998 resultados para transforming edge


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Adecuado como guía de lectura compartida o independiente tiene diferentes tipos de texto para distintos niveles de comprensión lectora. Muestra cómo algunos pueblos hacen frente a las condiciones ambientales extremas en que viven y trabajan. De qué forma obtienen los alimentos y el agua,y que no solo aprenden del pasado sino también prueban nuevas tecnologías y nuevos materiales. Hay un mapa con datos sobre la densidad de población en los distintos continentes.

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Aborda una de las preguntas más difíciles de nuestro tiempo, pues su único punto de vista se basa en el reconocimiento de que la interdisciplinariedad eficaz y coherente es necesaria para afrontar la cuestión del cambio climático y la multitud de fenómenos vinculados y conectados a él. Solo si se utiliza un enfoque general para dar sentido intelectual a los fenómenos complejos sobre la cuestión del cambio climático, se pueden ofrecer respuestas.

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Libro dirigido a profesores y cursos de métodos de alfabetización. Propone un modelo para la enseñanza de la alfabetización crítica con ejemplos y prácticas que pueden realizarse en el día a día de la escuela primaria o secundaria. Los materiales que presenta permiten a los estudiantes utilizar el lenguaje para cuestionar el mundo en su vida diaria, investigar la relación entre lenguaje y poder, analizar la cultura popular, entender cómo las relaciones fuertes están construidas socialmente, y considerar las acciones a realizar para conseguir una justicia social.

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Las preguntas por los métodos en ciencias sociales parecen responderse con facilidad en los manuales, el simple ejercicio de definir el enfoque que utilizaremos (cuantitativo o cualitativo) supone la apertura a la claridad. En este sentido los cuestionamientos acerca de qué es lo que vamos a estudiar, por cuánto tiempo, quiénes conformarán nuestra muestra, cómo abordaremos a los sujetos de estudio, qué tipo de preguntas, encuestas o modalidades de conversación grupales aplicaremos, de qué modo validaremos nuestros resultados y tantas otras preguntas, aparecen como estrategias y técnicas metodológicas con simulaciones contextuales que en muchos aspectos aclaran los tecnicismos, pero que no agotan las múltiples críticas y preguntas que dichos métodos también presentan. En los métodos de manual, particularmente la etnografía, las estrategias aparecen unas seguidas de otras como una multiplicidad de opciones a la mano que podemos elegir según el imaginario que hemos proyectado inicialmente. Siguiendo las pautas tendemos a olvidar que los sujetos de estudio son personas hombres y mujeres que piensan, accionan y reaccionan de distintos modos afectando las metodologías y estrategias seleccionadas, de tal modo que el manual debe ser siempre el repertorio de opciones posibles de modificarse, nunca la guía final de nuestros estudios. Estos cuestionamientos acompañaron muchos de mis procesos y experiencias con los métodos de campo, a partir de los cuales presentaré algunos aspectos que me parece interesante exponer.

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Extensive fragmentation of the sagebrush shrubsteppe of western North America could be contributing to observed population declines of songbirds in sagebrush habitat. We examined whether habitat fragmentation impacts the reproduction of songbirds in sagebrush edge habitat near agriculture, and if potential impacts vary depending on the adjacent crop type. Specifically, we evaluated whether nest abundance and nest survival varied between orchard edge habitat, vineyard edge habitat, and interior habitat. We then examined whether the local nest predator community and vegetation could explain the differences detected. We detected fewer nests in edge than interior habitat. Nest abundance per songbird was also lower in edge than interior habitat, although only adjacent to vineyards. Nest predation was more frequent in orchard edge habitat than vineyard edge or interior habitat. Predators identified with nest cameras were primarily snakes, however, reduced nest survival in orchard edge habitat was not explained by differences in the abundance of snakes or any other predator species identified. Information theoretic analysis of daily survival rates showed that greater study plot shrub cover and lower grass height at nests were partially responsible for the lower rate of predation-specific daily nest survival rate (PDSR) observed in orchard edge habitat, but additional factors are likely important. Results of this study suggest that different crop types have different edge effects on songbirds nesting in sagebrush shrubsteppe, and that these reproductive edge effects may contribute to observed declines of these species. Habitat managers should avoid the creation of new orchard-sagebrush habitat edges to avoid further impacts on already declining songbird populations.

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Nitric oxide regulates many important cellular processes including motility and invasion. Many of its effects are mediated through the modification of specific cysteine residues in target proteins, a process called S-nitrosylation. Here we show that S-nitrosylation of proteins occurs at the leading edge of migrating trophoblasts and can be attributed to the specific enrichment of inducible nitric oxide synthase (iNOS/NOS2) in this region. Localisation of iNOS to the leading edge is co-incidental with a site of extensive actin polymerisation and is only observed in actively migrating cells. In contrast endothelial nitric oxide synthase (eNOS/NOS3) shows distribution that is distinct and non-colocalised with iNOS, suggesting that the protein S-nitrosylation observed at the leading edge is caused only by iNOS and not eNOS. We have identified MMP-9 as a potential target for S-nitrosylation in these cells and demonstrate that it co-localises with iNOS at the leading edge of migrating cells. We further demonstrate that iNOS plays an important role in promoting trophoblast invasion, which is an essential process in the establishment of a successful pregnancy.

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The objective was to investigate the potential role of the oocyte in modulating proliferation and basal, FSH-induced and insulin-like growth factor (IGF)-induced secretion of inhibin A (inh A), activin A (act A), follistatin (FS), estradiol (E-2), and progesterone (P-4) by mural bovine granulosa cells. Cells from 4- to 6-mm follicles were cultured in serum-free medium containing insulin and androstenedione, and the effects of ovine FSH and IGF analogue (LR3-IGF-1) were tested alone and in the presence of denuded bovine oocytes (2, 8, or 20 per well). Medium was changed every 48 h, cultures were terminated after 144 h, and viable cell number was determined. Results are based on combined data from four independent cultures and are presented for the last time period only when responses were maximal. Both FSH and IGF increased (P < 0.001) secretion of inh A, act A, FS, E-2, and P-4 and raised cell number. In the absence of FSH or IGF, coculture with oocytes had no effect on any of the measured hormones, although cell number was increased up to 1.8-fold (P < 0.0001). Addition of oocytes to FSH-stimulated cells dose-dependently suppressed (P < 0.0001) inh A (6-fold maximum suppression), act A (5.5-fold), FS (3.6-fold), E-2 (4.6-fold), and P-4 (2.4-fold), with suppression increasing with FSH dose. Likewise, oocytes suppressed (P < 0.001) IGF-induced secretion of inh A, act A, FS, and E-2 (P < 0.05) but enhanced IGF-induced P-4 secretion (1.7-fold; P < 0.05). Given the similarity of these oocyte-mediated actions to those we observed previously following epidermal growth factor (EGF) treatment, we used immunocytochemistry to determine whether bovine oocytes express EGF or transforming growth factor (TGF) alpha. Intense staining with TGFalpha antibody (but not with EGF antibody) was detected in oocytes both before and after coculture. Experiments involving addition of TGFalpha to granulosa cells confirmed that the peptide mimicked the effects of oocytes on cell proliferation and on FSH- and IGF-induced hormone secretion. These experiments indicate that bovine oocytes secrete a factor(s) capable of modulating granulosa cell proliferation and responsiveness to FSH and IGF in terms of steroidogenesis and production of inhibin-related peptides, bovine oocytes express TGFalpha but not EGF, and TGFalpha is a prime candidate for mediating the actions of oocytes on bovine granulosa cells.