Proton-induced L x-ray spectra of heavy elements have been recorded with a Si(Li) x-ray spectrometer of accurately determined resolution function. The intrinsic widths of the Ll and Lα1 lines were obtained by a nonli...
Proton-induced L x-ray spectra of heavy elements have been recorded with a Si(Li) x-ray spectrometer of accurately determined resolution function. The intrinsic widths of the Ll and Lα1 lines were obtained by a nonlinear-least squares fitting procedure. Lα1 widths agree with relativistic independent-particle-model (IPM) calculations, but Ll widths fall some 10–30 % below predictions. This indicates a strong influence of many-body effects on the decay of the 3s hole state; a similar influence is already well established for the 2s state. Relative intensities of the weak, electric-dipole-forbidden lines Lt and Ls are in good accord with IPM calculations.
A relativistic gravitational theory in (1 + 1) dimensions is presented which exhibits many of the qualitative features of (3 + 1)-dimensional general relativity. The field equations are simple enough for undergraduate...
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A relativistic gravitational theory in (1 + 1) dimensions is presented which exhibits many of the qualitative features of (3 + 1)-dimensional general relativity. The field equations are simple enough for undergraduates to solve yet rich enough in structure to form a useful pedagogical example for exploring the qualitative features of relativistic gravitation. Black hole solutions to the field equations of the theory are derived and its relationship to Newtonian gravity is discussed in detail.
A new confocal scanning-stage transmitted-light and reflected-light laser microscope is described. In addition to allowing confocal transmitted-light imaging, this microscope has the unique feature of imaging both the...
A new confocal scanning-stage transmitted-light and reflected-light laser microscope is described. In addition to allowing confocal transmitted-light imaging, this microscope has the unique feature of imaging both the top and bottom of a specimen in reflected light, with the two images in perfect registration. Only one detector is used;different imaging modes can be selected by simple rotation of the polarizers. Several confocal images are presented, chosen to illustrate the unique features of the instrument.
First-principles theoretical results are reported for the specific heats and closely related thermodynamic quantities, required in the determination of the characteristics of the supercooled metallic liquids, for Al, ...
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First-principles theoretical results are reported for the specific heats and closely related thermodynamic quantities, required in the determination of the characteristics of the supercooled metallic liquids, for Al, Rb and Ca0.7Mg0.3 metals. Of these results, those for the specific heats are fully analyzed and discussed by considering computer-simulation results on the atomic motion in the supercooled-liquid region. It now appears that the specific heat at constant pressure behaves as a monotonically increasing function of temperature in decreasing from the melting temperature to the glass-transition temperature for those supercooled metallic liquids that have high glass-forming ability.
A first-principles thermodynamic calculation appropriate for metallic glasses is first proposed and is then carried out for the metals Al and Ca0.7Mg0.3. The calculated results are compared with previously obtained re...
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A first-principles thermodynamic calculation appropriate for metallic glasses is first proposed and is then carried out for the metals Al and Ca0.7Mg0.3. The calculated results are compared with previously obtained results for the supercooled-liquid states of pure Al metal. It now appears that, because of the significant change in the derivative of the volume with respect to temperature on going through the liquid-glass transition, the thermodynamic quantities vary drastically in this region, for those metals that can form glasses in the laboratory through the liquid-quenching process.
The dc-conductivity, plasma frequency and the specific heat are calculated as a function of doping for La2-xSrxCuO4 and related compounds. There is good quantitative agreement with experimental data. The volume includ...
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The dc-conductivity, plasma frequency and the specific heat are calculated as a function of doping for La2-xSrxCuO4 and related compounds. There is good quantitative agreement with experimental data. The volume included by the Fermi surface obeys Luttinger Theorem. The calculations are based on quasiparticles whose energy spectrum has tight binding form renormalized by strong correlations and originating from the t-t'-J model. We have used the relaxation time approximation.
The resistivity and T(c) of Bi2Sr2CaCu2O8+delta can be reversibly modified at room temperature using an electrochemical cell. Whereas reducing with up to 0.02 mole fraction of charge enhances the T(c) systematically f...
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The resistivity and T(c) of Bi2Sr2CaCu2O8+delta can be reversibly modified at room temperature using an electrochemical cell. Whereas reducing with up to 0.02 mole fraction of charge enhances the T(c) systematically from about 73 K to 88 K, further reduction decreases the T(c) again and eventually goes on to suppress superconductivity altogether. Above 0.10 mole fraction p(T) loses its metallic character and assumes a negative slope which, above 0.50 mole fraction, can be modeled in terms of a semiconductor with an activation energy of 30 +/- 2 meV. Oxidizing the latter material restores superconductivity, albeit the reversibility is not complete. Electrochemical and EDX data are compatible with the reversible solid state diffusion of copper;we propose that copper is intercalating.
We study the formulation of SU(2) Wess-Zumino-Witten theories with arbitrary level k away from criticality. Following the discussion of A.B. Zamolodchikov for minimal conformal models, we derive a counting argument th...
We study the formulation of SU(2) Wess-Zumino-Witten theories with arbitrary level k away from criticality. Following the discussion of A.B. Zamolodchikov for minimal conformal models, we derive a counting argument that leads to a prediction of the number of higher integrals of motion. We explicitly construct these higher integrals of motion for the special cases k = 1 and k = 2 (where these models are perturbed by some relevant primary field) and compare the results with the general counting argument. We consider renormalization group trajectories for k >> 1, and calculate the beta-function. Unlike the minimal models we do not find any link between fixed points in the SU(2) theories.
Molecular-dynamics simulations of 500 particles have been performed to study the icosahedral order and the defects in the supercooled liquid and glass states of metallic Mg3Ca7. Not only are Frank-Kasper polyhedra and...
Molecular-dynamics simulations of 500 particles have been performed to study the icosahedral order and the defects in the supercooled liquid and glass states of metallic Mg3Ca7. Not only are Frank-Kasper polyhedra and Bernal ‘‘hole’’ polyhedra detected, but also a variety of defective icosahedra. Especially, the number of the type of defective icosahedron defined by eight 1551 bonds, two 1661 bonds, and two 1441 bonds is much greater than the number of any kind of Frank-Kasper and Bernal polyhedra. This strongly supports the physical picture of liquids and glasses being a disordered, entangled array of +72° and -72° disclination lines in an icosahedral medium.
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