Machine learning techniques to select Be star candidates. An application in the OGLE-IV Gaia south ecliptic pole field

Statistical pattern recognition methods have provided competitive solutions for variable star classification at a relatively low computational cost. In order to perform supervised classification, a set of features is proposed and used to train an automatic classification system. Quantities related to the magnitude density of the light curves and their Fourier coefficients have been chosen as features in previous studies. However, some of these features are not robust to the presence of outliers and the calculation of Fourier coefficients is computationally expensive for large data sets. We propose and evaluate the performance of a new robust set of features using supervised classifiers in order to look for new Be star candidates in the OGLE-IV Gaia south ecliptic pole field. We calculated the proposed set of features on six types of variable stars and on a set of Be star candidates reported in the literature. We evaluated the performance of these features using classification trees and random forests along with K-nearest neighbours, support vector machines, and gradient boosted trees methods. We tuned the classifiers with a 10-fold cross-validation and grid search. We validated the performance of the best classifier on a set of OGLE-IV light curves and applied this to find new Be star candidates. The random forest classifier outperformed the others. By using the random forest classifier and colour criteria we found 50 Be star candidates in the direction of the Gaia south ecliptic pole field, four of which have infrared colours consistent with Herbig Ae/Be stars. Supervised methods are very useful in order to obtain preliminary samples of variable stars extracted from large databases. As usual, the stars classified as Be stars candidates must be checked for the colours and spectroscopic characteristics expected for them

Validación y ajuste del modelo hidrogeológico conceptual de un humedal de la Llanura Pampeana, Provincia de Buenos Aires, Argentina

Comprender el funcionamiento hidrológico y la interacción de los diferentes cuerpos de agua presentes en un área específica son temas esenciales a la hora de planificar el uso racional del recurso hídrico. El objetivo de este trabajo es validar y ajustar el modelo hidrogeológico conceptual de un humedal de la llanura Pampeana Bonaerense mediante técnicas hidrogeoquími­cas e isotópicas. Se ha seleccionado la cuenca de la laguna La Brava (53.6 km2). La misma es una laguna permanente y somera con una superficie de 4.0 km2 y una profundidad máxima de 4.57 m. Se tomaron muestras para análisis fisicoquímico e isotópico en el agua subterránea, en la laguna y en los arroyos afluente y e.fluente a la misma. Para el muestreo en la laguna se diseñó una malla de muestreo regular en la cual se midieron in situ los principales parámetros fisicoquímicos a 5 profundidades diferentes y se tomaron muestras. La composición química del agua de la cuenca es de tipo bicarbonatada sódica. El carácter efluente-influente de este humedal pudo ser confirmado a través de las mediciones isotópicas e hidroquími­caso El análisis de la conductividad eléctrica en el humedal a diferentes profundidades hace pensar en una zona de recarga preferencial en el contacto de la laguna con el faldeo oriental de la Sierra La Brava, donde se evidencia una disminución importante de este parámetro. La información obtenida indica que la recarga al acu(fero en esta zona es influenciada por: la precipitación, la descarga proveniente del humedal, la concentración del escurrimiento superficial desde el frente montañoso hacia las depresiones interserranas y el aporte de agua proveniente del sistema de jisuras presente en las ortocuarcitas.Understanding the hydrological functioning and the interaction among the different water bodies present in a specific area are essential when planning the rational use of the hydric resource. The aim of the present paper is to validate and adjust the conceptual hydrogeological model for a wetland of the Buenos Aires Pampa Plain through hydrochemical and isotopic techniques. La Brava Wetland Basin (53.6 km2) has been selected. La Brava is a shallow and permanent wetland with an area of 4.0 km2 and a maximum depth of 4.57 m. Samples for physicochemical and isotopic analyses were taken from groundwater, the wetland, and in the inflow and outflow streams. A regular grid was designed for the wetland sampling to measure in situ the main physical and chemical parameters at 5 different depths. The chemical composition of the water in the basin is of sodium bicarbonate type. Hydrochemical and isotopic data allowed the confirmation of the effiuent-influent behavior of this wetland. Electrical conductivity analysis in the wetland at different depths shows a possible preferential recharge zone in the contact of the wetland with La Brava Hill, where an important decrease in this parameter was detected. The information obtained indicates that the recharge to the aquifer is influenced by: the rainfall, the wetland discharge, the concentration of surface ron-off from the range fringes to inter-range depressions and water input from the fault system present in the quartzites

Neutron Transfer reactions induced by 8Li on 9Be

Angular distributions for the elastic scattering of 8Li on 9Be and the neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for 8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR

Efficacy of Controlled Memory and Shape Memory Nickel Titanium Instruments in Removing Filling Material from Severely Curved Root Canals: An Ex Vivo Study

Introduction: The aim of the present study was to compare the efficacy of four NiTi instruments with different properties (shape memory and control memory), in both rotary and reciprocating motions, during retreatment procedures. Methods and Materials: Mesial canals of thirty-two mandibular molars were instrumented, obturated, and then scanned with” Cone-beam Computed Tomography” (CBCT). Teeth were randomly divided into 4 groups (n=8) according to each system: “Shape Memory” (SM) instruments including Reciproc (R25 file) and ProTaper Next (X3 and X2 file), “Controlled Memory” (CM) instruments including WaveOne Gold (Primary file) and Hyflex (30.06 and 25.06 file). The specimens were rescanned after retreatment procedures. The volume of the residual material left inside the canals, the operating time and the fractured files were analyzed. ANOVA and student t-tests were used for statistical analysis. Results: There were no significant differences in the percentage of the residual filling material or requiring time amongst different groups of instruments (P>0.05). However, CM instruments presented the highest frequency of fractured files [2 SM instruments (12.5%) and 7 CM instruments (43.75%)] with a significant difference (P=0.023). Conclusions: This ex vivo study showed that CM and SM instruments can remove filling materials from mandibular mesial root canals during retreatment procedures; nonetheless the CM instruments had a higher frequency of fractured files. No system was able to completely remove the filling materials. Therefore, additional procedures and techniques are needed to improve root canal cleanliness. Keywords: Endodontics; Retreatment; Root Canal Preparation; Tooth Roo

Lactation curve model by lactation number in murciano-granadina goats

In this work four lactation curve models have been tested: The simple lineal regression pattern; the quadratic pattern; the Cobby and Le Du pattern; and the incomplete gamma of Wood function. As base of information we have used the historical file of controls carried out in the Milking Control Nucleus of Granada belonging to the National Association of Breeders of Murciano-Granadina Goat Breed, during the years 1990 to 2004, what supposes a total of 85235 controls made on 10351 goats belonging to 117 farms. The lactation curves has been studied in function of the lactation number. The lactations were standardized to 240 days. For the fitting of models we have used the NLIN procedure of SAS. For all the models, independently of the lactation number, R2 oscillated between 0.84 and 0.85. For the controls made in first, second and third lactation the Incomplete Gamma of Wood function shown the best fitting (smallest value of mean square error).En este trabajo se han utilizado cuatro modelos, uno de ellos el modelo de regresión lineal simple, el modelo cuadrático, el modelo de Cobby y Le Du y la función gamma incompleta de Wood. Como base de información se ha utilizado el archivo histórico de los controles realizados en el Núcleo de Control Lechero de Granada (Núcleo Nacional Número 362) perteneciente a la Asociación Nacional de Criadores de Caprino de Raza Murciano-Granadina, durante los años comprendidos entre 1990 y 2004, lo que supone un total de 85235 controles efectuados sobre 10351 cabras pertenecientes a 117 ganaderías. Se ha estudiado la curva de la lactación en función del número de lactación para lactaciones estandarizadas a 240 días. Para el ajuste de los modelos se utilizó el procedimiento NLIN de SAS. Para todos los modelos independientemente del número de lactación obtuvieron R2 que oscilaron entre 0,84 y 0,85. Para los controles efectuados en primera, segunda y tercera lactación el modelo de curva Gamma Incompleta de Wood obtuvo el mejor ajuste (menor valor de cuadrado medio del error)