High resolution observations of the outer disk around T Cha: the view from ALMA

T Cha is a young star surrounded by a transitional disk with signatures of planet formation. We have obtained high-resolution and high-sensitivity ALMA observations of T Cha in the ${\rm CO}(3$--$2)$, ${\rm ^{13}CO}(3$--$2)$, and ${\rm CS}(7$--$6)$ emission lines to reveal the spatial distribution of the gaseous disk around the star. In order to study the dust within the disk we have also obtained continuum images at 850$\mu$m from the line-free channels. We have spatially resolved the outer disk around T Cha. Using the CO(3-2) emission we derive a radius of $\sim$230 AU. We also report the detection of the $^{13}$CO(3-2) and the CS(7-8) molecular emissions, which show smaller radii than the CO(3-2) detection. The continuum observations at 850$\mu$m allow the spatial resolution of the dusty disk, which shows two emission bumps separated by $\sim$40AU, consistent with the presence of a dust gap in the inner regions of the disk, and an outer radius of $\sim$80AU. Therefore, T Cha is surrounded by a compact dusty disk and a larger and more diffuse gaseous disk, as previously observed in other young stars. The continuum intensity profiles are different at both sides of the disk suggesting possible dust asymmetries. We derive an inclination of i(deg)=67$\pm$5, and a position angle of PA (deg)= 113$\pm$6, for both the gas and dust disks. The comparison of the ALMA data with radiative transfer models shows that the gas and dust components can only be simultaneously reproduced when we include a tapered edge prescription for the surface density profile. The best model suggests that most of the disk mass is placed within a radius of $R<$ 50AU. Finally, we derive a dynamical mass for the central object of $M_{*}$=1.5$\pm$0.2M$_{\odot}$, comparable to the one estimated with evolutionary models for an age of $\sim$10Myr.Comment: 5 pages, 5 figures, accepted for publication in A&A Letter

Leydig Cell Tumor of the Ovary. A Rare Case of Hyperandrogenism

Os tumores ováricos secretores de androgénios são raros constituindo cerca de 1% de todas as neoplasias do ovário. Descreve-se o caso clínico de uma doente do sexo feminino, 67 anos de idade, que recorre à consulta por queixas de hirsutismo (score 23) e alopécia com padrão androgenético A avaliação laboratorial revelou níveis séricos elevados de testosterona. A ecografia ginecológica por via transvaginal permitiu identificar a presença de um nódulo sólido no ovário esquerdo com características imagiológicas sugestivas de malignidade pelo que, a doente foi submetida a ooforectomia bilateral. O exame histopatológico revelou a presença de células de Leydig. O seguimento clínico posterior da doente permitiu constatar melhoria do quadro clínico e normalização dos níveis séricos de testosterona

Bessel-Gauss beams of arbitrary integer order: propagation profile, coherence properties and quality factor

We present a novel approach to generate Bessel-Gauss modes of arbitrary integer order and well-defined optical angular momentum in a gradient index medium of transverse parabolic profile. The propagation and coherence properties, as well as the quality factor, are studied using algebraic techniques that are widely used in quantum mechanics. It is found that imposing the well-defined optical angular momentum condition, the Lie group $SU(1,1)$ comes to light as a characteristic symmetry of the Bessel-Gauss beams.Comment: 24 pages, 12 figure

Biomechanics of fish swimming in a hydrokinetic turbine wake

In the present paper, the assessment of the hydrodynamics of the fish swimming in undisturbed and altered wake-flow is carried out identifying hydrodynamical forces and flow patterns of the fish swimming wake. URANS approach with k-omega/SST turbulence model are employed combining fish and turbine in the same simulation. Fish motion is realized using dynamically adaptive mesh. The actuator line method is employed to induce the wake of a hydrokinetic turbine, which is a simplified method that requires lower computational cost than full geometry simulations. This work brings a new numerical approach involving fish and turbine wake highlighting that fish swimming in the wake presents higher thrust forces than in the undisturbed flow, due to the x-component to velocity in the wake is lower than free flow velocity

Los Problemas de Olimpiadas de Matemáticas. Un Recurso para Atender las Aptitudes Sobresalientes

The assessment of the diversity to which the most genuine human feeling summons us and for which fortunately the educational policy of Mexico and most of the countries are currently committed under the paradigm of Inclusive Education, constitutes one of the biggest challenges facing teachers today. Responding fairly to the characteristics, needs, interests, abilities, skills, and learning styles of each and every student requires that teachers, especially those who teach mathematics, make every effort and develop capabilities. In this effort, given the complexity of the task due to the necessary compliance with times and the number of diverse students to be intervened by Basic Education teachers, not few times those capacities that allow them go to the background in their management meet the demands of students with outstanding mathematical aptitudes, which frequently leads to the loss of student interest. Taking into account this panorama of the classroom reality, it is outlined as desirable for the teacher to have pragmatic and easily accessible intervention alternatives. In this way, the author of this Professional Development Project oriented his training towards the study of a successful afterschool environment in the potentialization of mathematical talent, the mathematical olympics. The general objective to follow was to recognize the qualities of the mathematical olympics as a transforming activity of the high intellectual and creative natural capacities in mathematical talent. For their development, a field research was carried out at a descriptive level, using observation in two stages as the main method, the second edition of the course for Mathematical Olympics coaches sponsored by the Center for High Performance in Mathematics (CARMA is the acronym in Spanish) and the training of the Zacatecan elementary school and junior high school preselective for their participation in the 2020 Mathematical Olympics. Through the results, it was possible to collect and organize plenty material representative of the implicit content in the problems of the competitions for elementary school and junior high school levels, as well as the practices that coaches implement for their teaching. Based on those results, it was possible to conclude with the recognition of the determining qualities in the accomplishment of learning in this extracurricular environment, qualities that consequently adapted can be retaken for effective intervention in order to potentiate mathematical talent from school.La valoración de la diversidad a la que nos convoca el más genuino sentimiento humano y por la que afortunadamente se apuesta desde la política educacional de México y de la mayoría de los países en la actualidad, bajo el paradigma de la Educación Inclusiva, constituye uno de los mayores desafíos a los que se enfrentan los docentes de hoy día. El responder con equidad a las características, necesidades, intereses, capacidades, habilidades y estilos de aprendizaje de todos y cada uno de los educandos requiere que los maestros, en especial los que se dedican a la enseñanza de las matemáticas, pongan todo el empeño y desarrollen capacidades. Dada la complejidad que supone la tarea por el necesario cumplimiento con tiempos y la cantidad de alumnos diversos a intervenir por los docentes de la Educación Básica, en este esfuerzo no pocas veces pasan a un segundo plano en su gestión aquellas capacidades que le permiten satisfacer las demandas de los alumnos con aptitudes sobresalientes para las matemáticas, lo que frecuentemente conlleva a la pérdida del interés de estos educandos. Teniendo en cuenta este panorama de la realidad áulica, se perfila como deseable que el docente cuente con alternativas de intervención pragmáticas y de fácil acceso. En este tenor, el autor del presente Proyecto de Desarrollo Profesional orientó su capacitación hacia el estudio de un medio extraescolar exitoso en la potencialización de talento matemático: las olimpiadas matemáticas. El objetivo general perseguido fue el identificar aspectos de las olimpiadas matemáticas como actividad transformadora de las altas capacidades naturales intelectuales y creativas en talento matemático. Para su desarrollo se llevó a cabo una investigación de campo de tipo descriptivo, utilizando como método principal la observación en dos escenarios: la segunda edición del Curso para Entrenadores de Olimpiadas Matemáticas auspiciado por el Centro de Alto Rendimiento en Matemáticas (CARMA) y los entrenamientos del preselectivo zacatecano de primaria y secundaria para su participación en las olimpiadas matemáticas de 2020. Como expresión de los resultados se logró recopilar y organizar abundante material representativo del contenido implícito en los problemas de las competiciones para los niveles de primaria y secundaria, así como de las prácticas que implementan los entrenadores para su enseñanza. Sobre la base de tales resultados se pudo concluir con la identificación de los aspectos determinantes en el logro de aprendizaje en este medio extraescolar, aspectos que consecuentemente adaptados pueden ser retomadas para la intervención efectiva en pos de potencializar el talento matemático desde la escuela

Constraints on the frequency and mass content of r-process events derived from turbulent mixing in galactic disks

Metal-poor stars in the Milky Way (MW) halo display large star-to-star dispersion in their r-process abundance relative to lighter elements. This suggests a chemically diverse and unmixed interstellar medium (ISM) in the early Universe. This study aims to help shed light on the impact of turbulent mixing, driven by core collapse supernovae (cc-SNe), on the r-process abundance dispersal in galactic disks. To this end, we conduct a series of simulations of small-scale galaxy patches which resolve metal mixing mechanisms at parsec scales. Our set-up includes cc-SNe feedback and enrichment from r-process sources. We find that the relative rate of the r-process events to cc-SNe is directly imprinted on the shape of the r-process distribution in the ISM with more frequent events causing more centrally peaked distributions. We consider also the fraction of metals that is lost on galactic winds and find that cc-SNe are able to efficiently launch highly enriched winds, especially in smaller galaxy models. This result suggests that smaller systems, e.g. dwarf galaxies, may require higher levels of enrichment in order to achieve similar mean r-process abundances as MW-like progenitors systems. Finally, we are able to place novel constraints on the production rate of r-process elements in the MW, $6 \times 10^{-7} {M_\odot / \rm yr} \lesssim \dot{m}_{\rm rp} \ll 4.7 \times 10^{-4} {M_\odot / \rm yr}$, imposed by accurately reproducing the mean and dispersion of [Eu/Fe] in metal-poor stars. Our results are consistent with independent estimates from alternate methods and constitute a significant reduction in the permitted parameter space.Comment: 20 pages, 12 figures, 3 appendices. Accepted for publication in The Astrophysical Journa

Space--time fluctuations and the spreading of wavepackets

Using a density matrix description in space we study the evolution of wavepackets in a fluctuating space-time background. We assume that space-time fluctuations manifest as classical fluctuations of the metric. From the non-relativistic limit of a non-minimally coupled Klein-Gordon equation we derive a Schr\"odinger equation with an additive gaussian random potential. This is transformed into an effective master equation for the density matrix. The solutions of this master equation allow to study the dynamics of wavepackets in a fluctuating space-time, depending on the fluctuation scenario. We show how different scenarios alter the diffusion properties of wavepackets.Comment: 11 page

Type-I alignment in MAPbI3 based solar devices with doped-silicon nanocrystals

In this work we couple silicon nanocrystals (Si NCs) with strong quantum confinement (< 4 nm diameter) with large grained MAPbI3 films combining the perovskites excellent transport properties with the unique opto-electronic properties of quantum confined Si NCs. The electronic structures of MAPbI3 and Si NCs, ideally aligned to form a type-I heterojunction, demonstrated improved carrier collection through a higher short-circuit current density (~ 20 mA cm−2) measured in photovoltaic test devices. The addition of p- and n-doped Si NCs within the MAPbI3 films also showed unexpected and interesting device performance improvements, where the typical perovskite degradation process in ambient conditions was considerably slowed down and the overall device efficiency was observed to increase under light soaking. We attribute these improvements to the presence of Si NCs, which helped maintain the perovskite film qualities for more than 14 days in open atmosphere

Measuring Cosmological Parameters with the JVAS and CLASS Gravitational Lens Surveys

The JVAS (Jodrell Bank-VLA Astrometric Survey) and CLASS (Cosmic Lens All-Sky Survey) are well-defined surveys containing about ten thousand flat-spectrum radio sources. For many reasons, flat-spectrum radio sources are particularly well-suited as a population from which one can obtain unbiased samples of gravitational lenses. These are by far the largest gravitational (macro)lens surveys, and particular attention was paid to constructing a cleanly-defined sample for the survey itself and for the underlying luminosity function. Here we present the constraints on cosmological parameters, particularly the cosmological constant, derived from JVAS and combine them with constraints from optical gravitational lens surveys, `direct' measurements of $\Omega_{0}$, $H_{0}$ and the age of the universe, and constraints derived from CMB anisotropies, before putting this final result into the context of the latest results from other, independent cosmological tests.Comment: LaTeX, 9 pages, 6 PostScript figures, uses texas.sty. To appear in the Proceedings of the 19th Texas Symposium on Relativistic Astrophysics and Cosmology (CD-ROM). Paper version available on request. Actual poster (A0 and A4 versions) available from http://multivac.jb.man.ac.uk:8000/helbig/research/publications/info/ texas98.htm