Bergische Universität Wuppertal
Recent publications
A method for the synthesis of benzoic acids from aryl iodides using two of the most abundant and sustainable feedstocks, carbon dioxide (CO2) and water, is disclosed. Central to this method is an effective and selective electrochemical reduction of CO2 (eCO2RR) to CO, which mitigates unwanted dehalogenation reactions occurring when H2 is produced via the hydrogen evolution reaction (HER). In a 3‐compartment set‐up, CO2 was reduced to CO electrochemically by using a surface‐modified silver electrode in aqueous electrolyte. The ex‐situ generated CO further underwent hydroxycarbonylation of aryl iodides by MOF‐supported palladium catalyst in excellent yields at room temperature. The method avoids the direct handling of hazardous CO gas and gives a wide range of benzoic acid derivatives. Both components of the tandem system can be recycled for several consecutive runs while keeping a high catalytic activity.
NiAl bi‐ and trilayers are prepared by alternating evaporation of aluminum and nickel on float glass substrates under high vacuum, with individual layer thicknesses between 20 and 100 nm. The samples are subjected to an annealing procedure to temperatures of up to 300 °C in vacuum, and the structural changes induced by the heat treatments are followed by in situ grazing incidence X‐ray absorption spectroscopy experiments at the Ni K‐edge. The results show that the elemental metallic deposits are stable up to 180 °C, while a slow formation of the intermetallic NiAl compound occurs at temperatures above 200 °C. No additional reaction intermediates are detected. Linear combination fits employing spectra of face‐centered metallic Ni and body‐centered NiAl as references allow to quantify the contributions of the respective phases as a function of the temperature and the depth in the multilayer. In general, an increase of the phase fraction of the intermetallic NiAl phase is detected. While the deposited elemental metals cannot completely be transformed into this intermetallic compound for the Al–Ni bilayer system even after prolonged annealing at 240 °C, the analysis of the spectra of the Al–Ni–Al trilayer suggests almost complete conversion to NiAl with body‐centered‐cubic structure.
Materials combining topologically non‐trivial behavior and superconductivity offer a potential route for quantum computation. However, the set of available materials intrinsically realizing these properties are scarce. Recently, surface superconductivity has been reported in PtBi2 in its trigonal phase and an inherent Weyl semimetal phase has been predicted. Here, based on scanning tunneling microscopy experiments, the signature of topological Fermi arcs are revealed in the normal state patterns of the quasiparticle interference. It is shown that the scattering between Fermi arcs dominates the interference spectra, providing conclusive evidence for the relevance of Weyl fermiology for the surface electronic properties of trigonal PtBi2.
The antimicrobial properties of silver ions are well known and effectively utilized in various biomedical applications. The efficacy of silver‐containing materials, particularly in terms of antimicrobial activity, heavily relies on the oxidizing surface, favoring nanosized silver features. However, producing such structures is challenging due to the high probability of miscibility in the liquid phase. Developing Ti–Ag composite alloys using the laser powder bed fusion technique with supported titanium powders and silver nanoparticles (AgNPs) represents a novel research pursuit, with no prior investigations reported. Incorporating AgNPs into titanium forms nanoislands, directly enhancing the antimicrobial efficacy of biomedical components. In this study, it is aimed to explore the solubility limit of silver in titanium and the feasibility of achieving finely dispersed silver islands. Experimental findings reveal that incorporating AgNPs into Ti‐based alloys results in discrete silver islands (0.01–0.02 μm²) within the microstructure, governed by the solubility limit of silver in titanium. In this study, valuable insights into producing components with augmented biocompatibility and proven antibacterial properties against Staphylococci infections are offered. The successful development of Ti–Ag composite alloys, featuring finely dispersed silver islands, opens promising avenues for biomedical applications, enhancing their antibacterial characteristics and improving patient outcomes.
Parallel zur Überarbeitung und Neuerscheinung der Produktnorm für Sandwichelemente EN 14509 soll als Teil der Normenreihe des Eurocode 3 demnächst die EN 1993‐7 für die Bemessung und Konstruktion von Sandwichelementen erscheinen. Nachfolgend werden anhand von Berechnungsbeispielen die Neuerungen in dieser Norm gegenüber dem Anhang E – Bemessungsverfahren der DIN EN 14509:2013‐12 vorgestellt und erläutert. In einem zusätzlichen Beispiel wird der Einfluss der seitlichen Stützung von Sandwichwandelementen auf Wandriegel untersucht.
Polyoxymethylene (POM) has been widely used as a gear material owing to its excellent mechanical properties. One of the key parameters that influence the tribological properties of POM is the operating temperature. In this study, the tribological properties of POM under different operating temperatures (25–110 °C) were studied. The results showed that the friction and wear coefficients tend to increase with increasing temperature. The adhesive wear is the primary wear mechanism influenced by temperature and the adhesive wear increases with an increased temperature. Material transfer was found for all the velocity and load settings.
Proximity logistics represent a counter movement to logistics sprawl-the return of logistics to urban areas. In the case presented, a logistics service provider in the groupage and less-than-truckload (LTL) segment runs an urban consolidation center (UCC), offers receiver-led consolidation and additional service like stockholding to inner-city businesses in the city of Dusseldorf. The case shows that for the development of a UCC or a proximity logistics facility to succeed, no expensive space is necessarily required in immediate inner-city areas. The transfer to other locations of logistics service providers of the same segment shows that these could serve as possible locations for UCC in terms of cargo-bike relevant distances. We, therefore, conclude that the relevant locations of logistics infrastructure like ports and centrally located logistics facilities should be seen as crucial for the transformation to sustainable freight transport and its initiation by municipal governments.
This paper offers a novel theoretical explanation for the gender gap in job satisfaction, where women typically report higher job satisfaction than men. We argue that rational family decisions can result in divergent job choices for women and men, leading to increased job satisfaction but lower earnings for women, even when their preferences and expectations align with those of men. We develop this explanation within a theoretical model of family household decision‐making that considers relative earnings disparities within households. We provide empirical evidence supporting our model's predictions utilizing survey and administrative data from Canada.
Background/Objectives: Weaning failure in elderly patients undergoing mechanical ventilation presents a complex clinical challenge due to age-related physiological changes and comorbidities. Understanding the dynamics of this phenomenon through systematic analysis can provide valuable insights for clinical management. This meta-analysis aims to investigate the factors contributing to weaning failure in elderly patients and to assess the efficacy of different strategies in mitigating this challenge. Design: The design of this study is a systematic review and meta-analysis. Methods: A systematic search of electronic databases was conducted to identify relevant studies focusing on weaning failure in elderly patients. Studies reporting outcomes related to mechanical ventilation weaning failure were included. Data extraction, quality assessment, and statistical analysis were performed following established guidelines. Results: A total of 15 studies met the inclusion criteria and were included in the meta-analysis. The average age of participants throughout the studies was 66.24 ± 10.21 years. This suggests that the study population largely consisted of older adults and displayed a moderate range of ages centered around the mean. The rate of weaning failure across these studies was slightly above 31.56%, indicating a significant occurrence of this complication in the patient cohorts. The analysis revealed age-related physiological changes, such as decreased respiratory muscle strength and increased chest wall stiffness, as significant contributors to weaning failure in elderly patients. Comorbidities, including chronic pulmonary diseases and cardiovascular conditions, further exacerbated the challenge. Various interventions, including tailored weaning protocols and respiratory therapies, showed promising results in improving weaning outcomes in this population. Conclusions: Weaning failure in elderly patients undergoing mechanical ventilation is influenced by a combination of age-related physiological changes and comorbidities. Tailored interventions addressing these factors are essential for optimizing weaning success rates in this vulnerable population. Further research is warranted to refine the strategies and enhance outcomes in elderly patients requiring mechanical ventilation.
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7,074 members
Matthias Ehrhardt
  • Department of Mathematik und Informatik
Michael Grosche
  • School of Education
Meinald Thielsch
  • Psychologie
Oliver Passon
  • School of Mathmatics and Natural Sciences
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Address
Wuppertal, Germany
Head of institution
Prof. Dr. Lambert T. Koch