Scientific publications of the Saarland University
Not a member yet
14321 research outputs found
Sort by
Challenges for Individual digital sovereignty in the context of security and privacy
Get PDFDigital sovereignty empowers individuals to make self-determined decisions and actions regarding digital technologies, particularly concerning security and privacy. This dissertation explores the security and privacy challenges limiting users’ digital sovereignty through four studies. First, I investigate self-hosted systems that offer maximum digital sovereignty. A qualitative study explores why people self-host and what challenges they face. A quantitative study examines the prevalence and characteristics of these systems and their operators. These studies highlight the potential for digital sovereignty but underscore significant barriers, especially in securing systems. Next, I examine mainstream technologies that restrict user sovereignty. A study on autonomous vehicles, which require minimal user input but offer limited control, examines the information drivers need for security-critical situations, enabling digitally sovereign use. Lastly, I analyze global corporations’ impact on non-Western populations through a study of Pakistani content creators on social media. The study reveals insufficient safeguards for vulnerable communities in a shifting threat landscape. These studies suggest that while automation can aid, users value informed decision-making in critical contexts. Additionally, reliance on large corporations fails to guarantee security and privacy for all users, emphasizing the need for alternative approaches to enhance digital sovereignty.Digitale Souveränität ermöglicht es, selbstbestimmte Entscheidungen über digitale Technologien zu treffen, besonders hinsichtlich Sicherheit und Datenschutz. Diese Dissertation untersucht in vier Studien Sicherheits- und Datenschutzprobleme, die die digitale Souveränität einschränken. Zunächst analysiere ich selbst gehostete Systeme, die maximale Souveränität bieten. Eine qualitative Studie zeigt, warum Menschen diese nutzen und welche Herausforderungen sie bewältigen müssen. Eine quantitative Studie untersucht die Verbreitung und Merkmale dieser Systeme und deren Betreibern. Beide Studien verdeutlichen das Potenzial, weisen aber auf Sicherheitsprobleme hin. Weiterhin untersuche ich Mainstream-Technologien, die Nutzerautonomie begrenzen. Eine Studie über autonome Fahrzeuge beleuchtet, welche Informationen Nutzer in sicherheitskritischen Situationen benötigen, um informierte Entscheidungen zu treffen.Eine weitere Analyse zeigt, dass soziale Medien globaler Unternehmen Privatsphäre und Sicherheit nicht ausreichend für alle Nutzergruppen gewährleisten, wie etwa für pakistanische Content Creators. Die Ergebnisse zeigen, dass Automatisierung zwar unterstützt, aber Nutzer in kritischen Kontexten mitbestimmen wollen. Zudem unterstreichen sie die Notwendigkeit alternativer Ansätze, um Abhängigkeiten von Großkonzernen zu reduzieren und digitale Souveränität für alle Nutzergruppen zu stärken
Cutaneous‐limited, initially strongly unilateral microscopic polyangiitis
Get PDFA 44-year-old female patient presented in good general health, but with obesity. Strictly limited to the left half of the body, up to 20 painful, reddish, roundish macules with a hemorrhagic appearance were found. The lesions were particularly prominent on the upper body, including the left half of the face and the left arm. In the dependent areas, especially on the lower legs, the macules developed into infiltrated, hemorrhagic plaques and ultimately to hemorrhagic necroses and ulcerations (Figure 1). The symptoms had initially started one month before with a single painful ulcer on the left lower leg. Chills and other signs of infection were denied. The patient reported joint pain and episodes of abdominal pain and nausea. The physical status, including the neurological status, was unremarkable
Silagermylenation of CO bonds and radical fragmentation of CO2-expanded bis(germylene) by a cyclic (alkyl)(amino)carbene
Get PDFThe transformation of the greenhouse gas CO2 into value-added products represents a major contemporary challenge. Low-valent p-block compounds typically react at the oxygen termini of CO2 due to the oxophilicity of the metal centers. We now report on the selective activation of CO2 and ethyl isocyanate at the central carbon atom by an N-heterocyclic carbene (NHC)-stabilized para-silylenephenylene-bridged bis(germylene). During the net silagermylenation, the C[double bond, length as m-dash]X (X = O, NEt) bonds are inserted into the Ge–Si bonds through cooperativity of the low-valent metal center and the electrophilic silyl backbone. The germanium(II) centers are retained in the products, as is confirmed by multinuclear NMR data, IR spectroscopy and X-ray analysis and supported by DFT calculations. Attempts to substitute the NHCs by cyclic (alkyl)(amino)carbenes (CAACs) resulted in a germylene-CAAC radical by homolytic cleavage of the Si–O bonds as evidenced by single crystal X-ray diffraction and continuous-wave EPR spectroscopy
Continuous wet-chemical synthesis and pyrolysis of inorganic-organic hybrid materials based on polyoxomolybdates and their electrochemical performance as anode materials in lithium-ion batteries
Get PDFContinuous wet-chemical synthesis of scale surface area particles in the micro- to nanometer range is possible with the microjet reactor. Synthesis involving the microjet reactor is a sustainable, low-energy process that can be used to achieve high throughputs with high reproducibility. These factors are especially important for industrial applications. In this dissertation, inorganic-organic hybrid materials were synthesized through the aqueous precipitation reaction with ammonium heptamolybdate (AHM) and different organic species, namely para-phenylenediamine (PPD), 1,8-diaminonaphthalene (1,8-DAN) or hexamethylenediamine (HMD). Systematic studies were performed by varying the ratios of the reactants. Varying molar ratios of molybdates to organic species and pH resulted in different crystalline hybrid compounds. By pyrolyzing these inorganic-organic hybrid precursors, mixtures of molybdenum carbide, nitride, oxide, elemental Mo and mixed anionic compounds such as Mo(C,N,O)x composites embedded in a carbonaceous matrix can be obtained. The morphology of the starting materials is also preserved after pyrolysis. Since morphology is a key property for Li-ion battery performance, this process is particularly suitable for Li-ion battery material synthesis.Die kontinuierliche nasschemische Synthese von Partikeln mit skalierter Oberfläche im Mikro- bis Nanometerbereich ist mit dem Mikrojetreaktor möglich. Die Synthese mit dem Mikrojetreaktor ist ein nachhaltiges, energiearmes Verfahren, mit dem sich hohe Durchsätze bei hoher Reproduzierbarkeit erzielen lassen. Diese Faktoren sind für industrielle Anwendungen besonders wichtig. In dieser Dissertation wurden anorganisch-organische Hybridmaterialien durch die wässrige Fällungsreaktion mit Ammoniumheptamolybdat (AHM) und verschiedenen organischen Spezies, nämlich para-Phenylendiamin (PPD), 1,8-Diaminonaphthalin (1,8-DAN) oder Hexamethylendiamin (HMD), synthetisiert. Es wurden systematische Studien durchgeführt, indem die Verhältnisse der Reaktanten variiert wurden. Unterschiedliche molare Verhältnisse von Molybdaten zu organischen Spezies und der pH-Wert führten zu verschiedenen kristallinen Hybridverbindungen. Durch Pyrolyse dieser anorganisch-organischen Hybridvorläufer können Mischungen aus Molybdäncarbid, -nitrid, -oxid, elementarem Mo und gemischten anionischen Verbindungen wie Mo(C,N,O)x-Verbindungen, die in eine kohlenstoffhaltige Matrix eingebettet sind, erhalten werden. Die Morphologie der Ausgangsmaterialien bleibt auch nach der Pyrolyse erhalten. Da die Morphologie eine Schlüsseleigenschaft für die Leistung von Lithium-Ionen-Batterien ist, eignet sich dieses Verfahren besonders gut für die Materialsynthese von Lithium-Ionen-Batterien
A Comparative Study Using Reversed-Phase and Hydrophilic Interaction Liquid Chromatography to Investigate the In Vitro and In Vivo Metabolism of Five Selenium-Containing Cathinone Derivatives
Get PDFBackground/Objectives: The emergence of cathinone-based psychostimulants necessitates
ongoing research and analysis of the characteristics and properties of novel derivatives. The
metabolic fate of five novel cathinone-derived substances (ASProp, MASProp, MASPent,
PySProp, and PySPent) containing a selenophene moiety was investigated in vitro and
in vivo. Methods: All compounds were incubated individually with pooled human liver
S9 fraction. A monooxygenase activity screening investigating the metabolic contribution
of eleven recombinant phase I isoenzymes was conducted. Rat urine after oral admin istration was prepared by urine precipitation. Liquid chromatography–high-resolution
tandem mass spectrometry was used for the analysis of all samples. Reversed-phase liquid
chromatography (RPLC) and zwitterionic hydrophilic interaction liquid chromatography
(HILIC) were used to evaluate and compare the metabolites’ chromatographic resolution.
Results: Phase I reactions of ASProp, MASProp, MASPent, PySProp, and PySPent included
N-dealkylation, hydroxylation, reduction, and combinations thereof. The monooxygenase
activity screening revealed the contribution of various isozymes. Phase II reactions de tected in vivo included N-acetylation and glucuronidation. Both chromatographic columns
complemented each other. Conclusions: All substances revealed metabolic reactions com parable to those observed for other synthetic cathinones. Contributions from isozymes to
their metabolism minimized the risk of drug–drug interactions. The identified metabo lites should be considered as targets in human biosamples, especially in urine screening
procedures. RPLC and HILIC can both be recommended for this purpose
Thermoplasmonic stimulation of gold nanorods for engineered living materials
Get PDFEngineered Living Materials (ELMs) with living cells in polymer gels enable the synthesis and controlled release of therapeutic molecules. This thesis explores the optical triggering of ELMs using thermoplasmonic gold nanorods (AuNRs) embedded in Pluronic or polyvinyl alcohol hydrogels. Upon near-infrared (NIR) irradiation (808 nm), AuNRs generate localized heat, activating thermoresponsive bacteria. Structured bilayer constructs with an AuNR-containing bottom layer and a bacteria-loaded top layer were developed. NIR light heated the lower layer, and the diffused heat induced mCherry expression in engineered E. coli. Temperature distribution and fluorescence analysis demonstrated controlled bacterial activation and the possibility to control protein production via light intensity. The system was then adapted to produce QK peptide, a VEGF-mimicking angiogenic factor, in a single-layer hydrogel, with secretion monitored via Nanoluciferase. The approach was extended to NIR-sensitized nanocomposite PluDA hydrogels, incorporated in 3D-printed waveguides by a partner. Single- and double-segmented fibers enabled localized heating along the waveguide, with core-shell structures demonstrating confined plasmonic heating. This facilitates NIR-triggered bacterial activation in deep tissue environments, offering a pathway for advanced therapeutic ELMs.Engineered Living Materials (ELMs) mit lebenden Zellen in Polymergelen ermöglichen die kontrollierte Synthese und Freisetzung therapeutischer Moleküle. Diese Dissertation untersucht die optische Aktivierung von ELMs durch thermoplasmonische Goldnanostäbchen (AuNRs) in Pluronic- oder Polyvinylalkohol-Hydrogelen. Unter der Bestrahlung mit Nahinfrarotlicht (NIR, 808 nm) erzeugen AuNRs lokalisierte Wärme, die thermoresponsive Bakterien aktiviert. Doppelschicht-Konstrukte mit einer AuNR-haltigen Bodenschicht und einer bakterienbeladenen Deckschicht wurden entwickelt. NIR-Licht erwärmte die untere Schicht, diffundierende Wärme induzierte mCherry-Expression in E. coli. Temperatur- und Fluoreszenzanalysen zeigten eine gezielte bakterielle Aktivierung und eine photothermisch steuerbare Proteinproduktion. Das System wurde zur Produktion des angiogenen QK-Peptids in einem einschichtigen Hydrogel adaptiert, und die Sekretion über Nanoluciferase verfolgt. Der Ansatz wurde auf NIR-sensibilisierte nanokomposite PluDA-Hydrogele erweitert, die von einem Partner in 3D-gedruckte Wellenleiter integriert wurden. Segmentierte Fasern ermöglichten lokalisierte Erwärmung und zeigten gezielte plasmonische Erwärmung. Dies erlaubt eine NIR-gesteuerte bakterielle Aktivierung in tiefen Gewebeschichten und bietet einen neuen Ansatz für therapeutische ELMs
Multiple levels, multiple streams: how border regions made it into the Treaty of Aix‑la‑Chapelle
Get PDFThe Treaty of Aix-la-Chapelle, signed in 2019 by the French President Macron and
the German Chancellor Merkel, is widely seen as a major step for border regions
on their way towards being fully acknowledged as political entities. However,
while much ink has been spilled on the relevance of the treaty for future cross border cooperation, we know surprisingly little about how that particular aspect
actually became the Chapter 4 of the treaty. Given the centralized architecture of
the French 5th republic, the new stipulations are actually a giant’s leap, which is
difficult to explain. In this paper, we draw on evidence from policy documents and
expert interviews to trace how cross-border cooperation was set on the government’s
agendas as an issue to be integrated in the Aix-la-Chapelle Treaty. Building on the
Multiple Streams Framework as theoretical lens, our analysis shows that actors from
the French and German border regions were instrumental for the inclusion of cross border cooperation in the Treaty. They used different channels in the multi-level
system to push both central governments towards the integration of cross-border
cooperation. Hence, the story how border regions made it into the Aix-la-Chapelle
Treaty is a prime example of the dynamics of multi-level governance
Business Process Management and Artificial Intelligence : Literature Survey and Future Research
Get PDFThe field of Business Process Management (BPM) has several academic roots, in particular management science and informatics. In particular at the intersection of BPM and Artificial Intelligence (AI), a vibrant interdisciplinary field of research evolved. In this survey, we review prior work from three perspectives, namely, (a) from the perspective of BPM we focus on modeling, analysis, redesign, implementation, and monitoring of processes; (b) from the perspective of AI we focus on natural language processing, knowledge representation, automated reasoning, machine learning, computer vision, and robotics; (c) from the perspective of application domains we focus on domains such as process-aware information systems, manufacturing, and healthcare. Additionally, we discuss future research challenges and opportunities
Efficient treatment of long-range electrostatics in charge equilibration approaches
Get PDFA charge equilibration method based on real-space Gaussians as charge densities is presented. The implementation is part of the Elec trode package available in the Large-scale Atomic/Molecular Massively Parallel Simulator and benefits from its efficient particle-mesh Ewald
approach. A simple strategy required to switch from the previously used Slater-type orbital (STO) shielding to Gaussians is provided by fitting
the Coulomb energy of two Gaussian charge distributions to the repulsion between two STOs. Their widths were optimized for O, Si, and
Ti species, obtaining results consistent with previous studies using STOs in the case of SiO2 polymorphs. In the limit of sufficiently narrow
Gaussians, it is shown that the implementation converges to electronegativity equalization method results for the case of Ti/TiOx interfaces.
The method presented is implemented in a way that is potentially beneficial for the application of modern machine-learning force fields that
include long-range electrostatic interactions
Drug Coated Balloon in Young Patients With ST-Elevation Myocardial Infarction: A Viable Treatment Option?
Get PDFThis clinical case highlights the safety and feasibility of drug coated balloon (DCB) angioplasty in a very young patients presenting with STEMI (ST-Elevation Myocardial Infarction) to avoid long-term complications associated with stent implantation, which still amount to 1%−2%. We successfully treated a 25 years old patient with occluded right coronary artery (RCA) with DCB after careful lesion preparation. Moreover, in a control angiogram 7 weeks later the RCA was patent with substantial lumen enlargement of 0.4 mm (RAO projection) to almost 2 mm (LAO projection) in a very short period of time. DCB angioplasty offers a viable alternative to stent implantation in young patients, avoiding the complications associated with permanent metallic implants while promoting vascular remodeling. While we acknowledge that more evidence is needed to optimize patient selection and confirm the long-term benefits of DCB in ACS, this case highlights its efficacy and safety in terms of an individualized treatment strategy