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31.
Cellular membranes of mammals are composed of a complex assembly of diverse phospholipids. Sphingomyelin (SM) and phosphatidylcholine (PC) are important lipids of eukaryotic cellular membranes and neuronal tissues, and presumably participate in the formation of membrane domains, known as "rafts," through intermolecular interaction and lateral microphase decomposition. In these two-dimensional membrane systems, lateral diffusion of lipids is an essential dynamic factor, which might even be indicative of lipid phase separation process. Here, we used pulsed field gradient nuclear magnetic resonance to study lateral diffusion of lipid components in macroscopically oriented bilayers composed of equimolar mixtures of natural SMs of egg yolk, bovine brain, bovine milk and dipalmitoylphosphatidylcholine (DPPC) with dioleoylphosphatidylcholine (DOPC). In addition, differential scanning calorimetry was used as a complementary technique to characterize the phase state of the lipid bilayers. In fully liquid bilayers, the lateral diffusion coefficients in both DOPC/DPPC and DOPC/SM systems exhibit mean values of the pure bilayers. For DOPC/SM bilayer system, this behavior can be explained by a model where most SM molecules form short-lived lateral domains with preferential SM-SM interactions occurring within them. However, for bilayers in the presence of their low-temperature gel phase, lateral diffusion becomes complicated and cannot simply be understood solely by a simple change in the liquid phase decomposition. 相似文献
32.
Sh. Sh. Bashkirov N. V. Boltakova V. V. Parfenov R. A. Nazipov A. V. Pyataev I. A. Gabidullin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):343-346
Strontium-substituted ferromanganites of europium and thulium were investigated. Samples of Eu0.65Sr0.35Mn1 ? x Fe x O3 and Tm0.65Sr0.35Mn1 ? x Fe x O3 were prepared using ceramic processing. Based on the data from X-ray analysis, the samples with europium had a perovskite lattice, whereas the thulium samples were crystallized in an ilmenite lattice. Stratification of the magnetic subsystem was observed in the Mössbauer spectra of certain samples at T ≈ 300 K. 相似文献
33.
The possibility of increasing the thermoelectric figure of merit for bulk nanostructured materials has been investigated theoretically.
The kinetic coefficients of the nanostructured material have been calculated and evaluated under the assumption that the dominant
role in the transfer is played by the tunneling of electrons between nanoparticles. The limiting case of the absence of phonon
thermal conductivity through barrier layers has been considered. It has been demonstrated using the estimates obtained for
materials based on Bi2Te3 that the thermopower in the nanostructured material can be sufficiently high and that, despite the low electrical conductivity,
the dimensionless thermoelectric figure of merit can be as large as 3–4 at room temperature. 相似文献
34.
Olga V. Andreeva Maya G. Belenok Liliya F. Saifina Marina M. Shulaeva Alexey B. Dobrynin Radmila R. Sharipova Alexandra D. Voloshina Alina F. Saifina Aidar T. Gubaidullin Bulat I. Khairutdinov Yuriy F. Zuev Vyacheslav E. Semenov Vladimir E. Kataev 《Tetrahedron letters》2019,60(47):151276
A series of novel 1,2,3-triazolyl nucleoside analogues was synthesized via the CuAAC reaction of N1-alkynyl uracil, 6-methyluracil, 3,6-dimethyl uracil, thymine and quinazolin-2,4-dione with protected azido β-d-ribofuranose. The obtained compounds differ in both the nature of the pyrimidine-2,4-dione fragment and the length of the polymethylene linker connecting it with the β-d-ribofuranosyl-1,2,3-triazol-4-yl moiety. The 1,2,3-triazolyl nucleoside analogues were evaluated for their cytotoxicity in vitro. 相似文献
35.
Yu. O. Chetverikov N. N. Aruev S. A. Bulat K. A. Gruzdov V. F. Ezhov P. Jean-Baptiste I. L. Kamenskii V. Ya. Lipenkov E. M. Prasolov V. A. Solovei R. V. Tyukal’tsev I. L. Fedichkin 《Technical Physics》2018,63(5):738-746
Isotope ratios of noble gases (He, Ne, Ar) were studied in samples collected by degassing of cores of water frozen over a glacier of Lake Vostok. The gases were collected into glass retorts during three days of degassing of cores, which have just been extracted from the borehole. Within the error, the isotope 3He/4He ratios of 0.28 ± 0.08 RA (RA = 1.38 × 10–6 is the ratio for air) correspond to those from [1]. The 4He/20Ne and 40Ar/36Ar ratios (12.4 ± 4.6 RA and 1.0074 ± 0.0023 RA, respectively) exceed their contents in air (4He/20NeA = 0.29; 40Ar/36ArA = 298.6) and may indicate some contribution of terrigenous gas to the gaseous balance of the lake, as well as the high content of ancient ground waters in the lake. The 3He/4He ratio of 0.28 RA means low mantle 3He flux typical of continental platforms far from active rift zones. 相似文献
36.
The diffraction of a shock wave (M0=4.7) at an angle close to 180 has been experimentally investigated for the three-dimensional case. Interferograms of the flow and the pressure distribution on the back wall in the course of its interaction with the diffracted wave were obtained. Rotation of the flow structure behind the shock wave relative to the axis of symmetry was observed as the flow pattern develops in time and space.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 200–201 March–April, 1993. 相似文献
37.
The change of the lattice thermal conductivity of bulk nanostructured materials based on Bi2Te3-Sb2Te3 solid solutions with grain size distribution has been studied. These materials have a polycrystalline structure with grain sizes ranging from a few tens of a nanometer to a few micrometers. Large grains may contain inclusions or consist of several smaller parts which can be identified with coherent scattering regions seen in X-ray diffraction. The change of the lattice thermal conductivity mediated by additional scattering by inclusions and grain boundaries has been calculated. This calculation allows for the effect of nanoparticle size distribution. The calculated estimates are compared with the available experimental data. 相似文献
38.
39.
International Applied Mechanics - 相似文献
40.
Bulat L. P. Ivanov A. A. Osvenskii V. B. Pshenay-Severin D. A. Sorokin A. I. 《Physics of the Solid State》2017,59(10):2097-2102
Physics of the Solid State - The temperature dependence of the thermal conductivity of nanostructured samples of copper selenide prepared by mechanochemical synthesis from initial pure components... 相似文献