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991.
Momentum transfer was investigated in an unbaffled agitated vessel of inner diameter 0.3 m equipped with different off-centred
impellers. The distribution of the shear rate on the tank wall as a function of the impeller type and Reynolds number was
studied in the turbulent regime of the Newtonian liquid flow. The dependences of the averaged dimensionless shear rate, friction
coefficient, and dissipated energy on the Reynolds number and eccentricity ratio were approximated using four-parameter equations.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献
992.
C. Santos 《European Polymer Journal》2006,42(12):3277-3285
Chitosan samples with different N-deacetylation levels were obtained from β-chitin under heterogeneous alkali conditions. Oxidative depolymerisation was performed to attain low-acetylated chitosan samples with different molecular mass. Water vapour permeability, membrane swelling and tensile mechanical properties were analysed in plasticized self-supporting chitosan membranes. The main purpose was to describe unambigously the effect of the biopolymer molecular mass and acetylation degree on these properties. Commercially available chitosan samples derived from α-chitin were also studied for comparison. The equilibrium degree of swelling in water and the water vapour permeability increase by increasing the molecular mass or the degree of acetylation. Regarding the effect on the mechanical properties, generally harder and tougher membranes were obtained for chitosans with higher molecular mass or lower acetylation degree. These observations are tentatively explained based on the different structural characteristics of the polymer and can lead to a better understanding of the tools necessary to tailor a specific type of chitosan membrane. 相似文献
993.
The type of interaction in quasi-binary system CuInSe2 (CIS)-CdSe was investigated using differential thermal and X-ray phase analysis methods. The limits of existence of solid solutions based on low-temperature (α) and high-temperature (γ) CIS modifications and CdSe (β) with chalcopyrite, sphalerite and wurtzite structures, respectively, were established in sub-solidus region at 620 K and 870 K. For certain compositions of solid solutions, the structure was refined using powder X-ray diffraction. A phase diagram of the CIS-CdSe system was constructed. A peritectic process L+β⇔γ takes place in the system at 1260 K. 相似文献
994.
995.
催化不对称Michalel加成反应的新进展 总被引:5,自引:0,他引:5
总结了近年催化不对称Michael加成反应的新方法,包括手性金属络合物催化 的反应,呈手性Lewis酸性的手性金属络合物促进的不对称加成,手性冠醚络合物 催化的反应及其它催化反应。 相似文献
996.
The EPC-synthesis of the cis-hydrindene subunit of the macquarimicins, antibiotics with antitumour and anti-inflammatory activity, has been achieved. Desymmetrization of cis-1,4-cyclopent-2-enediol was succeeded by Diels-Alder reaction and functional group transformations to a tricyclic ketone. Regio- and stereoselective methylation via Claisen condensation and hydrogenation was followed by nucleophilic, intramolecular addition, reduction and acidic fragmentation. Further functional group transformations led to the target molecule. 相似文献
997.
998.
Kratzsch C Peters FT Kraemer T Weber AA Maurer HH 《Journal of mass spectrometry : JMS》2003,38(3):283-295
A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (APCI-LC/MS) is presented for the fast and reliable screening and identification and for the precise and sensitive quantification of 15 neuroleptic (antipsychotic) drugs and three of their relevant metabolites in plasma. It allows confirmation of the diagnosis of a neuroleptic overdose and monitoring of psychiatric patients' compliance. The neuroleptics amisulpride, bromperidol, clozapine, droperidol, flupenthixol, fluphenazine, haloperidol, melperone, olanzapine, perazine, pimozide, risperidone, sulpiride, zotepine and zuclopenthixol and the pharmacologically active metabolites norclozapine, clozapine N-oxide and 9-hydroxyrisperidone were extracted from plasma using solid-phase extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' new LC/MS library, the neuroleptics were quantified in the selected-ion mode. The quantification assay was fully validated. It was found to be selective and proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes. The corresponding reference levels are listed. The accuracy and precision data were within the required limits. The analytes were stable in frozen plasma for at least 1 month. The method was successfully applied to several authentic plasma samples from patients treated or intoxicated with various neuroleptics. The validated LC/MS assay has proved to be appropriate for the isolation, separation, screening, identification and quantification of various neuroleptics in plasma for clinical toxicology and therapeutic drug monitoring purposes. 相似文献
999.
The mechanism for nitrogen activation by molybdenum complexes is a complicated one, involving as it does the coupling of a quartet molybdenum reactant with a singlet nitrogen molecule, passing via a series of quartet and doublet encounter complexes to a triplet intermediate, with the subsequent spin crossing to the singlet surface which then leads via a singlet transition state to the final pair of singlet products. We have investigated in detail a variety of levels of theory to describe the crossing of these electronic surfaces and have calculated both lower-bound and actual minimum energy crossing points for the key spin inversion processes. 相似文献
1000.
P. A. Stuzhin E. A. Pozdysheva O. V. Mal’chugina I. A. Popkova C. Ercolani 《Chemistry of Heterocyclic Compounds》2005,41(2):246-254
AM1 calculations gave the proton affinities of different types of donor sites in tetrakis-3,4-(1,2,5-thiadiazolo)porphyrazine, H2{[SN2)4PA}, and protonation of the meso-nitrogen atoms was found to be favored. A spectrometric study showed that the basicity of the meso-nitrogen atoms of the porphyrazine macrocycle is strongly diminished and these atoms in CF3CO2H are involved in an incomplete acid-base interaction (ABI) to give acid solvates, while a complete ABI (protonation) is found only in the presence of sulfuric acid. The basicity constants of the meso-nitrogen atoms were determined spectrophotometrically in CF3CO2H-H2SO4. The kinetics of decomposition of the macrocyclic chromophore in concentrated sulfuric acid was studied and a possible mechanism for this process was proposed.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 278–287, February, 2005. 相似文献