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951.
A.I. Veinger A.G. Zabrodskii T.V. Tisnek S.I. Goloshchapov 《Solid State Communications》2005,133(7):455-458
The first observation of low-temperature magnetoresistance (MR) of interference nature in the case of a light doping is reported. The MR occurs in n- and p-type Ge samples at a frequency of 10 GHz at temperatures below 30 K in weak magnetic fields on the background of the classical MR effect associated with electrons in different valleys (n-Ge) and with heavy and light holes (p-Ge). 相似文献
952.
953.
Adsorption of the copper ions from aqueous solutions, benzene, and water on the active carbon obtained by chemical activation
from walnut shells was studied. The active carbon was additionally oxidized with hydrogen peroxide and then impregnated with
nitrogen-containing compounds. As a result of impregnation with melamine, a secondary porosity is formed within the oxidized
active carbon, leading to an increase in the specific surface of the sorbent. A modified carbon surface is heterogeneous,
and the carbons themselves exhibit catalytic activity in the oxidation of luminol and decomposition of hydrogen peroxide. 相似文献
954.
K. Migléczi Gy. Somorjai M. Pátfalusi G. Tóth Gy. Horváth I. Hazai 《Chromatographia》2004,60(1):S67-S74
GYKI-16084 – (+)-(R)-2-{3-(benzo[1,4]dioxan-2-yl-methylamino)-1-propyl}-3(2H)-pyridazinone hydrochloride – is a new drug candidate for the treatment of benign prostatic hyperplasia. In our study the major metabolites formed in the rat and dog were isolated from dog and rat urine, then their structures were elucidated by means of MS and NMR. A two stage solid phase extraction (SPE) procedure and a semi-preparative HPLC method were developed utilizing various mechanisms of separation. The major metabolites proved to be isomeric glucuronides of the benzodioxane moiety hydroxylated at positions 6 or 7 and {2-(2-carboxyethyl)-3(2H)-pyridazinone}. 相似文献
955.
956.
The types of quartz textures found in a large collection of multiphase rocks from different regions of the earth are analyzed. Crystallographic textures of granulite, amphibolite, slate, and gneiss samples are measured, classified, and compared with the similar textures of monomineral rocks. 相似文献
957.
Three fixtures for conducting laboratory fretting fatigue tests are described and their respective testing methods and the
results of the analysis are compared. Each of these fixtures has been used to investigate the effects of various parameters
of interest in fretting fatigue. These fixtures include a unique apparatus in which all load applied to the specimen is transferred
to the fretting pads, an apparatus similar to many found in the literature where partial load transfer occurs across the pads,
and a simplified dovetail fixture in which the clamping load, P, and the shear load, Q, are varied in phase. Select test conditions from prior experiments performed on identical material and resulting in similar
lives ranging from one to ten million cycles from these fixtures are identified. The various testing conditions were used
to compute the unique stress field for each case. The resulting contact stresses were used to calculate crack initiation based
criteria, and to calculate stress intensity factors. The three fixtures were shown to be able to accommodate a range of loads,
fretting pad contours, and specimen geometries that produced a variety of stress fields. A crack-initiation-based criterion
was shown to predict the failure lives of thinner specimens accurately. The stress intensity factor calculations showed the
possibility of a crack arresting for a stress field that decays rapidly and the possibility of a local minimum for K as a function of depth. The fixtures are shown to be complementary in generating data for development of robust fretting
fatigue models that use these criteria. 相似文献
958.
Y. A. Abdu T. Ericsson H. Annersten 《Journal of magnetism and magnetic materials》2004,280(2-3):395-403
Fe–Ni alloys below the Invar region with compositions Fe100−xNix (x=21, 24, and 27 at%) were prepared by high-energy ball milling technique (mechanical alloying). The as-milled samples, characterized by X-ray diffraction and Mössbauer spectroscopy, contain a mixture of (BCC) and γ (FCC) phases, whereas the samples annealed at 650°C for 0.5 h show a single γ (FCC) phase displaying a single line Mössbauer spectrum at room temperature (RT). At low temperature, the Mössbauer spectra of annealed Fe76Ni24 and Fe73Ni27 alloys show the existence of a magnetically split pattern together with a broad singlet, which are ascribed to a high-moment ferromagnetic Ni-rich phase and a low-moment Fe-rich phase, respectively. The Fe-rich phase in annealed Fe76Ni24 alloy, which is paramagnetic at RT, undergoes antiferromagnetic ordering at 40 K, estimated from the dramatic line broadening of its spectrum, giving rise to a small hyperfine field (e.g. 2 T at 6 K). The coexistence of these phases is attributed to phase segregation occurring in these alloys as a result of enhanced atomic diffusion. The stability of these alloys towards martensitic (FCC→BCC) transformation at low temperatures is discussed in connection with the Fe–Ni phase diagram below 400°C. 相似文献
959.
G. T. Tarabrin 《Mechanics of Solids》2008,43(2):241-245
If the curvature of a shell changes under the action of an external force, then the shell can enter a strain state in which it acquires the shape of a plate. In the framework of physical and geometrical linearity, we suggest a solution of the axisymmetric problem about the stress-strain state of a shallow shell of revolution transformed into a circular plate. 相似文献
960.
T. M. Prokop’eva V. A. Mikhailov M. K. Turovskaya E. A. Karpichev N. I. Burakov V. A. Savelova I. V. Kapitanov A. F. Popov 《Russian Journal of Organic Chemistry》2008,44(5):637-646
Bis(dialkylamide)hydrogen dibromobromates were synthesized and their reactivity was investigated in decomposition of diethylphosphonic, diethylphosphoric, and 4-toluenesulfonic acids 4-nitrophenyl esters. The nucleophilic reactivity of a typical α-nucleophile, hypobromite ion, is independent of the source of the active bromine. The cetyltrimethylammonium dibromobromate is a unique reagent for destruction of ecotoxicants. In weakly alkaline media the half-life of 4-nitrophenyl diethylphosphonate did not exceed 6 s at [BrO?] 0.02 mol l?1, and the apparent reaction rate compared to water increased ~40-fold. The main factor governing the micellar effects of surfactants is concentrating the substrate in the micellar pseudophase. 相似文献