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931.
X. Y. Li G. J. Wang J. G. Sun Y. T. Zheng B. Yan H. T. Xie X. Wang 《Chromatographia》2007,65(1-2):13-18
To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea
(G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS)
method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte
was analyzed on a Kromasil C18 column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow
rate was 0.2 mL min−1. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion
monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was
linear over the concentration range of 2.0–500.0 ng mL−1. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV).
This validated method was successfully applied to the pharmacokinetics of G004 in rats. 相似文献
932.
M M Ayad G B El-Hefnawy G W Bahlol 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(1):161-166
The spectrophotometric and thermodynamic properties of different substituted methylnaphthalenes charge transfer (CT) complexes with tetracyanoethylene have been studied in carbon tetrachloride. The spectral characteristics of the CT bands have also been discussed in relation to the positions of methyl groups. The formation constants and the spectral properties of the complexes are markedly affected with the substitution position of the methyl groups. The ionization potentials of the donors are determined. 相似文献
933.
Three multivariate techniques (principal components analysis, correspondence factor analysis and spectral map analsis) are applied to x-ray fluorescence data from glass-making objects from the 5th century AD found in Tarragona (Tarraco in the Roman Empire). The information obtained by displaying th eobjects and variables in each reduced factor space is compared. The presence of redundant information is shown. The visualization of groups of objects and of the relationship between objects and variables allows the formulation of hypotheses concerning the origin of the samples and the presence of local glassworks. 相似文献
934.
V. Kolarik M. Juez-Lorenzo W. Engel N. Eisenreich 《Fresenius' Journal of Analytical Chemistry》1993,346(1-3):252-254
Summary The formation of -Fe2O3 on Fe3O4 during the oxidation of iron below 570°C occurs very slowly and the scales are so thin that they cannot be detected by microscopy. X-ray diffraction with grazing incidence, equipped with a high temperature device, allows an in situ study of the -Fe2O3 formation even the initial reactions. The formation of -Fe2O3 was studied in isothermal experiments at 400, 450, 500 and 550°C. -Fe2O3 could already be detected at the beginning of the experiments. The difference method, a numerical treatment for kinetic evaluation, yields curves showing the growth of the -Fe2O3 layer. Fitting the parabolic time law to these curves yields the rate constants. 相似文献
935.
Frank W. Harris Steve O. Norris 《Journal of polymer science. Part A, Polymer chemistry》1973,11(9):2143-2151
A series of phenylated polydihydrophthalimides has been synthesized by the Diels-Alder reactions of 3,3′-(oxydi-p-phenylene)bis(2,4,5-triphenylcyclopentadienone) and 3,3′-(p-phenylene)bis(2,4,5-triphenylcyclopentadienone) with N,N′-o-, -m-, and -p-phenylenedimaleimide. The polydihydrophthalimides were soluble in dimethylformamide (DMF) and had intrinsic viscosities that ranged from 0.33 to 1.01, the polymers were dehydrogenated thermally and chemically to afford the corresponding phenylated polyphthalimides. The totally aromatic polyimides were also soluble in DMF but had intrinsic viscosities only as high as 0.41. The thermogravimetric analyses of the polyphthalimides showed breaks near 530°C in air and in nitrogen atmospheres. 相似文献
936.
The irradiations of 1, 1-dimethyl- (8), 1, 1-di-(tri-deuteriomethyl)- (d6– 8 ), 1, 1, 2, 2-tetramethyl- ( 9 ) and cis- and trans-1, 2-dimethyl-1, 2-dihydronaphthalenes (cis- and trans- 10 ) were investigated in 2, 2-dimethylbutane/pentane at ?100° using a mercury high-pressure lamp, and with mercury high- and low-pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following: 1. The 1, 2-dihydronaphthalenes undergo a conrotatory ring opening to the o-quinodimethanes on irradiation with high- or low-pressure lamps at room temperature or at ?100°. Thermal reactions ([1, 7a]H-shifts, electrocyclisations) are suppressed at ?100°. The o-quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis- 10 (scheme 6) undergo on irradiation with the high-pressure lamp, [1, 5]H-shifts or photochemical Diels-Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex-2-ene derivatives. These Diels-Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions. 2. If the 1, 2-dihydronaphthalenes are irradiated at room temperature with either a high- or a low-pressure lamp, then the initially formed o-quinodimethanes undergo thermal [1, 7a]H-shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o-quinodimethanes are formed on irradiation of 8, 9 and cis- 10 . From trans- 10 , an o-quinodimethane mixture is formed, of which one component (cis, cis- 22 ) undergoes thermal [1, 7a] H-shifts, while the other (trans, trans- 22 ) suffers a thermal disrotatory electrocyclisation to give cis- 10 . If a high-pressure lamp is used in the last experiment, then the competing photochemical Diels-Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans- 22 . As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels-Alder reactions or [1, 5]H-shifts in the o-quinodimethanes require light of wavelength ? 400 nm (high-pressure lamp). The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2-dihydronaphthalenes [2]. 相似文献
937.
Glyoxaldiimines (I) RN=CHCH=NR show in the NMR a downfield shift of glyoxalic protons (Hgly) when complexed to (II: M = Mo, W), but increasing high field shifts when going to (III) and complexes (IV). In the tungsten complexes II HglyW coupling satellites are resolved (J(WH) ≈4–6 Hz); in the phosphine compounds III, IV long range PHgly coupling is clearly visible. Mechanisms of spinspin interaction are briefly discussed in connection with the EPR results on monoanionic radicals of II–IV. 相似文献
938.
939.
研究了高频超声应用中带无穷退化记忆项的Moore-Gibson-Thompson方程τu_(ttt)+α(x)u_(tt)-c^(2)Δu-bΔu_(t)+∫^(∞)_(0)g(s)div[a(x)▽u(t-s)]ds=0解的适定性和衰减速率,其中非负函数a(x)和α(x)是可退化的并满足a(x)+α(x)≥δ>0.该系统是由黏性热松弛流体中波传播模型的线性化而得到的.通过使用Faedo-Galerkin逼近和能量估计,证明了解的适定性.在适当的假设下,通过构造适当的李雅普诺夫泛函,建立了能量的指数或一般衰减结果. 相似文献
940.