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981.
Studies on Oxide Catalysts. XVI. Composition and Structure of Doped Zinc Oxide Catalysts Analytical, x-ray, textural, IR-spectroscopic, and MÖSSBAUER investigations of zinc oxide catalysts doped with Li2O, Ga2O3 and Fe2O3 were conducted in order to reveal relations between electronic and catalytic properties. The mixtures ZnO/Li2CO3, ZnO/Ga2O3, ZnO/Fe2O3, and ZnO/57Fe(NO3)3, after the thermal pretreatment, always exist in the state of a polyphase solid system. In the ZnO/Li2O system, only a very small part of the added lithium oxide is incorporated into the zinc oxide lattice by substitution. A second part of the Li2O volatizes during the thermal pretreatment, and the greater part of it exists in the state of a separate solid phase in the catalyst and can be washed out by water. During the pretreatment, according to its temperature and duration, two-phase systems (ZnO, ZnMe2O4) or three-phase systems (ZnO, ZnMe2O4, Me2O3) are formed in the solid systems ZnO/Ga2O3 and ZnO/Fe2O3. For the reaction of both oxides forming a spinel, an electronic model is proposed. 相似文献
982.
H. Bremer J. Körnig W. Reschetilowski F. Vogt K. -P. Wendlandt 《Reaction Kinetics and Catalysis Letters》1980,13(3):209-215
Isomerization of n-hexane over Pt/NH4NaY follows the reaction scheme k1, k2, kc linearly increase with increasing ammonia exchange degree in the zeolite and no significant changes in selectivity occur. During activation Al is partially removed from the lattice framework with the formation of HAlNaY.
- Pt/NH4NaY . k1, k2 kc , . Al HAlNaY.相似文献
983.
Quaternary System ZnSe - Cr2Se3 - In2Se3 The section Zn1-xIn0.667xCr2Se4 and ZnCr2-yInySe4 as well as some samples of compositions outside these joins of the quaternary system ZnSe Cr2Se3 - In2Se3 were studied with the help of X-ray Guinier photographs of quenched samples. Whereas no detectable amounts of chromium can be incorporated into ZnIn2Se4 of the thiogallate structure (MnIn2Te4 type) in the case of the spinel ZnCr2Se4 (a = 1050.0 pm) up to 21 mol % of chromium and up to 20 mol % of zinc can be substituted by indium. However, spinel type solid solutions with larger indium content (up to a = 1076 pm) are formed by coincident substitution of both zinc and chromium corresponding to Zn1-xIn0.667xCr2-yInySe4 (0 < x + y < 0.6) with indium in both tetrahedral and octahedral lattice sites. 相似文献
984.
985.
986.
Natalja S. Rodionova Emilia Rota Aleksandra S. Tsarkova Valentin N. Petushkov 《Photochemistry and photobiology》2017,93(2):416-428
Even though bioluminescent oligochaetes rarely catch people's eyes due to their secretive lifestyle, glowing earthworms sighting reports have come from different areas on all continents except Antarctica. A major breakthrough in the research of earthworm bioluminescence occurred in the 1960s with the studies of the North American Diplocardia longa. Comparative studies conducted on 13 earthworm species belonging to six genera showed that N‐isovaleryl‐3‐aminopropanal (Diplocardia luciferin) is the common substrate for bioluminescence in all examined species, while luciferases appeared to be responsible for the color of bioluminescence. The second momentous change in the situation has occurred with the discovery in Siberia (Russia) of two unknown luminous enchytraeids. The two bioluminescent systems belong to different types, have different spectral characteristics and localization, and different temperature and pH optima. They are unique, and this fact is confirmed by the negative results of all possible cross‐reactions. The bioluminescent system of Henlea sp. comprises four essential components: luciferase, luciferin, oxygen and calcium ion. For Friderica heliota, the luminescent reaction requires five components: luciferase, luciferin, ATP, magnesium ion and oxygen. Along with luciferin, more than a dozen analogues were isolated from worm biomass. These novel peptide‐like natural compounds represent an unprecedented chemistry found in terrestrial organisms. 相似文献
987.
Frederik Rummel Frerk Wehmeyer Dr. Matthias Vogt Prof. Dr. Robert Langer 《欧洲无机化学杂志》2023,26(28):e202300313
The thioether-group-containing SNS-type pincer complex [({EtSCH2CH2}2NH)RuCl(H)(PPh3)] ( 2 ) exists in three different diastereomers ( 2 a – c ). The molecular structures obtained from single crystal X-Ray diffraction studies of all three isomers reveal a difference in the relative orientation of the respective EtS-groups, while other commonly observed diastereomers as the result of cis-/trans- or fac-/mer-isomerism are not observed. Chemical exchange between the three diastereomers 2 a – c was discovered by phase-sensitive 1H and 31P NOESY NMR spectroscopy, and further quantified by line shape analysis of 1H NMR spectra. The experimentally derived averaged Gibbs energies of activation for the interconversion of the isomers (65–70 kJ/mol) are in good agreement with the results obtained from DFT calculations, which suggest an inversion of the ligating sulfur atoms, although a dissociative pathway for the configurational inversion can be competitive. 相似文献
988.
989.
C. Ascheron R. Flagmeyer G. Otto J. Vogt H. U. Frey 《Crystal Research and Technology》1987,22(12):1497-1503
On GaP single crystals bombarded with 0.3 MeV and 1.0 MeV protons the fluence and depth dependences of radiation damage are studied by means of particle induced X-ray emission spectrometry under chaneling conditions (PIXE-C) and the Rutherford backscattering/channeling technique (RBS-C). It is demonstrated that PIXE-C is suitable to study depth profiles of damage density by the combination with the bevelling technique. 相似文献
990.
Well‐established, linear multivariate calibration methods such as multivariate least‐squares regression (MLR), principal component regression (PCR), or partial least squares (PLS) have two limitations: (i) measured data must be linearly related to the response variables and (ii) predictor variables xn = 1, …, N cannot be coupled to each other. For evaluation of nonlinear data, however, these restrictions need to be overcome and thus polynomial multivariate least‐squares regression (PMLR or “response surfaces”) has been introduced here. PMLR is based on multivariate least squares but incorporates all combinations of predictor variables up to a user‐selected polynomial order (e.g., including u or v = 0). Because of the inclusion of such coupled terms and their powers, PMLR models are better adapted to model nonlinear data and can help to enhance the prediction step's accuracy and precision. PMLR has been based on MLR because it facilitates—unlike PCR or PLS—a physical and chemical interpretation of the predictors. Hence, the origins and the relevance of nonlinear and/or coupled predictors can be investigated. The details of the PMLR algorithm and its implementation are presented along with a method for model optimization utilizing gradients of response surfaces. Newly developed PMLR models up to quintic order have been applied to predict a chromatograph's peak resolution as a function of six‐instrument parameters. It has been demonstrated that PMLR is better capable than MLR and PCR to describe these nonlinear and coupled instrument parameters. In addition, the novel software tool has been utilized for model optimization to determine instrument parameters, which result in the best chromatographic resolution. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献