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1.
E. D. Livshits 《Mathematical Notes》2007,82(3-4):332-340
In this paper, we consider algorithms for constructing n-terms approximations with nonnegative coefficients. The convergence theorem is proved for a “positive” analog of the Pure Greedy Algorithm. We establish a condition on the sequence of weakness coefficients which is sufficient for the convergence of the Positive Weak Greedy Algorithm. This condition is also necessary for the class of monotone sequences. 相似文献
2.
V. A. Livshits B. G. Dzikovskii V. P. Tsybyshev B. B. Meshkov 《Russian Chemical Bulletin》1996,45(7):1563-1571
Isotherms of the binding of dodecyl sulfate anions (DDS–)and Na+ counterions during their coadsorption with a nonionic polymer. proxanol (PR). at the interface of dodecane-water emulsions have been measured by conductometry and Na-selective potentiometry. The adsorption of DDS– and PR is concurrent. The affinity constant of PR to the interface determined by the Langmuir model decreases as the concentration of PR increases, and the surface concentration of DDS– tends to a nonzero limiting value at high concentrations of PR. The surface (o) and electrokinetic () potentials at the interface have been determined at various polymer concentrations by the spin probe and electrophoresis methods. The average dielectric permeability and density of polymer segments in We adsorption layer have been determined by ESR. The lower boundary of the hydrodynamic thickness of the polymer adsorption layer at the interface has been estimated from the dependences of o and on the ionic strength.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1653–1661, July, 1996. 相似文献
3.
4.
Electrophoretic mobilities of hexadecane/water emulsions containing dimyristoyl-phosphatidylcholine (DMPC) or egg yolk lecithin
(EYL) monolayers at the interface and those of liposomes prepared from the same lipids were measured as functions of the concentrations
of Ca2+, Mn2+, Cu2+, and Ni2+ cations in the aqueous phase. The surface potentials, surface charge densities (σ), and the Langmuir adsorption isotherms
for various distances from the charged surface to the slip plane (d) were calculated on the basis of the Gouy-Chapman theory for 1∶2 electrolytes and the values of ζ-potentials. The binding
constants (K) and parametersd were determined under the assumption that the maximum σ values correspond to one ion per phospholipid molecule at the interface.
In the case of DMPC, the ion binding constants (L mol−1) at 25°C are 230 and 87 for Ca2+, 31.5 and 21 for Mn2+, 11 and 6 for Cu2+, and 7.5 and 5.3 for Ni2+ in liposomes and emulsions, respectively. The affinities of Cu2+ and Ni2+ ions for EYL monolayers and bilayers are lower than those for DMPC mono- and bilayers. Thed parameters for all ions are smaller than the radii of the hydrated ions. In the case of Ca2+, Cu2+, and Ni2+, thed values for mono- and bilayers are different. The differences in K values between monolayers and bilayers as well as those
between DMPC and EYL mono- and bilayers can be attributed to the differences in the local environment and orientation of the
interfacial phosphate groups in these systems.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2490–2495, December, 1998. 相似文献
5.
A. B. Kamenskii Yu. I. Smushkevich A. I. Livshits N. N. Suvorov 《Chemistry of Heterocyclic Compounds》1980,16(7):741-743
A method for the preparation of indole analogs of tolan, viz., indolylphenylacetylene and di-indolylacetylene, from indolyl benzyl ketone and indolyl skatyl ketone, respectively, by reaction with a Vilsmeier—Haack reagent was developed. The synthesis of indolyl skatyl ketone and 3-(3-indolyl)-3-chloro-2-phenyl-2-propen-1-al was realized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 956–958, July, 1980. 相似文献
6.
V. P. Tsybyshev V. A. Livshits B. B. Meshkov O. A. Fedorova S. P. Gromov M. V. Alfimov 《Russian Chemical Bulletin》1997,46(7):1239-1244
An amphiphilic crown-containing styryl dye (1) was synthesized, and the effects of irradiation, temperature, and alkali and alkali-earth metal ions on the conductivity
and optical spectra of its solutions in dioctyl phthalate were studied. Compound1 in thetrans-form almost completely exists as ion pairs (IP). Irradiation at a long-wavelength absorption maximum (λmax) results in a reversible increase in the conductivity and, hence, a degree of dissociation of IP (α); these parameters decrease
when complexes with metal ions are formed. The relaxation times for the photoinduced conductivity coincide with a decrease
in the extinction within experimental error in the 20–60°C temperature range. The photoinduced increase in α is caused bytrans—cis-isomerization and an increase in steric hindrances for the interaction of the ClO4
− anion with the N+ atom of benzothiazolium in thecis-form of1. The activation energies for the darkcis—trans-relaxation, absolute α values, and thermodynamic parameters of dissociation of IP in thetrans-form, as well as the α values in a photostationary mixture ofcis—trans-isomers, were estimated. The decrease in α after binding with metal ions is likely caused by the redistribution of the positive
charge to benzothiazolium through the conjugated system of1. Correlations between the decrease in conductivity (decrease in α) and the hypsochromic shift Δλmax after the formation of complexes between1 and metal ions were observed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1301, July, 1997. 相似文献
7.
Stablen-hexadecane/water andn-tetradecane/water macroemulsions containing monolayers of natural (egg yolk lecithin, EY) and synthetic (dimyristoylphosphatidylcholine,
DMPC) phospholipids at liquid-liquid interfaces were prepared. The existence of the monolayers was proved by studying the
reduction kinetics of a surface-active spin probe with ascorbate anions. Spin labeled derivatives of stearic acid in which
the nitroxide group is locared at different distances from the polar head (5-, 12-, and 16-doxylstearic acids) were used to
study the temperature dependences of the molecular ordering, rotational mobility, and local polarity in the monolayers in
emulsions and also in bilayers in liposomes obtained from the same lipids. In the EY monolayers, the degree of spin probe
solubilization is higher, while the order parameters (S) and rotational correlation times (τ) are lower than those in EY bilayers. The differences between these parameters for mono-
and bilayers increase with an increase in the distance of the reporter group from the aqueous phase. In the DMPC monolayers,
a first-order phase transition was detected by measuring the temperature dependences ofS and τ. The temperature region of the phase transition in monolayers is shifted to lower temperatures with respect to that
for bilayers and depends on the nature of the oil phase. It was concluded that the phospholipid monolayers in emulsions incorporate
hydrocarbon molecules, whose concentration in the DMPC monolayers increases on going from the low-temperature (gel) to the
high-temperature (liquid crystal) phase.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 418–425, March, 1998. 相似文献
8.
The surface energy of MgO is determined using experimental data collected from equilibrated thermal grooves circumscribing island grains. Local equilibrium assumptions at each groove require that the Herring equations be satisfied at each data site, thereby yielding a large and overdetermined system of equations involving the surface energy . This inverse problem is then solved using a new technique that is statistical in nature and multiscale in implementation. The resulting discrete solution represents a statistically significant representation of the surface energy of MgO as a function of surface orientation. Comparisons to results derived from a more traditional approach, along with suggested further applications, are discussed. 相似文献
9.
10.