On the Properties of Self-Thermophoretic Janus Particles: From Hot Brownian Motion to Motility Landscapes

This thesis investigates several phenomena that are associated with (self-)thermophoretic Janus particles with hemispheres made from different materials serving as a paradigm for active propul- sion on the microscale. (i) The dynamics of a single Janus sphere in the external temperature field created by an immobilized heat source is studied. I show that the particle’s angular velocity is solely determined by the temperature profile on the equator between the Janus particle’s hemispheres and their phoretic mobility contrast. (ii) The distinct polarization-density patterns observed for active-particle suspensions in activity landscapes are addressed. The results of my approximate theoretical model agree well with exact numerical and measurement data for a thermophoretic microswimmer, and can serve as a template for more complex applications. The essential physics behind the formal results is robustly captured and elucidated by a schematic two-species “run- and-tumble” model. (iii) I investigate coarse-grained models of suspended self-thermo- phoretic microswimmers. Starting from atomistic molecular dynamics simulations, the coarse-grained de- scription of the fluid in terms of a local molecular temperature field is verified, and effective nonequilibrium temperatures characterizing the particle’s so called hot Brownian motion are mea- sured from simulations. They are theoretically shown to remain relevant for any further spatial coarse-graining towards a hydrodynamic description of the entire suspension as a homogeneous complex fluid.In dieser Arbeit untersuche ich mehrere Phänomene, die im Zusammenhang mit (selbst-)thermo- phoretischen Janusteilchen auftreten. Diese Teilchen bestehen aus zwei Halbkugeln mit unter- schiedlichen Materialeigenschaften und dienen in dieser Arbeit als Musterbeispiel für aktive Fort- bewegung auf der Mikroskala. (i) Die Dynamik eines einzelnen Janusteilchens im externen Temper- aturfeld einer ortsfesten Heizquelle wird untersucht. Es wird gezeigt, dass die Winkelgeschwindigkeit des Teilchens ausschließlich durch das Temperaturprofil am Äquator zwischen den Hemisphären des Janusteilchens und dem Unterschied ihrer phoretischen Mobilitäten bestimmt wird. (ii) Ich befasse mich mit den charakteristischen Polarisations- und Dichteprofilen, die für aktive Teilchen in Aktivitätslandschaften beobachtet werden. Die Ergebnisse meines approximativen theoretis- chen Modells stimmen gut mit exakten numerischen Lösungen und Messdaten für einen ther- mophoretischen Mikroschwimmer überein und können als Vorlage für komplexere Anwendungen dienen. Die wesentliche Physik hinter den formalen Ergebnissen wird durch ein schematisches Zwei-Spezies-“Run-and-Tumble”-Modell erfasst und erklärt. (iii) Ich untersuche Coarse-Graining- Modelle von suspendierten selbst-thermophoretischen Mikroschwimmern. Ausgehend von atom- istischen molekulardynamischen Simulationen wird die grobkörnige (coarse-grained) Beschreibung des Fluids in Form eines lokalen molekularen Temperaturfeldes verifiziert. Anschließend berechne ich effektive Nichtgleichgewichtstemperaturen, die die sogenannte heiße Brownsche Bewegung der Teilchen charakterisieren, und vergleiche diese mit Simulationsdaten. Es wird gezeigt, dass diese effektiven Temperaturen für jede weitere räumliche Vergröberung hin zu einer hydrodynamischen Beschreibung der gesamten Suspension als homogenes komplexes Fluid relevant bleiben

A literature review

Introduction: In recent years, inter-organisational collaboration between healthcare organisations has become of increasingly vital importance in order to improve the integration of health service delivery. However, different barriers reported in academic literature seem to hinder the formation and development of such collaboration. Theory and methods: This systematic literature review of forty studies summarises and categorises the barriers to integrated care in inter-organisational settings as reported in previous studies. It analyses how these barriers operate. Results: Within these studies, twenty types of barriers have been identified and then categorised in six groups (barriers related to administration and regulation, barriers related to funding, barriers related to the inter-organisational domain, barriers related to the organisational domain, barriers related to service delivery, and barriers related to clinical practices). Not all of these barriers emerge passively, some are set up intentionally. They are not only context-specific, but are also often related and influence each other. Discussion and conclusion: The compilation of these results allows for a better understanding of the characteristics and reasons for the occurrence of barriers that impede collaboration aiming for the integration of care, not only for researchers but also for practitioners. It can help to explain and counteract the slow progress and limited efficiency and effectiveness of some of the inter-organisational collaboration in healthcare settings

Resourcing Goal-directed Networks: Toward A Practice-based Perspective

This paper proposes a practice-based perspective on how managers resource goal-directed networks in the public sector, especially those governed by a network administrative organization. While previous literature shows that network managers need to acquire and allocate resources in order to achieve network goals, little is known about specific resourcing practices and related challenges to resourcing goal-directed networks. To shed light on these issues, we outline a processual, multilevel, network-centric perspective that focuses on network resourcing practices and takes their interplay with network rules and goals into account. This paper shows that, to attain network goals, network managers need to mitigate developing tensions arising from the different interests of network members, external stakeholders, and the network itself, while navigating a trajectory of network resourcing. The paper contributes to the literature on public networks by examining potential sources of network-level resources; outlining basic resourcing practices of controlling, producing, reproducing, and transforming such resources; discussing multilevel tensions around network resourcing; and exploring trajectories of network resourcing. In addition, we propose avenues for empirical research on network resourcing

Insights from a discourse analysis of German tweets until contacts were banned in March 2020

This essay examines how different individual and collective actors interpreted the initial weeks of the worldwide COVID-19 outbreak from the German perspective. During this early phase, knowledge about COVID-19 was quite limited and uncertain, which also influenced the ability to assess (potential) impacts. The analysis relies on twitter data and traces the main arguments in the public German discourse between January and March 2020. It shows that actors ascribed different meanings to the outbreak – either recognizing or negating the gravity of the COVID-19 threat. Shortly before the first German lockdown, the seriousness of the COVID-19 threat had begun to feature prominently within the public discourse

Gendered publication patterns in Socio-Economic Review

Creating interdisciplinary dialog in the field of socio-economics cannot be separated from the social diversity among scholarly voices within its community. In marking the 20th anniversary year of Socio-Economic Review (SER), this article examines the role of gender among authors and reviewers in SER. Our findings show that women remain underrepresented in terms of authorship and reviewing. While no gender differences exist in overall acceptance rates for submitted papers, a substantial gender gap exists in the number of submissions. Our analysis also highlights how the persistence of gender segregation is related to the predominance of male-only author teams and male-dominated research topics. The article concludes with suggestions for further research and a discussion on gender disparities in socio-economics and other social science fields

A longitudinal case study on business model innovation for improving care in complex neurological diseases

Multi-sided platforms in healthcare often focus their business model on standardizing care for wide-spread, chronic diseases. However, there is a lack of knowledge surrounding platform business models enabling individualized care coordination for patients with rare diseases. This paper analyses the development of a complex platform business model addressing Amyotrophic Lateral Sclerosis, a severe neurological disease that requires the coordination of a diverse network of medical specialists, care, and equipment providers. A longitudinal case study examines the platform’s development, focusing subsequently on qualitative and efficient care coordination, care research, and active and direct involvement of patients, as well as establishing two business models, namely, care coordination and care research. We reconstruct how these complex platform business models were configured to improve patient care and care research, thereby creating immediate value for patients and insights for long-term care improvements. The ongoing platform development carefully balances value generation for diverse stakeholders and economic sustainability

Coarse Graining Nonisothermal Microswimmer Suspensions

We investigate coarse-grained models of suspended self-thermophoretic microswimmers. Upon heating, the Janus spheres, with hemispheres made of different materials, induce a heterogeneous local solvent temperature that causes the self-phoretic particle propulsion. Starting from molecular dynamics simulations that schematically resolve the molecular composition of the solvent and the microswimmer, we verify the coarse-grained description of the fluid in terms of a local molecular temperature field, and its role for the particle’s thermophoretic self-propulsion and hot Brownian motion. The latter is governed by effective nonequilibrium temperatures, which are measured from simulations by confining the particle position and orientation. They are theoretically shown to remain relevant for any further spatial coarse-graining towards a hydrodynamic description of the entire suspension as a homogeneous complex fluid