Ab-initio density functional studies of stepped TaC surfaces

We report on density functional total energy calculations of the step formation and interaction energies for vicinal TaC(001) surfaces. Our calculations show that double and triple-height steps are favored over single-height steps for a given vicinal orientation, which is in agreement with recent experimental observations. We provide a description of steps in terms of atomic displacements and charge localization and predict an experimentally observable rumpled structure of the step-edges, where the Ta atoms undergo larger displacements compared to the C atoms.Comment: 4 pages, 4 figure

Topological defects in spinor condensates

We investigate the structure of topological defects in the ground states of spinor Bose-Einstein condensates with spin F=1 or F=2. The type and number of defects are determined by calculating the first and second homotopy groups of the order-parameter space. The order-parameter space is identified with a set of degenerate ground state spinors. Because the structure of the ground state depends on whether or not there is an external magnetic field applied to the system, defects are sensitive to the magnetic field. We study both cases and find that the defects in zero and non-zero field are different.Comment: 10 pages, 1 figure. Published versio

Intracoronary optical coherence tomography

The cardiovascular departments of the hospital of Holy Pope Giovanni XXIII in Bergamo, Italy and of the Institute of Cardiology in Chisinau, the Republic of Moldova have a fruitful history of collaboration in the field of interventional cardiology and intracoronary imaging in particular. We have recently expanded our collaboration by adding the method of Optical Coherence Tomography (OCT) into the armamentarium of imaging in the catheterization laboratory. OCT is an innovative, real time, tomographic imaging modality able to visualize tissues at microstructure level. It delivers the rays of near-infrared light through the wall of the coronary artery using small diameter optical fibres. The light that illuminates the vessel is absorbed and backscattered or reflected by the structures of the tissues with different degrees of density, thus creating an image with an axial resolution of 10-20 µm. This technology allows acquiring high definition images of long segments of coronaries for a few seconds. For the time being, OCT is mainly used in the researches, providing insights into the pathophysiology of the atherosclerotic plaque and the vascular response to stenting. It also has a potential for clinical application, such as pre-interventional evaluation of coronary arteries, procedures guidance and follow-up assessment of vascular healing after the stent implantation. A joined database has been created by the two institutions in an effort to study in vivo the morphology of the coronary arteries in different pathologies. This review is focused on the potential fields of application of OCT in different clinical and scientific institutions

In-stent restenosis in the drug eluting stent assayed by optical coherence tomography

Hospital of Holy Pope Giovanni XXIII, Bergamo, Italy, Department of Interventional Cardiology, Institute of Cardiology, Chisinau, the Republic of MoldovaBackground: In order to study the mechanisms and morphological aspects of the in-stent restenosis (ISR) have been evaluated restenosis lesions referred to drug eluting stent (DES) of the first generation using optical coherence tomography technique (OCT). Material and methods: The study underwent 39 patients with ISR induced recurrent angina or acute coronary syndrome including 66 stents from which were: 44 stents (28 patients) of the first generation of DES (19 – Cypher TM and 23 – Taxus®), and 22 stents (11 patients) of the second DES generation (9 Xience TM 2 Promus TM), 10 ZES (Resolute TM), and one stent Nobori TM. Has been made quantitative and morphological analysis of tissue pattern of ISR using the following OCT criteria: 1) morphologically homogenous neointima; 2)morphologically heterogeneous neointima; and 3) neoatherosclerosis. Results: It has been established that in the first generation of DES morphological homogenous pattern was present in both ISR developed after 1 year and later. However, the optical aspect with heterogeneous presentation had a prevalence decline in dynamics. The heterogeneous model had a higher prevalence in actual generation of DES in both incipient (< 1 year) and late presentation. Conclusions: The phenomenon of neoatherosclerosis has presented a significantly less frequency in the late restenosis of actual generation of DES. Our results suggest that restenosis phenomenon in actual generation of DES has a different morphological and evolution pattern in time in comparison with ISR of the first generation of DES

Ponderea letalității prin tuberculoza post-abandon

Institutul de Ftiziopneumologie “Chiril Draganiuc”Introducere. În ultimii 25 de ani incidenţa tuberculozei a crescut de la 49,2 la 114,5, iar mortalitatea prin tuberculoză de la 4,6 la 16,4 la 100 000 populaţie. Se consemnează creşterea şi numărului de non-aderenţă la tratamentul antituberculos, care adeseori devine una din cauzele principale ale progresării tuberculozei şi finalizării prin deces

Matter-Wave Solitons in an F=1 Spinor Bose-Einstein Condensate

Following our previous work [J. Ieda, T. Miyakawa, M. Wadati, cond-mat/0404569] on a novel integrable model describing soliton dynamics of an F=1 spinor Bose--Einstein condensate, we discuss in detail the properties of the multi-component system with spin-exchange interactions. The exact multiple bright soliton solutions are obtained for the system where the mean-field interaction is attractive (c_0 < 0) and the spin-exchange interaction is ferromagnetic (c_2 < 0). A complete classification of the one-soliton solution with respect to the spin states and an explicit formula of the two-soliton solution are presented. For solitons in polar state, there exists a variety of different shaped solutions including twin peaks. We show that a "singlet pair" density can be used to distinguish those energetically degenerate solitons. We also analyze collisional effects between solitons in the same or different spin state(s) by computing the asymptotic forms of their initial and final states. The result reveals that it is possible to manipulate the spin dynamics by controlling the parameters of colliding solitons.Comment: 12 pages, 9 figures, to appear in J. Phys. Soc. Jpn. Vol.73 No.11 (2004

Space charge in drift chambers operated with the Xe,CO2(15%) mixture

Using prototype modules of the ALICE Transition Radiation Detector we investigate space charge effects and the dependence of the pion rejection performance on the incident angle of the ionizing particle. The average pulse height distributions in the drift chambers operated with the Xe,CO2(15%) mixture provide quantitative information on the gas gain reduction due to space charge accumulating during the drift of the primary ionization. Our results demonstrate that the pion rejection performance of a TRD is better for tracks which are not at normal incidence to the anode wires. We present detailed simulations of detector signals, which reproduce the measurements and lend strong support to our interpretation of the measurements in terms of space charge effects.Comment: 18 pages, 10 figures, accepted for publication in Nucl.Instrum.Meth. A. Data files available at http://www-alice.gsi.de/tr

Energy loss of pions and electrons of 1 to 6 GeV/c in drift chambers operated with Xe,CO2(15%)

We present measurements of the energy loss of pions and electrons in drift chambers operated with a Xe,CO2(15%) mixture. The measurements are carried out for particle momenta from 1 to 6 GeV/c using prototype drift chambers for the ALICE TRD. Microscopic calculations are performed using input parameters calculated with GEANT3. These calculations reproduce well the measured average and most probable values for pions, but a higher Fermi plateau is required in order to reproduce our electron data. The widths of the measured distributions are smaller for data compared to the calculations. The electron/pion identification performance using the energy loss is also presented.Comment: 15 pages, 10 figures, accepted for publication in Nucl.Instrum.Meth.

Transition Radiation Spectroscopy with Prototypes of the ALICE TRD

We present measurements of the transition radiation (TR) spectrum produced in an irregular radiator at different electron momenta. The data are compared to simulations of TR from a regular radiator.Comment: 4 pages, 5 Figures, Proceedings for "TRDs for the 3rd millennium" (Sept. 4-7, 2003, Bari, Italy