Phenomenological constraints due to CP violation in the K−K¯ system and the extent of B−B¯ mixing are used to determine the constraints on the various parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix...
Phenomenological constraints due to CP violation in the K−K¯ system and the extent of B−B¯ mixing are used to determine the constraints on the various parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix given the Ansatz is symmetric. An existing parametrization for the CKM matrix is shown to be the most general parametrization for the symmetric Ansatz. This Ansatz implies that the mass of the t quark is at least 180 GeV.
Superconductivity has been observed in originally semiconducting ceramic samples of La2CuO4 following oxidation in an electrochemical cell at room temperature. After processing, the room-temperature resistivity is low...
Superconductivity has been observed in originally semiconducting ceramic samples of La2CuO4 following oxidation in an electrochemical cell at room temperature. After processing, the room-temperature resistivity is lowered by over an order of magnitude and, on cooling below 150 K, acquires a metallic temperature dependence. The superconducting transition occurs near 45 K. Magnetic-susceptibility measurements confirm the bulk nature of the superconductivity. Furthermore, by reversing the polarization of the cell, semiconducting La2CuO4 can again be produced. The homogeneity of the processed samples was verified by x-ray powder diffraction and energy-dispersive x-ray elemental analysis.
A generalization of the Landau–de Gennes phenomenological theory of smectic-A liquid crystals is described. The theory is based on a Landau-Ginzburg free energy that includes local and nonlocal parts. The local part ...
A generalization of the Landau–de Gennes phenomenological theory of smectic-A liquid crystals is described. The theory is based on a Landau-Ginzburg free energy that includes local and nonlocal parts. The local part consists of the isotropic-Ising-model free energy and de Gennes’s phenomenological free energy of the nematic phase. The nonlocal part is derived from the form of two-body contributions to the free energy in molecular density-functional theories, expanded in gradients of the number density and orientational order parameter. A mean-field approximation to the theory is analyzed by both Landau expansion and by a full numerical solution, involving Fourier-series representations of the number density and an orientational order parameter with an appropriately large number of Fourier coefficients. The main purpose of the analysis is to show that the smectic phase results from the instability of a uniform phase induced by the gradient terms in the free energy, particularly those that couple modulations in the density and orientational order parameter.
In this paper, a model for water-oil-surfactant mixtures, which we have previously studied on two- and three-dimensional lattices, is now studied on a one-dimensional lattice. In this case we are able to obtain exact ...
In this paper, a model for water-oil-surfactant mixtures, which we have previously studied on two- and three-dimensional lattices, is now studied on a one-dimensional lattice. In this case we are able to obtain exact results, whereas on the higher-dimensional lattices it was necessary to use approximations. This one-dimensional model produces correlation and structure functions that are similar to those obtained for the disordered phase on the two- and three-dimensional lattices. The disorder line is obtained from the water-water correlation function and the Lifshitz line is derived from the water-water structure function. One or the other of these lines is typically used to divide the disordered phase into a region of ordinary disordered fluid and a microemulsion region. Both these lines calculated exactly for the one-dimensional lattice behave similarly to their counterparts on the two- and three-dimensional lattices calculated by various approximations.
An elementary discussion of time-dependent correlation functions is presented. These functions are discussed in the context of dielectric relaxation and nuclear magnetic resonance for two forms of decay: Simple expone...
详细信息
An elementary discussion of time-dependent correlation functions is presented. These functions are discussed in the context of dielectric relaxation and nuclear magnetic resonance for two forms of decay: Simple exponential and stretched (Kohlrausch-Williams-Watts) exponential. A guide to the calculation of the stretched exponential fitting parameters using numerical methods is given. Computational notes include comments on the truncation of mathematical series used.
7Li nuclear magnetic resonance (NMR) linewidths and spin-lattice relaxation times for poly(propylene-glycol) complexed with a range of concentrations of LiCF3SO3 are reported over the temperature region from 205 to 40...
R. A. Moore; Comment on ‘‘A wave‐packet description of the motion of a charged particle in a uniform magnetic field,’’ by W. Zimmermann, Jr. [Am. J. Phys. 57, 5
R. A. Moore; Comment on ‘‘A wave‐packet description of the motion of a charged particle in a uniform magnetic field,’’ by W. Zimmermann, Jr. [Am. J. Phys. 57, 5
C. G. Gray; Comment on ‘‘Fisher information as the basis for the Schrödinger wave equation,’’ by B. Roy Frieden [Am. J. Phys. 57, 1004–1008 (1989)], American Jo
C. G. Gray; Comment on ‘‘Fisher information as the basis for the Schrödinger wave equation,’’ by B. Roy Frieden [Am. J. Phys. 57, 1004–1008 (1989)], American Jo
Bi 2 Sr 2 CaCu 2 O 8+δ can be reversibly intercalated at room temperature with copper and silver using an electrochemical cell. Silver can be intercalated to about 0.01 mole fraction, and enhances the T c by about 15...
详细信息
Bi 2 Sr 2 CaCu 2 O 8+δ can be reversibly intercalated at room temperature with copper and silver using an electrochemical cell. Silver can be intercalated to about 0.01 mole fraction, and enhances the T c by about 15 K. Copper intercalates to about 0.4 mole fraction and thereby not only quenches superconductivity completely but, along with increasing the room temperature resistivity considerably, changes the ϱ(T) dependence to make the material appear semiconducting. Deintercalations restores superconductivity. These dramatic and reversible effects suggest that intercalation may be a valuable technique for studying some of the high T c copper oxides.
Single crystal open-circuit potential measurements of Ag x TaS 2 /Ag electrochemical cells at 310 K have provided new insight into the Ag x TaS 2 intercalation system by providing evidence of new phases in the stage 1...
详细信息
Single crystal open-circuit potential measurements of Ag x TaS 2 /Ag electrochemical cells at 310 K have provided new insight into the Ag x TaS 2 intercalation system by providing evidence of new phases in the stage 1 region, and by clearly showing that the intercalation reaction starts with a two phase region. Potentiometric silver diffusivity measurements using Ag 2 3 TaS 2 single crystals indicate that during intercalation or deintercalation the chemical diffusion coefficient, D̄ , at 310 K is 2±1×10 −8 cm 2 s −1 . Although this is two orders of magnitude smaller than published results using powdered compacts, it still corresponds very much to that of a superionic conductor.
暂无评论