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61.
Journal of Nonlinear Science - In the variational problems involving non-convex integral functionals, finding the binodal, the boundary of validity of the quasiconvexity of the energy density, is... 相似文献
62.
Alexander M. Khenkin Gregory Leitus Lev Weiner Ronny Neumann 《Journal of Cluster Science》2014,25(3):687-693
The tri-rhenium(VI) capped Wells–Dawson polyoxometalate, [Re3P2W15O62]6– with quaternary ammonium cations was synthesized by reacting the trivacant lacunary species, [P2W15O56]12– with [ReOCl3(PPh3)2] in an organic solvent. Elemental analysis by thermogravimetry and inductively coupled plasma mass spectroctrometry confirmed the substitution of three rhenium atoms, single-crystal X-ray diffraction as well as infra red spectroscopy showed the complete Wells–Dawson structure. The presence of all three rhenium atoms in one cap is indicated by 31P nuclear magnetic resonance spectroscopy and the electron spin resonance spectrum shows that the tri-rhenium(V) species with three unpaired electrons is low spin, S = ½. 相似文献
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64.
Dongjie Zhang Miguel A. Soto Lev Lewis Wadood Y. Hamad Mark J. MacLachlan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4735-4740
Cellulose nanocrystals (CNCs) spontaneously assemble into gels when mixed with a polyionic organic or inorganic salt. Here, we have used this ion-induced gelation strategy to create functional CNC gels with a rigid tetracationic macrocycle, cyclobis(paraquat-p-phenylene) ( CBPQT 4+). Addition of [ CBPQT ]Cl4 to CNCs causes gelation and embeds an active host inside the material. The fabricated CNC gels can reversibly absorb guest molecules from solution then undergo molecular recognition processes that create colorful host–guest complexes. These materials have been implemented in gel chromatography (for guest exchange and separation), and as elements to encode 2- and 3-dimensional patterns. We anticipate that this concept might be extended to design a set of responsive and selective gel-like materials functioning as, for instance, water-pollutant scavengers, substrates for chiral separations, or molecular flasks. 相似文献
65.
Dr. Alexey A. Mikhaylov Dr. Alexander G. Medvedev Dr. Andrei V. Churakov Dmitry A. Grishanov Dr. Petr V. Prikhodchenko Prof. Dr. Ovadia Lev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2980-2986
Tellurium–peroxo complexes in aqueous solutions have never been reported. In this work, ammonium peroxotellurates (NH4)4Te2(μ‐OO)2(μ‐O)O4(OH)2 ( 1 ) and (NH4)5Te2(μ‐OO)2(μ‐O)O5(OH)?1.28 H2O?0.72 H2O2 ( 2 ) were isolated from 5 % hydrogen peroxide aqueous solutions of ammonium tellurate and characterized by single‐crystal and powder X‐ray diffraction analysis, by Raman spectroscopy and thermal analysis. The crystal structure of 1 comprises ammonium cations and a symmetric binuclear peroxotellurate anion [Te2(μ‐OO)2(μ‐O)O4(OH)2]4?. The structure of 2 consists of an unsymmetrical [Te2(μ‐OO)2(μ‐O)O5(OH)]5? anion, ammonium cations, hydrogen peroxide, and water. Peroxotellurate anions in both 1 and 2 contain a binuclear Te2(μ‐OO)2(μ‐O) fragment with one μ‐oxo‐ and two μ‐peroxo bridging groups. 125Te NMR spectroscopic analysis shows that the peroxo bridged bitellurate anions are the dominant species in solution, with 3–40 %wt H2O2 and for pH values above 9. DFT calculations of the peroxotellurate anion confirm its higher thermodynamic stability compared with those of the oxotellurate analogues. This is the first direct evidence for tellurium–peroxide coordination in any aqueous system and the first report of inorganic tellurium–peroxo complexes. General features common to all reported p‐block element peroxides could be discerned by the characterization of aqueous and crystalline peroxotellurates. 相似文献
66.
Anastasia E. Sleptsova Liudmila N. Alyabyeva Evgeny A. Gorbachev Ekaterina S. Kozlyakova Maxim A. Karpov Chen Xinming Alexander V. Vasiliev Boris P. Gorshunov Anatoly S. Prokhorov Pavel E. Kazin Lev A. Trusov 《Mendeleev Communications》2021,31(2):221-223
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A mathematical model based on a straightforward geometrical background is developed which enables predictions of a transition of one dispersed phase to a cocontinuous one (i.e., the percolation threshold) on addition of another dispersed phase during melt mixing in ternary polymer blends. The present work concerns only ternary blends with two separate dispersions of the inner phases in which no encapsulation takes place. In addition, in order to simplify the model, one of the inner phases was represented by hard, nondeformable microspheres The expression developed describes well an experimental relationship between the percolation threshold, the concentration above which the former dispersed phase transforms to a continuous one, and concentrations of both inner phases. The results agree well with the experimental data obtained in a previous work. 相似文献
69.
A. G. Medvedev A. A. Mikhailov P. V. Prikhodchenko T. A. Tripol’skaya O. Lev A. V. Churakov 《Russian Chemical Bulletin》2013,62(8):1871-1876
The crystal structures of new peroxosolvates of the following pyridinemonocarboxylic acids were studied: picolinic 2-C5H4NCOOH·H2O2 (1), nicotinic 3-C5H4NCOOH·H2O2 (2), and isonicotinic 4-C5H4NCOOH·2H2O2 (3). In these compounds, the acids exist exclusively as zwitterions, as opposed to non-solvated crystals. In compounds 1–3, the hydrogen peroxide molecules form two donor hydrogen bonds and, in some cases, one additional acceptor hydrogen bond. Peroxosolvate 2 can be considered as a novel drug formulation of vitamin B3. 相似文献
70.
N. I. Kiselev D. A. Velikanov S. B. Korchagina E. A. Petrakovskaya A. D. Vasil’ev L. A. Solov’ev D. A. Balaev O. A. Bayukov I. A. Denisov S. S. Tsegel’nik E. V. Eremin D. A. Znak K. A. Shaikhutdinov A. A. Shubin N. P. Shestakov N. V. Volkov S. K. Gordeev P. I. Belobrov 《Russian Journal of General Chemistry》2013,83(11):2173-2181
The electrical and magnetic properties of the nanodiamond composites comprising nanodiamond, pyrolytic carbon, and nanosized pores were studied. The composites are p-type semiconductors and their resistance decreases by 12 orders of magnitude as the pyrocarbon-to-diamond ratio γ increases from 0 to 80 wt %. Evidence for paramagnetic properties of the nanodiamond composites was obtained. The observed properties are explained by increased concentration of surface Tamm states. The paramagnetic properties are explained in terms of the electron spins localized on the nanodiamond surface in the composite. 相似文献