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61.
Anufriev V. Ph. Polonik S. G. Pokhilo N. D. Balanyova N. N. 《Russian Chemical Bulletin》2003,52(10):2247-2250
The Friedel—Crafts acylation of trimethylhydroquinone, 3,5-diethyl-2-hydroxyhydroquinone, and 3,5-diethyl-1,2,4-trimethoxybenzene with dichloromaleic or citraconic anhydride in an AlCl3—NaCl melt is accompanied by o-C-dealkylation to afford functionally substituted naphthazarins. 相似文献
62.
63.
The mass spectra of eleven 1,2,4-triazepines with oxo, thioxo, methoxy and methylmercapto groups in the 3 and 5 positions are reported and analysed. Each of the five structures of the triazepine ring present is characterized by a particular group of fragmentations. 相似文献
64.
J. P. Durand F. Dawans Ph. Teyssie 《Journal of polymer science. Part A, Polymer chemistry》1970,8(4):979-990
In the course of investigations of polymerization of diolefins by transition metal derivatives, we have synthesized various monometallic nickel coordination catalysts. The complexes were prepared by reacting 2,6,10-dodecatriene-1,12-diyl nickel with protonic acids; they were shown to initiate the stereospecific polymerization of 1,3-butadiene. The study of these catalysts showed the strong influence of the nature of the counteranion used on the stereospecificity and the polymerization rate. Moreover, by adding various ligands, we were able to modify the behavior of the catalytic systems and to prepare either pure cis-1,4 or pure trans-1,4 or cis–trans equibinary polybutadienes, starting from the same complex and keeping a high 1,4 specificity. Some of these modifications were shown to be reversible. 相似文献
65.
The investigations performed in this work have demonstrated that an easy-axis frustrated non-Heisenberg magnet can contain homogeneous phases with the vector (ferromagnetic) and tensor (nematic) orderings, as well as a spatially inhomogeneous phase of the magnetic spiral type. Depending on the relationships between the material parameters, either a ferromagnetic spiral or a spiral of the quadrupole–ferromagnetic type with different periods of the spiral structures can be formed in the system. The phase diagram of the system has been constructed. 相似文献
66.
There have been performed experimental measurements of effective thermal conductivity of silica-gel for a stagnant cylindrical fixed bed under transient and steady state conditions in the presence of dry air at different pressures and for different amounts of adsorbed water. The Bauer-Schlünder and Kunii-Smith models have been used to identify the thermal solid conductivity of silica gel pellets from measurements of the conductivity in an adsorbent bed. Sorption rates of water vapor in silica gel were measured using a single-step thermal method by monitoring the sample surface temperature by infrared detection. In order to obtain the mass diffusivity it is necessary to match the numerical solution of the mathematical model to the experimental data. 相似文献
67.
I. Barakat Ph. Dubois Ch. Grandfils R. Jrme 《Journal of polymer science. Part A, Polymer chemistry》2001,39(2):294-306
Living ω‐aluminum alkoxide poly‐ϵ‐caprolactone and poly‐D,L ‐lactide chains were synthesized by the ring‐opening polymerization of ϵ‐caprolactone (ϵ‐CL) and D,L ‐lactide (D,L ‐LA), respectively, and were used as macroinitiators for glycolide (GA) polymerization in tetrahydrofuran at 40 °C. The P(CL‐b‐GA) and P(LA‐b‐GA) diblock copolymers that formed were fractionated by the use of a selective solvent for each block and were characterized by 1H NMR spectroscopy and differential scanning calorimetry analysis. The livingness of the operative coordination–insertion mechanism is responsible for the control of the copolyester composition, the length of the blocks, and, ultimately, the thermal behavior. Because of the inherent insolubility of the polyglycolide blocks, microphase separation occurs during the course of the sequential polymerization, resulting in a stable, colloidal, nonaqueous copolymer dispersion, as confirmed by photon correlation spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 294–306, 2001 相似文献
68.
Guidelines ISO 17025 and ISO 15189 aim to improve the quality-assurance scheme of laboratories. Reliable analytical results are of central importance due to the critical decisions that are taken with them. ISO 17025 and ISO 15189 therefore require that analytical methods be validated and that laboratories can routinely provide the measurement uncertainty of the results of measurements. To evaluate the fitness of purpose of analytical methods, total error is increasingly applied to assess the reliability of results generated by analytical methods. However, the ISO requirement to estimate measurement uncertainty seems opposed to the concept of total error, leading to delays in laboratories implementing ISO 17025 and ISO 15189 and confusion for the analysts. This article therefore aims to clarify the divergences between total error and measurement uncertainty, but also to discuss their main similarities and emphasize their implementation. 相似文献
69.
Summary A high-performance liquid chromatographic method for the simultaneous determination of urinary organic acids and creatinine for following the metabolism of aromatic solvents is reported. After extraction of acidified, filtered urine with diethylether followed by evaporation, the dried residue is dissolved in mobile phase. Hydroxybenzoic acid is used as internal standard. A column of Nucleosil C18 is used with a precolumn of the same material. The mobile phase is acetonitrilephosphate buffer, pH 3.3 (1783). For determination of creatinine the sample is simply diluted 10-fold and the eluate monitored at 215 nm (UV). This technique gives highly reproducible results and is simple, reliable and useful for biological monitoring. 相似文献
70.
New very effective results on the liquid-phase oxidation of cyclohexene to cyclohexanone by nitrous oxide are analyzed using the B3LYP/6-31G* approximation to predict a two-step reaction mechanism correlated with the experimental data. 相似文献