Quiescent and coherent cores from gravoturbulent fragmentation

[abridged] We investigate the velocity structure of protostellar cores that result from non-magnetic numerical models of the gravoturbulent fragmentation of molecular cloud material. A large fraction of the cores analyzed are ``quiescent'', and more than half are identified as ``coherent''. The fact that dynamically evolving cores in highly supersonic turbulent flows can be quiescent may be understood because cores lie at the stagnation points of convergent turbulent flows, where compression is at a maximum, and relative velocity differences are at a minimum. The coherence may be due to an observational effect related to the length and concentration of the material contributing to the line. The velocity dispersion of the our cores often has its local maximum at small offsets from the column density maximum, suggesting that the core is the dense region behind a shock. Such a configuration is often found in observations of molecular cloud cores, and argues in favor of the gravoturbulent scenario of stellar birth as it is not expected in star-formation models based on magnetic mediation. Cores with collapsed objects tend to be near equipartition between their gravitational and kinetic energies, while cores without collapsed objects tend to be gravitationally unbound, suggesting that gravitational collapse occurs immediately after gravity becomes dominant. Finally, cores in simulations driven at large scales are more frequently quiescent and coherent, and have more realistic ratios of $M_{\rm vir}/M$, supporting the notion that molecular cloud turbulence is driven at large scales.Comment: ApJ, in pres

Aplicacion de tecnologias de informacion emergentes para apoyar la autocapacitacion intensiva : desarrollo de un ambiente prototipo

74 p.La presente memoria se refiere a la modelación del proceso de autoaprendizaje centrado en el autocontrol y, al diseño de una interfaz como solución tecnológica con nombre de fantasía "i-AP" (interfaz para el autoaprendizaje personalizada) orientada a la implementación de cursos de educación a distancia enfocados a aquellos contenidos denominados "menos complejos" caracterizados por la mínima supervisión del profesor (tutor) en el proceso de enseñanza-aprendizaje. Particularmente se utilizara el modelo propuesto de autoaprendizaje centrado en el autocontrol y la plataforma de diseño y explotación de aplicaciones orientada a redes de trabajo "Lotus Notes" para el diseño de un prototipo de alto nivel de la solución tecnológica i-AP

Alternative transcription start site selection leads to large differences in translation activity in yeast

mRNA levels do not accurately predict protein levels in eukaryotic cells. To investigate contributions of 5′ untranslated regions (5′ UTRs) to mRNA-specific differences in translation, we determined the 5′ UTR boundaries of 96 yeast genes for which in vivo translational efficiency varied by 80-fold. A total of 25% of genes showed substantial 5′ UTR heterogeneity. We compared the capacity of these genes' alternative 5′ UTR isoforms for cap-dependent and cap-independent translation using quantitative in vitro and in vivo translation assays. Six out of nine genes showed mRNA isoform-specific translation activity differences of greater than threefold in at least one condition. For three genes, in vivo translation activities of alternative 5′ UTR isoforms differed by more than 100-fold. These results show that changing genes' 5′ UTR boundaries can produce large changes in protein output without changing the overall amount of mRNA. Because transcription start site (TSS) heterogeneity is common, we suggest that TSS choice is greatly under-appreciated as a quantitatively significant mechanism for regulating protein production.National Institutes of Health (U.S.) (NIH grant GM081399

The Photometric Variability of HH 30

This is the final version. Available from Universidad Nacional Autónoma de México via the link in this recordHH 30 is an edge-on disk around a young stellar object. Previous imaging with the Hubble Space Telescope has shown morphological variability that is possibly related to the rotation of the star or the disk. We report the results of two terrestrial observing campaigns to monitor the integrated magnitude of HH 30. We use the Lomb-Scargle periodogram to look for periodic modulation with periods between 2 days and almost 90 days in these two data sets and in a third, previously published, data set. We develop a method to deal with short-term correlations in the data. Our results indicate that none of the data sets shows evidence for significant periodic photometric modulation

Translation initiation factor eIF4G1 preferentially binds yeast transcript leaders containing conserved oligo-uridine motifs

Translational control of gene expression plays essential roles in cellular stress responses and organismal development by enabling rapid, selective, and localized control of protein production. Translational regulation depends on context-dependent differences in the protein output of mRNAs, but the key mRNA features that distinguish efficiently translated mRNAs are largely unknown. Here, we comprehensively determined the RNA-binding preferences of the eukaryotic initiation factor 4G (eIF4G) to assess whether this core translation initiation factor has intrinsic sequence preferences that may contribute to preferential translation of specific mRNAs. We identified a simple RNA sequence motif-oligo-uridine-that mediates high-affinity binding to eIF4G in vitro. Oligo(U) motifs occur naturally in the transcript leader (TL) of hundreds of yeast genes, and mRNAs with unstructured oligo(U) motifs were enriched in immunoprecipitations against eIF4G. Ribosome profiling following depletion of eIF4G in vivo showed preferentially reduced translation of mRNAs with long TLs, including those that contain oligo(U). Finally, TL oligo(U) elements are enriched in genes with regulatory roles and are conserved between yeast species, consistent with an important cellular function. Taken together, our results demonstrate RNA sequence preferences for a general initiation factor, which cells potentially exploit for translational control of specific mRNAs. Keywords: RNA binding; eIF4G; ribosome footprint profiling; transcript leaders; translation initiationNational Institutes of Health (U.S.) (Grant GM094303)National Institutes of Health (U.S.) (Grant GM081399)National Institutes of Health (U.S.) (Grant T32GM007287

Valoración del grado de madurez en la gestión de proyectos de la empresa Gustavo Perry Arquitectos S.A.S. de Bogotá basados en herramientas de PMBOK

Trabajo de investigaciónEl presente proyecto de grado tiene como fin realizar la valoración del grado de madurez en la gestión de proyectos de la empresa GUSTAVO PERRY ARQUITECTOS S.A.S, identificando las practicas y estándares de la gerencia de proyectos aplicados a proyectos de diseño, se conoció el grado de madures por grupos de procesos y por ultimo se propusieron estrategias y herramientas a mediano y corto plazo para el mejoramiento del grado de madurez.INTRODUCCIÓN 1. GENERALIDADES 2. MARCOS DE REFERENCIA 3. METODOLOGÍA 4. RESULTADOS 5. ANÁLISIS DE RESULTADOS E IMPACTOS 6. PROPUESTA DE MEJORA DE LA CULTURA DE PROYECTOS EN LA EMPRESA GUSTAVO PERRY ARQUITECTOS S.A.S 7. CONCLUSIONES BIBLIOGRAFÍA ANEXOSEspecializaciónEspecialista en Gerencia de Obras Civile

JULES-BE:Representation of bioenergy crops and harvesting in the Joint UK Land Environment Simulator vn5.1

We describe developments to the land surface model JULES, allowing for flexible user-prescribed harvest regimes of various perennial bioenergy crops or natural vegetation types. Our aim is to integrate the most useful aspects of dedicated bioenergy models into dynamic global vegetation models, in order that assessment of bioenergy options can benefit from state-of-the-art Earth system modelling. A new plant functional type (PFT) representing Miscanthus is also presented. The Miscanthus PFT fits well with growth parameters observed at a site in Lincolnshire, UK; however, global observed yields of Miscanthus are far more variable than is captured by the model, primarily owing to the model's lack of representation of crop age and establishment time. Global expansion of bioenergy crop areas under a 2 ?C emissions scenario and balanced greenhouse gas mitigation strategy from the IMAGE integrated assessment model (RCP2.6- SSP2) achieves a mean yield of 4.3 billion tonnes of dry matter per year over 2040-2099, around 30 % higher than the biomass availability projected by IMAGE. In addition to perennial grasses, JULES-BE can also be used to represent short-rotation coppicing, residue harvesting from cropland or forestry and rotation forestry

El realismo científico y el conocimiento de los inobservables

El presente trabajo echa un vistazo al desarrollo de la discusión entre realistas y anti-realistas, analiza los diversos argumentos a favor y en contra de la posición realista, explora algunas de las versiones realistas más famosas e influyentes y evalúa una versión estructuralista del realismo científico denominada semi‐realismo. Y al mismo tiempo explora las respuestas que las posturas más representativas e influyentes han dado a la siguiente pregunta epistemológica: ¿qué aspectos se pueden conocer del mundo inobservable? la cual parte de los siguientes supuestos 1) la existencia de un mundo independiente a la mente (o los procesos mentales) de los sujetos; y 2) que el mundo se divide en objetos que podemos percibir mediante nuestros órganos sensoriales y aquellos que no. Para dar respuesta a tal pregunta se desarrollan 6 capítulos. En el primero se expone la división observable/ inobservable y el compromiso epistemológico realista de que podemos conocer ambos aspectos de la realidad. El segundo presenta la postura filosófica del realismo científico, sus argumentos a favor y los diversos argumentos escépticos en su contra, sus versiones más plausibles (realismo de entidades y el realismo estructural) y sus correspondientes tesis epistemológicas acerca del mundo inobservable. En el tercero se muestra una versión novedosa de realismo científico –el semi-realismo- que pretende responder nuestra pregunta de manera más ambiciosa que los realismos científicos expuestos en el capítulo anterior. El cuarto muestra la necesidad de refinar y aclarar algunos términos de la posición realista expuesta en el capítulo anterior de la mano de la exposición del estructuralismo matemático. El quinto muestra la posible interpretación semi-realista de las diversas teorías geométricas y la mecánica newtoniana acerca del conocimiento de una entidad inobservable: el espacio. El sexto y último presenta críticas a la posición semi-realista, posibles respuestas y la conclusión final de todo lo expuesto a lo largo del trabajo