Ferromagnetism and metal-insulator transition in the disordered Hubbard model

A detailed study of the paramagnetic to ferromagnetic phase transition in the one-band Hubbard model in the presence of binary-alloy disorder is presented. The influence of the disorder (with concentrations x and 1-x of the two alloy ions) on the Curie temperature T(c) is found to depend strongly on electron density n. While at high densities, n>x, the disorder always reduces T(c); at low densities, n相似文献   

Experimental studies on the geometrical characteristics determining the system behavior of surface tension autooscillations

Autooscillation of the surface tension is a phenomenon related to Marangoni instability periodically arising and fading by dissolution of a surfactant droplet under a water-air interface. A detailed experimental investigation was performed to clear up the influence of the system geometry on development and characteristics of autooscillations. It was found that the aspect ratio is an additional dimensionless parameter that determines the system behavior equally to the Marangoni number. The influence of the cell diameter, capillary immersion depth, and droplet radius on the autooscillation period and amplitude was studied as well.     

Surface effects in fast atom bombardment mass spectrometry of ethylene glycol-glycerol mixtures

Binary mixtures of ethylene glycols HO(CH₂CH₂O)_xH (x = 3–5) with glycerol were investigated by fast atom bombardment mass Spectrometry. The relative intensities in the ethylene glycol partial mass spectra as a function of concentration exhibit a steep slope in the low concentration range. With increasing concentration the curves asymptotically approach the 100% line. This effect increases from triethylene to pentaethylene glycol. Comparison of these results with those of surface tension measurements leads to the conclusion that the high sensitivity of fast atom bombardment mass Spectrometry for ethylene glycols is caused by the surface-active properties of these compounds, which lead to an enrichment of the surface investigated with the substance molecules.     

X-ray emission from clusters of galaxies and cosmological parameters

Clusters of galaxies are excellent probes of cosmic structure and evolution. X-ray studies of clusters provide some of their key parameters, viz., temperature of the hot intra-cluster gas, its metallicity, X-ray luminosity and surface brightness giving mass distribution and mass-flow rate in the case of cooling flows. X-ray measurements for a large sample of clusters have lead to estimates of the total gravitating mass in them, which can be compared to the virial masses derived from dynamical considerations and gravitational lensing in some of them. X-ray derived total masses are consistent with masses obtained from the other methods after the effects due to the presence of cooling flows are taken into account in the analyses. Estimated virial masses, lack of evolution in X-ray properties, and detection of several very hot clusters at high redshifts indicate a Universe with a low value (≤ 0.3) for the Ω parameter.