High resolution scanning tunneling spectroscopy of ultrathin Pb on Si(111)-(6x6) substrate

The electronic structure of Si(111)-(6x6)Au surface covered with submonolayer amount of Pb is investigated using scanning tunneling spectroscopy. Already in small islands of Pb with thickness of 1 ML Pb$_{(111)}$ and with the diameter of only about 2 nm we detected the quantized electronic state with energy 0.55 eV below the Fermi level. Similarly, the I(V) characteristics made for the Si(111)-(6x6)Au surface reveal a localized energy state 0.3 eV below the Fermi level. These energies result from fitting of the theoretical curves to the experimental data. The calculations are based on tight binding Hubbard model. The theoretical calculations clearly show prominent modification of the I(V) curve due to variation of electronic and topographic properties of the STM tip apex.Comment: 7 pages, 7 figures, accepted for publication in Surface Scienc

Scanning tunneling microscopy of monoatomic gold chains on vicinal Si(335) surface: experimental and theoretical study

We study electronic and topographic properties of the Si(335) surface, containing Au wires parallel to the steps. We use scanning tunneling microscopy (STM) supplemented by reflection of high energy electron diffraction (RHEED) technique. The STM data show the space and voltage dependent oscillations of the distance between STM tip and the surface which can be explained within one band tight binding Hubbard model. We calculate the STM current using nonequilibrium Keldysh Green function formalism.Comment: 6 pages, 4 figure

Prestige of Psychologists in Britain, the USA & Israel

This article compares the status and income of psychologists in Britain with those of the U.S.A. and Israel

Polarization Effects in γP Gravitational Scattering with Applications to Dark Matter

Using a simple perturbative approach to quantum gravity, we consider gravitational scattering of high-energy, polarized photons on a massive scalar target. We find that due to the exchange of virtual gravitons, there is a non-trivial polarization dependence in the photon scattering behavior, not previously considered in the literature. Our results are considered in analogy with scattering in quantum electrodynamics. We find that the polarization dependence in a gravitational field is extremely weak relative to electromagnetic effects. A variety of possible experimental parameters were considered in order to isolate the quantum gravity effects. Using Monte-Carlo methods, this work models the gravitational scattering of galactic photons in the Dark Matter Halo of the Milky Way. The likelihood of detecting these scattered photons on Earth is then calculated, along with the degree of gravity-induced polarization. Detection of this polarization would provide convincing evidence of the quantum effects of gravity and indirect proof of graviton exchange. Our results indicate that Dark Matter can be thought as polarizing, even in scalar models where Dark Matter only interacts gravitationally. Results also suggest a new method of bounding the mass of the Dark Matter particle from above. Dark Matter was chosen as the scattering target to mitigate interfering non-gravitational effects. We also briefly discuss polarization effects of photon-scalar scattering as an entanglement breaking channel for maximally entangled photons produced by pair annihilation, which is a fascinating avenue for future research

Tight binding description of the STM image of molecular chains

A tight binding model for scanning tunneling microscopy images of a molecule adsorbed on a metal surface is described. The model is similar in spirit to that used to analyze conduction along molecular wires connecting two metal leads and makes it possible to relate these two measurements and the information that may be gleaned from the corresponding results. In particular, the dependence of molecular conduction properties along and across a molecular chain on the chain length, intersite electronic coupling strength and on thermal and disorder effects are discussed and contrasted. It is noted that structural or chemical defects that may affect drastically the conduction along a molecular chain have a relatively modest influence on conduction across the molecular wire in the transversal direction.Comment: 22 pages, 9 figures, Israel J Chemistry, in pres

Age-related cognitive effects of ECT and ECT-induced mood improvement in depressive patients

This explorative study investigated the interaction between electroconvulsive therapy (ECT) treatment-effect, reduced depression, and neuropsychological outcome in relation to age. Follow-up neuropsychological assessment was conducted with depressive patients treated with ECT. From a potential sample of 45 patients, the neuropsychological measures (pre-ECT, three times post-ECT, up to 12 months) and clinical data from the remaining 21 patients who completed all assessments were evaluated (mean age = 56.76; SD = 14.12; range, 33-79). ECT resulted in a decrease in the depression scores. A distinct impact of ECT and depression decrease on cognitive domains was found. Depression alleviation was mainly associated with improvement in cognitive domains such as memory, information processing, and executive function. ECT improved cognitive domains such as information processing and perception. Short-term cognitive improvement was greater in older patients but showed an increase similar to that at long-term follow-up in younger patients (<60). Current findings provide evidence that ECT may improve cognitive functioning in nondemented elderly, which has strong clinical relevance concerning the Use of ECT. © 2006 Wiley-Liss, Inc

Recall and recognition in mildly disturbed schizophrenics: the use of matched tasks

SynopsisUnlike previous studies, this study shows that in controlled conditions non-chronic schizophrenics receiving neuroleptic medication show no disparity between recall and recognition. Patients receiving both neuroleptic and anticholinergic drugs show this disparity, performing less well on recall than on recognition. These patients also seem more severely disturbed. The importance of task matching, drugs and chronicity are discussed.</jats:p