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Search Results: 1 - 10 of 168683 matches for " E. Cuevas "
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Critical spectral statistics in two-dimensional interacting disordered systems
E. Cuevas
Physics , 1998, DOI: 10.1103/PhysRevLett.83.140
Abstract: The effect of Coulomb and short-range interactions on the spectral properties of two-dimensional disordered systems with two spinless fermions is investigated by numerical scaling techniques. The size independent universality of the critical nearest level-spacing distribution $P(s)$ allows one to find a delocalization transition at a critical disorder $W_{\rm c}$ for any non-zero value of the interaction strength. At the critical point the spacings distribution has a small-$s$ behavior $P_c(s)\propto s$, and a Poisson-like decay at large spacings.
$f(α)$ Multifractal spectrum at strong and weak disorder
E. Cuevas
Physics , 2002, DOI: 10.1103/PhysRevB.68.024206
Abstract: The system size dependence of the multifractal spectrum $f(\alpha)$ and its singularity strength $\alpha$ is investigated numerically. We focus on one-dimensional (1D) and 2D disordered systems with long-range random hopping amplitudes in both the strong and the weak disorder regime. At the macroscopic limit, it is shown that $f(\alpha)$ is parabolic in the weak disorder regime. In the case of strong disorder, on the other hand, $f(\alpha)$ strongly deviates from parabolicity. Within our numerical uncertainties it has been found that all corrections to the parabolic form vanish at some finite value of the coupling strength.
Critical generalized inverse participation ratio distributions
E. Cuevas
Physics , 2002, DOI: 10.1103/PhysRevB.66.233103
Abstract: The system size dependence of the fluctuations in generalized inverse participation ratios (IPR's) $I_{\alpha}(q)$ at criticality is investigated numerically. The variances of the IPR logarithms are found to be scale-invariant at the macroscopic limit. The finite size corrections to the variances decay algebraically with nontrivial exponents, which depend on the Hamiltonian symmetry and the dimensionality. The large-$q$ dependence of the asymptotic values of the variances behaves as $q^2$ according to theoretical estimates. These results ensure the self-averaging of the corresponding generalized dimensions.
Two-level correlation function of critical random-matrix ensembles
E. Cuevas
Physics , 2004, DOI: 10.1103/PhysRevB.71.024205
Abstract: The two-level correlation function $R_{d,\beta}(s)$ of $d$-dimensional disordered models ($d=1$, 2, and 3) with long-range random-hopping amplitudes is investigated numerically at criticality. We focus on models with orthogonal ($\beta=1$) or unitary ($\beta=2$) symmetry in the strong ($b^d \ll 1$) coupling regime, where the parameter $b^{-d}$ plays the role of the coupling constant of the model. It is found that $R_{d,\beta}(s)$ is of the form $R_{d,\beta}(s)=1+\delta(s)-F_{\beta}(s^{\beta}/b^{d\beta})$, where $F_{1}(x)=\text{erfc}(a_{d,\beta} x)$ and $F_{2}(x)=\exp (-a_{d,\beta} x^2)$, with $a_{d,\beta}$ being a numerical coefficient depending on the dimensionality and the universality class. Finally, the level number variance and the spectral compressibility are also considerded.
Critical level spacing distribution in long-range hopping Hamiltonians
E. Cuevas
Physics , 2003, DOI: 10.1209/epl/i2004-10048-2
Abstract: The nearest level spacing distribution $P_c(s)$ of $d$-dimensional disordered models ($d=1$ and 2) with long-range random hopping amplitudes is investigated numerically at criticality. We focus on both the weak ($b^d \gg 1$) and the strong ($b^d \ll 1$) coupling regime, where the parameter $b^{-d}$ plays the role of the coupling constant of the model. It is found that $P_c(s)$ has the asymptotic form $P_c(s)\sim\exp [-A_ds^{\alpha}]$ for $s\gg 1$, with the critical exponent $\alpha=2-a_d/b^d$ in the weak coupling limit and $\alpha=1+c_d b^d$ in the case of strong coupling.
Critical properties in long-range hopping Hamiltonians
E. Cuevas
Physics , 2004, DOI: 10.1002/pssb.200404783
Abstract: Some properties of $d$-dimensional disordered models with long-range random hopping amplitudes are investigated numerically at criticality. We concentrate on the correlation dimension $d_2$ (for $d=2$) and the nearest level spacing distribution $P_c(s)$ (for $d=3$) in both the weak ($b^d \gg 1$) and the strong ($b^d \ll 1$) coupling regime, where the parameter $b^{-d}$ plays the role of the coupling constant of the model. It is found that (i) the extrapolated values of $d_2$ are of the form $d_2=c_db^d$ in the strong coupling limit and $d_2=d-a_d/b^d$ in the case of weak coupling, and (ii) $P_ (s)$ has the asymptotic form $P_c(s)\sim\exp (-A_ds^{\alpha})$ for $s\gg $, with the critical exponent $\alpha=2-a_d/b^d$ for $b^d \gg 1$ and $\alpha=1+c_d b^d$ for $b^d \ll 1$. In these cases the numerical coefficients $A_d$, $a_d$ and $c_d$ depend only on the dimensionality.
Multifractality of Hamiltonians with power-law transfer terms
E. Cuevas
Physics , 2003, DOI: 10.1103/PhysRevB.68.184206
Abstract: Finite-size effects in the generalized fractal dimensions $d_q$ are investigated numerically. We concentrate on a one-dimensional disordered model with long-range random hopping amplitudes in both the strong- and the weak-coupling regime. At the macroscopic limit, a linear dependence of $d_q$ on $q$ is found in both regimes for values of $q \alt 4g^{-1}$, where $g$ is the coupling constant of the model.
Estrategia y resultados de la farmacovigilancia de vacunas desde el Instituto Finlay, 2009
Cuevas,Iván E;
Vaccimonitor , 2010,
Abstract: this paper aims at showing the strategy and the results of pharmacosurveillance at finlay institute, as owner of sanitary medical registries. the biography of products was consolidated in post-marketing stage and risk/benefit balance was examined. in our case, the spontaneous notification of adverse events and the compliance with good practices and rules/regulations of the regulatory authority was possible due to agreements with institutions that allowed the access to digital and auditable data bases. data-mining search of the grouping of rare and unexpected events for a same lot or accidents, the preparation of periodic safety reports and the systematic practice to fill requested information on subpopulations and special groups, allowed updating the safety profile of vaccines. it was confirmed that the frequency of adverse events of trivalent leptospirosis vaccine, the typhoid vi vaccine and tetanus toxoid, was lower than 0.1 report per every 100 000 vaccinees, while the other vaccines showed values from 0.1 to 1 per 100 000 vaccinees. from 80% to 95% of the notifications were causally related to the vaccine, and only 0.89% was of serious severity, almost all of it in children younger than one year. general manifestations were predominant. results showed the pertinence of industry pharmacosurveillance to obtain valuable safety information on vaccine administration.
Presente y futuro de la farmacovigilancia en la Industria Farmacéutica
Cuevas,Iván E;
Vaccimonitor , 2007,
Abstract: a study about problems of post-commercialization surveillance in the pharmaceutical industry was carried out. adverse reactions to medicines and vaccines cause a significant increase in the costs of sanitary assistance; vaccines in particular have a deferred and unknown benefit and an immediate risk. this is the reason why higher surveillance standards are required. pharmaco-surveillance by itself presents obstacles which can be greater when they are focused on from the pharmaceutical industry. company or sponsorship as strategy allows overcoming these obstacles and establishing the post-commercialization surveillance system which has been systematic practice of finlay institute. the experience of our institute where all factors and conditions influencing on products are observed is an advance to obtain a better evaluation of the sanitary and economic impact on the application of our vaccines. implementation and starting of pharmaco-surveillance in the medicine industry is a challenge and a necessity to complete the development of the pharmaceutical industry.
Typhoid fever: a re-emerging disease
Ivan E. Cuevas Valdespino
Medwave , 2011,
Abstract:
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