Puebla de Zaragoza, Mexico
Puebla de Zaragoza, Mexico
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Avendano C.G.,Madero University | Reyes J.A.,National Autonomous University of Mexico
Optics Communications | Year: 2010

We consider a nonlinear cylindrical fiber with a nematic liquid crystal (LC) core having initially the escaped configuration and subject to the action of a normal mode propagating electromagnetic field of arbitrary intensity. We derive a set of coupled equations governing the nonlinear dynamics of the electromagnetic field and the confined LC. We solve numerically these coupled equations and find simultaneously the distorted textures of the nematic inside the cylinder and the Transverse Magnetic modes in the guide. We analyze the dependence of these solutions on the electromagnetic field intensity by assuming consistently soft boundary conditions. We have found a dramatic correlation in the spatial distribution of the nematic's configuration and the Transverse Magnetic modes. Thus, the director adopts configurations completely guided by the specific mode involved. We show that the cut-off frequencies and dispersion relations can be tuned by varying the intensity of the electromagnetic propagating field. © 2010 Elsevier B.V. All rights reserved.

Martinez-Vazquez M.A.,Madero University | Vazquez-Elizondo G.,Madero University | Gonzalez-Gonzalez J.A.,Madero University | Gutierrez-Udave R.,Madero University | And 2 more authors.
Revista de Gastroenterologia de Mexico | Year: 2012

Introduction: Irritable bowel syndrome (IBS) is characterized by recurrent abdominal pain, bloating, and changes in bowel habit. Aims: To determine the clinical effectiveness of the antispasmodic agents available in Mexico for the treatment of IBS. Methods: We carried out a systematic review and meta-analysis of randomized controlled clinical trials on antispasmodic agents for IBS treatment. Clinical trials identified from January 1960 to May 2011 were searched for in MEDLINE, the Cochrane Library, and in the Clinical-Trials.gov registry. Treatment response was evaluated by global improvement of symptoms or abdominal pain, abdominal distention/bloating, and frequency of adverse events. The effect of antispasmodics vs placebo was expressed in OR and 95% CI. Results: Twenty-seven studies were identified, 23 of which fulfilled inclusion criteria. The studied agents were pinaverium bromide, mebeverine, otilonium, trimebutine, alverine, hyoscine, alverine/simethicone, pinaverium/simethicone, fenoverine, and dicyclomine. A total of 2585 patients were included in the meta-analysis. Global improvement was 1.55 (CI 95%: 1.33 to 1.83). Otilonium and the alverine/simethicone combination produced significant values in global improvement while the pinaverium/simethicone combination showed improvement in bloating. As for pain, 2394 patients were included with an OR of 1.52 (IC 95%: 1.28 a 1.80), favoring antispasmodics. Conclusions: Antispasmodics were more effective than placebo in IBS, without any significant adverse events. The addition of simethicone improved the properties of the antispasmodic agents, as seen with the alverine/simethicone and pinaverium/simethicone combinations. © 2011 Asociación Mexicana de Gastroenterología.

Salazar-Ramirez M.,National Polytechnic Institute of Mexico | Martiinez D.,Madero University | Mota R.D.,National Polytechnic Institute of Mexico | Granados V.D.,National Polytechnic Institute of Mexico
Journal of Physics A: Mathematical and Theoretical | Year: 2010

We apply the Schrödinger factorization method to the radial second-order equation for the relativistic Kepler-Coulomb problem. From these operators we construct two sets of one-variable radial operators which are realizations for the su(1, 1) Lie algebra. We use this algebraic structure to obtain the energy spectrum and the supersymmetric ground state for this system. © 2010 IOP Publishing Ltd.

Avendano C.G.,Madero University | Martinez D.,Madero University
Applied Optics | Year: 2014

We present the tunability of the omnidirectional band gap (OBG) in a one-dimensional photonic structure consisting of N nematic liquid-crystal slabs in a twisted configuration. It is alternated by N isotropic dielectric layers by a dc electric field aligned along the periodicity axis. We consider the general case for which arbitrary anchoring of the nematic at the boundaries is taken into account. The threshold electric field for which the OBG is created decreases as the anchoring strength diminishes. The width of this band gets larger as the electric field increases and its center frequency is modified slightly. © 2014 Optical Society of America.

Avendano C.G.,Madero University | Reyes J.A.,National Autonomous University of Mexico
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The multiplet structure of the optical defect modes generated within the bandgap are analyzed by a finite number of identical equispaced twist defects in axially elongated cholesteric elastomers. It is shown that n 0 defect modes induced by n 0 twist defects can be mechanically tuned. The transfer matrix is obtained and the defect frequencies when n 0=1,2 are expressed in terms of twist angle, fractional shape anisotropy, and longitudinal deformation. For n 0=2, the coupling between modes is analytically studied and it is shown that when the separation between defects is much larger than the line width, the defect modes do not interact and become degenerated. © 2012 American Physical Society.

Avendano C.G.,Madero University | Reyes J.A.,National Autonomous University of Mexico
Optics Communications | Year: 2014

We consider a one-dimensional nonlinear photonic crystal consisting of an infinite set of concentrated equidistant scatterers inserted in a linear dielectric medium. Each of the scatterers is made by a very thin layer of a nonlinear medium with high refractive index that we model by a delta function. We show that the nonlinear optical exact solutions of this system form an intensity dependent band structure. To analyze the stability of these solutions we consider a modulation harmonic perturbation of these solutions whose amplitudes are slightly above the instability threshold. We demonstrate that the nonlinearity gives rise to an oscillatory instability of the solutions, which is a localized version of the well-known modulational instability of the nonlinear Schrodinger equation. We show that the linear harmonic perturbation forms as well a band structure whose allowed bands coincide for some intervals with those of the nonlinear band structure of the solutions for which case the structures are unstable whereas in the region where both the linear and nonlinear bands do not coincide, the nonlinear waves are indeed stable so that they conform spatial solitons. © 2014 Elsevier B.V.

Sevilla F.J.,National Autonomous University of Mexico | Olivares-Quiroz L.,Madero University
European Journal of Physics | Year: 2012

In this work, we address the concept of the chemical potential μ in classical and quantum gases towards the calculation of the equation of state μ = μ(n, T) where n is the particle density and T the absolute temperature using the methods of equilibrium statistical mechanics. Two cases seldom discussed in elementary textbooks are presented with detailed calculations. The first one refers to the explicit calculation of μ for the interacting classical gas exemplified by van der Waals gas. For this purpose, we used the method described by van Kampen (1961 Physica 27 783). The second one refers to the calculation of μ for ideal quantum gases that obey a generalized Pauli's exclusion principle that leads to statistics that go beyond the BoseEinstein and FermiDirac cases. The audience targeted in this work corresponds mainly to advanced undergraduates and graduate students in the physicalchemical sciences but it is not restricted to them. In regard of this, we have put a special emphasis on showing some additional details of calculations that usually do not appear explicitly in textbooks. © 2012 IOP Publishing Ltd.

Salazar-Ramirez M.,National Polytechnic Institute of Mexico | Martinez D.,Madero University | Granados V.D.,National Polytechnic Institute of Mexico | Mota R.D.,National Polytechnic Institute of Mexico
International Journal of Theoretical Physics | Year: 2010

We apply the Schrödinger factorization to construct the generators of the dynamical algebra su(1,1) for the radial equation of the generalized MICZ-Kepler problem. © Springer Science+Business Media, LLC 2010.

Martinez D.,Madero University | Avendano C.G.,Madero University
European Journal of Physics | Year: 2014

We evaluate the Feynman propagator for the harmonic oscillator in one dimension. Considering the ladder operators for the Hamiltonian of this system, we construct a set of operators which satisfy the su(2) Lie algebra to obtain Mehler's formula. © 2014 IOP Publishing Ltd.

Cortes-Gonzalez J.R.,Madero University | Arratia-Maqueo J.A.,Madero University | Gomez-Guerra L.S.,Madero University | Holmberg A.R.,Urologic
BJU International | Year: 2010

Objective To evaluate the effect of an extract of Butea superba (Roxb.) (BS) compared to sildenafil for treating erectile dysfunction (ED). Patients and methods An open label study was carried out among 32 men with organic ED to evaluate the response on the International Index of Erectile Function 5 (IIEF-5) to BS, a 'natural health' product (100 mg), compared to 50 mg of sildenafil (a phosphodiesterase-5 inhibitor). After a 1-week wash-out, responders to BS received either 100 mg starch or 100 mg of another batch of BS (double-blind). Results Of the patients in the BS group, 27 (84%) responded positively, compared with 26 (81%) in the sildenafil group. When assessing the score alone, 12 (38%) had a better score after taking BS, compared to seven (22%) after sildenafil, and eight (25%) had the same score. The results were surprising and could not be repeated in the double-blind part of the study, where no effect of BS was recorded. CONCLUSIONS A 'natural' health product containing BS was more effective than sildenafil in the first part of the study, but in the second, using another batch of BS, the positive result could not be repeated and no effect was recorded. The conclusion is that the first preparation of BS was most likely blended with a phosphodiesterase-5 inhibitor, later confirmed by the supplier of BS (a natural health products company) after their own analysis. © 2009 BJU International.

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