Made to measure: Easy Synthesis and Characterization of Nanocomposites with Tailored Functionalities for Chemistry Education

By adding nanoparticles to classical polymer systems, new functional materials with tailored properties can be obtained. The great variety of possibilities opens up just as many interesting fields of application for industry and science. Following on from this, this article will present how the classical educational subject area of polymers can be extended by a current research context. In a series of experiments, students are using inexpensive chemicals and simple materials from the hardware store to produce nanocomposites that have a much greater hardness or antimicrobial activity than polymers alone. Their properties can then be investigated using a simple test method. Overall, it will be illustrated, that the combination of polymer chemistry and nanotechnology offers a variety of learning opportunities and questions with curricular relevance for schools and student laboratories

Complexation of Zr and Hf in fluoride-rich hydrothermal aqueous fluids and its significance for high field strength element fractionation

Zirconium and hafnium behave nearly identically in most geological processes due to their identical nominal ionic charge and similar radius. Some of the most pronounced exceptions from this rule are observed in fluoride-rich aqueous systems, suggesting that aqueous fluoride complexation may be involved in Zr/Hf fractionation. To understand the mechanisms causing this phenomenon, we investigated complexation of Zr4+ and Hf4+ in fluoride-rich (1.0 mol/kg HF) aqueous solutions at 40 MPa and 100–400 °C, using synchrotron X-ray absorption spectroscopy (X-ray absorption near edge structure and extended X-ray absorption fine structure) combined with classical and ab initio molecular dynamics simulations. The dominant experimentally observed complexes are [Zr(F,OH)4·2H2O]0 and [Hf(F,OH)4·2H2O]0, respectively. The first coordination shell comprises a distorted octahedron, with fluoride and hydroxide ligands at a similar mean radial distance (1.9–2.0 Å) from the central cation, and H2O ligands at a slightly greater distance (>2.1 Å). With increasing temperature, the H2O ligands move further out, causing first an increasing distortion of the octahedron and subsequently a partial transition to less hydrated complexes as a certain fraction of the H2O molecules move to the second shell at > 3 Å. As a consequence, the radial distance of the F- and OH– anions from the central cation, as well as the overall average radial distance of the first shell decreases due to decreased steric repulsion from the H2O ligands. Both experiments and simulations agree in that Hf forms slightly shorter bonds to its nearest neighbors than Zr. The results suggest two hypotheses for the mechanism of Zr/Hf fractionation during precipitation of minerals from fluoride-rich hydrothermal solutions: 1) The heavy twin (Hf) prefers the lower coordination (shorter bonds) and is thus less likely to enter into the higher coordination found in the solids. This mechanism would be analogous to equilibrium isotope fractionation. 2) The change of Hf into a higher coordination environment (e.g., from solution to solid) is slower because it forms stronger ligand-bonds than Zr. This would be analogous to reactive kinetic isotope fractionation. In either case mass dependent fractionation qualitatively matches the observations but mass independent effects on bond strength may also be significant. Quantitative investigations of these effects are needed and may also shed light on the currently still somewhat enigmatic fractionation behavior of Zr isotopes

Phocine Distemper in German Seals, 2002

Approximately 21,700 seals died during a morbillivirus epidemic in northwestern Europe in 2002. Phocine distemper virus 1 was isolated from seals in German waters. The sequence of the P gene showed 97% identity with the Dutch virus isolated in 1988. There was 100% identity with the Dutch isolate from 2002 and a single nucleotide mismatch with the Danish isolate

Virus Replication as a Phenotypic Version of Polynucleotide Evolution

In this paper we revisit and adapt to viral evolution an approach based on the theory of branching process advanced by Demetrius, Schuster and Sigmund ("Polynucleotide evolution and branching processes", Bull. Math. Biol. 46 (1985) 239-262), in their study of polynucleotide evolution. By taking into account beneficial effects we obtain a non-trivial multivariate generalization of their single-type branching process model. Perturbative techniques allows us to obtain analytical asymptotic expressions for the main global parameters of the model which lead to the following rigorous results: (i) a new criterion for "no sure extinction", (ii) a generalization and proof, for this particular class of models, of the lethal mutagenesis criterion proposed by Bull, Sanju\'an and Wilke ("Theory of lethal mutagenesis for viruses", J. Virology 18 (2007) 2930-2939), (iii) a new proposal for the notion of relaxation time with a quantitative prescription for its evaluation, (iv) the quantitative description of the evolution of the expected values in in four distinct "stages": extinction threshold, lethal mutagenesis, stationary "equilibrium" and transient. Finally, based on these quantitative results we are able to draw some qualitative conclusions.Comment: 23 pages, 1 figure, 2 tables. arXiv admin note: substantial text overlap with arXiv:1110.336

Convalescent plasma treatment for SARS-CoV-2 infected high-risk patients: a matched pair analysis to the LEOSS cohort

Establishing the optimal treatment for COVID-19 patients remains challenging. Specifically, immunocompromised and pre-diseased patients are at high risk for severe disease course and face limited therapeutic options. Convalescent plasma (CP) has been considered as therapeutic approach, but reliable data are lacking, especially for high-risk patients. We performed a retrospective analysis of 55 hospitalized COVID-19 patients from University Hospital Duesseldorf (UKD) at high risk for disease progression, in a substantial proportion due to immunosuppression from cancer, solid organ transplantation, autoimmune disease, dialysis. A matched-pairs analysis (1:4) was performed with 220 patients from the Lean European Open Survey on SARS-CoV-2-infected Patients (LEOSS) who were treated or not treated with CP. Both cohorts had high mortality (UKD 41.8%, LEOSS 34.1%). A matched-pairs analysis showed no significant effect on mortality. CP administration before the formation of pulmonary infiltrates showed the lowest mortality in both cohorts (10%), whereas mortality in the complicated phase was 27.8%. CP administration during the critical phase revealed the highest mortality: UKD 60.9%, LEOSS 48.3%. In our cohort of COVID-19 patients with severe comorbidities CP did not significantly reduce mortality in a retrospective matched-pairs analysis. However, our data supports the concept that a reduction in mortality is achievable by early CP administration

1. Vorlesung (02.11.2020): Einführung und Modulübersicht

Vorlesungsinhalt: Organisatorisches; Vorlesungen; Seminar + Praktikum; Ablaufpla

1. Vorlesung (04.11.2020): Einführung und Modulübersicht

Vorlesungsinhalt: Vorstellung; Semesterplan; Leistungsanforderungen; Vorlesung; Praktiku

Conceptualization of "Nano" for School Chemistry Education

In der heutigen Zeit wie auch in der Zukunft steht die Menschheit vor dem Hintergrund einer rapide steigenden Weltbevölkerung und dem Klimawandel vor vielfältigen gesellschaftlichen Herausforderungen. Die Nanowissenschaften bzw. –technologie stellen hierbei ein aktuelles und bedeutendes Forschungsfeld dar, dem ein signifikanter Beitrag zur Bewältigung dieser Problemstellungen zugeschrieben wird. Ungeachtet ihrer großen Bedeutung in Wirtschaft, Wissenschaft und Gesellschaft werden Inhalte aus diesem Themenfeld bislang jedoch nur zögerlich in formale und non-formale Bildungszusammenhänge implementiert. Dies eröffnet eine Reihe von Fragestellungen, allen voran ob dieses Thema für eine Vermittlung außerhalb der Universität geeignet ist und auf welche Weise es didaktisch aufgearbeitet werden kann. Anknüpfend hieran soll in der vorliegenden Arbeit zunächst aus verschiedenen Blickwinkeln untersucht werden, welches Potenzial die Nanotechnologie für eine Vermittlung in Schule, Schülerlabor und Hochschule bietet. Hierbei wird herausgestellt, dass die Nanowissenschaften vielfältige Chancen für den Chemieunterricht bieten.  Aufbauend auf diese Grundlage werden anschließend Beiträge zur fachdidaktischen Konzeptualisierung dieses Themenfeldes vorgestellt. Im Rahmen einer didaktischen Rekonstruktion, welche den methodischen Rahmen der Konzeptualisierung bereitstellt, wird hierbei eine Klärung der Sachstruktur vorgenommen, um die elementaren Konzepte für eine Vermittlung herauszustellen. Von ebenso großer Bedeutung sind darüber hinaus die Perspektiven und Präkonzepte von Lernenden und Lehrenden, welche ebenso wie intrinsische und extrinsische Barrieren für eine unterrichtliche Behandlung empirisch erhoben bzw. identifiziert werden sollen.  Die ermittelten fachlichen Konzepte sowie die Perspektiven der Lernenden und Lehrenden werden schließlich miteinander verknüpft, sodass hieraus Leitlinien für die didaktische Strukturierung abgeleitet werden. Auf dieser Basis werden in dem Hauptteil der vorliegenden Arbeit nun in einem zyklischen Design Konzepte, Unterrichtseinheiten, –materialien sowie Lehrangebote für Schulen, Schülerlabore und Lehrer(fort)bildungen entwickelt, praktisch durchgeführt, evaluiert und weiter optimiert. Die Forschungs- und Entwicklungsarbeit wird dabei systematisch und in Anlehnung an die Basiskonzepte der Chemie erfolgen, um einen optimalen Anschluss an die Bildungsstandards bundesdeutscher Kerncurricula zu gewährleisten.

2. Vorlesung (09.11.2020): Trinkwasser

Vorlesungsinhalt: Vorkommen und Qualität; natürliche und menschliche Verunreinigung; Gewinnung und Aufreinigun

3. Vorlesung (11.11.2020): Energie

Vorlesungsinhalt: Energiebedarf und -verbrauch; Regenerative Energiequellen; Beispiel - Wasserstoff-Strategie; Mobilität - Antriebskonzepte und Kraftstoffgewinnun