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31.
In this paper we consider an isotropic variant of the BMO‐type norm recently introduced (Bourgain, Brezis, and Mironescu, 2015). We prove that, when considering characteristic functions of sets, this norm is related to the perimeter. A byproduct of our analysis is a new characterization of the perimeter of sets in terms of this norm, independent of the theory of distributions.© 2016 Wiley Periodicals, Inc. 相似文献
32.
Israel Zilbermann Avraham Meshulam Haim Cohen Dan Meyerstein 《Supramolecular chemistry》2013,25(2):325-332
Abstract The mechanisms and kinetics of oxidation of ascorbate, AH?, by Ni(III)Li aq and by LiNi(III) (HPO4)2 ? complexes (L1 = meso-(5,12)-7,7,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; L2 = 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) in neutral aqueous solutions have been investigated. The oxidation of ascorbate by the LiNi(III) (HPO4)2 ? and Ni(III)L1 aq proceeds via two consecutive reactions well separated in time. The products of the first reaction are the A.? radical anion and the corresponding Ni(II) complex. The oxidations by the LiNi(III)(HPO4)2 ? complexes proceed via the outer sphere mechanism, whereas the detailed mechanism of reaction of Ni(III)L1 aq cannot be determined. The rate of reaction decreases with the increase in the concentration of phosphate, thus indicating that LiNi(III)(HPO4)(H2O)+ and LiNi(III)OH2+ are stronger oxidizing agents than LiNi(III)(HPO4)? 2. The oxidation of ascorbate by Ni(III)L2 aq proceeds via three consecutive reactions which are well separated in time. Thus the results clearly point out that this process occurs via the inner sphere mechanism. The first transient observed is tentatively identified as L2(H2O)Ni(II)(A.?)2+, i.e., an unexpected complex of the ascorbate anion radical. Also in this process the last transient observed is the A.? anion radical. The stabilization of the ascorbyl radical in a transient complex might be of biological significance. 相似文献
33.
L. L. Gur’eva A. I. Tkachuk L. I. Kuzub G. A. Estrina E. I. Knerel’man I. I. Khodos B. A. Rozenberg 《Polymer Science Series B》2013,55(3-4):139-146
Silver nanoparticles stabilized by polystyrylmonocaboxylate ligands with varied chain lengths are synthesized via the low-temperature reduction of silver polystyrylmonocaboxylate with triethylamine. Silver nanoparticles have small dimensions, narrow size distributions, high stability, and ability to redisperse in nonpolar solvents. The kinetic features of the reaction are studied via high-performance liquid chromatography; UV, visible and IR spectroscopy; and transmission electron microscopy. It is shown that the reduction of silver occurs in the cores of reverse micelle species organized by diphilic macromolecules of silver polystyrylmonocarboxylates. 相似文献
34.
Tamar Nicole Soussana Dr. Haim Weissman Prof. Boris Rybtchinski Prof. Ran Drori 《Chemphyschem》2021,22(21):2182-2189
The mechanism by which safranine O (SFO), an ice growth inhibitor, halts the growth of single crystal tetrahydrofuran (THF) clathrate hydrates was explored using microfluidics coupled with cold stages and fluorescence microscopy. THF hydrates grown in SFO solutions exhibited morphology changes and were shaped as truncated octahedrons or hexagons. Fluorescence microscopy and microfluidics demonstrated that SFO binds to the surface of THF hydrates on specific crystal planes. Cryo-TEM experiments of aqueous solutions containing millimolar concentrations of SFO exhibited the formation of bilayered lamellae with an average thickness of 4.2±0.2 nm covering several μm2. Altogether, these results indicate that SFO forms supramolecular lamellae in solution, which might bind to the surface of the hydrate and inhibit further growth. As an ice and hydrate inhibitor, SFO may bind to the surface of these crystals via ordered water molecules near its amine and methyl groups, similar to some antifreeze proteins. 相似文献
35.
Dr. Jonathan Baram Dr. Haim Weissman Dr. Yaron Tidhar Dr. Iddo Pinkas Prof. Boris Rybtchinski 《Angewandte Chemie (International ed. in English)》2014,53(16):4123-4126
In covalent polymerization, a single monomer can result in different polymer structures due to positional, geometric, or stereoisomerism. We demonstrate that strong hydrophobic interactions result in stable noncovalent polymer isomers that are based on the same covalent unit (amphiphilic perylene diimide). These isomers have different structures and electronic/photonic properties, and are stable in water, even upon prolonged heating at 100 °C. Such combination of covalent‐like stability together with structural/functional variation is unique for noncovalent polymers, substantially advancing their potential as functional materials. 相似文献
36.
The formation of heterophase polymers via phase separation in the course of curing reaction in a blend of a thermosetting oligomer with a rubber modifier is considered. The interference of thermodynamic and kinetic factors that define the morphology of the material being formed is discussed. The need for a kinetic theory of cure-induced phase separation is established, and an approach of this kind is proposed. On the basis of this approach a simple quantitative criterion of deflection of the phase-separating system from the thermodynamic equilibrium is given. 相似文献
37.
We study experimentally and theoretically the hydrodynamic coupling between Brownian colloidal particles diffusing along a linear channel. The quasi-one-dimensional confinement, unlike other constrained geometries, leads to a sharply screened interaction. Consequently, particles move in concert only when their mutual distance is smaller than the channel width, and two-body interactions remain dominant up to high particle densities. The coupling in a cylindrical channel is predicted to reverse sign at a certain distance, yet this unusual effect is too small to be currently detectable. 相似文献
38.
M.J. Rozenberg 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):457-461
We propose a novel scenario for the electronic state in the manganese perovskites. We argue that, at low temperatures and
within the ferromagnetic state, the physics of these colossal magnetoresistance compounds may be characterized by a correlated
metallic state near a metal insulator transition where the orbital degrees of freedom play the main role. This follows from
the observation that a two-band degenerate Hubbard model under a strong magnetic field can be mapped onto a para-orbital single
band model. We solve the model numerically using the quantum Monte-Carlo technique within a dynamical mean field theory which
is exact in the limit of large lattice connectivity. We argue that the proposed scenario may allow for the qualitative interpretation
of a variety of experiments which were also observed in other (early) transition metal oxides.
Received: 3 October 1997 / Revised: 9 December 1997 / Accepted: 12 January 1998 相似文献
39.
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