Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*

Context. The discovery of pulsations in low-mass stars opens an opportunity for probing their interiors and to determine their evolution, by employing the tools of asteroseismology. Aims. We aim to analyze high-speed photometry of SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25 and discover brightness variabilities. In order to locate these stars in the $T_{\rm eff} - \log g$ diagram we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods. To carry out this study, we used the photometric data obtained by us for these stars with the 2.15m telescope at CASLEO, Argentina. We analyzed their light curves and we apply the Discrete Fourier Transform to determine the pulsation frequencies. Finally, we compare both stars in the $T_{\rm eff} - \log g$ diagram, with known two pre-white dwarfs, seven pulsating pre-ELM white dwarf stars, $\delta$ Scuti and SX Phe stars. Results. We report the discovery of pulsations in SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25. We determine their effective temperature and surface gravity to be $T_{\rm eff}$ = 7 972 $\pm$ 200 K, $\log g$ = 4.25 $\pm$ 0.5 and $T_{\rm eff}$ = 7 925 $\pm$ 200 K, $\log g$ = 4.25 $\pm$ 0.5, respectively. With these parameters these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ~ 0.17 Mo) or more massive SX Phe stars. We identified pulsation periods of 3 278.7 and 1 633.9 s for SDSSJ145847.02$+$070754.46 and a pulsation period of 3 367.1 s for SDSSJ173001.94$+$070600.25. These two new objects together with those of Maxted et al. (2013, 2014) indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded.Comment: 5 pages, 5 figures, 1 table, accepted for publication in A&A

Testing White Dwarf Crystallization Theory with Asteroseismology of the Massive Pulsating DA Star BPM 37093

It was predicted more than 40 years ago that the cores of the coolest white dwarf stars should eventually crystallize. This effect is one of the largest sources of uncertainty in white dwarf cooling models, which are now routinely used to estimate the ages of stellar populations in both the Galactic disk and the halo. We are attempting to minimize this source of uncertainty by calibrating the models, using observations of pulsating white dwarfs. In a typical mass white dwarf model, crystallization does not begin until the surface temperature reaches 6000-8000 K. In more massive white dwarf models the effect begins at higher surface temperatures, where pulsations are observed in the ZZ Ceti (DAV) stars. We use the observed pulsation periods of BPM 37093, the most massive DAV white dwarf presently known, to probe the interior and determine the size of the crystallized core empirically. Our initial exploration of the models strongly suggests the presence of a solid core containing about 90% of the stellar mass, which is consistent with our theoretical expectations.Comment: minor changes for length, accepted for ApJ Letter

Evidence For Temperature Change And Oblique Pulsation From Light Curve Fits Of The Pulsating White Dwarf GD 358

Convective driving, the mechanism originally proposed by Brickhill for pulsating white dwarf stars, has gained general acceptance as the generic linear instability mechanism in DAV and dbV white dwarfs. This physical mechanism naturally leads to a nonlinear formulation, reproducing the observed light curves of many pulsating white dwarfs. This numerical model can also provide information on the average depth of a star's convection zone and the inclination angle of its pulsation axis. In this paper, we give two sets of results of nonlinear light curve fits to data on the dbV GD 358. Our first fit is based on data gathered in 2006 by the Whole Earth Telescope; this data set was multiperiodic containing at least 12 individual modes. Our second fit utilizes data obtained in 1996, when GD 358 underwent a dramatic change in excited frequencies accompanied by a rapid increase in fractional amplitude; during this event it was essentially monoperiodic. We argue that GD 358's convection zone was much thinner in 1996 than in 2006, and we interpret this as a result of a short-lived increase in its surface temperature. In addition, we find strong evidence of oblique pulsation using two sets of evenly split triplets in the 2006 data. This marks the first time that oblique pulsation has been identified in a variable white dwarf star.Delaware Asteroseismic Research CenterNational Science Foundation AST-0909107, AST-0607840Norman Hackerman Advanced Research Program 003658-0255-2007Crystal Trust FoundationMt. Cuba ObservatoryUniversity of DelawareAstronom

Continuous macroscopic limit of a discrete stochastic model for interaction of living cells

In the development of multiscale biological models it is crucial to establish a connection between discrete microscopic or mesoscopic stochastic models and macroscopic continuous descriptions based on cellular density. In this paper a continuous limit of a two-dimensional Cellular Potts Model (CPM) with excluded volume is derived, describing cells moving in a medium and reacting to each other through both direct contact and long range chemotaxis. The continuous macroscopic model is obtained as a Fokker-Planck equation describing evolution of the cell probability density function. All coefficients of the general macroscopic model are derived from parameters of the CPM and a very good agreement is demonstrated between CPM Monte Carlo simulations and numerical solution of the macroscopic model. It is also shown that in the absence of contact cell-cell interactions, the obtained model reduces to the classical macroscopic Keller-Segel model. General multiscale approach is demonstrated by simulating spongy bone formation from loosely packed mesenchyme via the intramembranous route suggesting that self-organizing physical mechanisms can account for this developmental process.Comment: 4 pages, 3 figure

Design and Performance Analysis of 250 kW Grid-Connected Photovoltaic System in Iraqi Environment Using PVsyst Software

A 250 kW grid-connected photovoltaic (PV) plant systems have been installed at the Ministry of Electricity in Baghdad and penetrated to the Iraqi national grid since November 2017. This is the first high power grid-connected PV system that has been installed in Iraq and it’s one of the four parts 1MW large-scale PV systems that should be completed in early of 2019. This paper presents the design and performance analysis of this system using a PVsyst software package. The performance ratio and different losses that occurred in the system are also calculated. The results show that the performance ratio is 75% using 1428 photovoltaic panels type (Sharp 175Wp) spread over an area of 1858 m². The total energy injected into the grid is (346692 kWh/year) .Based on the simulation results that developed in this paper, the practical PV grid-tied system has been implemented in Baghdad site

Hypertension Prevalence, Awareness, Treatment and Control, and Associated Factors: Results from a National Survey, Jordan

The study examined prevalence, awareness, treatment and control of hypertension (HTN), and associated factors and to evaluate the trend in hypertension between 2009 (period 2) and 1994–1998 (period 1). A national sample of 4117 adults aged 25 years and older was selected. Prevalence rate of HTN (SBP ≥ 140 or DBP ≥ 90 or on antihypertensive therapy) was 32.3% and was higher than the 29.4% prevalence rate reported in period 1. Prevalence rate was significantly higher among males, older age groups, least educated, obese, and diabetics than their counterparts. The rate of awareness among hypertensives was 56.1% and was higher than the 38.8% rate reported form period 1 data. Awareness was positively associated with age, smoking, and diabetes for both men and women, and with level of education and body mass index for men. Rate of treatment for HTN among aware patients was 63.3% and was significantly higher than the 52.8% rate reported in period1. Control rate of HTN among treated hypertensives was 39.6%; significantly higher than the 27.9% control rate in period 1. Control of HTN was positively associated with age but only for women. In conclusion, HTN is still on the rise in Jordan, and levels of awareness and control are below the optimal levels

Revisiting the anatomy of the cephalic vein, its origin, course and possible clinical correlations in relation to the anatomical snuffbox among Jordanian

Background: The cephalic vein is one of the most distinguished superficial veins of the upper limb. Its clinical value lies in venous access. There is little known about the variation of its formation in relation to the anatomical snuffbox. Hence, anatomical variants in the origin of the cephalic vein are important in clinical practice. Subsequently, this study was designed to examine the variation of the cephalic vein formation in relation to the anatomical snuffbox. Materials and methods: A cross-sectional study of 438 subjects (722 hands), was prepared to study the cephalic vein among Jordanian students and staff of one of the major governmental Medical College in Jordan, by using infrared illumination system. The obtained data was analysed according to; gender, sidedness, and handedness. Results: Four sites for the formation of the cephalic vein in relation to the anatomical snuffbox were found. There was a significant relation between gender and sidedness, and the sites of formation of the cephalic vein (p < 0.0001 and p = 0.048, respectively). Conclusions: For the first time this study identified different sites for the formation of the cephalic vein in relation to the anatomical snuffbox. However, regardless of its sites of formation, the cephalic vein was running in 98% of the examined hands in the anatomical snuffbox

Primeras curvas de luz de estrellas variables ZZ Ceti observadas en el CASLEO

Las estrellas enanas blancas DA variables, o ZZ Ceti, constituyen la familia de enanas blancas pulsantes más numerosa. A partir del advenimiento del Sloan Digital Sky Survey (SDSS) el número de objetos conocidos de esta clase se elevó a 160. Estas estrellas poseen atmósferas ricas en Hidrógeno y se localizan en un rango de temperaturas efectivas entre 10500 y 12300 K. La astrosismología de enanas blancas permite extraer información acerca de la estructura interna y las propiedades globales de estos objetos compactos y antiguos. Esta técnica consiste básicamente en la comparación de los peréodos de pulsación observados con períodos calculados a partir de modelos teóricos representativos. En este trabajo presentamos las primeras curvas de luz resultantes de datos fotométricos de estrellas enanas blancas candidatas a ser variables ZZ Ceti, obtenidos con el telescopio de 2.15 m del CASLEO. Se incluyen también, nuevos peréodos de pulsación y parámetros físicos derivados para las enanas blancas pulsantes ya conocidas: BPM37093, L19-2 y PG1159-035, entre otras.DA white dwarf stars, ZZ Ceti, are the most numerous class among the pulsating white dwarfs. These stars have atmospheres dominated by hydrogen, and effective temperatures between 10500 and 12300 K. Because of the periodic variations of their luminosity, we can use asteroseismology to study the inner structure and the global properties of these compact and old objects. These techniques basically consists on the comparison between the observed pulsation periods and theoretical periods computed from representative models. In this work we present the first light curves and Fourier transforms of the ZZ Ceti stars WD162813+122452 y BPM37093, obtained with the 2,15 m telescope at CASLEO. Observational data and physical parameters derived for some ZZ Ceti observed candidates are also included.Fil: Corti, Mariela A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto Argentino de Radioastronomia (i); Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Romero, Alejandra D.. Universidade Federal do Rio Grande do Sul; BrasilFil: Kanaan, Antonio. Universidade Federal Da Santa Catarina; BrasilFil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; BrasilFil: Costa, J. E.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Córsico, Alejandro H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Althaus, Leandro G.. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina; Argentin