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31.
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
32.
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
33.
Kozmon S Matuška R Spiwok V Koča J 《Physical chemistry chemical physics : PCCP》2011,13(31):14215-14222
In this article we present the first systematic study of the additive properties (i.e. degree of additivity) of the carbohydrate-aromatic moiety CH-π dispersion interaction. The additive properties were studied on the β-D-glucopyranose, β-D-mannopyranose and α-L-fucopyranose complexes with the naphthalene molecule by comparing the monodentate (single CH-π) and bidentate (two CH-π) complexes. All model complexes were optimized using the DFT-D approach, at the BP/def2-TZVPP level of theory. The interaction energies were refined using single point calculations at highly correlated ab initio methods at the CCSD(T)/CBS level, calculated as E + (E(CCSD(T))-E(MP2))(Small Basis). Bidentate complexes show very strong interactions in the range from -10.79 up to -7.15 and -8.20 up to -6.14 kcal mol(-1) for the DFT-D and CCSD(T)/CBS level, respectively. These values were compared with the sum of interaction energies of the appropriate monodentate carbohydrate-naphthalene complexes. The comparison reveals that the bidentate complex interaction energy is higher (interaction is weaker) than the sum of monodentate complex interaction energies. Bidentate complex interaction energy corresponds to 2/3 of the sum of the appropriate monodentate complex interaction energies (averaging over all modeled carbohydrate complexes). The observed interaction energies were also compared with the sum of interaction energies of the corresponding previously published carbohydrate-benzene complexes. Also in this case the interaction energy of the bidentate complex was higher (i.e. weaker interaction) than the sum of interaction energies of the corresponding benzene complexes. However, the obtained difference is lower than before, while the bidentate complex interaction energy corresponds to 4/5 of the sum of interaction energy of the benzene complexes, averaged over all structures. The mentioned comparison might aid protein engineering efforts where amino acid residues phenylalanine or tyrosine are to be replaced by a tryptophan and can help to predict the changes in the interactions. The observed results also show that DFT-D correctly describes the CH-π interaction energy and their additive properties in comparison to CCSD(T)/CBS calculated interaction energies. Thus, the DFT-D approach might be used for calculation of larger complexes of biological interest, where dispersion interaction plays an important role. 相似文献
34.
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
35.
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
36.
Sy-David Friedman Radek Honzik Šárka Stejskalová 《Annals of Pure and Applied Logic》2018,169(6):548-564
Starting from a Laver-indestructible supercompact κ and a weakly compact λ above κ, we show there is a forcing extension where κ is a strong limit singular cardinal with cofinality ω, , and the tree property holds at . Next we generalize this result to an arbitrary cardinal μ such that and . This result provides more information about possible relationships between the tree property and the continuum function. 相似文献
37.
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
38.
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
39.
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
40.
Colloidal Surface Active Maghemite Nanoparticles for Biologically Safe CrVI Remediation: from Core‐Shell Nanostructures to Pilot Plant Development
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Dr. Massimiliano Magro Dr. Stefania Domeneghetti Davide Baratella Dr. Petr Jakubec Prof. Dr. Gabriella Salviulo Dr. Emanuela Bonaiuto Dr. Paola Venier Ondřej Malina Dr. Jiří Tuček Dr. Václav Ranc Dr. Giorgio Zoppellaro Prof.Dr. Radek Zbořil Prof. Dr. Fabio Vianello 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14219-14226
The present study is aimed at the exploration of achievable improvements for CrVI ex situ and in situ water remediation by using novel naked colloidal maghemite (γ‐Fe2O3) nanoparticles (surface active maghemite nanoparticles, SAMNs). The reliability of SAMNs for CrVI binding and removal was demonstrated, and SAMN@CrVI complex was characterized, as well as the covalent nature of the absorption was unequivocally proved. SAMNs were structurally and magnetically well conserved after CrVI binding. Thus, in consideration of their affinity for CrVI, SAMNs were exploited in a biological model system, mimicking a real in situ application. The assay evidenced a progressive reduction of revertant colonies of Salmonella typhimurium TA100 strain, as maghemite nanoparticles concentration increased, till the complete suppression of CrVI mutagen effect. Finally, an automatic modular pilot system for continuous magnetic removal and recovery of CrVI from water is proposed. SAMNs, thanks to their colloidal, binding, and catalytic properties, represent a promising tool as a reliable nanomaterial for water remediation by CrVI. 相似文献