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Cuntz–Pimsner algebras of partial automorphisms twisted by vector bundles I: Fixed point algebra, simplicity and the tracial state space
No full textWe associate a C*-algebra to a partial action of the integers acting on the base space of a vector bundle, using the framework of Cuntz–Pimsner algebras. We investigate the structure of the fixed point algebra under the canonical gauge action, and show that it arises from a continuous field of C*-algebras over the base space, generalizing results of Vasselli. We also analyze the ideal structure, and show that, for a free action, ideals correspond to open invariant subspaces of the base space. This shows that if the action is free and minimal, then the Cuntz–Pimsner algebra is simple. In the case of a line bundle, we establish a bijective correspondence between tracial states on the algebra and invariant measures on the base space. This generalizes results about the C*-algebras associated to
homeomorphisms twisted by vector bundles of Adamo, Archey, Forough, Georgescu, Jeong, Strung and Viola
Designing and Evaluating a Collaborative Business Model for Offshore Green Hydrogen Production Using Curtailed Wind Energy
No full textContext: The energy transition towards renewable energy sources is in full swing. Hydrogen is expected to play an important role as an energy carrier in this transition in hard-to-abate sectors such as the chemical and maritime industries. Hydrogen is commonly produced using coal and natural gas, respectively referred to as black and grey hydrogen. In contrast, renewable green hydrogen can be generated through electrolysis, a process that splits water into hydrogen and oxygen using electricity from sustainable sources. However, the business case for producing green hydrogen remains unviable and is hindered by high production costs, technological barriers, and policy uncertainty. A solution commonly suggested, but not yet implemented, is utilizing curtailed energy from offshore wind farms to produce green hydrogen. The increased congestion on the electricity grid in the Netherlands, combined with the expansion of offshore wind capacity, is leading to more frequent curtailments. However, due to the uncertainty and the complexity of aligning the interests of multiple actors, stakeholders remain hesitant to invest in offshore hydrogen production. This underscores the need for collaboration and a holistic assessment of the different costs and benefits associated, as well as a viability analysis to support informed decision-making.
Objective: Therefore, this research aims to develop a Collaborative Business Model (CBM) for offshore hydrogen production using curtailed wind energy in the Dutch North Sea and subsequently evaluate the viability of the CBM using a System Dynamics simulation model.
Research Design: This research adopts a Design Science Research methodology to create both the Collaborative Business Model and the System Dynamics model. Through a systematic literature review and a co-creation workshop with practitioners and various experts, the CBM was created using the Collaborative Business Model Matrix framework. Subsequently, the System Dynamics model was designed and validated through a focus group, which quantified costs and benefits and captured the dynamics between stakeholders, ultimately enabling scenario-based viability testing.
Results: The viability analysis revealed several key drivers of viability: a focused subsidy and attention to the industrial user, aimed at bridging the price gap between grey and green hydrogen; beneficial electricity pricing for the hydrogen producer; and enforcement of the renewable REDIII hydrogen targets. The CBM and SD models serve as reference models for future collaborations in the production of green hydrogen. Additionally, the method for evaluating the viability of the CBM was found to be useful and applicable in real-world contexts.
Conclusions: The use of curtailed offshore wind energy holds large potential to support green hydrogen production. Realizing the potential requires a structured collaboration among stakeholders and a targeted policy to incentivize producers and to generate a reliable demand. The proposed CBM and SD models can guide these future efforts, providing practical tools for designing and evaluating offshore hydrogen production initiatives
Different propensities for gate opening in gyrases and topoisomerase IV
No full textThe bacterial type IIA topoisomerases gyrase and topoisomerase IV (Topo IV) catalyze DNA supercoiling and decatenation (gyrase), or DNA relaxation and decatenation (Topo IV) in ATP-dependent reactions. Most bacteria contain both gyrase and Topo IV, which jointly remove torsional stress during replication: gyrase removes positive supercoils ahead of the replication fork, while Topo IV decatenates pre-catenanes behind the fork and the catenated daughter chromosomes. Some bacteria, including 'Mycobacterium tuberculosis', contain only a gyrase, which then needs to perform both reactions. The molecular determinants for the predominant activity of type IIA topoisomerases are unclear. We hypothesize that the prevalent activity is connected to the stabilities of the DNA- and C-gates. In a comparative single-molecule FRET study of 'Bacillus subtilis' and 'M. tuberculosis' gyrase and 'B. subtilis' Topo IV, we show that the DNA-gates are less stable than the C-gates in all three enzymes. The stabilities of the DNA-gates of gyrase and Topo IV are similar. Strikingly, the C-gates in both gyrases are highly stable, but the C-gate in Topo IV is markedly less stable. Our results suggest that the stability of the C-gate of type IIA topoisomerases is linked to their activities
Divergent Electrophysiologic Effects of Sacubitril in Digitalis- and Pinacidil-Related Shortened Repolarization: Experimental Evidence for Harmful Effects of Digitalis Glycosides
No full textBackground: Recent studies reported an abbreviation of cardiac repolarization induced by sacubitril. Thus, the purpose of this study was to evaluate the electrophysiologic effects of sacubitril in the presence of drugs that shorten the QT interval. Methods and Results: 25 rabbit hearts were retrogradely perfused. After generating baseline data, hearts were allocated to two groups. In the first group (n = 12), the IK,ATP opener pinacidil (1 µM) significantly reduced action potential duration at 90% of repolarization (APD90), QT intervals and effective refractory periods (ERP). Additional administration of sacubitril (5 µM) slightly reduced APD90. The digitalis glycoside ouabain (0.2 µM) significantly shortened repolarization duration and refractory periods. Additional infusion of sacubitril abbreviated repolarization duration and ERP. Ventricular vulnerability was assessed by delivering premature extra stimuli and burst stimulation. Significantly more ventricular arrhythmias occurred with pinacidil (26 episodes vs. 5 episodes under baseline conditions, p < 0.05). Additional sacubitril treatment had no significant proarrhythmic effect (24 episodes). Ouabain alone did not provoke ventricular arrhythmias (6 episodes vs. 3 under baseline conditions, p = ns) whereas additional sacubitril treatment significantly increased the occurrence of VT episodes (29 episodes, p < 0.01). Conclusions: Sacubitril abbreviates cardiac repolarization in ouabain-pretreated hearts. While sacubitril had no proarrhythmic effect in the presence of pinacidil, the combination of sacubitril and ouabain amplified the arrhythmic risk. The underlying mechanism is a further abbreviation of refractory periods and cardiac repolarization that facilitate ventricular arrhythmias. These findings add further evidence to the proarrhythmic capacity of digitalis glycosides in the presence of other drugs that influence cardiac repolarization
Experiences and Plans for AI in Teaching and Performance Assessment
No full textDie Entwicklung der Künstlichen Intelligenz (KI) hat insbesondere bei Sprachmodellen große
Fortschritte gemacht, die auch Auswirkungen auf Hochschulen haben. Hier wird über die
bislang begrenzten Erfahrungen des Instituts für Organisationsökonomik an der Universität
Münster hinsichtlich KI in der Lehre und bei Leistungsbeurteilungen berichtet und werden
diesbezügliche Pläne für die Zukunft vorgestellt.The development of artificial intelligence (AI) has made significant progress, particularly in
large language models, which also has implications for higher education. This discussion
paper reports on the limited experience of the Institute for Organisational Economics at the
University of Münster with AI in teaching and performance assessment and presents future
plans in this regard
