126 research outputs found
Adolescent obesity increases significantly in second and third generation U.S. immigrants: The National Longitudinal Study of Adolescent Health
Little is known concerning obesity patterns of ethnic subpopulations in the U.S. and the effects of acculturation on these patterns. Adolescent obesity, a major public health problem, has important health, social and economic consequences for the adolescent. The National Longitudinal Study of Adolescent Health survey is unique in the size of the adolescent sample and in its ability to provide large representative samples of Anglo, African-American, Hispanic and Asian-American adolescents. A nationally representative sample of 13,783 adolescents was studied. Measurements of weight and height collected in the second wave of the survey were used to study adolescent obesity. Multivariate logit techniques were used to provide an understanding of the ethnic, age, gender and intergenerational patterns of adolescent obesity. Comparisons are presented between the NHANES III results and those from the Adolescent Health Survey. The smoothed version of the NHANES I 85th percentile cut-off was used for the measure of obesity in this paper. For the total sample, 26.5% were obese. The rates were as follows: white non-Hispanics, 24.2%; black non-Hispanics, 30.9%; all Hispanics, 30.4%; and all Asian-Americans, 20.6%. Important variations within the Hispanic and Asian-American subpopulations are presented. The Chinese (15.3%) and Filipino (18.5%) samples showed substantially lower obesity than non-Hispanic whites. All groups showed more obesity among males than among females, except for blacks (27.4% for males and 34.0% for females). Asian-American and Hispanic adolescents born in the U.S. are more than twice as likely to be obese as are first generation residents of the 50 states
WASP-120b, WASP-122b and WASP-123b: Three newly discovered planets from the WASP-South survey
We present the discovery by the WASP-South survey of three planets transiting
moderately bright stars (V ~ 11). WASP-120b is a massive (5.0MJup) planet in a
3.6-day orbit that we find likely to be eccentric (e = 0.059+0.025-0.018)
around an F5 star. WASP-122b is a hot-Jupiter (1.37MJup, 1.79RJup) in a 1.7-day
orbit about a G4 star. Our predicted transit depth variation cause by the
atmosphere of WASP-122b suggests it is well suited to characterisation.
WASP-123b is a hot-Jupiter (0.92MJup, 1.33RJup) in a 3.0-day orbit around an
old (~ 7 Gyr) G5 star.Comment: 15 pages, 10 figures, 5 table
Giant planet migration, disk evolution, and the origin of transitional disks
We present models of giant planet migration in evolving protoplanetary disks.
Our disks evolve subject to viscous transport of angular momentum and
photoevaporation, while planets undergo Type II migration. We use a Monte Carlo
approach, running large numbers of models with a range in initial conditions.
We find that relatively simple models can reproduce both the observed radial
distribution of extra-solar giant planets, and the lifetimes and accretion
histories of protoplanetary disks. The use of state-of-the-art photoevaporation
models results in a degree of coupling between planet formation and disk
clearing, which has not been found previously. Some accretion across planetary
orbits is necessary if planets are to survive at radii <~1.5AU, and if planets
of Jupiter mass or greater are to survive in our models they must be able to
form at late times, when the disk surface density in the formation region is
low. Our model forms two different types of "transitional" disks, embedded
planets and clearing disks, which show markedly different properties. We find
that the observable properties of these systems are broadly consistent with
current observations, and highlight useful observational diagnostics. We
predict that young transition disks are more likely to contain embedded giant
planets, while older transition disks are more likely to be undergoing disk
clearing.Comment: 13 pages, 9 figures. Accepted for publication in Ap
The thermal emission of the exoplanets WASP-1b and WASP-2b
We present a comparative study of the thermal emission of the transiting
exoplanets WASP-1b and WASP-2b using the Spitzer Space Telescope. The two
planets have very similar masses but suffer different levels of irradiation and
are predicted to fall either side of a sharp transition between planets with
and without hot stratospheres. WASP-1b is one of the most highly irradiated
planets studied to date. We measure planet/star contrast ratios in all four of
the IRAC bands for both planets (3.6-8.0um), and our results indicate the
presence of a strong temperature inversion in the atmosphere of WASP-1b,
particularly apparent at 8um, and no inversion in WASP-2b. In both cases the
measured eclipse depths favor models in which incident energy is not
redistributed efficiently from the day side to the night side of the planet. We
fit the Spitzer light curves simultaneously with the best available radial
velocity curves and transit photometry in order to provide updated measurements
of system parameters. We do not find significant eccentricity in the orbit of
either planet, suggesting that the inflated radius of WASP-1b is unlikely to be
the result of tidal heating. Finally, by plotting ratios of secondary eclipse
depths at 8um and 4.5um against irradiation for all available planets, we find
evidence for a sharp transition in the emission spectra of hot Jupiters at an
irradiation level of 2 x 10^9 erg/s/cm^2. We suggest this transition may be due
to the presence of TiO in the upper atmospheres of the most strongly irradiated
hot Jupiters.Comment: 10 pages, submitted to Ap
Do Social Bonds Matter for Emerging Adults?
The extent to which social bonds and turning points influence criminal activity has been the focus of much empirical research. However, there have been few empirical studies exploring social bonds and turning points and offending for those who have experienced emerging adulthood, a recently identified stage of the life course. Using data from the National Longitudinal Study of Adolescent Health we examined if indicators of social bonds and turning points were predictors of criminal offending. Several of the turning points and social bonds included in these analyses were found to influence decreases in criminal offending for a cohort of emerging adults. We extend previous research by examining the influence of social bonds and turning points on patterns of criminal offending during emerging adulthood
Strong size evolution of the most massive galaxies since z~2
Using the combined capabilities of the large near-infrared Palomar/DEEP-2
survey, and the superb resolution of the ACS HST camera, we explore the size
evolution of 831 very massive galaxies (M*>10^{11}h_{70}^{-2}M_sun) since z~2.
We split our sample according to their light concentration using the Sersic
index n. At a given stellar mass, both low (n2.5)
concentrated objects were much smaller in the past than their local massive
counterparts. This evolution is particularly strong for the highly concentrated
(spheroid-like) objects. At z~1.5, massive spheroid-like objects were a factor
of 4(+-0.4) smaller (i.e. almost two orders of magnitudes denser) than those we
see today. These small sized, high mass galaxies do not exist in the nearby
Universe, suggesting that this population merged with other galaxies over
several billion years to form the largest galaxies we see today.Comment: MNRAS in press, 13 pages, 11 figures. Data Table will be published in
its integrity in the MNRAS online versio
Seven transiting hot-Jupiters from WASP-South, Euler and TRAPPIST: WASP-47b, WASP-55b, WASP-61b, WASP-62b, WASP-63b, WASP-66b & WASP-67b
We present seven new transiting hot Jupiters from the WASP-South survey. The
planets are all typical hot Jupiters orbiting stars from F4 to K0 with
magnitudes of V = 10.3 to 12.5. The orbital periods are all in the range
3.9--4.6 d, the planetary masses range from 0.4--2.3 Mjup and the radii from
1.1--1.4 Mjup. In line with known hot Jupiters, the planetary densities range
from Jupiter-like to inflated (rho = 0.13--1.07 rho_jup). We use the increasing
numbers of known hot Jupiters to investigate the distribution of their orbital
periods and the 3--4-d "pile-up".Comment: 15 page
WASP-121 b : a hot Jupiter close to tidal disruption transiting an active F star
We present the discovery by the WASP-South survey of WASP-121 b, a new remarkable short-period transiting hot Jupiter. The planet has a mass of 1.183+0.064−0.062 MJup, a radius of 1.865 ± 0.044 RJup, and transits every 1.274 9255+0.000 0020−0.000 0025 days an active F6-type main-sequence star (V = 10.4, 1.353+0.080 −0.079 M, 1.458 ± 0.030 R, Teff = 6460 ± 140 K). A notable property of WASP-121 b is that its orbital semimajor axis is only ~1.15 times larger than its Roche limit, which suggests that the planet is close to tidal disruption. Furthermore, its large size and extreme irradiation (~7.1 109 erg s−1 cm−2) make it an excellent target for atmospheric studies via secondary eclipse observations. Using the TRAnsiting Planets and PlanetesImals Small Telescope, we indeed detect its emission in the z'-band at better than ~4σ, the measured occultation depth being 603 ± 130 ppm. Finally, from a measurement of the Rossiter–McLaughlin effect with the CORALIE spectrograph, we infer a sky-projected spin-orbit angle of 257.8+5.3−5.5. This result may suggest a significant misalignment between the spin axis of the host star and the orbital plane of the planet. If confirmed, this high misalignment would favour a migration of the planet involving strong dynamical events with a third body
Prevalence of Chlamydial and Gonococcal Infections Among Young Adults in the United States
Context: Chlamydial and gonococcal infections are important causes of pelvic inflammatory
disease, ectopic pregnancy, and infertility. Although screening for Chlamydia
trachomatis is widely recommended among young adult women, little information
is available regarding the prevalence of chlamydial and gonococcal infections
in the general young adult population.
Objective: To determine the prevalence of chlamydial and gonoccoccal infections in
a nationally representative sample of young adults living in the United States.
Design, Setting, and Participants: Cross-sectional analyses of a prospective cohort
study of a nationally representative sample of 14322 young adults aged 18 to 26
years. In-home interviews were conducted across the United States for Wave III of
The National Longitudinal Study of Adolescent Health (Add Health) from April 2, 2001,
to May 9, 2002. This study sample represented 66.3% of the original 18924 participants
in Wave I of Add Health. First-void urine specimens using ligase chain reaction
assay were available for 12548 (87.6%) of the Wave III participants.
Main Outcome Measures: Prevalences of chlamydial and gonococcal infections
in the general young adult population, and by age, self-reported race/ethnicity, and
geographic region of current residence.
Results: Overall prevalence of chlamydial infection was 4.19% (95% confidence interval
[CI], 3.48%-4.90%). Women (4.74%; 95% CI, 3.93%-5.71%) were more likely
to be infected than men (3.67%; 95% CI, 2.93%-4.58%; prevalence ratio, 1.29; 95%
CI, 1.03-1.63). The prevalence of chlamydial infection was highest among black women
(13.95%; 95% CI, 11.25%-17.18%) and black men (11.12%; 95% CI, 8.51%-
14.42%); lowest prevalences were among Asian men (1.14%; 95% CI, 0.40%-3.21%),
white men (1.38%; 95% CI, 0.93%-2.03%), and white women (2.52%; 95% CI,
1.90%-3.34%). Prevalence of chlamydial infection was highest in the south (5.39%;
95% CI, 4.24%-6.83%) and lowest in the northeast (2.39%; 95% CI, 1.56%-3.65%).
Overall prevalence of gonorrhea was 0.43% (95% CI, 0.29%-0.63%). Among black
men and women, the prevalence was 2.13% (95% CI, 1.46%-3.10%) and among
white young adults, 0.10% (95% CI, 0.03%-0.27%). Prevalence of coinfection with
both chlamydial and gonococcal infections was 0.030% (95% CI, 0.18%-0.49%).
Conclusions: The prevalence of chlamydial infection is high among young adults in
the United States. Substantial racial/ethnic disparities are present in the prevalence of
both chlamydial and gonococcal infections
Automatic vetting of planet candidates from ground based surveys : machine learning with NGTS
State of the art exoplanet transit surveys are producing ever increasing quantities of data. To make the best use of this resource, in detecting interesting planetary systems or in determining accurate planetary population statistics, requires new automated methods. Here we describe a machine learning algorithm that forms an integral part of the pipeline for the NGTS transit survey, demonstrating the efficacy of machine learning in selecting planetary candidates from multi-night ground based survey data. Our method uses a combination of random forests and self-organising-maps to rank planetary candidates, achieving an AUC score of 97.6% in ranking 12368 injected planets against 27496 false positives in the NGTS data. We build on past examples by using injected transit signals to form a training set, a necessary development for applying similar methods to upcoming surveys. We also make the autovet code used to implement the algorithm publicly accessible. autovet is designed to perform machine learned vetting of planetary candidates, and can utilise a variety of methods. The apparent robustness of machine learning techniques, whether on space-based or the qualitatively different ground-based data, highlights their importance to future surveys such as TESS and PLATO and the need to better understand their advantages and pitfalls in an exoplanetary context
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