232 research outputs found
QUASI-2-DIMENSIONAL APPROACH TO STATES OF AN ADSORBED ATOM
No full textA method is developed for solving the Schrödinger equation to obtain the eigenfunctions (z,R) and eigenvalues of an adsorbed atom. By solving a one-dimensional equation for a given position R on the surface, one generates an effective potential (R) for the problem of lateral motion. The leading correction to this Born-Oppenheimer-like approach is expressed in analytic form. A numerical calculation for the case of He on graphite illustrates the simplicity and accuracy of the method. The mean distance of a ground-state He4 atom is found to agree with an experimental result of Carneiro, Passell, Thomlinson, and Tau
MODEL ADSORPTION POTENTIALS FOR HE AND NE ON GRAPHITE
No full textCalculations are presented concerning the adsorption of the atoms He and Ne on graphite. The ingredients of the potential are a repulsion obtained from the effective-medium theory, an anisotropic van der Waals dipolar attraction between atoms, and a quadrupole dispersion interaction. It is shown that alternative plausible models are compatible with experimental data obtained with atom and neutron scattering and adsorption isotherm
STRUCTURAL TRANSITION FOR POSITIVE IMPURITY IONS IN FLUIDS
No full textIt is suggested that the neighborhood of an alkaline-earth ion in a noble-gas fluid may undergo a structural transition as a function of applied pressure p0. For p0pc, a thin solid "crust" is present. The transition can be seen as a rapidly varying or discontinuous mobility at pc
Depletion of Superfluid Fraction In the Quasi-2-dimensional Bose-gas
No full textA theory is presented for the depletion of superfluid density in a low-temperature Bose gas adsorbed on a surface. Longitudinal excitations are treated in a Bogoliubov type of approximation. Transverse modes are found to contribute significantly if the excitation energy of adatoms normal to the surface is small
ENERGY OF IMMERSING A HE, NE, OR AR ATOM OR H-2 MOLECULE INTO A LOW-DENSITY ELECTRON-GAS
No full textWe calculate the energy E(n) required to immerse a noble-gas atom or H2 molecule into a low-density electron gas. The basic idea of Puska, Nieminen, and Manninen [Phys. Rev. B 24, 3037 (1981)] is modified by replacing the scattering length a with an effective length calculated by omitting polarization. The results are in good agreement with both ab initio and semiempirical results obtained by other methods
Analysis of full-text publication and publishing predictors of abstracts presented at an Italian public health meeting (2005-2007)
No full textBACKGROUND:
In Public Health, a thorough review of abstract quality evaluations and the publication history of studies presented at scientific meetings has never been conducted. To analyse the long-term outcome of quality abstracts submitted to conferences of Italian Society of Hygiene and Public Health (SItI) from 2005 to 2007, we conducted a second analysis of previously published material aiming to estimate full-text publication rate of high quality abstract presented at Italian public health meetings, and to identify predictors of full-text publication.
METHODS:
The search was undertaken through scientific databases and search engines and through the web sites of the major Italian journals of Public Health. For each publication confirmed as a full text paper, the journal name, impact factor, year of publication, gender of the first author, type of study design, characteristics of the results and sample size were collected.
RESULTS:
The overall publication rate of the abstracts presented is 23.5 %; most of the papers were published in Public Health journals (average impact factor: 3.007). Non universitary affiliation had resulted in a lower probability of publication, while some of the Conference topics had predisposed the studies to an increased likelihood of publication as well as poster form presentation.
CONCLUSIONS:
The method presented in this study provides a good framework for the evaluation of the scientific evidence. The findings achieved should be taken into consideration by the Scientific Societies during the contributions selection phase, with the aim of achieving a continuous improvement of work quality. In the future, it would be interesting to survey the abstract authors to identify reasons for unpublished data
Helium adsorption on a lithium substrate
No full textWe report results of path integral Monte Carlo and density functional studies of He-4 adsorption on a lithium substrate at low temperature. A recently proposed, accurate potential is used to model the He-4-substrate interaction. Results show evidence of continuous growth of a He-4 film, with a superfluid monolayer at low coverage and no well-defined layering at higher coverages. Estimated superfluid transition temperatures exhibit a coverage dependence similar to that found in recent experiments of Csathy et al
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