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41.
42.
Fe2O3--V2O5 catalysts doped with Cs2SO4 (molar ratio: V:Fe:Cs=1:0.74:0.06) were found to be a rather inhomogeneous mixture of various crystalline and amorphous iron
vanadate phases. After calcination in air the catalyst was divided into three different parts which were analyzed separately
revealing the formation of FeVO4 in the top and bottom fraction of the crucible and Fe2V4O13 in the middle fraction. As compared to the well crystallized FeVO4 reference sample, the quadrupole splittings of FeVO4 in the Cs-doped catalysts were larger pointing to more distorted iron sites which were assumed to be responsible for high
catalytic selectivities. In contrast, the quadrupole splittings of FeVO4 in the less selective K- and Rb-doped Fe2O3--V2O5 catalysts were smaller. Additional components in the bottom fraction were also α-Fe2O3 and Fe1-xS. As indicated by the CEMS spectra the latter is located preferentially on the surface of the catalyst particles.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
43.
G. Dlubek R. Krause O. Brümmer J. Tittes 《Applied Physics A: Materials Science & Processing》1987,42(2):125-127
Positron-lifetime measurements have been used to study the annealing of vacancies in neutron-irradiated GaAs. The vacancies which are interpreted as defects in the Ga sublattice disappear in a single annealing stage (at 500°C in GaAs doped with Si or Zn, and at 600°C in Cr-doped GaAs). 相似文献
44.
The flat rank of a totally disconnected locally compact group G, denoted flat-rk(G), is an invariant of the topological group
structure of G. It is defined thanks to a natural distance on the space of compact open subgroups of G. For a topological
Kac-Moody group G with Weyl group W, we derive the inequalities alg-rk(W) ≤ flat-rk(G) ≤ rk(|W|0). Here, alg-rk(W) is the maximal Z-rank of abelian subgroups of W, and rk(|W|0) is the maximal dimension of isometrically embedded flats in the CAT0-realization |W|0. We can prove these inequalities under weaker assumptions. We also show that for any integer n ≥ 1 there is a simple, compactly
generated, locally compact, totally disconnected group G, with flat-rk(G) = n and which is not linear. 相似文献
45.
In a previous paper we considered an extension of the hard hexagon model to a solvable two-dimensional lattice gas with at most two particles per pair of adjacent sites. Here we use various mathematical identities (in particular Gordon's generalization of the Rogers-Ramanujan relations) to express the local densities in terms of elliptic functions. The critical behavior is then readily obtained.Supported in part by the National Science Foundation Grant MCS 8201733. 相似文献
46.
George R. T. Hendry 《Journal of Graph Theory》1989,13(2):245-248
The Ramsey numbers r(F1, F2) are tabulated for essentially all but six pairs of graphs F1 and F2 with five vertices. 相似文献
47.
48.
The ability to quantitatively map the distribution of elements on the micrometer scale and smaller with high sensitivity and isotopic discrimination is unique to ion microscopy. The information contained in ion images can be crucial to the study of the solid state, where chemical heterogeneity is often directly related to observed behavior. The tools of digital image processing allow the extraction of quantitative information from the image data. These techniques coupled with improved instrumentation for the detection of ion images drastically increase the problem solving capabilities of the ion microscope. The use of such methods and instrumentation in the ion microscopic analyses of cell cultures and tissues of biological and biomedical relevance will be discussed. 相似文献
49.
50.
Symmetric Hilbert spaces such as the bosonic and the fermionic Fock spaces over some lsquo;one particle space’ are formed by certain symmetrization procedures performed on the full Fock space. We investigate alternative ways of symmetrization
by building on Joyal's notion of a combinatorial species. Any such species F gives rise to an endofunctor of the category of Hilbert spaces with contractions mapping a Hilbert space to a symmetric Hilbert space with the same symmetry as the species F. A general framework for annihilation and creation operators on these spaces is developed, and compared to the generalised
Brownian motions of R. Speicher and M. Bożejko. As a corollary we find that the commutation relation with admits a realization on a symmetric Hilbert space whenever f has a power series with infinite radius of convergence and positive coefficients.
Received: 7 April 2000; in final form: 28 November 2000 / Published online: 19 October 2001 相似文献