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991.
Yüksel Tufan Nurcan Karacan J. Eric D. Davies 《Journal of inclusion phenomena and macrocyclic chemistry》1999,33(2):149-154
Four new clathrates of the formula M(Im)2Ni(CN)4·2·Dioxane (where M = Co, Ni, Cu, Cd; Im = Imidazole) have been prepared in powder form and their FT-IR and laser-Raman spectra are reported for the first time. These clathrates are analogues to the previously reported classical Hofmann type clathrates except for the copper clathrate. The Cu clathrate has different spectral features in comparison with its analogues due to the Jahn-Teller effect. 相似文献
992.
固定pH滴定法测定弱酸弱碱性药物 总被引:8,自引:0,他引:8
报道一种水溶液吕测定弱酸弱碱性药物的新型滴定分析方法-固定pH滴定法,其理论基础是弱酸弱碱在水溶液中各种存在形式的分布系数在pH值固定时为常数,对甲硝唑,盐酸美西律等离散常数在10^-8至10^-11范围内的7种弱酸弱碱性药物进行测定。结果与药典法吻合,回收率在99.4%~100.6%,方法简便,快速,准确,制剂中的赋形剂及色物不影响测定。 相似文献
993.
Summary The highly complex matrix of diesel particulate extracts was analyzed for nitrated polycyclic aromatic hydrocarbons (nitro-PAH)
using fused-silica capillary-column gas chromatography along with a thermionic nitrogen-phosphorus detector (TID) and high-performance
liquid chromatography followed by on-line catalytic reduction of the nitro-PAH to amino-PAH and subsequent fluorescence detection.
Positive isomer identification and quantitation of nitro-PAH are from retention times of authentic standards and their mass
spectra. The ease of nitro-PAH formation by nitration of PAH raises the question regarding the origin of these species, whether
they are produced as “native” products during the engine combustion process and/or in the exhaust, or instead, formed as the
result of chemical conversion to produce artifacts during the sampling procedure. This problem is assessed examing 1-nitropyrene-concentration
in particulates of three light-duty diesel engines for different sampling times. 1-Nitropyrene concentrations show only a
moderate increase with sampling time under average sampling conditions.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
994.
Klärner FG Lobert M Naatz U Bandmann H Boese R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(20):5036-5047
The novel trimethylene-bridged clips 3 and 4 have been synthesized by using repetitive stereoselective Diels-Alder reactions of the benzo- and naphthobismethylenenorbornenes 8 and 19 as dienes and norbornadiene 9 as bisdienophile, and subsequent dehydrogenation of the primary cyclobisadducts 10 and 20 by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Clips 3 and 4 serve as receptors for a variety of electron-deficient neutral and cationic aromatic substrates, comparable to the molecular tweezers 1 and 2. The thermodynamic parameters of the complex formation, K(a) and DeltaG, were determined by (1)H NMR titration experiments and, in the case of the highly stable complex TCNB 32@4, by the use of isothermal titration microcalorimetry. The finding that clip 4 forms more stable complexes than 3 can be explained by the larger van der Waals contact surfaces of the naphthalene sidewalls in 4 compared to the corresponding benzene systems in 3. In the complexes with 4 as receptor, the plane of each aromatic substrate molecule is calculated to be oriented almost parallel to the naphthalene sidewalls. However, in the complexes of tweezers 2, the substrate is usually oriented parallel to the central naphthalene spacer unit. Due to the more open topology of 4, most complexes were calculated to consist of two or more equilibrating noncovalent conformers. 相似文献
995.
S. V. Nochur G. R. Jacobson M. F. Roberts A. L. Demain 《Applied biochemistry and biotechnology》1992,37(1):33-41
Fungi were screened for important industrial enzymes produced from industrial chips and sawdust of laurel (Louro inamui, Ocotea cymbarum) and cedar (Cedro, Cedrella odorata). Seven hyphomycetes and one zygomycete were isolated and characterized. Two different media for testing the enzymatic activities
were used. In general, in potato dextrose (1%) medium (M-3) a preponderancy of ligninolytic over cellulolytic enzymes was
observed. In potato infusion-sawdust wood (1%) medium (M-4) the cellulolytic, xylanolytic, and lipolytic enzymes were efficiently
induced. Significant modulation of enzyme production by the carbon source was found in the extracted fungi from self-heated
industrial chips piles of cedar and laurel trees at the Amazonian region. 相似文献
996.
Nils Siegbahn Mats-Olle Maånsson Klaus Mosbach 《Applied biochemistry and biotechnology》1987,12(2):91-105
A soluble, bifunctional enzyme complex has been prepared by crosslinking lactate dehydrogenase and alcohol dehydrogenase with
glutaraldehyde. The crosslinking was performed on a solid phase while the active sites of alcohol dehydrogenase and lactate
dehydrogenase were held adjacent to one another with the aid of a bis-NAD analog. Subsequently, the enzyme complex was released
from the solid phase. The soluble enzyme complex was then purified by using NAD-Sepharose as an affinity adsorbent. Based
on gel filtration experiments, the complex was estimated to consist of one of each dehydrogenase.
By using a third enzyme, lipoamide dehydrogenase, which competes with lactate dehydrogenase for NADH produced by alcohol dehydrogenase,
the effect of site-to-site orientation was studied. It was found that about 83% of the NADH produced by alcohol dehydrogenase
was oxidized by site-to-site oriented lactate dehydrogenase compared to a figure of only about 61% obtained in an identical
system of separate enzymes. This indicates that given two alternative routes, the preference for the one to lactate dehydrogenase
over the one to lipoamide dehydrogenase is enhanced when lactate dehydrogenase and alcohol dehydrogenase are site-to-site
oriented. 相似文献
997.
N. N. Zemlyanskii I. V. Borisova A. K. Shestakova Yu. A. Ustynyuk E. A. Chernyshev 《Russian Chemical Bulletin》1998,47(3):469-474
The first stable dibenzosilafulvene, 9-{[8-(dimethylaminomethyl)-1-naphthyl]phenylsil-1-ylium}fluoren-9-ide (7a), was obtained in one step from 9-fluorenyllithium and chloro[8-(dimethylaminomethyl)-1-naphthyl]phenylsilane as a stable
solvate with THF. The structure of the zwitterionic compound7a was established by1H,13C, and29Si NMR in solution and in the solid state. The reactions of compound7a with crotonaldehyde, ethanol, and triethylethylidenephosphorane are described. The data on the synthesis of alkoxy- and alkylthiochloro-9-fluorenylsilanes
and their phosphonium salts are given.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 486–491, March, 1998. 相似文献
998.
Diffusion coefficients of copper sulfate-water and copper sulfate-sulfuric acid-water solutions have been determined at 25°C using conductimetric and diaphragm-cell techniques. The ternary diffusion measurements indicate that diffusion of sulfuric acid can produce large counterflows of copper sulfate and vice versa. If diffusion of copper sulfate in aqueous sulfuric acid solutions is treated as a binary process, the measured apparent diffusivities of copper sulfate can be 1 to 8% lower than the salt's true diffusivity. Equations are developed to predict transport coefficients from the concentrations and mobilities of the diffusing species. 相似文献
999.
High-quality online course materials were reconstructed through feedback from undergraduate students and online data analysis regarding constructed learning materials on the Chao Xing Learning Platform. They were used for studying organic chemistry courses online and offline in university for nationalities. This model, based on student-centered teaching, can effectively transform students from passively accepting knowledge to actively learning and internalizing knowledge. This strategy can also enhance the students' learning initiative and the effects of learning, and hopefully be helpful to the universities in multi-ethnic areas in developing fundamental disciplined construction of organic chemistry and other courses. 相似文献
1000.
The reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for determination of lercanidipine hydrochloride and its synthetic impurities, degradation and oxidative products in Carmen® tablets. The best separation was performed on Zorbax SB C18 column, 250 x 4.6 mm, particle size 5 m. Acetonitrile-water-triethylamine 55:44.8:0.2 (v/v/v) was used as a mobile phase with flow rate 1 mL min–1. pH was adjusted to 3.0 with orthophosphoric acid. UV detection was performed at 240 nm. Duration of chromatographic run was about 12 min for six examined compounds. The chromatographic conditions for the determination of lercanidipine hydrochloride and its related substances were the same, but the concentration of lercanidipine hydrochloride was 0.03 mg mL–1 for assay and 0.3 mg mL–1 for related substances. The validation of the method performance characteristics (figures of merits, quality of parameters) was established to be adequate for the intended use. The evaluation of number of parameters, such as selectivity, linearity, accuracy, specificity, precision (repetability and reproducibility), sensitivity and detection and determination limits is entailed.Acknowledgements This work was supported by the Institute of Pharmacy of Serbia, Belgrade and by the Ministry for Science, Technology and Development of Serbia, Contact: 1458 相似文献