49 research outputs found
Prediction of adult height in girls: the Beunen-MalinaFreitas method
The purpose of this study was to validate and cross-validate the Beunen-Malina-Freitas method for non-invasive prediction of adult height in girls. A sample of 420 girls aged 10â15 years from the Madeira Growth Study were measured at yearly intervals and then 8 years later. Anthropometric dimensions (lengths, breadths, circumferences, and skinfolds) were measured; skeletal age was assessed using the Tanner-Whitehouse 3 method and menarcheal status (present or absent) was recorded. Adult height was measured and predicted using stepwise, forward, and maximum R2 regression techniques. Multiple correlations, mean differences, standard errors of prediction, and error boundaries were calculated. A sample of the Leuven Longitudinal Twin Study was used to cross-validate the regressions. Age-speciïŹc coefïŹcients of determination (R2) between predicted and measured adult height varied between 0.57 and 0.96, while standard errors of prediction varied between 1.1 and 3.9 cm. The cross-validation conïŹrmed the validity of the Beunen-Malina-Freitas method in girls aged 12â15 years, but at lower ages the cross-validation was less consistent. We conclude that the Beunen-Malina-Freitas method is valid for the prediction of adult height in girls aged 12â15 years. It is applicable to European populations or populations of European ancestry.info:eu-repo/semantics/publishedVersio
Associação do envolvimento Ă actividade fĂsica e Ă aptidĂŁo em jovens madeirenses
O objectivo central do presente estudo consistiu em investigar a associação do meio (urbano, semi-urbano e rural) Ă actividade fĂsica e Ă aptidĂŁo na criança e no adolescente madeirense. A amostra foi constituĂda por 1498 sujeitos, 758 rapazes e 740 raparigas, que participaram no âEstudo de Crescimento da Madeiraâ. A actividade fĂsica e a aptidĂŁo foram avaliadas atravĂ©s do questionĂĄrio de Baecke e da bateria de testes motores Eurofit, respectivamente. As crianças e adolescentes madeirenses do meio urbano apresentaram valores mais elevados de prĂĄtica regular e sistemĂĄtica de um ou mais desportos. Os resultados para as componentes da aptidĂŁo fĂsica nĂŁo favorecem um Ășnico meio sĂłcio-geogrĂĄfico. Os rapazes do meio urbano e/ou semi-urbano foram mais proficientes na flexibilidade, força e resistĂȘncia muscular, e potĂȘncia, enquanto os rapazes rurais apresentaram melhores resultados na resistĂȘncia aerĂłbia, força estĂĄtica, e velocidade/agilidade. As raparigas do meio urbano e/ou semiurbano apresentaram melhores resultados na velocidade/agilidade, enquanto as raparigas do meio rural foram mais proficientes na força estĂĄtica e na força e resistĂȘncia muscular. A eliminação dos diferenciais negativos na actividade fĂsica e na aptidĂŁo associados ao meio sĂłcio-geogrĂĄfico irĂĄ resultar numa melhor saĂșde das crianças e adolescentes madeirenses.info:eu-repo/semantics/publishedVersio
Classical tests in brane gravity
The vacuum solutions in brane gravity differ from those in 4D by a number of
additional terms and reduce to the familiar Schwarzschild metric at small
distances. We study the possible roles that such terms may play in the
precession of planetary orbits, bending of light, radar retardation and the
anomaly in mean motion of test bodies. Using the available data from Solar
System experiments, we determine the range of the free parameters associated
with the linear term in the metric. The best results come from the anomalies in
the mean motion of planets. Such studies should shed some light on the origin
of dark energy via the solar system tests.Comment: 10 pages, no figures, to appear in CQ
Accretion of Planetary Material onto Host Stars
Accretion of planetary material onto host stars may occur throughout a star's
life. Especially prone to accretion, extrasolar planets in short-period orbits,
while relatively rare, constitute a significant fraction of the known
population, and these planets are subject to dynamical and atmospheric
influences that can drive significant mass loss. Theoretical models frame
expectations regarding the rates and extent of this planetary accretion. For
instance, tidal interactions between planets and stars may drive complete
orbital decay during the main sequence. Many planets that survive their stars'
main sequence lifetime will still be engulfed when the host stars become red
giant stars. There is some observational evidence supporting these predictions,
such as a dearth of close-in planets around fast stellar rotators, which is
consistent with tidal spin-up and planet accretion. There remains no clear
chemical evidence for pollution of the atmospheres of main sequence or red
giant stars by planetary materials, but a wealth of evidence points to active
accretion by white dwarfs. In this article, we review the current understanding
of accretion of planetary material, from the pre- to the post-main sequence and
beyond. The review begins with the astrophysical framework for that process and
then considers accretion during various phases of a host star's life, during
which the details of accretion vary, and the observational evidence for
accretion during these phases.Comment: 18 pages, 5 figures (with some redacted), invited revie
Stochastic Gravity: Theory and Applications
Whereas semiclassical gravity is based on the semiclassical Einstein equation
with sources given by the expectation value of the stress-energy tensor of
quantum fields, stochastic semiclassical gravity is based on the
Einstein-Langevin equation, which has in addition sources due to the noise
kernel. In the first part, we describe the fundamentals of this new theory via
two approaches: the axiomatic and the functional. In the second part, we
describe three applications of stochastic gravity theory. First, we consider
metric perturbations in a Minkowski spacetime, compute the two-point
correlation functions of these perturbations and prove that Minkowski spacetime
is a stable solution of semiclassical gravity. Second, we discuss structure
formation from the stochastic gravity viewpoint. Third, we discuss the
backreaction of Hawking radiation in the gravitational background of a black
hole and describe the metric fluctuations near the event horizon of an
evaporating black holeComment: 100 pages, no figures; an update of the 2003 review in Living Reviews
in Relativity gr-qc/0307032 ; it includes new sections on the Validity of
Semiclassical Gravity, the Stability of Minkowski Spacetime, and the Metric
Fluctuations of an Evaporating Black Hol
Perturbation Spectra in the Warm Inflationary Scenario
We investigate the phenomenology of warm inflation and present generic
results about the evolution of the inflaton and radiation fields. The general
conditions required for warm inflation to take place are derived and discussed.
A comprehensive approach is presented for the generation of thermally induced
adiabatic and isocurvature perturbations and the amplitude of their spectra
calculated. In addition we derive the ratio of tensor-to-scalar perturbations
and find the spectral indices for adiabatic, isocurvature and tensor
perturbations formed in the warm inflationary era. These results are presented
in a simplified and compact approach that is generally applicable. Our results
are illustrated by inflation models with polynomial and exponential potentials.
We compare our analytic results against numerical models and find excellent
agreement. Finally, presently available data is used to put constraints on warm
inflation and we discuss how near--future observations may distinguish the warm
inflationary scenario from standard supercooled inflation. The main observable
difference is the different scalar-to- tensor ratio, and that the consistency
relation between this and the slope of tensor perturbations does not hold for
warm inflation.Comment: 12 pages, Latex, Accepted by Phys Rev D., minor change
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
Tracking of fatness during childhood, adolescence and young adulthood: a 7-year follow-up study in Madeira Island, Portugal
Aims: Investigating tracking of fatness from childhood to adolescence, early adolescence to young adulthood and late adolescence to young adulthood. Subjects and methods: Participants from the Madeira Growth Study were followed during an average period of 7.2 years. Height, body mass, skin-folds and circumferences were measured, nine health- and performance-related tests were administered and the Baecke questionnaire was used to assess physical activity. Skeletal maturity was estimated using the TW3 method. Results: The prevalence of overweight plus obesity ranged from 8.2â20.0% at baseline and from 20.4â40.0% at followup, in boys. Corresponding percentages for girls were 10.6â 12.0% and 13.2â18.0%. Inter-age correlations for fatness indicators ranged from 0.43â0.77. BMI, waist circumference and sum of skin-folds at 8, 12 and 16-years old were the main predictors of these variables at 15, 19 and 23-years old, respectively. Strength, muscular endurance and aerobic ïŹtness were negatively related to body fatness. Physical activity and maturation were independently associated with adolescent (15 years) and young adult (19 years) fatness. Conclusions: Over 7.2 years, tracking was moderate-to-high for fatness. Variance was explained by fatness indicators and to a small extent by physical ïŹtness, physical activity and maturation
Automated transient identification in the Dark Energy Survey
We describe an algorithm for identifying point-source transients and moving objects on reference-subtracted optical images containing artifacts of processing and instrumentation. The algorithm makes use of the supervised machine learning technique known as Random Forest. We present results from its use in the Dark Energy Survey Supernova program (DES-SN), where it was trained using a sample of 898,963 signal and background events generated by the transient detection pipeline. After reprocessing the data collected during the first DES-SN observing season (2013 September through 2014 February) using the algorithm, the number of transient candidates eligible for human scanning decreased by a factor of 13.4, while only 1.0% of the artificial Type Ia supernovae (SNe) injected into search images to monitor survey efficiency were lost, most of which were very faint events. Here we characterize the algorithm's performance in detail, and we discuss how it can inform pipeline design decisions for future time-domain imaging surveys, such as the Large Synoptic Survey Telescope and the Zwicky Transient Facility. An implementation of the algorithm and the training data used in this paper are available at at http://portal.nersc.gov/project/dessn/autoscan
Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median ). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July