Una experiencia de aplicación de mapas conceptuales en la enseñanza de química física

En este trabajo se ha analizado de qué manera los alumnos de tercer curso de la ETSIM (UPM) elaboran mapas conceptuales en la enseñanza de la asignatura de Química Física. Antes de impartir el tema sobre corrosión los investigadores evaluaron los conocimientos previos de los estudiantes y los iniciaron en la construcción de los mapas conceptuales. Al final del curso los alumnos elaboraron un mapa conceptual. Los resultados obtenidos evidenciaron que la estrategia utilizada para iniciar a los alumnos en la construcción de mapas conceptuales fue eficiente, permitiéndoles aprender a trabajar con esta herramienta

3D short-range wetting and nonlocality

Analysis of a microscopic Landau-Ginzburg-Wilson model of 3D short-ranged wetting shows that correlation functions are characterized by two length scales, not one, as previously thought. This has a simple diagrammatic explanation using a nonlocal interfacial Hamiltonian and yields a thermodynamically consistent theory of wetting in keeping with exact sum rules. For critical wetting the second length serves to lower the cutoff in the spectrum of interfacial fluctuations determining the repulsion from the wall. We show how this corrects previous renormalization group predictions for fluctuation effects, based on local interfacial Hamiltonians. In particular, lowering the cutoff leads to a substantial reduction in the effective value of the wetting parameter and prevents the transition being driven first order. Quantitative comparison with Ising model simulation studies due to Binder, Landau, and co-workers is also mad

Immunological Features of the Non-Structural Proteins of Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is currently one of the most important viruses affecting the swine industry worldwide. Despite the large number of papers published each year, the participation of non-structural proteins (nsps) in the immune response is not completely clear. nsps have been involved in the host innate immune response, specifically, nsp1α/β, nsp2, nsp4 and nsp11 have been associated with the immunomodulation capability of the virus. To date, only participation by nsp1, nsp2, nsp4 and nsp7 in the humoral immune response has been reported, with the role of other nsps being overlooked. Furthermore, nsp1, nsp2, nsp5, nsp7 nsp9, nsp10, nsp11 have been implicated in the induction of IFN-γ and probably in the development of the cell-mediated immune response. This review discusses recent reports involving the participation of nsps in the modulation of the innate immune response and their role in the induction of both the humoral and cellular immune responses

Environmental Exposure of Arsenic in Groundwater Associated to Carcinogenic Risk in Underweight Children Exposed to Fluorides

Background: The purpose of this study was to determine the concentration of inorganic arsenic (As) in the potable water available to the population to be able to estimate the non-carcinogenic risks for underweight children and the carcinogenic risk for adults exposed to As intake who live in the Mezquital municipality, Durango, Mexico. Methods: The As content was quantifed in the water supply sources for human use and its intake was estimated in Mezquital population, southern Durango. With the data obtained, the hazard quotient (HQ) was calculated to determine the non-carcinogenic risk to develop chronic systemic effects in underweight children. The Environmental Protection Agency (EPA) reference health values estimating As exposure risk are from 0.0003 mg/kg/day (non-carcinogenic) to 1.5 mg/kg/day (carcinogenic risk). Results: The analyzed waters presented as concentrations that varied from 0.3 to 10.2 µg/L, with a mean of 7.35 µg/L (CI 95% 6.27-8.38). The exposure dose was 0.4 to 1.36, and the HQ was 1.90 to 6.48 mg/kg/day, the estimated carcinogenic risk from adults varied from 1.28 to 4.37E-4, with values of 3.74-4.37E-4 mg/kg/day in central area. Conclusions: The children are at risk to develop chronic systemic effects due to ingestion of As from water

Derivation of a Non-Local Interfacial Hamiltonian for Short-Ranged Wetting II: General Diagrammatic Structure

In our first paper, we showed how a non-local effective Hamiltionian for short-ranged wetting may be derived from an underlying Landau-Ginzburg-Wilson model. Here, we combine the Green's function method with standard perturbation theory to determine the general diagrammatic form of the binding potential functional beyond the double-parabola approximation for the Landau-Ginzburg-Wilson bulk potential. The main influence of cubic and quartic interactions is simply to alter the coefficients of the double parabola-like zig-zag diagrams and also to introduce curvature and tube-interaction corrections (also represented diagrammatically), which are of minor importance. Non-locality generates effective long-ranged many-body interfacial interactions due to the reflection of tube-like fluctuations from the wall. Alternative wall boundary conditions (with a surface field and enhancement) and the diagrammatic description of tricritical wetting are also discussed.Comment: (14 pages, 2 figures) Submitted J. Phys. Condens. Matte

Social Networks, a corporate strategy for the PyMES of the region of Guaymas Sonora Mexico

[ESP] Las Redes Sociales son una alternativa para las pequeñas y medianas empresas (PyMEs) de la región Guaymas-San Carlos, Sonora, México para conquistar mayor presencia en el mercado. El presente trabajo se planteó como objetivo conocer qué tanto estas organizaciones han utilizados las redes sociales y los beneficios que han logrado, así como proponer estrategias que mejoren su desempeño. En la metodología, el estudio se enfocó a las PyMEs del sector comercio y servicios. Se aplicó un cuestionario de 15 reactivos y de la información obtenida se realizaron los análisis con el programa estadístico SPSS. Los resultados mostraron que un gran porcentaje de los negocios no utilizan las redes sociales o no las aprovechan adecuadamente. Asimismo, se encontró que el medio de comunicación que más conocen y utilizan es el correo electrónico, cuyos beneficios son posicionar productos y servicios, tener un mayor contacto con los socios e incrementar las ventas, entre otros. [ENG] The Social Networks are an alternative for the small and medium companies (PyMEs) of the region Guaymas-San Carlos, Sonora, Mexico, to conquer major presence on the market. The present work´s target is to find out how much these organizations have used the social networks and the benefits that have achieved, as well as to propose strategies that improve their performance. In the methodology, the study focused on the PyMEs of the sector commerce and services. There was applied a questionnaire of 15 reagents and from the obtained information the analyses was made with the statistical program SPSS. The results showed that a big percentage of the business do not use the social networks or do not make use of them appropriately. Also, was found that the way of communication that they know and use the most is the e-mail, which benefits are to place products and services, to have a major contact with the associates and to increase the selling, among others

Differences of vegetation structure and diversity of a forest in an altitudinal gradient of the Sierra La Laguna Biosphere Reserve, Mexico

Abstract Background: The Sierra La Laguna Biosphere Reserve is located which is considered an “island of vegetation” within an arid environment. Considering that this protected natural area has an altitudinal gradient that ranges from 500 to 2,100 meters above sea level. Hypothesis: Higher altitudinal gradient decreases abundance, basal area and diversity of plant species. Studied species and data description: The data analyzed in this study included the structural variables of abundance (N ha-1), basal area (m2 ha-1) and diversity (alfa and beta) of arborous species in areas with different elevations. Study site and dates: This study was carried out in four localities of the tropical deciduous forest and broadleaved forest. In the spring of 2016. Methods: Five circular sampling plots of 500 m2 for arborous vegetation and 1m2 for herbaceous vegetation were established in every vegetation community, resulting in 20 sampling plots. Results: Sixteen families, 22 genera and 22 vascular plant species were recorded. The most diverse family was Fabacea with four species followed by Cactaceae with three species. The abundance, dominance and diversity of vegetation species did not show any decrease (or increase) tendency of values as the altitudinal gradient augmented. Conclusions: The hypothesis is rejected because abundance, dominance and diversity of vegetation species do not show any decrease or increase tendency as the altitudinal gradient augmented. The vegetation communities showed a high similarity in the composition of species. Key words: Altitudinal gradient, Baja California, diversity, species richness, vegetation structure. Resumen Antecedentes: La Reserva de la Biosfera Sierra la Laguna se encuentra en lo que es considerado una “isla de vegetación” dentro de un ambiente árido. Considerando que esta área natural protegida tiene un rango altitudinal que va desde los 500 a 2,100 metros sobre el nivel del mar. Hipótesis: A mayor gradiente altitudinal disminuye la abundancia, área basal y diversidad de las especies vegetales. Especies de estudio y descripción de datos: La información analizada en este estudio incluyó las variables estructurales de abundancia (N ha-1), el área basal (m2 ha-1) y diversidad (alfa y beta) de especies arbóreas en áreas con diferentes elevaciones. Sitio de estudio y año de estudio: Este estudio fue realizado en cuatro comunidades de selva baja caducifolia y bosque de latifoliadas. En la primavera de 2016. Métodos: Cinco parcelas circulares de 500 m2 para vegetación arbórea y 1m2 para vegetacion herbácea fueron establecidas en cada comunidad vegetal, resultado en 20 parcelas de muestreo. Resultados: Dieciséis familias, 22 géneros y 22 especies de plantas vasculares fueron registradas. La familia más diversa fue Fabacea con cuatro especies, seguido de Cactaceae con tres especies. La abundancia, dominancia y diversidad de especies vegetales no mostró una tendencia decreciente (o incremento) conforme el gradiente altitudinal aumentó. Conclusiones: La hipótesis fue rechazada debido a que la abundancia, dominancia y diversidad de especies vegetales no mostró ninguna tendencia decreciente (o incremento) en los valores conforme el gradiente altitudinal aumenta. Las comunidades vegetales mostraron una alta similitud en la composición de especies. Palabras clave: Baja California, diversidad, estructura vegetal, gradiente altitudinal, riqueza de especies

Fluoride exposure effects and dental fluorosis in children in Mexico City

BACKGROUND The objective of the present study was to determine the prevalence and severity of dental fluorosis and to evaluate exposure to fluoridated products in students in the southwest part of the Federal District (Mexico City). MATERIAL AND METHODS Students between 10 and 12 years of age who were born and raised in the study zone were evaluated. The level of dental fluorosis was determined using the modified Dean index (DI) using criteria recommended by the World Health Organization (WHO). A bivariate analysis was performed with the χ2 test, and odds ratios (OR) and 95% confidence intervals (CI) are presented. Logistic regression was performed to evaluate the association between dental fluorosis and the independent variables. RESULTS A total of 239 students were evaluated. Their mean age was 11±0.82 years, and there were 122 (51%) males. Overall, dental fluorosis was found in 59% of participants; 29.3% had very mild fluorosis, 20.9% had mild fluorosis, 6.7% had moderate fluorosis, and 2.1% had severe fluorosis. The mean fluorosis score was 0.887±0.956. In the final logistic regression model, dental fluorosis was significantly associated with frequency of brushing (OR: 0.444; 95% CI: 0.297-0.666) and with the absence of parental supervision (OR: 0.636; 95% CI: 0.525-0.771). CONCLUSIONS The association found with frequency of brushing and lack of parental supervision may be contributing to the prevalence and severity of dental fluorosis