Anderson Localization Phenomenon in One-dimensional Elastic Systems

The phenomenon of Anderson localization of waves in elastic systems is studied. We analyze this phenomenon in two different set of systems: disordered linear chains of harmonic oscillators and disordered rods which oscillate with torsional waves. The first set is analyzed numerically whereas the second one is studied both experimentally and theoretically. In particular, we discuss the localization properties of the waves as a function of the frequency. In doing that we have used the inverse participation ratio, which is related to the localization length. We find that the normal modes localize exponentially according to Anderson theory. In the elastic systems, the localization length decreases with frequency. This behavior is in contrast with what happens in analogous quantum mechanical systems, for which the localization length grows with energy. This difference is explained by means of the properties of the re ection coefficient of a single scatterer in each case.Comment: 15 pages, 10 figure

A Verilog-A Based Fractional Frequency Synthesizer Model for Fast and Accurate Noise Assessment

This paper presents a new strategy to simulate fractional frequency synthesizer behavioral models with better performance and reduced simulation time. The models are described in Verilog-A with accurate phase noise predictions and they are based on a time jitter to power spectral density transformation of the principal noise sources in a synthesizer. The results of a fractional frequency synthesizer simulation is compared with state of the art Verilog-A descriptions showing a reduction of nearly 20 times. In addition, experimental results of a fractional frequency synthesizer are compared to the simulation results to validate the proposed model

Estudi computacional de les interaccions moleculars entre l'àcid itacònic i compostos antimalàrics: un pas important per al disseny racional de sistemes d'alliberament controlat de fàrmacs

Las interacciones moleculares entre cuatro antimaláricos: cloroquina, primaquina, quinina y amodiaquina, con un dímero del ácido itacónico, fueron estudiadas a través de la teoría del funcional de la densidad usando B3LYP/++6-31G(d,p) y el modelo CPCM para el solvente. Cloroquina, primaquina y quinina presentan interacción apreciable con el dímero del ácido itacónico, con energías de interacción en el rango de -17 hasta -6,7 kcal/mol, de naturaleza exotérmica, a través de un proceso de fisisorción. El valor positivo de la energía de interacción para la amodiaquina sugiere una menor probabilidad de que este sea adsorbido por un dímero de ácido itacónico. Los cálculos NBO y la aplicación de la teoría de perturbación de segundo orden indican transferencia de carga desde los compuestos cloroquina y primaquina. Adicionalmente, los resultados sugieren que las interacciones principales son de naturaleza polar, donde los enlaces de hidrógenos juegan un rol principal. Los resultados encontrados a través del método CPCM indican que los complejos entre el dímero de ácido itacónico con cloroquina y primaquina son bastante estables en disolución acuosa; además presentan valores adecuados de LogP y momento dipolar, indicando alta la interacción con el solvente que permitiría el hinchamiento y la liberación controlada de estos fármacos.The molecular interactions between four widely used antimalaric i.e, chloroquine, primaquine, quinine and amodiaquine, with an itaconic acid dimer as a hydrogel model, have been studied by the mean of the Density Functional Theory calculation in both, vacuum and water environment, using B3LYP/++6-31G(d,p) basis set and PCM model of solvent. Chloroquine, primaquine, and quinine show a suitable interaction with the itaconic acid dimer, with binding energy into the range of -17 to -6.7 kcal/ mol. These values of binding energies suggest the formation of stable and exothermic complexes in the range of physisorption energy. By contrast, the positive value of binding energy for amodiaquine indicates a little chance to be absorbed into the hydrogel polymer. The NBO calculation and the second order perturbation theory indicate a strong charge-transference from chloroquine and primaquine to itaconic acid dimer. In addition, these results suppose the interactions are mainly polar in nature where the hydrogen bond plays a pivotal role in complex stabilization. On the other hand, the CPCM calculations suggest the chloroquine and primaquine complex are stables, with suitable values of both, LogP and dipole momentum implying the swelling of these complex in water and the eventual drugs controlled-delivery from the polymeric matrix

Enhanced suppresion of localization in a continuous Random-Dimer Model

We consider a one-dimensional continuous (Kronig-Penney) extension of the (tight-binding) Random Dimer model of Dunlap et al. [Phys. Rev. Lett. 65, 88 (1990)]. We predict that the continuous model has infinitely many resonances (zeroes of the reflection coefficient) giving rise to extended states instead of the one resonance arising in the discrete version. We present exact, transfer-matrix numerical calculations supporting, both realizationwise and on the average, the conclusion that the model has a very large number of extended states.Comment: 10 pages, 3 Figures available on request, REVTeX 3.0, MA/UC3M/1/9

Discovery of the broad-lined Type Ic SN 2013cq associated with the very energetic GRB 130427A

Long-duration gamma-ray bursts (GRBs) at z < 1 are in most cases found to be accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The highest-energy GRBs are mostly located at higher redshifts, where the associated SNe are hard to detect observationally. Here we present early and late observations of the optical counterpart of the very energetic GRB 130427A. Despite its moderate redshift z = 0.3399+/-0.0002, GRB 130427A is at the high end of the GRB energy distribution, with an isotropic-equivalent energy release of Eiso ~ 9.6x10^53 erg, more than an order of magnitude more energetic than other GRBs with spectroscopically confirmed SNe. In our dense photometric monitoring, we detect excess flux in the host-subtracted r-band light curve, consistent with what expected from an emerging SN, ~0.2 mag fainter than the prototypical SN 1998bw. A spectrum obtained around the time of the SN peak (16.7 days after the GRB) reveals broad undulations typical of SNe Ic-BL, confirming the presence of a SN, designated SN 2013cq. The spectral shape and early peak time are similar to those of the high expansion velocity SN 2010bh associated with GRB 100316D. Our findings demonstrate that high-energy long-duration GRBs, commonly detected at high redshift, can also be associated with SNe Ic-BL, pointing to a common progenitor mechanism.Comment: 12 pages, 4 figures, 1 table, accepted for publication in Ap