14,227 research outputs found
Feasibility of Hair Collection for Cortisol Measurement in Population Research on Adolescent Health
Background: Black–White disparities in adolescent health are widespread and thought to be explained, in part, by exposure to chronic stress. Cortisol assayed from hair is increasingly recognized as a valid and reliable measure for chronic physiological stress, but the feasibility of collecting hair among large probability samples of diverse adolescents is unknown.
Purpose: The aim of the study was to investigate participation in hair collection for cortisol analyses in a probability sample of racially and socioeconomically diverse adolescents, including the extent to which sociodemographic factors and adverse exposures were associated with participation.
Methods: The study included a probability sample of 516 adolescents conducted in conjunction with a prospective cohort study on adolescent health. Data were collected over 1 week via in-home interviews, ecological momentary assessment, global positioning system methods, and in-home hair collection at the end of the week.
Results: Of the 516 eligible youth, 471 (91.3%) participated in the hair collection. Of the 45 youth who did not provide hair samples, 18 had insufficient hair, 25 refused, and 2 did not participate for unknown reasons. Multivariable logistic regression results indicated that non-Hispanic Black youth were less likely than their non-Hispanic White peers to participate due to insufficient hair or refusal (OR = 0.24, 95% CI [0 .09, 0.60]). Despite lower rates of participation, the proportion of Black youth in the participating sample was representative of the study area. No significant differences in participation were found by other sociodemographic characteristics or adverse exposures.
Conclusions: Hair collection for cortisol measurement is feasible among a probability sample of racially and socioeconomically diverse adolescents. Hair cortisol analyses may accelerate research progress to understand the biological and psychosocial bases of health disparities
Semi-inclusive charged-current neutrino-nucleus reactions
The general, universal formalism for semi-inclusive charged-current
(anti)neutrino-nucleus reactions is given for studies of any hadronic system,
namely, either nuclei or the nucleon itself. The detailed developments are
presented with the former in mind and are further specialized to cases where
the final-state charged lepton and an ejected nucleon are presumed to be
detected. General kinematics for such processes are summarized and then
explicit expressions are developed for the leptonic and hadronic tensors
involved and for the corresponding responses according to the usual charge,
longitudinal and transverse projections, keeping finite the masses of all
particles involved. In the case of the hadronic responses, general symmetry
principles are invoked to determine which contributions can occur. Finally, the
general leptonic-hadronic tensor contraction is given as well as the cross
section for the process
Coincidence charged-current neutrino-induced deuteron disintegration
Deuteron disintegration by charged-current neutrino (CC) scattering
offers the possibility to determine the energy of the incident neutrino by
measuring in coincidence two of the three resulting particles: a charged lepton
(usually a muon) and two protons, where we show that this channel can be
isolated from all other, for instance, from those with a pion in the final
state. We discuss the kinematics of the process for several detection
scenarios, both in terms of kinematic variables that are natural from a
theoretical point of view and others that are better matched to experimental
situations. The deuteron structure is obtained from a relativistic model
(involving an approximation to the Bethe-Salpeter equation) as an extension of
a previous, well-tested model used in deuteron electrodisintegration. We
provide inclusive and coincidence (semi-inclusive) cross sections for a variety
of kinematic conditions, using the plane-wave impulse approximation,
introducing final-state hadronic exchange terms (plane-wave Born approximation)
and final-state hadronic interactions (distorted-wave Born approximation).Comment: 31 pages, 14 figure
Receipt, 1 February 1867
https://egrove.olemiss.edu/aldrichcorr_d/1166/thumbnail.jp
Wigner Distribution Function Approach to Dissipative Problems in Quantum Mechanics with emphasis on Decoherence and Measurement Theory
We first review the usefulness of the Wigner distribution functions (WDF),
associated with Lindblad and pre-master equations, for analyzing a host of
problems in Quantum Optics where dissipation plays a major role, an arena where
weak coupling and long-time approximations are valid. However, we also show
their limitations for the discussion of decoherence, which is generally a
short-time phenomenon with decay rates typically much smaller than typical
dissipative decay rates. We discuss two approaches to the problem both of which
use a quantum Langevin equation (QLE) as a starting-point: (a) use of a reduced
WDF but in the context of an exact master equation (b) use of a WDF for the
complete system corresponding to entanglement at all times
Exposure to violence and PTSD symptoms among Somali women
Posttraumatic stress disorder (PTSD) symptoms, exposure to traumatic stressors, and health care utilization were examined in 84 women attending a primary health care clinic in Mogadishu, Somalia. The Somalia-Posttraumatic Diagnostic Scale was used in this active warzone to measure symptoms. Nearly all women reported high levels of confrontations with violence; half described being exposed to a potentially traumatizing event. Nearly one third had significant PTSD symptoms. Compared to those who did not, women who reported exposure to a traumatic stressor reported more confrontations with violence (7.1 vs. 3.3; p < . 001), health complaints (3.8 vs. 2.9; p = .03), and nearly 3 times as much (p = .03) health service utilization. A potentially traumatizing event was found to be a simplified proxy for assessing mental health distress in women attending a primary health care facility in highly insecure, unpredictable, resource-limited settings
Bayesian Methods for Analysis and Adaptive Scheduling of Exoplanet Observations
We describe work in progress by a collaboration of astronomers and
statisticians developing a suite of Bayesian data analysis tools for extrasolar
planet (exoplanet) detection, planetary orbit estimation, and adaptive
scheduling of observations. Our work addresses analysis of stellar reflex
motion data, where a planet is detected by observing the "wobble" of its host
star as it responds to the gravitational tug of the orbiting planet. Newtonian
mechanics specifies an analytical model for the resulting time series, but it
is strongly nonlinear, yielding complex, multimodal likelihood functions; it is
even more complex when multiple planets are present. The parameter spaces range
in size from few-dimensional to dozens of dimensions, depending on the number
of planets in the system, and the type of motion measured (line-of-sight
velocity, or position on the sky). Since orbits are periodic, Bayesian
generalizations of periodogram methods facilitate the analysis. This relies on
the model being linearly separable, enabling partial analytical
marginalization, reducing the dimension of the parameter space. Subsequent
analysis uses adaptive Markov chain Monte Carlo methods and adaptive importance
sampling to perform the integrals required for both inference (planet detection
and orbit measurement), and information-maximizing sequential design (for
adaptive scheduling of observations). We present an overview of our current
techniques and highlight directions being explored by ongoing research.Comment: 29 pages, 11 figures. An abridged version is accepted for publication
in Statistical Methodology for a special issue on astrostatistics, with
selected (refereed) papers presented at the Astronomical Data Analysis
Conference (ADA VI) held in Monastir, Tunisia, in May 2010. Update corrects
equation (3
Quantum measurement and decoherence
Distribution functions defined in accord with the quantum theory of
measurement are combined with results obtained from the quantum Langevin
equation to discuss decoherence in quantum Brownian motion. Closed form
expressions for wave packet spreading and the attenuation of coherence of a
pair of wave packets are obtained. The results are exact within the context of
linear passive dissipation. It is shown that, contrary to widely accepted
current belief, decoherence can occur at high temperature in the absence of
dissipation. Expressions for the decoherence time with and without dissipation
are obtained that differ from those appearing in earlier discussions
Measured quantum probability distribution functions for Brownian motion
The quantum analog of the joint probability distributions describing a
classical stochastic process is introduced. A prescription is given for
constructing the quantum distribution associated with a sequence of
measurements. For the case of quantum Brownian motion this prescription is
illustrated with a number of explicit examples. In particular it is shown how
the prescription can be extended in the form of a general formula for the
Wigner function of a Brownian particle entangled with a heat bath.Comment: Phys. Rev. A, in pres
Nuclear-spin relaxation of Pb in ferroelectric powders
Motivated by a recent proposal by O. P. Sushkov and co-workers to search for
a P,T-violating Schiff moment of the Pb nucleus in a ferroelectric
solid, we have carried out a high-field nuclear magnetic resonance study of the
longitudinal and transverse spin relaxation of the lead nuclei from room
temperature down to 10 K for powder samples of lead titanate (PT), lead
zirconium titanate (PZT), and a PT monocrystal. For all powder samples and
independently of temperature, transverse relaxation times were found to be
ms, while the longitudinal relaxation times exhibited a
temperature dependence, with of over an hour at the lowest temperatures,
decreasing to s at room temperature. At high temperatures, the
observed behavior is consistent with a two-phonon Raman process, while in the
low temperature limit, the relaxation appears to be dominated by a
single-phonon (direct) process involving magnetic impurities. This is the first
study of temperature-dependent nuclear-spin relaxation in PT and PZT
ferroelectrics at such low temperatures. We discuss the implications of the
results for the Schiff-moment search.Comment: 6 pages, 4 figure
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