On the mechanics of skeletal and smooth muscle : linking structure to function

Muscle is essential to the health and well-being of animals and humans, performing crucial functions such as enabling movement (skeletal muscle) and facilitating the motility of fluids within hollow organs (smooth muscle). Muscular tissue is pervasive throughout the body, with skeletal muscle alone accounting for approximately 35% of human body mass, underscoring its biological significance. Due to its widespread presence and vital functions, muscular tissue remains a central focus of research in the natural sciences, particularly in medicine. The rigorous study of muscle originated during the 17th-century scientific revolution, when figures like Giovanni Alfonso Borelli and Niels Stensen first recognized the relationship between skeletal muscle structure and force output. Our contemporary understanding encompasses key principles such as the influence of fiber length on muscle excursion and velocity, as well as the functional implications of pennate fiber arrangements. Nonetheless, several important aspects remain insufficiently characterized. In particular, the three-dimensional deformation of muscle fibers during dynamic movement is not yet fully resolved. In the domain of smooth muscle, notable progress has been made in describing its complex mechanical behavior, including nonlinear stress responses, viscoelasticity, and adaptation. However, experimental approaches frequently rely on simplified uniaxial testing, which does not accurately reflect in vivo behavior. Additionally, the impact of smooth muscle length adaptation on testing protocols remains unclear, and the structural and functional heterogeneity of the stomach continues to pose challenges for computational modeling. This thesis was funded by the Deutsche Forschungsgemeinschaft (DFG) under grant SI841/13-1 and addresses three principal research areas: A. Skeletal muscle architecture, B. Constitutive properties of smooth muscle tissue, and C. Mechanical heterogeneity and anisotropy of the stomach. Across nine individual contributions, the thesis investigates the following seven research questions: Skeletal muscle architecture A1. How does muscle architecture adapt during muscle lengthening? A2. How does muscle architecture compare between in situ and isolated conditions? A3. How does muscle architecture adapt throughout the growth process? Constitutive properties of smooth muscle tissue B1. How does the stress-stretch response of urinary smooth muscle compare between uniaxial and biaxial test modes? B2. How can reproducible results be obtained in repeated tensile tests of smooth muscle tissue? Mechanical heterogeneity and anisotropy of the stomach C1. How does stomach wall thickness vary locally? C2. What are the local strain patterns in the stomach wall during passive filling? To address these questions, a range of experimental methodologies was employed. Skeletal muscle architecture was investigated by manually digitizing fiber paths in rabbit calf muscles using a Microscribe MLX. The passive and active mechanical responses of porcine urinary smooth muscle tissue were analyzed through biaxial tensile testing with a custom-built device, and length adaptation was studied via uniaxial tests using an Aurora Scientific 305C-LR. For the stomach, local wall thickness was measured directly, and strain distributions were assessed through optical, marker-based analysis (VICON Motus) during in vitro inflation tests. The research yielded a number of significant findings regarding the structural and mechanical characteristics of muscular tissue. In skeletal muscle, length changes were found to induce compartment-specific alterations in the architecture of the rabbit M. gastrocnemius lateralis. Furthermore, muscle growth during maturation was shown to involve complex architectural remodeling rather than uniform scaling. With respect to smooth muscle, substantial differences in optimal stretch - though not stress - were observed between uniaxial and biaxial testing of urinary bladder tissue. Additionally, it was demonstrated that isometric contractions at reference length can reverse effects of length adaptation. In the stomach, pronounced regional differences were identified in the thickness of muscle and mucosal layers, along with heterogeneous and anisotropic strain patterns during passive inflation. Collectively, these results contribute to a more detailed understanding of the functional specialization and adaptive behavior of muscular tissues. The compartment-specific modifications observed in the M. gastrocnemius lateralis suggest a previously underappreciated level of functional differentiation within individual muscles. The architectural changes associated with growth appear to favor energy storage in the tendon and a reduction of the muscle’s rotational inertia with respect to the knee joint. In smooth muscle, the discrepancy between uniaxial and biaxial results indicates that the bladder may operate closer to its optimal stress in vivo than would be predicted from conventional uniaxial test results. Finally, the complex mechanical behavior of the stomach wall, including its anisotropy and regional thickness variation, reflects its functional compartmentalization and provides essential data for the development of accurate computational models

Modelling and experimental characterization of double layer InP/AlGaInP quantum dot laser

Spectrum of an InP/AlGaInP self- assembled double-layer quantum dot (QD) laser fabricated by metal-organic vapor-phase epitaxy is theoretically and experimentally investigated. A bimodal QD size distribution (small and large QD groups) was detected which is formed during the fabrication. A model is proposed based on rate equations accounting for the superposition of two inhomogeneous QD groups. The total output power and the power spectral density (PSD) of the fabricated QD laser are experimentally characterized at room temperature. The output spectrum is segmented into the sum of two Gaussians curves (super Gaussian) belonging to the small and large QD groups. The peak PSD and the spectral width of each group are extracted and their dependency on the injected current density is analysed. The peak of the large QDs is found to be dominant at small current while the peak of the small QDs dominated at high current alongside a reduction in its spectral width leading to lasing based on them. This behaviour is attributed to the saturation of the large QDs energy levels due to its relatively long radiative lifetime. The experimental analysis is in a good agreement with the theoretical results.The Science, Technology & Innovation Funding Authority (STDF

Making und Computational Thinking in der frühkindlichen Bildung - ein Praxisbericht zum Entwicklungs- und Forschungsprojekt MakeTechEarly (MTE)

Der Praxisbericht stellt die im Projekt MTE entwickelten 12 Lernarrangements zu den Themen Making und Computational Thinking (Schwerpunkt Problemlösen) vor. Diese wurden in enger Zusammenarbeit zwischen der Universität Stuttgart und Expert:innen der frühkindlichen Bildung entwickelt und in einem sogenannten „natürlichen Setting“ (Lye & Koh, 2014) erprobt. Die in MTE generierten (ersten) empirischen Ergebnisse belegen eine Wirksamkeit der Interventionsmaßnahme auf die CT-Fähigkeiten der beteiligten Vorschulkinder (N = 138) hinsichtlich der inhaltsbezogenen und prozessbezogenen Kompetenzen sowie die positiven technologischen Verhaltensweisen im Kontext der Lernarrangements zu Making. Trotz der Befundlage sind methodische und strukturelle Limitationen in der Interpretation zu beachten. Die Evaluation stützt sich auf eine relativ kleine und selektive Auswahl von interessierten Erzieher:innen an zehn Kindertagesstätten. Die externe Generalisierbarkeit der Befunde bleibt daher aufgrund einer möglichen Positivauswahl begrenzt. Weitere Einschränkungen resultieren aus unvollständigen Datenerhebungen bei Kindern (bedingt z. B. durch Krankheit der Kinder). Die Befunde sind an das spezifische Setting, die gewählten Zukunftsfähigkeiten und die involvierten Partnerinstitutionen gebunden. Dennoch lassen sich zentrale Gelingensbedingungen und Erfolgsfaktoren identifizieren, die als Referenz für vergleichbare Initiativen in der frühen Bildung dienen können. Insgesamt beeinträchtigen diese Limitationen zwar die Reichweite der Befunde, schmälern jedoch nicht die grundsätzliche Aussagekraft der Evaluation im Hinblick auf die Wirksamkeit der Interventionen an den beteiligten Kindertagesstätten. Unter Berücksichtigung der limitierenden Aspekte belegen die Studienergebnisse positive Wirkungseffekte auf das Wissen und die Fähigkeiten zu Making und Computational Thinking bei Vorschulkindern. Die quantitativen Ergebnisse zur gemessenen Wirkung werden durch die teilnehmenden Beobachtungen in den Kindertagesstätten untermauert. Die Befunde zeigen darüber hinaus auch auf, dass bereits in der frühkindlichen Bildung im Kontext der individuell realisierten Lehr und Lernarrangements Zukunftsfähigkeiten durch die Erzieher:innen kompetenzorientiert entwickelt werden können

Nanoalignment by critical Casimir torques

The manipulation of microscopic objects requires precise and controllable forces and torques. Recent advances have led to the use of critical Casimir forces as a powerful tool, which can be finely tuned through the temperature of the environment and the chemical properties of the involved objects. For example, these forces have been used to self-organize ensembles of particles and to counteract stiction caused by Casimir-Liftshitz forces. However, until now, the potential of critical Casimir torques has been largely unexplored. Here, we demonstrate that critical Casimir torques can efficiently control the alignment of microscopic objects on nanopatterned substrates. We show experimentally and corroborate with theoretical calculations and Monte Carlo simulations that circular patterns on a substrate can stabilize the position and orientation of microscopic disks. By making the patterns elliptical, such microdisks can be subject to a torque which flips them upright while simultaneously allowing for more accurate control of the microdisk position. More complex patterns can selectively trap 2D-chiral particles and generate particle motion similar to non-equilibrium Brownian ratchets. These findings provide new opportunities for nanotechnological applications requiring precise positioning and orientation of microscopic objects.Horizon Europe ERC Consolidator Grant MAPEIPolish National Science Cente

Process development methods in microtechnology and the associated process environment

Microsystem technology (MST) and micro-electro-mechanical systems (MEMS) are key technologies that continually introduce new application opportunities. Increasing complexity and individualization require systematic process development to avoid errors and delays. While existing methods for process development address various aspects of the manufacturing process, the systematic consideration of external factors influencing the process environment (PEnv) remains broadly inadequate. Despite extensive standards, PEnv-related influences lead to quality fluctuations in practice. A list of influencing factors and an example process illustrate these challenges. This study aims to analyze which methods exist for process development in MST and to what extent they systematically consider process environmental factors. A mixed methods design was used for the analysis. In a systematic literature review (SLR) using traditional databases and Artificial intelligence-supported search tools, a total of 75 relevant studies from the years 2005 to 2024 were identified. The methods that cover various aspects of process development are presented in an overview. An adapted GRADE (Grading of Recommendations Assessment, Development, and Evaluation) analysis was used to check the extent to which the PEnv can be included in process development using the methods currently available. The results show that existing approaches often take PEnv into account insufficiently. Efficient consideration with the use of current methods requires extensive expert knowledge, knowledge management, and project-specific supplementary methods. This study emphasizes the need for research into methods that systematically integrate environmental requirements into process development to improve the efficiency and quality of MST manufacturing in this area

Automation of customizable library preparation for next-generation sequencing into an open microfluidic platform

Next-generation sequencing (NGS) is becoming more relevant for medical diagnostics, especially for using cell-free DNA to monitor response to therapy in cancer management, as high sensitivity of NGS enables detection of rare events. Sequencing Library preparation is a time-consuming and complex process, and large-scale liquid handlers are often used for automation. However, for smaller labs and low-to-medium throughput samples, these liquid handlers are expensive and need experts for handling. This work presents a proof-of-concept for library preparation on a commercially available and open lab-on-a-chip platform, which provides an alternative automation for low-to-medium throughput requirements. It covers common library preparation steps optimized to a microfluidic environment that include customizable PCR for target enrichment, end-repair, adapter ligation, nucleic acid purification via magnetic beads, and an integrated quantification step. The functionality of the cartridge is demonstrated with reference cfDNA containing different allelic frequencies of seven known mutations. Processing the samples in the cartridge reveals highly comparable results to manual processing (Pearson r = 0.94) based on amplicon sequencing. Summarized, the proposed automated lab-on-a-chip workflow for customizable library preparation could further pave the way for NGS to evolve from a technology used for research purposes to one that is applied in routine cancer management

Development of a deployment platform for ONNX models

Artificial Intelligence models and specifically Machine Learning models are experiencing increasing adoption in various fields and domains. Consequentially the demand for efficient deployment solutions is becoming urgent. Ensuring seamless model management, reliable deployment and fast inference remains a key challenge. This work presents a solution to the mentioned problem. The solution is a platform for ONNX model deployment, providing a streamlined approach to model versioning, metadata management, and inference execution. To enable the efficient model file storage and their associated metadata, the platform leverages MongoDB alongside GridFS. Additionally the platform manages model versioning, where each model version is stored as a seperate entry, enabling multiple versions of a model to exist without having to delete previous versions. Deployment and inference are tested using performance metrics, like resource utilization and speed. Usability and robustness though are evaluated through structured test cases and user feedback. All in all the goal is to develop a prototype of the platform quickly utilizing rapid prototyping, while iteratively evaluating it with the help of design science. Deployment results indicate efficient resource utilization and rapid inference, with challenges in scalability, especially for large models. Usability testing confirms an intuitive interface, ease of use and general user satisfaction. Robustness testing shows that the platform handles unexpected scenarios effectively without failures, while remaining operable and avoiding complete crashes. Finally the platform successfully addresses ONNX model deployment challenges, while maintaining ease of use, even for non-technical users. Future enhancements could include enhanced model versioning, inference optimizations and integration with external platforms

Propädeutik der Technikwissenschaften : Doktorandenseminar: Wissenschaftstheorie der Technikwissenschaften

Technikwissenschaften im Wissenschaftssystem Vom Forschungsprozess zur Gliederung: Forschungsreise Technikwissenschaftliche Erkenntnis: Begriff & Hypothese Modelltheorie und Systemtheorie Forschungsfrage und Themenfindung Evaluation der Zielerreichung: Verifikation & Validierung Wissenschaftstheoretische Positionierun