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During space missions astronauts suffer from cardiovascular deconditioning, when they are exposed to microgravity conditions. Until now, no specific drugs are available for effective countermeasures, since the underlying mechanism is not completely understood. Endothelial cells (ECs) and smooth muscle cells (SMCs) play crucial roles in a variety of cardiovascular functions, many of which are regulated via P2 receptors. However, their function in ECs and SMCs under microgravity condition is still unknown. In this study, ECs and SMCs were isolated from bovine aorta and differentiated from human mesenchymal stem cells (hMSCs), respectively. Subsequently, the cells were verified based on specific markers. An altered P2 receptor expression pattern was detected during the commitment of hMSC towards ECs and SMCs. The administration of natural and artificial P2 receptor agonists and antagonists directly affected the differentiation process. By using EC growth medium as conditioned medium, a vessel cell model was created to culture SMCs and vice versa. Within this study, we were able to show for the first time that the expression of some P2 receptors were altered in ECs and SMCs grown for 24h under simulated microgravity conditions. On the other hand, in some P2 receptor expressions such as P2X7 conditioned medium compensated this change.
In conclusion, our data show that P2 receptors play an important functional role in hMSC differentiation towards ECs and SMCs. Since some P2 receptor artificial ligands are already used as drugs for patients with cardiovascular diseases, it is reasonable to assume that in the future they might be promising candidates for treating cardiovascular deconditioning.
Risikobasierte Authentifizierung (RBA) ist ein adaptiver Ansatz zur Stärkung der Passwortauthentifizierung. Er überwacht eine Reihe von Merkmalen, die sich auf das Loginverhalten während der Passworteingabe beziehen. Wenn sich die beobachteten Merkmalswerte signifikant von denen früherer Logins unterscheiden, fordert RBA zusätzliche Identitätsnachweise an. Regierungsbehörden und ein Erlass des US-Präsidenten empfehlen RBA, um Onlineaccounts vor Angriffen mit gestohlenen Passwörtern zu schützen. Trotz dieser Tatsachen litt RBA unter einem Mangel an offenem Wissen. Es gab nur wenige bis keine Untersuchungen über die Usability, Sicherheit und Privatsphäre von RBA. Das Verständnis dieser Aspekte ist jedoch wichtig für eine breite Akzeptanz.
Diese Arbeit soll ein umfassendes Verständnis von RBA mit einer Reihe von Studien vermitteln. Die Ergebnisse ermöglichen es, datenschutzfreundliche RBA-Lösungen zu schaffen, die die Authentifizierung stärken bei gleichzeitig hoher Menschenakzeptanz.
Computer graphics research strives to synthesize images of a high visual realism that are indistinguishable from real visual experiences. While modern image synthesis approaches enable to create digital images of astonishing complexity and beauty, processing resources remain a limiting factor. Here, rendering efficiency is a central challenge involving a trade-off between visual fidelity and interactivity. For that reason, there is still a fundamental difference between the perception of the physical world and computer-generated imagery. At the same time, advances in display technologies drive the development of novel display devices. The dynamic range, the pixel densities, and refresh rates are constantly increasing. Display systems enable a larger visual field to be addressed by covering a wider field-of-view, due to either their size or in the form of head-mounted devices. Currently, research prototypes are ranging from stereo and multi-view systems, head-mounted devices with adaptable lenses, up to retinal projection, and lightfield/holographic displays. Computer graphics has to keep step with, as driving these devices presents us with immense challenges, most of which are currently unsolved. Fortunately, the human visual system has certain limitations, which means that providing the highest possible visual quality is not always necessary. Visual input passes through the eye’s optics, is filtered, and is processed at higher level structures in the brain. Knowledge of these processes helps to design novel rendering approaches that allow the creation of images at a higher quality and within a reduced time-frame. This thesis presents the state-of-the-art research and models that exploit the limitations of perception in order to increase visual quality but also to reduce workload alike - a concept we call perception-driven rendering. This research results in several practical rendering approaches that allow some of the fundamental challenges of computer graphics to be tackled. By using different tracking hardware, display systems, and head-mounted devices, we show the potential of each of the presented systems. The capturing of specific processes of the human visual system can be improved by combining multiple measurements using machine learning techniques. Different sampling, filtering, and reconstruction techniques aid the visual quality of the synthesized images. An in-depth evaluation of the presented systems including benchmarks, comparative examination with image metrics as well as user studies and experiments demonstrated that the methods introduced are visually superior or on the same qualitative level as ground truth, whilst having a significantly reduced computational complexity.
Daryoush Daniel Vaziri illustrates that the use of mixed methods designs may support the induction of more subtle and complete theories about older adults’ use of technologies for the support of active and healthy aging. The results show that older adults’ social contexts and environments considerably affect their perspectives, practices and attitudes with respect to health, quality of life, well-being and technology use for active and healthy aging support. Results were collected with older adults aged 60+ as well as relevant secondary stakeholders like caregivers, policy makers or health insurance companies.
The processing of employee personal data is dramatically increasing. To protect employees' fundamental right to privacy, the law provides for the implementation of privacy controls, including transparency and intervention. At present, however, the stakeholders responsible for putting these obligations into action, such as employers and software engineers, simply lack the fundamental knowledge needed to design and implement the necessary controls. Indeed, privacy research has so far focused mainly on consumer relations in the private context. In contrast, privacy in the employment context is less well studied. However, since privacy is highly context-dependent, existing knowledge and privacy controls from other contexts cannot simply be adopted to the employment context. In particular, privacy in employment is subject to different legal and social norms, which require a different conceptualization of the right to privacy than is usual in other contexts. To adequately address these aspects, there is broad consensus that privacy must be regarded as a socio-technical concept in which human factors must be considered alongside technical-legal factors. Today, however, there is a particular lack of knowledge about human factors in employee privacy. Disregarding the needs and concerns of individuals or lack of usability, though, are common reasons for the failure of privacy and security measures in practice. This dissertation addresses key knowledge gaps on human factors in employee privacy by presenting the results of a total of three in-depth studies with employees in Germany. The results provide insights into employees' perceptions of the right to privacy, as well as their perceptions and expectations regarding the processing of employee personal data. The insights gained provide a foundation for the human-centered design and implementation of employee-centric privacy controls, i.e., privacy controls that incorporate the views, expectations, and capabilities of employees. Specifically, this dissertation presents the first mental models of employees on the right to informational self-determination, the German equivalent of the right to privacy. The results provide insights into employees' (1) perceptions of categories of data, (2) familiarity and expectations of the right to privacy, and (3) perceptions of data processing, data flow, safeguards, and threat models. In addition, three major types of mental models are presented, each with a different conceptualization of the right to privacy and a different desire for control. Moreover, this dissertation provides multiple insights into employees' perceptions of data sensitivity and willingness to disclose personal data in employment. Specifically, it highlights the uniqueness of the employment context compared to other contexts and breaks down the multi-dimensionality of employees' perceptions of personal data. As a result, the dimensions in which employees perceive data are presented, and differences among employees are highlighted. This is complemented by identifying personal characteristics and attitudes toward employers, as well as toward the right to privacy, that influence these perceptions. Furthermore, this dissertation provides insights into practical aspects for the implementation of personal data management solutions to safeguard employee privacy. Specifically, it presents the results of a user-centered design study with employees who process personal data of other employees as part of their job. Based on the results obtained, a privacy pattern is presented that harmonizes privacy obligations with personal data processing activities. The pattern is useful for designing privacy controls that help these employees handle employee personal data in a privacy-compliant manner, taking into account their skills and knowledge, thus helping to protect employee privacy. The outcome of this dissertation benefits a wide range of stakeholders who are involved in the protection of employee privacy. For example, it highlights the challenges to be considered by employers and software engineers when conceptualizing and designing employee-centric privacy controls. Policymakers and researchers gain a better understanding of employees' perceptions of privacy and obtain fundamental knowledge for future research into theoretical and abstract concepts or practical issues of employee privacy. Employers, IT engineers, and researchers gain insights into ways to empower data processing employees to handle employee personal data in a privacy-compliant manner, enabling employers to improve and promote compliance. Since the basic principles underlying informational self-determination have been incorporated into European privacy legislation, we are confident that our results are also of relevance to stakeholders outside Germany.
In forensic DNA profiling, the occurrence of complex mixed profiles is currently a common issue. Cases involving intimate swabs or skin flake tape liftings are prone to mixed profiles, because of more than one donor contributing to a DNA sample. By DNA profiling of single spermatozoa and skin flakes, problems associated with mixed profile could ideally be overcome. However, PCR is not a sensitive enough method to generate DNA profiles by STRs on single cells. Moreover, high quality intact DNA is required, but is not always available in skin flakes due to degradation. Additionally, single skin flakes are difficult to discriminate from other similar looking particles on tape liftings used to secure DNA samples from evidence. The main purpose of this study was to develop a method that enables DNA profiling of single sperm cells and skin flakes. After studying multiple whole genome amplification (WGA) protocols, REPLI-g Single Cell WGA was selected due to its suitability in the pre-amplification step of template DNA. Micromanipulation was used to isolate single spermatozoa. Furthermore, micromanipulation in combination with REPLI-g Single Cell WGA resulted in successful DNA profiling of single spermatozoa by using autosomal STRs as well as X- and Y-chromosomal STRs. The single spermatozoa DNA profiling method described in this thesis was successfully used to identify male contributors from mock intimate swabs with a mixture of semen from multiple male contributors. Different dyes were analysed to develop a staining method to discriminate skin flakes from other particles including particles such as those from hair cosmetic products. From all dyes tested, Orange G was the only dye which successfully discriminated skin flakes from hair product particles. Also, an alkaline based lysis protocol was developed that allowed PCR to be carried out directly on the lysates of single skin flakes. Furthermore, REPLI-g Single Cell WGA was tested on single skin flakes. In contrast to the single spermatozoa, REPLI-g Single Cell WGA was not successful in DNA profiling of single skin flakes. The single skin flake DNA profiling method described in this thesis was successfully used in correctly identifying contributors from mock mixed DNA evidence. Additionally, a small amplicon-based NGS method was tested on single skin flakes. Compared to the PCR and CE approach, the small amplicon-based NGS method improved DNA profiling of single skin flakes, giving a significant increase in allele recovery. In conclusion, this study shows circumventing mixtures is possible by DNA profiling of single spermatozoa, using micromanipulation and WGA. Furthermore, DNA profiling of single skin flakes has been improved by the staining of tape liftings methodology with Orange G, alkaline lysis, direct-PCR and a small amplicon-based NGS approach. Nonetheless, future work is required to assess the performance of the single spermatozoa method on mock swabs with more diluted semen. Also, commercially available NGS kits should be tested with single skin flakes and compared with the in-house NGS method.
Remineralizing soils? The agricultural usage of silicate rock powders in the context of One Health
(2022)
The concept of soil health describes the capacity of soil to fulfill essential functions and ecosystem services. Healthy soils are inextricably linked to sustainable agriculture and are crucial for the interconnected health of plants, animals, humans, and their environment ("One Health"). However, soil health is threatened through unprecedented rates of soil degradation. A major form of soil degradation is nutrient depletion, which has been seriously underestimated for potassium (K) and several micronutrients. One way to replenish K and micronutrients are multi-nutrient silicate rock powders (SRPs). Their agronomic suitability has long been questioned due to slow weathering rates, although recent studies found significant soil health improvements and challenge past objections which insufficiently addressed the factorial complexity of the weathering process. Furthermore, environmental co-benefits might arise through their mixture with livestock slurry, which could reduce the slurry’s ammonia (NH3) emissions and improve its biophysicochemical properties. However, neither SRPs effects on soil health, nor the biophysicochemical effects of mixing SRPs with livestock slurry have hitherto been comprehensively analyzed. The overall aim of this dissertation is thus to review the agricultural usage of SRPs in the context of One Health. The first part of this thesis starts with an elaboration of the health concept in general and then explores the interlinkages between soil health and One Health. Subsequently, the potentials and oftentimes bypassed problems of operationalizing soil health will be outlined, and feasible ways for its future usage are proposed. In the second part of the thesis, it is reviewed how and under which circumstances SRPs can ameliorate soil health. This is done by presenting a new framework with the most relevant factors for the usage of SRPs through which several contradictory outcomes of prior studies can be explained. A subsequent analysis of 48 crop trials reveals the potential of SRPs as K and multi-nutrient soil amendment for tropical soils, whereas the benefits for temperate soils are inconclusive. The review revealed various co-benefits that could substantially increase SRPs overall agronomic efficiency. The last part of the thesis reports about the effects of mixing two rock powders with cattle slurry. SRPs significantly increased the slurry´s CH4 emission rates, whereas the effects on NH3, CO2, and N2O emission rates were mostly insignificant. The rock powders increased the nutrient content of the slurry and altered its microbiology. In conclusion, the concept of soil health must be operationalized in more specific, practical, and context-dependent ways. Particularly in humid tropical environments, SRPs could advance low-cost soil health ameliorations, and its usage could have additional co-benefits regarding One Health. Mixing SRPs with organic materials like livestock slurry could overcome the major obstacle of their low solubility, although the effects on NH3 and greenhouse gas emissions must be further evaluated.
In this doctoral thesis the curing process of visible light-curing (VLC) dental composites and 3D printing rapid prototyping (RP) materials are investigated with the focus on dielectric analysis (DEA). This method is able to monitor the curing of resins in an alternating electric fringe field with adjustable frequencies and is often used for cure control of composites manufacturing in the aviation and automotive industry but hardly established in dental science or RP method development. It is capable of investigating very fast initiation and primary curing processes using high frequencies in the kHz-range. The aim of the Thesis is a better understanding of the curing processes with respect to curing parameters such as resin composition, viscosity, temperature, and for light-curing composites also light intensity and irradiation depth. Due to the nature of both dental and RP systems an application of specific experimental set-up had to be designed allowing for the generation of reproducible and valid results. Subsequently, different evaluation methods were developed to characterize the curing behavior of both material types. A special focus was paid to the determination of kinetic parameters from DEA measurements. Reaction rates of the curing of the corresponding thermosets were calculated and applied to the ion viscosity curves measured by DEA to evaluate reaction kinetic parameters. For the dental composites it could be clearly shown that the initial curing rate is directly proportional to light intensity and not to its square root as proposed by many others authors. A good description of the curing behaviour of 3DP RP materials was also achieved assuming a reaction order smaller than one. This data provides the base for the kinetic modeling of polymerization and curing processes proposed within the Thesis.
The detection of human skin in images is a very desirable feature for applications such as biometric face recognition, which is becoming more frequently used for, e.g., automated border or access control. However, distinguishing real skin from other materials based on imagery captured in the visual spectrum alone and in spite of varying skin types and lighting conditions can be dicult and unreliable. Therefore, spoofing attacks with facial disguises or masks are still a serious problem for state of the art face recognition algorithms. This dissertation presents a novel approach for reliable skin detection based on spectral remission properties in the short-wave infrared (SWIR) spectrum and proposes a cross-modal method that enhances existing solutions for face verification to ensure the authenticity of a face even in the presence of partial disguises or masks. Furthermore, it presents a reference design and the necessary building blocks for an active multispectral camera system that implements this approach, as well as an in-depth evaluation. The system acquires four-band multispectral images within T = 50ms. Using a machine-learning-based classifier, it achieves unprecedented skin detection accuracy, even in the presence of skin-like materials used for spoofing attacks. Paired with a commercial face recognition software, the system successfully rejected all evaluated attempts to counterfeit a foreign face.
Collaboration among multiple users on large screens leads to complicated behavior patterns and group dynamics. To gain a deeper understanding of collaboration on vertical, large, high-resolution screens, this dissertation builds on previous research and gains novel insights through new observational studies. Among other things, the collected results reveal new patterns of collaborative coupling, suggest that territorial behavior is less critical than shown in previous research, and demonstrate that workspace awareness can also negatively affect the effectiveness of individual users.