Physical mechanisms and scaling laws of K-shell double photoionization

We report on the photon energy dependence of the K-shell double photoionization (DPI) of Mg, Al, and Si. The DPI cross sections were derived from high-resolution measurements of x-ray spectra following the radiative decay of the K-shell double vacancy states. Our data evince the relative importance of the final-state electron-electron interaction to the DPI. By comparing the double-to-single K-shell photoionization cross-section ratios for neutral atoms with convergent close-coupling calculations for He-like ions, the effect of outer shell electrons on the K-shell DPI process is assessed. Universal scaling of the DPI cross sections with the effective nuclear charge for neutral atoms is revealed

Double K-shell photoionization of low-Z atoms and He-like ions

We report on the investigation of the photon energy dependence of double 1s photoionization of light atoms and compare the cross sections for hollow atom and He-like ion production. Measurements of the Kα hypersatellite x-ray spectra of Mg, Al, and Si were carried out using the Fribourg high-resolution x-ray spectrometer installed at the ID21 and ID26 beam lines at the ESRF. The double-to-single photoionization cross section ratios were derived as a function of the incident photon beam energy and compared to convergent close-coupling (CCC) calculations for He-like ions. The dynamical electron-electron scattering contribution to the DPI cross-sections was found to be more important for neutral atoms than for the He isoelectronic serie

El resum: més del mateix

Abstract not availabl

FAUNE ET FLORE DES NIVEAUX PROFONDS DE SHAHI-TUMP (BALOCHISTAN, PAKISTAN) Premiers résultats

International audienceÀ Shahi-Tump, site fouillé par la Mission archéologique française au Makran (district de Kech-Makran, Balochistan pakistanais), les niveaux les plus anciens appartiennent à un faciès néolithique acéramique. Pourtant, les premiers résultats des analyses des restes archéozoologiques et archéobotaniques indiquent une séquence culturelle qui correspond à la phase ultime précédant l'introduction de la céramique dans cette région occidentale du Balochistan. L'exploitation du milieu naturel y est de faible importance et l'économie alimentaire repose fondamentalement sur des espèces animales et végétales domestiques-mais dont le spectre est encore limité. Un tel modèle est rare dans la vaste région comprise entre l'Iran oriental et l'Indus. Le seul site ayant livré des faunes et des fl ores domestiquées associées à des niveaux sans céramique est le site de Merhgarh. Ce dernier appartient cependant à une zone biogéographique très différente du Makran, et le rôle des animaux sauvages pour l'obtention de protéines d'origine animale y est très important, alors qu'il n'a joué qu'un rôle mineur dans l'économie de Shahi-Tump. La rareté de tels horizons dans toute cette région nous a paru justifi er la diffusion des points originaux concernant l'économie alimentaire de ce site avant la publication d'autres données-tout particulièrement la métrique-qui seront présentées dans le cadre de la future monographie consacrée aux restes de ce gisement. Abstract: At Shahi-Tump, a site excavated by the French Archaeological Mission to Makran (district of Kech-Makran, Baluchistan, Pakistan), the oldest occupational levels belong to an aceramic neolithic horizon. The fi rst results obtained by the analysis of archaeozoological and archaeobotanical remains suggest nevertheless that we deal here with a phase immediately preceding the introduction of ceramics into this western part of Baluchistan. The exploitation of wild resources was of minor importance and the subsistence economy seems to have been mainly based on a limited number of domestic animal and plant species. This model is uncommon in the vast region stretching from eastern Iran to the Indus. The only other site that has provided remains of domestic animals and plants associated with aceramic neolithic levels is Mehrgarh. However, at this site, situated in a quite different biogeographical zone, wild animals constituted a signifi cant part of the diet, while hunting never played an important role in the subsistence economy at Shahi-Tump. The rarity of aceramic deposits across this region justifi es the publication of the fi rst results from Shahi-Tump even though this paper does not contain detailed information, most particularly morphometric data. These will be presented at length in a future monograph dedicated to the site. Mots-clés : Archéozoologie, Archéobotanique, Shahi-Tump, Makran, Néolithique acéramique, Paléo-environnement

Front-end electronics for the ALICE TPC-detector

The Front-End electronics for the Time Projection Chamber (TPC) for the ALICE experiment consists of 5x105 channels. A single readout channel is comprised of three basic units: a charge sensitive amplifier/shaper with a fast tail cancellation; a 10 bit 10 Msamples/sec low power ADC; a digital ASIC which contains the zero suppression circuit and a multiple-event buffer. Data from a number of channels (4096) are multiplexed into an optical link (DDL) by means of a local custom bus which can support a data throughput of 2 Mbyte/event at a trigger rate of 50 Hz. The construction of a prototype of this electronics is presented in this paper

Relativistic nature of a magnetoelectric modulus of Cr_2O_3-crystals: a new 4-dimensional pseudoscalar and its measurement

Earlier, the magnetoelectric effect of chromium sesquioxide Cr_2O_3 has been determined experimentally as a function of temperature. One measures the electric field-induced magnetization on Cr_2O_3 crystals or the magnetic field-induced polarization. From the magnetoelectric moduli of Cr_2O_3 we extract a 4-dimensional relativistic invariant pseudoscalar $\widetilde{\alpha}$. It is temperature dependent and of the order of 10^{-4}/Z_0, with Z_0 as vacuum impedance. We show that the new pseudoscalar is odd under parity transformation and odd under time inversion. Moreover, $\widetilde{\alpha}$ is for Cr_2O_3 what Tellegen's gyrator is for two port theory, the axion field for axion electrodynamics, and the PEMC (perfect electromagnetic conductor) for electrical engineering.Comment: Revtex, 36 pages, 9 figures (submitted in low resolution, better quality figures are available from the authors

Punica granatum (Pomegranate) juice provides an HIV-1 entry inhibitor and candidate topical microbicide

BACKGROUND: For ≈ 24 years the AIDS pandemic has claimed ≈ 30 million lives, causing ≈ 14,000 new HIV-1 infections daily worldwide in 2003. About 80% of infections occur by heterosexual transmission. In the absence of vaccines, topical microbicides, expected to block virus transmission, offer hope for controlling the pandemic. Antiretroviral chemotherapeutics have decreased AIDS mortality in industrialized countries, but only minimally in developing countries. To prevent an analogous dichotomy, microbicides should be: acceptable; accessible; affordable; and accelerative in transition from development to marketing. Already marketed pharmaceutical excipients or foods, with established safety records and adequate anti-HIV-1 activity, may provide this option. METHODS: Fruit juices were screened for inhibitory activity against HIV-1 IIIB using CD4 and CXCR4 as cell receptors. The best juice was tested for inhibition of: (1) infection by HIV-1 BaL, utilizing CCR5 as the cellular coreceptor; and (2) binding of gp120 IIIB and gp120 BaL, respectively, to CXCR4 and CCR5. To remove most colored juice components, the adsorption of the effective ingredient(s) to dispersible excipients and other foods was investigated. A selected complex was assayed for inhibition of infection by primary HIV-1 isolates. RESULTS: HIV-1 entry inhibitors from pomegranate juice adsorb onto corn starch. The resulting complex blocks virus binding to CD4 and CXCR4/CCR5 and inhibits infection by primary virus clades A to G and group O. CONCLUSION: These results suggest the possibility of producing an anti-HIV-1 microbicide from inexpensive, widely available sources, whose safety has been established throughout centuries, provided that its quality is adequately standardized and monitored

Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method

This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1$ of the true values and the fractional energy resolution is $[(58\pm3)/\sqrt{E}+(2.5\pm0.3)$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM

Hypersatellite x-ray decay of 3d3d hollow-KK-shell atoms produced by heavy-ion impact

We report on the radiative decay of double K-shell vacancy states produced in solid Ca, V, Fe, and Cu targets by impact with about 10 MeV/amu C and Ne ions. The resulting K hypersatellite x-ray emission spectra were measured by means of high- energy-resolution spectroscopy using a von Hamos bent crystal spectrometer. The experiment was carried out at the Philips variable energy cyclotron of the Paul Scherrer Institute. From the fits of the x-ray spectra the energies, line widths, and relative intensities of the hypersatellite x-ray lines could be determined. The fitted intensities were corrected to account for the energy-dependent solid angle of the spectrometer, effective source size, target self-absorption, crystal reflectivity, and detector efficiency. The single-to-double K-shell ionization cross-section ratios were deduced from the corrected relative intensities of the hypersatellites and compared to theoretical predictions from the semiclassical approximation model using hydrogenlike and Dirac-Hartree-Fock wave functions and from classical trajectory Monte Carlo calculations