Calibration of BVRI Photometry for the Wide Field Channel of the HST Advanced Camera for Surveys

We present new observations of two Galactic globular clusters, PAL4 and PAL14, using the Wide-Field Channel of the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST), and reanalyze archival data from a third, NGC2419. We matched our photometry of hundreds of stars in these fields from the ACS images to existing, ground-based photometry of faint sequences which were calibrated on the standard BVRI system of Landolt. These stars are significantly fainter than those generally used for HST calibration purposes, and therefore are much better matched to supporting precision photometry of ACS science targets. We were able to derive more accurate photometric transformation coefficients for the commonly used ACS broad-band filters compared to those published by Sirianni, et al. (2005), owing to the use of a factor of several more calibration stars which span a greater range of color. We find that the inferred transformations from each cluster individually do not vary significantly from the average, except for a small offset of the photometric zeropoint in the F850LP filter. Our results suggest that the published prescriptions for the time-dependent correction of CCD charge-transfer efficiency appear to work very well over the ~3.5 yr interval that spans our observations of PAL4 and PAL14 and the archived images of NGC2419.Comment: 22 pages, 12 figures. Accepted for publication in PAS

LSST optical beam simulator

We describe a camera beam simulator for the LSST which is capable of illuminating a 60mm field at f/1.2 with realistic astronomical scenes, enabling studies of CCD astrometric and photometric performance. The goal is to fully simulate LSST observing, in order to characterize charge transport and other features in the thick fully depleted CCDs and to probe low level systematics under realistic conditions. The automated system simulates the centrally obscured LSST beam and sky scenes, including the spectral shape of the night sky. The doubly telecentric design uses a nearly unit magnification design consisting of a spherical mirror, three BK7 lenses, and one beam-splitter window. To achieve the relatively large field the beam-splitter window is used twice. The motivation for this LSST beam test facility was driven by the need to fully characterize a new generation of thick fully-depleted CCDs, and assess their suitability for the broad range of science which is planned for LSST. Due to the fast beam illumination and the thick silicon design [each pixel is 10 microns wide and over 100 microns deep] at long wavelengths there can be effects of photon transport and charge transport in the high purity silicon. The focal surface covers a field more than sufficient for a 40x40 mm LSST CCD. Delivered optical quality meets design goals, with 50% energy within a 5 micron circle. The tests of CCD performance are briefly described.Comment: 9 pages, 9 figure

Modeling the Transmission Dynamics of Typhoid in Malaria Endemic Settings

Typhoid and malaria co-infection is a major public health problem in many developing countries. In this paper, a deterministic model for malaria and typhoid co-infection is proposed and analyzed. It has been established that the model exhibits a backward bifurcation phenomenon. Overall, the study reveals that a typhoid outbreak in malaria endemic settings may lead to higher cumulative cases of dually-infected individuals displaying clinical symptoms of both infections than singly-infected individuals displaying clinical symptoms of either malaria or typhoid

Comparative Analysis of Extrusion Processes by Finite Element Analysis

AbstractExtrusion processes are quite extended in the manufacturing of long products for a wide range of industrial applications. There are different approaches of extrusion processes, depending on either the final shape of the product to obtain or the maximum loading capacity of the equipment to be used. This work presents a comparative study of extrusion processes (solid and cup extrusion), considering both direct and indirect forming conditions and showing the most interesting differences between them. The comparison is realized by Finite Element simulation of the processes, using the code DEFORM F2. The material is a low carbon steel (AISI-1010) and the same extrusion ratio and ram displacement are considered in all cases. By comparing the required forces it can be concluded that required loads are higher in cup extrusion processes than in solid extrusion ones. Regarding the friction load, the maximum contribution due to the die-billet contact in cup extrusion is much higher than in the case of solid extrusion. On the contrary, the maximum friction load contribution due to the container wall is much higher in the case of solid extrusion than in cup extrusion

Pensamiento matemático y creatividad a través de la invención y resolución de problemas matemáticos

This work shows the relationship between the development of mathematical thinking and creativity with mathematical problem posing and solving. Creativity and mathematics are disciplines that do not usually appear together. Both concepts constitute complex processes sharing elements, such as fluency (number of ideas), flexibility (range of ideas), novelty (unique idea) and elaboration (idea development). These factors contribute, among others, to the fact that schoolchildren are competent in mathematics. The problem solving and posing are a very powerful evaluation tool that shows the mathematical reasoning and creative level of a person. Creativity is part of the mathematics education and is a necessary ingredient to perform mathematical assignments. This contribution presents some important research works about problem posing and solving related to the development of mathematical knowledge and creativity. To that end, it is based on various beliefs reflected in the literature with respect to notions of creativity, problem solving and posing.En este trabajo se muestra la relación entre el desarrollo del pensamiento matemático y la creatividad con la invención y resolución de problemas matemáticos. No son frecuentes las ocasiones en las que aparecen juntas Creatividad y Matemáticas. Ambas constituyen procesos complejos que comparten elementos como la fluidez (número de ideas), la flexibilidad (variedad de ideas), la novedad (idea única) y la elaboración (desarrollar una idea). Estos factores contribuyen, entre otras cosas, a que los escolares sean competentes en matemáticas. La invención y la resolución de problemas resultan ser un instrumento evaluador muy potente con el que se pone de manifiesto el nivel de razonamiento matemático y creativo de una persona. La creatividad forma parte de la educación matemática y constituye un ingrediente necesario para realizar las tareas matemáticas. Esta aportación presenta algunas investigaciones relevantes, que se han llevado a cabo sobre invención y resolución de problemas, vinculadas al desarrollo del conocimiento matemático y a la creatividad. Para ello se parte de las distintas creencias que se recogen en la literatura referente a las nociones de creatividad, invención de problemas y resolución de problemas

Pensamiento matemático y creatividad a través de la invención y resolución de problemas matemáticos

This work shows the relationship between the development of mathematical thinking and creativity with mathematical problem posing and solving. Creativity and mathematics are disciplines that do not usually appear together. Both concepts constitute complex processes sharing elements, such as fluency (number of ideas), flexibility (range of ideas), novelty (unique idea) and elaboration (idea development). These factors contribute, among others, to the fact that schoolchildren are competent in mathematics. The problem solving and posing are a very powerful evaluation tool that shows the mathematical reasoning and creative level of a person. Creativity is part of the mathematics education and is a necessary ingredient to perform mathematical assignments. This contribution presents some important research works about problem posing and solving related to the development of mathematical knowledge and creativity. To that end, it is based on various beliefs reflected in the literature with respect to notions of creativity, problem solving and posing.En este trabajo se muestra la relación entre el desarrollo del pensamiento matemático y la creatividad con la invención y resolución de problemas matemáticos. No son frecuentes las ocasiones en las que aparecen juntas Creatividad y Matemáticas. Ambas constituyen procesos complejos que comparten elementos como la fluidez (número de ideas), la flexibilidad (variedad de ideas), la novedad (idea única) y la elaboración (desarrollar una idea). Estos factores contribuyen, entre otras cosas, a que los escolares sean competentes en matemáticas. La invención y la resolución de problemas resultan ser un instrumento evaluador muy potente con el que se pone de manifiesto el nivel de razonamiento matemático y creativo de una persona. La creatividad forma parte de la educación matemática y constituye un ingrediente necesario para realizar las tareas matemáticas. Esta aportación presenta algunas investigaciones relevantes, que se han llevado a cabo sobre invención y resolución de problemas, vinculadas al desarrollo del conocimiento matemático y a la creatividad. Para ello se parte de las distintas creencias que se recogen en la literatura referente a las nociones de creatividad, invención de problemas y resolución de problemas

Recyclable supported Pd-NHC catalytic systems for the copper free Sonogashira cross-coupling in flow

A new family of well-defined NHC-Pd complexes immobilised onto silica, alumina and titania is reported. The catalysts display activity and recyclability in the Sonogashira cross-coupling reactions under batch and continuous flow conditions. Under batch conditions the new catalytic systems were recycled up to four times with yields over 80%. These catalysts have a broad substrate scope of different aryl bromides and alkynes. The titania-supported catalysts show good conversions under continuous flow conditions at least over 8 hours on stream using MeOH as solvent.The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (EC FP7) Grant Agreement n. [NMP2-SL-2012-280827]. The authors are grateful to TECSPR14-1-0045; TECNIOspring programme, the Agency for Business Competitiveness of the Government of Catalonia, ACCIÓ, the Generalitat de Catalunya (2014SGR670). and the Spanish Ministerio de Economía y Competitividad (CTQ2016-75016-R) for financial support

Variables predictors of the set in the defence complex in volleyball

El objetivo de la investigación fue conocer las variables predictoras de la eficacia de colocación en el complejo de defensa (KII), en ambos géneros, en categorías de formación. La muestra del estudio estuvo compuesta por 2.404 acciones de juego, 1.104 en género masculino y 1.300 en género femenino, desarrolladas por los 34 equipos participantes en el Campeonato de España Under 16. La variable dependiente fue la eficacia de colocación. Las variables independientes se agruparon en: variables de defensa, de colocación en KII y de bloqueo. Los resultados determinaron que, en ambos géneros, la eficacia de defensa, la técnica de colocación y la participación en bloqueo predecían la eficacia de la colocación; en género masculino, zona de defensa y tiempo de colocación; ninguna variable fue predictora únicamente en género femenino. Esta información puede ser relevante para el desarrollo del proceso de entrenamiento en voleibolThe objective of the research was to analyse the variables predictors of the setting efficacy in the defence complex (KII), in youth athlete, in both genders. The study sample was comprised of 2404 game actions, 1104 in the male gender and 1300 in the female gender. The actions were carried out by the 34 teams that participated in the Spanish Under-16 Championship. The dependant variable was the setting efficacy. The results determined that, in both genders, the dig efficacy, setting technique and the participation in block predicted the setting efficacy; in male gender, the defence zone and tempo of set; no predictor variables were exclusive to the female gender. This information may be relevant when developing training processes in volleyballEste estudio se ha realizado gracias a la aportación de la Consejería de Economía e Infraestructuras de la Junta de Extremadura a través del Fondo Europeo de Desarrollo Regiona

Photometry and spectroscopy of faint candidate spectrophotometric standard DA white dwarfs

We present precise photometry and spectroscopy for 23 candidate spectrophotometric standard white dwarfs. The selected stars are distributed in the Northern hemisphere and around the celestial equators and are all fainter than r ~ 16.5 mag. This network of stars, when established as standards, together with the three Hubble Space Telescope primary CALSPEC white dwarfs, will provide a set of spectrophotometric standards to directly calibrate data products to better than 1%. These new faint standard white dwarfs will have enough signal-to-noise ratio in future deep photometric surveys and facilities to be measured accurately while still avoiding saturation in such surveys. They will also fall within the dynamic range of large telescopes and their instruments for the foreseeable future. This paper discusses the provenance of the observational data for our candidate standard stars. The comparison with models, reconciliation with reddening, and the consequent derivation of the full spectral energy density distributions for each of them is reserved for a subsequent paper.Comment: 31 pages, 17 figures, 10 tables, ApJ in press (accepted on December 23rd, 2018