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121.
“True” metal-boron compounds have been known for about ten years. The bonding between the metal and boron atoms can vary widely in nature: Not only simple covalent bonds are encountered but also coordinate bonds and boron-metal multicenter bonds. Furthermore, π complexes of transition metals with boron-nitrogen systems and metal complexes containing boron(I) compounds as ligands have recently also been prepared.  相似文献   
122.
研究了烷基硫酸钠纯度,烷基碳链分布对甲基丙烯酸甲酯种子乳液聚合反应的影响。结果表明,烷基硫酸钠中乙醇不溶物含量的增加,可提高MMA乳液聚合反应速度,在采用K2S2O8-NaHSO3-Cu^2+三元氧化-还原引发体系的MMA乳液聚合中,Fe^2+降低反应速率,而Fe^3+则提高聚合反应速率;  相似文献   
123.
The effect of the quantity of sodium metasilicate and conditioning time in one set of experiments, and the effect of the solution concentration of sodium metasilicate, added at the same dosage and conditioning time to coal slurry, on flotability of a typical Indian coal in another set of experiments are studied. Two sets of 32 full factorial experiments are carried out to assess the effects of the aforementioned variables. The generated data are analyzed quantitatively and explained qualitatively. At 0.1% (w/v) solution concentration of solution added (0.02 g/kg) and 8 min conditioning time, sodium metasilicate acted as activator for kaolinite, whereas at 1.0% (w/v) solution concentration (0.2 g/kg), it acted as dispersant. The best observed condition of depressant is obtained at an added concentration of 10.0% (w/v, 0.2 g/kg) and 8 min conditioning time. The desired effect of the sodium metasilicate can be achieved by controlling its quantity, solution concentration added, and conditioning time.  相似文献   
124.
An in situ photochemical fluorescence probe method for the determination of DNA with sodium 9,10-anthraquinone-2-sulfonate (AQS) as a photochemical fluorescence probe was developed. It was based on the conversion of AQS into an intensively fluorescent product by irradiating with UV radiation. The photochemical reaction is retarded by DNA. The determination can be carried out by measuring the fluorescence intensity at a fixed time. The calibration graph was linear in the range 0–80 ng ml−1 calf thymus (CT) DNA (r = 0.9991), the limit of detection was 3.2 ng ml−1 CT DNA (n = 9). The kinetic behaviour of the photochemical reaction and the effects of experimental conditions were investigated and discussed in detail. The results of absorption spectra and competitive binding experiments suggested the interaction between AQS and DNA to be intercalative.  相似文献   
125.
[60]Fullerene-fused pyrazolines 1 were prepared by the reaction of C60 with alky diazoacetates under the solid-state high-speed vibration milling conditions as well as in toluene solution. Pyrazolines 1 were stable in refluxing toluene and its thermolysis process in 1,2-dichlorobenzene was investigated, the decomposition rates and activation energies of pyrazolines 1 were obtained. The current work demonstrated that the liquid-phase reaction of C60 with alkyl diazoacetates undergoes via 1,3-dipolar cycloaddition pathway at room temperature, or proceeds via carbene mechanism at a temperature of refluxing toluene, thus clarifies the previous ambiguity of its reaction mechanism.  相似文献   
126.
A synthesis and stereochemistry confirmation of a constituent recently isolated from the whole plant Isodon excisus is reported. An enantioselective catalytic boron-mediated reduction of an α-bromoketone was utilized in the key synthetic transformation. The methodology described herein was also used for the synthesis of the natural product's enantiomer and several derivatives. In addition, the compounds were evaluated for inhibitory activity in a caspase induction assay. The natural product was found to be devoid of activity, but several derivatives had moderate inhibitory activity (EC50<1 μM).  相似文献   
127.
The electrical conductivities of sodium chloride and sodium iodide solutions in formamide-water mixtures of different composition have been measured at 25°C. From these data, the limiting equivalent conductances for these salts have been determined. The correspondingWalden products are compared together with the one reported for sodium bromide in the same solvent mixtures, and they are analysed as functions of the anion size. Further, the limiting ionic equivalent conductances are estimated for the different ions. The variation of the ionicWalden products with solvent composition is discussed in terms of ionic solvation and solvent structure.
Elektrische Leitfähigkeit von Halogensalzen in wäßrigen Formamid-Lösungen
Zusammenfassung Es wurden die elektrischen Leitfähigkeiten von Natriumchlorid- und Natriumjodidlösungen in Formamid-Wasser-Mischungen verschiedener Zusammensetzung bei 25°C gemessen. Aus diesen Daten wurden die Grenzäquivalenzleitfähigkeiten für diese Salze bestimmt. Die entsprechendenWalden-Produkte wurden mit den für Natriumbromid in den gleichen Lösungsmittelgemischen berichteten verglichen und hinsichtlich der Anionengrößen analysiert. Außerdem wurden die ionischen Grenzäquivalenzleitfähigkeiten für die einzelnen Ionen abgeschätzt. Die Variation der ionischenWalden-Produkte mit der Lösungsmittelzusammensetzung wurde bezüglich Ionensolvatation und Lösungsmittelstruktur diskutiert.
  相似文献   
128.
马忠龙  张伦  刘昌俊 《催化学报》2003,24(9):645-646
Hydrogenperoxideisagreenoxidantwithgreatpotentialformuchapplication .Thepresentproduc tionofhydrogen peroxiderequiressevereconditionsand generates pollutants .AlternativesynthesesarerequiredandthesynthesisofH2 O2 fromCO ,H2 OandO2 isverypromising .AsshowninEq(1) ,thesynthesisisthermodynamicallyfavored :CO +H2 O +O2 H2 O2 +CO2 (1)ΔG02 98=- 134kJ/mol  ThereactionwasfirstreportedbyZudinetal[1]whousedpalladiumtriphenylphosphaneasacatalyst.Bianchietal[2 ] usedabiphasesystemforthesynthe …  相似文献   
129.
130.
A partial least squares (PLS) Fourier transform Raman spectrometry procedure based on the measurement of solid samples contained inside standard glass vials, has been developed for direct and reagent-free determination of sodium saccharin and sodium cyclamate in table top sweeteners. A classical 22 design for standards was used for calibration, but this system provides accuracy errors higher than 13% w/w for the analysis of samples containing glucose monohydrate. So, an extended model incorporating glucose monohydrate (23 standards) was assayed for the determination of sodium saccharin and sodium cyclamate in all the samples. Mean centering spectra data pre-treatment has been employed to eliminate common spectral information and root mean square error of calibration (RMSEC) of 0.0064 and 0.0596 was obtained for sodium saccharin and sodium cyclamate, respectively. A mean accuracy error of the order of 1.1 and 1.9% w/w was achieved for sodium saccharin and sodium cyclamate, in the validation of the method using actual table top samples, being lower than those obtained using an external monoparametric calibration. FT-Raman provides a fast alternative to the chromatographic method for the determination of the sweeteners with a three times higher sampling throughput than that obtained in HPLC. On the other hand, FT-Raman offers an environmentally friendly methodology which eliminates the use of solvents. Furthermore, the stability of samples and standards into chromatographic standard glass vials allows their storage for future analysis thus avoiding completely the waste generation.  相似文献   
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