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排序方式: 共有10000条查询结果,搜索用时 445 毫秒
931.
Klaus Müllen Siglinde Bender Eleni Kotzamani Hans Schmickler Bruno Frei Hans R. Wolf 《Tetrahedron letters》1981,22(36):3513-3516
The conformational mobility of a series of conjugated dienones is investigated by low-temperature NMR- and IR-spectroscopy and interpreted in terms of substituent effects. 相似文献
932.
Danielle Giron S. Monnier M. Mutz P. Piechon T. Buser F. Stowasser K. Schulze M. Bellus 《Journal of Thermal Analysis and Calorimetry》2007,89(3):729-743
Adequate very sensitive quantification methods are needed for the development and are also now required for the monitoring
of undesirable solid form(s) as routine tests. The pre-requisite for quantitation are selectivity, sensitivity and most important
the purity of standards and their proper storage, what is a challenge for metastable forms.
Several analytical techniques are available such as X-ray diffraction, spectroscopy, thermal analysis and microcalorimetry.
The different steps of the validation of the analytical methods and problems to be solved are discussed. Examples illustrate
the different techniques and compare their possible advantages and limits. The relative standard deviation of measurements
should allow for checking the homogenization procedure of mixtures for calibration. The validation should be carried out following
ICH guidelines for validation of analytical methods. Comparison of different techniques in adequate concentration range add
confidence in the analytical results. 相似文献
933.
Giuseppe Bruno Santo Lanza Francesco Nicol Giuseppe Tresoldi Giuseppe Rosace 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(5):m316-m318
The title compound, [PdPtCl(C3H5)(C6H10N2S2)(C17H14NP)]·CHCl3, was obtained by deprotonation of the initial platinum(II) complex of the dithioxamide and subsequent reaction with [Pd(η3‐C3H5)(μ‐Cl)]2. Both metal atoms exhibit a square‐planar coordination geometry, with the two planes forming a dihedral angle of 21.7 (2)°. The dithioxamide bis‐chelating bridge is flat. 相似文献
934.
Andrzej Czerwiński Iwona Kiersztyn Michał Grdeń 《Journal of Solid State Electrochemistry》2003,7(6):321-326
The effect of temperature on hydrogen and deuterium electrosorption into a palladium LVE (limited-volume electrode) has been
investigated. A decrease in hydrogen capacity (H/Pd ratio) with increasing temperature has been observed. Temperature strongly
influences the plots of measured H(D)/Pd values vs. potential scan rate. In addition, hydrogen absorption was found to be
dependent on the composition of the surrounding electrolyte solution. These results have confirmed the hypothesis that two
different mechanisms of hydrogen desorption from the palladium electrode take place, namely electrochemical oxidation and
non-electrochemical recombination. Further, the ratio between the rate constants for these two processes has been found to
change with temperature.
Electronic Publication 相似文献
935.
Petra Spitzer Bruno Rossi Yves Gaignet Stéphane Mabic Uwe Sudmeier 《Accreditation and quality assurance》2005,10(3):78-81
There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 S cm–1 at 25.0 °C, resistivity >1 M cm at 25.0 °C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.Milipore, Milli-Q and Elix are registered trademarks of Millipore Corporation. 相似文献
936.
Summary The thermal behavior of KH2PO4, NaH2PO4 and Na2HPO4 under non-isothermal conditions using TG method with different heating rates was studied. The values of the reaction rate were processed by means of Friedmans differential-isoconversional method. A dependence of the activation energy vs. conversion was observed. Therefore a procedure based on the compensation effect (suggested by Budrugeac and Segal) was applied. A less speculative data processing protocol was offered by the non-parametric kinetics method suggested by Serra, Nomen and Sempere. Three steps were observed by non-isothermal heating: a dehydration, a dimerization and a polycondensation. The differences in the intimate reaction mechanism are determined by the initial number of water molecules. 相似文献
937.
Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal desorption spectroscopy(TDS)results demonstrate that adsorption of molecular hy- drogen on Pt(111)forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species.Bulk Had species is more thermal-unstable than surface Had species on Pt(111),suggesting that bulk Had species is more energetic.This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions. 相似文献
938.
On the mechanism of nanopore filling of SAPO-5 molecular sieve by nitrogen molecules 总被引:1,自引:0,他引:1
Boddenberg B Radha Rani V Grosse R 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):10962-10969
SAPO-5 molecular sieve was synthesized according to patent literature and characterized with X-ray diffraction, electron microscopy (SEM, TEM), and solid state magic angle spinning NMR spectroscopy. The material of particles in the micrometer region was found to consist of ca. 20 nm microcrystallites packed in mostly parallel orientation to ca. 200 nm sized agglomerates. The nitrogen adsorption isotherm was measured at 77.6 K over ca. 7 decades of pressure up to pore saturation. The course of the isotherm is interpreted to consist of filling of the nanopores (diameter, 0.73 nm) up to 2N(2)/unit cell, subsequent multilayer adsorption on the outer surface of the agglomerates, and, finally, pore condensation in the interparticle adsorption space. The nanopore adsorption can be quantitatively reproduced with the statistical mechanical model of a quasi one-dimensional lattice gas taking intermolecular interactions into account. The evaluated energy parameters are of physically reasonable magnitude and agree with literature data. The multilayer part of the adsorption isotherm can be well represented by the Brunauer-Emmett-Teller model yielding a specific outer space area (63 m(2) g(-)(1)) which is consistent with estimated geometrical and pore size analysis data. 相似文献
939.
Ahmad Shaabani Abbas Rahmati Soheila Naderi 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):553-557
Summary. Reaction of triphenylphosphine and an electron deficient acetylenic ester in the presence of strong N–H acid such as alkyl
and aryl sulfamides or acetamide produces phosphorous ylides at room temperature in CH2Cl2. The aryl sulfamide phosphoranes undergo a smooth transformation reaction in boiling toluene and produce iminophosphoranes. 相似文献
940.
Crown ethers were reacted with HN-proton-donor molecules to obtain crystalline molecular host-guest complexes. It was found that complexes with crown ethers of different structure are formed, depending on the linear dimensions and mode of steric shielding of active centers of the proton-donor molecules.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 2030–2033.Original Russian Text Copyright © 2004 by Wang, Ganin.This revised version was published online in April 2005 with a corrected cover date. 相似文献