Embarazo adolescente

Este trabajo aborda principalmente los resultados obtenidos en una investigación realizada con adolescentes embarazadas, en el Barrio Isla del Río Diamante de San Rafael, entre los meses de enero del 2012 y abril del 2013. Se estudian los principales factores que están asociados al embarazo en las adolescentes, tales como pobreza, consumo de tóxicos y deserción escolar. La falta y/o distorsión de la información es otro de los factores que se relacionan con la ocurrencia de los embarazos adolescentes. Las adolescentes pertenecientes a familias disfuncionales, donde las relaciones entre padres o tutores son inadecuadas, violentas, con agresiones, y faltas de respeto, generan carencias afectivas y desapego, lo que en consecuencia impulsa a los adolescentes a la práctica de relaciones sexuales, en busca de ese amor que no tienen en el hogar. Investigaciones similares a la presente se han realizado en diferentes países con resultados equivalentes. En el capítulo I, se analiza lo definido como problema, en función de los datos recolectados en el Centro de Salud Nº159 Humberto Taranto del Barrio de la Isla del Río Diamante de San Rafael, se plantean los objetivos de la presente investigación, y se da cuenta de los trabajos que constituyen la estructura y el respaldo teórico de la investigación. En el capítuloII, se expone el diseño metodológico en donde está incluida la hipótesis del trabajo, variables consideradas, la selección de la muestra, los criterios de inclusión, el instrumento de recolección de datos y análisis y procesamiento de los datos. En el capítulo III, se aborda la interpretación de los resultados obtenidos, se realiza una propuesta de acción para difundir proyectos ya existentes y la conclusión de la tesis.

Figuraciones de "lo afro" y "lo negro" en las producciones culturales cubanas contemporáneas

La apertura producida en Cuba a inicios de los noventa como efecto de la caída del bloque soviético y sus consecuencias socio-económicas en la isla, permitió un proceso de re-etnización que se manifestó en ámbitos culturales, intelectuales y de activismo político. Sin embargo, como todo movimiento social, éste es heterogéneo y presenta resultados disímiles con respecto a las autodefiniciones y las reflexiones teóricas. Por otro lado, algunas expresiones se vuelven controvertidas al ignorar el carácter relacional e histórico de toda etnización y al adjudicarle carácter real a las "razas"

Introducción

Este dossier sobre la narrativa y la poesía de Pedro Juan Gutiérrez incluye diversos trabajos que abordan núcleos centrales de su obra, en especial, los vínculos de sus novelas y de su poesía con el mercado editorial en Cuba y fuera de Cuba, la representación de los sectores marginales de Centro Habana durante el periodo especial de los años 90, la dialéctica entre el voyeurismo y el exhibicionismo, y la configuración de una "escritura sucia"

Figuraciones de "lo afro" y "lo negro" en las producciones culturales cubanas contemporáneas

La apertura producida en Cuba a inicios de los noventa como efecto de la caída del bloque soviético y sus consecuencias socio-económicas en la isla, permitió un proceso de re-etnización que se manifestó en ámbitos culturales, intelectuales y de activismo político. Sin embargo, como todo movimiento social, éste es heterogéneo y presenta resultados disímiles con respecto a las autodefiniciones y las reflexiones teóricas. Por otro lado, algunas expresiones se vuelven controvertidas al ignorar el carácter relacional e histórico de toda etnización y al adjudicarle carácter real a las "razas"

Introducción

Este dossier sobre la narrativa y la poesía de Pedro Juan Gutiérrez incluye diversos trabajos que abordan núcleos centrales de su obra, en especial, los vínculos de sus novelas y de su poesía con el mercado editorial en Cuba y fuera de Cuba, la representación de los sectores marginales de Centro Habana durante el periodo especial de los años 90, la dialéctica entre el voyeurismo y el exhibicionismo, y la configuración de una "escritura sucia"

Figuraciones de "lo afro" y "lo negro" en las producciones culturales cubanas contemporáneas

La apertura producida en Cuba a inicios de los noventa como efecto de la caída del bloque soviético y sus consecuencias socio-económicas en la isla, permitió un proceso de re-etnización que se manifestó en ámbitos culturales, intelectuales y de activismo político. Sin embargo, como todo movimiento social, éste es heterogéneo y presenta resultados disímiles con respecto a las autodefiniciones y las reflexiones teóricas. Por otro lado, algunas expresiones se vuelven controvertidas al ignorar el carácter relacional e histórico de toda etnización y al adjudicarle carácter real a las "razas"

Organic- and carbonate-carbon values and extract data for DSDP Holes 63-467 and 63-471

Quantity, type, and maturity of the organic matter of middle Miocene to Quaternary sediments from the eastern North Pacific (Deep Sea Drilling Project Leg 63) were determined. Hydrocarbons and fatty acids in lipid extracts were analyzed by capillary column gas chromatography and combined gas chromatography/mass spectrometry. Kerogens were investigated by Rock-Eval pyrolysis and microscopy, and vitrinite reflectance values were determined. At Site 467, in the San Miguel Gap of the outer California Continental Borderland, organic carbon contents range from 1.46% to 5.40%. Normalized to organic carbon, total extracts increase from about 10 to 36 mg/g Corg with depth. The organic matter is a mixture of both marine and terrestrial origin, with the marine organic matter representing a high proportion in some of the samples. Steroid hydrocarbons - sterenes and steradienes in the upper part of the section and steranes in the deepest sample - are the most abundant compounds in the nonaromatic hydrocarbon fractions. Perylene, alkylated thiophenes, and aromatic steroid hydrocarbons dominate in the aromatic hydrocarbon fractions of the shallower samples; increasing maturation is indicated by a more petroleumlike aromatic hydrocarbon distribution. Microscopy revealed a high amount of liptinitic organic matter and confirmed the maturation trend as observed from analysis of the extracts. The vitrinite reflectance may be extrapolated to a bottom-hole value of nearly 0.5% Ro. The liquid hydrocarbon potential of the sediments at higher maturity levels is rated to be good to excellent. At Site 471, off Baja California, organic carbon values are between 0.70% and 1.12%. Extract values increase with depth, as at Site 467. The investigation of the soluble and insoluble organic matter, despite some compositional similarities, consistently revealed a more terrigenous influx compared with Site 467. Thus the potential for liquid hydrocarbon generation is lower, the organic matter being more gas-prone. The deepest sample analyzed indicates the onset of hydrocarbon generation. At this site, frequent sand intercalations offer pathways for migration and possibly reservoir formation.

Resistencia a compresión de bloques de tierra comprimidad estabilizada con materiales de sílice de diferente tamaño de partícula.

Los bloques de tierra comprimida (BTC) están actualmente siendo estudiados en gran parte del mundo con diferentes estabilizantes para mejorar diversas de sus características. Esta situación es debida a la importancia que la tierra cruda tiene en el planeta como material de construcción. Su fácil disponibilidad, bajo coste e inercia térmica hacen de la tierra una materia prima fundamental para las viviendas de ciertas poblaciones en el mundo. El objetivo fundamental del presente Trabajo Fin de Máster es determinar si existe una relación del tamaño de partícula del material que aporta la sílice en relación a la reacción química con la cal hidratada para el aumento de la resistencia a compresión de los BTC. Para la diferenciación de los tamaños de partícula de sílice en este estudio se ha utilizado arcilla como componente control de las probetas ensayadas y una pequeña cantidad de nanosílice para comparar con las probetas sin este nanomaterial y determinar así la influencia del tamaño de partícula. Así mismo se han ensayado otros tipos de probetas para confirmar la influencia de la compactación mecánica en los BTC y de la cantidad de agua para considerar un equilibrio entre la resistencia y la trabajabilidad de los BTC. Durante la redacción del trabajo se repasará la importancia comentada de la tierra cruda en la construcción mundial y las principales técnicas que la han usado a lo largo de la historia para sentar las bases de los BTC actuales. También se comentarán y valorarán en lo relativo a los estabilizantes y la resistencia a compresión una serie de investigaciones publicadas con aspectos semejantes a los tratados en este estudio. A continuación se procederá a una explicación de los métodos ejercidos para los ensayos de las probetas de BTC correspondientes a este trabajo para más tarde realizar una discusión de los resultados obtenidos. Con todo ello se establecerán unas conclusiones en lo referente a los objetivos del trabajo.

Leftovers in seed dispersal: ecological implications of partial seed consumption for oak regeneration

1. Successful seed dispersal by animals is assumed to occur when undamaged seeds arrive at a favourable microsite. Most seed removal and dispersal studies consider only two possible seed fates, predation or escape intact. Whether partial consumption of seeds has ecological implications for natural regeneration is unclear. We studied partial consumption of seeds in a rodent-dispersed oak species. 2. Fifteen percent of dispersed acorns were found partially eaten in a field experiment. Most damage affected only the basal portion of the seeds, resulting in no embryo damage. Partially eaten acorns had no differences in dispersal distance compared to intact acorns but were recovered at farther distances than completely consumed acorns. 3. Partially eaten acorns were found under shrub cover unlike intact acorns that were mostly dispersed to open microhabitats. 4. Partially eaten acorns were not found buried proportionally more often than intact acorns, leading to desiccation and exposure to biotic agents (predators, bacteria and fungi). However, partial consumption caused more rapid germination, which enables the acorns to tolerate the negative effects of exposure. 5. Re-caching and shrub cover as microhabitat of destination promote partial seed consumption. Larger acorns escaped predation more often and had higher uneaten cotyledon mass. Satiation at seed level is the most plausible explanation for partial consumption. 6. Partial consumption caused no differences in root biomass when acorns experienced only small cotyledon loss. However, root biomass was lower when acorns experienced heavy loss of tissue but, surprisingly, they produced longer roots, which allow the seeds to gain access sooner to deeper resources. 7.Synthesis. Partial consumption of acorns is an important event in the oak regeneration process, both quantitatively and qualitatively. Most acorns were damaged non-lethally, without decreasing both dispersal distances and the probability of successful establishment. Faster germination and production of longer roots allow partially eaten seeds to tolerate better the exposure disadvantages caused by the removal of the pericarp and the non-buried deposition. Consequently, partially consumed seeds can contribute significantly to natural regeneration and must be considered in future seed dispersal studies.

Disentangling factors controlling fruit and seed removal by rodents in temperate forests

Fleshy fruits fall on to the ground together with cleaned seeds previously ingested by primary dispersers, offering a wide range of fruits and seeds to the ground foragers. Although nutritional properties strongly differ between fruits and seeds, this different seed presentation (cleaned seeds versus seeds within the pulp) has not been addressed in seed removal studies. This study reports on the removal of fruits versus their seeds in five fleshy-fruited species in a temperate forest. We found that rodents removed most of the seeds and partially consumed most of the fruits, preferring seeds to fruits. Rodents bit the fruits to extract the seeds, leaving most of the pulp. We found a preference ranking for the seeds (Sorbus aucuparia>Ilex aquifolium>Sorbus aria>Rosa canina>Crataegus monogyna) but no preferences were found for the fruits, probably due to their similarities in pulp constituents. Seed and fruit choice were affected by chemical and physical properties and not by their size. The presence of alternative and preferred seeds (nuts) delayed the encounter of the fruits and seeds and diminished their removal rates. We found that higher rodent abundance is not necessarily associated with higher removal rates of fleshy fruits. Rodent abundance, fruit size and seed size are minor factors in the removal of fleshy fruits and their seeds. This study underlines that scatter-hoarding rodents are important removers of fleshy fruits and their seeds, producing a differential seed removal depending on the seed presentation (with or without pulp), the nutritional properties of the seeds (but not of the fruits) and the presence of alternative food

Flying vs. climbing: Factors controlling arboreal seed removal in oak-beech forests

Nuts are heavy and nutritious seeds that need animals to be successfully dispersed. Most studies address nut removal by a single animal species once seeds fall onto the ground. However, nuts are also accessible before the seed drop and usually to a wide guild of seed foragers. This study examines the factorscontrollingarborealseedremoval in oak–beechforests within the whole guild of nut foragers. We found that seed-dispersing rodents (Apodemus sylvaticus) were the main acorn removers in the oaks (up to 3.75 m height), with a rapid seed encounter and a high removal rate. However, rodents did not climb the beech trees, probably due to their smoother bark in comparison to oak bark and/or the lower nutritional value of beechnuts with regard to acorns. Jays (Garrulus glandarius) were more abundant in oak stands (both dense and scattered) and clearly preferred acorns to beechnuts whereas nuthatches (Sitta europaea) were more abundant in beech stands and preferred beechnuts to acorns. Non-storing birds such as great tits (Parus major) also removed acorns and beechnuts, especially in the stands where oaks are dominant. Jays and rodents preferred sound seeds over insect-infested seeds but such a preference was not found for nuthatches. This study highlights that pure beech stands showed a reduced guild of arboreal nut foragers in comparison to oak stands. This different guild could probably affect the spatial patterns of seed dispersal, with a proportionally higher number of long dispersal events for acorns (mostly jay-dispersed) than for beechnuts (mostly nuthatch-dispersed). Long-distance dispersal of beechnuts (by jays) is determined by the presence of other preferred species (oaks) and their frequency of non-mast years. Seed location in different habitats strongly determines the contribution of different arboreal removers (including climbing rodents) and their removal speed, leading to a differential seed fate that will eventually affect tree regeneration. As nuthatches are sedentary birds, it is important to maintain old and dead trees where they can breed (crevices), forage (arthropods) and store seeds in order to favor beechnut dispersal and gene flow. By maintaining or favoring oak trees within beech stands we will ensure a wider guild of arboreal nut dispersers.

Moonlight and shelter cause differential seed selection and removal by rodents

Various environmental factors may influence the foraging behaviour of seed dispersers which could ultimately affect the seed dispersal process. We examined whether moonlight levels and the presence or absence of rodentshelter affect rodentseedremoval (rate, handling time and time of removal) and seedselection (size and species) among seven oak species. The presence or absence of safe microhabitats was found to be more important than moonlight levels in the removal of seeds. Bright moonlight caused a different temporal distribution of seedremoval throughout the night but only affected the overall removal rates in open microhabitats. Seeds were removed more rapidly in open microhabitat (regardless of the moon phase), decreasing the time allocated to seed discrimination and translocation. Only in open microhabitats did increasing levels of moonlight decrease the time allocated to selection and removal of seeds. As a result, a more precise seedselection was made under shelter, owing to lower levels of predation risk. Rodent ranking preference for species was identical between full/new moon in shelter but not in open microhabitats. For all treatments, species selection by rodents was much stronger than size selection. Nevertheless, heavy seeds, which require more energy and time to be transported, were preferentially removed under shelter, where there is no time restriction to move the seeds. Our findings reveal that seedselection is safety dependent and, therefore, microhabitats in which seeds are located (sheltered versus exposed) and moonlight levels in open areas should be taken into account in rodent food selection studies.