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1.
The pseudopotential method is used to calculate the band spectra, valence charge densities, and electroneutrality levels in
the graphitic (h-BN) and rhombohedral (r-BN) modifications of boron nitride. It is shown that these compounds are indirect-band
insulators with the minimum energies of the indirect (4.65 and 4.8 eV) and direct (5.27 and 5.5 eV) forbidden zones in h-
and r-BN, respectively. The band energies of h-BN correlate well with the experimental data. Both crystals are characterized
by ionic-covalent chemical bonds. In the plane of hexagonal layers, the bonds are more covalent in h-BN. In h- and r-BN, the
electroneutrality levels correspond to the energy of about 1.9 eV over the top of the valence band, which is responsible for
the hole conductivity of the substances. In superlattices based on these compounds, the rhombohedral phase is a quantum well
for holes and a barrier for electrons.
Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 1, pp. 32–42, January–February, 1997. 相似文献
2.
N. E. Eshmirzaeva N. K. Khidyrova M. Khodzhaeva L. G. Mezhlumyan Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2005,41(4):451-453
Neutral substances, carbohydrates, and microelements from the aerial part of Silene viridiflora in addition to the protein content and its amino-acid composition were determined.
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Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 365–366, July–August, 2005. 相似文献
3.
M. A. Khodzhaeva A. A. Razhabova G. R. Muzaffarova 《Chemistry of Natural Compounds》2006,42(5):509-511
The content of carbohydrates in Allium motor was studied as a function of vegetation period. The qualitative and quantitative compositions and physical chemical properties
of sugars soluble in alcohol, water-soluble polysaccharides, pectinic substances, and hemicellulose were characterized. Galacturonan
was produced by partial hydrolysis of the pectinic substances.
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Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 409–411, September–October, 2006. 相似文献
4.
Free and bound lipids from Helianthus tuberosus tubers were investigated. Neutral, glyco-and phospholipid classes and their fatty-acid compositions were determined. The
composition of unsaponified substances was established.
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Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 3–4, January–February, 2008. 相似文献
5.
Yu. I. Vesnin 《Journal of Structural Chemistry》1995,36(4):655-660
Published experimental data on the dependence of the properties of crystal substances on crystal size are discussed. The dependence
is of the same form for different properties and different crystal substances. When the crystal diminishes in size, its properties
remain constant until the size decreases to 10−5–10−6 cm; smaller crystals considerably change their properties. It is shown that the currently available experimental data are
sufficient to substantiate the notion of an “elementary unit of a solid crystal” (“crystal quantum”). The elementary unit
of a crystal is regarded as a basis for the secondary structure (macrostructure) of a solid and an elementary carrier of its
“crystal” properties. Due to this notion, we can interpret the vast experimental material on the real structures and properties
of solids from a single viewpoint.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 724–730, July–August, 1995.
Translated by L. Smolina 相似文献
6.
D. A. Rakhimov T. N. Kholmuradova R. Sh. Shoyakubov 《Chemistry of Natural Compounds》2006,42(3):259-261
It was established by studying carbohydrates of Iris pseudacorus during vegetative periods that the content of water-soluble polysaccharides in the rhizomes and roots is greatest during
seed ripening; of pectinic substances, during budding. Glycomannan was isolated from seeds.
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Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 216–217, May–June, 2006. 相似文献
7.
M. Kh. Malikova 《Chemistry of Natural Compounds》1994,30(3):290-291
Pectin substances have been isolated from the leaves ofUngernia tadschicorum and characterized. A galacturonan has been obtained by partial hydrolysis. On the basis of the results of IR spectroscopy
and periodiate — nitric acid oxidation, its structure has been established as an α-1→4-bound polymer-homolog.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, FAX (3712) 62
73 48. Translated from Khimiya Prirodnykh Soedinenii, No. 3, 320–322, May–June, 1994. 相似文献
8.
G. S. Kupriyanova 《Journal of Structural Chemistry》1997,38(3):408-414
1H and13C NMR spectra of a series of coumarin dyes used as active laser media are studied. Electron densities and ring currents are
calculated. Formulas for calculating13C NMR chemical shifts from quantum mechanical data for aminocoumarins are suggested. NMR data and electronic structure calculations
are used to explain the generation properties of coumarins.
Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 3, pp. 495–502, May–June, 1997. 相似文献
9.
Voltammetry and electrochemical impedance spectroscopy were applied to investigate the inhibition activity of ethyleneglycol
and its oligomers on tin electrode in strong acidic sulfate solutions. Tetraethyleneglycol was found to be the most active
substance among compounds HO–(CH2–CH2–O)
m
–H (m≤4) that retards diffusion-controlled Sn(II) reduction due to its inhibitive adsorption. This rather slow process is controlled
both by diffusion and electrosorption steps. A comparison of exchange current densities obtained in the presence of different
polyethers shows that the length of the hydrocarbon chain is the main factor responsible for inhibition activity of such substances
on tin electrode. 相似文献
10.
V. P. Zhukov 《Journal of Structural Chemistry》1997,38(3):459-482
Popular techniques for analyzing the spatial and energy characteristics of chemical bonding in solids based on Hückel theory,
Hartree-Fock method, and electron density functional theory are reviewed. Methods for calculating the total energies and dependent
characteristics (cohesion energies, formation energies, partial pressures, etc.), the moments of the densities of states,
bond occupations, and the pair potentials of electron density and localization function are considered. Examples of using
these calculations for high-melting and laminated compounds are given.
Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 3, pp. 554–583, May–June, 1997. 相似文献
11.
V. M. Tapilin 《Journal of Structural Chemistry》1994,35(1):13-20
The Slater approximation for atomic electron energies is employed to calculate the electronic structure of the Ir(111) surface.
The results are used to estimate the shift of the 4f7/2 level on the surface relative to its position in the volume. The electron state densities in the neighborhood of the center
of the surface Brillouin zone (SBZ) are compared with photoelectronic spectra for emission normal to the Ir(111) surface.
On this basis, the accuracy of this approximation is estimated.
Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 17–24, January–February, 1994.
Translated by O. Kharlamova 相似文献
12.
V. V. Zadorozhnii O. I. Dubrovskii E. R. Likhachev S. I. Kurganskii 《Journal of Structural Chemistry》1998,39(6):876-883
The electronic structure of high-temperature superconducting films of Bi-Sr-Ca-Cu-O is determined using the linearized augmented
plane wave method. Total and local partial densities of states are calculated for each film using the results of band structure
calculations. Theoretical OKα and CuLα X-ray emission spectra are found. The dependence of the electronic structure and spectra on the number of CuO2 layers in the unit cell is discussed.
Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 6, pp. 1067–1075, November–December, 1998. 相似文献
13.
M. G. Kiselev Yu. P. Pukhovskii D. V. Ivlev Yu. M. Kessler 《Journal of Structural Chemistry》1999,40(2):246-252
The effect of variation of the potential function on the structural and dynamic properties of model water when the surface
of pair interactions is invariant is studied by the molecular dynamics method. Variations for the rigid and polarizable models
are compared.
Translated fromZhurnal Strukturnoi Khimii, Vol.40, No. 2, pp. 296–303, March–April, 1999. 相似文献
14.
A new steroid glycoside was isolated from leaves of Digitalis ciliata (Scrophulariaceae) by fractionation of the total extracted substances. Its structure was determined as (25R)-5α-spirostan-3β-ol 3-O-β-D-glucopyranosyl-(1→3)[β-D-fucopyranosyl-(1→2)]-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside based on chemical transformations,
physical constants, and spectral data.
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Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 135–137, March–April, 2007. 相似文献
15.
A qualitative classification algorithm for constructing large clusters of aerogel model structures is used. According to this
algorithm, aerogel is classified with polysilicas characterized by a packing of long chains of silicon-oxygen tetrahedra.
A model of the aerogel structure is suggested, according to which aerogel is described as a set of cross-linked chains forming
double or more complex ribbons. This model is in agreement with the conclusions drawn from analysis of the vibration spectra
of its components.
Institute of Surface Chemistry, Ukrainian Academy of Sciences. Russian University of Peoples' Friendship. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 3, pp. 35–38, May–June, 1994.
Translated by O. Kharlamova 相似文献
16.
N. V. Alekseev S. P. Knyazev E. A. Chernyshev I. A. Abronin 《Russian Chemical Bulletin》1998,47(3):367-371
The spatial and electronic structures of some organogermanes with extended coordination spheres of the metal were calculated
using AMPAC and HYPER CHEM 4.0 program packages. Interatomic distances, bond angles, torsion angles, atomic charges, electron
densities, bond orders, parameters of localized and canonical molecular orbitals,etc. were determined. The nature of the additional intramolecular O→Ge interaction in the molecules of these compounds was considered.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 383–387, March, 1998. 相似文献
17.
The natural physiologically active compound gossvpol easily forms clathrate compounds with almost all low-molecular organic
substances. The clathrates and the polymorphs of gossypol with known structures are classified into 24 groups of isostructural
crystals. They differ from each other in the type of molecular association of gossypol. All possible types of gossypol association
with predominant intermolecular H-bonds are analyzed in detail. Zero-, one- and two- dimensional associates are formed; each
type of associate, except the zero-dimensional one, is built from more than one system of interm olecular H-bonds. An attempt
is made to find out the reasons for the diversity of the types of gossypol supramolecular association based on the specific
features of the molecular structure of gossypol.
Translated fromZhurnal Strukturnoi Khimii, Vol. 40, No. 5, pp. 849–871, September–October, 1999. 相似文献
18.
Pectinic substances from the aerial part of Mentha x piperita were isolated and characterized and found to be a mixture of β-(1→4)-glucogalactan (MPG) and two α-(1→4)-rhamnopolygalacturonans (MPP′-1 and MPP′-2). It was shown that the pectin and its components exhibited membrane-stabilizing,
antiatherogenic, and antioxidant activity. Hemicelluloses from M. piperita were a lignocarbohydrate complex.
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Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 411–416, September–October, 2007. 相似文献
19.
In this paper we examine clathrate formation in the tetraisoamylammonium propionate-water binary system. We have found formation
of four polyhydrates, two of which are metastable over the whole temperature range studied. All polyhydrate crystals were
isolated and their compositions and densities determined; for (i-C5H11)4NC2H5COO·36.5H2O, unit cell parameters were additionally found. The results are compared with data for tetra-n-butylammonium carboxylate
polyhydrates, and the structure of the title compounds is suggested. It is confirmed that the isoamyl radical stabilizes the
tetradecahedral void of the clathrate hydrate framework better than the n-butyl radical.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 3, pp. 67–71, May–June, 1994.
Translated by L. Smolina 相似文献
20.
The chemical composition of Pinus silvestris essential oil from contaminated areas was studied. An apparent effect of radionuclides and toxic elements on the biosynthesis
of terpenoids in common pine essential oil was found. Increasing contamination apparently increased the content of sesquiterpenes
and O-containing substances and decreased the content of monoterpenes in the essential oil. The contents of α-pinene, camphene,
and limonene increased and those of 3-carene, terpinolene, and β-pinene decreased in the monoterpene fraction.
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Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 47–49, January–February, 2007. 相似文献