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991.
Vytautas Getautis Giedre Sinkeviciute Albina Stanisauskaite 《Monatshefte für Chemie / Chemical Monthly》2007,138(5):477-480
Summary. A synthesis of 1,2-diphenylpyrazolidin-4-ol via direct heterocyclization of 1,2-diphenylhydrazine with 1-chloro-2,3-epoxypropane, its O-epoxypropyl-, O-ethyl-, and O-benzylderivatives are described. Novel hydrazone derivatives with pyrazolidine units were also synthesized. The compounds
were characterized by spectroscopic methods as well as elemental analyses. 相似文献
992.
B. Schoofs T. Mouganie B. A. Glowacki V. Cloet S. Hoste I. Van Driessche 《Journal of Sol-Gel Science and Technology》2007,41(2):113-122
Today, the deposition of coated conductors on a variety of substrates is often performed using a vacuum or low pressure technique.
However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and attaining independence
of geometric constraints of the substrates are areas in which vacuum techniques will need sustained development in order to
answer industrial demands. The development of the next generation of deposition methods, based on deposition under atmospheric
environment and from aqueous precursor solutions is a real challenge. This work describes the deposition of thin NdBa2Cu3O7-y layers on SrTiO3 single crystals based on a new sol-gel dip coating process using aqueous precursor solutions. Two inorganic aqueous sol-gel
routes were investigated, a metal nitrate–citric acid based and a metal acetate–triethanol amine based solution. Using detailed
thermal analysis, it is shown that adjusting the different parameters during thermal treatment can be used to control the
morphology of the films. Also special attention is given to the microstructure of the thin film because of its relevance to
the superconducting transport properties of the coated conductor system. 相似文献
993.
The US National Institute of Standards and Technology (NIST) participated in an international interlaboratory study under
the auspices of the Consultative Committee for Amount of Substance (CCQM) for the determination of 19-norandrosterone (19-NA)
in urine, the principal metabolite of nandrolone and certain other synthetic testosterone substitutes banned for use by the
World Antidoping Agency (WADA). Prior to this study, NIST developed a candidate reference measurement procedure based upon
isotope dilution liquid chromatography/tandem mass spectrometry. This method was applied to a urine sample distributed to
the participants in the study by the Australian National Measurement Institute, Pymble, Australia (NMIA). The NIST results
were in very good agreement with those from the other participants, all of whom used methods based upon gas chromatography/mass
spectrometry. All known significant sources of uncertainty were evaluated, resulting in a relative expanded uncertainty of
less than 5% (coverage factor k = 2). 相似文献
994.
Alexander Apelblat Emanuel Manzurola Zoya Orekhova 《Journal of solution chemistry》2007,36(8):1023-1035
Conductivity measurements of glutaric acid and disodium glutarate in dilute aqueous solutions were performed in the 288.15
to 323.15 K temperature range. The limiting equivalent conductances of glutarate anions, λ
o(HGlut−,T) and λ
o(1/2Glut2−,T), and the dissociation constants of glutaric acid, K
1(T) and K
2(T), were derived by the use of the Onsager and the Quint and Viallard conductivity equations. The applied molecular model was
successfully confirmed by analyzing the conductivities of sodium hydrogen glutarate at 298.15 K. 相似文献
995.
Shinsaku Fujita 《Journal of mathematical chemistry》2007,42(2):215-263
The concepts of double coset representations and sphericities of double cosets are proposed to characterize stereoisomerism, where double cosets are classified into three types, i.e., homospheric double cosets, enantiospheric double cosets, or hemispheric double cosets. They determine modes of substitutions (i.e., chirality fittingness), where homospheric double cosets permit
achiral ligands only; enantiospheric ones permit achiral ligands or enantiomeric pairs; and hemispheric ones permit achiral
and chiral ligands. The sphericities of double cosets are linked to the sphericities of cycles which are ascribed to right
coset representations. Thus, each cycle is assigned to the corresponding sphericity index (a
d
, c
d
, or b
d
) so as to construct a cycle indices with chirality fittingness (CI-CFs). The resulting CI-CFs are proved to be identical
with CI-CFs introduced in Fujita’s proligand method (S. Fujita, Theor. Chem. Acc. 113 (2005) 73–79 and 80–86). The versatility
of the CI-CFs in combinatorial enumeration of stereoisomers is demonstrated by using methane derivatives as examples, where
the numbers of achiral plus chiral stereoisomers, those of achiral stereoisomers, and those of chiral stereoisomers are calculated
separately by means of respective generating functions. 相似文献
996.
Mikhail H. Klin Serge S. Tratch Nikolai S. Zefirov 《Journal of mathematical chemistry》1991,7(1):135-151
We give a necessary and sufficient condition for a reaction graph of a degenerate rearrangement to be connected. This condition is formulated in terms of vertex stabilizers of the automorphism group of a molecular graph. The condition is illustrated on several examples, including the reaction graph of bullvalene. We consider different mathematical models for the construction of reaction graphs and state the problem: which of the models is more adequate? 相似文献
997.
Boris Mahltig Jean-François Gohy Sayed Antoun Robert Jérôme Manfred Stamm 《Colloid and polymer science》2002,280(6):495-502
This paper reports on the pH-dependent adsorption of weak the polyelectrolytic diblock copolymer poly(2-vinylpyridine)-block-poly(dimethylaminoethyl methacrylate), (PVP-b-PDMAEMA). Aqueous PVP-b-PDMAEMA solutions have been adsorbed on alkaline pretreated silicon substrates. Altogether two copolymers differing in block ratio and molecular weight were used for the investigations. While the electrical charge of both samples in solution was investigated by electrophoretic measurements, the adsorbed polymer layers were studied with ellipsometry and atomic force microscopy (AFM). Depending on pH the electrical charge of both blocks of the diblock copolymer varied. Three different regimes have been identified. Under acidic conditions at pH<5, both blocks are mainly positively charged. At medium pH between 5 and 8, only the PDMAEMA block is positively charged. At pH>8, both blocks are nearly uncharged and a polymer precipitation occurred in solution. Each of these pH regimes was characterized by a specific adsorption behaviour leading to two adsorption maxima at acidic and alkaline pH values, while at medium pH a plateau in the adsorbed amount was observed. Moreover, the structures of the polyelectrolytes formed on the substrate after adsorption were specific to each of the three pH regimes. 相似文献
998.
In the previous paper in this issue we have demonstrated that it is possible to measure the five different relaxation rates of a deuteron in (13)CH(2)D methyl groups of (13)C-labeled, fractionally deuterated proteins. The extensive set of data acquired in these experiments provides an opportunity to investigate side-chain dynamics in proteins at a level of detail that heretofore was not possible. The data, acquired on the B1 domain of peptostreptococcal protein L, include 16 (9) relaxation measurements at 4 (2) different magnetic field strengths, 25 degrees C (5 degrees C). These data are shown to be self-consistent and are analyzed using a spectral density mapping procedure which allows extraction of values of the spectral density function at a number of frequencies with no assumptions about the underlying dynamics. Dynamics data from 31 of 35 methyls in the protein for which data could be obtained were well-fitted using the two-parameter Lipari-Szabo model (Lipari, G.; Szabo, A. J. Am. Chem. Soc. 1982, 104, 4546). The data from the remaining 4 methyls can be fitted using a three-parameter version of the Lipari-Szabo model that takes into account, in a simple manner, additional nanosecond time-scale local dynamics. This interpretation is supported by analysis of a molecular dynamics trajectory where spectral density profiles calculated for side-chain methyl sites reflect the influence of slower (nanosecond) time-scale motions involving jumps between rotameric wells. A discussion of the minimum number of relaxation measurements that are necessary to extract the full complement of dynamics information is presented along with an interpretation of the extracted dynamics parameters. 相似文献
999.
Natalia V. Loginova Tat’yana V. Koval’chuk Rimma A. Zheldakova Anna A. Chernyavskaya Nikolai P. Osipovich Gennady K. Glushonok Henry I. Polozov Victor L. Sorokin Oleg I. Shadyro 《Central European Journal of Chemistry》2006,4(3):440-457
Cu (II) complexes with the sterically hindered diphenol derivatives 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzenetriol (II) and the sulfur-containing 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements.
Compounds I–III can coordinate in their singly deprotonated forms and act as bidentate ligands. These compounds yield Cu (II) complexes of the stoichiometry Cu(L)2, which have square planar geometry (g| > g⊥ > ge). Unlike them, compound IV behaves as a terdentate ligand, and its complex Cu(LIV)2 has distorted octahedral geometry. According to ESR data, only the Cu(LII)2 complex contains a very small amount of phenoxyl radicals. Antimicrobial activities of these ligands and their respective
Cu (II) complexes have been determined with respect to Gram-positive and Gram-negative bacteria, as well as on yeasts. Their
phytotoxic properties against Chlorella vulgaris 157 were also examined. 相似文献
1000.
Ren Yan-Wei Dang Li-Long Li Jun Gao Wei-wei Zhang Feng-Xing 《Journal of Structural Chemistry》2005,46(2):352-357
A novel one-dimensional (1D) chain coordination polymer [Mn2(2,2′-dipha)2(phen)]n has been synthesized by hydrothermal reaction, and characterized by elemental analysis, IR spectroscopy, TGA, and X-ray diffraction. Orange crystals crystallized in the monoclinic system, space group C2/c with a = 19.393(7) Å, b = 19.183(7) Å, c = 19.729(7) Å, β = 90.826(6)°, V = 7338(5) Å3, Z = 8. In the crystal structure, one manganese atom is six-coordinated with four carboxylate oxygen atoms from one pentadentate 2,2′-dipha ligand and two tetradentate 2,2′-dipha ligands, and with two nitrogen atoms of one phen ligand, giving a slightly distorted octahedral geometry. The other manganese atom is five-coordinated with five oxygen atoms from two tetradentate 2,2′-dipha ligands and two pentadentate 2,2′-dipha ligands and has a trigonal bipyramidal environment. The TGA curve shows that the compound is stable below 310°. 相似文献