University of Siegen
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Publication Access status: Open Access , The Idleness of Mobility Behaviour – Contributions and Challenges of Subsidisation and Digitalisation to Turn the Tide in Favor of Sustainable Public Transport(2026-03-24)This dissertation examines how innovative mobility concepts, price mechanisms, and technological developments influence mobility behaviour, the acceptance of sustainable modes of transport, and the future design of public transport (PT) in Germany. Drawing on Vincent Kaufmann’s concept of mobility as a form of social action potential, mobility is understood as the interplay of structural access, individual capabilities, and cultural processes of appropriation. The dissertation thus addresses a research gap at the intersection of behavioural economics, social sciences, and technological mobility research. The work employs a mixed-method design combining quantitative analyses on price and subsidy mechanisms (Studies 1–3) with qualitative investigations on digitalisation and autonomous buses (Studies 4–6). User surveys, regression models, expert interviews, and scenario-based explorations provide a differentiated empirical picture of current and potential mobility dynamics. The findings reveal that price incentives – such as climate tickets or rising fuel prices – can trigger short-term shifts in the modal split, yet do not induce a sustained shift away from private motorised transport (PMT) in the absence of structural improvements. Once subsidies run out, PMT is frequently chosen again, particularly in regions with limited PT quality. Price mechanisms thus unfold their effectiveness only in combination with reliable, spatially accessible, and userfriendly services – a core dimension of Kaufmann’s mobility concept. Furthermore, the results show that ecological motivation is constrained by economic conditions. During periods of economic volatility, financial considerations tend to dominate mobility decisions. Socially balanced fare models and targeted subsidies are therefore central prerequisites for socially viable mobility strategies. Digitalisation offers the potential to structurally reduce deficits in PT provision. Digital bus stop concepts, real-time information and mobility platforms improve accessibility and the user experience, while on-demand services enhance flexibility, particularly in rural areas. However, the success of digital innovations ultimately depends on societal acceptance. The studies indicate that, although autonomous buses are regarded as a response to the growing shortage of bus drivers, reservations persist, especially among younger users, driven less by technical concerns and more by social and work-related considerations. The findings show implications for three groups of stakeholders. For policy makers, a systemic approach is required that integrates pricing, infrastructure development, and digitalisation. For mobility users, the results highlight that conscious mode choice, digital competencies, and active participation in feedback or planning processes constitute essential elements of stable modal-shift dynamics. Transport companies face the challenge of evolving from reactive service providers to strategic designers of multimodal mobility environments that integrate physical, digital, and fare-related components. Overall, the studies demonstrate that sustainable modal shift is not the result of isolated measures but emerges from the multifaceted interaction of structural, cultural, and technological factors. Transforming PT therefore requires long-term, socially balanced, and technologically adaptive strategies. Looking ahead, digital innovations, autonomous driving, and integrative subsidy structures will be key components of a mobility culture that aligns ecological objectives with social participation and everyday functionality. This dissertation thus contributes to the theoretical foundation and empirical analysis of the mobility transition and identifies central avenues for future national and international research.Source Type:Doctoral Thesis4 3 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Consumers’ Information Systems: Managing Consumption within Households and in Interaction with Digital Firms(2026-05)This dissertation investigates the information systems underlying consumption by shifting the analytical focus from firms to private households. While traditional Information Systems research has extensively examined how digital technologies support organizational processes within firms, the complementary domain of consumption—where individuals coordinate, manage, and enact market transactions—has remained comparatively underexplored. Building on the premise that consumption is not a passive act but involves substantial managerial, coordinative, and cognitive effort, I conceptualize these activities as consumers’ work. This work unfolds within the household as an economic unit as well as at its boundary to the market, where consumers interact with firms under conditions of bounded rationality, information asymmetries, and an increasing digitalization driven by the platform economy and a growing “everything-as-a-service” subscription paradigm. The theoretical foundation integrates perspectives from sociology, (New) Home Economics, as well as New Institutional approaches, and synthesizes them to be examined through a socio-technical IS lens. Sociological research highlights the often invisible, unequally distributed, and cognitively demanding nature of household labor, particularly its managerial and administrative dimensions. Economic perspectives reconceptualize households as productive units and emphasize the costs of coordination inherent in market transactions. Complementing these views and following prior empirical research on money work within the CSCW and HCI communities as well as theoretical considerations on technically intermediated markets, IS research provides a newly socio-technical understanding of consumers’ work systems and mechanisms. Methodologically, the dissertation follows a retroductive design inquiry grounded in critical realism and abductive reasoning, moving iteratively between a problem space (consumers’ work) and a solution space (emerging work-supporting technologies). It combines inductive empirical exploration with theory-building across four interrelated studies conducted in Germany, each addressing a specific research objective. Study 1 follows the artifact “invoice” through 17 households to reconstruct domestic accounting as a spatio-temporal practice. Study 2 develops a taxonomy of twelve administrative task categories and quantifies temporal workload, mental workload, and satisfaction in an online survey with 617 socio-demographically distributed participants. Study 3, drawing on the same dataset, maps the devices, tools, specialized software, and physical workplaces consumers appropriate for this office-like work at home. Study 4 employs interviews and a week-long field study with five intermediary firms in finance, insurance, utilities, health, and general administration to investigate how intermediaries mediate and partially take over consumers’ work in market coordination. Together, the studies provide a mixed-method, multi-level, and multi-perspective understanding of consumers’ work across different tasks involving different kinds of technologies. The dissertation’s outcome advances both theory and practice by conceptualizing consumers’ work as a boundary practice situated between households and markets, articulated through a socio-technical framework that captures the interplay of structures, people, tasks, and technologies. Empirically, the findings demonstrate that consumers perform substantial, often underestimated and unseen labor in managing consumption. Invoice handling, for example, unfolds as a fragmented spatio-temporal practice across paper-based and digital media. The identified twelve administrative task categories differ considerably in mental workload and satisfaction, with tax affairs, problem management, governmental affairs, long term contracts, and insurance emerging as priority pain points for design. Emerging digital services, from financial management tools and contract managers to intermediary platforms, already intervene in and reshape these work practices. Conceptually, the dissertation contributes (I.) an integrated chain of consumption management that links intra-household administration with market-directed activities across five phases (anticipating, identifying, deciding, monitoring, and modifying); (II.) the introduction of heteronomy imposed by external institutions as a design variable that work supporting technology must explicitly address rather than ignore; and (III.) a reframing of intermediaries as a socio-technical infrastructure of market cooperation that bridges social and technical interoperability gaps through its own socio-technical measures, such as “adversarial” or “backward” interoperability. In doing so, the dissertation provides an empirically grounded conceptualization of theories such as intermediation or Vendor Relationship Management while also generating new empirical evidence and concepts. By positioning consumers as active agents who perform essential economic work, this dissertation opens a new line of inquiry for IS research and contributes to a broader understanding of digital transformation that encompasses not only firms but also the everyday practices of individuals in the economy. It thereby extends the traditionally firm-centered focus of Business Informatics with a complementary consumer-centered perspective and positions Consumer Informatics as an essential site of inquiry within IS research.Source Type:Doctoral Thesis20 6 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Sprachbildende Schulbuchaufgaben im Fachunterricht - Qualitative Inhaltsanalyse und Intervention(2026)In diesem Open-Access-Buch wird ein zentrales Problem schulischer Praxis aufgegriffen: Schulbuchaufgaben können für Schüler:innen schwer verständlich sein und nur begrenzte Unterstützung für den Erwerb bildungssprachlicher Kompetenzen bieten. Auf Basis einer Mixed-Methods-Studie mit 1.357 Aufgaben aus den Fächern Wirtschaft-Politik und Physik wird untersucht, welches Lern- und Schreibpotenzial sie aufweisen und wie sich dieses gezielt ausbauen lässt. Eine systematische Aufgabenanalyse wird dabei mit einer Interventionsstudie in einem hybriden Lernsetting verbunden. Die Ergebnisse zeigen sowohl fachübergreifende Herausforderungen der Aufgabenkultur als auch fachspezifische Unterschiede. Zugleich wird deutlich, wie schreibförderlich gestaltete Aufgaben fachliches und sprachliches Lernen produktiv verbinden können. Der Band richtet sich an Forschende, Lehrkräfte, Schulbuchautor:innen und Studierende, die Unterricht sprachbildend gestalten und Lernumgebungen – einschließlich generativer KI – reflektiert und wirksam einsetzen möchten.Source Type:Doctoral Thesis32 6 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , More than a Lifetime: Towards Precision Predictions for B-Meson Decays in the Standard Model and Beyond(2026)This thesis presents a systematic investigation of heavy hadron lifetimes, focusing on the $B$ mesons, as a probe of both Standard Model (SM) dynamics and possible effects of physics beyond the SM (BSM). Within the framework of the Heavy Quark Expansion (HQE), we compute, at leading order in QCD, the complete dimension-seven two-quark contributions, corresponding to the $1/m_b^4$ corrections, for the CKM-favoured non-leptonic decays $b\to c\bar{u}d$ and $b\to c\bar{c}s$, providing the full analytical expressions for the corresponding Wilson coefficients. These results, which reveal new matrix elements unique to non-leptonic decays, lay the foundation for future numerical studies and refined SM lifetime predictions. Having extended the SM calculation to the next order in the HQE, we turn to the dimension-six Darwin contribution, whose sizeable numerical impact in the SM motivates its generalization to a model-independent BSM framework. In particular, we derive, at leading order in QCD, the Wilson coefficients up to and including the dimension-six two-quark (Darwin) operators, corresponding to the $1/m_b^3$ corrections in the HQE, for non-leptonic decays induced by a general effective Hamiltonian. We further determine the previously missing dimension-six four-quark weak-annihilation contribution induced by the same general operator basis. Since the SM QCD-penguin operators are contained within this basis, our calculation also yields, as a special case, the previously missing dimension-five and dimension-six contributions induced by the SM QCD-penguin operators, thereby further improving the theoretical precision of HQE predictions. Finally, we explore the phenomenological implications of the $B$-Mesogenesis model, which links the matter–antimatter asymmetry of the universe and dark matter to exotic $B$-meson decays. The model is tested through both inclusive and exclusive decay channels: the inclusive analysis, performed within the HQE, quantifies the impact of these new decay modes on the total decay rates and the lifetime ratios $\tau(B^+)/\tau(B_d)$ and $\tau(B_s)/\tau(B_d)$, while the exclusive analysis employs light-cone sum rules to calculate the branching fraction for the exclusive decay $B^+\to p\psi$, involving a proton and a dark-sector fermion in the final state. By comparing our predictions with experimental limits from BaBar, Belle, and Belle II, we constrain specific effective operators of the model. Furthermore, by examining power-suppressed terms, we identify regions in the dark-sector mass parameter space where subleading effects exceed the leading dimension-three contributions—offering new insight into the applicability of the operator product expansion within the HQE. Together, these studies advance the theoretical understanding of heavy-hadron lifetimes, strengthen the bridge between precision flavour physics and physics beyond the SM, and open new avenues for probing the interplay between heavy-quark dynamics and the dark sector.Source Type:Doctoral Thesis38 7 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Wenn der Markt nicht regeln kann: Klimaneutralität zwischen Wirtschaftswachstum und gesellschaftlicher Akzeptanz(2026-06-23)Die Aktualität des Miteinanders von Wirtschafts- und Klimapolitik ist kaum zu übersehen. In vier Kapiteln beschäftigt sich die kumulative Dissertationsschrift mit dem Verhältnis von Wirtschaftswachstum und gesellschaftlicher Akzeptanz auf dem Weg zur deutschen Klimaneutralität. Dabei verbindet die Arbeit Ansätze der Ökologischen Ökonomik, des Ordoliberalismus und der Umweltökonomik. Die einzelnen Kapitel thematisieren: (1) die Stärke ökonomischer Multiperspektivität im Postwachstumsdiskurs, (2) eine Analyse von Modellannahmen deutscher Klimaneutralitätsszenarien, (3) das Konzept einer Sozialen Marktwirtschaft innerhalb planetarer Belastungsgrenzen sowie (4) die Ergebnisse deutschlandweiter Expert:inneninterviews zu den Hürden und Erfolgsfaktoren im kommunalen Klimaschutz. Die Dissertation zeigt aus unterschiedlichen Perspektiven, wie der klimapolitische Ordnungsrahmen der Bundesrepublik für ein zukunftsfähiges Wirtschaftssystem ausgestaltet sein sollte: widerspruchsfrei, effizient und konsistent zur klimawissenschaftlichen Datenlage.Source Type:Doctoral Thesis104 55 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Deterministic Superscalar AI Hardware Accelerator for Dependable Embedded Real-Time Systems(2026-10-12)Safety-critical real-time systems that rely on AI-based object classification and detection for critical decision-making require strict guarantees of reliability and timing correctness, as even minor deviations in behavior can lead to catastrophic consequences. Integrating AI hardware accelerators into such real-time environments therefore demands not only high computational throughput but also predictable and analyzable execution behavior. Conventional accelerators, such as the Versatile Tensor Accelerator (VTA), meet performance requirements but fall short in predictability due to their event-driven execution model and limited timing control. This variability introduces significant risks in scenarios where timely and deterministic inference is essential. To address these limitations, this work adopts a time-triggered execution paradigm for AI acceleration. It first introduces the Time-Triggered VTA (TT-VTA), which replaces the non-deterministic behavior of the original VTA with a deterministic counterpart based on statically defined, pattern-based timing schedules. These schedules are generated offline at design time using a scheduler with a built-in simulator for the VTA architecture. The scheduler further integrates additional simulation frameworks: DRAMSim2 is used to model memory-related instructions, while a cycle-accurate simulator captures compute-bound operations. Together, these components enable precise timing analysis, deterministic resource utilization, and predictable execution behavior. Evaluation with a CNN classification model shows that the TT-VTA preserves classification accuracy while ensuring predictable execution, however with a slight increase in inference latency (53 ms compared to 51 ms for conventional VTA), indicating room for further optimization. Building on this foundation, the Superscalar Time-Triggered VTA (STT-VTA) is proposed to improve performance without sacrificing determinism. STT-VTA extends the architecture by exploiting parallelism through multiple coordinated accelerator functional-units, whose configuration is determined at compile time via an enhanced architecture management and scheduling framework. This framework analyzes the computational structure needed for the target AI model and generates optimized schedules that maintain strict timing guarantees while increasing throughput. Experimental results demonstrate that the STT-VTA achieves the same classification accuracy as both TT-VTA and conventional VTA, while reducing inference latency by 17-41% compared to the TT-VTA. With the STT-VTA, another challenge arose in managing memory-intensive workloads, which introduce performance bottlenecks. To address this, the work further incorporates deterministic caching and pre-fetching strategies, leading to the Superscalar Time-Triggered VTA with Caching and Pre-fetching (STA-CP). Unlike conventional dynamic approaches, these mechanisms are integrated directly into the static scheduling process. At compile time, all tensor operations and memory transactions are fully specified, enabling predictable data movement and efficient overlap between computation and memory communication. By eliminating redundant memory accesses and hiding memory latency within a fully analyzable execution model, STA-CP achieves improved throughput while preserving strict temporal determinism. Experimental evaluation on different CNN classification models demonstrates up to a 30% reduction in deterministic inference latency compared to TT-VTA. Overall, the proposed STA-CP architecture demonstrates that the integration of time-triggered execution, controlled parallelism, and deterministic memory-management techniques can simultaneously achieve high performance and predictable execution behavior. These characteristics are fundamental for deploying AI accelerators in safety-critical real-time systems, where both computational correctness and strict timing guarantees are essential.Source Type:Doctoral Thesis53 11 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , HQET Sum Rules for Hadronic Matrix Elements and Applications to BSM Scenarios(2026-06-30)The Standard Model (SM) remains among the most stringently tested theories in physics, yet it leaves several open questions, including the nature of dark matter and the mechanism behind baryogenesis. Additionally, hadronic uncertainties continue to limit the precision of SM predictions relative to experimental data. To identify potential beyond the Standard Model (BSM) effects, it is essential to refine theoretical predictions through effective field theory (EFT) techniques and accurate treatment of non-perturbative contributions. My research focuses on these challenges using Heavy Quark Effective Theory (HQET) and observables related to heavy quark lifetimes and neutral B-meson mixing. Investigations of B-mixing and B-hadron lifetimes serve as a sensitive probe of Quantum Chromodynamics (QCD) and offer an indirect window into BSM physics. The heavy quark expansion (HQE) expresses the total decay rate of B-hadrons as a series in inverse powers of the b-quark mass, allowing a systematic separation of short-distance Wilson coefficients from long-distance hadronic matrix elements. These matrix elements often dominate the theoretical uncertainty in key observables, such as the lifetime ratio $\tau (B^+)/\tau (B_d)$ or the decay rate difference $\Delta \Gamma_s$. While lattice QCD offers precision in the long-term, QCD sum rules provide necessary first estimates. My first main project is computing dimension-six hadronic matrix elements using HQET sum rules, including a complete set of operators involving all BSM Dirac structures. This involves generating three-loop diagrams with a single gluon insertion, performing integration by parts reductions to master integrals, and extracting double discontinuities with advanced complex analysis techniques. An extension of this project will be to determine dimension-seven matrix elements, the dominant source of uncertainty in $\Delta \Gamma_s$, and where current lattice results suffer from very large uncertainties. In a complementary project, I investigate a BSM framework in which CP-violating oscillations and decays of $B$-mesons into a dark sector simultaneously generate the baryon asymmetry and the dark matter relic abundance. A central requirement of this mechanism is a minimal strength of new baryon number violating $b$-quark decay channels, which can be tested using both inclusive and exclusive observables. On the theory side, I compute the relevant inclusive decay rates and their impact on $B$-hadron lifetimes within the HQE, including one and two-loop contributions that depend on the same non-perturbative inputs that appear in the SM lifetime and mixing analyses. This creates a direct link between the HQET sum-rule determination of $\Delta B = 0$ matrix elements at dimension six and concrete constraints on the viable parameter space in certain $B$-mesogenesis models.Source Type:Doctoral Thesis20 10 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Development and Investigation of Polymer Brush-Based Prodrugs and Micropatterned Lipid Bilayer Membranes(2026-09-08)Verbesserte Implantatbeschichtungen werden dringend benötigt, um die Besiedlung durch pathogene Bakterien zu verhindern und damit die Bildung infektionsverursachender Biofilme zu unterbinden. Gleichzeitig sollte die Adhäsion von Wirtszellen gefördert werden, um eine erfolgreiche Integration des Implantats in das umliegende Gewebe zu ermöglichen. Materialien, die diese konkurrierende Besiedlung der Implantatoberfläche – bekannt als „race for the surface“ – zugunsten der Gewebeintegration steuern, müssen dabei hohe biomedizinische Anforderungen erfüllen, darunter Biokompatibilität, Langzeitstabilität und antibakterielle Wirksamkeit. Ziel dieser Arbeit ist es, das Verständnis von Polymerbürsten als biomedizinische Beschichtungen zu vertiefen, indem beide Aspekte des „race for the surface“ systematisch untersucht werden. Im ersten Teil wird die Kombination von Polymerbürsten mit Polymer-Prodrugs betrachtet, wodurch eine neue Materialklasse entsteht, die als „Polymerbürsten-Prodrugs“ bezeichnet wird. Hierfür wurden zwei monomere Prodrugs auf Basis der Antibiotika Chloramphenicol und Sulfanilamid synthetisiert. Diese enthalten entweder eine Ester- oder eine Iminbindung als hydrolysierbare Verknüpfung und wurden anschließend zur Herstellung entsprechender Polymerbürsten verwendet. Die resultierenden Materialien wurden umfassend charakterisiert und hinsichtlich ihrer Fähigkeit untersucht, unter physiologischen Bedingungen durch hydrolytische Spaltung der Bindungen das jeweilige Antibiotikum freizusetzen. Eine verlängerte Wirkstofffreisetzung konnte ausschließlich für das hydrolytisch labile Imin-System beobachtet werden. Dabei wurden Wirkstoffkonzentrationen erreicht, die ausreichten, um drei planktonische Stämme von Staphylococcus aureus zu inaktivieren. Der zweite Teil der Arbeit legt die Grundlage für neuartige Zellkulturplattformen auf Basis hybrider Systeme, die aus mit Polymerbürsten modifizierten Lipidmembranen bestehen. Durch die Übertragung der oberflächeninitiierten Bürstensynthese mittels reversibler Additions-Fragmentierungs-Kettenübertragungspolymerisation (RAFT) auf einen neu entwickelten UV-induzierten Ansatz konnten Polymerbürsten für die Untersuchung der Zelladhäsion auf diesen Oberflächen hergestellt werden. Es zeigte sich, dass sich die Antifouling-Eigenschaften der modifizierten Membranen gezielt über die Länge der Ethylenglykol-Seitenketten einstellen lassen, wodurch Zelladhäsion entweder ermöglicht oder verhindert werden kann. Darüber hinaus eröffnet die Kettenverlängerung der Polymerbürsten mit einem zweiten Block aus funktionalisierbarem Glycidylmethacrylat die Möglichkeit, spezifische biochemische Motive einzuführen und so zelluläre Reaktionen gezielt zu untersuchen. Insgesamt bietet die entwickelte Plattform neue Möglichkeiten, das Zellverhalten an Polymerbürsten-Grenzflächen detailliert zu analysieren.Source Type:Doctoral Thesis13 13 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Polymeric systems for antimicrobial photodynamic therapy of bacterial wound infections(2026)Antimicrobial photodynamic therapy (aPDT) is a promising alternative to conventional antibiotics for treating and preventing microbial infections, owing to its broad-spectrum activity and low potential for resistance development. For application in future advanced wound dressings, photosensitisers (PSs) must be immobilised or encapsulated to maintain a high local concentration at the site of infection. This Thesis investigates the incorporation of the FDA-approved xanthene dye Phloxine B (PhB) as a PS for aPDT into polymer-based delivery systems. The first part of this work examines the fundamental photophysical behaviour of PhB, including its absorption and emission, pH-dependence, 1O2 generation and photostability. The aPDT activity of PhB was systematically evaluated against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa), common pathogens found in wound infections, establishing its efficacy as an aPDT agent. Building on these findings, the second part of this Thesis focuses on the synthesis and characterisation of amphiphilic poly(ethylene glycol)-block-polyester (PEG-b-polyester) copolymers and their self-assembly into nanoscale assemblies for PhB encapsulation. Copolymers with varying hydrophobic block lengths formed assemblies with diameters ranging from 50-200 nm. As a water-soluble PS, PhB was encapsulated into polymeric vesicles ~200 nm in diameter, achieving dye concentrations >30 µM in the vesicle suspensions. Encapsulated PhB retained its aPDT activity, successfully eradicating both S. aureus and P. aeruginosa after 15 min of green light irradiation. The timescales of the antibacterial studies suggested at most limited internalisation of PhB, motivating the development of immobilised PhB-chitosan (CS) films. The final part of the Thesis therefore explores these PhB-CS films as aPDT surfaces, demonstrating effective inactivation of both planktonic and biofilm-associated bacteria upon light activation. Overall, this Thesis advances the integration of PhB into functional polymeric materials for application in advanced wound dressings.Source Type:Doctoral Thesis23 12 - Some of the metrics are blocked by yourconsent settings
Publication Ein datengetriebenes Verfahren zur robusten und zuverlässigen Auslegung des Niederdruck-Kokillen-Gießprozesses(2026)Diese Arbeit demonstriert einen datengetriebenen Ansatz zur effizienten Ermittlung eines robusten und zuverlässigen Arbeitspunkts im Niederdruck-Kokillen-Gießprozess. Durch dynamische Versuchsplanung, Modellierung und Optimierung werden im Rahmen der Prozessauslegung Parameterkombinationen identifiziert, die die Ausschusswahrscheinlichkeit und die Zykluszeit unter Berücksichtigung von Unsicherheiten minimieren.Source Type:Doctoral ThesisSeries:Forschungsberichte des Lehrstuhls für Umformtechnik21 12
