Involutions of polynomially parametrized surfaces

We provide an algorithm for detecting the involutions leaving a surface defined by a polynomial parametrization invariant. As a consequence, the symmetry axes, symmetry planes and symmetry center of the surface, if any, can be determined directly from the parametrization, without computing or making use of the implicit representation. The algorithm is based on the fact, proven in the paper, that any involution of the surface comes from an involution of the parameter space (the real plane, in our case); therefore, by determining the latter, the former can be found. The algorithm has been implemented in the computer algebra system Maple 17. Evidence of its efficiency for moderate degrees, examples and a complexity analysis are also given

Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies

Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disc galaxies, in which gas rotation accurately traces the gravitational potential, the interstellar medium (ISM) of z ≳ 1 galaxies is typically more dynamic and exhibits elevated turbulence. If not properly modelled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyse the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a range of galaxy properties from low-redshift Milky-Way-mass galaxies to massive high-redshift galaxies (M⋆ > 10¹¹ M⊙ at z = 1). Selecting only snapshots where a disc is present, we calculate the rotational profile v_ϕ(r) of the cool (⁠10^(3.5) < T <10^(4.5) K⁠) gas and compare it to the circular velocity v_c = √GM_(enc)/r⁠. In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the centre and in the outer disc. Our simulations appear to over-predict observed rotational velocities in the centres of massive galaxies (likely from a lack of black hole feedback), so we focus on larger radii. Gradients in the turbulent pressure at these radii can provide additional radial support and bias dynamical mass measurements low by up to 40 per cent. In both the interior and exterior, the gas’ motion can be significantly non-circular due to e.g. bars, satellites, and inflows/outflows. We discuss the accuracy of commonly used analytic models for pressure gradients (or ‘asymmetric drift’) in the ISM of high-redshift galaxies

Disappearing galaxies: the orientation dependence of JWST-bright, HST-dark, star-forming galaxy selection

Galaxies that are invisible in deep optical-NIR imaging but detected at longer wavelengths have been the focus of several recent observational studies, with speculation that they could constitute a substantial missing population and even dominate the cosmic star formation rate density at $z\gtrsim4$. The depths now achievable with JWST at the longest wavelengths probed by HST, coupled with the transformative resolution at longer wavelengths, are already enabling detailed, spatially-resolved characterisation of sources that were invisible to HST, often known as `HST-dark' galaxies. However, until now, there has been little theoretical work to compare against. We present the first simulation-based study of this population, using highly-resolved galaxies from the Feedback in Realistic Environments (FIRE) project, with multi-wavelength images along several lines of sight forward-modelled using radiative transfer. We naturally recover a population of modelled sources that meet commonly-used selection criteria ($H_{\rm{AB}}>27\,\rm{mag}$ and $H_{\rm{AB}}-\rm{F444W}>2.3$). These simulated HST-dark galaxies lie at high redshifts ($z=4-7$), have high levels of dust attenuation ($A_{V}=2-4$), and display compact recent star formation ($R_{1/2,\,\rm{4.4\,\mu\rm{m}}}\lesssim1\,\rm{kpc}$). Orientation is very important: for all but one of the 17 simulated galaxy snapshots with HST-dark sightlines, there exist other sightlines that do not meet the criteria. This result has important implications for comparisons between observations and models that do not resolve the detailed star-dust geometry, such as semi-analytic models or coarsely-resolved hydrodynamical simulations. Critically, we demonstrate that HST-dark sources are not an unexpected or exotic population, but a subset of high-redshift, highly-dust-attenuated sources viewed along certain lines of sight.Comment: 12 pages, 8 figures. Accepted for publication in Ap

Extracellular matrix and fibrosis in the adipose tissue in obesity and insulin resistance

La ECM del tejido adiposo es fundamental para mantener la homeostasis del tejido, así como para la formación y mantenimiento de la estructura del propio tejido (Divoux & Clement, 2011). Como en otros tejidos, la ECM del tejido adiposo contiene diversos tipos de colágeno, glicoproteínas de adhesión (fibronectina, laminina, etc), proteínas elásticas y proteoglicanos (PGs), (Humphrey, Dufresne, & Schwartz, 2014; Mouw, Ou, & Weaver, 2014; Theocharis & Karamanos, 2019), si bien la presencia y cantidad relativa de cada uno de estos componentes puede variar entre especies, tipo de depósito graso y fase de desarrollo (Mariman & Wang, 2010). Los componentes de la ECM son producidos por los adipocitos y células de la SVF, como fibroblastos y macrófagos (Mariman & Wang, 2010). Durante el desarrollo de obesidad, el aumento de tamaño y número de adipocitos, junto con la infiltración de células inmunes y la neovascularización del tejido adiposo en expansión conllevan una profunda remodelación de la ECM, incluyendo tanto la degradación como la producción de nuevos componentes de la matriz (Baker et al., 2017; Divoux & Clement, 2011; Pellegrinelli et al., 2016; Rutkowski et al., 2015). Si el aporte de nutrientes y el estado inflamatorio persisten, se produce la disfunción del tejido adiposo que se caracteriza, entre otros procesos patológicos, por el desarrollo de fibrosis que limita la expansión del tejido (Pellegrinelli et al., 2016). Estudios pioneros de transcriptómica de tejido adiposo subcutáneo (SC) de individuos delgados vs. Individuos con obesidad demostraron que la obesidad estaba asociada a un aumento significativo de genes y rutas intracelulares relacionadas con constituyentes de la ECM, además de demostrar la presencia de fibrosis en el tejido (Henegar et al., 2008). Posteriormente se demostró que, en comparación con individuos delgados, en los individuos con obesidad se producía un aumento tanto de la fibrosis total como de la pericelular en el tejido adiposo SC y el tejido adiposo omental (OM) (Khan et al., 2009; Vila et al., 2014). Respecto a la composición de la ECM en obesidad, diferentes estudios han mostrado aumentos fundamentalmente en isoformas de colágeno I (COL-I) (COL-Iα1) y colágeno VI (COL-VI) (COL-VIα3) en el tejido adiposo (SC y/o OM) de individuos con obesidad (con o sin síndrome metabólico) respecto a individuos delgados o en animales obesos [ob/ob, o sometidos a dieta alta en grasa (HFD)] (Khan et al., 2009; Vila et al., 2014). No obstante, aún hay controversia con relación a los resultados obtenidos en los estudios que han explorado el impacto de estos cambios en los componentes de la ECM del tejido adiposo. También se han encontrado datos contradictorios en cuanto a los cambios que ocurren cuando la obesidad concurre con enfermedades metabólicas. Así, se ha descrito una disminución de colágenos fibróticos, o la ausencia de cambios en ciertos tipos de colágeno, en pacientes con obesidad con y sin IR (Guglielmi et al., 2015). Esta discrepancia entre la expresión de colágenos y la presencia de fibrosis ha llevado a proponer que los cambios que ocurren en la ECM podrían afectar no solo a la cantidad de colágenos sino depender también de factores que aumentan la estabilidad y el entrecruzamiento del colágeno, evitando así su degradación (Guglielmi et al., 2015). En este contexto, se ha demostrado que en el tejido adiposo de personas con obesidad e IR existen niveles de expresión más elevados de proteínas de la ECM reguladoras de la formación de fibrillas (fibrilogénesis) o de la actividad de las MMPs y TGF-β (SPARC, osteopontina) y proteasas (MMP7) que en individuos con obesidad pero sin IR (Divoux & Clement, 2011; Lawler et al., 2016). Notablemente, varios estudios han demostrado el aumento de la expresión del PG, lumican (LUM), en el tejido adiposo humano y murino en obesidad (Henegar et al., 2008; Vila et al., 2014) y, de hecho, la exposición de preadipocitos de individuos delgados a medio condicionado de macrófagos aumenta la expresión de LUM mientras que su expresión disminuye en animales ob/ob KO para COL-VI (i.e., metabólicamente saludables) (Divoux & Clement, 2011; Khan et al., 2009). A pesar de estas observaciones, aún no se ha determinado la función de LUM en el tejido adiposo, si bien se han descrito numerosas e importantes funciones de este PG en otros tejidos. Así, diversos estudios han demostrado que las interacciones moleculares del LUM con las fibrillas de colágeno influyen de manera fundamental en la arquitectura tisular del colágeno y las características biomecánicas de los tejidos (Stamov, Muller, Wegrowski, Brezillon, & Franz, 2013). En esta línea, nuestros estudios proteómicos previos de muestras pareadas de tejido adiposo SC y OM de individuos delgados vs. individuos con obesidad con distintos grados de sensibilidad a insulina nos han permitido observar cambios en la expresión de LUM y COL-VI en relación con la obesidad y la IR (Guzman-Ruiz et al., 2020). En este contexto, el objetivo general de esta Tesis Doctoral se ha centrado en analizar la respuesta de los adipocitos a cambios en los componentes de la matriz extracelular, en particular de lumican y colágeno VI, que pueden definir o comprometer la función de estas células y la capacidad de expansión del tejido adiposo en condiciones de obesidad

Cluster Analysis of Variations in the Diurnal Pattern of Grass Pollen Concentrations in Northern Europe (Copenhagen) and Southern Europe (Córdoba)

From an allergological point of view, Poaceae pollen is one of the most important type of pollen that the population is exposed to in the ambient environment. There are several studies on intra diurnal patterns in grass pollen concentrations, and agreement on the high variability. However, the method for analysing the different patterns is not yet well established. The aim of the present study is therefore to examine the method of pattern analysis by statistical clustering, as well as relating the proposed patterns to time of season and meteorological variables at two highly different biogeographical locations; Córdoba, Spain and Copenhagen, Denmark. Airborne pollen is collected by Hirst type volumetric spore traps and counted using an optical microscope at both sites. The counts were converted to two-hours concentrations and a new method based on cluster analysis was applied with the aim of determining the most frequent diurnal patterns in pollen concentrations and their dependencies of site, season and meteorological variables. Three different well defined diurnal patterns were identified at both locations. The most frequent pattern in Copenhagen was associated with days having peak pollen concentrations in the evening (maximum between18h-20h), whereas the most frequent pattern at Córdoba was associated with days having peak pollen concentrations in the afternoon (maximum between 14h-16h). These three patterns account for 70% of days with no rain and pollen concentrations above 20 grains m-3. The most frequent pattern accounts for 40% and 57% of the days in Córdoba and Copenhagen respectively. The analysis clearly shows the great variation in pollen concentration pattern, albeit a dominating pattern can be found. It was not possible to explain all the differences in the patterns by the meteorological variables when examined individual. Clustering method is estimated to be an appropriate methodology for studying aerobiological phenomena with high variability

Mobile Learning Technologies for Education: Benefits and Pending Issues

Today’s world demands more efficient learning models that allow students to play a more active role in their education. Technology is having an impact on how instruction is delivered and how information is found and share. Until very recently, the educational models encouraged memorization as an essential learning skill. These days, technologies have changed the educational model and access to information. Knowledge is available online, mostly free, and easily accessible. Reading, sharing, listening and, doing are currently necessary skills for education. Mobile devices have become a complete set of applications, support, and help for educational organizations. By conducting an analysis of the behavior and use of mobile devices on current students, efficient educational applications can be developed. Although there are several initiatives for the use of mobile learning in education, there are also issues linked to this technology that must be addressed. In this work, we present the results of a literature review of mobile learning; the findings described are the result of the analysis of several articles obtained in three scientific repositories. This work also lists certain issues that, if properly addressed, can avoid possible complications to the implementation of this technology in education.This work was supported by the EduTech project (609785-EPP-1-2019-1-ES-EPPKA2-CBHEJP) co-funded by the Erasmus+ Programme of the European Union