Molecular Dynamics Simulations of Polymers and Micelles at Interfaces

Molekulardynamik (MD) Simulationen wurden an zwei verschiedenen Systemen durchgeführt: 1. Grenzfläche zwischen Polyethylen und isotaktischem Polypropylen (PE-iPP) und 2. Zylindrische Mizellen, bestehend aus Tetradecyltrimethylammoniumbromid (C14TAB), in wässriger Lösung und an Fest-Flüssig-Grenzflächen. Die allgemeinen Schwierigkeiten bei der Simulation von Grenzflächen kristalliner Polymere wurden diskutiert und eine Methode für solche Simulationen vorgeschlagen. Diese Methode wurde zur epitaxialen Kristallisation von PE auf iPP benutzt. Experimentelle Ergebnisse der epitaxialen Kristallisation konnten durch die Simulation bestätigt werden. Ferner konnte vorhergesagt werden, dass PE bevorzugt auf einer iPP-Oberfläche mit hoher Methylgruppenkonzentration kristallisiert. Ebenso wurde durch die MD Simulation vorhergesagt, dass PE in der Grenzflächenregion von einer orthorhombischen zur monoklinischen Kristallstruktur wechselt. Die Simulationsdauer für die Mizellen betrug einige Nanosekunden. Die Ergebnisse für die Mizellen in wässriger Lösung stehen hierbei in guter Übereinstimmung mit experimentellen Werten. Im Widerspruch zur allgemein üblichen Vorstellung führte die Simulation der Mizellen zur Ausbildung eines Hohlraums in ihrer Mitte sowie zu einer inhomogenen Dichte des hydrophoben Mizellkerns. Dies wurde zum Teil der inhomogenen Verteilung der terminalen Methylgruppen im Mizellkern zugeschrieben. Zylindrische und halbzylindrische Mizellen wurden an den Paraffin/Wasser- und Gold/Wasser-Grenzflächen simuliert.Molecular Dynamic (MD) simulation of two different systems was performed: 1) Polyethylene- isotactic Polypropylene (PE-iPP) interfaces and 2) cylindrical micelles formed by tetradecyl trimethylammonium bromide (C14TAB) molecules in aqueous solution and at solid liquid interfaces. The general difficulties of simulation of polymer crystalline interfaces were discussed and one method was proposed for such simulations. Thise method was used to simulate epitaxial crystallisation of PE on iPP. The experimental results on epitaxial crystallisation were confirmed by MD simulation and in addition epitaxial crystallisation of PE on iPP surface with high dencity of methyl groups was predicted. MD simulation also predicted that PE should change at the interfacial region from the orthorhombic to monoclinic crystalline structure. Several nanoseconds of life of cylindrical micelles were simulated. The simulation results for the micelle in aqueous solution were favourably compared with experimental results. In contradiction to the standard picture of an ionic micelle the simulated micelle formed hole in its centre and the density of the hydrophobic micelle core was inhomogeneous. This effect partially was explained by the inhomogeneous distribution of the terminal methyl groups in the micelle core. Cylindrical and half cylindrical micelles of C14TAB molecules were simulated at the paraffin- and gold-aqueous interfaces

Plasmonic rod dimers as elementary planar chiral meta-atoms

Electromagnetic response of metallic rod dimers is theoretically calculated for arbitrary planar arrangement of rods in the dimer. It is shown that dimers without an in-plane symmetry axis exhibit elliptical dichroism and act as "atoms" in planar chiral metamaterials. Due to a very simple geometry of the rod dimer, such planar metamaterials are much easier in fabrication than conventional split-ring or gammadion-type structures, and lend themselves to a simple analytical treatment based on coupled dipole model. Dependencies of metamaterial's directional asymmetry on the dimer's geometry are established analytically and confirmed in numerical simulations.Comment: 3 page

Bulk Nanocrystalline Thermoelectrics Based on Bi-Sb-Te Solid Solution

A nanopowder from p-Bi-Sb-Te with particles ~ 10 nm were fabricated by the ball milling using different technological modes. Cold and hot pressing at different conditions and also SPS process were used for consolidation of the powder into a bulk nanostructure and nanocomposites. The main factors allowing slowing-down of the growth of nanograins as a result of recrystallization are the reduction of the temperature and of the duration of the pressing, the increase of the pressure, as well as addition of small value additives (like MoS2, thermally expanded graphite or fullerenes). It was reached the thermoelectric figure of merit ZT=1.22 (at 360 K) in the bulk nanostructure Bi0,4Sb1,6Te3 fabricated by SPS method. Some mechanisms of the improvement of the thermoelectric efficiency in bulk nanocrystalline semiconductors based on BixSb2-xTe3 are studied theoretically. The reduction of nanograin size can lead to improvement of the thermoelectric figure of merit. The theoretical dependence of the electric and heat conductivities and the thermoelectric power as the function of nanograins size in BixSb2-xTe3 bulk nanostructure are quite accurately correlates with the experimental data.Comment: 35 pages, 24 figures, 4 tables, 52 reference

Triple-cation perovskite solar cells fabricated by hybrid PVD/blade coating process using green solvents

The scalability of highly efficient organic-inorganic perovskite solar cells (PSCs) is one of the remaining challenges of solar module manufacturing. Various scalable methods have been explored to strive for uniform perovskite films of high crystal quality on large-area substrates. However, each of these methods have individual drawbacks, limiting the successful commercialization of perovskite photovoltaics. Here, we report a fully scalable hybrid process, which combines vapor- and solution-based techniques to deposit high quality uniform perovskite films on large-area substrates. This two-step process does not use toxic solvents, and it further allows facile implementation of passivation strategies and additives. We fabricated PSCs based on this process and used blade coating to deposit both charge transporting layers (SnO2 and Spiro-OMeTAD) without hazardous solvents in ambient air. The fabricated PSCs have yielded open-circuit voltage up to 1.16 V and power conversion efficiency of 18.7 % with good uniformity on 5 cm x 5 cm substrates

No impact of sex on surgical site infections in abdominal surgery: a multi-center study.

OBJECTIVE Male sex is controversially discussed as a risk factor for surgical site infections (SSI). The aim of the present study was to evaluate the impact of sex on SSI in abdominal surgery under elimination of relevant confounders. METHODS Clinicopathological data of 6603 patients undergoing abdominal surgery from a multi-center prospective database of four Swiss hospitals including patients between 2015 and 2018 were assessed. Patients were stratified according to postoperative SSI and risk factors for SSI were identified using univariate and multivariate analysis. RESULTS In 649 of 6603 patients, SSI was reported (9.8%). SSI was significantly associated with reoperation (22.7% vs. 3.4%, p  75th percentile (57.0% vs. 17.9%, p  75th percentile (OR 2.3 [1.8-2.9]), high contamination level (OR 1.3 [1.0-1.6]), laparotomy (OR 1.3 [1.0-1.7]), previous laparotomy (OR 1.4 [1.1-1.7]), blood transfusion (OR 1.7 [1.2-2.4]), cancer (OR 1.3 [1.0-1.8] and malnutrition (OR 2.5 [1.8-3.4]). CONCLUSION Under elimination of relevant confounders, there is no significant correlation between sex and risk of SSI after abdominal surgery

Stable algorithm for event detection in event-driven particle dynamics : logical states

Acknowledgments: The authors gratefully acknowledge the support of the German Research Foundation (DFG) through the Cluster of Excellence ‘Engineering of Advanced Materials’ at the University of Erlangen-Nuremberg and through Grant Po 472/25.Peer reviewedPostprin

Extended states in 1D lattices: application to quasiperiodic copper-mean chain

The question of the conditions under which 1D systems support extended electronic eigenstates is addressed in a very general context. Using real space renormalisation group arguments we discuss the precise criteria for determining the entire spertrum of extended eigenstates and the corresponding eigenfunctions in disordered as well as quasiperiodic systems. For purposes of illustration we calculate a few selected eigenvalues and the corresponding extended eigenfunctions for the quasiperiodic copper-mean chain. So far, for the infinite copper-mean chain, only a single energy has been numerically shown to support an extended eigenstate [ You et al. (1991)] : we show analytically that there is in fact an infinite number of extended eigenstates in this lattice which form fragmented minibands.Comment: 10 pages + 2 figures available on request; LaTeX version 2.0

Combat sports elements to intensify physical training of police cadets

Objective of the study was to rate and analyze benefits of modern combat sports elements for physical training service at police academie