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1.
The flow of Russian-language chemical information of 1997 in theChemical Abstracts (CA) database (DB) and in the corresponding parts of the multi-subject database of the Russian Institute for Scientific and
Technical Information (VINITI) is analyzed. The CA coverage corresponds to not only the “Khimiya” (Chemistry) DB but also,
fully or partly, to at least six other VINITI DBs. The total array of the Russian-language documents in these DBs exceeds
that in the CA array almost twofold, even taking into account the possible overlap. This is due to the limited-circulation
(“gray”) literature and nonspecialized journals. The distribution of Russian-language publications among the CA parts and
sections is mapped. Their ranking shows that applied works are presented most fully in CA, some sections of organic and physical
chemistry are presented at a level higher than the average level, and the biochemical part of the Russian-language document
flow appears to be presented most poorly.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 183–187, January, 2000. 相似文献
2.
The flow of Russian-language chemical information of 1997 in theChemical Abstracts (CA) database (DB) and in the corresponding parts of the multi-subject database of the Russian Institute for Scientific and
Technical Information (VINITI) is analyzed. The CA coverage corresponds to not only the “Khimiya” (Chemistry) DB but also,
fully or partly, to at least six other VINITI DBs. The total array of the Russian-language documents in these DBs exceeds
that in the CA array almost twofold, even taking into account the possible overlap. This is due to the limited-circulation
(“gray”) literature and nonspecialized journals. The distribution of Russian-language publications among the CA parts and
sections is mapped. Their ranking shows that applied works are presented most fully in CA, some sections of organic and physical
chemistry are presented at a level higher than the average level, and the biochemical part of the Russian-language document
flow appears to be presented most poorly.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 183–187, January, 2000. 相似文献
3.
V. V. Zverev Z. G. Bazhanova V. M. Vakar' L. V. Ermolaeva V. E. Kataev 《Journal of Structural Chemistry》1995,36(1):87-92
Photoelectron spectra of bis(1,3,6-trimethyluracilyl-5)methane (I) and 1,3,6-trimethyluracil (II) were studied; AM1 optimization
of geometric characteristics was carried out. The total energy minimum and the best agreement between the values of IPm and -ɛm were obtained for conformations with nearly orthogonal location of uracilyl fragments. In such conformations, the highest
occupied orbitals are pseudodegenerate. To interpret the photoelectron spectra, we employed ab initio calculations in STO-3G
and 4-31G basis sets. For uracil and its derivatives, all methods give the π, π, n−, n+, π sequence of the highest orbitals.
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences. Translated
fromZhurnal Struktumoi Khimii, Vol. 36, No. 1, pp. 102–107, January–February, 1995.
Translated by L. Smolina 相似文献
4.
Ab initio quantum chemical calculations of the divinylacetylene molecule with different mutual orientations of vinyl groups
are carried out using the 6–31G*/MP2 basis set. The torsional potential is approximated by a Fourier series. It is shown that
the second term of the series dominates. The enthalpies of the cis- and trans-isomers are nearly equal; the maximum corresponds
to the gosh-orientation (180.4 cm−1 with respect to the cis-form). The vibrational spectra of the compounds with cis-, gosh-, and trans-orientations of vinyl
groups are analyzed based on the ab initio calculations. It is concluded that the experimental data available in the literature
agree with the hypothesis that divinylacetylene exists as cis- and trans-isomers.
Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 610–617, July–August, 1998. 相似文献
5.
N. I. Golovina N. V. Chukanov A. V. Raevskii L. O. Atovmyan 《Journal of Structural Chemistry》2000,41(2):238-242
This paper is a continuation of our series of publications dealing with crystal-lattice processes occuning on heating and
at temperatures near the transition point and accompanied by structural changes in discrete molecules and in the crystal structure
as a whole. The prephase state of 2-bromo-2-nitropropane-1,3-diol crystals and the transition from monoclinic to cubic phase
are studied by IR spectroscopy at 296–391 K.
Translated fromZnumal Strktumo, Chimii, Vol. 41, No. 2, pp. 294–299, March–April, 2000. 相似文献
6.
The Flory–Huggins interaction parameter, χ
23, characterizing the interaction between solvents in a mixed stationary phase has been calculated using inverse gas chromatography
(IGC). The χ
23 parameters for four mixed solvent systems formed by mixing a non-polar branched alkane, 19, 24-dioctadecyldotetracontane
(C78), with four different polar solvents are analysed as a function of temperature. Two of the polar solvents are formed
by replacing one of the –CH3 groups of C78 by –OH (POH) group and –CN (PCN) group and the other two polar solvents are formed by replacing all the four
–CH3 groups of C78 by four –CF3 (TTF) groups and four –OCH3 (TMO) groups. The five solvents have similar structures and nearly the same molar volume and in mixtures, they form regular
solutions. For the mixture, C78 + POH, χ
23 was calculated at two compositions and for the remaining three mixtures χ
23 was calculated at equimolar composition. Eight solute probes representing all possible chemical structures and polarity were
used under conditions approaching infinite dilution. The effects of temperature, concentration of the mixed solvent and probe
solute on χ
23 are presented and discussed. The probe-independent χ
23 values were also calculated by linear regression analysis using the retention data of all the solute probes. In all the mixed
solvents considered here the χ
23 values are probe-dependent and decrease with increase of temperature. 相似文献
7.
V. N. Piottukh-Peletskii B. G. Derendyaev T. F. Bogdanova 《Journal of Structural Chemistry》1997,38(1):126-134
Identification of fragments of organic compounds by the IR spectra of the latter using complete sets of fragments and an IR
database of more than 11,000 complete spectra and structures of organic compounds is treated. Probability and reliability
of identification are estimated, and types of revealed fragments are examined. For many fragments, automatic identification
is possible. The influence of the threshold and nonrandom occurrences of the fragment in the resulting list of structures
on the efficiency of identification are considered. The reliability of identification is justified statistically.
Translated fromZhurnal Struktumoi Khimii, Vol. 38, No. 1, pp. 155–166, January–February, 1997. 相似文献
8.
F. Girardi 《Journal of Radioanalytical and Nuclear Chemistry》1982,69(1-2):15-25
The development and applications of activation analysis in the period 1945–1980 are reviewed. In analysing the number of publications
reported with time three periods can be distinguished: (a) A first period of slow development, up to 1960, in which the technique
showed its very high sensitivity and demonstrated the importance of trace elements; (b) A second period of fast development
(1960–1970) in which all aspects of the technique were developed; (c) A third period (after 1970) in which development occurred
at a rate approximately equal to the average development rate of analytical chemistry, in terms of the number of publications
reported. The present trends shows only minor developments in the methodology, while a good a potential for new and original
applications is evident. The importance of a good scientific knowledge of the specific areas of applications is considered
necessary to properly frame the analytical activities. 相似文献
9.
For the 54 atoms from H to Xe, compact yet accurate segmented Gaussian-type basis sets have been constructed for all electron
calculations. Non-relativistic nZP (Sapporo-nZP) sets for Li–Xe and relativistic nZP (Sapporo-DK-nZP) sets for K–Xe are developed (n = D, T, Q), which efficiently incorporate valence and core electron correlations. Test calculations at the coupled-cluster
level of theory are performed for spectroscopic constants of 12 hydrides of s- and d-block atoms and 12 diatomics of p-block atoms in their ground states. For all molecules, the calculated spectroscopic constants approach to the experimental
values smoothly as the basis set quality increases. 相似文献
10.
The data of ab initio quantum chemical calculations of Β-diketones and their anions performed in split valence-shell bases
are presented. These compounds are of great interest as ligands in numerous chelate complexes. The electronic structures of
substituted enolized Β-diketones containing the period III elements S and Cl are compared. It is shown that using the Huzinaga
pseudopotential for describing core electronic shells makes it possible to adequately reproduce the main peculiarities of
the structure of the outer electronic layers at a qualitative level. The basis used substantial affects on the calculated
values of atomic charges, bond orders, and dipole moments, whereas the one-electron energies are less sensitive to the choice
of the basis.
Translated fromZhurnal Struktumoi Khimii, Vol.40, No. 2, pp. 234–241, March–April, 1999. 相似文献
11.
Thereza Christina Vessoni Penna Marina Ishii Adalberto Pessoa Junior Olivia Cholewa 《Applied biochemistry and biotechnology》2004,114(1-3):469-483
The thermal stability of the recombinant green fluorescent protein (GFPuv) expressed by Escherichia coli cells and isolated by three-phase partitioning extraction with hydrophobic interaction chromatography was studied. The GFPuv
(3.5–9.0 μg of GFPuv/mL) was exposed to various pH conditions (4.91–9.03) and temperatures (75–95°C) in the 10 mM buffers: acetate (pH 5.0–7.0), phosphate (pH 5.5–8.0), and Tris-HCl (pH 7.0–9.0). The extent of protein denaturation (loss
of fluorescence intensity) was expressed in decimal reduction time (D-value), the time exposure required to reduce 90% of the initial fluorescence intensity of GFPuv. For pH 7.0 to 8.0, the thermostability
of GFPuv was slightly greater in phosphate buffer than in Tris-HCl. At 85°C, the D-values (pH 7.1–7.5) ranged from 7.24 (Tris-HCl) to 13.88 min (phosphate) The stability of GFPuv in Tris-HCl (pH>8.0) was
constant at 90 and 95°C, and the D-values were 7.93 (pH 8.38–8.92) and 6.0 min (pH 8.05–8.97), respectively. The thermostability of GFPuv provides the basis
for its potential utility as a fluorescent biologic indicator to assay the efficacy of moist-heat treatments at temperatures
lower than 100°C. 相似文献
12.
13.
Conditions of the sorption preconcentration of Pt, Pd, Au, Ag, and Hg as colored complexes of azorhodanines, tyrodine, and
sulfonitrophenol M from acidic solutions (pH 0–2) on a polyamide membrane in the flow mode are determined. At a flow rate
of 10–20 mL/min, concentrations of determined elements of 10-9-10-7 M, and pressure of 10–20 mm Hg, the complexes are nearly quantitatively sorbed on a polyamide membrane disk (d = 1 cm,m = 2.7 mg, andl = 0.1 mm). The influence of the composition of the test solutions on the formation of the analytical signal in the solid
phase is studied. Rapid sorption-spectrometric procedures are developed for the determination of Pt, Pd, Au, Ag, and Hg with
the detection limit 5–30 ng of the element in the sorbent zone 相似文献
14.
I. I. Guseinov 《Journal of mathematical chemistry》2007,42(3):415-422
Using complete orthonormal sets of Ψα-exponential type orbitals (Ψα-ETOs, α =1, 0, −1, −2, ...) introduced by the author, the series expansion formulae are derived for the two-center integer
and noninteger n STO (ISTO and NISTO) charge densities in terms of integer n STOs at a third center. The expansion coefficients occurring in these relations are presented through the two-center overlap
integrals between STOs with integer and noninteger principal quantum numbers. The general formulae obtained for the STO charge
densities are utilized for the evaluation of two-center Coulomb and hybrid integrals of NISTOs appearing in the Hartee–Fock–Roothaan
approximation. The final results are expressed in terms of both the overlap integrals and the one-center basic integrals over
integer n STOs. It should be noted that the result for the multi-center multielectron integrals with two-center noninteger n STO charge densities presented in this paper were not appeared in our past publications. 相似文献
15.
Sosale Chandrasekhar 《Research on Chemical Intermediates》2005,31(9):779-783
The 'duplication' strategy for the further enrichment of an already enantiomerically-enriched mixture consists of the formation
of all the three possible 'dimeric' diastereomers, i.e., (R)–X–(R), (R)–X–(S) and (S)–X–(S), where X is an appropriate spacer that can be readily cleaved to yield the original enantiomers. The mixture of (R)–X–(R) and (S)–X–(S) thus obtained would be of higher enantiomeric excess (e.e.) as compared to the original mixture, on the basis of a simple
kinetic scheme. The success of the strategy is experimentally well-established, but is apparently based on the (unproven)
assumption that the theoretically-derived rate ratios are identical to the experimentally observed product ratios. Although
the detailed kinetic treatment for a system such as the above is extremely complex, it is possible to show (mathematically)
that the above assumption is indeed justified when all the three diastereomers are formed without chiral discrimination (as
assumed in the strategy). 相似文献
16.
W. Bremser 《Accreditation and quality assurance》1998,3(10):398-402
The principles of uncertainty-based data evaluation are explained. Based on a brief review of recent publications on the
topic, examples for application to standard procedures in analytical chemistry – calibration, method validation, standard
addition etc., – are given. The performance and the advantages of uncertainty-based data evaluation are discussed.
Received: 4 July 1998 · Accepted: 6 July 1998 相似文献
17.
Debbie J. Beard Sumer A. Barakat Nathanael B. Lockhart Chandler R. Pace Charles U. Pittman Jr. Burnette W. Hamil Svein Saebo 《Structural chemistry》2012,23(2):351-357
A systematic computational study of four-membered cyclic ketene –O,O–, –O,S–, –O,N–, –S,N– and –N,N-acetals as well as their protonated analogs have been performed at the second order M?ller Plesset level with a polarized
triple zeta basis set. The main purpose of this study was to make predictions about the nucleophilicity of these systems and
the variations in nucleophilicity with the hetero atoms. Our calculations suggest that all six target molecules are good nucleophiles,
and that the N,N analog is the strongest and the S,S analog the weakest nucleophile. Our results include molecular geometries, bond lengths, proton affinities, vibrational frequencies,
and calculated charges. 相似文献
18.
C. Vanderdonckt M. Krumova F. J. Baltá Calleja H. G. Zachmann S. Fakirov 《Colloid and polymer science》1998,276(2):138-143
Poly(ethylene terephthalate) (PET) was annealed in vacuum at different temperatures (190–260 °C) for different times (10 min–24 h)
in order to examine the mechanical properties (microhardness) of PET samples with a wide range of molecular weights (10 000–120 000).
Short annealing times result in a twofold decrease in mol. wt. due to hydrolytic decomposition. However, long annealing times
give rise to a substantial molecular weight increase. It is found that microhardness (H) rises linearly with the degree of crystallinity obtained during up-grading of mol. wt. and its extrapolation leads to H-values of completely crystalline PET, H
PET
c=405 MPa for samples with conventional mol. wt. and of 426 MPa for samples with mol. wt. higher than 30 000. It is shown that
the increase of mol. wt. for each set of samples with a given range of degree of crystallinity also causes a slight increase
of H. The influence of mol. wt. upon hardness is discussed in the light of the changes in the physical structure (crystallinity,
crystal thickness) which is formed at given heat treatment conditions.
Received: 29 April 1997 Accepted: 23 September 1997 相似文献
19.
A theoretical charge density study on nitrogen-rich 4,4′,5,5′-tetranitro-2,2′-bi-1H-imidazole (TNBI) energetic molecule 总被引:1,自引:0,他引:1
P. Srinivasan S. N. Asthana Rajesh B. Pawar P. Kumaradhas 《Structural chemistry》2011,22(6):1213-1220
The bond topological and electrostatic properties of nitrogen-rich 4,4′,5,5′-tetranitro-2,2′-bi-1H-imidazole (TNBI) energetic
molecule have been calculated from the DFT method with the basis set 6-311G** and the AIM theory. The optimized geometry of
this molecule is almost matched with the experimental geometric parameters. The electron density at the bond critical point
and the Laplacian of electron density of C–NO2 bonds are not equal, one of them is much weaker than the other. Similar trend exists in the C–N bonds of the imidazole ring
of the molecule. The ratio of the bond dissociation energy (BDE) of the weakest bond to the molecular total energy exhibits
nearly a linear correlation with the impact sensitivity; its h
50% value is ~32.01 cm. The electrostatic potential around both the nitro groups are found unequal; the NO2 group of weakest C–NO2 bond exhibits an extended electronegative region. 相似文献
20.
Permethrin is the most popular synthetic pyrethroid insecticide used in agriculture and public health. For the assessment
of human exposure to permethrin, a competitive indirect enzyme-linked immunosorbent assay (ELISA) for the detection of the
glycine conjugate of a major metabolite, cis-/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DCCA), of permethrin was developed based on a polyclonal
antibody. An assay based on an antibody with a high sensitivity was optimized and characterized. The IC50 value and the detection range for trans-DCCA–glycine, in the assay buffer were 1.2 and 0.2−7.0 μg/L, respectively. The antibody recognized trans-DCCA–glycine and the mixture of cis-/trans-DCCA–glycine with an isomer range from 30:70 to 50:50 nearly equally. Little or no cross-reactivity to permethrin and its
other free metabolites or glycine conjugates was measured. The integration of the ELISA and solid-phase extraction which was
used to reduce the matrix effect from human urine samples provided for analysis of total cis-/trans-DCCA–glycine at low parts per billion levels in the samples. The limit of quantitation of the target analyte was 1.0 μg/L
in urine with a limit of detection of 0.1 μg/L in buffer. This assay might be a useful tool for monitoring human exposure
to permethrin. 相似文献