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101.
Synthesis and Crystal Structure of a Novel Hexagonal Modification of Al2S3 with Five-coordinated Aluminum A new hexagonal high temperature modification of Al2S3 could be prepared by chemical vapour transport with iodine (860 → 750°C) or by annealing of α -Al2S3 at 550°C. According to the single crystal X-ray structure determination the novel form of Al2S3 crystallizes in space group P 61 (No. 169) with a = 6.491(1), c = 17.169(4) Å, V = 626.5 Å3, Z = 6; R = 0.0253. In this modification one half of the aluminum atoms are tetrahedrally coordinated [d(Al? S): 2.226–2.267 Å], whereas the other half are in trigonal bipyramidal coordination of five S atoms with bond lengths of 2.272–2.315 Å (equatorial) and 2.495–2.521 Å (axial). Aluminum in AlS5 coordination is observed for the first time in this compound. The crystal structure is isotypic to In2Se3 and AlInS3. In addition, results of a refinement of the α -Al2S3 crystal structure are reported which were obtained on crystals prepared also by chemical vapour transport with iodine. 相似文献
102.
103.
Fundamental understanding of aerosol formation and particle transport are important aspects of understanding and improving
laser-ablation ICP–MS. To obtain more information about particles entering the ICP, laser aerosols generated under different
ablation conditions were collected on membrane filters. The particles and agglomerates were then visualised using scanning
electron microscope (SEM) imaging. To determine variations between different sample matrices, opaque (USGS BCR-2G) and transparent
(NIST SRM 610) glass, CaF2, and brass (MBH B26) samples were ablated using two different laser wavelengths, 193 and 266 nm. This study showed that the
condensed nano-particles (∼10 nm in diameter) formed by laser ablation reach the ICP as micron-sized agglomerates; this is
apparent from filters which contain only a few well-separated particles and particle agglomerates. Ablation experiments on
different metals and non-metals show that the structure of the agglomerates is matrix-dependent. Laser aerosols generated
from silicates and metals form linear agglomerates whereas particle-agglomerates of ablated CaF2 have cotton-like structures. Amongst other conditions, this study shows that the absorption characteristics of the sample
and the laser wavelength determine the production of micron-sized spherical particles formed by liquid droplet ejection. 相似文献
104.
S. Nagadome H. Oda Y. Hirata H. Igimi A. Yamauchi Y. Sasaki G. Sugihara 《Colloid and polymer science》1995,273(7):701-707
In order to study how the bile salts and lipids behave in the vicinity of microvillus, the transport properties of a sodium salt of deoxycholic acid (NaDC) and its mixture with monooleoylglycerol (MO) through artificial membranes were investigated in 0.15 M NaCl saline solution at 37°C.The hydrodynamic radius of MO-solubilized micelles was estimated to be approximately 17–20 Å from the transport study. The thermodynamically stable MO-NaDC mixed micelles formed above critical micelle concentration in the higher region of mole fraction of NaDC in the mixture (X
NaDC>ca. 0.6), can behave as a single species in transport process and freely pass through the porous membranes of both pore sizes, 0.01 m and 0.1 m.The permeabilities of MO-NaDC mixed micelles are large compared with those of pure NaDC micelles. MO molecules solubilized may probably enhance the interaction between MO and NaDC molecules by better contacting with the respective hydrophobic groups in a mixed micelle (the flexible structure of MO molecule enables it), and in this situation, the smaller micelles compared with those of pure NaDC must be more favorable. 相似文献
105.
D. Beigie 《Journal of Nonlinear Science》1995,5(1):57-103
Summary We study separatrix crossing in near-integrablek-degree-of-freedom Hamiltonian flows, 2 <k < , whose unperturbed phase portraits contain separatrices inn degrees of freedom, 1 <n <k. Each of the unperturbed separatrices can be recast as a codimension-one separatrix in the 2k-dimensional phase space, and the collection of these separatrices takes on a variety of geometrical possibilities in the reduced representation of a Poincaré section on the energy surface. In general 0 l n of the separatrices will be available to the Poincaré section, and each separatrix may be completely isolated from all other separatrices or intersect transversely with one or more of the other available separatrices. For completely isolated separatrices, transitions across broken separatrices are described for each separatrix by the single-separatrix crossing theory of Wiggins, as modified by Beigie. For intersecting separatrices, a possible violation of a normal hyperbolicity condition complicates the analysis by preventing the use of a persistence and smoothness theory for compact normally hyperbolic invariant manifolds and their local stable and unstable manifolds. For certain classes of multi-degree-of-freedom flows, however, a local persistence and smoothness result is straightforward, and we study the global implications of such a local result. In particular, we find codimension-one partial barriers and turnstile boundaries associated with each partially destroyed separatrix. From the collection of partial barriers and turnstiles follows a rich phase space partitioning and transport formalism to describe the dynamics amongst the various degrees of freedom. A generalization of Wiggins' higher-dimensional Melnikov theory to codimension-one surfaces in the multi-separatrix case allows one to uncover invariant manifold geometry. In the context of this perturbative analysis and detailed numerical computations, we study invariant manifold geometry, phase space partitioning, and phase space transport, with particular attention payed to the role of a vanishing frequency in the limit approaching the intersection of the partially destroyed separatrices. The class of flows under consideration includes flows of basic physical relevance, such as those describing scattering phenomena. The analysis is illustrated in the context of a detailed study of a 3-degree-of-freedom scattering problem. 相似文献
106.
On the Chemical Transport and Sublimation of CrBr3 — Experiments and Model Calculations The migration of CrBr3 in the presence of high concentrations of bromine (for example D(Br2) = 0,05 mmol/ml; closed silica ampoules) in the investigated temperature range (T? = 625°C to 875°C; T? = 50°C) is a result from the endothermic reaction The chemical transport of CrBr3 is superimposed with the sublimation. With low concentrations of D(Br2) and high temperatures T? is the sublimation decisive participated. This is a result of the homogenous equilibrium between CrBr3,g and CrBr4,g (2a) The reaction (2a) in comparison with the chemical transport of CrCl3 with Cl2 (Gl. (2b)) is more shifted to CrBr3,g. 相似文献
107.
The transport coefficients for the nine point groups
—which represent the symmetry groups of the quasicrystals in two and three dimensions—have been evaluated and tabulated in
this work, employing group-theoretical methods. 相似文献
108.
L. Fionova O. Konokenko V. Matveev L. Priester S. Lartigue F. Dupau 《Interface Science》1994,1(3):207-211
Data on mutual arrangements of different types of grain boundaries in polycrystals are presented. The heterogeneity in grain boundary distribution, namely, the effect of gathering low-angle or special tilt grain boundaries is found in pure aluminum thin films, in sheets of Fe-3% Si alloy and in Al2O3 doped with MgO or MgO and Y
2O3. The local texture, i.e., formation of colonies or clusters of close-oriented grains is considered as a reason of this heterogeneity. The influences of grain boundary gathering on the transport properties of polycrystals and on the crack propagation are discussed. A new concept of effective grain size is suggested to analyze the relationship between material microstructures and material properties. 相似文献
109.
In this paper the thermal energy diffusion for quantum particles is described. The quantum heat transport equation is obtained. It is shown that, for a short-time thermal excitation (of the order of the relaxation time), the excited matter response is quantized on the different levels (atomic, nuclear, quark) with quantum thermal energy equalE
atomic 9 eV,E
nuclear 7 MeV, andE
quark 139 MeV. 相似文献
110.
An energy-transport model is rigorously derived from the Boltzmann transport equation of semiconductors under the hypothesis that the energy gain or loss of the electrons by the phonon collisions is weak. Retaining at leading order electron-electron collisions and elastic collisions (i.e., impurity scattering and the elastic part of phonon collisions), a rigorous diffusion limit of the Boltzmann equation can be carried over, which leads to a set of diffusion equations for the electron density and temperature. The derivation is given in both the degenerate and nondegenerate cases. 相似文献