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Trejo-Valdez M.,National Polytechnic Institute of Mexico | Torres-Martinez R.,Research Center en Ciencia Aplicada | Perea-Lopez N.,Laboratory for Nanoscience and Nanotechnology Research LINAN | Santiago-Jacinto P.,National Autonomous University of Mexico | Torres-Torres C.,Seccion de Estudios de Posgrado e Investigacion
Journal of Physical Chemistry C | Year: 2010

We measured the absorptive and refractive nonlinearities in Au nanoparticles when they are embedded in a TiO2 film and when they are suspended in ethanol. The morphology of the nanoparticles was estimated by using HRTEM microscopy. Different contributions related to electronic polarization and two-photon absorption were observed in the samples using a self-diffraction technique with pulses of 26 ps at 532 nm. Transmittance experiments were performed in order to confirm the mechanisms of optical absorption. The Au nanoparticles were grown by the photoreduction of TiO 2 sol-gel solutions which contain Au3+ ions. The thin films were prepared by using the dip coating technique with fresh UV exposed sol-gel solutions. We observed that when the sample does not present any important nonlinear absorption it is possible to enhance the participation of the nanoparticles in the optical Kerr response of the media. © 2010 American Chemical Society. Source

Fernandez-Garcia N.,Seccion de Estudios de Posgrado e Investigacion | Hernandez E.,National Autonomous University of Mexico | Jauregui A.,University of Sonora | Mondragon A.,National Autonomous University of Mexico
Journal of Physics A: Mathematical and Theoretical | Year: 2013

In this paper, we present and discuss an example of exceptional points in the continuous spectrum of a Hamiltonian of von Neumann-Wigner type associated with a double pole in the normalized Jost eigenfunctions, as functions of the wave number. The two unnormalized Jost energy eigenfunctions are analytic functions of the wave number k for all k complex, but at the exceptional points k = ±q, they coalesce to give rise to Jordan cycles of two generalized bound state quadratically integrable eigenfunctions. The Green function has simple poles at the exceptional points, but the regular scattering eigenfunction vanishes at those points. The scattering matrix is a regular function of the wave number at the exceptional points, that is, S(k) does not have a pole at the exceptional points. © 2013 IOP Publishing Ltd. Source

Velazquez-Roman J.A.,Seccion de Estudios de Posgrado e Investigacion
Clinical and experimental hypertension (New York, N.Y. : 1993) | Year: 2011

Both gestation and diabetes mellitus (DM) are conditions associated with an increased participation of renin-angiotensin system (RAS) as well as with changes in the vascular response to angiotensin II (Ang II). We sought to establish the impact of gestational diabetes mellitus (GDM) on Ang II- induced vasoconstriction and its correlation with the expression of angiotensin II receptors (AT(1)R, AT(2) R). Female Wistar rats, virgin, or on day 3 after mating, received randomly streptozotocin (STZ) 60 mg/kgor saline ip.Streptozotocin-treated animals developed hyperglycemia (25.6 ± 1.42 mM). Ang II-induced vasoconstriction was evaluated on isolated aortas with (e+) and without (e-) endothelium and the protein expression of AT(1)R and AT(2)R was measured by western blot. Gestational diabetes mellitus significantly increased vasoconstriction with respect to all the other groups. Changes were observed only on e+ vessels. Interestingly, GDM moved AT(1)R: AT(2)R balance towards AT(1) R, while both pregnancy and diabetes towards AT(2)R expression. In conclusion, GDM increases the possibility of an hypertensive complication by an increased AT(1)R expression. Source

Perez-Cruz J.H.,University of Guadalajara | Ruiz-Velazquez E.,University of Guadalajara | De Jesus Rubio J.,Seccion de Estudios de Posgrado e Investigacion | De Alba-Padilla C.A.,University of Guadalajara
Mathematical Problems in Engineering | Year: 2012

In this study, the problem of controlling an unknown SISO nonlinear system in Brunovsky canonical form with unknown deadzone input in such a way that the system output follows a specified bounded reference trajectory is considered. Based on universal approximation property of the neural networks, two schemes are proposed to handle this problem. The first scheme utilizes a smooth adaptive inverse of the deadzone. By means of Lyapunov analyses, the exponential convergence of the tracking error to a bounded zone is proven. The second scheme considers the deadzone as a combination of a linear term and a disturbance-like term. Thus, the estimation of the deadzone inverse is not required. By using a Lyapunov-like analyses, the asymptotic converge of the tracking error to a bounded zone is demonstrated. Since this control strategy requires the knowledge of a bound for an uncertainty/disturbance term, a procedure to find such bound is provided. In both schemes, the boundedness of all closed-loop signals is guaranteed. A numerical experiment shows that a satisfactory performance can be obtained by using any of the two proposed controllers. © 2012 J. Humberto Pérez-Cruz et al. Source

Resendiz L.,Seccion de Estudios de Posgrado e Investigacion | Estrada M.,CINVESTAV | Cerdeira A.,CINVESTAV | Iniguez B.,Rovira i Virgili University | Deen M.J.,McMaster University
Organic Electronics: physics, materials, applications | Year: 2010

In this paper, we analyze the variation of the threshold voltage V T and carrier mobility μfet with the active layer thickness of polymer thin film transistors (PTFTs). The value of VT was observed to become more negative as the active layer thickness decrease, while mobility slightly increased. Simulations obtained for different active layer thickness were first validated with experimental data from measured devices with known active layer thickness. Then using the calibrated simulator, it was found that as the semiconductor thickness decreased, the charge per square units in the active layer changes, establishing the cause of both of these behaviors. © 2010 Elsevier B.V. All rights reserved. Source

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