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991.
992.
Dr. Benjamin Paschke Dr. Dmytro Denysenko Dr. Björn Bredenkötter Dr. German Sastre Prof. Dr. Achim Wixforth Prof. Dr. Dirk Volkmer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10803-10807
The separation of deuterium from hydrogen still remains a challenging and industrially relevant task. Compared to traditional cryogenic methods for separation, based on different boiling points of H2 and D2, the use of ultramicroporous materials offers a more efficient alternative method. Due to their rigid structures, permanently high porosity, tunable pore sizes and adjustable internal surface properties, metal–organic frameworks (MOFs), a class of porous materials built through the coordination between organic linkers and metal ions/clusters, are more suitable for this approach than zeolites or carbon-based materials. Herein, dynamic gas flow studies on H2/D2 quantum sieving in MFU-4, a metal-organic framework with ultra-narrow pores of 2.5 Å, are presented. A specially designed sensor with a very fast response based on surface acoustic waves is used. On-chip measurements of diffusion rates in the temperature range 27–207 K reveal a quantum sieving effect, with D2 diffusing faster than H2 below 64 K and the opposite selectivity above this temperature. The experimental results obtained are confirmed by molecular dynamic simulation regarding quantum sieving of H2 and D2 on MOFs for which a flexible framework approach was used for the first time. 相似文献
993.
994.
Ionics - Free-standing paper-like electrochemical sensors have many advantages such as high flexibility, thickness adjustability, and large electroactive surface area, when compared to traditional... 相似文献
995.
Francesco Aquilante Luca De Vico Nicolas Ferr Giovanni Ghigo Per‐ke Malmqvist Pavel Neogrdy Thomas Bondo Pedersen Michal Pitok Markus Reiher Bjrn O. Roos Luis Serrano‐Andrs Miroslav Urban Valera Veryazov Roland Lindh 《Journal of computational chemistry》2010,31(1):224-247
Some of the new unique features of the MOLCAS quantum chemistry package version 7 are presented in this report. In particular, the Cholesky decomposition method applied to some quantum chemical methods is described. This approach is used both in the context of a straight forward approximation of the two‐electron integrals and in the generation of so‐called auxiliary basis sets. The article describes how the method is implemented for most known wave functions models: self‐consistent field, density functional theory, 2nd order perturbation theory, complete‐active space self‐consistent field multiconfigurational reference 2nd order perturbation theory, and coupled‐cluster methods. The report further elaborates on the implementation of a restricted‐active space self‐consistent field reference function in conjunction with 2nd order perturbation theory. The average atomic natural orbital basis for relativistic calculations, covering the whole periodic table, are described and associated unique properties are demonstrated. Furthermore, the use of the arbitrary order Douglas‐Kroll‐Hess transformation for one‐component relativistic calculations and its implementation are discussed. This section especially focuses on the implementation of the so‐called picture‐change‐free atomic orbital property integrals. Moreover, the ElectroStatic Potential Fitted scheme, a version of a quantum mechanics/molecular mechanics hybrid method implemented in MOLCAS, is described and discussed. Finally, the report discusses the use of the MOLCAS package for advanced studies of photo chemical phenomena and the usefulness of the algorithms for constrained geometry optimization in MOLCAS in association with such studies. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献
996.
Localized planar patterns arise in many reaction-diffusion models. Most of the paradigm equations that have been studied so
far are two-component models. While stationary localized structures are often found to be stable in such systems, travelling
patterns either do not exist or are found to be unstable. In contrast, numerical simulations indicate that localized travelling
structures can be stable in three-component systems. As a first step towards explaining this phenomenon, a planar singularly
perturbed three-component reaction-diffusion system that arises in the context of gas-discharge systems is analysed in this
paper. Using geometric singular perturbation theory, the existence and stability regions of radially symmetric stationary
spot solutions are delineated and, in particular, stable spots are shown to exist in appropriate parameter regimes. This result
opens up the possibility of identifying and analysing drift and Hopf bifurcations, and their criticality, from the stationary
spots described here. 相似文献
997.
The strength properties of interfibre bonds play a vital role in the response of fibrous materials, such as paper and paperboard, under mechanical loading. To help tailor the properties of such materials by chemical or mechanical treatments of the fibre wall and fibre surfaces, improved understanding of the microscopic damage and failure mechanisms of interfibre joints is desirable. In this paper, a method for manufacturing and testing of interfibre joint specimens in two principally different modes of loading is presented. The method was applied to investigate the strength of Kraft pulp interfibre joints with different geometries and in two different modes of loading: the conventional shearing mode and also a peeling mode of loading. The method was also used to investigate the influence of drying pressure, defined as the nominal pressure between two Teflon surfaces or between a rubber surface and a Teflon one as well as a simple comparison of a pulp with two different degrees of refining. The results are presented in terms of rupture force and using different methods of normalization such as nominal overlap area, length, and width of the joint region, measured using a microscope. It was shown in this study that normalising the force at rupture by either geometric parameter reduced the scatter of the strength measurements slightly, but, neither were unambiguously more successful than the other. The results of tests done with the peeling type of loading were about 20 % of those done with the conventional shearing type of loading. 相似文献
998.
Phosphorus‐nitrogen compounds. Part 39. Syntheses and Langmuir‐Blodgett thin films and antimicrobial activities of N/N and N/O spirocyclotriphosphazenes with monoferrocenyl pendant arm
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Nuran Asmafiliz Mehmet Civan Arda Özben Zeynel Kılıç Nagehan Ramazanoğlu Leyla Açık Tuncer Hökelek 《应用有机金属化学》2018,32(4)
The Cl substitution reactions of the N/N ( 1 ‐ 3 ) and N/O ( 4 and 5 ) spirocyclic monoferrocenylphosphazenes with 1,4‐dioxa‐8‐azaspiro[4,5]decane (DASD) produce the mono‐ ( 1a ‐ 5a ), geminal‐ ( 1b ‐ 5b ) and tetrakis‐DASD‐substituted ferrocenylspirocyclotriphosphazenes ( 1c ‐ 5c ). The mono‐ and geminal‐DASD‐substituted phosphazenes have two and one stereogenic P‐centers, respectively. The structures of the compounds were established by spectroscopic techniques. The molecular structures of 3a and 2b were evaluated using X‐ray crystallography. Additionally, the ultrathin and highly ordered Langmuir‐Blodgett (LB) films of 3a and 2b were also prepared. The characterizations of the LB films were done using p‐polarized grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques. On the other hand, the antimicrobial activities of the eight phosphazene derivatives against G(+) and G(‐) bacteria and fungi were investigated. Furthermore, the interactions between the compounds and plasmid DNA were studied by agarose gel electrophoresis. 相似文献
999.
A novel wetting and drying treatment for second-order Runge-Kutta discontinuous Galerkin methods solving the nonlinear shallow-water equations is proposed. It is developed for general conforming two-dimensional triangular meshes and utilizes a slope limiting strategy to accurately model inundation. The method features a nondestructive limiter, which concurrently meets the requirements for linear stability and wetting and drying. It further combines existing approaches for positivity preservation and well balancing with an innovative velocity-based limiting of the momentum. This limiting controls spurious velocities in the vicinity of the wet/dry interface. It leads to a computationally stable and robust scheme, even on unstructured grids, and allows for large time steps in combination with explicit time integrators. The scheme comprises only one free parameter, to which it is not sensitive in terms of stability. A number of numerical test cases, ranging from analytical tests to near-realistic laboratory benchmarks, demonstrate the performance of the method for inundation applications. In particular, superlinear convergence, mass conservation, well balancedness, and stability are verified. 相似文献
1000.
Crystallization and Organic Field-Effect Transistor Performance of a Hydrogen-Bonded Quaterthiophene
Dr. Jan Gebers Dr. Bilal Özen Dr. Lucia Hartmann Michel Schaer Dr. Stéphane Suàrez Philippe Bugnon Dr. Rosario Scopelliti Dr. Hans-Georg Steinrück Dr. Oleg Konovalov Prof. Andreas Magerl Dr. Martin Brinkmann Dr. Riccardo Petraglia Dr. Piotr de Silva Prof. Clémence Corminboeuf Prof. Holger Frauenrath 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(45):10265-10275
Crystalline thin films of π-conjugated molecules are relevant as the active layers in organic electronic devices. Therefore, materials with enhanced control over the supramolecular arrangement, crystallinity, and thin-film morphology are desirable. Herein, it is reported that hydrogen-bonded substituents serve as additional structure-directing elements that positively affect crystallization, thin-film morphology, and device performance of p-type organic semiconductors. It is observed that a quaterthiophene diacetamide exhibits a denser packing than that of other quaterthiophenes in the single-crystal structure and, as a result, displays enhanced intermolecular electronic interactions. This feature was preserved in crystalline thin films that exhibited a layer-by-layer morphology, with large domain sizes and high internal order. As a result, organic field-effect transistors of these polycrystalline thin films showed mobilities in the range of the best mobility values reported for single-crystalline quaterthiophenes. The use of hydrogen-bonded groups may, thus, provide an avenue for organic semiconducting materials with improved morphology and performance. 相似文献