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971.
It is wellknown that the technique of character sums together with the tools of algebraic number theory is the adequate method for the study of difference sets in abelian groups, compare for instance Ott [5] or Turyn [6]. In this paper we use this method to prove a new non-existence theorem for certain difference sets in abelian groups of order rpa rp^a , where r 1 2 r \neq 2 and p are distinct primes. 相似文献
972.
973.
974.
Andrei N. Yakunin 《Central European Journal of Physics》2004,2(3):535-555
A cubic structure of polymer colloid complexes is studied. The technique of the research includes i) an analysis of well-known
literature SAXS data; on this basis, ii) constructing a simple model to estimate geometric structure parameters and to obtain
a simulated scattering curve; and iii) comparing the model with the real structure obtained from the SAXS data, using the
reconstruction of electron density distribution. A bicontinuous structure in cubic mesophases is formed.
Dedicated to the memory of Alexander T. Dembo 相似文献
975.
Victor P. Palamodov 《Arkiv f?r Matematik》2004,42(1):119-152
A fundamental solution of the acoustical equation with a variable refraction coefficient is constructed. The solution satisfies
the limiting absorption and radiation conditions. The optimal high frequency estimate is proved for square means of the solution.
The source function for the diffusion equation is a by-product of this construction.
Partially supported by a stipend of the Mathematical Scientific Research Institute at Berkeley, 2001. 相似文献
976.
G. I. Malofeeva O. M. Petrukhin B. Ya. Spivakov E. V. Poteshkina 《Journal of Analytical Chemistry》2003,58(3):211-216
Conditions of the liquid–liquid and solid-phase extraction of metal chelates are compared. The analogy and differences in the behavior of chelates and the effect of stability and partition constants on the completeness of the extraction of metals are discussed. 相似文献
977.
B. B. Damaskin O. A. Baturina V. A. Safonov N. V. Safonov 《Russian Journal of Electrochemistry》2003,39(6):685-691
Effect of the electrode potential on the coadsorption of two organic substances is studied using a set of two mixed Frumkin isotherms and a model of three parallel capacitors in conditions where in the absence of an electric field this system has seven solutions. It is shown that only four of these solutions may correspond to realizable adsorption states. Effect of the electrode potential on the number of possible solutions of the isotherm set, the number of realizable adsorption states, as well as on the composition and properties of a surface layer is considered. 相似文献
978.
We consider a discretized volume V consisting of finite, congruent and attached copies of a tile t. We find a group L
V
the orbit of which, when applied to t, is just V. We show the connection between the structural matrixQ in the formal solution of a boundary value problem formulated for volume V and the so called auxiliary matrix of the graph Γ
v
associated with V. We show boundary value problems to be isomorphic if the graphs associated with the volumes are isomorphic, or, if the covering
groups are Sunada pairs. 相似文献
979.
Sam Efromovich 《Annals of the Institute of Statistical Mathematics》2004,56(2):205-223
A blockwise shrinkage is a popular procedure of adaptation that has allowed the statisticians to establish an impressive bouquet
of asymptotic mathematical results and develop softwares for solving practical problems. Traditionally risks of the estimates
are studied via upper bounds that imply sufficient conditions for a blockwise shrinkage procedure to be minimax. This article
suggests to analyze the estimates via exact (non-asymptotic) lower bounds established for a no-signal setting. The approach
complements the familiar minimax, Bayesian and numerical analysis, it allows to find necessary conditions for a procedure
to attain desired rates, and it sheds a new light on popular choices of blocks and thresholds recommended in the literature.
Mathematical results are complemented by a numerical study.
Supported in part by NSF Grants DMS-9971051 and DMS-0243606. 相似文献
980.
Abhimanyu O. Patil Stephen Zushma Robert T. Stibrany Steven P. Rucker Louise M. Wheeler 《Journal of polymer science. Part A, Polymer chemistry》2003,41(13):2095-2106
Novel nickel(II) bisbenzimidazole complexes were prepared via a three‐step synthetic procedure consisting of aniline/diacid condensation, ligand N‐alkylation, and metal complexation. The complexes were characterized by X‐ray crystallography and found to possess a pseudotetrahedral geometry. Upon activation with methylaluminoxane, these nickel bisbenzimidazoles did not polymerize simple olefins (e.g., ethylene, propylene, and 1‐butene) but were found to carry out the rapid and efficient polymerization of norbornene. The polynorbornene products were characterized by gel permeation chromatography/light scattering, 13C NMR, and IR, and their Mark–Houwink and dn/dc parameters were determined. The molecular weights of the polynorbornenes were very high (weight‐average molecular weight = 587,000–797,000 g/mol). 13C NMR suggested that the polymerization occurred via vinyl addition (i.e., a 2,3‐linked polymer); no ring‐opened product was observed. Thermogravimetric analysis indicated that the polynorbornenes were stable up to 400 °C under nitrogen. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2095–2106, 2003 相似文献