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31.
A single piston capillary rheometer was modified by the addition of a second chamber with a restricting valve (developed at
the Polymer Centre, Zlín, Czech Republic), which provides backpressure and increasing the pressure in the melted material
during the flow through the die. The Carreau–Yasuda model was employed to fit the measured viscosity data and determine the
temperature and pressure coefficients for polyolefin based binder and its compounds with carbide powder. Both temperature
and pressure sensitivity coefficients are largely dependent on the structure of a polymer, which should be taken into account
for binder-formation’s development. Increasing the loading level of the powder in the compound diminishes the pressure sensitivity
of their flow properties. 相似文献
32.
Virender K. Sharma Karolina M. Siskova Radek Zboril Jorge L. Gardea-Torresdey 《Advances in colloid and interface science》2014
This review paper presents the overview of processes involved in transformation of organic-coated silver nanoparticles (AgNPs) in biological systems and in the aquatic environment. The coating on AgNPs greatly influences the fate, stability, and toxicity of AgNPs in aqueous solutions, biological systems, and the environment. Several organic-coated AgNP systems are discussed to understand their stability and toxicity in biological media and natural water. Examples are presented to demonstrate how a transformation of organic-coated AgNPs in an aqueous solution is affected by the type of coating, pH, kind of electrolyte (mono- or divalent), ionic strength, organic ligands (inorganic and organic), organic matter (fulvic and humic acids), redox conditions (oxic and anoxic), and light. Results of cytotoxicity, genotoxicity, and ecotoxicity of coated AgNPs to food chain members (plants, bacteria, and aquatic and terrestrial organisms) are reviewed. Key factors contributing to toxicity are the size, shape, surface coating, surface charge, and conditions of silver ion release. AgNPs may directly damage the cell membranes, disrupt ATP production and DNA replication, alternate gene expressions, release toxic Ag+ ion, and produce reactive oxygen species to oxidize biological components of the cell. A progress made on understanding the mechanism of organic-coated AgNP toxicity using different analytical techniques is presented. 相似文献
33.
Stochastic simulation of coupled chemical reactions is often computationally intensive, especially if a chemical system contains reactions occurring on different time scales. In this paper, we introduce a multiscale methodology suitable to address this problem, assuming that the evolution of the slow species in the system is well approximated by a Langevin process. It is based on the conditional stochastic simulation algorithm (CSSA) which samples from the conditional distribution of the suitably defined fast variables, given values for the slow variables. In the constrained multiscale algorithm (CMA) a single realization of the CSSA is then used for each value of the slow variable to approximate the effective drift and diffusion terms, in a similar manner to the constrained mean-force computations in other applications such as molecular dynamics. We then show how using the ensuing Fokker-Planck equation approximation, we can in turn approximate average switching times in stochastic chemical systems. 相似文献
34.
35.
Mohamed K. Albolkany Dr. Yang Wang Dr. Weijin Li Syeda Arooj Chun-Hui Chen Niannian Wu Yan Wang Prof. Dr. Radek Zbořil Prof. Dr. Roland A. Fischer Prof. Dr. Bo Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21683-21688
Graphitic carbon nitride quantum dots (g-CNQDs) are highly promising photoresponsive materials. However, synthesis of monodispersed g-CNQDs remains challenging. Here we report the dual function of MOF [Cu3BTC2] (HKUST-1) as a catalyst and template simultaneously to prepare g-CNQDs under mild conditions. Cyanamide (CA), a graphitic carbon nitride precursor, catalytically dimerized inside the larger MOF cavities at 90 °C and condensed into g-CNQDs at 120 °C in a controlled fashion. The HKUST-1 template was stable under the reaction conditions, leading to uniform g-CNQDs with a particle size of 2.22±0.68 nm. The as prepared g-CNQDs showed photoluminescence emission with a quantum yield of 3.1 %. This concept (MOF dual functionality) for catalyzing CA polycondensation (open metal sites (OMSs) effect) and controlling the produced particle size (pore-templating effect), together with the tunable MOF porosity, is expected to produce unique g-CNQDs with controllable size, morphology, and surface functionality. 相似文献
36.
Radek Erban 《Mathematical Methods in the Applied Sciences》2003,26(6):489-517
We consider the Navier–Stokes equations for compressible, barotropic flow in two space dimensions. We introduce useful tools from the theory of Orlicz spaces. Then we prove the existence of globally defined finite energy weak solutions for the pressure satisfying p(?) = a?logd(?) for large ?. Here d>1 and a > 0. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
37.
Ray L. Frost Silmarilly Bahfenne Jií ejka Jií Sejkora Sara J. Palmer Radek koda 《Journal of Raman spectroscopy : JRS》2010,41(6):690-693
Raman spectroscopy has been used to study the arsenate minerals haidingerite Ca(AsO3OH)·H2O and brassite Mg(AsO3OH)·4H2O. Intense Raman bands in the haidingerite spectrum observed at 745 and 855 cm−1 are assigned to the (AsO3OH)2−ν3 antisymmetric stretching and ν1 symmetric stretching vibrational modes. For brassite, two similarly assigned intense bands are found at 809 and 862 cm−1. The observation of multiple Raman bands in the (AsO3OH)2− stretching and bending regions suggests that the arsenate tetrahedrons in the crystal structures of both minerals studied are strongly distorted. Broad Raman bands observed at 2842 cm−1 for haidingerite and 3035 cm−1 for brassite indicate strong hydrogen bonding of water molecules in the structure of these minerals. OH···O hydrogen‐bond lengths were calculated from the Raman spectra based on empirical relations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
38.
A variational two-level method in the class of methods with an aggressive coarsening and a massive polynomial smoothing is proposed. The method is a modification of the method of Section 5 of Tezaur, Vaněk (2018). Compared to that method, a significantly sharper estimate is proved while requiring only slightly more computational work. 相似文献
39.
Shivaji S. Kadam Lukáš Maier Tomáš Šolomek Marek Nečas Karel Šmejkal Jiří Dostál Vladimír Sklenář Radek Marek 《Journal of Physical Organic Chemistry》2013,26(10):814-821
We report a preparation of new 6‐substituted‐5,6‐dihydrobenzo[c]phenanthridines by the reaction of azoles with quaternary benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine. The prepared compounds have been characterized by NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction. Conformational behaviors of carbazole derivatives in solution have been investigated by low‐temperature NMR experiments. Barriers to rotation around newly formed C6–N bonds were determined to be 12–13 kcal/mol. Quantum chemical calculations have been used to reproduce the experimental observations. Large structural effects on several 1H NMR resonances were observed experimentally, analyzed by Density Functional Theory (DFT) calculations at B3LYP/6‐311+G(d,p)/PCM level, and interpreted by ring‐current effects of the benzo[c]phenanthridine and carbazole units. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
40.
In this paper we introduce some fusion properties of forcing notions which guarantee that an iteration with supports of size ?κ not only does not collapse κ+ but also preserves the strength of κ (after a suitable preparatory forcing). This provides a general theory covering the known cases of tree iterations which preserve large cardinals (cf. Dobrinen and Friedman (2010) [3], Friedman and Halilovi? (2011) [5], Friedman and Honzik (2008) [6], Friedman and Magidor (2009) [8], Friedman and Zdomskyy (2010) [10], Honzik (2010) [12]). 相似文献