479 research outputs found
Estudio de tendencias formativas e investigativas en Ingeniería Civil en universidades de Suecia y Suiza
Trabajo de InvestigaciónLa Ingeniería Civil es una disciplina cuyo ejercicio profesional produce dinámica al desarrollo económico y social de las naciones, tiene también un fuerte componente organizativo que logra su aplicación en la administración del ambiente urbano principalmente, y frecuentemente rural; no sólo en lo referente a la construcción, sino también, al mantenimiento, control y operación de lo construido, así como en la planificación de la vida humana en el ambiente diseñado desde esta misma; esto comprende planes de organización territorial tales como prevención de desastres, control de tráfico y transporte, manejo de recursos hídricos, servicios públicos, tratamiento de basuras y todas aquellas actividades que garantizan el bienestar de la humanidad que desarrolla su vida sobre las obras civiles construidas y operadas por ingenieros civiles. La investigación busca identificar las tendencias mundiales asociadas con la Ingeniería Civil como disciplina, con el fin de proporcionar tanto al sector productivo como educativo, los elementos conceptuales y metodológicos que conduzcan a incrementar los índices de productividad y competitividad nacionales, a través de la apropiación, adaptación y generación de herramientas tecnológicas funcionales y pertinentes para el contexto colombiano, que se conviertan en agentes impulsores del desarrollo nacional. El conocimiento obtenido como resultado de la investigación permitirá formular alternativas de formación y de actualización curricular de cara a la permanente y vertiginosa transformación tecnológica que presentan las disciplinas en el mundo.PregradoIngeniero Civi
Índice de Calidad del Suelo Bajo Sistemas Agropecuarios en el Bosque Seco Tropical-Colombia
En las últimas décadas, la creciente demanda de alimentos, asociada al aumento demográfico conllevó a la transformación de áreas boscosas o ecosistemas naturales en tierras de producción agropecuaria. El uso de índices de calidad de suelo permite mejor comprensión del nivel de degradación o mejoría que puede tener el suelo bajo diferentes sistemas agropecuarios, lo que favorece la toma de decisiones y la selección de prácticas de gestión sostenibles. El objetivo de este trabajo fue evaluar el índice de calidad de suelo (ICS) en diferentes sistemas agropecuarios, como estrategia en la toma de decisiones para la conservación y rehabilitación de los suelos en el caribe colombiano. En los departamentos de Atlántico, Córdoba, Bolívar, Sucre, Cesar y Magdalena, se seleccionaron cuatro sistemas de uso de la tierra: sistema forestal comercial (Forestal), sistemas de praderas de ganadería tradicional (Pr), sistemas Agroforestales con cacao (SAF) y sistemas silvopastoriles (SSP); en cada uno se evaluaron variables físicas, químicas y biológicas del suelo con el fin de calcular los ICS. La implementación de SSP favoreció la acumulación de materia orgánica y capacidad de intercambio catiónico (CIC), entre 25 y 29% más que los sistemas monocultivo forestal y Pr. La diversidad biológica del suelo fue mayor dentro de los sistemas asociados con especies arbóreas. La CIC fue el indicador de suelo de mayor relevancia en la construcción del índice, con un aporte de entre 34.7 al 41.2% del valor total del ICS. El conjunto mínimo de datos seleccionados estuvo conformado por CIC, resistencia mecánica a la compactación, porcentaje de arena (A), orden isóptera, pH y contenido de fósforo. El sistema de uso de suelo con mayor ICS fue SAF (0.77), seguido de SSP (0.66). La inclusión de especies arbóreas dentro de los sistemas de producción mejora la calidad del suelo, aumentando la captura de carbono en el suelo en más de 19% dentro de SSP
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Contrasting evidence of phylogenetic trophic niche conservatism in mammals worldwide
Aim
Phylogenetic niche conservatism (PNC), a pattern of closely related species retaining ancestral niche-related traits over evolutionary time, is well documented for abiotic (Grinellian) dimensions of the ecological niche. However, it remains unclear whether biotic niche (Eltonian) axes are also phylogenetically conserved, even though knowledge of biotic niches is essential to an understanding of the spatiotemporal dynamics of ecological communities. We conduct the first analysis of biotic PNC by evaluating dietary specialization in a vertebrate class.
Location
Global
Methods
We analysed two global compilations of diets of living mammals and a more detailed database for large carnivores together with a species-level phylogeny to evaluate trophic PNC. We searched for evidence of PNC by estimating the phylogenetic signal in distinct descriptors of dietary niche.
Results
Trophic niches were generally similar among related species but not strongly conserved under a niche-drift macroevolutionary model (Brownian Motion). The degree of similarity in trophic niche varied among different taxonomic groups and was, importantly, even within the same group, contingent on the metric of dietary preferences used and the quality of information on the database.
Main conclusions
Overall, our results showed limited support for PNC in the trophic niche of mammals. However, different data sources and metrics of dietary preferences sometimes offered different conclusions, highlighting the importance of gathering high-quality quantitative data and considering multiple metrics to describe dietary niche breadth and to assess PNC. The fully quantitative database for large carnivores provided some interesting evidence of PNC that could not be detected with semi-quantitative or presence/absence descriptors. Subsequent assessments of phylogenetic imprints on dietary specialization would benefit from considering different metrics and using well-resolved phylogenies jointly with detailed quantitative diet information. While Eltonian trophic niches did not show the same high levels of evolutionary conservatism often displayed by Grinnellian niches, both niche components should be considered to understand range limits of species and clades at biogeographic scales
Effect of salinity on the biosynthesis of n-3 long-chain polyunsaturated fatty acids in silverside Chirostoma estor
The genus Chirostoma (silversides) belongs to the family Atherinopsidae, which contains around 150 species, most of which are marine. However, Mexican silverside (Chirostoma estor) is one of the few representatives of freshwater atherinopsids and is only found in some lakes of the Mexican Central Plateau. However, studies have shown that C. estor has improved survival, growth and development when cultured in water conditions with increased salinity. In addition, C. estor displays an unusual fatty acid composition for a freshwater fish with high docosahexaenoic acid (DHA) : eicosapentaenoic acid (EPA) ratios. Freshwater and marine fish species display very different essential fatty acid metabolism and requirements and so the present study investigated long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis to determine the capacity of C. estor for endogenous production of EPA and DHA, and the effect that salinity has on these pathways. Briefly, C. estor were maintained at three salinities (0, 5 and 15 ppt) and the metabolism of 14C-labelled 18:3n-3 determined in isolated hepatocyte and enterocyte cells. The results showed that C. estor has the capacity for endogenous biosynthesis of LC-PUFA from 18-carbon fatty acid precursors, but that the pathway was essentially only active in saline conditions with virtually no activity in cells isolated from fish grown in freshwater. The activity of the LCPUFA biosynthesis pathway was also higher in cells isolated from fish at 15 ppt compared to fish at 5 ppt, The pathway was around 5-fold higher in hepatocytes compared to enterocytes, although the majority of 18:3n-3 was converted to 18:4n-3 and 20:4n-3 in hepatocytes whereas the proportions of 18:3n-3 converted to EPA and DHA were higher in enterocytes. The data were consistent with the hypothesis that conversion of EPA to DHA could contribute, at least in part, to the generally high DHA:EPA ratios observed in the tissue lipids of C. estor
Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV
The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8 TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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