Entwicklung und Charakterisierung von planaren amperometrischen Mikroelektroden unter Einsatz statischer und dynamischer Testverfahren

The increasing demand for chemical and biochemical sensors meets with strong requirements for sensor miniaturization and permanent lowering of costs. Thus, fabrication methods of the semiconductor industry attract manufacturers of chemical sensors. But the advantages of the silicon technologies fail to work, if no tools for waferlevel functional tests of transducers and sensors are available. Within this theses test methods for quality control of ultramicroelectrode-arrays (UMA) were evaluated, including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). Waferlevel tests of glucose sensors were also performed. It was shown, that EIS at very low frequencies in combination with UMA provide an easy and powerful tool for deriving standard rate constants even of very fast charge-transfer reactions. In addition, a single-chip potentiostat was chacacterized and its reliability was demonstrated. Besides the waferlevel yield the most important number in sensor technology is the assembly test yield (ATY). Within the theses a technology recipe for making backside contacts for silicon chips was developed, which promises an increase in ATY.Ein steigender Bedarf an chemischen und biochemischen Sensoren in Verbindung mit dem Streben nach Miniaturisierung und Kostendruck durch kurze Nutzungsdauern lassen den Einsatz von Technologien der Mikroelektronikfertigung mit seinen großen Potential an massenproduktionstauglichen Methoden attraktiv erscheinen. Die Vorteile der Siliziumtechnik werden jedoch nur dann voll wirksam, wenn neben der günstigen Herstellung auch Prüfwerkzeuge für den Funktionstest der Transducer und Sensoren noch auf Basis der unzerteilten Wafer zur Verfügung stehen. Der Validierung solcher Prüfmethoden widmet sich diese Dissertation, im Besonderen der Qualitätskontrolle an Ultramikroelektrodenarrays (UMA). Zur Bestimmung der charakteristischen Bauteilparameter wurden die elektroanalytischen Meßmethoden elektrochemische Impedanzspektroskopie (EIS), Cyclovoltammetrie (CV) und rasterelektrochemische Mikroskopie (SECM) untersucht. Der Übergang zu entsprechenden Fragestellungen beim vollständigen Sensor wurde am Beispiel Glukosesensor behandelt. Es ist zudem gezeigt worden, daß die EIS an UMA bei niederen Anregungsfrequenzen die verläßliche Bestimmung der Standardgeschwindigkeitskonstanten reversibler Redoxsysteme ermöglicht. Die untersuchten Prüfmethoden machen den Einsatz eines Potentiostaten erforderlich. In der vorliegenden Arbeit wurde ein Single-Chip Potentiostat charakterisiert und seine Zuverlässigkeit validiert und demonstriert. Neben der Ausbeutebestimmung beim Funktionstest auf Waferebene ist bei Sensoren die Ausbeute nach Assemblierung entscheidend. Im Rahmen der Dissertation wurde eine Rückseitenkontaktierung für Siliziumchips entwickelt, die eine deutliche Steigerung dieser Ausbeute verspricht. Dazu wurde mit dem anisotropen Rückseitenätzen ein Verfahren der Silizium-Mikromechanik eingesetzt

Perceived privacy risk in the Internet of Things: determinants, consequences, and contingencies in the case of connected cars

The Internet of Things (IoT) is permeating all areas of life. However, connected devices are associated with substantial risks to users’ privacy, as they rely on the collection and exploitation of personal data. The case of connected cars demonstrates that these risks may be more profound in the IoT than in extant contexts, as both a user's informational and physical space are intruded. We leverage this unique setting to collect rich context-immersive interview (n = 33) and large-scale survey data (n = 791). Our work extends prior theory by providing a better understanding of the formation of users’ privacy risk perceptions, the effect such perceptions have on users’ willingness to share data, and how these relationships in turn are affected by inter-individual differences in individuals’ regulatory focus, thinking style, and institutional trust

Privacy Risk Perceptions in the Connected Car Context

Connected car services are rapidly diffusing as they promise to significantly enhance the overall driving experience. Because they rely on the collection and exploitation of car data, however, such services are associated with significant privacy risks. Following guidelines on contextualized theorizing, this paper examines how individuals perceive these risks and how their privacy risk perceptions in turn influence their decision-making, i.e., their willingness to share car data with the car manufacturer or other service providers. We conducted a multi-method study, including interviews and a survey in Germany. We found that individuals’ level of perceived privacy risk is determined by their evaluation of the general likelihood of IS-specific threats and the belief of personal exposure to such threats. Two cognitive factors, need for cognition and institutional trust, are found to moderate the effect that perceived privacy risk has on individuals’ willingness to share car data in exchange for connected car services

Identification of Genes under Positive Selection Reveals Differences in Evolutionary Adaptation between Brown-Algal Species

Brown algae are an important taxonomic group in coastal ecosystems. The model brown algal species Ectocarpus siliculosus and Saccharina japonica are closely related lineages. Despite their close phylogenetic relationship, they vary greatly in morphology and physiology. To obtain further insights into the evolutionary forces driving divergence in brown algae, we analyzed 3,909 orthologs from both species to identify Genes Under Positive Selection (GUPS). About 12% of the orthologs in each species were considered to be under positive selection. Many GUPS are involved in membrane transport, regulation of homeostasis, and sexual reproduction in the small sporophyte of E. siliculosus, which is known to have a complex life cycle and to occupy a wide range of habitats. Genes involved in photosynthesis and cell division dominated the group of GUPS in the large kelp of S. japonica, which might explain why this alga has evolved the ability to grow very rapidly and to form some of the largest sporophytes. A significant number of molecular chaperones (e.g., heat-shock proteins) involved in stress responses were identified to be under positive selection in both species, potentially indicating their important roles for macroalgae to cope with the relatively variable environment of coastal ecosystems. Moreover, analysis of previously published microarray data of E. siliculosus showed that many GUPS in E. siliculosus were responsive to stress conditions, such as oxidative and hyposaline stress, whereas our RNA-seq data of S. japonica showed that GUPS in this species were most highly expressed in large sporophytes, which supports the suggestion that selection largely acts on different sets of genes in both marcoalgal species, potentially reflecting their adaptation to different ecological niches

Gli3 Controls Corpus Callosum Formation by Positioning Midline Guideposts During Telencephalic Patterning

The corpus callosum (CC) represents the major forebrain commissure connecting the 2 cerebral hemispheres. Midline crossing of callosal axons is controlled by several glial and neuronal guideposts specifically located along the callosal path, but it remains unknown how these cells acquire their position. Here, we show that the Gli3 hypomorphic mouse mutant Polydactyly Nagoya (Pdn) displays agenesis of the CC and mislocation of the glial and neuronal guidepost cells. Using transplantation experiments, we demonstrate that agenesis of the CC is primarily caused by midline defects. These defects originate during telencephalic patterning and involve an up-regulation of Slit2 expression and altered Fgf and Wnt/β-catenin signaling. Mutations in sprouty1/2 which mimic the changes in these signaling pathways cause a disorganization of midline guideposts and CC agenesis. Moreover, a partial recovery of midline abnormalities in Pdn/Pdn;Slit2(-/-) embryos mutants confirms the functional importance of correct Slit2 expression levels for callosal development. Hence, Gli3 controlled restriction of Fgf and Wnt/β-catenin signaling and of Slit2 expression is crucial for positioning midline guideposts and callosal development

Distinct Roles of Bcl-2 and Bcl-Xl in the Apoptosis of Human Bone Marrow Mesenchymal Stem Cells during Differentiation

Background: Adult mesenchymal stem cells (MSCs) can be maintained over extended periods of time before activation and differentiation. Little is known about the programs that sustain the survival of these cells. Principal Findings: Undifferentiated adult human MSCs (hMSCs) did not undergo apoptosis in response to different cell death inducers. Conversely, the same inducers can readily induce apoptosis when hMSCs are engaged in the early stages of differentiation. The survival of undifferentiated cells is linked to the expression of Bcl-Xl and Bcl-2 in completely opposite ways. Bcl-Xl is expressed at similar levels in undifferentiated and differentiated hMSCs while Bcl-2 is expressed only in differentiated cells. In undifferentiated hMSCs, the down-regulation of Bcl-Xl is associated with an increased sensitivity to apoptosis while the ectopic expression of Bcl-2 induced apoptosis. This apoptosis is linked to the presence of cytoplasmic Nur 77 in undifferentiated hMSCs. Significance: In hMSCs, the expression of Bcl-2 depends on cellular differentiation and can be either pro- or anti-apoptotic. Bcl-Xl, on the other hand, exhibits an anti-apoptotic activity under all conditions

Synapse Clusters Are Preferentially Formed by Synapses with Large Recycling Pool Sizes

Synapses are distributed heterogeneously in neural networks. The relationship between the spatial arrangement of synapses and an individual synapse's structural and functional features remains to be elucidated. Here, we examined the influence of the number of adjacent synapses on individual synaptic recycling pool sizes. When measuring the discharge of the styryl dye FM1–43 from electrically stimulated synapses in rat hippocampal tissue cultures, a strong positive correlation between the number of neighbouring synapses and recycling vesicle pool sizes was observed. Accordingly, vesicle-rich synapses were found to preferentially reside next to neighbours with large recycling pool sizes. Although these synapses with large recycling pool sizes were rare, they were densely arranged and thus exhibited a high amount of release per volume. To consolidate these findings, functional terminals were marked by live-cell antibody staining with anti-synaptotagmin-1-cypHer or overexpression of synaptopHluorin. Analysis of synapse distributions in these systems confirmed the results obtained with FM 1–43. Our findings support the idea that clustering of synapses with large recycling pool sizes is a distinct developmental feature of newly formed neural networks and may contribute to functional plasticity

Building Trust in Intelligent Automation: Insights into Structural Assurance Mechanisms for Autonomous Vehicles

Intelligent automation is increasingly taking over tasks that normally require substantial human experience and intuition. However, for individuals to delegate full control to applications like autonomous vehicles (AVs), they need to establish sufficient initial trust in the automation\u27s functionality, reliability and transparency. Manufacturers and external institutions may build users\u27 initial trust by providing structural assurance. Answering calls for a more context-specific, theoretically substantiated investigation of trust in AVs, we investigate how five different forms of structural assurance can be designed and how effective they are in trust-building: Technical, provider, legal, certifier and social protection. Extending previous, survey-based research, we conducted a choice-based conjoint experiment (n = 220). We find that external structural assurance in the form of legal and certifier protection may even outperform manufacturers\u27 trust-building efforts. This is especially the case for some user groups, as a cluster analysis reveals individuals\u27 heterogeneous preferences for structural assurance mechanisms