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81.
We report the first six-dimensional quantum dynamical study of the dissociative adsorption of H(2) on a (110) surface. We have performed quantum coupled-channel calculations for the system H(2)/Pd(110) based on a potential energy surface (PES) that was derived from ab initio electronic structure calculations. In particular, we have focused on the effects of the corrugation and anisotropy of the PES on the H(2) dissociation probability. Our results agree well with the available experimental data for the sticking probability as a function of the initial kinetic energy and the angle of incidence. Because of the coupling between the anisotropy and corrugation of the potential energy surface our calculations predict an unusual rotational heating and a rather small rotational alignment in desorption. 相似文献
82.
Oxide ceramic masses react to simple shearing with hardening (peptisation: increase in the shear stress with the shear deformation).
In the present study the correlation between the increase in the shear stress and the porosity, agglomeration processes and
the type of flow are analysed. For this purpose oxide ceramic masses are tested in a shear device especially developed for
pastes and analysed by rheometric experiments, NMR methods and particle size analysis. The results support the hypothesis
that structural changes (hardening, increase in the mean porosity) of the material during the peptisation mainly depend on
the magnitude and not on the kind of the energy input and thus of the type of flow. The fraction of bound (more generally,
the immobilised) water increases with the shear displacement. Also crushing of primary particles could be observed. Both the
crushing of solid particles causing an increased solid surface and the formation of a three-dimensional gel structure are
microscopic effects capable of resulting in the binding or retaining water. On a macroscopic scale these phenomena cause hardening.
Magnetic resonance imaging visualises flow-induced agglomerates, which form owing to the shear flow and increase the porosity
averaged over the whole sample. After the shear experiment rolls of paste can be seen which indicate that the general assumption
of a plane shear flow in the shear device is not warrantable.
Received: 19 July 2001 Accepted: 25 October 2001 相似文献
83.
Joachim Meissner 《Polymer Testing》1983,3(4):291-301
Laser Doppler velocimetry (LDV) is a new tool for fluid dynamics studies. Using LDV the velocity vector field can be measured without disturbing the flow itself. However, in polymer melt fluid dynamics difficulties arise because of temperature problems, the relatively high pressure involved, and the often extremely slow flows. In this paper a LDV system is described which was set up especially for polymer melt flow investigations. 相似文献
84.
Abstract— Photofrin II (PF-II) is the commercial name of the active photosensitizer which is used in photodynamic therapy of cancer. The effect of the composition of lipid membranes on the binding of PF-II was studied and compared to hematoporphyrin derivative (Hpd), which is a complex mixture of porphyrins and from which PF-II is separated. We find that increasing the content of cholesterol in the bilayer decreases the partitioning of PF-II into the bilayer, similar to what we have found earlier with Hpd. However, inserting DMPC or DPPC into the membrane, which was shown to decrease the binding of Hpd, causes the opposite trend with PF-H. A membrane fluidizer such as benzyl alcohol also has different effects on the membrane binding of Hpd and PF-II. The rate of binding of PF-II to a lipid membrane is about 10 times lower than that of Hpd. These results as well as I- quenching of the fluorescence of the two porphyrins indicate that PF-II is immersed less homogeneously and deeper in the bilayer than Hpd. The unique additive-dependent binding of PF-II to lipid membranes calls for care in using Hpd as a model photosensitizer. 相似文献
85.
A simple semiconductor gas sensor (TGS 812) is used for the on-line measurement and control of indole during the production of l-tryptophan from indole and l-serine with immobilized E. coli cells. Indole is estimated in the reactor gas space. In combination with an automatic indole supply system, a feed-batch process became possible. The indole concentration was monitored and kept within the optimal range (300–600 mg l?1). A simple gas-sensing electrode dipped in the reaction medium provides direct measurement of organic solvents and gases in the liquid. Such a system is suitable for on-line determination of ethanol (10–70 g l?1) during continuous production of ethanol with immobilized yeast cells. 相似文献
86.
Joachim Franzke Maria-Antoaneta Bratescu Damir Veza Kay Niemax 《Mikrochimica acta》1994,113(3-6):349-355
Laser impedance spectroscopy in a miniature neon RF-discharge operating at 0.27 bar was performed. The dominant role of the metastable atoms to the size and the sign of the RF-signal was investigated. Excellent linearity of the RF-signal but poor detection sensitivity of excited metastable neon atoms were found at low laser powers. 相似文献
87.
Gintaras Pivoriunas Ccilia Maichle‐Mssmer Simon Schwarz Joachim Strhle 《无机化学与普通化学杂志》2005,631(10):1743-1745
Synthesis and Crystal Structure of [(Ph3PAu)3NPPh3][PF6]2, a Gold(I) Phosphoraneiminato Complex The photolytic reaction of Ph3PAuN3 with Cr(CO)6 in THF yields the phosphoraneiminato complex [(Ph3PAu)3NPPh3]2+ in low yield as well as the cluster cation [(Ph3PAu)8]2+ as the main product. The phosphoraneiminato complex crystallizes from CH2Cl2 with [PF6]? ions as [(Ph3PAu)3NPPh3][PF6]2·CH2Cl2 in the triclinic space group with a = 1200.8(1), b = 1495.6(2), 2053.5(5), α = 86.97(2)°, β = 82.79(1)°, γ = 81.87(2)°, and Z = 2. The phosphoraneiminato ligand bridges through its N atom three Au atoms, which itself are connected to each other by weak aurophilic interactions. 相似文献
88.
Helmut Ehrenberg Hermann Pauly Joachim Gröbner 《Journal of solid state chemistry》2004,177(1):227-230
The cubic face-centered structure of LiAl (, at ) transforms into a tetragonal body-centered structure (I41/amd, , at ). This first-order phase transition at about during heating is probably the reason for the so-called “ anomalies” in some physical properties like specific heat, electrical resistivity and nuclear-spin lattice relaxation. This transition seems to be correlated with the composition Li:Al of the alloy and the amount of Li vacancies. 相似文献
89.
90.
Binuclear Nickel(0) Complexes with “Snake Ligands” of 1-Azadiene Type: Model Systems of the Oxidative Coupling of 1-Azadienes and 1.3-Dienes at Nickel(0) Synthesis, properties, and reactions of dimeric nickel(0) complexes with special 1-azadiene typ ligands (“snake ligands”) are described. The X-ray analysis of a typical compound (Bis-(bis-cinnamaldehyde-N,N'-propylendiimine)-dinickel(0)) shows that both central atoms have the coordination number 3. The four 1-azadiene groups are coordinated in a different way: unidendate coordination by N-Ni(1) bond and bidendate coordination by N-Ni(1) and olefine-Ni(2) bond. The compound is a good model system for the oxidative coupling reaction of 1-azadienes with 1.3-dienes at 2 nickel(0) centres. IR and electronic spectra show other complexes with this type of ligands to have an analogous coordination sphere. 相似文献