Exploring the UV spectral range to constrain the evolution of massive galaxies in varying environments and varying redshift

Las galaxias más masivas del Universo local son las galaxias de tipo temprano (del inglés, ETGs) que comprenden las galaxias elípticas y lenticulares. El grueso de sus poblaciones de estrellas son viejas y prácticamente no están formando nuevas estrellas. Su actividad de formación estelar no es lo que llegó a ser en las etapas tempranas del Universo, donde grandes cantidades de gas se transformaron en estrellas. La formación de estrellas se detuvo rápidamente y las ETGs evolucionaron como sistemas rojos y viejos. Cuáles fueron los mecanismos físicos responsables de detener la creación de nuevas estrellas sigue siendo un misterio, aunque se cree que las contribuciones de los núcleos activos de galaxias (del inglés, AGNs) pudieron transformar estos sistemas estelares en objetos evolucionando pasivamente con escasa formación estelar. Las estrellas viejas de las ETGs emiten la mayor parte de su luz en el rango espectral óptico. El óptico, sin embargo, es relativamente insensible a pequeñas fracciones de poblaciones estelares jóvenes, cuya luz domina en el rango ultravioleta (UV). Afortunadamente, el UV es un trazador óptimo de las poblaciones estelares más calientes como las estrellas jóvenes. Estudios fotométricos en el UV han puesto de manifiesto que las ETGs pueden tener formación de estrellas a un ritmo muy bajo. Sin embargo, el rango UV en los espectros de las ETGs no ha sido explorado para determinar sus poblaciones jóvenes. El objetivo de esta tesis es cuantificar estas poblaciones estelares jóvenes de las ETGs masivas usando las líneas de absorción de sus espectros. Hemos usado nuevos modelos de poblaciones estelares para analizar, por primera vez, índices espectrales ópticos y del UV cercano simultáneamente. Comparamos las observaciones con las predicciones de los modelos de dos parametrizaciones de las historias de formación estelar (del inglés, SFH) de las galaxias masivas. Primero hemos investigado si la formación de estrellas residual es una característica común entre la población de ETGs, mediante la suma de miles de espectros de galaxias masivas a un desplazamiento al rojo medio de z~0.4. De estos espectros sumados hemos podido obtener las fracciones de población joven en función de la masa de la galaxia. Hemos encontrado que las ETGs masivas tienen en promedio una fracción de estrellas jóvenes formadas en los últimos 2 mil millones de años por debajo del 1%, y que ésta fracción es mayor para las galaxias menos masivas. Esta tendencia con la masa es consistente con el hecho que las galaxias menos masivas tienen SFH más extendidas en el tiempo que las más masivas. También hemos visto que las galaxias masivas sintéticas de las simulaciones cosmológicas producen demasiadas estrellas de edades intermedias. Esto implica que los procesos para suprimir la formación de estrellas en galaxias masivas y mantenerla suprimida en el tiempo, aun necesitan ser comprendidos. Nuestros resultados ponen rigurosos límites que necesitan ser satisfechos por las simulaciones. Para intentar entender el origen de estas poblaciones jóvenes, hemos analizado espectros resueltos espacialmente para obtener información de dónde están situadas en las galaxias. Para ello, hemos analizado un tipo especial de ETGs: las galaxias más brillantes de los cúmulos de galaxias (del inglés, BCGs). Estas galaxias se encuentran en el centro de los potenciales gravitatorios de los cúmulos de galaxias. Nuestro estudio de 6 BCGs cercanas ha demostrado que sus estrellas jóvenes están en el interior de <2 kpc del centro de las galaxias, es decir, en los núcleos. Las pequeñas fracciones de estrellas jóvenes que encontramos son consistentes con un origen in-situ, es decir, la formación de estrellas residual puede producirse gracias al material reciclado de la muerte de estrellas de generaciones anteriores o del gas inicial residual. Sin embargo, debido a la ubicación de estos objetos, un origen ex-situ a través los efectos y procesos del entorno del no puede ser descartado. Estudiar las componentes estelares jóvenes en galaxias reliquias nos ayuda a entender los orígenes de la formación estelar reciente que detectamos en las galaxias ETGs normales. Estas galaxias reliquias, masivas y compactas, han sobrevivido intactas desde su formación a alto desplazamiento al rojo hasta el Universo local, es decir, sin haber experimentado un crecimiento tanto en tamaño como en masa a través de fusiones e interacciones con otras galaxias. Por ello, hemos estudiado la contribución de las poblaciones jóvenes en la región central de 1 kpc de la galaxia NGC 1277, la galaxia reliquia por excelencia del Universo cercano. Encontramos una población joven que contribuye menos del 1%, similar a los resultados previos, lo que apunta a que la formación estelar reciente encontrada en galaxias masivas ETGs puede estar relacionada con los procesos intrínsecos de las galaxias.Early-type galaxies (ETGs), consisting of ellipticals and lenticulars, are the most massive galaxies in the local Universe. The bulk of their stellar populations are characterised as being old with negligible recent star formation activity, having followed a passive evolution from the high-redshift Universe to the present day. Their star formation activity is not what used to be at the early Universe (z > 2), where large amounts of gas were transformed into stars. Star formation was virtually extinguished in rather short time and ETGs evolved as red and dead objects. The exact physical mechanisms responsible for quenching the star formation in these massive systems at high-redshift is not completely resolved. Although, it is widely considered that AGN feedback could turn these stellar systems into passively evolving objects without significant formation of new stars. There is growing observational and theoretical evidences for a two-phase formation scenario for ETGs. According to this picture, during the first phase the cores of present-day ETGs are formed at z > 2 dissipatively, while in the second phase the outer regions are a result of mergers and accretion. This is supported by a large number of studies that have shown that massive galaxies at z > 2 are more compact than their local counterparts, and have experienced significant growth both in size and, to a lesser degree, in mass. This suggests that these high-z massive compacts are the cores of local ETGs formed at high redshift, while the outer regions are where the accreted material due to dissipationless mergers (i.e. gas-poor) is deposited. This second phase is mostly ”dry”, i.e. does not trigger star formation, at least not in any efficient way. The bulk of the stars in ETGs are ancient and emit much of their light in the optical spectral range. However, the optical is relatively insensitive to small fractions of young stellar populations, whose light dominate the ultraviolet (UV). Studies of the optical range are therefore, biased to the old stellar populations. Fortunately, the UV is an optimal tracer of the hottest stellar populations such as young stars. Photometric studies in the UV have previously suggested that ETGs might have recent low-level star formation. However, the UV window of ETG’s spectra has not been explored for determining the youngest stellar populations. This thesis aims to quantify these young stellar populations by using spectral absorption features of massive ETGs. We exploit state-of-the-art stellar population models based on empirical stellar libraries to analyse, for the first time, observed optical and near-UV line-strength indices simultaneously. We compare observations with model predictions from two assumed simple parameterisations of the star formation history (SFH) of massive galaxies. We first explore if the residual star formation is ubiquitous among the massive ETG population by stacking thousands of galaxy spectra at redshift of z ∼ 0.4. We derive mass fractions of the young stellar component as a function of mass. We find that massive galaxies show, on average, a sub-one percent fraction of young stars formed within the last 2 Gyr, and that this fraction is larger for less massive galaxies. This trend with mass is consistent with the fact that less massive galaxies have more extended SFHs than their more massive counterparts and also may be related to the fact that AGN feedback stops the formation of new stars more efficiently for more massive galaxies. We also find that synthetic massive galaxies from cosmological numerical simulations significantly overproduce both intermediate and young stellar populations. This means that the recipe to quench the star formation in these galaxies, and perhaps to maintain them quenched, still needs to be fully understood. However, the results obtained here put stringent constrains that must be satisfied by these simulations. In order to understand the origin of these young stars, we turned to spatially resolved spectroscopy to tell us precisely where they are located. For this purpose, we analyse a special type of ETGs: the brightest cluster galaxies (BCGs). These galaxies are located in the centres of the gravitational potential wells of galaxy clusters. Our study of 6 nearby BCGs indicate that their young stars are located within < 2 kpc of the galaxy centres, i.e. in their cores. Our findings of small young mass fractions are consistent with being formed in-situ, likely residual star formation from recycled material of dying stars from previous generations. However, due to the particular location of these massive systems, an ex-situ origin through environmental processes can not be ruled out. The study of young stellar components in so-called ”relic galaxies” offers us unique clues to understand the possible origins of the recent star formation that we detect in normal ETGs. These massive compact relic galaxies are thought to have survived untouched since their formation at high-z until the presentday, i.e. without having gone through a second phase that is characterised by a growth in size and mass by accretion. For this purpose, we studied the young stellar contribution in the 1 kpc central region of NGC 1277, a well studied galaxy that is regarded as the prototypical relic galaxy in the nearby Universe. We find a sub-one percent level of young mass fractions, similar to our samples of massive ETGs, which points to intrinsic, in-situ, processes that trigger the formation of these young stars

Quantitative RNA-seq Analysis Unveils Osmotic and Thermal Adaptation Mechanisms Relevant for Ectoine Production in Chromohalobacter salexigens

Quantitative RNA sequencing (RNA-seq) and the complementary phenotypic assays were implemented to investigate the transcriptional responses of Chromohalobacter salexigens to osmotic and heat stress. These conditions trigger the synthesis of ectoine and hydroxyectoine, two compatible solutes of biotechnological interest. Our findings revealed that both stresses make a significant impact on C. salexigens global physiology. Apart from compatible solute metabolism, the most relevant adaptation mechanisms were related to “oxidative- and protein-folding- stress responses,” “modulation of respiratory chain and related components,” and “ion homeostasis.” A general salt-dependent induction of genes related to the metabolism of ectoines, as well as repression of ectoine degradation genes by temperature, was observed. Different oxidative stress response mechanisms, secondary or primary, were induced at low and high salinity, respectively, and repressed by temperature. A higher sensitivity to H2O2 was observed at high salinity, regardless of temperature. Low salinity induced genes involved in “protein-folding-stress response,” suggesting disturbance of protein homeostasis. Transcriptional shift of genes encoding three types of respiratory NADH dehydrogenases, ATP synthase, quinone pool, Na+/H+ antiporters, and sodium-solute symporters, was observed depending on salinity and temperature, suggesting modulation of the components of the respiratory chain and additional systems involved in the generation of H+ and/or Na+ gradients. Remarkably, the Na+ intracellular content remained constant regardless of salinity and temperature. Disturbance of Na+- and H+-gradients with specific ionophores suggested that both gradients influence ectoine production, but with differences depending on the solute, salinity, and temperature conditions. Flagellum genes were strongly induced by salinity, and further induced by temperature. However, salt-induced cell motility was reduced at high temperature, possibly caused by an alteration of Na+ permeability by temperature, as dependence of motility on Na+-gradient was observed. The transcriptional induction of genes related to the synthesis and transport of siderophores correlated with a higher siderophore production and intracellular iron content only at low salinity. An excess of iron increased hydroxyectoine accumulation by 20% at high salinity. Conversely, it reduced the intracellular content of ectoines by 50% at high salinity plus high temperature. These findings support the relevance of iron homeostasis for osmoadaptation, thermoadaptation and accumulation of ectoines, in C. salexigens.España Ministerio de Economía y Competitividad BIO2015-63949-RJunta de Andalucía P11-CVI-729

Nutritional Status and Infant and Young Child Feeding (IYCF) Practices among Buhid Mangyan Tribe, Occidental Mindoro Philippines

Nutritionally adequate and safe complementary feeding starting from the age of 6 months up to 59 months is one of the effective intervention to reduce infant and child morbidity and malnutrition. This study aims to determine the nutritional status of children ages 6-59 months and their caregiver’s infant and young child feeding (IYCF) practices of the Buhid community in Rizal, Occidental Mindoro. The design used in this study was a descriptive cross-sectional carried out between December 2016-February 2017. A survey questionnaire was utilized as an instrument in this study. It includes an anthropometric survey of 6-59 months old and infant and young child feeding practices using WHO and UNICEF IYCF indicators. Vaccination, vitamin A supplementation and deworming coverage were also measured. Findings revealed a prevalence of global acute malnutrition (GAM) at a critical level. There is a low but significant prevalence of stunting and underweight among children. There is a good infant and young feeding practice in the community except for the minimum acceptable diet during complementary feeding. Lastly, there is low BCG and measles vaccination coverage in the community that could be a threat to the impending disease outbreak

Perceptions of local population on the impacts of substitution of fossil energies by renewables: A case study applied to a Spanish rural area

Using the perceptions of a sample of 231 people from a Spanish region as a case study, this paper aims to respond to the increasing demand for measurement of economic, social and environmental performance of renewables implementation. First, from this information, the paper analyzes the willingness to pay of the rural community for the complete replacement of fossil fuels with clean ones throughout the region. Second, it explores this rural community''s perceptions in order to determine the most outstanding outputs, outcomes and impacts for the whole renewable energy penetration

Aplicación web con énfasis multimedia para divulgar los principales sitios turísticos, promovidos por INTUR en el municipio de Matagalpa, año 2013

El Instituto Nicaragüense de Turismo INTUR-Matagalpa, se enfoca en la divulgación y promoción de los sitios turísticos más importantes del municipio, actualmente la información recolectada y los destinos turísticos inscritos se manejan de forma escrita, presentando problemas al momento de brindar información; en cuanto a la divulgación se ha hecho de manera tradicional. Por lo tanto surgió la necesidad de evaluar el proceso de divulgación de los principales sitios turísticos de este municipio, con el fin de detectar las dificultades y así brindar alternativas de solución que puedan ser accesibles y las puedan implementar, para que el instituto nicaragüense de turismo en Matagalpa lleve un control más óptimo de dichos procesos. Además la importancia de proponer una aplicación web con énfasis multimedia, radica que a través de ella se podrá presentar o comunicar información de una forma original y llamativa, añadiendo gráficos, textos, imágenes, animaciones, sonido, tours virtuales, visitas previas a los sitios, videos, entre otros, permitiendo que los turistas tanto nacionales como extranjeros puedan elegir entre las vistas propuestas presentadas a través de la aplicación web. En el proceso de divulgación de los principales sitios turísticos se utilizan los medios electrónicos, audiovisuales e impresos, las dificultades encontradas en este proceso de divulgación son: Ausencia de presupuesto, Falta de capacitación del personal, Ausencia de una página web y además ineficiencia de la comunicación de información al momento de promover dichos sitios turísticos y se logró desarrollar una aplicación web con énfasis multimedia, que dará solución a dichas dificultades encontrada

Spherical deconvolution of multichannel diffusion MRI data with non-Gaussian noise models and spatial regularization

Spherical deconvolution (SD) methods are widely used to estimate the intra-voxel white-matter fiber orientations from diffusion MRI data. However, while some of these methods assume a zero-mean Gaussian distribution for the underlying noise, its real distribution is known to be non-Gaussian and to depend on the methodology used to combine multichannel signals. Indeed, the two prevailing methods for multichannel signal combination lead to Rician and noncentral Chi noise distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique, intended to deal with realistic MRI noise, based on a Richardson-Lucy (RL) algorithm adapted to Rician and noncentral Chi likelihood models. To quantify the benefits of using proper noise models, RUMBA-SD was compared with dRL-SD, a well-established method based on the RL algorithm for Gaussian noise. Another aim of the study was to quantify the impact of including a total variation (TV) spatial regularization term in the estimation framework. To do this, we developed TV spatially-regularized versions of both RUMBA-SD and dRL-SD algorithms. The evaluation was performed by comparing various quality metrics on 132 three-dimensional synthetic phantoms involving different inter-fiber angles and volume fractions, which were contaminated with noise mimicking patterns generated by data processing in multichannel scanners. The results demonstrate that the inclusion of proper likelihood models leads to an increased ability to resolve fiber crossings with smaller inter-fiber angles and to better detect non-dominant fibers. The inclusion of TV regularization dramatically improved the resolution power of both techniques. The above findings were also verified in brain data

Nature and Nurture in Dark Matter Halos

Cosmological simulations consistently predict specific properties of dark matter halos, but these have not yet led to a physical understanding that is generally accepted. This is especially true for the central regions of these structures. Recently two major themes have emerged. In one, the dark matter halo is primarily a result of the sequential accretion of primordial structure (ie `Nature'); while in the other, dynamical relaxation (ie `Nurture') dominates at least in the central regions. Some relaxation is however required in either mechanism. In this paper we accept the recently established scale-free sub-structure of halos as an essential part of both mechanisms. Consequently; a simple model for the central relaxation based on a self-similar cascade of tidal interactions, is contrasted with a model based on the accretion of adiabatically self-similar, primordial structure. We conclude that a weak form of this relaxation is present in the simulations, but that is normally described as the radial orbit instability.Comment: 25 pages, 3 figures, fig with parts 1 to d, fig 3 with parts a to

A pushing mechanism for microtubule aster positioning in a large cell type

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Meaders, J. L., de Matos, S. N., & Burgess, D. R. A pushing mechanism for microtubule aster positioning in a large cell type. Cell Reports, 33(1), (2020): 108213, doi:10.1016/j.celrep.2020.108213.After fertilization, microtubule (MT) sperm asters undergo long-range migration to accurately position pronuclei. Due to the large sizes of zygotes, the forces driving aster migration are considered to be from pulling on the astral MTs by dynein, with no significant contribution from pushing forces. Here, we re-investigate the forces responsible for sperm aster centration in sea urchin zygotes. Our quantifications of aster geometry and MT density preclude a pulling mechanism. Manipulation of aster radial lengths and growth rates, combined with quantitative tracking of aster migration dynamics, indicates that aster migration is equal to the length of rear aster radii, supporting a pushing model for centration. We find that dynein inhibition causes an increase in aster migration rates. Finally, ablation of rear astral MTs halts migration, whereas front and side ablations do not. Collectively, our data indicate that a pushing mechanism can drive the migration of asters in a large cell type.We would like to thank Dr. Jesse Gatlin for sending us the Tau-mCherry fusion protein for imaging live MTs. We would also like to thank Dr. Timothy Mitchison, Dr. Christine Field, and Dr. James Pelletier for supplying us with CA4, p150-CC1, and EB1-GFP peptides, as well as for fruitful discussions. Finally, we would like to thank Dr. Charles Shuster and Leslie Toledo-Jacobo for constructive feedback when preparing the manuscript. We thank Bret Judson and the Boston College Imaging Core for infrastructure and support. This material is based upon work supported by NSF grant no. 124425 to D.R.B

Simulating water distribution patterns for fixed spray plate sprinkler using the ballistic theory

Ballistic simulation of the spray sprinkler for self-propelled irrigation machines requires the incorporation of the effect of the jet impact with the deflecting plate. The kinetic energy losses produced by the jet impact with the spray plate were experimentally characterized for different nozzle sizes and two working pressures for fixed spray plate sprinklers (FSPS). A technique of low speed photography was used to determine drop velocity at the point where the jet is broken into droplets. The water distribution pattern of FSPS for different nozzle sizes, working at two pressures and under different wind conditions were characterized in field experiments. The ballistic model was calibrated to simulate water distribution in different technical and meteorological conditions. Field experiments and the ballistic model were used to obtain the model parameters (D50, n, K1 and K2). The results show that kinetic energy losses decrease with nozzle diameter increments; from 80% for the smallest nozzle diameter (2 mm) to 45% for nozzle diameters larger than 5.1 mm, and from 80% for the smallest nozzle diameter (2 mm) to 34.7% for nozzle diameters larger than 6.8 mm, at 138 kPa and 69 kPa working pressures, respectively. The results from the model compared well with field observations. The calibrated model has reproduced accurately the water distribution pattern in calm (r = 0.98) and high windy conditions (r = 0.76). A new relationship was found between the corrector parameters (K1’ and K2’) and the wind speed. As a consequence, model simulation will be possible for untested meteorological conditions