The investigation of the response of the immune system, which is influenced by the communication between cells of the same as well as different species (interkingdom signalling), is a crucial part in biomedical research. Especially the sensing of signalling molecules that are produced by bacteria can induce a response of eukaryotic cells present in the immune system. For the studies of cellular response in vitro, the extracellular matrix (ECM), which surrounds the cells in their natural environment, needs to be simulated. The creation of an artificial three-dimensional (3D) environment is essential and affects the cell adhesion, proliferation as well as migration. Thereby, the cell detachment and separation can be induced. In this Thesis, different approaches to generate suitable cell culture platforms were explored and their suitability for future work in cell communication investigated. In particular, polymer brushes as well as lipid bilayers were examined as approaches to spatially and temporally control selective cell attachment and detachment. Furthermore, hydrogel-based scaffolds were prepared and investigated regarding their suitability to create viable environments for cell encapsulation. Thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) brushes were successfully used for selective separation of human umbilical vein endothelial cells (HUVEC) from a coculture with macrophages without the use of additional compounds, such as releasing agents or antibodies. The decrease of the temperature below the transition temperature of 35 °C for (5 ± 1) nm thin PDEGMA brushes, resulted in a change of the chain conformation and thus cause a desorption of cell adhesion proteins. HUVECs and macrophages attached and spread in a coculture on (5 ± 1) nm thin PDEGMA brushes at 37 °C. In contrast to macrophages HUVECs, which possess a lower adhesion strength, detached from the brushˈ surface after decreasing the temperature to 22 °C. HUVECs could be reseeded on a new surface with a yield of 71 % and a purity of almost 100 %. Square-shaped, patterned polymeric lipid bilayers that were modified with PDEGMA and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) brushes with brush thicknesses of 26 nm and 20 nm, respectively, were investigated in terms of selective cell attachment. Mouse fibroblasts (NIH 3T3) cells were able to attach and spread on polymeric lipid bilayer. In contrast, polymer brushes possess cell repulsive properties, so that the cells are only able to attach on bare glass squares. The use of patterned polymeric lipid bilayers, which are modified with polymer brushes, allows a selective cell attachment. The adhesion and spreading of cells inside different hydrogels with various geometries were investigated. The encapsulation of NIH 3T3 cells and pancreatic tumor cells (PaTu 8988t) inside chitosan microbeads cross-linked with glycerol phosphate disodium salt (CS + GP) as well as inside alginate — fibrin microbeads were not successful due to the too harsh conditions of the gelling bath and the lack of cell adhesion properties, respectively. However, a hydrogel consisting of alginate dialdehyde (ADA) with a degree of oxidation of 30 % and gelatine modified with carbohydrazide (GelCHD) in a ratio of 1 : 3 were shown to be useful, afford attachment, spreading, and proliferation of encapsulated cells. Finally, the response of encapsulated NIH 3T3 cells, in the above-mentioned hydrogel, to the signalling molecule N-(3-oxododecanoyl)-L-homoserine lactone (HSL) was examined. A pronounced decrease of the cellsˈ viability from 90 % to 71 % and an increase in the intracellular Ca2+ concentration was detected after treatment with HSL, confirming a response of the cells on the signal molecules. Overall, the results reported in this Thesis highlight the potential of polymer brushes, lipid bilayers as well as hydrogel scaffolds for the encapsulation of cells and the investigation of cellular communication processes.

Missing data in public health present challenges for evidence-based research. While convenient missing data handling methods like complete-case analysis or single imputation have a strong tendency to produce biased parameter estimates, Multiple Imputation by Chained Equations (MICE) provides a more appropriate approach but struggles with statistical complexities such as non-linearity in health data. Ensemble learning methods like random forest and XGBoost offer greater flexibility for multiple imputation (MI). Particularly multiple Imputation through XGBoost (Mixgb) is a recent development that promises to transfer the strong performance of XGBoost to missing data challenges. This thesis evaluates three traditional methods (complete-case analysis, mean-mode-median imputation, MICE) alongside two ensemble algorithms for MI (MICE-ranger, Mixgb) through a simulation study recreating complex health data sets. Eight missing data scenarios combine Missing At Random (MAR) or Missing Not At Random (MNAR) mechanisms with missing data proportions of 10%, 20%, 30%, or 40%. Statistical complexities including non-linearity, interactions, conditional heteroskedasticity, class imbalance, and noise were incorporated. Methods were assessed on bias, confidence interval width, coverage, and a composite performance score, then applied to real-world health data. Results indicate Mixgb is, on average, the most robust method across all scenarios, demonstrating the least bias and consistently good coverage. MICE-ranger performed better than MICE but worse than Mixgb. Real-world data analysis showed all MI methods generated proper imputations for low-to-moderate missing data proportions, though significant differences in single parameter estimates occurred between methods, underscoring the need to consider different MI methods to handle missing data. These findings suggest ensemble learning methods, particularly Mixgb, offer superior performance compared to linear methods like MICE for complex missing data scenarios. Given the heterogeneous nature of public health data, researchers should consider ensemble methods for MI as robust solutions for missing data challenges, without neglecting MICE as a possible solution to more linear missing data scenarios.

Juan S. Guse’s “Tausendmal so viel Geld wie jetzt” (2025) presents a striking paradox: while its paratextual elements suggest a research-based text, the publisher S. Fischer categorizes it as fiction. Read against the backdrop of the “New Journalism” movement that emerged in the United States in the 1960s, the work blurs the boundaries between fact and fiction. As in his previous novels “Lärm und Wälder” and “Miami Punk,” Guse draws on and disrupts established genre traditions. Through literary techniques that immerse readers in the worlds of his protagonists, he seeks not merely to present facts but to “stage authenticity.” At the same time, this mode of writing functions as a diagnostic tool for our present: through the example of the crypto industry, Guse renders perceptible a world in which fact and fiction can no longer be clearly separated – an indistinction that itself becomes legible as a narrative principle within the text.

With digitization, consumer practices have changed significantly. Consumers no longer need to enter stores physically, but this has also shifted how they express their consumption preferences and, thus, their social status. Individuals can express their lifestyle choices more prominently on social networks than ever. The digital goods we consume also represent a form of lifestyle expression and transfer meanings. These goods no longer need a tangible form; instead, they can take hybrid forms and be experienced physically in different ways. Therefore, this thesis will investigate the role of consumers’ agency in technological transformations and how they negotiate the constitution of social norms and practices. It examines various phenomena to explore how this negotiation process unfolds and its implications for the potential democratization of consumption through technology. Through the following four studies, I aim to critically reflect on democratization, social distinction, and the formation of practices and social norms of digital consumption and lifestyles: 1) Breaching the Social Order: An innovative card game method is introduced to explore breaches in digital privacy norms. This method provides insights into negotiating digital privacy “common sense” and the constitution of social order. 2) Digital Ownership beyond the Sharing Economy: This study investigates how consumers perceive digitally shared physical goods without “possessing” them. This phenomenon redefines the boundaries of sharing and challenges the concept of social distinction. 3) Digital Mediated Practices: This study presents the practice of digitally mediated wine tasting, which combines established and emerging consumption practices and raises questions about democratization and the senses. 4) Designing for Taste as a Social Practice: Using the case of a click-dummy taste app, this study explores how food consumption and taste are conceptualized as social practices within the field of digital consumption. Through these studies, I identify various practice elements that underlie the reproductive, transformative, and emergent dimensions of Digital Consumer Practices. Therefore, this work contributes to the heterogeneous research field and bridges the discourses of Consumer Culture Studies, Verbraucherinformatik as a discipline within Human-Computer Interaction (HCI), and Practice Theory.