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On the subloading surface model for metals: some insights and an efficient numerical implementation
No full textIn this work, we revisit the subloading surface model, as well as its extended version. By investigating its original formulation, we provide an alternative interpretation. With which, it is shown that the corresponding evolution rules of historic variables can be greatly simplified. The proposed evolution rules are analytically more concise and possess straightforward implications that can be easily illustrated while remain mathematically equivalent to the original ones. Based on the new proposal, an implicit numerical algorithm is presented. Compared to the previous implementation, the new algorithm is more efficient and robust. Additional insights regarding the unconventional (un)loading criterion and the specific form of some functions are also discussed.Open Access funding enabled and organized by Projekt DEAL.Humboldt-Universität zu Berlin (1034)Peer Reviewe
Sentencing procedures under the adversarial and inquisitorial models of justice: a comparative analysis
No full textThis article examines the key procedural distinction in sentencing between adversarial (common law) and inquisitorial (civil law) systems: bifurcation versus unification. Common law jurisdictions separate sentencing from the trial phase, while civil law systems integrate sentencing within the verdict determination. The article examines the implications of these approaches and assesses their strengths and weaknesses. Bifurcation allows for a focused mitigation hearing, ensures that all relevant information is considered prior to sentencing, and minimises potential bias from prior convictions or sentencing factors during trial. However, it also prolongs proceedings and can lead to inefficiencies. By contrast, unified sentencing integrates all relevant factors into a single hearing, streamlining the process but potentially exposing defendants to prejudicial considerations before a verdict is reached. While neither tradition is likely to fully abandon its approach, the authors suggest that if a new jurisdiction were to adopt a sentencing model, the adversarial system—with modifications to increase efficiency—would be preferable. They conclude by calling for further empirical research to assess the comparative impact of these systems on sentencing outcomes and perceptions of fairness.Peer Reviewe
Silanes and stannanes as tools in the activation and derivatization of fluorinated organic compounds
No full textDie Arbeit umfasst die Aktivierung und Derivatisierung fluorierter organischer Verbindungen unter Verwendung von Silan- und Stannanverbindungen. Chlorodefluorierung von Fluormethanen und Fluoralkenen wird von Aluminiumchlorofluorid (ACF) in Verbindung mit ClSiEt3 katalysiert und liefert hohe Ausbeuten. Verschiedene Fluormethane, die durch silyliumartige Spezies in C6D12-Lösung aktiviert werden, können in Chloromethane umgewandelt werden, während polyfluorierte Alkene, zu Chloroverbindungen überführt werden.Die Rolle von Silanverbindungen bei der C-F-Aktivierung wird weiter durch Hydrodefluorierungsreaktionen von Fluoralkanen beschrieben. Der Einfluss verschiedener Gruppe-14-Verbindungen auf katalytische Reaktionen wird beleuchtet. Fluoralkane mit unterschiedlichen Kettenlängen werden untersucht, wobei Fluorpentane, katalysiert von ACF in Gegenwart von HSnBu3, Dehydrofluorierungsreaktionen zu Pentenen mit bemerkenswerten Ausbeuten durchlaufen. Darüber hinaus beeinflusst die Wahl des Lösungsmittels die Ausbeuten sowohl von Mono- als auch von Polyfluoralkanen. Analog zu anderen Gruppe-14-Verbindungen fungieren stannyliumartige Spezies als Initiatoren für die C-F-Bindungsaktivierung nach der Immobilisierung an der Oberfläche von ACF. Die Derivatisierungsreaktion unter Verwendung von Gruppe-14-Verbindungen stellt eine vielversprechende Strategie dar, um den Nutzen flourhaltiger Verbindungen aufzuzeigen. Die Stille-Kupplungsreaktion unter Verwendung von HSnBu3 bei der Derivatisierung von Alkenen und Alkinen wird erforscht. Bei Photokatalyse zeigen verschiedene Fluoropropene eine äußerst hohe Umwandlung in Hydrostannierungsprodukte. Die resultierenden Hydrostannierungsprodukte von 1,1,1,4,4,4-Hexafluorbutin werden konsekutiv in Stille-Kreuzkupplungsreaktionen verwendet, welche zufriedenstellende Ausbeuten innerhalb kurzer Reaktionszeiten liefern. Diese Derivatisierungsreaktion zeigt einen Weg zur Herstellung fluorhaltiger organischer Verbindungen auf.The focus of this thesis encompasses the activation and derivatization of fluorinated organic compounds utilizing silane and stannane compounds. Chlorodefluorination reactions of fluoromethanes and fluoroalkenes are catalyzed with notable yields by aluminum chlorofluoride (ACF) in the presence of ClSiEt3. Different fluoromethanes exhibit robust conversion to chloromethanes activated by silylium-like species in C6D12 solvent, while polyfluorinated alkenes undergo activation into chloro compounds. Notably, isomeric forms of pentafluoropropenes yield satisfying yields using Chloro silane. The role of silane compounds in C-F activation is delineated through hydrodefluorination reactions of fluoroalkanes. The impact of Group 14 compounds on catalytic reactions is explored. Fluoroalkanes with varying chain length are investigated, revealing that fluoropentanes, catalyzed by ACF in the presence of HSnBu3, undergo dehydrofluorination reactions into pentenes with notable yields. Moreover, the choice of solvent influences the yields of both mono- and polyfluorinated alkanes. Analogous to other Group 14 compounds, stannylium-like species serve as initiators for C-F bond activation after the immobilisation on the surface of ACF. Derivatization reaction by Group 14 compounds is a favorable strategy to understand the utility of fluorinated compounds. Stille coupling reaction using HSnBu3 in derivatization reaction of fluorinated alkenes and alkynes is studied. Different fluoropropenes exhibit extremely high conversion to hydrostannation products by photocatalysis. The ensuing hydrostannation products of 1,1,1,4,4,4-hexafluorobutyne are consecutively used in Stille cross-coupling reaction with satisfying yield under ambient conditions within a short time. This derivatization reaction creates a path for accessing fluorine-containing organic compounds
Dynamics and Stability of Inverter Dominated Power Grids
No full textDer Wandel zu erneuerbaren Energien transformiert Stromnetze und stellt ihre Stabilität vor neue Herausforderungen. Netzbildende Wechselrichter gelten als Schlüsseltechnologie, doch ihre kollektive Dynamik ist bislang unzureichend verstanden. Herkömmliche Modelle sind rechenintensiv und verhindern probabilistische Analysen. Diese Arbeit entwickelt neue Werkzeuge, die nichtlineare und probabilistische Methoden integrieren. Ein zentraler Beitrag ist die Erweiterung der Normalform, eines technologieneutralen Modells für die Dynamik netzbildender Komponenten. Ich stelle eine Verbindung zur komplexen Frequenz her, die viele Anwendungen ermöglicht. Aufbauend darauf wird eine Systemidentifizierung entwickelt, um die Normalform für zwei Wechselrichter zu bestimmen: einen in EMT-Simulation, einen anhand von Labordaten. Die Ergebnisse bestätigen, dass die Normalform Wechselrichterdynamiken auch unter unbekannten Bedingungen zuverlässig erfasst. Zudem werden komplexe Kopplungen eingeführt, die eine Reformulierung von Stromnetzen als adaptive dynamische Netzwerke und control-affine Systeme erlauben. Am Beispiel von Kuramoto-Oszillatoren und der Normalform wird dies demonstriert. Durch grundlegende Theoreme wird eine global synchronisierende Regelung abgeleitet. Weiterhin wird ein Framework zur Generierung synthetischer Netze vorgestellt, das erstmals Topologie, Leistungssollwerte und dynamische Modelle kombiniert und auf deutschen Netzdaten basiert. Validierungen zeigen, dass die erzeugten Netze etablierte Stabilitätskriterien erfüllen und realistische Synchronisation und Robustheit aufweisen. Abschließend werden die entwickelten Methoden kombiniert, um Wechselrichter-dominierte Netze probabilistisch zu analysieren. Die Studien zeigen, wie algebraische Zwangsbedingungen, Topologie und nichtlineare Effekte die Stabilität beeinflussen. Die teils kontraintuitiven Ergebnisse stellen szenariobasierte Bewertungen infrage und unterstreichen den Bedarf moderner probabilistischer Ansätze.The transition to renewable energy reshapes power grids and introduces new stability challenges. Grid-forming inverters are seen as a key solution, yet their collective dynamics remain poorly understood. Traditional models are computationally demanding, hindering large-scale probabilistic analysis. This thesis develops efficient modeling and analysis tools that integrate nonlinear dynamics and probabilistic methods. A central contribution is the extension of the normal-form model, a technology-neutral framework for grid-forming devices. By establishing a link between the normal-form and complex frequency, this work enables new applications. Building on this, a system identification pipeline using complex frequency is introduced to identify the normal-form for two inverter types, using EMT simulations and laboratory data. Results confirm the model's ability to capture inverter dynamics across various conditions and generalize to unseen scenarios. Further, the thesis introduces complex couplings, allowing the reformulation of power grids as adaptive dynamical networks and control-affine systems. Demonstrations on Kuramoto oscillators and the normal-form illustrate the approach. Fundamental control theorems are used to derive a globally synchronizing control law. Additionally, a modular framework for generating realistic synthetic grids is developed, integrating topology, power set-points, and dynamic models based on openly available German grid data. The synthetic grids meet established stability criteria and exhibit strong synchronization and robustness, as expected. Finally, the developed methods are combined to study inverter-dominated grids using probabilistic stability analysis. Studies reveal how algebraic constraints, topology, and non-linear effects shape stability, uncovering new mechanisms and counterintuitive behaviors. The findings challenge traditional scenario-based approaches and underscore the need for modern probabilistic methods in stability assessment
Eine liminale Alteritätsfigur um 1920
No full textThe publication of this work was supported by the Open Access Publication Fund of Humboldt-Universität zu Berlin.Mit der Zeit ›um 1920‹, die hier ganz eng gefasst wird, verbindet sich nicht nur der Übergang vom Krieg zum Nachkrieg, sondern auch Revolution, Inflation, Hunger, politischer Systemwechsel und das Ausscheiden Deutschlands aus dem Kreis der Kolonialstaaten. In welcher Beziehung steht der zur politischen Schwellenzeit um 1920 so überaus dynamische Kannibalismusdiskurs mit der Funktionsweise des Kannibalischen als liminaler Alteritätsfigur, die ein in Bewegung geratenes Verhältnis von Eigenem und Anderem, von Außen und Innen, von Identifikation und Abstoßung erfasst? Untersucht werden u.a. Texte von Alfred Döblin und Linke Poot, Sigmund Freud, Theodor Lessing, Wilhelm Lamszus, Helenefriederike Stelzner, Franz Kafka, Artur Heye und Berta Lask. Die Studie leistet einen Beitrag zur Wissens- und Diskursgeschichte des Kannibalismus, zur postkolonialen Germanistik und zur Liminalitätsforschung
Correction of: Copper Paste Printed Paper-Based Dual-Band Antenna for Wearable Wireless Electronics
No full textThe article processing charge was funded by the Open Access Publication Fund of Humboldt-Universität zu Berlin.The authors regret an error in Figure 4 and Figure 7 of the published article and have provided corrected versions.Peer Reviewe
a systematic review and meta-analysis
No full textThe article processing charge was funded by the Open Access Publication Fund of Humboldt-Universität zu Berlin.Background: Hypoxic conditioning has emerged as a promising intervention for enhancing physiological adaptations. This systematic review and meta-analysis of randomized controlled trials aims to investigate the efficacy of hypoxic conditioning on physical fitness measures in aging populations.
Methods: The Embase, PubMed, Cochrane Library, and Web of Science were searched from inception to November 2024 (Prospero registration: CRD42023474570). The Cochrane Evaluation Tool and Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework were used for risk of bias assessment and evidence certainty evaluation. Mean differences (MD) and standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated using the Review Manager software. Subgroup analysis was performed to explore possible associations between the study characteristics and the effectiveness of the intervention.
Results: A total of 13 randomized controlled trials (RCTs) with 368 subjects were included in the meta-analysis. High certainty evidence found hypoxic conditioning (HC) significantly improved peak oxygen uptake (VO2peak) (SMD = 0.31, 95% CI [0.01-0.61]; P 0.05), muscle strength (SMD = -0.19, 95% CI [-0.63-0.26]; P > 0.05), maximal power output (SMD = 0.29, 95% CI [-0.17-0.76]; P > 0.05), VO2max (SMD = -0.39, 95% CI [-1.12-1.90]; P > 0.05), and exercise workload (MD = -10.07, 95% CI [-34.95-14.80]; P > 0.05).
Conclusion: This study suggests that hypoxia conditioning has a greater effect on enhancing VO2peak compared to equivalent normoxic training in the middle-aged and older population. More high-quality RCTs are needed in the future to explore the optimal oxygen concentration and exercise intensity during hypoxia conditioning.Peer Reviewe
Kernfach im Kombinationsstudiengang mit Lehramtsbezug - Zweitfach im Kombinationsstudiengang mit Lehramtsoption - Überfachlicher Wahlpflichtbereich für andere Bachelorstudiengänge und -studienfächer
No full textEcosystems in DMA designation decisions - Bridging the gap between legal text and economic reality
No full textA divide between legal text and economic reality characterizes the Digital Markets Act (DMA): whilst in the competition policy discourse ecosystems take a central role, they are absent in the legal text of the DMA. This leads to frictions and legal uncertainty in the DMA’s application as can been seen in the disparate use of ecosystem-related arguments in the Commission’s designation decisions. In this situation, the General Court brought some clarity in its ByteDance judgement by providing an ecosystem definition and clarifying some points with regard to which and how ecosystem-related arguments can be used in designation proceedings and what the respective standard of proof is. Nonetheless, many issue remain unresolved, letting us to conclude with a tentative outlook on things to come.Peer Reviewe
Understanding the Role of Varying Ti3C2Tx MXene in Ni/Ti3C2Tx for the Oxygen Evolution Reaction
No full textThe current state‐of‐the‐art catalysts for the oxygen evolution reaction (OER) in an anion exchange membrane (AEM) electrolyser are not efficient enough to surpass green H2 produced by other electrolyser technologies, such as Proton Exchange Membrane (PEM) electrolysers. One reason for this is due to the AEM catalysts not being active enough and lacking long‐term stability. In this work, we combine Ni based material with Ti3C2Tx MXene at different loadings (1, 5 and 10 %) to understand the effect of the MXene on the OER activity and stability. Our results show that the amount of MXene not only affects the OER performance, but the materials surface is also altered. Interestingly, the Ti3C2Tx is still present in the bulk for all composites but the surface of the composites contains different amounts of oxidized Ti3C2Tx i.e. TiO2. The optimum material in this study for the OER is the NiOx/1 %Ti3C2Tx which can be rationalized by the lower Ti/Ni ratio in the starting materials hence producing less overall surface TiO2 during OER. Additionally, when the pure NiOx and the 1 % Ni‐Ti3C2Tx are compared by operando Raman spectroscopy, the NiOx/1 %Ti3C2Tx exhibits β‐NiOOH at lower overpotentials, which is known to be present for efficient OER on Ni materials.Helmholtz Association's Initiative and Networking FundPeer Reviewe