The International Chemistry Olympiad 2023 – A Glimpse Behind the Scenes

For the first time an International Chemistry Olympiad was hosted in Switzerland. A look behind the scenes shows some of the various challenges the organizers faced in the preparation and running of this event

A Twitter corpus and benchmark resources for german sentiment analysis

In this paper we present SB10k, a new corpus for sentiment analysis with approx.10,000 German tweets. We use this new corpus and two existing corpora to provide state-of-the-art bench-marks for sentiment analysis in German:we implemented a CNN (based on the winning system of SemEval-2016) and a feature-based SVM and compare their performance on all three corpora. For the CNN, we also created German word embeddings trained on 300M tweets. These word embeddings were then optimized for sentiment analysis using distant-supervised learning. The new corpus, the German word embeddings (plain and optimized), and source code to re-run the benchmarks are publicly available

Analysis of a viscoelastic phase separation model

A new model for viscoelastic phase separation is proposed, based on a systematically derived conservative two-fluid model. Dissipative effects are included by phenomenological viscoelastic terms. By construction, the model is consistent with the second law of thermodynamics, and we study well-posedness of the model, i.e., existence of weak solutions, a weak-strong uniqueness principle, and stability with respect to perturbations, which are proven by means of relative energy estimates. A good qualitative agreement with mesoscopic simulations is observed in numerical tests.Comment: 10 pages, 8 figure

Effects of face masks on performance and cardiorespiratory response in well-trained athletes

Background During the COVID-19 pandemic, compulsory masks became an integral part of outdoor sports such as jogging in crowded areas (e.g. city parks) as well as indoor sports in gyms and sports centers. This study, therefore, aimed to investigate the effects of medical face masks on performance and cardiorespiratory parameters in athletes. Methods In a randomized, cross-over design, 16 well-trained athletes (age 27 ± 7 years, peak oxygen consumption 56.2 ± 5.6 ml kg−1 min−1, maximum performance 5.1 ± 0.5 Watt kg−1) underwent three stepwise incremental exercise tests to exhaustion without mask (NM), with surgical mask (SM) and FFP2 mask (FFP2). Cardiorespiratory and metabolic responses were monitored by spiroergometry and blood lactate (BLa) testing throughout the tests. Results There was a large effect of masks on performance with a significant reduction of maximum performance with SM (355 ± 41 Watt) and FFP2 (364 ± 43 Watt) compared to NM (377 ± 40 Watt), respectively (p < 0.001; ηp2 = 0.50). A large interaction effect with a reduction of both oxygen consumption (p < 0.001; ηp2 = 0.34) and minute ventilation (p < 0.001; ηp2 = 0.39) was observed. At the termination of the test with SM 11 of 16 subjects reported acute dyspnea from the suction of the wet and deformed mask. No difference in performance was observed at the individual anaerobic threshold (p = 0.90). Conclusion Both SM and to a lesser extent FFP2 were associated with reduced maximum performance, minute ventilation, and oxygen consumption. For strenuous anaerobic exercise, an FFP2 mask may be preferred over an SM

Molecular mechanism of enzymatic chlorite detoxification: insights from structural and kinetic studies

The heme enzyme chlorite dismutase (Cld) degrades chlorite to chloride and dioxygen. Although the structure and steady-state kinetics of pentameric Clds have been elucidated, many questions remain, such as the mechanism of chlorite cleavage and the pH dependence of the reaction. Here, we present high resolution X-ray crystal structures of a dimeric Cld at pH 6.5 and 8.5, its fluoride and isothiocyanate complexes and the neutron structure at pH 9.0 together with the pH dependence of the Fe(III)/Fe(II) couple and the UV-vis and resonance Raman spectral features. We demonstrate that the distal Arg127 cannot act as proton acceptor and is fully ionized even at pH 9.0 ruling out its proposed role in dictating the pH dependence of chlorite degradation. Stopped-flow studies show that (i) Compound I and hypochlorite cannot recombine and (ii) Compound II is the immediately formed redox intermediate that dominates during reaction. Homolytic cleavage of chlorite is propose

Switzerland at the International Chemistry Olympiad 2022

At the remote International Chemistry Olympiad 2022 hosted by China, two outstanding students from Switzerland won one bronze medal and one honorable mention. A joint remote participation to the event of the delegations from Germany, Austria, and Switzerland could be realized in Basel with the support of the University of Basel. The International Chemistry Olympiad 2023 will be hosted at ETH Zurich. This will be the first time this annual event comes to Switzerland.ISSN:0009-429

Switzerland at the International Chemistry Olympiad 2022: Conference Report

At the remote International Chemistry Olympiad 2022 hosted by China, two outstanding students from Switzerland won one bronze medal and one honorable mention. A joint remote participation to the event of the delegations from Germany, Austria, and Switzerland could be realized in Basel with the support of the University of Basel. The International Chemistry Olympiad 2023 will be hosted at ETH Zurich. This itinerary will mark the first time this annual event comes to Switzerland

α-Diimine Synthesis via Titanium-Mediated Multicomponent Diimination of Alkynes with C-Nitrosos

α-Diimines are commonly used as supporting ligands for a variety of transition metal-catalyzed processes, most notably in α-olefin polymerization. They are also precursors to valuable synthetic targets, such as chiral 1,2-diamines. Their synthesis is usually performed through acid-catalyzed condensation of amines with α-diketones. Despite the simplicity of this approach, accessing unsymmetrical α-diimines is challenging. Herein, we report the Ti-mediated intermolecular diimination of alkynes to afford a variety of symmetrical and unsymmetrical α-diimines through the reaction of diazatitanacyclohexadiene intermediates with C-nitrosos. These diazatitanacycles can be readily accessed in situ via the multicomponent coupling of Ti≡NR imidos with alkynes and nitriles. The formation of α-diimines is achieved through formal [4+2]-cycloaddition of the C-nitroso to the Ti and γ- carbon of the diazatitanacyclohexadiene followed by two subsequent cycloreversion steps to eliminate nitrile and afford the α- diimine and a Ti oxo