6,944 research outputs found
Scaling of Coulomb pseudo-potential in s-wave narrow-band superconductors
The Coulomb pseudo-potential is extracted by fitting the numerically
calculated transition temperature of the Eliashberg-Nambu equation which
is extended to incorporate the narrow-band effects, that is, the vertex
correction and the frequency dependence of the screened Coulomb interaction. It
is shown that even for narrow-band superconductors, where the fermi energy is comparable with the phonon frequency , the Coulomb
pseudo-potential is a pertinent parameter, and is still given by , provided is
appropriately scaled.Comment: 5 pages, 3 figures, accepted for publication by Phys. Rev.
Estimation of an Examinee's Ability in the Web-Based Computerized Adaptive Testing Program IRT-CAT
We developed a program to estimate an examinee s ability in order to provide freely available access to a web-based computerized adaptive testing (CAT) program. We used PHP and Java Script as the program languages, PostgresSQL as the database management system on an Apache web server and Linux as the operating system. A system which allows for user input and searching within inputted items and creates tests was constructed. We performed an ability estimation on each test based on a Rasch model and 2- or 3-parametric logistic models. Our system provides an algorithm for a web-based CAT, replacing previous personal computer-based ones, and makes it possible to estimate an examinee's ability immediately at the end of test
Synthesis of Ag Nanostructures by Photochemical Reduction Using Citrate-Capped Pt Seeds
A simple synthesis of Ag nanostructures such as nanorods and nanowires has been demonstrated with citrate-capped Pt seeds. UV-visible spectra and photographs of the synthesized solutions at different UV exposure times showed that the citrate-capped Pt seed played a crucial role in the growth of Ag nanostructures. After UV exposure of the colloidal solution for 60 min, the average diameter, length, and aspect ratio of the Ag nanostructures were about 95 nm, 2.1 nm, and 22, respectively. The photochemical reduction is hypothesized to result from photoelectron transfer from adsorbed citrate to Pt nanoparticle seed allowing Ag ions to form Ag nanostructures. Based on X-ray diffraction spectra and transmission electron microscope images, the synthesized Ag nanostructures were a face-centered cubic single crystal with good purity. These results suggest that the photochemical reduction method can provide Ag nanostructures in the presence of citrate-capped Pt seeds at room temperature for anisotropic Ag products
Dynamical mean-field theory of Hubbard-Holstein model at half-filling: Zero temperature metal-insulator and insulator-insulator transitions
We study the Hubbard-Holstein model, which includes both the
electron-electron and electron-phonon interactions characterized by and
, respectively, employing the dynamical mean-field theory combined with
Wilson's numerical renormalization group technique. A zero temperature phase
diagram of metal-insulator and insulator-insulator transitions at half-filling
is mapped out which exhibits the interplay between and . As () is
increased, a metal to Mott-Hubbard insulator (bipolaron insulator) transition
occurs, and the two insulating states are distinct and can not be adiabatically
connected. The nature of and transitions between the three states are
discussed.Comment: 5 pages, 4 figures. Submitted to Physical Review Letter
Isolation of p-hydroxycinnamaldehyde as an antibacterial substance from the saw fly, Acantholyda parki S.
AbstractWe purified an antibacterial substance from larvae of the saw fly, Acantholyda parki S., and identified its molecular structure as p-hydroxycinnamaldehyde. We then synthesized it by reduction of p-hydroxycinnamic acid. The antibacterial activity of the synthetic p-hydroxycinnamaldehyde was equal to that of the authentic substance. This molecule was found to have a broad antibacterial spectrum against not only Gram-negative, but also Gram-positive bacteria. Furthermore, it showed antifungal activity against Candida albicans. We suggest that this substance may play a role in the defense system of this insect. This is the first report of p-hydroxycinnamaldehyde of animal origin
- …