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991.
992.
François Cheviré Charles F. Baker Olivier Larcher Christophe Colbeau-Justin 《Journal of solid state chemistry》2006,179(10):3184-3190
A new fluorite-type solid solution domain has been evidenced in the system (1−x) CeO2−x/7 Y6WO12□2 using the amorphous citrate route. All the studied phases (0?x?1) crystallize in a cubic-type symmetry. Diffuse reflectance spectra reveal a strong optical absorption between 380 and 400 nm. All substituted compositions spectral selectivities are estimated suitable for application as inorganic UV absorbers. The non linear variation observed in the optical gap values between Y6WO12 and CeO2 is attributed to the presence of the cerium 4f-block band. Additionally, Time Resolved Microwave Conductivity (TRMC) experiment and phenol photodegradation analyses carried out on the Ce0.81Y0.16W0.03O1.95□0.05 (x=0.19) composition do not indicate any photocalatytic activity for this material. 相似文献
993.
994.
We compare Aut(Q), the classical automorphism group of a countable dense linear order, with Aut
c
(Q), the group of all computable automorphisms of such an order. They have a number of similarities, including the facts that every element of each group is a commutator and each group has exactly three nontrivial normal subgroups. However, the standard proofs of these facts in Aut(Q) do not work for Aut
c
(Q). Also, Aut(Q) has three fundamental properties which fail in Aut
c
(Q): it is divisible, every element is a commutator of itself with some other element, and two elements are conjugate if and only if they have isomorphic orbital structures. 相似文献
995.
Scattering functions arise naturally in standard treatments of the effects of a material object or surface embedded in a uniform field. The most commonly used scattering function describes the far-field modulation imparted at large distances to a spherical wavefront eminating from the scatterer. The purpose of this is to develop the properties of the spectrum of scattered plane waves as an exact generalized scattering function. The linearity of the wave equations guarantees that such a representation exists; moreover, it is possible to derive the generalized scattering function from the far-field scattering function by analytic continuation. Although these properties are known, recent theoretical developments have motivated us to reexplore the interrelations among the far-field scattering function, the Green's function and various forms of the generalized scattering function as well as the symmetry properties of the generalized scattering function imposed by reciprocity. For multiple-scattering objects that can be separated by parallel planes, a system of difference equations is developed that fully accommodates the mutual interaction among the scatterers. The mutual interaction equations were developed earlier, but we show here that they can be transformed into the form that would be obtained by using the Foldy-Lax-Twersky formalism. This reinforces the equivalence between wave-space and configuration space formulations of the scattering problems. 相似文献
996.
M.T. Manzari O. Hassan K. Morgan N.P. Weatherill 《Finite Elements in Analysis and Design》1998,30(4):353
An edge-based finite element method is presented for the simulation of compressible turbulent flows on unstructured tetrahedral grids. A two equation k–ω turbulence model is employed and the standard Galerkin approach is used for spatial discretisation. Stabilisation of the resulting procedure is achieved by the addition of an appropriate diffusion. An explicit multistage time-stepping scheme is used to advance the solution in time to steady state. The performance of the algorithm is demonstrated for the simulation of a high Reynolds number transonic separated flow over a wing. 相似文献
997.
For idealized, infinitely thin (“dry”) soap films, an Xis unstable, while for very thick (“wet”) soap films it is minimizing. We show that for soap films of relatively small but
positive wetness, the Xis unstable. Full stability diagrams for the constant liquid fraction case and the constant pressure case are generated. Analogous
questions about other singularities remain controversial. 相似文献
998.
An induced matching of a graph G is a matching having no two edges joined by an edge. An efficient edge dominating set of G is an induced matching M such that every other edge of G is adjacent to some edge in M. We relate maximum induced matchings and efficient edge dominating sets, showing that efficient edge dominating sets are maximum induced matchings, and that maximum induced matchings on regular graphs with efficient edge dominating sets are efficient edge dominating sets. A necessary condition for the existence of efficient edge dominating sets in terms of spectra of graphs is established. We also prove that, for arbitrary fixed p≥3, deciding on the existence of efficient edge dominating sets on p-regular graphs is NP-complete. 相似文献
999.
Nicole R Herring Tori L Schaefer Peter H Tang Matthew R Skelton James P Lucot Gary A Gudelsky Charles V Vorhees Michael T Williams 《BMC neuroscience》2008,9(1):49
Background
Methamphetamine (MA) use is a worldwide problem. Abusers can have cognitive deficits, monoamine reductions, and altered magnetic resonance spectroscopy findings. Animal models have been used to investigate some of these effects, however many of these experiments have not examined the impact of MA on the stress response. For example, numerous studies have demonstrated (+)-MA-induced neurotoxicity and monoamine reductions, however the effects of MA on other markers that may play a role in neurotoxicity or cell energetics such as glucose, corticosterone, and/or creatine have received less attention. In this experiment, the effects of a neurotoxic regimen of (+)-MA (4 doses at 2 h intervals) on brain monoamines, neostriatal GFAP, plasma corticosterone, creatinine, and glucose, and brain and muscle creatine were evaluated 1, 7, 24, and 72 h after the first dose. In order to compare MA's effects with stress, animals were subjected to a forced swim test in a temporal pattern similar to MA administration [i.e., (30 min/session) 4 times at 2 h intervals]. 相似文献1000.
Yurii N. Panchenko Charles W. Bock Joseph D. Larkin Alexander V. Abramenkov 《Structural chemistry》2008,19(5):793-799
In connection with the appearance of new experimental vibrational data on the high-energy rotational isomer of 2,3-dimethylbuta-1,3-diene
(I) in a low-temperature matrix and in neat crystals, the ab initio-based vibrational analysis of this molecule has been re-evaluated.
Calculated wavenumbers derived from a scaled quantum-mechanical force field analysis at the MP2(FC)/aug-cc-pVDZ//MP2(FC)/aug-cc-pVDZ
computational level are compared with experimental data. Several reassignments of the fundamental wavenumbers for I have been suggested in the course of the current analysis, and the existence of a high-energy non-planar s-gauche conformer of 2,3-dimethylbuta-1,3-diene has been confirmed. 相似文献