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111.
Thin film capacitors of CeO2 were fabricated by thermal evaporation. The dielectric properties of these films were studied in the frequency range 0.05–16 KHz at various temperatures, starting from liquid nitrogen temperature to 390 K. The effect of annealing on capacitance and tan δ were studied for different frequencies. The behaviour was explained on the basis of relief in strain energy. The plot between current density and temperature was drawn, and from the slope of the plot the activation energy was calculated and found to be 0.52 ev. The results were discussed. 相似文献
112.
Cerium Oxide films were prepared by vacuum thermal evaporation from tantalum boat in a conventional vacuum coating unit. Current-voltage characteristics were studied for different film thicknesses. The breakdown voltage (VB) and dielectric field strength (EB) were calculated. It is found that the breakdown voltage increases and dielectric field strength decreases as the thickness of the film increases. The applicability of Forlani-Minnaja relation is discussed. Current-voltage characteristics were also drawn at different temperatures and breakdown voltages were calculated. The breakdown voltage decreases as the temperature of the structure increases but the variation is nonlinear. The variation of current density with temperature was studied and the activation energy for the migration of charge carriers was calculated and it is about 0.52 ev. The results were discussed. 相似文献
113.
B. Gopala Krishna G. Ravi Chandra S. V. Suryanarayana 《Crystal Research and Technology》1992,27(4):569-581
Samples with the nominal composition Bi2Sr2CaCu2Oy with na doped at the Ca site and K doped at the Sr site are prepared by solid state reaction method. From the X-ray diffraction data it is found that all the the samples have exhibited a single phase 2212. The D.C. electrical resistivity data show that for Na-doped samples the Tc (zero) varies from 80 K to 85 K and for K-doped samples it is from 79 K to 82 K. The loss of oxygen from these samples around 400°C was confirmed by high temperature dilatometry. The variation of the thermal expansion coefficient (“α”) with temperature for different alkali dopings are discussed. Also the samples with the nominal composition Bi4Sr3Ca3Cu4−xAgxOy (with x = 0, 0.1, 0.2, 0.3) were studied. 相似文献
114.
Lauren M. Reid Ileana Guzzetti Tor Svensson Anna-Carin Carlsson Wu Su Tomas Leek Lena von Sydow Werngard Czechtizky Marija Miljak Chandra Verma Leonardo De Maria Jonathan W. Essex 《Chemical science》2022,13(7):1957
Understanding the conformational ensembles of intrinsically disordered proteins and peptides (IDPs) in their various biological environments is essential for understanding their mechanisms and functional roles in the proteome, leading to a greater knowledge of, and potential treatments for, a broad range of diseases. To determine whether molecular simulation is able to generate accurate conformational ensembles of IDPs, we explore the structural landscape of the PLP peptide (an intrinsically disordered region of the proteolipid membrane protein) in aqueous and membrane-mimicking solvents, using replica exchange with solute scaling (REST2), and examine the ability of four force fields (ff14SB, ff14IDPSFF, CHARMM36 and CHARMM36m) to reproduce literature circular dichroism (CD) data. Results from variable temperature (VT) 1H and Rotating frame Overhauser Effect SpectroscopY (ROESY) nuclear magnetic resonance (NMR) experiments are also presented and are consistent with the structural observations obtained from the simulations and CD. We also apply the optimum simulation protocol to TP2 and ONEG (a cell-penetrating peptide (CPP) and a negative control peptide, respectively) to gain insight into the structural differences that may account for the observed difference in their membrane-penetrating abilities. Of the tested force fields, we find that CHARMM36 and CHARMM36m are best suited to the study of IDPs, and accurately predict a disordered to helical conformational transition of the PLP peptide accompanying the change from aqueous to membrane-mimicking solvents. We also identify an α-helical structure of TP2 in the membrane-mimicking solvents and provide a discussion of the mechanistic implications of this observation with reference to the previous literature on the peptide. From these results, we recommend the use of CHARMM36m with the REST2 protocol for the study of environment-specific IDP conformations. We believe that the simulation protocol will allow the study of a broad range of IDPs that undergo conformational transitions in different biological environments.A protocol for simulating intrinsically disordered peptides in aqueous and hydrophobic solvents is proposed. Results from four force fields are compared with experiment. CHARMM36m performs the best for the simulated IDPs in all environments. 相似文献
115.
The present paper reports for the first time an exact analytic expression that can be used for obtaining fracture stress σF, when fracture occurs in the elastic limit and also when fracture occurs after general yield (σF > σY) in a brittle solid. The present paper may provide a new basis to fracture-safe design of brittle materials. 相似文献
116.
117.
Yogendra K. Gautam Amit K. ChawlaRajan Walia R.D. AgrawalRamesh Chandra 《Applied Surface Science》2011,257(14):6291-6295
Structural and optical properties of pure Mg thin film coated with Pd have been investigated. Pd-capped Mg thin films had been prepared by DC magnetron sputtering. This work presents an ex situ study on hydrogenation and dehydrogenation kinetics of Pd/Mg films at different conditions using XRD, AFM and optical spectrophotometer. We have succeeded to load thin films of Mg to MgH2 at normal temperature and normal pressure of hydrogen gas. In hydrogenation, α-MgH2 phase of magnesium hydride was observed in hydrogenated films at 200 °C and γ-MgH2 at 250 °C respectively. The desorption kinetics in vacuum also revealed the phase transformation α-MgH2 to γ-MgH2. A reflectance change was observed in hydrogenated films in comparison of as deposited thin film. Hydrogenated (H loaded) samples were observed partially transparent in comparison of as deposited. 相似文献
118.
119.
120.
Hydroxyl compounds readily add to dihydropyran in presence of a catalytic amount of ceric ammonium nitrate to give high yield of tetrahydropyranyl ethers. 相似文献