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Im Rahmen dieser Arbeit wurden zunächst neuartige ionische Agarosederivate synthetisiert und anschließend umfassend charakterisiert. Anionische Agarosesulfate mit einer regioselektiven Derivatisierung in Position G6 wurden durch homogene Umsetzung in ionischer Flüssigkeit erhalten. Kationische Agarosecarbamate mit einstellbarem Funktionalisierungsgrad waren durch einen zweistufigen Syntheseansatz zugänglich. Hierzu wurden zunächst Agarosephenylcarbonate in einer homogenen Synthese hergestellt, im Anschluss folgte eine Aminolyse zu den gewünschten funktionalen Agarosederivaten. Die ionischen Agarosederivate waren bereits bei geringen Funktionalisierungsgraden vollständig löslich in Wasser. Damit war es möglich, Alginatmikrokapseln polyelektrolytisch zu beschichten und diese als Träger für eine kontrollierte Wirkstofffreisetzung zu verwenden. Ebenfalls konnten Kompositgele aus Agarose, Hydroxyapatit und Agarosederivaten hergestellt und charakterisiert werden. Im zweiten Teil wurden sowohl die Kompositträgermaterialien als auch die Alginatmikrokapseln mit vier verschiedenen Modellwirkstoffen (ATP, Suramin, Methylenblau und A740003) beladen und die Wirkstofffreisetzung über einen Zeitraum von zwei Wochen untersucht. Für die ionischen Modellwirkstoffe erwiesen sich Kompositträgermaterialien mit ionischem Agarosederivat, die beschichteten Mikrokapseln sowie die Kombination aus Komposit und Kapseln als effektiv, um die Freisetzung auf bis zu 40% zu verlangsamen. Für die schlecht wasserlösliche Substanz A740003, ein Rezeptorligand für die osteogene Differenzierung von Stammzellen, wurde eine stark verzögerte Freisetzung aus Polyelektrolytemikrokapseln festgestellt. Mithilfe von literaturbekannten und neu entwickelten Anpassungsmodellen gelang es, die Diffusion als Hauptmechanismus der Wirkstofffreisetzung zu identifizieren und die Freisetzungskurven mathematisch akkurat zu beschreiben und daraus Rückschlüsse über die einzelnen Phasen der Freisetzung zu ziehen.
Elektronik für Entscheider
(2023)
Dieses Buch gibt Nichtingenieuren, die sich beruflich mit Elektronik beschäftigen, die Möglichkeit, sich ein Stück auf dieses Fachgebiet zu begeben, um Aufgaben, Sprache und Vorgehensweise von Ingenieuren zu verstehen. Ziel ist es dabei nicht, nach dem Lesen dieses Buches eine elektronische Schaltung entwickeln zu können. Im Vordergrund steht vielmehr ein generelles Verständnis für die Zusammenhänge und Grundbegriffe der Elektronik. (Verlagsangaben)
Background: the potency of drugs that interfere with glucose metabolism, i.e., glucose transporters (GLUT) and nicotinamide phosphoribosyltransferase (NAMPT) was analyzed in neuroendocrine tumor (NET, BON-1, and QPG-1 cells) and small cell lung cancer (SCLC, GLC-2, and GLC-36 cells) tumor cell lines. (2) Methods: the proliferation and survival rate of tumor cells was significantly affected by the GLUT-inhibitors fasentin and WZB1127, as well as by the NAMPT inhibitors GMX1778 and STF-31. (3) Results: none of the NET cell lines that were treated with NAMPT inhibitors could be rescued with nicotinic acid (usage of the Preiss–Handler salvage pathway), although NAPRT expression could be detected in two NET cell lines. We finally analyzed the specificity of GMX1778 and STF-31 in NET cells in glucose uptake experiments. As previously shown for STF-31 in a panel NET-excluding tumor cell lines, both drugs specifically inhibited glucose uptake at higher (50 μM), but not at lower (5 μM) concentrations. (4) Conclusions: our data suggest that GLUT and especially NAMPT inhibitors are potential candidates for the treatment of NET tumors.
Stably stratified Taylor–Green vortex simulations are performed by lattice Boltzmann methods (LBM) and compared to other recent works using Navier–Stokes solvers. The density variation is modeled with a separate distribution function in addition to the particle distribution function modeling the flow physics. Different stencils, forcing schemes, and collision models are tested and assessed. The overall agreement of the lattice Boltzmann solutions with reference solutions from other works is very good, even when no explicit subgrid model is used, but the quality depends on the LBM setup. Although the LBM forcing scheme is not decisive for the quality of the solution, the choice of the collision model and of the stencil are crucial for adequate solutions in underresolved conditions. The LBM simulations confirm the suppression of vertical flow motion for decreasing initial Froude numbers. To gain further insight into buoyancy effects, energy decay, dissipation rates, and flux coefficients are evaluated using the LBM model for various Froude numbers.
In dieser Arbeit wird eine kompressible Semi-Lagrangesche Lattice-Boltzmann-Methode neu entwickelt und erprobt. Die Lattice-Boltzmann-Methode ist ein Verfahren zur numerischen Strömungssimulation, das auf einer Modellierung von Partikeldichten und deren Interaktion untereinander basiert. In ihrer Ursprungsform ist die Methode jedoch auf schwach kompressible Strömungen mit niedriger Machzahl beschränkt. Wesentliche Nachteile der bisherigen Versuche zur Erweiterung auf supersonische Strömungen sind entweder mangelhafte Stabilität der Verfahren, unpraktikabel große Geschwindigkeitssätze oder die Beschränktheit auf kleine Zeitschrittweiten. Als Alternative zu bisherigen Ansätzen wird in dieser Arbeit ein Semi-Lagrangescher Strömungsschritt eingesetzt. Semi-Lagrangesche Verfahren entkoppeln mittels Interpolation die Orts-, Zeit- und Geschwindigkeitsdiskretisierung der ursprünglichen Lattice-Boltzmann-Methode. Nach der Einleitung wird im zweiten und dritten Kapitel dieser Arbeit zunächst auf die Grundlagen und Prinzipien der Lattice-Boltzmann-Methode eingegangen sowie bisherige Ansätze zur Simulation kompressibler Strömungen aufgeführt. Im Anschluss wird die kompressible Semi-Lagrangesche Lattice-Boltzmann-Methode entwickelt und beschrieben. Die Erweiterung erfolgt im Wesentlichen durch die Verknüpfung der Methode mit geeigneten Gleichgewichtsfunktionen und Geschwindigkeitssätzen. Im vierten Kapitel der Arbeit werden neue Kubatur-basierte Geschwindigkeitssätze entwickelt und getestet, darunter ein D3Q45-Geschwindigkeitssatz zur Berechnung kompressibler Strömungen, der den Rechenaufwand gegenüber konventionellen Geschwindigkeitsdiskretisierungen erheblich verringert. Im fünften Kapitel der Arbeit werden zur Validierung Simulationen von eindimensionalen Stoßrohren, zweidimensionalen Riemann-Problemen und Stoß-Wirbel-Interaktionen durchgeführt. Im Anschluss zeigen Simulationen von dreidimensionalen, kompressiblen Taylor-Green-Wirbeln sowie von wandgebundenen Testfällen die Vorteile der Methode für kompressible Strömungssimulationen. Zu diesem Zweck werden die Überschallströmung um ein zweidimensionales NACA-0012-Profil und um eine dreidimensionale Kugel sowie eine supersonische Kanalströmung untersucht. Dem Simulationsteil folgt eine umfangreiche Diskussion der Semi-Lagrangeschen Lattice-Boltzmann-Methode im Vergleich zu anderen Methoden. Die Vorteile der Methode, wie vergleichsweise große Zeitschrittweiten, körperangepasste Netze und die Stabilität der Methode, werden hier herausgearbeitet.
Liebe Leserinnen und Leser!
(2023)
Statistik im Fokus
(2023)
Digital ecosystems are driving the digital transformation of business models. Meanwhile, the associated processing of personal data within these complex systems poses challenges to the protection of individual privacy. In this paper, we explore these challenges from the perspective of digital ecosystems' platform providers. To this end, we present the results of an interview study with seven data protection officers representing a total of 12 digital ecosystems in Germany. We identified current and future challenges for the implementation of data protection requirements, covering issues on legal obligations and data subject rights. Our results support stakeholders involved in the implementation of privacy protection measures in digital ecosystems, and form the foundation for future privacy-related studies tailored to the specifics of digital ecosystems.
Risk-based authentication (RBA) aims to protect users against attacks involving stolen passwords. RBA monitors features during login, and requests re-authentication when feature values widely differ from those previously observed. It is recommended by various national security organizations, and users perceive it more usable than and equally secure to equivalent two-factor authentication. Despite that, RBA is still used by very few online services. Reasons for this include a lack of validated open resources on RBA properties, implementation, and configuration. This effectively hinders the RBA research, development, and adoption progress.
To close this gap, we provide the first long-term RBA analysis on a real-world large-scale online service. We collected feature data of 3.3 million users and 31.3 million login attempts over more than 1 year. Based on the data, we provide (i) studies on RBA’s real-world characteristics plus its configurations and enhancements to balance usability, security, and privacy; (ii) a machine learning–based RBA parameter optimization method to support administrators finding an optimal configuration for their own use case scenario; (iii) an evaluation of the round-trip time feature’s potential to replace the IP address for enhanced user privacy; and (iv) a synthesized RBA dataset to reproduce this research and to foster future RBA research. Our results provide insights on selecting an optimized RBA configuration so that users profit from RBA after just a few logins. The open dataset enables researchers to study, test, and improve RBA for widespread deployment in the wild.
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.
Work-related thoughts during off-job time have been studied extensively in occupational health psychology and related fields. We provide a focused review of the research on overcommitment—a component within the effort–reward imbalance model—and aim to connect this line of research to the most commonly studied aspects of work-related rumination. Drawing on this integrative review, we analyze survey data on ten facets of work-related rumination, namely (1) overcommitment, (2) psychological detachment, (3) affective rumination, (4) problem-solving pondering, (5) positive work reflection, (6) negative work reflection, (7) distraction, (8) cognitive irritation, (9) emotional irritation, and (10) inability to recover. First, we apply exploratory factor analysis to self-reported survey data from 357 employees to calibrate overcommitment items and to position overcommitment within the nomological net of work-related rumination constructs. Second, we leverage apply confirmatory factor analysis to self-reported survey data from 388 employees to provide a more specific test of uniqueness vs. overlap among these constructs. Third, we apply relative weight analysis to assess the unique criterion-related validity of each work-related rumination facet regarding (1) physical fatigue, (2) cognitive fatigue, (3) emotional fatigue, (4) burnout, (5) psychosomatic complaints, and (6) satisfaction with life. Our results suggest that several measures of work-related rumination (e.g., overcommitment and cognitive irritation) can be used interchangeably. Emotional irritation and affective rumination emerge as the strongest unique predictors of fatigue, burnout, psychosomatic complaints, and satisfaction with life. Our study is intended to assist researchers in making informed decisions on selecting scales for their research and paves the way for integrating research on the effort–reward imbalance and work-related rumination.
Work-related thoughts in off-job time have been studied extensively in occupational health psychology and related fields. We provide a focused review of research on overcommitment – a component within the effort-reward imbalance model – and aim to connect this line of research to the most commonly studied aspects of work-related rumination. Drawing on this integrative review, we analyze survey data on ten facets of work-related rumination, namely (1) overcommitment, (2) psychological detachment, (3) affective rumination, (4) problem-solving pondering, (5) positive work reflection, (6) negative work reflection, (7) distraction, (8) cognitive irritation, (9) emotional irritation, and (10) inability to recover. First, we leverage exploratory factor analysis to self-report survey data from 357 employees to calibrate overcommitment items and to position overcommitment within the nomological net of work-related rumination constructs. Second, we leverage confirmatory factor analysis to self-report survey data from 388 employees to provide a more specific test of uniqueness vs. overlap among these constructs. Third, we apply relative weight analysis to quantify the unique criterion-related validity of each work-related rumination facet regarding (1) physical fatigue, (2) cognitive fatigue, (3) emotional fatigue, (4) burnout, (5) psychosomatic complaints, and (6) satisfaction with life. Our results suggest that several measures of work-related rumination (e.g., overcommitment and cognitive irritation) can be used interchangeably. Emotional irritation and affective rumination emerge as the strongest unique predictors of fatigue, burnout, psychosomatic complaints, and satisfaction with life. Our study assists researchers in making informed decisions on selecting scales for their research and paves the way for integrating research on effort-reward imbalance and work-related rumination.
Background
Consumers rely heavily on online user reviews when shopping online and cybercriminals produce fake reviews to manipulate consumer opinion. Much prior research focuses on the automated detection of these fake reviews, which are far from perfect. Therefore, consumers must be able to detect fake reviews on their own. In this study we survey the research examining how consumers detect fake reviews online.
Methods
We conducted a systematic literature review over the research on fake review detection from the consumer-perspective. We included academic literature giving new empirical data. We provide a narrative synthesis comparing the theories, methods and outcomes used across studies to identify how consumers detect fake reviews online.
Results
We found only 15 articles that met our inclusion criteria. We classify the most often used cues identified into five categories which were (1) review characteristics (2) textual characteristics (3) reviewer characteristics (4) seller characteristics and (5) characteristics of the platform where the review is displayed.
Discussion
We find that theory is applied inconsistently across studies and that cues to deception are often identified in isolation without any unifying theoretical framework. Consequently, we discuss how such a theoretical framework could be developed.
Protokoll 27
(2023)
This thesis proposes a multi-label classification approach using the Multimodal Transformer (MulT) [80] to perform multi-modal emotion categorization on a dataset of oral histories archived at the Haus der Geschichte (HdG). Prior uni-modal emotion classification experiments conducted on the novel HdG dataset provided less than satisfactory results. They uncovered issues such as class imbalance, ambiguities in emotion perception between annotators, and lack of representative training data to perform transfer learning [28]. Hence, the objectives of this thesis were to achieve better results by performing a multi-modal fusion and resolving the problems arising from class imbalance and annotator-induced bias in emotion perception. A further objective was to assess the quality of the novel HdG dataset and benchmark the results using SOTA techniques. Through a literature survey on the challenges, models, and datasets related to multi-modal emotion recognition, we created a methodology utilizing the MulT along with a multi-label classification approach. This approach produced a considerable improvement in the overall emotion recognition by obtaining an average AUC of 0.74 and Balanced-accuracy of 0.70 on the HdG dataset, which is comparable to state-of-the-art (SOTA) results on other datasets. In this manner, we were also able to benchmark the novel HdG dataset as well as introduce a novel multi-annotator learning approach to understand each annotator’s relative strengths and weaknesses for emotion perception. Our evaluation results highlight the potential benefits of the novel multi-annotator learning approach in improving overall performance by resolving the problems arising from annotator-induced bias and variation in the perception of emotions. Complementing these results, we performed a further qualitative analysis of the HdG annotations with a psychologist to study the ambiguities found in the annotations. We conclude that the ambiguities in annotations may have resulted from a combination of several socio-psychological factors and systemic issues associated with the process of creating these annotations. As these problems are also present in most multi-modal emotion recognition datasets, we conclude that the domain could benefit from a set of annotation guidelines to create standardized datasets.
Risk-Based Authentication for OpenStack: A Fully Functional Implementation and Guiding Example
(2023)
Online services have difficulties to replace passwords with more secure user authentication mechanisms, such as Two-Factor Authentication (2FA). This is partly due to the fact that users tend to reject such mechanisms in use cases outside of online banking. Relying on password authentication alone, however, is not an option in light of recent attack patterns such as credential stuffing.
Risk-Based Authentication (RBA) can serve as an interim solution to increase password-based account security until better methods are in place. Unfortunately, RBA is currently used by only a few major online services, even though it is recommended by various standards and has been shown to be effective in scientific studies. This paper contributes to the hypothesis that the low adoption of RBA in practice can be due to the complexity of implementing it. We provide an RBA implementation for the open source cloud management software OpenStack, which is the first fully functional open source RBA implementation based on the Freeman et al. algorithm, along with initial reference tests that can serve as a guiding example and blueprint for developers.
Pursuant to Sustainable Development Goal (SDG) 15 of the 2030 Agenda for Sustainable Development of the United Nations, one pivotal target is to halt biodiversity loss. This paper’s objective is to analyze why and how German farmers hesitate to implement more than the prescriptive measures with regard to cross compliance and direct payments under the European Common Agricultural Policy (CAP) and what their aspirations are for possible incentives to bring biodiversity into focus. By applying a mixed methods approach, we investigate the experience of individual farmers by means of a qualitative approach followed by a quantitative study. This analysis sheds light on how farmers perceive indirect influencing factors and how these factors play a non-negligible role in farmers´ commitment to biodiversity. Economy, policy and society are intertwined and need to be considered from a multi-faceted perspective. In addition, an in-depth analysis is conducted based on online focus group discussions to determine whether farmers accept financial support, focusing on both action- and success-oriented payments. Our results highlight the importance of paying attention to the heterogeneity of farmers, their locations and, consequently, farmers’ different views on indirect drivers influencing agricultural processes, showing the complexity of the problem. Although farmers’ expectations can be met with financial allocations, other aspects must also be taken into account.
This paper aims to assess farmers’ challenges in enhancing biodiversity. The so-called “trilemma” (WBGU 2021) of land use stems from the multiple demands made on land for the benefit of mitigating climate change, securing food, and maintaining biodiversity. Agriculture is accused of maladministration, causing soil contamination, animal cruelty, bee mortality, and climate change. However, farmers play a key role in overcoming upcoming sustainability challenges. While their supportive role is urgently needed, farmers find themselves caught between a “rock” and a ”hard place”. Consumers call for sustainable production and affordable food products without pesticide residues, demanding enough for all. Farmers are restricted by the wants and needs of consumers who are influenced by interest groups and exposed to interdependent direct and indirect influencing factors. They need to balance the scrutiny of the critical public as well as the regulatory control. In this paper, we collected and surveyed the data of farmers within or close to the 21 selected nature protected areas of the DINA (Diversity of Insects in Nature protected Areas) Project, using a mixed methods approach with a semi-structured questionnaire considering issues’ interdependencies and the complexity of today´s problems. The conflicts and obstacles faced by farmers were assessed. The results reflect the farmers’ willingness and the importance of receiving appreciation for implementing biodiversity measures. These results, complemented by a following quantitative study, are the basis for recommendations for policymakers and farmers in all German nature protected areas.