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951.
952.
A. V. Kotikov G. Parente J. Sánchez Guillen 《Zeitschrift fur Physik C Particles and Fields》1993,58(3):465-469
A renormalization scheme invariant analysis of the deep inelastic scattering structure functionF 2 andF L is performed. Expressions for the moments are given in this approach. We find a significant improvement of the agreement withR=σ L /σ T -SLAC data with respect to the conventional perturvative \((\overline {MS} )\) analysis. Higher twist corrections are also required confirming previous evidence. 相似文献
953.
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956.
L. F. Capitán-Vallvey R. Avidad Castañeda M. del Olmo Iruela J. L. Vilchez Quero 《Mikrochimica acta》1993,112(1-4):55-62
Benzo(a)pyrene (BaP) and pyrene (Pyr) are two polycyclic aromatic hydrocarbons (PAHs) showing native fluorescence in solution. Both compounds have been determined in water at trace levels by solid-phase spectrofluorimetry, in which BaP and Pyr are fixed on Sephadex G-25 gel and the relative fluorescence intensity is measured after the system is packed in a 1-mm silica cell. First-derivative synchronous spectra obtained at =38 nm were used to determine BaP and Pyr in the presence of other potentially interferent PAHs. The spectral characteristics of the PAHs-gel system are described, the applicable concentration ranges being 0.4–2.5 ng/ml for BaP and 0.7–4.5 ng/ml for Pyr. The relative standard deviations were 1.1% and 1.4% for BaP and Pyr respectively. The detection limits were 0.04 ng/ml for BaP and 0.1 ng/ml for Pyr. The method was applied to the analysis of both compounds in water at trace levels and a recovery study on tap, natural and sea waters was carried out. 相似文献
957.
The influence of -irradiation on the paramagnetic properties of non-doped polyacetylene at low and high radiation doses has been studied and summarized. The dependence of the EPR spectra on the radiation dose in irradiated polyacetylene has been measured. No essential changes of the spin mobility as a consequence of irradiation were observed. Our measurements of spin concentration confirm the high resistivity of non-doped polyacetylene to radiation. 相似文献
958.
The development of a rapid and reproducible method for the separation of plutonium from soil samples is described. Tetravalent plutonium is extracted from 8M HNO3 into 30% Aliquat-336/toluene mixture. Uranium and thorium are removed with nitric and hydrochloric acid washes. Plutonium is backextracted with HCl–H2C2O4 and HCl–HF solutions. Plutonium is coprecipitated with NdF3 and filtrated onto a 0.1–0.2 m membrane filter to prepare a source for -spectrometry. The chemical yields of separation are about 50–60%. 相似文献
959.
Zoltán Füredi 《Journal of Geometry》1993,46(1-2):55-65
Let s1 (n) denote the largest possible minimal distance amongn distinct points on the unit sphere
. In general, let sk(n) denote the supremum of thek-th minimal distance. In this paper we prove and disprove the following conjecture of A. Bezdek and K. Bezdek: s2(n) = s1([n/3]). This equality holds forn > n0 however s2(12) > s1(4).We set up a conjecture for sk(n), that one can always reduce the problem of thek-th minimum distance to the function s1. We prove this conjecture in the casek=3 as well, obtaining that s3(n) = s1([n/5]) for sufficiently largen.The optimal construction for the largest second distance is obtained from a point set of size [n/3] with the largest possible minimal distance by replacing each point by three vertices of an equilateral triangle of the same size . If 0, then s2 tends to s1([n/3]). In the case of the third minimal distance, we start with a point set of size [n/5] and replace each point by a regular pentagon. 相似文献
960.
Daniel H. Huson 《Geometriae Dedicata》1993,47(3):269-296
Algorithms based on the theory of Delaney-Dress symbols are discussed that can be used to recursively produce all possible equivariant types of tile-k-transitive tilings of the Euclidean plane, the sphere and the hyperbolic plane, for any (reasonable)k. A number of results can be obtained using computer implementations of the algorithms. 相似文献