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排序方式: 共有312条查询结果,搜索用时 15 毫秒
31.
32.
R. Rentzsch B. Sandow A. N. Ionov N. V. Agrinskaya M. J. Lea P. Fozooni 《Czechoslovak Journal of Physics》1996,46(5):2447-2448
In this work, we report the results of magnetoresistance studies of variable range hopping down to 30 mK in isotopically engineered Ge with low compensation, and in n-CdTe crystals. Experimentally we find a decrease and disappearance of the negative magnetoresistance with decreasing temperature down to 200 mK, in weak magnetic fields. Such behaviour is in disagreement with the quantum interference theory of Nguen, Spivak and Shklovskii. 相似文献
33.
K. Woidich und A. Bolliger 《Fresenius' Journal of Analytical Chemistry》1943,125(1-2):60-61
Ohne Zusammenfassung 相似文献
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35.
Analysis of diethylstilbestrol and its impurities in tablets using reversed-phase high-performance liquid chromatography 总被引:1,自引:0,他引:1
A high-performance liquid chromatographic (HPLC) method is described which is capable of resolving cis- and trans-diethylstilbestrol (DES), DES mono- and dimethyl ethers and 4,4'-dihydroxystilbene. The mobile phase and internal standard used stabilise the cis-trans DES isomer ratio, and the method is capable of quantitating both isomers in dosage forms without derivatisation. Recovery of DES from tablets is quantitative. Results of tablet analyses using this method are compared with those obtained with the official spectrophotometric procedure. 相似文献
36.
Colin Lea 《Trends in analytical chemistry : TRAC》1983,2(5):118-121
Analysis of single atomic layers at surfaces and interfaces is now possible routinely, using such techniques as Auger electron spectroscopy, X-ray photoelectron spectroscopy and secondary ion mass-spectroscopy. The handling of specimen surfaces before analysis is therefore critical to ensure a valid measurement of composition. 相似文献
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We demonstrate the advantages of randomization in coherent quantum dynamical control. For systems which are either time-varying or require decoupling cycles involving a large number of operations, we find that simple randomized protocols offer superior convergence and stability as compared to deterministic counterparts. In addition, we show how randomization may allow us to outperform purely deterministic schemes at long times, including combinatorial and concatenated methods. General criteria for optimally interpolating between deterministic and stochastic design are proposed and illustrated in explicit decoupling scenarios relevant to quantum information storage. 相似文献
39.
A method for the simultaneous determination of 4(5)-methylimidazole (4MeI) and 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)-imidazole (THI) was developed using SPE and HPLC/MS. Solid-phase extraction using SCX Disc cartridges was used for isolation of the analytes from liquid samples. The lower LOQwas 0.1 ng/mL for 4MeI and 0.2 ng/ mL for THI. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients >0.999. The CV for the intra- and inter-day precision was <5% (n = 6); the accuracy was in the range 98-103%. The recovery was > or = 97 and > or = 98% for THI and 4MeI, respectively. The method was used to determine THI and 4MeI in beverages, coffee, caramel colours and other samples. 相似文献
40.
Hilde Lea Lein Øystein Skottun Andersen Per Erik Vullum Edgar Lara-Curzio Randi Holmestad Mari-Ann Einarsrud Tor Grande 《Journal of Solid State Electrochemistry》2006,10(8):635-642
Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship
observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials.
Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature
creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending
was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture
mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface
of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient
temperature fracture strength and toughness. 相似文献