Phase Transition effect on the Parametric Instability of Liquid Crystals

We review advances in the last few years on the study of the Faraday instability onset on thermotropic liquid crystals of nematic and smectic A types under external magnetic fields which have been investigated with a linear stability theory. Especially, we show that thermal phase transition effects on nematics of finite thickness samples produce an enhanced response to the instability as a function of the frequency of Shaker’s movement. The linear stability theory has successfully been used before to study dynamical processes on surfaces of complex fluids. Consequently, in Section 1, we show its extension to the study of the instability in the nematics, which set the theoretical framework for its further application to smectics or other anisotropic fluids such as lyotropic liquid crystals. We present the dispersion relationships of both liquids and its dependence on interfacial elastic parameters governing the surface elastic responses to external perturbations, to the sample size and their bulk viscosities. Finally, we point out the importance of following both experimental and theoretical analysis of various effects that needs to be incorporated into this model for the quantitative understanding of the hydrodynamics behavior of surface phenomena in liquid crystals

Emotion Regulation Strategies on Depression through a Problematic Use of Technology: Toward an Explanation of the Association between Depressive Symptomatology and Internet Addiction

Depression has been reliably associated in the past with uncontrolled use of the Internet regardless of its consequences, a phenomenon commonly referred to as Internet addiction. However, less attention has been afforded to explaining this association. The present study aims to provide a potential explanation based on current theoretical accounts of emotion regulation and the problematic use of the Internet. To achieve this goal, this dissertation comprises three articles. The first discusses a transcultural adaptation of the most psychometrically evaluated measure of Internet addiction and a test of its psychometric properties on an adult sample from Chile. Next, using a sample of Chilean high school students, a cross-sectional test of two potential mechanisms linking depressive symptomatology and Internet addiction investigates the possibility of being cognitively absorbed on the Internet (referred to as flow experiences online) and using the Internet to postpone unpleasant tasks (referred to as Internet procrastination). The final article analyzed data from the follow-up measurements of the adolescent sample to provide a longitudinal explanation of the association between depressive symptomatology and Internet addiction for those using the Internet to disconnect from life situations, that is, using the Internet as a proxy for an attentional deployment emotion regulation strategy. Taken together, results suggest that the inflexible use of the Internet to regulate emotional experiences may influence the development of Internet addiction based on a negative affective state such as the presence of depressive symptomatology. A possible vicious circle is theoretically discussed, together with the study limitations and potential implications for both clinical practice and future research efforts. It is hoped that the present study sheds light on the mechanisms linking the technologically mediated context with adolescent affective processes

Scale dependent three-dimensional charged black holes in linear and non-linear electrodynamics

In the present work we study the scale dependence at the level of the effective action of charged black holes in Einstein-Maxwell as well as in Einstein-power-Maxwell theories in (2+1)-dimensional spacetimes without a cosmological constant. We allow for scale dependence of the gravitational and electromagnetic couplings, and we solve the corresponding generalized field equations imposing the "null energy condition". Certain properties, such as horizon structure and thermodynamics, are discussed in detail.Comment: v1: 13 pages, 10 figure

From feminist epistemologies to decolonial feminism: Contributions to studies about migrations

Este artículo parte con el análisis de tres enfoques que han cuestionado el pensamiento científico convencional: las epistemologías feministas, la teoría decolonial y los feminismos decoloniales; luego, se integran las fortalezas de estos marcos con el fin de generar una propuesta epistemológica para los estudios de género y migración. Dicha propuesta —basada en tres ejes— desarticula los fundamentos androcéntricos y sexistas de las ciencias, así como las tramas eurocéntricas y colonialistas que se han plasmado en los estudios de género, apostando por una perspectiva investigativa que aborde las interseccionalidades que vivencian las mujeres en el marco de las experiencias sociales de género y migración desde una mirada dialógica, que entendemos debe ser impronta del quehacer científico.This paper start with the analusis of three approaches that have challenged conventional scientific thinking: feminist epistemologies, decolonial theory and decolonial feminism; then, the strengths of these frameworks are integrated in order to generate an epistemological proposal for gender and migration studies. This proposal —based on three axes— dismantles the androcentric and sexist foundations of science as well as eurocentric and colonialist arguments reflected in gender studies, betting on a research perspective that addresses the intersectionalities that women experience in the Framework of the social experiences of gender and migration from a dialogical view, which we understand must be imprint of the scientific work

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

In this chapter, we review the experimental and theoretical modeling of structural and dynamical properties of colloidal magnetic fluids at equilibrium. Presently, several prototype experimental systems are very well characterized. We survey the different models, which help to reach a comprehensive knowledge of these complex magnetic fluids. One prime example is the ongoing investigation of the realistic interparticle potentials that drive the formation of the different phase states observed experimentally. Further, a stochastic equation approach for the description of tracer diffusion, viscoelasticity, and dielectric relaxation at equilibrium in colloidal ferrofluids is discussed

Violencia de género: prevalencia, imaginarios sexistas, y mitos en la juventud universitaria

The aim of this study is to identify aspects related to gender-based violence at Chilean universities, with a focus on three areas of analysis: the prevalence of violence against women in heterosexual relationships; the persistence of traditional gender constructs; and the reproduction of myths about this form of abuse, as well as the sexist imaginaries present in the student’s experiences. Theoretical support is drawn from feminist analyses that have examined the power structures in which these aggressions survive and reproduce, as well as the social dynamics that naturalize them. Studies have found that higher education is neither a protective factor against violence nor a tool that dismantles the gender imaginary that supports it. At a methodological level, 1,120 surveys were administered at three Chilean universities, encompassing the three aforementioned areas of analysis. The results point to the continuing prevalence of violence against women, as well as the endurance of myths and sexist imaginary that invisibilize the reproduction of gender power relations. The discussion and conclusions highlight the role of education and higher education institutions in driving changes in this area.Se presenta una investigación cuyo objetivo fue analizar aspectos relacionados con la violencia de género en el contexto universitario chileno abordando tres ejes en particular: prevalencia de violencia contra las mujeres en relaciones de pareja heterosexuales, pervivencia de constructos tradicionales de género, reproducción de mitos sobre este maltrato, así como imaginarios sexistas presentes en el estudiantado. El sustento teórico viene dado por los enfoques feministas que han examinado las estructuras de poder en las que permanecen y se reproducen estas agresiones, así como las dinámicas sociales que las naturalizan. Los estudios en el área destacan que la educación superior no es necesariamente un factor protector ante la violencia ni una herramienta que, de por sí, desmonte los imaginarios de género que le dan soporte. A nivel metodológico, se aplicaron 1.120 encuestas en tres universidades chilenas, en las que se abordaron los tres ejes de análisis ya señalados. Los resultados muestran un elevado porcentaje de violencia contra las mujeres y, a la vez, evidencian la subsistencia de mitos e imaginarios sexistas que invisibilizan la reproducción de este tipo de relaciones de poder. En la discusión y conclusiones, se releva el papel de la educación y de las instituciones de educación superior a la hora de promover cambios en este ámbito

Biodiversity and coffee culture in Mexico

Coffee is grown in agro-ecosystems designed by humans in tropical rain forests. Under diversified shade coffee retains much of the structure and functioning of forest ecosystems. After cereals, coffee is the agricultural product moving major currencies in international markets. It is produced in 50 countries by indigenous and peasants. In order to evaluate the coffee culture of central Veracruz region in Mexico, coffee production systems were studied and social organization manners were identified. The project had a transdisciplinary design. The network consists of 100 scholars, 10 organizations of producers and 109 companies in 52 municipalities. In four years (2010-2013), 254 meetings were held with the participation of 6,400 persons. Each activity was thought looking at farmers, their business project and its own culture.El café se produce en agro-ecosistemas diseñados por los seres humanos, a partir de bosques tropicales húmedos. El cafetal bajo la sombra conserva una gran parte de la estructura y funcionamiento de los ecosistemas boscosos. Después de los cereales, el café es el producto agrícola que mayores divisas mueve en el mercado internacional. Se produce en 50 países, principalmente por indígenas y campesinos. Con el objeto de valorar la cultura cafetalera del centro de Veracruz en México, se estudiaron los sistemas de producción de café y se identificaron las formas de organización social. El proyecto ha tenido un diseño transdisciplinario. La red de este estudio está formada por 100 académicos, 10 organizaciones de productores y 109 empresas en 52 municipios. En cuatro años (2010-2013) se realizaron 254 eventos con 6.400 participaciones. Cada actividad se realizó teniendo en cuenta a los productores, su proyecto de empresa y su cultura