Forward-backward equations for nonlinear propagation in axially-invariant optical systems

We present a novel general framework to deal with forward and backward components of the electromagnetic field in axially-invariant nonlinear optical systems, which include those having any type of linear or nonlinear transverse inhomogeneities. With a minimum amount of approximations, we obtain a system of two first-order equations for forward and backward components explicitly showing the nonlinear couplings among them. The modal approach used allows for an effective reduction of the dimensionality of the original problem from 3+1 (three spatial dimensions plus one time dimension) to 1+1 (one spatial dimension plus one frequency dimension). The new equations can be written in a spinor Dirac-like form, out of which conserved quantities can be calculated in an elegant manner. Finally, these new equations inherently incorporate spatio-temporal couplings, so that they can be easily particularized to deal with purely temporal or purely spatial effects. Nonlinear forward pulse propagation and non-paraxial evolution of spatial structures are analyzed as examples.Comment: 11 page

Lepton masses in a supersymmetric 3-3-1 model

We consider the mass generation for both charginos and neutralinos in a 3-3-1 supersymmetric model. We show that R-parity breaking interactions leave the electron and one of the neutrinos massless at the tree level. However the same interactions induce masses for these particles at the 1-loop level. Unlike the similar situation in the MSSM the masses of the neutralinos are related to the masses of the charginos.Comment: RevTex, 11 pages incluing 2 .eps figures. Extended published versio

Motivación hacia el cuidado del agua en población mexicana

Realizamos una adaptación de la Escala de Motivación hacia el Ambiente (Pelletier, Tuson, Green-Demers, Noels & Beaton, 1998), orientándola específicamente hacia el cuidado del agua. Por tal razón encuestamos a una muestra intencional de 350 estudiantes con edades entre 16 y 30 años pertenecientes a una universidad pública de la Ciudad de México. Mediante el empleo de un análisis factorial exploratorio obtuvimos dos dimensiones que denominamos como a) motivación autodeterminada y b) motivación no autodeterminada. Esta estructura bifactorial la ratificamos con el empleo de un análisis factorial confirmatorio, el cual evidenció índices de ajuste suficientes. Los hallazgos obtenidos nos sugieren que la muestra identifica sólo dos tipos de motivación en contraste con la evidencia especializada que reporta seis dimensiones en esta escala (e.g. Villacorta, Koestner & Lekes, 2003), por lo que se sugiere profundizar la línea de estudio respecto a los tipos de motivaciónWe carry out an adaptation of the Motivation Scale Toward the Environment (Pelletier, Tuson, Green-Demers, Noels & Beaton, 1998) guiding it specifically to water conservation. For such reason we apply a survey to an intentional sample of 350 students with ages between 16 and 30 years old belonging to a public university from Mexico City. By means of the employment of an exploratory factorial analysis we obtained two dimensions that were denominated like a) self-determined motivation and b) no self-determined motivation. We ratified this bifactorial structure with confirmatory factorial analysis, which evidenced enough fit indexes. The obtained results suggest us that the sample analyzed only identifies two motivation types in contrast with specialized evidence that reported six dimensions in this scale (e.g. Villacorta, Koestner & Lekes, 2003). Therefore we suggest to deepen the study line regarding the motivation type

ESTRATEGIA EDUCATIVA COMO EJE FUNDAMENTAL DEL CUIDADO ENFERMERO HACIA LA GESTANTE QUE VIVE EN CONDICIÓN DE VIH/SIDA, PARA LA PREVENCION DE LA TRANSMISIÓN VERTICAL

The increase in HIV / AIDS in females of childbearing age results in the vertical infection from mother to child and in turn, the incidence of HIV/AIDS in children. In this regard, prenatal or vertical transmission of HIV can occur during pregnancy, childbirth or through breast milk in breastfeeding. In this sense the objective is to design an action plan with educational strategies as key to nursing care of pregnant women living with HIV / AIDS, for prevention of vertical transmission of expectant mothers at the care center of La Morera, Juan German Roscio, Guarico (Venezuela). The methodology is part of a feasible project based on a descriptive field study, the population comprising of users attending the consultation of this center. The non-probability sample of the census included 20 expectant women who attended during the implementation period the data collection, which corresponded to a questionnaire of 30 dichotomous questions, and was validated by experts. The reliability obtained by Kuder Richarsond 20 was 0.89. The results determined that the patient had general knowledge of vertical transmission of HIV / AIDS, have limitations with respect to risk factors. In this sense, it was concluded that nursing care in obstetrics plays a very important role in detection, prevention and treatment of vertical transmission of HIV / AIDS in addition to the respective control that can receive guidance from the health team. That is the reason why having tools such as lesson plans, designed beforehand to offer the education they require.El incremento de VIH SIDA en la población femenina en edad fértil trae como consecuencia la infección vertical de la madre al hijo y a su vez la incidencia del VIH SIDA en la población infantil. En este sentido, la transmisión vertical o prenatal del VIH puede ocurrir durante el embarazo, el parto o por medio de la leche materna en el amamantamiento. En este sentido, se plantea como objetivo diseñar un plan de acción con estrategias educativas como eje fundamental del cuidado enfermero hacia la gestante que vive en condición de VIH/sida, para la prevención de la transmisión vertical dirigido a las mujeres embarazadas que asisten al centro de atención integral “La Morera”, Municipio Juan German Roscio, Guarico - Venezuela. La metodología utilizada se enmarcó en un proyecto factible fundamentado en un estudio de campo descriptivo, la población estuvo conformada por las usuarias que asisten a la consulta de dicho centro, la muestra de tipo no probabilística censal comprendió 20 gestantes que asistieron durante el período de aplicación del instrumento de recolección de datos, este último correspondió a un cuestionario de 30 preguntas dicotómicas, el cual fue validado por expertos y la confiabilidad obtenida a través de Kuder Richarsond 20, fue de 0,89. Los resultados determinan que las usuarias tenían conocimiento general acerca de la transmisión vertical del VIH/SIDA, teniendo limitaciones con respecto a los factores de riesgo; en este sentido, se concluye que el cuidado de enfermería en el área obstétrica juega un papel importantísimo en la detección, prevención y atención de la transmisión vertical del VIH SIDA, siendo, además del control respectivo, las orientaciones que puede recibir por parte del equipo de salud, de allí que cuente con herramientas como los planes de enseñanza, previamente diseñados para lograr llevar a cabo la educación que requieren

Multiple-Time Higher-Order Perturbation Analysis of the Regularized Long-Wavelength Equation

By considering the long-wave limit of the regularized long wave (RLW) equation, we study its multiple-time higher-order evolution equations. As a first result, the equations of the Korteweg-de Vries hierarchy are shown to play a crucial role in providing a secularity-free perturbation theory in the specific case of a solitary-wave solution. Then, as a consequence, we show that the related perturbative series can be summed and gives exactly the solitary-wave solution of the RLW equation. Finally, some comments and considerations are made on the N-soliton solution, as well as on the limitations of applicability of the multiple scale method in obtaining uniform perturbative series.Comment: 15 pages, RevTex, no figures (to appear in Phys. Rev. E

Neutrino masses through see-saw mechanism in 3-3-1 models

Some years ago it was shown by Ma that in the context of the electroweak standard model there are, at the tree level, only three ways to generate small neutrino masses by the see-saw mechanism via one effective dimension-five operator. Here we extend this approach to 3-3-1 chiral models showing that in this case there are several dimension-five operators and we also consider their tree level realization.Comment: RevTex, 7 pages and 4 .eps figures. Version published in Phys. Rev. D. with a change in the titl

Localized starbursts in dwarf galaxies produced by impact of low metallicity cosmic gas clouds

Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver of star formation over cosmic history. Except in very dense environments where galaxy mergers are also important, model galaxies feed from cold streams of gas from the web that penetrate their dark matter haloes. Although these predictions are unambiguous, the observational support has been indirect so far. Here we report spectroscopic evidence for this process in extremely metal-poor galaxies (XMPs) of the local Universe, taking the form of localized starbursts associated with gas having low metallicity. Detailed abundance analyses based on Gran Telescopio Canarias (GTC) optical spectra of ten XMPs show that the galaxy hosts have metallicities around 60 % solar on average, while the large star-forming regions that dominate their integrated light have low metallicities of some 6 % solar. Because gas mixes azimuthally in a rotation timescale (a few hundred Myr), the observed metallicity inhomogeneities are only possible if the metal-poor gas fell onto the disk recently. We analyze several possibilities for the origin of the metal-poor gas, favoring the metal-poor gas infall predicted by numerical models. If this interpretation is correct, XMPs trace the cosmic web gas in their surroundings, making them probes to examine its properties.Comment: Accepted for publication in ApJ