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Search Results: 1 - 10 of 325164 matches for " S. Malvezzi "
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K-matrix and Dalitz plot analysis from FOCUS
S. Malvezzi
Physics , 2007,
Abstract: Dalitz analysis is a powerful tool for physics studies within and beyond the Standard Model. In the last decade it has helped to investigate the Heavy Flavor hadronic decay dynamics and is now being applied to extract angles of the CKM Unitarity triangle. To perform such sophisticate analyses we need to model the strong interaction effects. The FOCUS experiment has performed pilot studies in the charm sector through the K-matrix formalism. What has been learnt from charm will be beneficial for future accurate beauty measurements. Experience and results from FOCUS are presented and discussed.
Influence of Nearest-Neighbor Coulomb Interactions on the Phase Diagram of the Ferromagnetic Kondo Model
A. L. Malvezzi,S. Yunoki,E. Dagotto
Physics , 1998, DOI: 10.1103/PhysRevB.59.7033
Abstract: The influence of a nearest-neighbor Coulomb repulsion of strength V on the properties of the Ferromagnetic Kondo model is analyzed using computational techniques. The Hamiltonian studied here is defined on a chain using localized S=1/2 spins, and one orbital per site. Special emphasis is given to the influence of the Coulomb repulsion on the regions of phase separation recently discovered in this family of models, as well as on the double-exchange-induced ferromagnetic ground state. When phase separation dominates at V=0, the Coulomb interaction breaks the large domains of the two competing phases into small ``islands'' of one phase embedded into the other. This is in agreement with several experimental results, as discussed in the text. Vestiges of the original phase separation regime are found in the spin structure-factor as incommensurate peaks, even at large values of V. In the ferromagnetic regime close to density $n=0.5$, the Coulomb interaction induces tendencies to charge ordering without altering the fully polarized character of the state. This regime of ``charge- ordered ferromagnetism'' may be related with experimental observations of a similar phase by C. H. Chen and S-W. Cheong (Phys. Rev. Lett. 76, 4042 (1996)). Our results reinforce the recently introduction notion (see e.g., S. Yunoki et al., Phys. Rev. Lett. 80, 845 (1998)) that in realistic models for manganites analyzed with unbiased many-body techniques, the ground state properties arise from a competition between ferromagnetism and phase-separation/charge-ordering tendencies.
Analysis of Substructures in Charm Decays
Sandra Malvezzi
Physics , 1996,
Abstract: Recent results on Dalitz analysis of three-pseudoscalar decays are discussed in the context of probing charm hadronic-decay mechanisms: the role of FSI effects, which create phase shifts between the interfering resonant channels, can be studied in the different decay modes and the annihilation contribution measured in the charm sector through the $D^+_s \to \pi^+\pi^-\pi^+$ decay.
Tetracritical behaviour in a spin-3/2 quantum chain
A. Malvezzi
Physics , 1994,
Abstract: Finite-Size-Scaling and Conformal Invariance are used in order to find the phase diagram and critical exponents of a quantum spin chain with spin $S=3/2$. The model has a tetracritical point besides critical lines. The conformal anomaly and anomalous dimensions of some primary operators are calculated at the tetracritical point.
Charm lifetime
Sandra Malvezzi
Physics , 1995, DOI: 10.1007/BF02731706
Abstract: A review of the charmed meson and baryon lifetimes is presented. Our knowledge of charmed particle lifetimes has greatly improved over the past two years, a crucial r\^ole having been played by the E687 experiment at Fermilab, which has almost quadrupled the samples of $D$ mesons. The lifetime ratios $\tau(D^+)/\tau(D^0)$ and $\tau(D_s^+)/\tau(D^0)$ are now known with an accuracy of 1.7\% and 3.7\% respectively. In the baryon sector the statistics is still limited, but the experimental results on $\Lambda_c^+$, $\Xi_c^0$ and $\Xi_c^+$ exhibit a clear pattern of lifetime hierarchy, as expected from simple theoretical arguments. The first measurement of $\tau(\Omega_c^0)$ from E687 is also presented to complete the charmed baryon lifetime picture. The more accurate experimental scenario can provide information on non-perturbative QCD effects and the hadronic matrix elements.
Light quark and charm interplay in the Dalitz-plot analysis of hadronic decays in FOCUS
Sandra Malvezzi
Physics , 2003, DOI: 10.1016/S0920-5632(03)02334-X
Abstract: The potentiality of interpreting the D-meson decay-dynamics has revealed itself to be strongly dependent on our understanding of the light-meson sector. The statistics collected by FOCUS is already at a level that manifests parametrization problems for scalar particles. In this paper the first application of the K-matrix approach in the charm sector is illustrated and preliminary results on the D+ and Ds decays to three pions are shown.
Status and prospects of charm physics: a few considerations
Sandra Malvezzi
Physics , 2004,
Abstract: Progress in charm physics has been prodigious over the last twenty years; it comes both from fixed target and collider experiments, and can guide us toward future investigations. To fully exploit the power of flavor physics, complications coming from strong dynamics effects have to be dealt with. The role of charm in the search for New Physics, the lessons learnt so far and warnings for the future are briefly discussed.
Effect of L-arginine, dimercaptosuccinic acid (DMSA) and the association of L-arginine and DMSA on tissue lead mobilization and blood pressure level in plumbism
Malvezzi, C.K.;Moreira, E.G.;Vassilieff, I.;Vassilieff, V.S.;Cordellini, S.;
Brazilian Journal of Medical and Biological Research , 2001, DOI: 10.1590/S0100-879X2001001000016
Abstract: lead (pb)-induced hypertension is characterized by an increase in reactive oxygen species (ros) and a decrease in nitric oxide (no). in the present study we evaluated the effect of l-arginine (no precursor), dimercaptosuccinic acid (dmsa, a chelating agent and ros scavenger), and the association of l-arginine/dmsa on tissue pb mobilization and blood pressure levels in plumbism. tissue pb levels and blood pressure evolution were evaluated in rats exposed to: 1) pb (750 ppm, in drinking water, for 70 days), 2) pb plus water for 30 more days, 3) pb plus dmsa (50 mg kg-1 day-1, po), l-arginine (0.6%, in drinking water), and the combination of l-arginine/dmsa for 30 more days, and 4) their respective matching controls. pb exposure increased pb levels in the blood, liver, femur, kidney and aorta. pb levels in tissues decreased after cessation of pb administration, except in the aorta. these levels did not reach those observed in nonintoxicated rats. all treatments mobilized pb from the kidney, femur and liver. pb mobilization from the aorta was only effective with the l-arginine/dmsa treatment. blood pb concentrations in pb-treated groups were not different from those of the pb/water group. pb increased blood pressure starting from the 5th week. l-arginine and dmsa treatments (4th week) and the combination of l-arginine/dmsa (3rd and 4th weeks) decreased blood pressure levels of intoxicated rats. these levels did not reach those of nonintoxicated rats. treatment with l-arginine/dmsa was more effective than the isolated treatments in mobilizing pb from tissues and in reducing the blood pressure of intoxicated rats.
Effect of L-arginine, dimercaptosuccinic acid (DMSA) and the association of L-arginine and DMSA on tissue lead mobilization and blood pressure level in plumbism
Malvezzi C.K.,Moreira E.G.,Vassilieff I.,Vassilieff V.S.
Brazilian Journal of Medical and Biological Research , 2001,
Abstract: Lead (Pb)-induced hypertension is characterized by an increase in reactive oxygen species (ROS) and a decrease in nitric oxide (NO). In the present study we evaluated the effect of L-arginine (NO precursor), dimercaptosuccinic acid (DMSA, a chelating agent and ROS scavenger), and the association of L-arginine/DMSA on tissue Pb mobilization and blood pressure levels in plumbism. Tissue Pb levels and blood pressure evolution were evaluated in rats exposed to: 1) Pb (750 ppm, in drinking water, for 70 days), 2) Pb plus water for 30 more days, 3) Pb plus DMSA (50 mg kg-1 day-1, po), L-arginine (0.6%, in drinking water), and the combination of L-arginine/DMSA for 30 more days, and 4) their respective matching controls. Pb exposure increased Pb levels in the blood, liver, femur, kidney and aorta. Pb levels in tissues decreased after cessation of Pb administration, except in the aorta. These levels did not reach those observed in nonintoxicated rats. All treatments mobilized Pb from the kidney, femur and liver. Pb mobilization from the aorta was only effective with the L-arginine/DMSA treatment. Blood Pb concentrations in Pb-treated groups were not different from those of the Pb/water group. Pb increased blood pressure starting from the 5th week. L-arginine and DMSA treatments (4th week) and the combination of L-arginine/DMSA (3rd and 4th weeks) decreased blood pressure levels of intoxicated rats. These levels did not reach those of nonintoxicated rats. Treatment with L-arginine/DMSA was more effective than the isolated treatments in mobilizing Pb from tissues and in reducing the blood pressure of intoxicated rats.
Magnetic Susceptibility of an integrable anisotropic spin ladder system
A. P. Tonel,S. R. Dahmen,A. Foerster,A. L. Malvezzi
Physics , 2003, DOI: 10.1209/epl/i2003-00144-3
Abstract: We investigate the thermodynamics of a spin ladder model which possesses a free parameter besides the rung and leg couplings. The model is exactly solved by the Bethe Ansatz and exhibits a phase transition between a gapped and a gapless spin excitation spectrum. The magnetic susceptibility is obtained numerically and its dependence on the anisotropy parameter is determined. A connection with the compounds KCuCl3, Cu2(C5H12N2)2Cl4 and (C5H12N)2CuBr4 in the strong coupling regime is made and our results for the magnetic susceptibility fit the experimental data remarkably well.
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