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排序方式: 共有311条查询结果,搜索用时 15 毫秒
11.
M. Saiki R. E. P. Leite F. A. Genezini L. T. Grinberg R. E. L. Ferretti J. M. Farfel C. Suemoto C. A. Pasqualucci W. Jacob-Filho 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):267-272
Studies have shown that there is a potential relationship between the levels of trace elements in cerebral tissues and neurological disorders. However, there are few publications available on the elemental composition of these tissues as well as for different regions of the brain. The aim of this study was to investigate trace element differences in various regions of the human brain from an elderly population of normal individuals. Brain samples from 31 individuals of both genders, aged 51–95 years were provided by the Brain Bank of the Brazilian Aging Study Group of the São Paulo University, Medical School. The tissues from the regions of the hippocampus, cerebellum and frontal, parietal, temporal, occipital cortex were dissected using a titanium knife, ground, freeze-dried and then analyzed by instrumental neutron activation analysis (INAA). Samples and element standards were irradiated with a neutron flux at the IEA-R1 nuclear research reactor for Br, Fe, K, Na, Rb, Se and Zn determinations. One-way ANOVA test (p < 0.05) was used to compare the results which showed significant differences for several elements among the brain regions. Most of our brain analysis results agreed with the literature data. The results were also submitted for brain region classification by cluster analysis. 相似文献
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Anna Goldberg Vitali Grinberg Irina Utepova Oleg Chupakhin Igor Eremenko 《Journal of organometallic chemistry》2011,696(13):2607-2610
New ionic complexes [ML2(MeCN)2]?2Otf (M = Co or Ni; L = 6-ferrocenyl-2,2′-bipyridyl) were synthesized and characterized by single-crystal X-ray diffraction. Cyclic voltammograms of the compounds [ML2(MeCN)2]?2Otf in CH2Cl2 show good cycle stability over 100 cycles in the quasi-reversible oxidation potential range (from −0.25 to 0.5 V). 相似文献
14.
Maciej Garbarczyk Farida Grinberg Nikolaus Nestle Winfried Kuhn 《Journal of Polymer Science.Polymer Physics》2001,39(18):2207-2216
We present a novel NMR approach to the determination of crosslink densities in rubber materials. The method is based on the dipolar correlation effect (DCE) on the stimulated echo examined in a series of rubber samples and linear polyisoprene. The parameter evaluated from the echo attenuation curves is the mean‐squared dipolar fluctuation associated with anisotropic reorientations of macromolecular backbones. The contributions to the DCE of the constraints due to excluded volume effects and chemical crosslinks are estimated. A strong dependence of the mean‐squared dipolar fluctuation on the crosslink density of rubber combined with the simplicity of performing the measurements with inexpensive low‐field instruments suggests that the DCE is a useful tool for routine applications. The potential and problems of performing DCE measurements in low‐magnetic‐field conditions are discussed in detail. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2207–2216, 2001 相似文献
15.
We address the failure in scalability of large-scale parallel simulations that are based on (semi-)implicit time-stepping and hence on the solution of linear systems on thousands of processors. We develop a general algorithmic framework based on domain decomposition that removes the scalability limitations and leads to optimal allocation of available computational resources. It is a non-intrusive approach as it does not require modification of existing codes. Specifically, we present here a two-stage domain decomposition method for the Navier–Stokes equations that combines features of discontinuous and continuous Galerkin formulations. At the first stage the domain is subdivided into overlapping patches and within each patch a C0 spectral element discretization (second stage) is employed. Solution within each patch is obtained separately by applying an efficient parallel solver. Proper inter-patch boundary conditions are developed to provide solution continuity, while a Multilevel Communicating Interface (MCI) is developed to provide efficient communication between the non-overlapping groups of processors of each patch. The overall strong scaling of the method depends on the number of patches and on the scalability of the standard solver within each patch. This dual path to scalability provides great flexibility in balancing accuracy with parallel efficiency. The accuracy of the method has been evaluated in solutions of steady and unsteady 3D flow problems including blood flow in the human intracranial arterial tree. Benchmarks on BlueGene/P, CRAY XT5 and Sun Constellation Linux Cluster have demonstrated good performance on up to 96,000 cores, solving up to 8.21B degrees of freedom in unsteady flow problem. The proposed method is general and can be potentially used with other discretization methods or in other applications. 相似文献
16.
S. Mahlik B. Kukliński Y.M. Yen R.S. Meltzer M. Grinberg 《Journal of luminescence》2008,128(5-6):715-717
The 4f65d1(e)→4f7 emission (normal) of Eu2+ in SrF2 and normal and anomalous emissions of Eu2+ in BaF2 are studied as a function of pressure and temperature. Although in BaF2 both emissions (anomalous and normal) shift with pressure in the same spectral direction (a red shift), the anomalous emission converts to the normal emission when the pressure increases to 33 kbar. Considering the dependence of BaF2:Eu2+ luminescence on the pressure and temperature we have found that spectral transformation takes place due to a smooth pressure-induced level crossing at approximately the same pressure as the phase transition. 相似文献
17.
F. Haber und S. Grinberg 《Fresenius' Journal of Analytical Chemistry》1897,36(1):557-567
Ohne Zusammenfassung(Mittheilung aus dem Chemisch-technischen Institut der Technischen Hochschule zu Karlsruhe.) 相似文献
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19.
N. D. Kagramanov S. R. Sterlin V. A. Grinberg 《Russian Journal of Electrochemistry》2009,45(11):1306-1309
Electrolysis of azobenzene (I) in the system of Et4NF · 3HF, MeCN results in predominant fluorination of the products of polymerization of I formed in the course of electrolysis. Also, m-fluoroazobenzene (II) and o-fluoroazobenzene (III) (II: III = 4: 1) were obtained with a low yield. Anomalously high content of m-isomer II is probably related to redistribution of localization of electron-deficient centers in cation-radical I as a result of its protonation by acidic electrolyte. 相似文献
20.
V. A. Grinberg N. A. Mayorova A. A. Pasynskii 《Russian Journal of Electrochemistry》2009,45(12):1321-1326
A bimetallic platinum-tin catalyst is synthesized by depositing on highly dispersed carbon black from a cluster of the corresponding
metals with atomic ratio in the surface layer 2: 1. The obtained catalyst was characterized by X-ray diffraction and electron-dispersion
analyses, laser mass-spectrometry, and transmission electron microscopy. According to voltammetry data, specific characteristics
of the synthesized cluster catalyst in the reaction of ethanol direct oxidation are superior to those of the platinum-tin
catalyst described in literature. 相似文献