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排序方式: 共有138条查询结果,搜索用时 15 毫秒
31.
Avraham A. Melkman 《Journal of Approximation Theory》1996,84(3):265-273
We provide a different proof for Morken's result on necessary and sufficient conditions for a minor of the discrete B-spline collocation matrix to be positive and supply intuition for those conditions. 相似文献
32.
Decaprenylphosphoryl β-d-arabinofuranose (DPA) is a key arabinose donor in mycobacteria. In an effort to establish a practical synthetic scheme for DPA, the synthesis of nerylphosphoryl and farnesylphosphoryl β-d-arabinofuranoses has been developed. The products were obtained by coupling of a suitably protected β-d-arabinofuranosyl phosphate intermediate with activated forms of the C10 nerol and C15trans,trans-farnesol and subsequent deprotection. 相似文献
33.
Let G be a reductive group scheme of type A acting on a spherical scheme X. We prove that there exists a number C such that the multiplicity is bounded by C, for any finite field F and any irreducible representation ρ of . We give an explicit bound for C. We conjecture that this result is true for any reductive group scheme and when F ranges (in addition) over all local fields of characteristic 0.Different aspects of this conjecture were studied in [3], [11], [6], [7]. 相似文献
34.
Avraham?AizenbudEmail author Dmitry?Gourevitch Siddhartha?Sahi 《Israel Journal of Mathematics》2015,206(1):39-88
The notion of derivatives for smooth representations of GL(n, ? p ) was defined in [BZ77]. In the archimedean case, an analog of the highest derivative was defined for irreducible unitary representations in [Sah89] and called the “adduced” representation. In [AGS] derivatives of all orders were defined for smooth admissible Fréchet representations (of moderate growth).A key ingredient of this definition is the functor of twisted coinvariants with respect to the nilradical of the mirabolic subgroup. In this paper we prove exactness of this functor and compute it on a certain class of representations. This implies exactness of the highest derivative functor, and allows to compute highest derivatives of all monomial representations.In [AGS] these results are applied to finish the computation of adduced representations for all irreducible unitary representations and to prove uniqueness of degenerate Whittaker models for unitary representations. 相似文献
35.
Determination of volatile biogenic amines in muscle food products by ion mobility spectrometry 总被引:2,自引:0,他引:2
The extent of spoilage of muscle food products was determined through measurement of volatile biogenic amines that emanated from food samples. The release of the amines was enhanced by addition of a few drops of an alkaline solution and the amines were monitored by ion mobility spectrometry (IMS). The limit of detection of the method for trimethylamine (TMA) was 2 ng and the measurement was completed within <2 min with short and long term reproducibility of 15 and 25%, respectively, for replicate samples. The method provides qualitative information as it distinguishes between different amines, as well as quantitative data for the key compounds. A good correlation was found between the IMS results and the microorganism populations in microbiological cultures. The effects of storage time and temperature and of the type of meat on the formation of biogenic amines were examined, and as expected, the higher the storage temperature the faster the spoilage. Thus, this pilot study shows that the measurement of biogenic amines can serve as an indicator for food spoilage or freshness. 相似文献
36.
Lior C. Goldenberg Ian Hutcheon Norman Wardlaw Avraham J. Melloul 《Transport in Porous Media》1993,13(3):221-237
The rearrangement of matrix configuration due to the redistribution of clay particles was studied by introducing different suspensions into porous media. Clay (kaolinite) with low CEC (cation exchange capacity) and small flocs of high CEC clay (smectite) accumulated in regions of slow flow. In some experiments this was followed by rapid accumulation in regions of high velocity, impairing flow to a considerable degree. Clay with high CEC formed more voluminous structures which could bridge over a passage and impair the flow.In either case, whether small or large units of clay are involved, the final flow occurred mainly through open, preferred pathways. Such processes of redistribution and appearance of flow pathways may occur in subsurface porous media aquifers where forced gradients exist (e.g. in aquifers near the perforation of pumping wells and in places where large quantity of water are naturally or artificially recharged and in producing gas and oil fields). 相似文献
37.
Many analytical instruments (e.g., videofluorimeter and liquid chromatographs with spectrometric detectors) can produce two-dimensional data arrays. Rank-annihilation factor analysis enables chemical composition to be quantified from such an array. Solution by this method requires a search for a minimum value of an eigenvector which cannot be calculated even iteratively. The problem is presented here as a generalized eigenvalue problem and a direct solution is found by using singular value decomposition. 相似文献
38.
39.
Beidenkopf H Avraham N Myasoedov Y Shtrikman H Zeldov E Rosenstein B Brandt EH Tamegai T 《Physical review letters》2005,95(25):257004
The thermodynamic phase diagram of Bi2Sr2CaCu2O8 was mapped by measuring local equilibrium magnetization M(H,T) in the presence of vortex shaking. Two equally sharp first-order magnetization steps are revealed in a single temperature sweep, manifesting a liquid-solid-liquid sequence. In addition, a second-order glass transition line is revealed by a sharp break in the equilibrium M(T) slope. The first- and second-order lines intersect at intermediate temperatures, suggesting the existence of four phases: Bragg glass and vortex crystal at low fields, glass and liquid at higher fields. 相似文献
40.
Feintuch A Alexandrowicz G Tashma T Boasson Y Grayevsky A Kaplan N 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,142(2):382-385
Three-dimensional pulsed ESR imaging was performed on a (FA)(2)PF(6) crystal using a three-dimensional Fourier imaging sequence. The best resolution achieved was of 20 microm(3). Comparison with images obtained using the filtered back-projection method shows the superiority of this method under the given conditions. 相似文献