University of Konstanz
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Stress transmission in social groups of mice : Unveiling physiological responses, behavioral patterns, and immune dynamics
No full textIn modern societies, stress is pervasive, requiring sophisticated physiological mechanisms for stability and survival, primarily through the sympatho-adrenal medullary (SAM) and hypothalamo-pituitary adrenal (HPA) axes. Chronic stress is linked to a range of mental and physical health problems and has been shown to affect immune function.
In this study, a paradigm for social stress transmission in groups of mice was established, based on a restraint stress model to study how stress spreads among individuals. Mice exposed to indirect stress exhibited HPA-axis activation, elevated corticosterone (CORT) levels, enlarged adrenal glands, and anxiety-like behaviors in light-dark-box tests. Notably, female mice were more susceptible to stress transmission. While stress transmission enhanced innate immune responses, it did not affect adaptive immunity following vaccination with a PLGA-based vaccine. In contrast, direct stress impaired both immune responses and the effectiveness of immunotherapy in a melanoma model.publishe
Molecular mechanisms of aberrant remodelling in the pathogenesis of idiopathic pulmonary fibrosis
No full textDisruptions in tissue homeostasis and aberrant cell fate decisions are fundamental for the development of many chronic diseases, giving rise to a complex landscape of pathological changes. In the context of persistent injury conditions, such as those seen in idiopathic pulmonary fibrosis (IPF), cells have to adapt to a new equilibrium, often leading to aberrant remodelling and maladaptive cellular behaviours. Understanding these fundamental processes and underlying molecular mechanisms is crucial for unravelling the pathogenesis of IPF and exploring new research paths to ultimately identify therapeutic strategies for repair and regeneration of the fibrotic lung. Therefore, the present research aimed to explore key mechanisms governing aberrant cell fate decisions in IPF. Central to these findings is the role of aberrant epithelial remodelling, a process that has long remained a mystery. By leveraging a patient-derived 3D distal AO model, key IPF features, including the appearance of aberrant KRT5+ basal cells, were mimicked and found to be inducible within this model. Deeper characterisation of these aberrant basal cells revealed a metabolic alteration towards elevated O-linked β-N-acetylglucosamine (O-GlcNAc) levels and increased chromatin accessibility, particularly at promoter regions of metabolic and fibrotic genes with a JUNB motif. Combining these findings, an important role of O-GlcNAcylation of JUNB on its function was detected, fostering a profibrotic response to persistent injury, ultimately leading to aberrant epithelial remodelling. Importantly, perturbation of O-GlcNAc sites on JUNB mitigates the aberrant differentiation of basal cells and leads to a disruption of the fibrotic cell fate in general, eventually aiding in the restoration of homeostasis in the lung, specifically the alveolar lineage. This novel connection between metabolic dysregulation being transduced into chromatin alterations via the O-GlcNAc-JUNB-axis not only emphasises the importance for future investigations in the consequences of metabolic dysregulation in IPF but also opens up new avenues for therapeutic strategies to combat this fatal disease.publishe
Silizium-Halbleitertechnologie für Quantencomputer : Quantenrechnen mit Spins
No full textHalbleiter-Spinqubits gelten als vielversprechende Kandidaten für die Recheneinheit eines Quantencomputers. Um ein Spinqubit zu realisieren, wird ein einzelner Ladungsträger, ein Elektron oder ein Ladungsträgerloch, in einem Quantenpunkt eingefangen. Dort sind ihre Spins über lokal erzeugte Magnetfelder zwischen zwei Zuständen 0 und 1 kontrollierbar. Auf Basis solcher Quantenpunkte gestatten die etablierten Fabrikationstechniken der Halbleiterindustrie eine präzise und skalierbare Herstellung von Quantenprozessoren. Sowohl Ein-Qubit-Gatter als auch Zwei-Qubit-Gatter mit Spinqubits operieren mit hoher Genauigkeit und ermöglichen so universelles Quantenrechnen. Wichtig sind dabei ihre hohen Lebensdauern im Bereich von Mikrosekunden bis sogar Sekunden. Die Anzahl an Spinqubits auf einem Chip ist besonders in den letzten Jahren gewachsen. Die Möglichkeit, Spinqubits auf verschiedene Weisen miteinander zu koppeln, erlaubt auch langreichweitige Operationen zwischen verschiedenen Registern. Es gilt, Korrelationseffekte zwischen Spinqubits und ihrer Umgebung noch besser zu verstehen und die Verdrahtung auf dem Chip zu optimieren, um so den Weg zu einem halbleiterbasierten Quantencomputer zu ebnen.publishe
Electro-optic sampling of classical and quantum light
No full textFull characterization of electric-field waveforms in amplitude and phase is achieved across the terahertz to visible spectral range through interaction with an optical pulse shorter than a half-cycle period via the Pockels (linear electro-optic) effect. This technique of electro-optic sampling has become an indispensable tool in various areas, including ultrafast pump-probe, time-domain and frequency-comb spectroscopies, quantum optics, high-harmonic generation, and attosecond science, and holds great promise for further advances. Not only does it enable spectroscopic measurements with record dynamic range and temporal resolution, along with massively parallel real-time spectral data acquisition, but its remarkable sensitivity also allows the detection of vacuum fluctuations, i.e., “zero-point motion” of electric fields, profoundly impacting our understanding of the fundamental laws of nature.publishe
On Greedy Reconstruction Algorithms
No full textThis thesis is devoted to the development and analysis of greedy reconstruction (GR) algorithms. These procedures allow the design of optimized control functions that facilitate the accurate and efficient identification of unknown operators in dynamical systems. The approach is based on an offline/online decomposition of the reconstruction process, and on an ansatz for the unknown operator defined by a given family of operators.
The first part of this thesis focuses on linear dynamical systems. A detailed analysis demonstrates that the controls computed by the GR algorithm make the quadratic online reconstruction problem strictly convex. Based on these results, an optimized greedy strategy (OGR) is introduced that additionally optimizes the ansatz for the unknown operator.
In the second part, more general nonlinear systems are considered. Based on the linearization of these systems, a new greedy algorithm (LGR) is developed. It is shown that the controls computed by LGR lead to the local convergence of the classical Gauss-Newton method applied to the nonlinear online reconstruction problem. This result is extended to the controls obtained by the original GR algorithm applied directly to the nonlinear system. Numerical experiments on dynamical systems with linear and bilinear control structures confirm the effectiveness of the greedy algorithms.
The third part of this thesis considers the reconstruction of a non-trivial joint probability distribution for two Hamiltonian parameters in Nuclear Magnetic Resonance. While the corresponding spin dynamics can be represented by a bilinear dynamical system, the online reconstruction problem is fully quadratic. A rigorous analysis proves that the controls generated by the GR algorithm ensure strict convexity of this reconstruction problem. These findings are confirmed by numerical experiments that highlight the efficiency of the OGR algorithm.
In the final part of this work, the GR algorithms are applied to general function approximation problems. In the case of polynomial interpolation, the original GR algorithm is shown to compute exactly the (tensor-product) Leja points. Additionally, an equivalence between OGR and the well-established Empirical Interpolation Method is revealed. Finally, a new class of greedy algorithms is developed, that aim to select the smallest subset of a given data set, while simultaneously optimizing the structure of the approximation ansatz, within a given family of approximation functions. Extensive numerical tests on function approximation by neural networks demonstrate the efficiency of the new algorithms.publishe
Singlet, Doublet, and Triplet Emissions of Diarylamine-Modified Bismuth Pincer Complexes
No full textpublishe
"I know that I can help the person and that is priceless to me" : a qualitative study on tasks and experiences of peers in mental healthcare for refugees
No full textBackground. Numerous barriers prevent refugees from accessing indicated psychotherapy in the German healthcare system. Peer support emerges as a potential key element to overcome utilization barriers for refugees in the future. Since 2017, the pilot project "Coordinated Psychotherapeutic Treatment with the Involvement of Peer Support Workers" (COPEER) has been developed and implemented and is currently being evaluated. In COPEER, supervised, but autonomously acting peer support workers (PSWs) accompany and support refugees with mental disorders in the healthcare system.
Objective: This study focuses on the qualitative description of the PSWs' work reality and their positive and negative work-related experiences in COPEER to assess the feasibility and relevance of their role.
Method: An exploratory and qualitative approach with purposive sampling was chosen; face-to-face expert interviews were conducted using a semi-structured guide with 8 PSWs (3 women, 5 men; age M = 43 years). The evaluation was carried out using Mayering's Qualitative Content Analysis. Five main task areas within the work reality of PSWs could be identified: organization, physical accompaniment, cultural mediation, motivation and emotional support. PSWs reported both positive and negative work-related experiences, with positive aspects being mentioned more frequently, such as high meaningfulness and a personal learning process. Negative experiences were often encountered during the initial phase of their work, e.g., problems managing the professional relationship. The mandatory continuous supervision provided by COPEER was described as helpful. PSWs take on important tasks that actively help to overcome central barriers to the regular health care system for refugees. In doing so, they experience both negative and positive aspects. Training and regular supervision appear to be crucial to successfully cope with work-related demands. In sum, the results show that a peer approach, as implemented in COPEER, can help to overcome barriers and enable equal access to mental health care for a particularly disadvantaged patient group.publishe
Active Matter under static and dynamic confinement
No full textThis thesis presents an experimental investigation of active matter under confinement. The experiments build on an established platform that allows individual control over the motion of suspended microscopic particles by using an optical feedback control setup. Here, we extend this setup to generate arbitrary-shaped light-induced effective potential landscapes that constrain the motion of these self-propelled microparticles.
This provides a versatile model system for exploring how geometric boundaries and confinement affect the collective dynamics and emergent behavior in active matter. We detail the implementation of our technique and characterize the motion of the self-propelled microparticles and their interaction with the repulsive boundaries through benchmark measurements. Furthermore, we employ our experimental model to investigate active matter under both static and dynamic confinement in three distinct situations.
First, we confine active particles in narrow, soft channels and examine how this influences motility induced cluster formation. We find a novel reentrant behavior regarding cluster formation as a function of particle velocity and strength of confinement. Second, we study the flow of active particles through bottleneck constrictions and examine the mechanisms leading to clogging. We find that clogging is due to arch-formation as known from granular matter up to a threshold value of interparticle attraction, above which clogging is governed by cohesive droplets. Third, we perform indirect measurements of the force on a beating, flagellum-shaped object moving through a suspension of active matter. We demonstrate that slow object motion promotes the accumulation of active particles at its rear, leading to a notable reduction in drag force. A similar phenomenon is known as active thinning.
These studies are corroborated by coarse analytical models and computer simulations aligning overall well with the experimental results, indicating that the observed phenomena are rather generic features occurring in various realizations of active matter systems. All in all, our results sustain the rapidly evolving research field of active matter in complex environments and highlight the importance of considering boundary effects when designing microfluidic devices or micromachines that are intended to operate with or within active matter.
BEINHALTET EINE DEUTSCHSPRACHIGE ZUSAMMENFASSUNGpublishe
