463 research outputs found
A Search for Radio Emission at the Bottom of the Main Sequence and Beyond
We have used the VLA to conduct a deep search for 3.6 cm radio emission from
nearby very low mass stars and brown dwarfs. The Gudel-Benz relation is used to
predict radio luminosities for some very low mass stars and candidate brown
dwarfs with measured X-ray fluxes. The predicted radio fluxes are quite small,
whereas the measured radio flux from the brown dwarf candidate Rho Oph GY 31 is
relatively strong. In light of our new observations, this object remains an
anomaly. We present upper limits for our measured radio fluxes at 3.6 cm for
our targets.Comment: 10 pages, no figures. Accepted for publication in A
Influence of Behavioural Training on Interpersonal Competence with Reference to Generation X Managers
âGeneration Xâ is phrase that has gained entry into modern management literature. Generation X managers are expected to shoulder leadership responsibilities to steer future organizations towards excellence. However, not much research work has been carried out in Indian context to study the characteristics and preferences of Generation X and influence behavioural training on their interpersonal competence. Hence a study was conducted to study the influence of behavioural training on the interpersonal competence of Generation X managers. Data for the study were collected from 243 Generation X managers from a population of 353. The respondents were from nine companies that belonged to seven manufacturing industries. This paper presents the profile of Generation X managers, establishes the need of the study, the methodology adapted to collect the data for the study and discusses the findings of the study. Keywords: Generation X, Interpersonal Competence, Behavioural Training
Information methods for predicting risk and outcome of stroke
Stroke is a major cause of disability and mortality in most economically developed countries. It is the second leading cause of death worldwide (after cancer and heart disease) [55.1, 2] and a major cause of disability in adults in developed countries [55.3]. Personalized modeling is an emerging effective computational approach, which has been applied to various disciplines, such as in personalized drug design, ecology, business, and crime prevention; it has recently become more prominent in biomedical applications. Biomedical data on stroke risk factors and prognostic data are available in a large volume, but the data are complex and often difïŹcult to apply to a speciïŹc person. Individualizing stroke risk prediction and prognosis will allow patients to focus on risk factors speciïŹc to them, thereby reducing their stroke risk and managing stroke outcomes more effectively. This chapter reviews various methodsâconventional statistical methods and computational intelligent modeling methods for predicting risk and outcome of stroke
Prioritizing hazardous pollutants in two Nigerian water supply schemes: a risk-based approach
Objective To rank pollutants in two Nigerian water supply schemes according to their effect on human health using a risk-based approach.
Methods Hazardous pollutants in drinking-water in the study area were identified from a literature search and selected pollutants were monitored from April 2010 to December 2011 in catchments, treatment works and consumer taps. The disease burden due to each pollutant was estimated in disability-adjusted life years (DALYs) using data on the pollutantâs concentration, exposure to the pollutant, the severity of its health effects and the consumer population.
Findings The pollutants identified were microbial organisms, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead and zinc. All were detected in the catchments but only cadmium, cobalt, chromium, manganese and lead exceeded World Health Organization (WHO) guideline values after water treatment. Post-treatment contamination was observed. The estimated disease burden was greatest for chromium in both schemes, followed in decreasing order by cadmium, lead, manganese and cobalt. The total disease burden of all pollutants in the two schemes was 46 000 and 9500 DALYs per year or 0.14 and 0.088 DALYs per person per year, respectively, much higher than the WHO reference level of 1 Ă 10â6 DALYs per person per year. For each metal, the disease burden exceeded the reference level and was comparable with that due to microbial contamination reported elsewhere in Africa.
Conclusion The estimated disease burden of metal contamination of two Nigerian water supply systems was high. It could best be reduced by protection of water catchment and pretreatment by electrocoagulation
Data mining framework for fatty liver disease classification in ultrasound: a hybrid feature extraction paradigm
PURPOSE: Fatty liver disease (FLD) is an increasing prevalent disease that can be reversed if detected early. Ultrasound is the safest and ubiquitous method for identifying FLD. Since expert sonographers are required to accurately interpret the liver ultrasound images, lack of the same will result in interobserver variability. For more objective interpretation, high accuracy, and quick second opinions, computer aided diagnostic (CAD) techniques may be exploited. The purpose of this work is to develop one such CAD technique for accurate classification of normal livers and abnormal livers affected by FLD. METHODS: In this paper, the authors present a CAD technique (called Symtosis) that uses a novel combination of significant features based on the texture, wavelet transform, and higher order spectra of the liver ultrasound images in various supervised learning-based classifiers in order to determine parameters that classify normal and FLD-affected abnormal livers. RESULTS: On evaluating the proposed technique on a database of 58 abnormal and 42 normal liver ultrasound images, the authors were able to achieve a high classification accuracy of 93.3% using the decision tree classifier. CONCLUSIONS: This high accuracy added to the completely automated classification procedure makes the authors' proposed technique highly suitable for clinical deployment and usage
Lithium abundances from the 6104A line in cool Pleiades stars
Lithium abundances determined by spectral synthesis from both the 6708A
resonance line and the 6104 subordinate line are reported for 11 late-type
Pleiades stars, including spectra previously analysed by Russell (1996). We
report a 0.7 dex scatter in the abundances from 6708A, and a scatter at least
as large from the 6104A line. We find a reasonable correllation between the
6104A and 6708A Li abundances, although four stars have 6104A-determined
abundances which are significantly larger than the 6708-determined values, by
up to 0.5 dex, suggesting problems with the homogeneous, one-dimensional
atmospheres being used. We show that these discrepancies can be explained,
although probably not uniquely, by the presence of star spots with plausible
coverage fractions. The addition of spots does not significantly reduce the
apparent scatter in Li abundances, leaving open the possibility that at least
some of the spread is caused by real star-to-star differences in pre-main-
sequence Li depletion.Comment: 13 pages, 7 figures; Accepted by A&A 17/05/0
How Good a Clock is Rotation? The Stellar Rotation-Mass-Age Relationship for Old Field Stars
The rotation-mass-age relationship offers a promising avenue for measuring
the ages of field stars, assuming the attendant uncertainties to this technique
can be well characterized. We model stellar angular momentum evolution starting
with a rotation distribution from open cluster M37. Our predicted
rotation-mass-age relationship shows significant zero-point offsets compared to
an alternative angular momentum loss law and published gyrochronology
relations. Systematic errors at the 30 percent level are permitted by current
data, highlighting the need for empirical guidance. We identify two fundamental
sources of uncertainty that limit the precision of rotation-based ages and
quantify their impact. Stars are born with a range of rotation rates, which
leads to an age range at fixed rotation period. We find that the inherent
ambiguity from the initial conditions is important for all young stars, and
remains large for old stars below 0.6 solar masses. Latitudinal surface
differential rotation also introduces a minimum uncertainty into rotation
period measurements and, by extension, rotation-based ages. Both models and the
data from binary star systems 61 Cyg and alpha Cen demonstrate that latitudinal
differential rotation is the limiting factor for rotation-based age precision
among old field stars, inducing uncertainties at the ~2 Gyr level. We also
examine the relationship between variability amplitude, rotation period, and
age. Existing ground-based surveys can detect field populations with ages as
old as 1-2 Gyr, while space missions can detect stars as old as the Galactic
disk. In comparison with other techniques for measuring the ages of lower main
sequence stars, including geometric parallax and asteroseismology,
rotation-based ages have the potential to be the most precise chronometer for
0.6-1.0 solar mass stars.Comment: For a brief video explaining the key results of this paper, see
http://www.youtube.com/user/OSUAstronom
Reduced magnetic braking and the magnetic capture model for the formation of ultra-compact binaries
A binary in which a slightly evolved star starts mass transfer to a neutron
star can evolve towards ultra-short orbital periods under the influence of
magnetic braking. This is called magnetic capture. In a previous paper we
showed that ultra-short periods are only reached for an extremely small range
of initial binary parameters, in particular orbital period and donor mass. Our
conclusion was based on one specific choice for the law of magnetic braking,
and for the loss of mass and angular momentum during mass transfer. In this
paper we show that for less efficient magnetic braking it is impossible to
evolve to ultra-short periods, independent of the amount of mass and associated
angular momentum lost from the binary.Comment: 7 pages, 7 figures, accepted for publication in Astronomy and
Astrophysics. See http://www.astro.uu.nl/~sluys/PhD
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