blockchain ecosystem, the research provides a comprehensive solution for enhancing the interoperability, autonomy, and sustainability of smart energy systems.
Towards Consistent Subgrid Momentum Closures (2025)
Bagaeva, Ekaterina
This thesis addresses the challenge of accurately representing oceanic dynamics characterized by a multitude of interacting processes in numerical models. Specifically, it focuses on the simulation of oceanic circular patterns ranging from 10 to 100 km in diameter, known as mesoscale eddies. These eddies play a critical role in transporting energy, water properties, and nutrients across the ocean. This research uses grid resolutions that directly capture some larger mesoscale eddies (resolved) while employing advanced mathematical techniques to represent the effects of smaller, unresolved eddies. The primary aim of the thesis is to develop and incorporate novel mathematical and numerical approaches into the Finite Volume Sea Ice-Ocean Model (FESOM2) to improve the representation of mesoscale eddies while maintaining manageable computational costs. To bridge the gap between low-resolution and high-resolution simulations, the study enhances the mesoscale eddy modeling framework formulated by Juricke et al. (2019) through the implementation of new components that address unresolved dynamics. This includes the addition of an advection-based component to capture nonlinear interactions between resolved and unresolved eddies, which demonstrates positive performance. Furthermore, stochastic elements are introduced into the governing equations to better represent small-scale variability missing from deterministic formulations. In parallel, the thesis explores alternative and complementary parameterization strategies, offering fresh perspectives on modeling at partially resolved scales. Each enhancement is rigorously evaluated using a suite of diagnostic tools — many developed as part of this work — with a particular focus on spectral analysis and energy pathways. Overall, the thesis proposes an integrated approach to mesoscale eddy modeling, advancing the accuracy and consistency of ocean simulations across eddy-permitting resolutions.
Uncovering Pricing and Behavioural Patterns in Online Apparel: A Data Mining and Machine Learning Approach Using Clickstream Data (2025)
Acharya, Mitali Nileshbhai ; Schelle, Alexej
This project investigates customer behavior and pricing dynamics in the context of online apparel sales, using a real-world clickstream from a European e-commerce platform. Through a structured process of exploratory data analysis and predictive modeling, the study explores how product visuals, attributes, and browsing behavior influence both purchasing patterns and pricing outcomes. Random Forest models were used for both regression and classification tasks to predict product prices and classify items into budget or premium tiers. These model outputs were then combined to detect potential pricing–perception mismatches, where a product appears over- or underpriced relative to how it is perceived based on its features. This approach helps highlight products that may benefit from a review of their pricing or presentation strategy. Key insights from the analysis show that products with frontal model photography tend to perform better in both pricing and sales, while black and blue items generate the highest revenue. These findings lead to clear business recommendations in areas such as pricing, visual merchandising, and product positioning. The project demonstrates how machine learning can be applied not only to forecast outcomes but also to guide practical, data-driven decisions in e-commerce.
Advancing Environmental, Social, and Governance (ESG) Assessment and Reporting: A Hybrid Framework of Semantic Modeling, Multi-Criteria Analysis, and Maturity Models (2025)
VIJAYA, ANNAS
Environmental, Social, and Governance (ESG) reporting is increasingly critical for corporate transparency and accountability as demands from investors, regulators, and the public grow. Despite its importance, ESG reporting faces persistent challenges, including fragmented standards, inconsistent metrics, misalignment with global goals like the UN SDGs, and limited relevance for stakeholders. These issues weaken benchmarking, data reliability, and decision-making, raising the risk of greenwashing. Although previous studies have explored drivers of ESG performance, there is still a clear need for technical solutions that enhance the quality and usefulness of ESG disclosures through integrated approaches. This dissertation addresses these critical gaps by developing and proposing a novel, integrated framework that leverages the strength of semantic technologies, MCDM methods, and ESG maturity models. The research is structured through several interconnected studies, exploring specific industry applications using multi-criteria analysis techniques to identify and prioritize relevant ESG KPIs. A systematic literature review (SLR) provides a foundational understanding of existing ontology-driven solutions and their limitations in addressing reporting challenges and integrating quantitative methods. Based on these insights, the core contribution is the design of an ontology-based framework called ESGOnt. This framework utilizes a modular ESG ontology to standardize terminology, integrate fragmented data sources, and explicitly map ESG metrics to SDG targets. This research contributes by addressing critical challenges in ESG reporting through a novel, integrated framework. It advances the understanding of how semantic models can be combined with quantitative methods to create robust, transparent, and actionable sustainability reporting systems, strengthening corporate accountability and supporting more effective contributions to global sustainable development.
Sentiment Analysis of Tesla Tweets: Leveraging XGBoost for Social Media Insights (2025)
Lu, Zerong ; Schelle, Alexej
This study conducts an extensive sentiment analysis of 7,357 English Tesla-related tweets using an XGBoost classifier, addressing the critical need to understand public perception of innovative companies in the electric vehicle (EV) sector (Jain et al., 2019). The methodology involves advanced preprocessing with tweet-preprocessor and NLTK, feature engineering using TF-IDF (2,000 features) and weighted VADER sentiment scores, and model optimization via GridSearchCV with SMOTE balancing (Chawla et al., 2002). The model achieved an accuracy of 71.67% and a macro F1-score of 67.73% ± 5.97%, with a sentiment distribution of 37.31% negative, 30.58% neutral, and 32.11% positive. Theoretical assumptions explore the impact of social media on EV sentiment (Thelwall et al., 2010), while results and discussions highlight model performance and Tesla-specific insights (Chen & Guestrin, 2016). The study concludes with implications for EV marketing and future research directions in NLP.
The Structure and Dynamics of Groups in Open Source Software Development: A Computational Social Science Approach to Understanding Online Collaboration (2025)
Zöller, Nikolas
This dissertation examines Free/Libre Open Source Software (FLOSS) development groups through three interconnected studies, each applying computational social science methods to understand different aspects of online collaboration. The first study analyzes group interactions via pull requests, identifying five organizational structures ranging from hierarchical to collaboratively governed networks. This typology moves beyond the traditional "bazaar-cathedral" dichotomy and reveals how group structure impacts outcomes such as popularity, stability, and productivity. The second study employs an agent-based model informed by Affect Control Theory to explore how cultural dynamics shape roles, status, power distribution, and gender biases within FLOSS communities. Findings illustrate the interplay between cultural norms and social structures, highlighting pathways toward gender equality through cultural norm shifts. The third study investigates macro-level project dynamics, examining how repository fitness, preferential attachment, and aging influence project popularity. It compares the meritocratic nature of scientific research and FLOSS development, employing generative probabilistic models based on stochastic processes to understand the mechanisms driving popularity. Together, these studies demonstrate how platform design, cultural norms, and social structures collectively shape FLOSS projects, advancing our understanding of digital collaborative systems.
Straddling the border between tests and proofs (2025)
Huang, Li
Tests and proofs are two main techniques in modern software verification. To test a program means running the program to check if its execution yields an expected outcome. To prove a program is to build a mathematical proof, showing the correctness of the program against its desired properties. In the traditional view, however, tests and proofs are considered as two incompatible techniques. They are often treated as warring siblings and mostly applied in isolation. The complementarity of tests and proofs — though not immediately apparent — has been relatively underexplored. Can their combination mitigate each other’s weaknesses while harnessing their respective strengths? This thesis tries to straddle the border between tests and proofs and suggest a concrete answer. It explores how the two approaches can collaborate with and mutually benefit one another. Three key contributions arise from this exploration. The first contribution is Proof2Test, a framework that transforms failed proofs into useful test cases, allowing programmers to use tests to debug failed proofs effectively. The second contribution consists of several proof-based test generation strategies, which use proofs to enhance both the efficiency and effectiveness of test generation. This thesis also extends SC with “loop unrolling”, considering not just zero or one but any number of iterations, up to a set limit. It also includes an empirical study to examine how much (if anything) testing strategies miss when they limit themselves to standard branch coverage and, conversely, how many more bugs we can find if we unroll loops. The last contribution of this thesis is an automatic program repair approach, Proof2Fix, which takes advantages of the proposed test generation methods to produce meaningful corrections to faults revealed by proofs.
Neurocognitive and psychological dimensions associated with gait and balance in older adults (2025)
Imani, Hadis
This Ph.D. dissertation investigates the neurobehavioral, psychological, and cognitive factors influencing postural control and its age-related changes through four studies. Postural control is essential for daily activities, and its decline with age increases fall risk, leading to autonomy loss and reduced quality of life. The first study (Imani & Godde, 2021) explores how self-efficacy mediates the relationship between falls and autonomy in older adults. While falls negatively impact autonomy, higher self-efficacy reduces this effect. Cognitive function predicts autonomy but does not moderate the relationship between falls and autonomy. The second study examines the bidirectional link between cognitive and physical function. Results show that cognitive decline affects physical abilities over time and vice versa, highlighting the strong connection between executive function and motor control. This reinforces how cognitive decline, falls, and depressive mood contribute to reduced social participation. The third study investigates the effects of transcranial direct current stimulation (tDCS) combined with balance training in younger adults. Targeting the sensorimotor cortex and dorsolateral prefrontal cortex (DLPFC), the study assesses how anodal tDCS enhances balance. Resting-state EEG is also explored as a predictor of training effects. The fourth study extends this research to older adults, revealing age-related differences in neural activation during balance training. Results suggest individualized stimulation protocols may improve balance outcomes. Overall, these studies emphasize the cognitive-motor link in postural control and propose targeted interventions to enhance balance and autonomy, particularly in older adults at risk of falls.
The Decision to Start a Business: Determinants of Business Formation and Differences between Entrepreneurs and Employees (2025)
Jamitzky, Benedikt
Entrepreneurship is vital in driving innovation, economic growth, and societal transformation. Due to its growing relevance, this dissertation examines the factors that motivate individuals to engage in entrepreneurial endeavors, grounded in the Theory of Planned Behavior (TPB) and enriched by supplementary theoretical perspectives. The research combines qualitative and quantitative methods to explore how attitudes, subjective norms, and perceived behavioral control interact with these diverse aspects. The first study identifies key influences on entrepreneurial intention through qualitative interviews with entrepreneurs, thereby revealing ten critical determinants. The second study expands upon these findings by employing a quantitative approach to validate these parameters through a survey among entrepreneurs in Germany. It demonstrates the central importance of economics-oriented education, materialistic values, and resilience while refining the theoretical assumptions of the TPB in entrepreneurial contexts. Lastly, the third study extends the analysis by comparing the personality traits of entrepreneurs and employees utilizing the OCEAN model. This research delineates substantial differences across all five traits, underscoring the psychological dimensions of entrepreneurial behavior. By amalgamating the three studies and their respective findings, this dissertation contributes to the theoretical understanding of entrepreneurship by enhancing the predictive validity of the TPB for research on entrepreneurship and highlighting differences in personality traits among entrepreneurs and employees. Through the integration of qualitative insights and quantitative validation, this dissertation provides a comprehensive and nuanced perspective on the complex nature of entrepreneurship.
Applying co-creation to develop behaviour change interventions: Analysing the design, build and evaluation of digital health interventions (2025)
Anand Kumar, Vinayak
Chronic and non-communicable diseases present ongoing challenges for healthcare systems worldwide. Digital Health Interventions (DHIs) provide a promising solution by empowering patients to engage in health-related decisions and manage their behaviours. At present, many DHIs suffer from low user adoption or fail to progress beyond research. This thesis analyses the design, build, and evaluation of such tools to guide the effective co-creation of DHIs. Across five studies, this thesis examines the design, build, and evaluation of DHIs. The first two studies explore how to effectively plan the co-creation of DHIs, identifying both facilitators and challenges. The second study applies co-creation methods to incorporate end users in developing design specifications for a DHI. The third study evaluates the impact of including end users in the build phase, whilst the final two studies assess evaluation strategies, demonstrating how synthetic data and machine learning can be used to manage missing data and predict intervention outcomes. Findings highlight the importance of adaptive, inclusive design processes, careful planning of co-creator involvement, and the application of behavioural science across all phases. The thesis offers practical guidance for future researchers, emphasising the value of empowering patients, addressing attrition, and applying predictive analytics to maximise the real-world impact of DHIs.
The Relevance of Due Diligence, Hard and Soft Information in Financing Small Firms in Ghana (2025)
Umuerri, Oghenekome
Small business lending is significantly influenced by the interplay between the information institution types, the information models, and the due diligence process undertaken by financial institutions. While previous research has examined the impact of hard and soft information on credit availability, limited attention has been given to how different combinations of these information types and various financial institution types influence the quality of loan applications and the loan application success rates. Additionally, the role of due diligence in assessing small business loan applications and the specific signals lenders rely on for decision-making remain underexplored. This study integrates insights from three research streams to provide a unique analysis of small business lending dynamics. First, based on primary data collected from 242 small firms in Ghana and considering different financial institutions, including non-banks, we examine the effect of three distinct combinations of hard and soft information on loan application success rates. Our findings challenge conventional wisdom, indicating that an increased emphasis on soft information does not necessarily enhance transparency or improve loan application success rates. Moreover, while small-sized banks positively influence credit availability, this effect does not extend to small-sized non-banks. Second, leveraging signal theory, we analyze the due diligence process undertaken by financial institutions through qualitative insights from 24 loan officer interviews. We identify 11 key hard and soft signals that influence credit risk assessments, including key person risk, change in leadership risk, articulation of company value, adaptation to change, data accuracy, and completeness. These insights highlight the multifaceted nature of credit decision-making.
Bridging the Gap: A Semantic Approach to Industry 4.0 Maturity Models for Enhanced Adoption of Industry 4.0 (2025)
Angreani, Linda Salma
The existing Industry 4.0 maturity models (I4.0 MM) have mostly been built and tested in developed nations, making them less effective in developing countries with unique issues. Additionally, flexible updated models are needed to support the smooth integration of I4.0 adoption in rapid technological advancements and organizational matters. The research addresses the challenges by developing an adaptable I4.0 MM using approaches starting with structured literature reviews (SLRs), investigating the causal relationship and prioritization of I4.0 MMs key driving factors, aligning it with reputable reference architecture model (RAMs), and developing an ontology, named Ontomat 4.0, to facilitate interoperability of I4.0 MMs. The research's general findings highlight the core gaps in existing I4.0 MMs, the need to prioritize and the interdependence of the key driving factor in I4.0 transformation, the importance of strategically enhancing I4.0 adoption by aligning the key factor of I4.0 MMs with RAMs, and the necessity of a framework with an approach that can bridge the theoretical foundation of I4.0 MMs with practical application. The research concludes by describing contributions to the issues and challenges in the findings. However, while the research acknowledges the significant progress in its accomplishment, there are limitations to the study that need to be addressed in future research directions, including integrating sustainability metrics and increasingly essential factors, such as Customers, the potential integration of artificial intelligence (AI) within Ontomat 4.0, future exploration equipped with longitudinal studies, and the expansion of Ontomat 4.0 into a collaborative ecosystem where knowledge sharing and best practices can grow.
Advanced Beamforming Techniques for Enhanced Flexibility, Accessibility, and Multi-functionality in Wireless Communications Systems (2025)
Ando, Kengo
This dissertation contributes to three distinct focuses of BF design as: BF for flexible connectivity, BF for enhanced connectivity, and BF for over-the-air-computating (AirComp). The first objective is the “BF for flexible connectivity”. In order to realize flexibility for preserving connectivity regardless of the user position in the coverage area, the recent cell-free MIMO (CF-MIMO) system is considered. For the BF design, a flexible design is proposed, which is directly adaptable not only for both uplink (UL) and downlink (DL) communication modes but also for both under-loaded and over-loaded scenarios. As for the second focus, termed “BF for enhanced connectivity,” a novel BF design compatible with three distinct power allocation schemes is proposed. For the sake of connectivity enhancement, a DL MIMO-rate splitting multiple access (RSMA) system is considered. Even though the proposed BF design is assumed to be used only for under-loaded or fully-loaded scenarios, the computational complexity required to design BF is significantly less than that of the state-of-the-art (SotA) alternative. Finally, the ”BF for Over the Air Computing” is considered for envisioning the realization of integrated AI and communication. In this focus, novel receiver (RX) BF designs compatible with uniform-forcing (UF) precoding for a multi-user UL multiple-input single-output (MISO)-AirComp system are considered for higher performance or lower complexity. Toward higher performance design, while the proposed design sacrifices computational complexity in the BF, the resulting AirComp has a lower mean square error(MSE) performance. On the other hand, the proposed BF design for lower complexity realizes equivalent MSE performance achieved by the high-performance BF design with significantly lower complexity thanks to the combination of recent convex optimization and Bayesian optimization (BO) methods.
Modelling plankton dynamics and community compositions in temperate lakes (2025)
To, Sze Wing
In recent years, lakes have faced rising pressure from anthropogenic activities and climate warming, and the aquatic communities of some lake ecosystems are reshaping in ways that can form harmful algal blooms. It is crucial to understand how lake phytoplankton communities respond to environmental stressors under varying environmental conditions. The cell size of phytoplankton has multiple important implications for the dynamics, diversity, and productivity of a phytoplankton community. Empirical investigations in lakes showed that the size composition of phytoplankton communities differs with inorganic nutrient conditions, grazing pressure (usually quantified by zooplankton abundance), and water temperature. However, it is not clear how these three factors interact to shape the size composition of lake phytoplankton. In this thesis, I use size-based plankton modelling to elucidate how a trade-off mechanism, dependent on inorganic nutrient availabilities and zooplankton size-specific grazing strategies, shapes the dynamics, the size composition, and the exclusion pattern of phytoplankton in a generic temperate lake. Lastly, I recast the model to a specific Swiss lake, Greifensee, by using high-frequency data comprising phytoplankton cell size (biovolume) and plankton abundances. In summary, this thesis investigates the interactive effects of inorganic nutrient regimes and zooplankton grazing strategies on the community dynamics and compositions of lake phytoplankton and offers a glimpse into the future size compositions of phytoplankton and nutrient and plankton dynamics of Greifensee. The results not only advance our understanding of plankton communities in temperate lakes, but they also identify hypotheses related to zooplankton grazing strategies that can be further tested experimentally. The data-driven modelling approach presented here can contribute to strategic conservation and management plans for mitigating the effects of ongoing environmental change.
Characterization of geological settings related to intrusive magmatism on the Moon and Mars (2025)
Suárez Valencia, Javier Eduardo
In this research, I explored the geology of igneous intrusive domes in the Moon and Mars. These structures have not been widely investigated outside Earth, mainly due to the difficulty in locating them. I decided to do a detailed analysis of two systems: the Valentine Domes on the Moon, and the Utopia Planitia Dome field on Mars, focusing on their properties at the surface. I followed a cartographic approach in this research, using geostratigraphic units to characterize the locations and define their geological evolution. While analyzing the Valentine Domes, I noticed the lack of an open-source tool to work with the spectral data of the Moon, this led to the creation of the MoonIndex library, a tool to process spectral cubes and generate spectral indexes for the Moon. With the aid of MoonIndex, I performed the geological analysis of the Valentine Domes. The first result was the discovery of a new dome, which was detected by using the aspect parameter. I also found that several smaller structures such as rilles, dykes, and secondary domes are associated with the main domes. The dome field in Utopia Planitia is different from the lunar location, hundreds of domes were emplaced in a large area. The study of the domes showed they originated from an intrusive-to-extrusive system, since their shapes range from cryptodomes to volcanic domes. The lunar and Martian domes show some similarities, they are basaltic, have a small incidence in the surface morphology, and their parental magmas took advantage of structural features to reach the surface. However, the genesis of the system is different. The Valentine Domes formed under a polygenetic style, while the dome field in Utopia Planitia originated in a monogenetic system. This research will open the door to discovering new intrusive systems and to better understand the ones already known.
Production of an aspartyl proteinase from Mucor racemosus via solid-state fermentation. Applications in cheese manufacturing. (2025)
Qasim, Farhat
In recent years, solid-state fermentation [SFF] has gained the interest of the research community by showing remarkable developments in bioprocesses. It has emerged as a technology with the potential for producing microbial products such as pharmaceuticals, industrial enzymes, secondary metabolites, feed & food, and biofuels. Mucor racemosus CBS 381 was grown on optimized solid media (wheat bran) using the software, Design of Experiment (DoE). Based on laboratory-scale experiments the the SSF was scaled up by establishing a precisely controlled environment by utilizing Terrafors-IS Infors HT in-situ sterilizable rotating solid-state bioreactor. SSFs were introduced to predict the effect of shear forces caused by drum rotation on the overall biomass and enzyme production. Additionally, the aeration requirement and sensitivity of fungal growth and its effect on the final product were also investigated in combination with various moisture levels. Fermentations were performed with high and low moisture content i.e. 90% and 60% in combination with the flow rate of 1 and 2 L/min. Crude extract analysis via scale-up SSF with 60% moisture content and the airflow provided 1 L/min, exhibited ~570 U/mL milk-clotting activity with ~1600g biomass. However, the 2 L/min flow with 60% moisture content resulted in less biomass with reduced milk clotting activity. 90% moisture content with a 1 L /min Flow rate has resulted in enhanced biomass production i.e. ~1800 g and enzyme with the milk-clothing i.e. 558 U/mL. This study revealed that low moisture and low aeration levels lead to an increase in enzyme activity. Enzyme purification was accomplished via ion exchange chromatography using a DEAE Sepharose Fast Flow column. A threefold increase in the enzyme activity of the crude extract was observed. By using the enzyme, fresh cheese was manufactured on a pilot scale utilizing pasteurized cow milk. Various properties of the cheese were analysed.
Pectinolytic waste valorization – Fermentation of D-galacturonic acid by Saccharomyces cerevisiae using glycerol as a co-substrate (2025)
Perpelea, Andreea
Utilizing agro-industrial waste as a raw material for the production of chemicals, fuels and materials could support a circular bioeconomy, helping to minimize carbon and energy loss. Pectin-rich biomass is a generally under-utilized feedstock, and includes residues such as citrus peel, apple pomace and sugar beet pulp. It offers itself as a feedstock for biotechnological production processes using microorganisms as a cell factory. Unlike other biomass residues, this waste is advantageous due to its high sugar and low lignin content. One key component of pectin is D-galacturonic acid (D-GalUA), an oxidized substrate that S. cerevisiae cannot metabolize naturally. To enable its consumption, S. cerevisiae was equipped with the catabolic pathway naturally present in filamentous fungi. However, this did not allow D-GalUA to serve as sole carbon and energy source. The inability to grow on D-GalUA was thought to be due to a lack of electrons, as the pathway requires NAD(P)H. In this work, this problem was addressed by providing a co-substrate - glycerol - a by-product of the biodiesel industry. The electrons provided in this way were supposed to not only enable D-GalUA utilization but also support its fermentation to ethanol. Therefore, S. cerevisiae was equipped with both the fungal pathway for D-GalUA catabolism and the ‘DHA pathway’ for glycerol utilization – the latter channeling electrons from glycerol oxidation into cytosolic NADH. The resulting strain not only consumed D-GalUA at a high specific rate, but also co-fermented the substrates into ethanol, achieving a maximum yield of 71% of the theoretical maximum. Additionally, the native Gcy1, a non-specific aldo-keto reductase, was found to convert D-GalUA into L-galactonate, an intermediate of the D-GalUA catabolic pathway. By providing valuable insights into the co-utilization of glycerol and D-GalUA, this study lays the foundation for future endeavors towards the valorization of these two industrial by-products.
Towards Sustainable Fisheries Management: Understanding Territorial Use Rights in Fisheries (TURF) and Environmental Stewardship Actions (2025)
Furqan, Rifki
Local fishers have historically been subjected to the detrimental effects of overfishing, a consequence of open access practices that are likely to persist in the coming decades. The open-access nature of many fisheries is a significant driver of overfishing, which poses a substantial threat to marine ecosystems and their livelihoods that depend on them. The concept of common property theory provides a theoretical framework that can be used to explain the phenomenon of overfishing due to open access practices. Fishery resources are regarded as examples of a common property, implying that these resources belong to all fishers. This assumption gives rise to intense competition among fishers to exploit the fishery resources. One potential solution to this problem is to establish a territorial use rights system (TURF) that would prevent open-access practices. This thesis argues that all relevant stakeholders in small-scale fisheries management should prioritize environmental stewardship, regardless of the system used to address the overfishing problem caused by open-access practices, as this constitutes a principal factor in determining sustainability. This perspective is particularly relevant in the context of TURF implementation as numerous studies have demonstrated that TURF is an effective means of fostering stewardship. This thesis presents a collection of three studies that address the two primary topics of TURF and stewardship. While this thesis is primarily based on a case study of TURF implementation and stewardship actions (fishing logbook) in Kepulauan Seribu, Indonesia, I hope that the resulting publications will serve as additional references and contribute to the global discussion on TURF and stewardship.
Enabling Scalable High-Performance Integrated Sensing and Communications for Next-Generation Wireless Systems (2025)
Rou, Hyeon Seok
Wireless communications technology has gone through a significant evolution since its inception in the late 19th century, integrating itself as a critical pillar of modern society and the functions of the world. Successive generations of the mobile network systems since the first generation (1G) until the present have seen an ever-increasing demand of the key performance indicators (KPIs), such as data rate, reliability, spectral effciency, device connectivity, and more – outlined by the scope of the current fifth generation (5G) systems as enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine- type communications (mMTC), to support the emergent use cases such as autonomous and intelligent networks, extended reality (XR) applications, and Internet-of-Things (IoT), under the enabling technologies such as millimeter-wave (mmWave)/Terahertz (THz) bands, massive multiple-input multiple-output (mMIMO), cell-free MIMO (CF-MIMO), reconfigurable intelligent surface (RIS), and more. Furthermore, the imminent beyond fifth generation (B5G) and sixth-generation (6G) systems anticipate even higher requirements and ambitious paradigms in wireless technologies, aiming to improve upon the performance of 5G but also addressing other challenges which have assumed greater importance for the future, such as resource effciency (spectrum, energy, and hardware), physical layer security, system scalability, and high-mobility. In summary, this thesis entails a comprehensive investigation into the realisation of beyond fifth generation (B5G), underpinned by the two major topics of resource-effciency and low-complexity within the frameworks of the two selected enabling technologies, index modulation (IM) and integrated sensing and communications (ISAC), thereby proposing novel methods and analyses from unique yet complementary perspectives of the addressed problem of achieving scalable and high-performance next-generation wireless systems.
Numerical mixing across density surfaces in ocean modelling (2024)
Banerjee, Tridib
Several oceanic processes depend delicately on mixing of fluid parcels, particularly across density surfaces because of its extremely small magnitude. Even a fractional deviation in its representation can therefore cause large errors in various other ocean modelling aspects like circulation or tracer distribution. Moreover, since this mixing is also vital in maintaining the global energy balance, its accurate representation is highly desirable. This thesis thus deals with the issue of spurious mixing (artificial mixing of numerical or non-physical origin) across density surfaces in general circulation ocean models. It explores ways to properly identify it and also to potentially mitigate it. The thesis predominantly evolves around Finite volumE Sea Ice-Ocean Model (FESOM2). It develops a split-explicit external model solver together with an asynchronous time-stepping procedure that supports Arbitrary Largangian Eulerian (ALE) coordinates. It also implements a few such ALE coordinates known to reduce spurious mixing across density surfaces. The thesis then further develops a diagnostic technique that provides semi-local in space and time estimates for such spurious mixing on any grid without operator splitting. The work shows the novel solver to be less dissipative and scale better at any given workload without the need for additional temporal-filtering subcycles. It also shows the novel diagnostic technique to provide a local decomposition of various spurious mixing components. It reports levels of spurious mixing across density surfaces for different cases and how it can be much larger than the physical mixing. Finally, it provides discussion on the future possibilities and objectives.
Unveiling Small Microplastics from European Waters to the Arctic: Surface Water to Deep Sediment and Reflections on Data Representativeness (2024)
Wu, Fangzhu
Since the invention of the first synthetic polymer in 1907, plastics have revolutionized industries but have also caused significant environmental challenges. Over 170 trillion plastic particles are estimated to float in the world's oceans. Once in the marine environment, these plastics fragment into smaller particles (microplastics, MPs, <5 mm) under environmental forces, contaminating ecosystems worldwide, including the remote Arctic. This thesis investigates the Norwegian Coastal Current (NCC), a key transport route for MPs from northern Europe to the Arctic Ocean. Using novel sampling devices and advanced micro-Fourier transform infrared microscopy (μFTIR), small MPs (SMPs, 11–300 μm) were analyzed in seawater and sediments, providing the first detailed assessment of their spatial and temporal distribution in the NCC. The results reveal the prevalence of SMPs from surface seawater to deep sediments, including layers deposited before the advent of plastics. Key findings include a relatively homogeneous horizontal distribution of SMPs in surface and subsurface seawater and significant variability in sediment concentrations (54–12491 MP kg⁻¹) across cores. SMP accumulation trends in post-1950 sediment layers varied, challenging their reliability as markers of the Anthropocene. A total of 21 polymer types were identified, with smaller size classes dominating, highlighting their ecological significance. Further analysis of data representativeness revealed significant variability in MP concentrations and polymer diversity across stations, emphasizing the need for standardized protocols to ensure reliable data. Despite being based on a single research cruise, this study provides a valuable snapshot of SMP distribution in the NCC. The findings critically evaluate current MP research practices and highlight the need for robust methodologies to improve the reliability of future studies.
Analyzing deliberation and collective action problems in environmental governance: a case study of an aquaculture policy program (2024)
Paramita, Adiska Octa
Addressing environmental governance challenges necessitates collaboration among diverse societal actors to collectively develop and modify rules, norms, and social structures. A significant obstacle in environmental governance lies in the problems of institutional fit, where the existing governance arrangements may be mismatched with the specific social-ecological conditions at the local level. This misalignment poses a hurdle to effective and sustainable environmental management. Collective action’s theoretical lens is used in this study to navigate the varied interests, goals, and perspectives involved, aiming to comprehend the different factors influencing collaboration in the management of shared resources. Recognizing that collective action is inherently difficult, this dissertation focuses on the importance of deliberation to facilitate discussions on the risks, benefits, values, and capacities of different actors.
Machine Learning-Based Scheduling in Steel Manufacturing (2024)
Niyayesh, Mohammad
Steel manufacturing is characterized by its high energy consumption and the production of high-value-added products. In real-world steel production, unforeseen events frequently disrupt schedules, emphasizing the critical need for effective and adaptive planning to ensure continuous operations. This study makes significant contributions to the steel industry by offering new approaches to improve efficiency, streamline operations, and optimize production processes, ultimately driving advancements in steel manufacturing performance. To address the challenges inherent to EAF-based steelmaking, a seamless pipeline of algorithms has been developed. This pipeline works together to enhance the manufacturing planning process by providing an accurate chemical condensation of molten steel and classifying this outcome according to the most feasible steel grade, which can be obtained with a minimum of purification. Finally, the pipeline reschedules the planning process with the objective of maximizing machine utilization. To achieve these goals, the steelmaking stage key performance indicators (KPIs) that have the most impact on the quality of the final product were first identified. In the next step, a novel prediction algorithm utilizing a multilayer feedforward neural network was developed to estimate key quality parameters. Finally, to enhance the pipeline's resilience to disruptions, a Genetic Algorithm (GA) is employed to mitigate the impact of scenarios where processing times for jobs vary and do not align with the established schedule. This is a prevalent disruption event that renders the base schedule infeasible. The proposed algorithm aims to minimize total completion and waiting times, thereby enhancing operational efficiency and minimizing manufacturing costs.
Advancing quantitative methods for complex social-ecological system research: a case study of aquaculture (2024)
Nagel, Ben
Over the last few decades, environmental governance research has embraced a complex adaptive systems (CAS) framing: solving sustainability challenges requires an understanding of the social-ecological systems (SES) they are embedded in, consisting of interlinked components and relationships which form dynamic and emergent patterns. Many frameworks have been developed to help conceptually understand SES, however less focus has been given to advancing methods for SES research. I identify a particular need to advance quantitative SES methods, as despite a growing range of available approaches, much quantitative SES research heavily relies on classic statistical methods which by design ignore interactive effects and focus on reducing systems to individual variables. This creates tensions when applied to systems shaped by highly interactive and context-sensitive processes. Further, despite an emphasis on standardizability, quantitative research has not led to widespread synthesis of SES knowledge. There is a need to advance quantitative SES methods in ways which 1) incorporate complex system properties into case studies and 2) synthesize generalizable findings across cases without overly abstracting case complexity. In this thesis I explore these methodological challenges within the literature on Elinor Ostrom’s social-ecological systems framework (SESF). I then apply recent advances in methods for complexity through the case study of small-scale aquaculture governance in Indonesia: a participatory modeling method called fuzzy cognitive mapping to analyze “mental models” of aquaculture complexity, and archetypes analysis to synthesize generalizable patterns in complexity across a large set of heterogeneous aquaculture cases. I conclude that advancing SES methods to inform sustainable outcomes requires more critical engagement with “complex systems thinking” in not only conceptualizing environmental governance problems but also in empirical research design.
Microbial physiology of nitric oxide-transforming microorganisms (2024)
Garrido Amador, Paloma
Nitric oxide (NO) is a small gaseous molecule with important functions in cell biology and atmospheric chemistry owed to its unique physical and chemical properties. Since its relevance in biology was established, research on NO has focused primarily on its roles as signaling molecule, cytotoxin, and metabolic intermediate. Indeed, as a free radical and highly reactive compound, NO is as a potent toxin that can inhibit microbial growth, however it also has a central position in the microbial nitrogen cycle as a key intermediate in processes such as denitrification, aerobic ammonia oxidation, anaerobic ammonium oxidation, and nitrite-dependent anaerobic methane oxidation. Additionally, NO is a very energy-rich molecule with a high redox potential (NO/N2O; E0’ = +1.175 V) and it may have played a key role in the evolution of life on early Earth and the bioenergetic pathways related to modern denitrification and aerobic respiration. During recent years, we have been presented with new roles of NO in the nitrogen cycle. It appears as if the focus of NO research has slowly started to change its course as we begin to recognize its potential as direct substrate for microbial growth. Given its important roles in past and present microbial life, we believe that there must be a plethora of microorganisms that are capable of growing on NO conversions. Therefore, the main goal of my PhD project was to challenge our understanding of NO as mere toxin and intermediate, and investigate its potential as direct energy source for microbial life, whether it is through known or novel biochemical reactions, and the microorganisms that use it for this purpose, using a combination of continuous and batch incubations, physiological experiments, and multi-OMIC analyses.
Computational Insights into Light Harvesting in Photosystem II Antenna Complexes (2024)
Sarngadharan, Pooja
Photosynthesis is an essential process through which sunlight is converted into chemical energy, sustaining virtually all life on Earth. In the specific case of oxygenic photosynthesis, Photosystem II (PSII) plays a pivotal role as a major component of the photosynthetic machinery, responsible for the initial light absorption and generating molecular oxygen. This process involves numerous protein-pigment complexes within PSII. The photosynthetic apparatus is rich in colored pigments, which not only make it visually appealing but also crucial for capturing and transporting sunlight through excitation energy transfer. Due to the large size of these proteins and the electronic complexity of the pigment molecules embedded in the membrane, multiscale quantum-classical methods are essential for studying the processes. The protein environment significantly influences the tuning of the excitation energy of the pigments, thereby establishing an energy funnel in such systems. This thesis aims to deepen our understanding of the lightharvesting process in the antenna complexes of PSII. To achieve this, a multiscale approach is employed. This involves using the density functional tight-binding (DFTB) method to perform ground state molecular dynamics within a quantum mechanics/molecular mechanics (QM/MM) framework, coupled to an electrostatic classical environment. Following this, the time-dependent extension of the long-range-corrected DFTB is applied to obtain the excitation energies of each pigment molecule, within a QM/MM setting. This method generates essential excitonic parameters such as site energies, couplings, and spectral densities, which are utilized to model the spectroscopic properties. Furthermore, the calculated results have been compared with experimental data, showing great agreement for the antenna complexes in PSII. This alignment ensures the robustness of the methods, validating their use for studying light harvesting in both plant and cyanobacterial systems.
A Framework for Enabling Synergic Interactions Between Omnichannel and Product Lifecycle Management Platform Inspired by System Dynamics Approach (2024)
Mohammadian, Noushin
The rapid rise of new technologies, such as mobile phones, social networks, and increased internet access, has created new opportunities for retailers to expand through omnichannel strategies, which aim to provide a seamless customer experience across different channels. While omnichannel can offer benefits and competitive advantages, it faces challenges like price inconsistencies and poor information sharing. Despite its growing recognition, its integration with Product Lifecycle Management (PLM) is underexplored. This thesis investigates the overlap and mutual effects of omnichannel and PLM, particularly emphasizing the importance of data and knowledge sharing between them. As research into data analytics in omnichannel evolves, tracking and tracing mechanisms in PLM become increasingly critical. The main objective of this study is to develop a bi-directional framework connecting omnichannel and PLM using a System Dynamics approach. This framework aims to incorporate omnichannel mechanisms into PLM and provide cause-and-effect analysis to better understand the operational role of omnichannel within PLM. Additionally, the research introduces an approach to integrate Business-to-Business (B2B) aspects from PLM with Business-to-Customer (B2C) elements through omnichannel strategies. Leveraging omnichannel's influence on touchpoints like influencers and social media, this approach helps companies align consumer behavior with strategic goals, boosting competitiveness. Ultimately, this thesis aims to bridge the gap between omnichannel and PLM, driving a shift in consumer behavior and strengthening the integration of B2B and B2C in retail.
An Investigation of Nearly Geostrophic Flows in Bounded Domains (2024)
Afzal, Khadeeja
This thesis investigates the use and behavior of balance relations for studying the nearly-geostrophic flow in a bounded domain. The goal is to derive simple, fully nonlinear models for the large scale flow in the vicinity of basin boundaries and investigate their asymptotic behavior. This will help improve our conceptual understanding and provide benchmarks for the calibration of larger numerical ocean models. The balance models are those in which the Coriolis force balances the pressure gradient force in the limit of small Rossby number. These models are derived using a Lagrangian-based variational approach. The idea was first proposed by Salmon (1983), in which the author derived the approximate model for nearly geostrophic flow for the rotating shallow water equations. He applied the approximations on the Lagrangian of the parent fluid model and then took variations to get the Euler-Lagrangian equations, which he named as L1 balance model. Oliver (2006) generalized this idea and started with the arbitrary change in coordinates to the canonical coordinates, and then consistently truncated the transformation and the Lagrangian to a desired order. This approach gives the one-parameter generalized family of large-scale models (GLSG), among which Salmon’s L1 model is observed to be numerically well-behaved, as noted by Dritschel et al. (2017). In the current study, we employ the approach detailed in Oliver (2006) and derived the variational L1 balance model for the shallow water equations with constant Coriolis force in the vicinity of the boundaries. At the boundary, zero-flux is assumed in the normal direction and the variational derivation of the model suggests the geostrophic balance up to O(ε) in the tangential direction. We numerically investigated how well the balance dynamics capture the shallow water equations under specified boundary conditions. For this, we initialized the full shallow water equations with the balanced state and allowed it to advect until time T. We then compared the fields using their root mean square (r.m.s.) differences and observed their asymptotic behaviour. Furthermore, Eulerian time scales are also determined at which both the models can be compared. Notably, we observed that the physical boundary interactions result in a slowdown of the time scales when compared to the time scales in the case of periodic boundaries.
Physiology and genomics of new marine methane-oxidizing bacteria (2024)
Kniaziuk, Margarita
Methane is the most abundant hydrocarbon on Earth, and plays a vital role in the global carbon cycle. In marine ecosystems, large quantities of produced methane are oxidized by methane-oxidizing microorganisms before it reaches the atmosphere. Aerobic methanotrophic bacteria, which consume methane in the upper oxic layers of marine sediments and the water column, represent the final oceanic methane filter. To date, the majority of marine aerobic methanotrophs remains uncultivated, with currently only nine formally described cultures. This hinders our understanding of their physiology that ultimately controls their activity and affects the dispersal of these methanotrophs in nature. In order to fill this gap in knowledge, the present work was focused on the isolation and characterization of marine methanotrophs from the North Sea and the Western Scheldt estuary sediments. The obtained methanotrophic cultures were investigated in physiological tests, and their metabolism was reconstructed based on high quality genomes. The isolation of four new methanotrophic species affiliated to the genera Methyloprofundus and Methylomarinum allowed to determine specific ecophysiological preferences and key conserved and distinct features within these genera. The isolate of Methylomarinum sarcina B3 exhibited a sarcina-like cell organization, which has not been previously reported for any marine methanotroph. The unusual Embden-Meyerhof-Parnas pathway identified in the new Methyloprofundus spp. could potentially serve as an alternative to the canonical glycolytic route. Finally, the discovery of a new putative nitrate reductase in Methyloprofundus spp. could have important implications for the understanding of the diversity of bacterial nitrate reductases and anaerobic respiration. Altogether, this work has advanced the characterization of the Methyloprofundus and Methylomarinum genera and laid the foundation for future research in microbial carbon and nitrogen metabolism.
The Complex Effects of Distorted Social Perceptions on Opinions about Climate Change (2024)
Steiglechner, Peter
Polarisation is a great concern in current social and political debates. A divergence of opinions or, more generally, a lack of societal agreement, for example on fundamental problems like climate change, presents a barrier to rapid action against a looming crisis. There are many theories on why people polarise on certain topics. However, the drivers of polarisation in social environments are multi-faceted and involve complex feedbacks among social, cognitive, and structural processes. While humans require interactions with each other to form shared views and cooperate effectively on many problems, social influence can produce a variety of opinion patterns, such as consensus, persistent disagreement, or polarisation. In this thesis, I develop mathematical models of opinion formation or perception to uncover the conditions underpinning the emergence of such patterns. I formalise how psychological factors distort the way individuals perceive others into a mathematical language and analyse how these perceptions affect the formation of consensus or the persistence of disagreement in a virtual society. The factors are: (1) noise, (2) bias, or (3) subjective perception. Taken together, the three studies demonstrate that these factors distorting people's perceptions or responses to social influence have a non-negligible and sometimes surprising impact on collective opinion patterns. This thesis highlights the importance to better understand the mechanisms behind social phenomena and their non-trivial consequences on opinion dynamics. While the models and the conclusions presented in the thesis may not be readily used to predict opinion patterns, owing to the complexity and inherent uncertainty of our society, they contribute to the social sciences by demonstrating counter-intuitive consequences of seemingly obvious theoretical assumptions, highlighting gaps and potentially critical ambiguities in social theories, and suggesting future directions for empirical analysis.
Monitoring Biological Processes Based on Supramolecular Host-Guest Interactions (2024)
Jiang, Ruixue
The thesis comprises three main sections, in which the central theme revolves around the supramolecular reporter pairs. The first and second sections aim to design intricate coupled reactions, namely supramolecular tandem enzyme membrane assays and supramolecular membrane enzyme assays, achieving the simulation of continuous physiological processes. In the supramolecular tandem enzyme membrane assays section, we describe the usage of two supramolecular reporter pairs, with one set located inside the vesicles and the other set positioned outside the vesicles, to mimic the simple process of digestion and absorption. The second section, the supramolecular tandem membrane enzyme assays, focuses on simulating the processes of cellular uptake and metabolism using a single set of reporter pair located within the vesicles. In the uptake process, the transport of substrates across the vesicle membrane is monitored by the internal reporter pair calix[4]arene•luciginin (CX4•LCG) or cucurbit[7]uril•berberine (CB7•BE). Similarly, the metabolic process is monitored by the same reporter pair within the vesicles, monitoring the enzymatic conversion of the substrates. The third section represents an intriguing exploration of the effects of variations in the vesicle surface microenvironment on the interactions between supramolecular hosts and guests. The aim is to gain a deeper understanding of the mechanisms underlying the regulation of cell signaling transduction, transmembrane transport, and sensing processes, which are governed by the dynamic and complex presence of proteins, saccharides, and other molecules on the cell surface.
Development of Phytoextract from Food Waste for Sustainable Aerosol Disinfection Technology (2024)
Ziemah, James
The rapid increase in food production waste, totalling 1.3 billion tons annually, significantly contributes to greenhouse gas emissions. Bioeconomy strategies are needed to utilize this waste and mitigate environmental impacts sustainably. Repurposing food waste as a source of phytoextracts rich in bioactive compounds can serve industries as sustainable food, hygiene, and pharmaceutical alternatives. This thesis explores the development of antimicrobial phytoextracts from food production waste—such as hot trub (HT), coffee silverskin (CSS), lemon peel (LP), and broad bean shell (BBS)—as alternatives to synthetic chemicals for aerosol hygiene disinfection. The phytoextracts, characterized using advanced analytical techniques (UHPLC-ESI-QTOF-MS, NMR, NanoDSF and FTIR), exhibited significant antibacterial activity against pathogens like Listeria monocytogenes and Staphylococcus aureus, primarily due to bioactive polyphenols. The phytoextracts were successfully converted into aerosol formulations and tested for efficacy in reducing bacterial contamination on surfaces and in the air, achieving up to 98% reduction in bacteria, yeast, and mould. These results align with commercial disinfectant standards, demonstrating the feasibility of using these extracts for disinfection. The study also employed green extraction methods, maintaining phytoextracts' chemical integrity and antibacterial activity. Additionally, the extracts showed promising antidiabetic and antioxidant Sum Parameters activities and were free of cytotoxic effects, further expanding their applications. Protein extracts from BBS were also analyzed, revealing valuable peptides that could be used in various industries. However, further optimization is necessary for commercialization, reducing aerosol particle size, and conducting safety tests. The study highlights the untapped potential of food waste streams as valuable sources of bioactive compounds with diverse applications across multiple industries.
A Moving Belt System for the Continuous Recovery of Bioproducts Utilizing Composite Fibrous Adsorbent (2024)
Guo, Yijia
A novel composite fabric-based adsorbent is presented, in the form of an elastic and robust woven fabric belt following the general designs observed in known horizontal flat belt conveyors. The adsorbent was a strong cation-exchanger functionalized by sulphopropyl (SP) made of nylon 6 reaching a static binding capacity equal to 107.3 mg/g. Moreover, excellent dynamic binding capacity (DBC) values (54.5 mg/g) was tested even when operated at high flow rates (480 cm/h). In a subsequent step, a continuous protein purification system based on the true moving bed concept, namely moving adsorption belt system, is presented. The composite adsorbent was embedded into a bench-scale prototype, permitting performance studies with a model protein (lysozyme). Results indicated that the moving belt system could recover lysozyme with a productivity up to 0.5 mg/cm2/h. Subsequently, a monoclonal antibody (Humira) was recovered from unclarified CHO_K1 cell line culture with high purity as judged by reducing SDS-PAGE, high purification factor (5.8), and in a single step confirming the suitability and selectivity of the purification procedure. A dynamic decision-support tool, was utilized to evaluate how the potential of the moving belt system various across a range of scale (50 to 5000 kg/year) from an economic perspective. The comparison of cost of goods per gram (COG/g) demonstrates that moving belt system cannot offer a better manufacturing cost comparing to protein A chromatography when the production scale was smaller than 5000 kg/year. At production scale of 5000 kg/year, both capture processes offer similar COG/g values. The most effective way to narrow the difference in COG/g is to increase the DBC of the moving belt process 4 times. Certain adoption barriers were observed during processing and the possible optimization approaches were introduced. Inherently, scale-up is relatively easy to be fulfilled if moving adsorption system is utilized for purification.
Continuous Downstream Bioprocessing of Proteins Employing Fluidised Bed Adsorption Technology (2024)
Herlevi, Lisa-Marie
In this work capacity constraints during downstream processing of biologics are addressed by development of novel platform for continuous and direct purification of target protein from unclarified feed (e.g. fermentation broth or cell culture). The work is focused on addressing hinderances observed in related work on truly continuous moving expanded or fluidized bed systems by establishing a novel platform referred as Fluidized Bed Riser Adsorption System (FBRAS) that is based on two distinct components: a) a co-current column where the feedstock and the adsorbent beads are contacted permitting simultaneous product capture and biomass removal. Within this section, the fluid velocity is considerably lower than the terminal settling velocity of the adsorbent particles, thus leading to increased residence time and increased contact time. b) A series of counter-current baffle-modified contactors/columns in series, allowing adsorbent washing, and efficient product elution and bead regeneration/re-equilibration due to restricted settling of adsorbent. The second part of this work is aimed to support the overall technology development with construction of novel resin materials suitable for continuous processing by exploiting double network (DN) strategy for co-polymerisation of agarose via hydrogen bonding induced by freeze-thaw (FT) method. The FBRAS was validated for continuous capture and concentration of lysozyme followed by implementation to an existing DSP routine for production of antifungal peptide in collaboration with Protera SAS.
LC-MS Based Profiling of Peptides and Proteins of Common Legumes in Sri Lanka and Evaluation of their Bioactive Potential (2024)
Alakolanga, Alakolange Gedara Achala Wimukthika
The popularity of plant-based proteins, especially legumes has experienced a remarkable surge in recent years, due to the heightened awareness health benefits, concerns on animal welfare, environmental sustainability, and advancements in food technology. Apart from their nutritional value, many of the encrypted peptide sequences have shown remarkable bioactivities. However, most of the legume crops consumed worldwide are not evaluated for protein profile and bioactive potential, except for soya beans, peas, and lentils. The lack of scientific evidence has become a major barrier in successful utilization of these legumes. Also, there are many chemical and physiological barriers which limit the protein digestion such as protease inhibitors and complex structural diversity. So, this study was planned to evaluate the amino acid profile, presence of bioactive peptide sequences and improving the digestibility of proteins from common legumes cultivated in Sri Lanka, including pigeon pea-Cajanus cajan, green gram- Vigna radiata, cowpea - Vigna unguiculata, black gram - Vigna mungo and horse gram- Macrotyloma uniflorum. Extraction with acid, alkaline, salt, alcohol and TRIS buffers were compared for the yield and the diversity of protein profile. Digested protein extracts with trypsin, chymotrypsin and pepsin were analysed by LC-ESI-MS. Peptide sequencing was performed with PEAKS software to identify proteins, post-translational modifications, and amino acid profile. The peptide fragments identified from trypsin, pepsin and chymotrypsin hydrolysates were screened with different in-silico approaches and in vitro bioassays. Also, the effect of domestic processing methods including soaking, gemination, boiling and roasting on the digestibility of green gram proteins was evaluated. Results showed that the alkaline extraction is effective in extracting an optimum protein yield with most diverse and balanced protein profile, comprising storage, enzyme, and other functional proteins. Most of the cultivars tested show similar storage protein profiles, but there were significant differences in functional proteins important in abiotic stress management. Also, seed storage proteins show extensive post-translational modifications, which serves as another level of protection and functionalities such as dormancy release and metabolic resumption. They also have balanced essential amino acid profile, except for Methionine (M) and tryptophane (W). All legumes exhibited significant potential in antioxidant and antibacterial properties, and trypsin mediated digestion is more successful in generating bioactive peptides. Boiling and roasting enhanced the digestibility of legume proteins, which can be attributed to the removal of protease inhibitors, unfolding of globular storage proteins and alterations in secondary structures into less ordered conformations.
Expanding the Scope of the k-Prototypes Algorithm - Addressing Issues in Cluster Analysis of Mixed-Type Data Arising from Real-World Applications (2024)
Aschenbruck, Rabea
Cluster analysis is a common part of data analysis. Its aim is the identification of unknown structure in data and the determination of a partition with groups of objects as similar as possible (so-called clusters). In contrast to the frequent occurrence of mixed-type data in real-world applications, involving numerical as well as categorical features, research tends to concentrate on data containing exclusively numerical features. There are comparatively few methods for clustering mixed-type data, with the k-prototypes algorithm being presumably the most widely recognized. The purpose of this cumulative dissertation is to expand the scope of this clustering algorithm. It addresses aspects that are not treated in Huang's original publication of the k-prototype algorithm, including the validation of the number of clusters, variable selection of data to be clustered, imputation of incomplete data, algorithm initialization, and the integration of an alternative distance measure in the algorithm routine. These issues are covered as they are prevalent in the application of the k-prototypes algorithm on real-world data. In these clustering tasks, the user lacks knowledge about the optimal number of clusters or the most useful variables to determine the cluster partition. In addition, incomplete data often occur and need to be dealt with. The algorithm’s initialization is analyzed to optimize the iterative routine, which was originally published with a random-based choice of initial prototypes. Additionally, the distance-based partitioning algorithm is extended to ordinal data for distance calculation with the change of the algorithm’s distance measure. To conduct the research, simulation studies on artificially generated data are utilized as well as exemplary analyzes on real-world data.
Multi-criteria flexibility allocation for electric distribution networks (2024)
Spiegel, Thomas
Germany’s national climate protection policy, the German Energy Transition, is oriented towards the reduction of energy-related greenhouse gas emissions by rapidly expanding the share of renewable energy systems. New challenges arise regarding technical and energy economical integration as installed wind and photovoltaic power capacities increase continuously. This thesis contributes to the topic by introducing a framework for online multi-criteria flexibility allocation in electrical distribution networks with transport capacity limitations. It considers technical aspects and market participant interests that may contradict each other. Local master data is preprocessed using geospatial information of buildings, photovoltaic systems, wind turbines, and the human population within a spatial domain of interest. By combining weather forecast data, this establishes the foundation for predicting power flow in the electrical distribution network and generating grid-beneficial criteria utilizing the smart grid traffic light concept. Furthermore, master data of the German wind and photovoltaic power plant portfolio is combined with weather forecast data to predict ationwide wind and photovoltaic power feed-in and to generate ecological- and market-beneficial criteria. In addition, metamodels are created and employed to forecast balancing group management data, i.e., EPEX SPOT Day-Ahead electricity prices in the bidding zone of Germany and Luxembourg, and imbalance energy demand of difference balancing groups. At last, non-scalarized schedule solutions are estimated to reach a multi-criteria flexibility allocation. The framework applicability is demonstrated by defined scenarios. Results show that publicly available data allows modelling, calibrating, and operating the introduced multi-criteria flexibility allocation framework in a real-world setting.
Development and Application of Compound Class-Specific Benchmark Data Sets for Differentiated Assessment of Docking and Scoring Algorithm Performance (2024)
Chachulski, Laura
This thesis focuses on the development and application of benchmark data sets for diverse compound classes and the differentiated assessment of docking and scoring algorithm performance using the curated sets. Various popular software, including AutoDock, AutoDock Vina, GOLD, MOE, FlexX and FITTED were assessed for two important types of compounds, which are summarized as follows. In publication I, we investigated the fragment placement performance of molecular docking software AutoDock, AutoDock Vina, GOLD and FlexX. For this assessment we constructed LEADS-FRAG, a benchmark data set containing 93 high-quality protein-fragment complexes. GOLD with ChemPLP and AutoDock Vina performed best and generated near-native conformations (root mean square deviation <1.5 Å) for more than 50% of the data set considering the top-ranked docking pose. Taking into account all docking poses, the tested programs generated near-native conformations for up to 86% of the fragments. By rescoring with the GOLD scoring functions and PLIff, the number of near-native conformations increased up to 40% with respect to the top-rescored poses, showing that conventional small-molecule docking programs achieve a satisfactory fragment docking performance. In manuscript 2, we examined covalently bound ligands and tested the efficiency of covalent docking options in the software programs AutoDock, GOLD, MOE and FITTED. We generated the LEADS-COV data set, containing 89 high-quality covalently bound protein-ligand complexes: 47 with a cysteine bound ligand and 42 with serine. For Cysteine GOLD with ChemPLP or ChemScore performed best and generated near-native conformations (root mean square deviation <1.5 Å) for more than 40% of the data set considering the top-ranked docking pose. Serine in comparison had better results, with over 65% top-ranked near native poses by GOLD with ChemPLP. Taking into account all generated poses values went up to over 65% for cysteine and over 80% for serine.
The Role of Drug Repurposing in Containment of Emerging Viral Disease Caused by SARS‐CoV‐2 (2024)
Kuzikov, Maria
This thesis focuses on the role of drug repurposing in containment of an emerging disease, taking SARSCoV‐2 as a case study. The severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) emerged in2019 causing a deadly respiratory disease: COVID‐19. The increasing knowledge about SARS‐CoV‐2allowed the expansion of multiple approaches to contain the spread of infection. Eventually the rapid development of anti‐SARS‐CoV‐2 vaccines allowed a control of the pandemic. Effective antiviral pharmacological treatments are still rare and viral evolution allowed a fast adaptation and escape from available containment methods. Since the beginning of the SARS‐CoV‐2 pandemic drug repurposing was considered as a valuable source for identification of new antivirals, due to the advantage of available clinical safety data and activity profiles. To interfere with SARS‐CoV‐2 infection and to identify new antiviral compounds, key steps of the virus replication cycle and their corresponding targets were selected for assay development. The screening approaches not only identified new molecules, that can act as starting points to develop new antiviral therapies, but also revealed critical steps and pitfalls in developing assays, that will help to optimize the translation of compound effects from biochemical to cell‐based state. The study also adresses the misconception that repurposed drug cannot interfere with assay, by showing examples of compound‐reactivity through generation of reactive oxygen species, and readout interference. In addition, a drug‐combination approach for entry‐inhibitors aiming at a synergistic response is shown as an option to overcome difficulties in reaching necessary intracellular target‐doses without increasing cytotoxicity. In conclusion, this research highlights the potential of drug repurposing in antiviral drug discovery. The generated results contribute to the publicly available data on drug repurposing against SARS‐CoV‐2, which may be used for research.
Transition of soluble membrane pore forming proteins from solution into the membrane: hsPEX5 and LaTXs. (2024)
Blum, Daniel Arno
Proteins are usually classified as water-soluble proteins or membrane proteins based on their cellular localization. In the course of their biogenesis, there is a significant number of initially water-soluble proteins and, after crossing into the membrane, develop their actual function as pore-forming or receptor proteins. Although the passage of the water-soluble proteins into the membrane and the associated refolding of the proteins are essential steps for the formation of the protein functions, only a few high-resolution methods exist to investigate these individual steps of the protein-membrane binding and the simultaneous development of the final active conformation in the membrane. In this study the transition of some proteins from the aqueous phase into the functional integral membrane form is examined for two cases, the human peroxisomal targeting signal 1 (PTS1) receptor hsPEX5 and the presynaptic pore-forming neu-rotoxins (LaTXs) found in the venom of Latrodectus spiders, namely α-LCT, δ-LIT and α-LTX. A vertical and horizontal artificial bilayer setup was used, enabling simultaneous and sequential high-resolution electrical and fluorescent measurements at the single-molecule level. It is presented that hsPEX5 alone harbors the ability to interact with the artificial mem-brane and generate a conductive membrane-pore. The electrophysiological results revealed for the LaTXs the essential role of calcium in stabilizing the oligomerized pore and moreover the significance of the latrotoxin-channels in cellular calcium homeostasis.
Modelling the atmosphere-ocean interface with improved energetic consistency (2024)
Streffing, Jan
Our unintentional large-scale geoengineering project, characterized by a rapid in- crease in greenhouse gas concentrations, poses significant challenges in predicting and mitigating global and regional consequences. Climate researchers worldwide are constructing and refining climate models to understand and navigate the complex Earth system state and evolution. This thesis focuses on my contributions to this endeavor, specifically the construction, evaluation, and application of the AWI-CM3 coupled climate model. Additionally, I address the importance of improving the energetic consistency across the critical interface between the atmosphere and ocean. This research was conducted as part of the DFG collaborative Research Center Transregio (TRR) 181 ”Energy Transfers in Atmosphere and Ocean”, which aims to develop mathematically rigorous tools for climate analysis and modelling. By focusing on the interactions between the atmosphere and ocean, I strive to enhance our under- standing of the exchange of heat, momentum, and mass, while incorporating model components for sea ice and river runoff. I review the selection and method of computation for physical interface fluxes, introduce of stochastic remapping to conserve information across the coupling interface, and adapt vertical ocean mixing parameterizations to enhance the realism of the AWI-CM3 model. Through these efforts, I aim to contribute to the development of a comprehensive Earth System Model and advance our understanding of climate change and its societal implications.
Improving pregnant women´s safe communication by applying health psychology and digital interventions: Evaluation of synchronous and asynchronous intervention approaches (2024)
Kötting, Lukas
Patient safety, as a topic that has been under constant development for several decades with the aim of increasing it, is associated with an understudied target behaviour: safe communication behaviour of pregnant women. Study one refers to N= 424 cross-sectional self-administered data. The evaluation was carried out via path modelling. In the second study (N=367), the effectiveness of two forms of intervention developed in the project for improving safe communication was tested using repeated measures analyses of covariance (ANCOVAs) for a before-and-after comparison, whereby the online live seminar and control group followed an RCT design. In the third study (N=1187), psychological predictors of safe communication as well as sociodemographic characteristics were identified using hierarchical regression. Risk factors associated with early drop out within the web app were identified using logistic regression. Results from Study 1 show that an adapted HAPA fitted the data best, whereby two sequential mediations emerged. Regarding Study 2 results indicate that women participating in the digital live seminar improved their safe communication behaviour and perceived patient more compared to women using the web app. Study 3 identified that younger women are at risk for early dropout in the web app. Action planning revealed as a core finding in predicting safe communication behaviour over the course of the web app. Psychological mechanisms and their social-cognitive determinants in the motivational phase of pregnant women's intention to communicate safely are mediated by coping-specific as well as planning-specific volitional determinants and could be identified and explained. Younger age is a risk factor for early discontinuation in the web-app. This thesis shows how digital applications could be built, developed and implemented from a psychological perspective in the future and is addressed to pregnant women, to health care providers and to researchers.
Application of Enhanced Sampling Approaches to the Translocation of Antibiotics through Porins (2024)
Acharya, Abhishek
Antibiotics enter the bacterial cells through the outer membrane diffusion channels called porins. The antibiotic permeation process through porins is of immediate interest and the understanding is expected to aid the development of antibacterial drugs with improved efficacy. The accurate estimation of free energy for translocation is a prerequisite for obtaining quantitative estimates from simulations which would enable a meaningful comparison of different antibiotic permeation mechanisms. This goal, however, has proved to be a significant challenge in the studies on bulky antibiotics, presumably due to a number of slow modes that govern the permeation process. Umbrella sampling and well-tempered metadynamics, that have been extensively used in the field, are limited in the number of degrees of freedom that can be simultaneously biased. In recent years, several methods have been developed that allow biasing simultaneously more degrees of freedom. The primary objective of the present thesis is to examine a few temperature acceleration-based sampling schemes for the enhanced exploration of antibiotic permeation pathways. Subsequently, the temperature accelerated sliced sampling method has been applied to the study of permeation pathways for a few antibiotics. The method, in combination with applied field simulations, is used to uncover the mechanistic aspects of L3 conformational dynamics in antibiotic permeation and voltage gating. The findings provide a strong rationale for the fast permeation of positive and zwitterionic antibiotics reported in experiments. Finally, the combination of a Brownian dynamics scheme with the temperature accelerated molecular dynamics method has been used for the fast and approximate estimation of antibiotic permeability constants.
Coordination in smart energy systems? Contracting and pricing (2024)
Palovic, Martin
This thesis studies energy system integration, that is mechanisms coordinating electricity sector with the broader energy system. More specifically, it utilizes microeconomic modeling and academic insights from industrial and institutional economics to develop coordination mechanisms capable of addressing flawed stakeholder coordination occurring within the electricity sector and at its interface to other energy sectors. This cumulative dissertation consists of five papers that together cover all three layers of energy system integration. Paper 1 addresses the whole-network optimization layer and asks whether independent operators of electricity networks have an incentive to cooperate in optimizing their interconnected networks. It demonstrates an incentive problem in power network operator interactions that turns these into game-theoretical problems like prisoner’s dilemma and chicken game. This makes optimization of electricity network as a single system difficult. Papers 2, 3 and 4 explore the whole-chain optimization layer of energy system integration which focuses at coordination between electricity network and power generation, storage, and consumption. Paper 2 evaluates the economic efficiency of administrative network congestion management, that is addressing network congestion by an administrative rule, and provides a policy advice on an efficient design. Paper 4 provides a similar result for market-based alternatives, where network congestion is addressed by market-based coordination between network and network users. Paper 3 reviews the empirical experience with such market-based type of congestion management. Paper 5 is concerned with the cross-system optimization layer. Aiming to provide a policy advice on a coherent institutional framework governing investment in the future hydrogen infrastructure, which is expected to be dispersed across multiple energy sectors, it reviews and evaluates current governance proposals raised by the European institutions.
Beyond Western Influences: Development and Reforms of Social Protection and Pension Schemes in China since 1978 (2024)
Tian, Tong
Over the past 40 years, a modern welfare state has emerged in the People’s Republic of China (PRC). Social protection has thereby extended from a selected group of privileged state employees and civil servants to most of the population. This dissertation argues that the significant extension of social protection, and of pension schemes in particular, is not only a consequence of domestic economic development and political reform; international influences also manifested themselves during the course of the development and reforms of the Chinese social protection system. My key research question is: How have international influences impacted on Chinese social security and pension reform? While I do analyze the roles of “Western” influences and International Organizations, I particularly focus on one important gap in the literature – the scarcely studied role of “Eastern” or East Asian influences on Chinese social protection development. Theoretically, this dissertation builds on the policy learning literature as well as the concept of East Asian welfare productivism to explain how international influences impacted on Chinese social protection expansion and reforms and to better understand welfare features the PRC shares with its East Asian neighbors. Regarding methodology, this dissertation employs several methods in the tradition of qualitative research: process tracing, document analysis, and discourse analysis. The core data of this research was collected via expert interviews during fieldwork in China. Moreover, archive data, official policy reports in Chinese, English and Japanese, and other primary and secondary data were utilized. This cumulative dissertation consists of four interdependent articles focusing on the development and expansion of Chinese social protection under international influences, and especially on the two major reforms of Chinese pension schemes: the 1990s Urban Employee Pension Reforms, and the 2009 New Rural Pension Scheme.
The effects of climate change and climate variability on the distribution of Atlantic cod (Gadus morhua) in the Arctic (2023)
Spotowitz, Lisa
The Arctic is experiencing warming to a much higher degree compared to other regions on Earth. The annual mean surface temperature between 1971 and 2019 was three times higher than the global average (AMAP 2021). While previous warm episodes like the Early Arctic warming occurring from the 1920s to 1960s are known to be driven by natural processes like changes in the North Atlantic Oscillation (NAO), recent studies provide evidence that the ongoing Arctic warming process differs from the earlier phases and that it is caused by anthropogenically induced large-scale global warming. Consequences for the local marine ecosystem can be, among other things, a shift in species abundance and distribution from a polar towards a more boreal community. In this context, fish species like the Atlantic cod (Gadus morhua) are reported to have risen in abundance in the Arctic region over the last decades. This dissertation focuses on the effects of climate change and climate variability on the population structure and spatial distribution of Atlantic cod in the fjords of Svalbard. A combination of different methods was used and included fishing campaigns in several locations on the coast of Svalbard, genetic studies on the ecotype composition of the catches, otolith studies on subpopulation structure, and year-round in situ camera observations on the occurrence of juvenile cod in the shallow waters of the Kongsfjorden ecosystem. Based on the combined use of observation, otolith shape, and genetic tools, a local ecotype, the “Svalbard coastal cod (SCC)” could be identified as a potential permanent resident in Svalbard fjords. Eggs or larvae of Atlantic cod could not be identified in the catches, nevertheless, eggs of long rough dab have been found during the ichthyoplanktonic surveys indicating spawning in the area. Both, Atlantic cod, and the long rough dab share a similar lifestyle and demonstrate the recent invasion of boreal species into the Arctic marine ecosystem.
Trace metals and organic matter in the Amazon-Pará River Estuary (2023)
Hollister, Adrienne
The Amazon is the largest River on earth, accounting for 15–20% of the global river freshwater discharge, and making it an important source of trace metals, nutrients and organic matter to the Atlantic Ocean. The nearby Pará River is the 5th largest river and converges to mix in the Amazon Estuary. Trace metals in the ocean (e.g., Mn, Co, Fe, Ni, Cu, Zn, Cd and Pb) act as important nutrients and/or toxins to marine organisms. However, no data exists for these trace metals in the Amazon Estuary after 1976. Therefore, it is of urgent importance to establish a baseline for trace metals in the Amazon estuary. A GEOTRACES process study (cruise GApr11) was conducted in the Amazon estuary during the wet season (April–May) of 2018. Herein we present data for dissolved trace metals and organic matter from samples collected from this cruise. Chapter 1 focuses on copper (Cu), a micronutrient and potential toxin, and its complexation to organic ligands. Chapter 2 discusses two other micronutrients, cobalt (Co) and nickel (Ni), in surface and depth samples analyzed by two different methods. Chapter 3 brings together all trace metals from this study (Al, Mn, Co, Fe, Ni, Cu, Zn, Cd, Pb and U) to calculate the fluxes from the Amazon and Pará Rivers into the Atlantic Ocean. Finally, chapter 4 describes depth profiles of bioactive metals in different size fractions. Trace metal cycling in the estuary was influenced by complex biogeochemical processes, including ligand complexation, particle adsorption-desorption, colloidal flocculation, physical mixing and biological activity. In addition, we observed distinct influences from the Amazon and Pará Rivers, which draw from distinct catchment areas. Cu was mostly conservative with respect to salinity, while Fe and Pb were highly particle reactive during early mixing and experienced the greatest estuary removal. We estimated that the Amazon and Pará Rivers account for ~21% and 18% of the global riverine Cu and Ni to the oceans.
A first approach to seawater gallium-aluminium systematics throughout Earth’s history (2023)
Ernst, David
Marine chemical sedimentary rocks, like banded iron formations (BIFs), ferromanganese (Fe-Mn) crusts and nodules, marine carbonates or cherts, are of great scientific interest because they can preserve primary information on the physico-chemical conditions of ambient seawater. Especially for research on the Precambrian, marine chemical sedimentary rocks are invaluable archives as they are the only remaining access point to the geochemical conditions of the Archaean and Palaeoproterozoic marine environment. This PhD thesis investigates the geochemical partner couples of gallium, aluminium (Ga-Al), germanium, and silicon (Ge-Si). Those two couples show mostly coherent geochemical behaviour in igneous and clastic sedimentary processes. However, in (low- low-temperature) aqueous environments, both partners decouple from each other. This thesis aims to investigate the behaviour of Ga-Al and Ge-Si during the precipitation of Fe (oxyhydr)oxides in the natural environment and to elaborate on whether characteristic distributions of Ga/Al and Ge/Si ratios in marine chemical sedimentary rocks can be applied as geochemical proxies.
Designing Virtual Constraints for IT-Supported Creativity (2023)
Pilcicki, Raoul
Increasingly decentralized collaboration drives the development of new creativity support systems (CSS) that offer virtual teams various means for communication, information exchange, and creative collaboration. As CSS aim to mitigate the limitations of virtual communication and collaboration, reason suggests that more functionalities yield better outcomes. Hence, a wide range of capabilities for interaction, knowledge sharing, or innovative collaboration processes is implemented into these CSS. However, if CSS offer functionalities beyond the required level, they can become confusing to use, overload users, or cause feature fatigue. Previous research shows that having more options or functionalities does not always lead to better results, especially in the context of creativity, and suggests a curvilinear relationship between constraints and creativity. While the effects of constraints on creative collaboration have been studied in analogue settings before, their design and application to support creative collaboration in virtual contexts, remains under-researched. This PhD thesis examines how constraints in CSS can be designed to foster creative collaboration and contribute to a better understanding of how limited functionalities and interactions during particular phases of creative collaboration can help individuals and teams access a CSS's instrumental potential and benefit from idea generation and exploration beyond routine performance, and encourage more radical forms of creativity. To support the evolution of knowledge about the theory and practice of CSS design, this research project follows a design science research (DSR) approach.
Synthesis, Structural Characterization and Catalytic Studies of Peroxo-Containing Heteropolyanions (2023)
Sundar, Anusree
Polyoxometalates (POMs) are discrete, anionic metal-oxo clusters comprising early d-block metal ions in high oxidation states. Due to the large compositional and structural variety, POMs exhibit many interesting physicochemical properties including catalysis.POMs containing peroxo-groups are of special interest in hydrogen peroxide-assisted oxidation catalysis. In this thesis, the focus is on the synthesis of novel peroxo-containing POMs, the solid-state and solution characterization, and a study of their H2O2-based biphasic homogenous as well as heterogenous oxidation catalysis. Chapter 1 is an introduction of POMs and peroxo-POMs, whereas in Chapter 2 the motivation for the planned work is lined out. In Chapter 3, the experimental details are described, as well as the instruments used for the structural characterization and catalytic studies. In Chapter 4 some novel peroxo-Zr/Hf-containing Wells-Dawson anions are reported, which were studied for various H2O2-mediated oxidation reactions, using homogenous and supported conditions. A comparative study was also carried out on structurally-related peroxo-Zr/Hf Keggin anions. In Chapter 5 several novel peroxo-Ce-containing POMs of the Wells-Dawson type were isolated and structurally characterized in solution and in the solid state, followed by a comparative catalytic study using homogenous and supported conditions for the biphasic alcohol oxidation as well as alkene epoxidation. Chapter 6 describes the synthesis and characterization of a peroxo-Ce-containing POM of the Keggin type with the highest nuclearity amongst all peroxo-cerium POMs reported to date. Finally, Chapter 8 describes the synthesis and structural characterization of two dimethylarsinate-containing molybdenum-oxo clusters, a large, anionic mixed-valence wheel and a small neutral species. The novel compounds were mainly characterized in the solid state by FTIR,TGA, elemental analysis and XPS, and in solution by NMR and UV-Vis spectroscopy.
From back-arc spreading center to volcanic arc: Hydrothermal vent fluid chemistry across the North-East Lau Basin, SW Pacific (2023)
Klose, Lukas Benjamin
This PhD thesis focuses on the investigation of high-temperature hydrothermal vent fluids from multiple vent sites between the North-Eastern Lau Spreading Center and the Tofua arc. The sampling area is located in the northeastern part of the Lau Basin which is affected by some of earths’ highest subduction rate, a highly complex microplate tectonic, an influence of hot spot material from the Samoan mantle plume as well as the subduction of the Louisville Seamount Chain. This study extends our knowledge of high-temperature hydrothermal systems in the North-East Lau Basin, in that it reports for the first time on the chemical and isotopic composition of vent fluids from Maka volcano and Niuatahi volcano. This cumulative PhD thesis highlights the compositional variability of hydrothermal fluids associated with different geologic settings. The newly reported vent fluid data as well as systematic spatial distribution of trace metals and metalloids adds to our understanding of hydrothermal processes and in the future may help improve the estimates of element specific fluxes associated with seafloor hydrothermalism.
The Potential of Fungal Biomass as Industrial Catalyst: Modification of Lipids (2023)
Elhussieny, Nadeem Ibraheem Hussien
This study investigated the potential of fungal biomass as industrial catalyst through developing an alternative catalyst for biodiesel production using fungal biomasses for whole-cell catalysis. The research explored various fungal isolates and identified the most potent isolates. The transesterification catalytic capability of the selected isolates was improved through random genetic mutagenesis and optimization of the cultivation conditions of the chosen mutants. Aspergillus flavus and Rhizopus stolonifer two fungal species belong to two different phyla (Ascomycota and Zygomycota) revealed the capability of their biomasses to catalyze the transesterification reaction efficiently up to 95.5 %, in relatively short reaction time (24 h.). The biomass produced was also capable of catalyzing the transesterification reaction using different acyl-acceptors. A. flavus and R. stolonifer biomasses proved the probability of using biomasses cocktails to catalyze transesterification reaction. In addition, the fungal biomass investigated exhibited considerable ability to catalyze the hydrolysis of triglycerides, which means an opportunity of producing multifunctional catalytic fungal biomass. A. flavus showed a potential to be implemented in biorefinery processes that include wastewater treatment by microalgae as part of a circular economy approach, where A. flavus biomass produced in a biorefinery approach was effectively capable of catalyzing the modification of lipids.
Microplastics in the Weser – North Sea transitional system: Potential pathways and methodological improvements (2023)
Roscher, Lisa
Microplastics (MP) have received increased scientific, political and societal attention due to their environmental omnipresence. This thesis aims to provide comprehensive data on aquatic MP pollution through the application of state-of-the-art analytical methods, and compares data outputs from two data pipelines. Within the River Weser–North Sea transitional system, small MP (<500 µm) predominated, with a notable abundance of suspected paint particles. Large MP (>500 µm) exhibited low abundances, mainly composed of the common plastic polymers polyethylene and polypropylene. The estuary’s turbidity maximum zone showed the highest MP concentrations, then declining towards the North Sea, possibly influenced by increased vertical and horizontal export or dilution in the larger marine water body. Additionally, this thesis evaluated two wastewater treatment plants as potential riverine MP point sources. Interference by post-processing residual material required an adaptation of the FTIR reference database by the inclusion of new reference material. Results showed that polyolefins were prevalent in the effluent, and that observed temporal patterns in MP concentrations could be partially explained by technical and environmental parameters. Input of MP into the River Weser via effluent is likely, necessitating more research to understand the full dynamics of MP pollution within this river system. Furthermore, the MP analysis pipeline comparison study showed discrepancies for certain polymer types, possibly due to different polymer grouping methods, or overestimation effects. By excluding these polymer types, both datasets generally were in accordance, suggesting a harmonization of both pipelines should be undertaken to improve comparability of MP data. In summary, this thesis provides a detailed foundation for understanding MP dynamics in the River Weser–North Sea system and highlights methodological challenges inherent in the field of MP pollution research.
Study of E. coli outer membrane proteins to understand and combat antibiotic resistance (2023)
Paul, Eshita
Antibiotic resistance poses severe threats on mankind and ruins the greatest of medical advancements. At the economic level, it not only causes loss of productivity but also creates huge burden on healthcare expenses. Regarding antibiotic resistance Gram-negative bacteria especially the ESCAPE pathogens are in the limelight as they are responsible for the highest mortality rates. Their multidrug resistance results from a combination of factors including modification of antibiotic uptake pathway as well as decreased intracellular concentration of drugs. Reduced intracellular drug retention is a result of drug elimination and is mostly driven by RND-family of efflux pumps. AcrAB-TolC is a prototype of this family in E. coli. TolC being the outer membrane component of this efflux machinery is readily available for reconstitution on synthetic lipid bilayers and thus allows substrate interactions to be studied at a single channel level. In the present study, biophysical approach to identify small chemical molecules as TolC inhibitors is described. In order to observe their interaction with TolC at a single molecule level, traditional electrophysiology technique has been used and method’s resolution is extended using principles of protein engineering as well as novel data analysis considering also the ion current fluctuations. At the same time, porin dependent translocation of a therapeutically important class of antibiotics is studied and novel uptake pathways are reported. Although, not directly beneficial to clinical development, outcomes of these studies will help to open new ways for further research and I hope this thesis will be useful despite having many open-ended questions.
From Bench to Bedside: Development of a MAPPs assay-based personalized healthcare tool to evaluate the clinical immunogenicity of therapeutic antibodies (2023)
Hartman, Katharina
Despite success, the use of therapeutic monoclonal antibodies (mAbs) in clinical settings has been complicated by the ability of the patient’s immune system to provoke an unwanted humoral immune response against the drug, generally through the formation of anti-drug antibodies (ADAs) – termed immunogenicity. ADA onset may compromise clinical efficacy and impact safety in patients. A fundamental area of immunogenicity research is investigating mAb-derived peptides processed by dendritic cells (DCs) and presented through major histocompatibility complex (MHC) class II receptors. These mAb-derived peptides, representing potential T cell engaging epitopes, orchestrate the immunogenicity cascade by directly influencing T cell activation leading to ADA production. The MHC-II-associated peptide proteomics (MAPPs) assay is a Roche-invented methodology to identify and quantify such potential T cell epitopes. As an integrated approach during preclinical drug development, MAPPs is used alongside other in vitro, in silico, and in vivo tools to address the risk of immunogenicity. This PhD work aims to extend the applications of MAPPs for the development of a tool for personalized healthcare (PHC) in the clinic with the purpose of identifying patients with a potential risk of immunogenicity prior to treatment in order to devise an ideal treatment plan (main aim 1). Moreover, since most MAPPs studies are currently restricted to HLA-DR as the dominant MHC-II genotype due to lack of satisfactory MHC-II receptor-precipitating reagents available, an immunoprecipitation strategy using the MAPPs assay alongside the advanced epitope–prediction algorithm NetMHCIIpan was developed to accommodate MHC-II pan receptors for improved predictability of potential T cell epitopes (main aim 2). Taken together, these reformed uses of the MAPPs assay will lead to an invaluable clinical tool for immunogenicity risk assessments that support personalized healthcare.
Synthesis, Structure and Catalysis of Polyoxo-Noble-Metalates (Pt, Au, Pd) and Noble Metal (Pt, Rh)-Containing Polyoxometalates (2023)
Zhang, Jiayao
This thesis is divided into six chapters. Chapter I generally introduces the historical background, structural aspects, properties, and applications of POMs, the state of the art of polyoxo-noble-metalates, noble-metal-containing POMs and arsenic compound, as well as the motivation to perform this work. Chapter II includes the information of applied analytical techniques and synthetic procedures for the used POM and organorhodium(III) precursors. Chapter III is devoted to polyoxoplatinate, polyoxopalladate and mixed polyoxo-noble-metalates, and 7 novel polyoxo-noble-metalates have been obtained with the following highlights: (i) The first PtIV-containing discrete polyoxoplatinate(II) Pt7 and polyoxopalladate(II) PtPd6 have been prepared and characterized in the solid-state, in solution, and in the gas phase; (ii) The first discrete mixed platinum(IV)-gold(III) oxoanion Pt2Au3 was structurally characterized in the solid state by single-crystal XRD and TGA, and in solution by multinuclear NMR and ESI-MS studies. Chapter IV presents 3 novel Platinum(II/III)-containing isopolytungstates. The polyoxoanion Pt3W11 consists of three {W3O13} and one {W2O10} fragments connected by three Pt(II) atoms forming linear {Pt3O12} triad. The polyoxoanion PtII2W5 and PtIII2W5 both consists of one lacunary Lindqvist fragments {W5O18}6− coordinated by two Pt(II) in square planar coordination and two Pt(III) with direct Pt–Pt bonding, respectively. Chapter V describes the synthesis of three all-inorganic platinum arenate(III) compound. The first two full inorganic discrete platinum arsenate(III) clusters: PtAs6 and Pt4As8, have been synthesized in aqua media. In Pt4As8, Each Pt atom is coordinated by two O atoms and two As atoms involved in direct As-Pt bonding. And a platinum arsenate(III) heteropolytungstate Pt2As6W4 has been synthesized in aqua media and characterized by 195Pt NMR.Chapter VI deals with the synthesis and characterization of two RhCp*-containing heteropolytungstates.
Application of Machine Learning and Optimization to Problems in Supply Network Management (2023)
Lyutov, Alexey
The field of logistics and supply chain management deals with various supply network problems on multiple levels starting from strategic years-long decisions regarding network topology, down to operational weekly-based decisions. Moreover, due to the interaction of customers and random accidents, the system becomes stochastic and difficult to control based only on logistic experience. To help with the problem of supply chain design and management, scientists try to approach the field with existing instruments including network science, mathematical modeling, control theory, machine learning, etc. In this thesis, a complex approach that addresses different aspects of supply network management is demonstrated. First, an automatization scheme for the daily management of logistic requirements is proposed. Second, an in-depth investigation of non-conventional usage of natural language processing and machine learning algorithms is presented. The developed approach can be used to enhance the process of requirement management by extracting additional knowledge about the supply network operation. Third, the strategic problem of designing robust supply networks is addressed by developing a minimalistic model of a supply network. The model is designed to simulate a scenario of supply-demand imbalance and generate networks that satisfy the imbalance in a robust way. The overall outcome of the work is a better understanding of separate supply network aspects and an attempt to holistically improve the way how supply networks are managed.
Comparing the long-term effects of health behaviours and health problems on depression among the elderly in Germany and Taiwan (2023)
Chiang, Rose Pei-Fang
Depression is rising both in Germany and Taiwan among all age groups but specially, also among elderly. In Taiwan, a larger proportion of users of antidepressants are over 65 years of age (NHI, 2020). In Germany, 24 % of people aged 65+ reporting depression symptoms in 2017 (OECD, 2019). Data were extracted from the DEAS and the TLSA. Both of DEAS and TLSA were a countrywide representative survey. The scale used to measure depression in the two surveys was the CES-D. Data analysis included regression models, specifically logistic regression, and Generalized Estimating Equations. The McNemar test and Mantel-Haenszel test was applied to examine the consistency of the responses of the same group of subjects before and after the test. The study found that in Germany, subjects with heart disease, cancer, and poor self-rated health (SRH) were more likely to suffer from depression. In Taiwan, subjects with diabetes, heart disease, stroke, cancer, and poor SRH were more likely to be depressed. Both countries showed that the drinking and exercise groups had a lower chance of developing depression. Widowhood increased the risk of developing depression, but there was no gender difference. In addition to maintaining and improving physical health, exercise has been proven in this study to relieve psychological depression. Partnerships, on the other hand, provide social bonding and social support for middle-aged and older adults. Without a spouse, there is an association with more psychological health constraints like depression in older people living in Germany and Taiwan. Getting out and building relationships with friends and exercising together could be a good way to decrease the risk of depression among the elderly. According to attachment theory, having a stable relationship with some friends can also help the emotions of the elderly recover from the death of their spouse.
Synthesis and Reactivity of 2-Diazo-1,1,3,3,3-Pentafluoropropyl Phosphonate (2023)
Hajdin, Ita
Diazo compounds are remarkable versatile building blocks and increasingly important molecules in organic synthesis. Even though the field of diazo chemistry was discovered more than hundred years ago it is still a subject of great research interest. Besides, the field of organofluorine chemistry has grown immensely in recent years, and fluorochemicals have permeated into nearly every aspect of our daily lives. Hence, the aim of this work was the synthesis of a bench-stable 2-diazo-1,1,3,3,3-pentafluoropropyl phosphonate, the first fluorinated diazo compound bearing trifluoromethyl and difluoromethyl phosphonate moiety, along with a demonstration of its synthetic applications in a series of chemical reactions. After the successful synthesis, the novel diazo compound was incorporated in cyclopropanation reaction of aromatic and aliphatic terminal alkenes using CuI as a catalyst. Consequently, sixteen new cyclopropanes were synthesized in good to very good yields and under mild reaction conditions. Furthermore, a new pathway for synthesizing fluorinated β-alkoxy vinyl phosphonates via O-H insertion reaction using Rh2(OAc)4 as a catalyst is presented in this thesis. The insertion reaction of benzyl and aliphatic alcohols using the diazo compound were carried out under mild conditions and nineteen new fluorinated β-alkoxy vinyl phosphonates were synthesized in good to very good yields. The following reaction was a catalyst- and solvent-free 1,3-dipolar cycloaddition of alkynes and alkene with the diazo compound. This green approach provided an efficient route for direct synthesis of fluorinated pyrazoles and pyrazoline in moderate to excellent yields. Lastly, a Cu(II) catalysed [2,3]-sigmatropic rearrangement reaction of propargyl and allyl sulfides with the diazo compound produced products bearing difluoromethylphosphonate and trifluoromethyl groups.
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