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11.
12.
Aakarsh Saxena Emily C. Dugan Jeffrey Liaw Matthew D. Dembo Robert D. Pike 《Polyhedron》2009,28(18):4017-4031
The coordination of heterocyclic thiourea ligands (L = N-(2-pyridyl)-N′-phenylthiourea (1), N-(2-pyridyl)-N′-methylthiourea (2), N-(3-pyridyl)-N′-phenylthiourea (3), N-(3-pyridyl)-N′-methylthiourea (4), N-(4-pyridyl)-N′-phenylthiourea (5), N-(2-pyrimidyl)-N′-phenylthiourea (6), N-(2-pyrimidyl)-N′-methylthiourea (7), N-(2-thiazolyl)-N′-methylthiourea (8), N-(2-benzothiazolyl)-N′-methylthiourea (9), N,N′-bis(2-pyridyl)thiourea (10) and N,N′-bis(3-pyridyl)thiourea (11)) with CuX (X = Cl, Br, I, NO3) has been investigated. CuX:L product stoichiometries of 1:1–1:5 were found, with 1:1 being most common. X-ray structures of four 3-coordinate mononuclear CuXL2 complexes (CuCl(6)2, CuCl(7)2, CuBr(6)2, and CuBr(9)2) are reported. In contrast, CuBr(1)2 is a 1D sulfur-bridged polymer. CuIL structures (L = 7, 8) are 1D chains with corner-sharing Cu2(μ-I)2 and Cu2(μ-S)2 units, and CuCl(10) is a 2D network having μ-Cl and N-/S-bridging L. Two [CuL2]NO3 structures are reported: a mononuclear 4-coordinate copper complex with chelating ligands (L = 10) and a 1D link-chain with N-/S-bridging L (L = 3). Two ligand oxidative cyclizations were encountered during crystallization. CuI crystallized with 6 to produce zigzag ladder polymer [(CuI)2(12)]·½CH3CN (12 = N-(pyrimidin-2-yl)benzo[d]thiazol-2-amine) and CuNO3 crystallized with 10 to form [Cu2(NO3)(13)2(MeCN)]NO3 (13 = dipyridyltetraazathiapentalene). 相似文献
13.
14.
Serguei G. Starodoubtsev Natalia A. Churochkina Alexander T. Dembo Alexei R. Khokhlov 《Macromolecular Symposia》1999,146(1):193-198
The swelling behavior in the solutions of sodium chloride, linear polyelectrolytes and ionic surfactants of the composites based on clay mineral bentonite (BENT) embedded in neutral and slightly charged poly(acrylamide) (PAAm) gels is studied. Negatively charged flat clay particles incorporated into polymer gel adsorb oppositely charged surfactant and linear polyelectrolyte and attract the charged chains of cationic polymer matrix. The results of SAXS study manifest the formation of lamella structure of the cationic surfactant adsorbed by the clay plates. The gels loaded with the clay show a strong response to changes in the nature and the composition of the ionic environment. 相似文献
15.
D. I. Svergun É. V. Shtykova M. B. Kozin V. V. Volkov P. V. Konarev A. T. Dembo E. V. Shtykova Jr. L. M. Bronshtein D. M. Chernyshov O. A. Platonova A. N. Yakunin P. M. Valetsky A. R. Khokhlov 《Crystallography Reports》2001,46(4):586-595
The structures of self-organizing polymer matrices based on collapsed gels and polyoctadecylsiloxanes have been studied by the methods of conventional and anomalous X-ray small-angle scattering with the use of the laboratory and synchrotron sources of X-ray radiation. The process of formation of metal nanoparticles in such matrices is also studied, their size distributions are calculated, and the models of localization of these particles in the polymer matrices are suggested. It is shown that growth of metal particles is controlled by the structure of the polymer network and is limited by the dimensions of its cells. The electron-density profiles of polycondensed octadecylsiloxane matrices are also calculated. 相似文献
16.
Yu. M. Yevdokimov V. I. Salyanov O. V. Kondrashina A. A. Gasanov É. V. Shtykova K. A. Dembo 《Journal of Experimental and Theoretical Physics》2007,104(3):499-507
Certain physicochemical characteristics of particles of the cholesteric liquid-crystal dispersions of complexes of double-stranded nucleic acids with rare earth elements have been determined. It is shown for the first time that the binding of the rare earth cations to linear nucleic acid molecules ordered in the structure of particles of the cholesteric liquid crystal dispersions is accompanied not only by amplification of the abnormal band in the circular dichroism spectrum, but also by the disappearance of the characteristic maximum on the X-ray scattering curves for small angles. The (cholesteric 1-cholesteric 2) transition induced by rare earth cations is an example of the operation of a microscopic machine consisting of spatially ordered nucleic acid molecules. Particles of the cholesteric liquid crystal dispersions of nucleic acid complexes with rare earth elements hold the abnormal optical properties for a long time. 相似文献
17.
CD spectra of liquid-crystalline dispersions, X-ray diffraction patterns and optical textures of liquid crystals prepared from native superhelical DNA in poly(ethyleneglycol)-containing water-salt solutions before and after treatment of DNA with micrococcal nuclease have been obtained. It was found that condensation of native superhelical DNA is accompanied by the formation of liquid crystals with a non-specific optical texture. After treatment of the DNA, liquid-crystalline dispersions, with Micrococcal nuclease the DNA is able to form two similar types of liquid crystals with abnormal optical activity which differ in the peculiarities of their textures. The data obtained demonstrate the formation of multiple types of liquid crystals from high molar mass double-stranded optically active DNA molecules. 相似文献
18.
V. E. Asadchikov V. V. Volkov Yu. O. Volkov K. A. Dembo I. V. Kozhevnikov B. S. Roshchin D. A. Frolov A. M. Tikhonov 《JETP Letters》2011,94(7):585-587
The structure of the transient layer at the interface between air and the aqueous solution of silica nanoparticles with the
size distribution of particles that has been determined from small-angle scattering has been studied by the X-ray reflectometry
method. The reconstructed depth profile of the polarizability of the substance indicates the presence of a structure consisting
of several layers of nanoparticles with the thickness that is more than twice as large as the thickness of the previously
described structure. The adsorption of 1,2-distearoyl-sn-glycero-3-phosphocholine molecules at the hydrosol/air interface
is accompanied by the condensation of anion silica nanoparticles at the interface. This phenomenon can be qualitatively explained
by the formation of the positive surface potential due to the penetration and accumulation of Na+ cations in the phospholipid membrane. 相似文献
19.
Summary Refinements of Sanov's large deviations theorem lead via Csiszár's information theoretic identity to refinements of the Gibbs conditioning principle which are valid for blocks whose length increase with the length of the conditioning sequence. Sharp bounds on the growth of the block length with the length of the conditioning sequence are derived.Partially supported by NSF DMS92-09712 grant and by a US-Israel BSF grantPartially supported by a US-Israel BSF grant and by the fund for promotion of research at the Technion 相似文献
20.
We present a tracking model for asset allocation that tracks desired investment goals. The model is shown to be optimal with respect to an investor's ‘regret distribution’, the cumulative distribution of the difference between the revenue under perfect foresight and that possible without foresight. Relationships with Markowitz mean/variance models are also explored. 相似文献