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Selected Abstracts

Preparation and Electrical Properties of New Oxide Ion Conductors Ce6,xGdxMoO15,, (0.0,x,1.8)

Defeng Zhou
A series of oxide ion conductors Ce6,xGdxMoO15,, (0.0,x,1.8) have been prepared by the sol,gel method. Their properties were characterized by differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), Raman, IR, X-ray photoelectron spectroscopy (XPS), and AC impedance spectroscopy. The XRD patterns showed that the materials were single phase with a cubic fluorite structure. The conductivity of Ce6,xGdxMoO15,, increases as x increases and reaches the maximum at x=0.15. The conductivity of Ce4.5Gd1.5MoO15,, is ,t=3.6 × 10,3 S/cm at 700°C, which is higher than that of Ce4.5/6Gd1.5/6O2,, (,t=2.6 × 10,3 S/cm), and the corresponding activation energy of Ce4.5Gd1.5MoO15,, (0.92 eV) is lower than that of Ce4.5/6Gd1.5/6O2,, (1.18 eV). [source]

Quantum criticality of Ce1,xLaxRu2Si2: The magnetically ordered phase

Stéphane Raymond
Abstract We report specific heat and neutron scattering experiments performed on the system Ce1,xLaxRu2Si2 on the magnetic side of its quantum critical phase diagram. The Kondo temperature does not vanish at the quantum phase transition and elastic scattering indicates a gradual localization of the magnetism when x increases in the ordered phase. [source]

Monte Carlo study of cycloamylose: Chain conformation, radius of gyration, and diffusion coefficient

BIOPOLYMERS, Issue 2 2002
Yasushi Nakata
Abstract Cyclic (1 , 4)-,- D -glucan chains with or without excluded volume have been collected from a huge number (about 107) of linear amylosic chains generated by the Monte Carlo method with a conformational energy map for maltose, and their mean-square radii of gyration ,S2, and translational diffusion coefficients D (based on the Kirkwood formula) have been computed as functions of x (the number of glucose residues in a range from 7 to 300) and the excluded-volume strength represented by the effective hard-core radius. Both ,S2,/x and D in the unperturbed state weakly oscillate for x < 30 and the helical nature of amylose appears more pronouncedly in cyclic chains than in linear chains. As x increases, these properties approach the values expected for Gaussian rings. Though excluded-volume effects on them are always larger in cycloamylose than in the corresponding linear amylose, the ratios of ,S2, and the hydrodynamic radius of the former to the respective properties of the latter in good solvents can be slightly lower than or comparable to the (asymptotic) Gaussian-chain values when x is not sufficiently large. An interpolation expression is constructed for the relation between the gyration-radius expansion factors for linear and cyclic chains from the present Monte Carlo data and the early proposed asymptotic relation with the aid of the first-order perturbation theories. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 72,79, 2002 [source]

Crystallographic and Electrochemical Characteristics of La0.7Mg0.3Ni5.0,x(Al0.5Mo0.5)x Hydrogen-Storage Alloys,

CHEMPHYSCHEM, Issue 3 2005
Xin Bo Zhang Dr.
Abstract The structure, hydrogen-storage property and electrochemical characteristics of La0.7Mg0.3Ni5.0,x(Al0.5Mo0.5)x(x=0,0.8) hydrogen-storage alloys have been studied systematically. X-ray diffraction Rietveld analysis shows that all the alloys consist of an La(La,Mg)2Ni9 phase and an LaNi5 phase. The pressure,composition isotherms indicate that the hydrogen-storage capacity first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. Electrochemical measurements show that the maximum discharge capacity and the exchange-current density of the alloy electrodes increase as x increases from 0 to 0.6 and then decrease when x increases further from 0.6 to 0.8. Moreover, the low-temperature dischargeability of the alloy electrodes increases monotonically with increasing x in the alloys. [source]