3,551 research outputs found
The Effect of Melatonin Upon Post-Acute Withdrawal Among Males in a Residential Treatment Program (M-Paws): A Randomized, Double-Blind, Placebo Controlled Trial
The study goal was to assess melatonin as an adjuvant treatment along with current pharmaco- and behavioral therapy for 28 days on weekly self-reported severity of anxiety, depression, stress, and sleep complaints as well as how sleep is affecting daily life in a sample of males in recovery from chemical dependency at a single, residential treatment site, Salvation Army Harbor Light Center in Pittsburgh, PA. This study was a single-center, randomized, double-blind, placebo-controlled, parallel group trial of 28 days. Participants were randomized to melatonin (5 mg) or placebo and instructed to administer the intervention nightly at bedtime. Primary self-reported outcome measures of severity of anxiety, depression, stress, as well as sleep complaints and how sleep is affecting daily life were assessed on a weekly basis with the Generalized Anxiety Disorder Scale (GAD-7), Personal Health Questionnaire Depression Scale (PHQ-8), Perceived Stress Scale (PSS-14), and Pittsburgh Sleep Symptom Questionnaire – Insomnia (PSSQ-1). Secondary outcome measures were to acquire participant histories, determine adherence as well as adverse events. Seventy participants (age 21 – 65, mean 40.4 ± 11 years) were enrolled with 24 completing the study in each group. Demographically, the sample consisted of those who identified as white (70%), single (74.3%), and with an education level of high school/G.E.D. or less (77.1%). Intention-to-treat analysis for all outcome measures revealed statistically significant within-groups differences over time for both groups. The study failed to demonstrate statistically between-group differences for these measures. Also, complete case analysis for each week revealed no between-group differences. Additionally, the change from Baseline and Day 28 as determined by a response of an improvement of 50% or higher in scores for each scale revealed no significant strength of association between the groups when considering worst case for the loss to follow-up. Melatonin appeared to be well tolerated with similar adverse events reported as placebo; however, there was a tendency to report more vivid dreams/nightmares as well as next day tiredness/grogginess/sleepiness. Clinical investigations into the use of melatonin as a treatment for depression, anxiety, stress, and sleep difficulties in those recovering from illicit and non-illicit drug dependency are limited and larger studies are warranted. Possible future directions include a study design that is multicenter, the inclusion of a therapy only arm, assessing various doses and timelines, assessing effects in adolescents or females, or limiting inclusion based on prescribed medications, mental health status, medical conditions, prior melatonin use, and/or a specific chemical dependency. Overall, this is the first and largest randomized, double-blind, placebo-controlled, parallel group trial assessing the effects of melatonin upon post-acute withdrawal among males in a residential treatment program. However, the various analyses indicated insufficient evidence to suggest that melatonin and placebo were significantly different, and it may be concluded, based upon the study sample, design, and its limitations, the effect of melatonin on the assessed measures was no different than placebo. Due to the heterogeneity of the participants as evidenced by the participant histories, there exists a possibility of a Type II error that must be considered and not overlooked
Is There a Relationship between the Density of Primordial Black Holes in a Galaxy and the Rate of Cosmological Gamma-Ray Bursts?
The rate of accretion of matter from a solar-type star onto a primordial
black hole (PBH) that passes through it is calculated. The probability that a
PBH is captured into an orbit around a star in a galaxy is found. The mean
lifetime of the PBH in such an orbit and the rate of orbital captures of PBHs
in the galaxy are calculated. It is shown that this rate does not depend on the
mass of the PBH. This mechanism cannot make an appreciable contribution to the
rate of observed gamma-ray bursts. The density of PBHs in the galaxy can reach
a critical value - the density of the mass of dark matter in the galaxy.Comment: 7 page
The stellar mass-accretion rate relation in T Tauri stars and brown dwarfs
Recent observations show a strong correlation between stellar mass and
accretion rate in young stellar and sub-stellar objects, with the scaling
holding over more than four orders of magnitude
in accretion rate. We explore the consequences of this correlation in the
context of disk evolution models. We note that such a correlation is not
expected to arise from variations in disk angular momentum transport efficiency
with stellar mass, and suggest that it may reflect a systematic trend in disk
initial conditions. In this case we find that brown dwarf disks initially have
rather larger radii than those around more massive objects. By considering disk
evolution, and invoking a simple parametrization for a shut-off in accretion at
the end of the disk lifetime, we show that such models predict that the scatter
in the stellar mass-accretion rate relationship should increase with increasing
stellar mass, in rough agreement with current observations.Comment: 4 pages, 2 figures. Accepted for publication in ApJ Letter
Inverse Compton X-rays from the radio galaxy 3C 219
We report the results from a Chandra observation of the powerful nearby
(z=0.1744) radio galaxy 3C 219. We find evidence for non-thermal X-ray emission
from the radio lobes which fits fairly well with a combination of inverse
Compton scattering of Cosmic Microwave Background radiation and of nuclear
photons with the relativistic electrons in the lobes. The comparison between
radio synchrotron and IC emission yields a magnetic field strength
significantly lower (about a factor 3) than that calculated under minimum
energy conditions; the source energetics is then dominated by the relativistic
particles.Comment: 5 pages, 2 color figures, Accepted for publication in MNRAS pink
page
Hydromagnetic and gravitomagnetic crust-core coupling in a precessing neutron star
We consider two types of mechanical coupling between the crust and the core
of a precessing neutron star. First, we find that a hydromagnetic (MHD)
coupling between the crust and the core strongly modifies the star's
precessional modes when ; here is the
Alfven crossing timescale, and and are the star's spin and
precession periods, respectively. We argue that in a precessing pulsar PSR
B1828-11 the restoring MHD stress prevents a free wobble of the crust relative
to the non-precessing core. Instead, the crust and the proton-electron plasma
in the core must precess in unison, and their combined ellipticity determines
the period of precession. Link has recently shown that the neutron superfluid
vortices in the core of PSR B1828-11 cannot be pinned to the plasma; he has
also argued that this lack of pinning is expected if the proton Fermi liquid in
the core is type-I superconductor. In this case, the neutron superfluid is
dynamically decoupled from the precessing motion. The pulsar's precession
decays due to the mutual friction between the neutron superfluid and the plasma
in the core. The decay is expected to occur over tens to hundreds of precession
periods and may be measurable over a human lifetime. Such a measurement would
provide information about the strong n-p interaction in the neutron-star core.
Second, we consider the effect of gravitomagnetic coupling between the neutron
superfluid in the core and the rest of the star and show that this coupling
changes the rate of precession by about 10%. The general formalism developed in
this paper may be useful for other applications.Comment: 6 page
Wiggles in the cosmic microwave background radiation: echoes from non-singular cyclic-inflation
In this paper we consider a unique model of inflation where the universe
undergoes rapid asymmetric oscillations, each cycle lasting millions of Planck
time. Over many-many cycles the space-time expands to mimic the standard
inflationary scenario. Moreover, these rapid oscillations leave a distinctive
periodic signature in ln(k) in the primordial power spectrum, where k denotes
the comoving scale. The best fit parameters of the cyclic-inflation model
provides a very good fit to the 7-year WMAP data.Comment: Computational details and a figure adde
Extended radio emission in BL Lac objects - I: the images
We have observed 28 sources selected from the 1Jy sample of BL Lac objects
(Stickel et al. 1991) with the Very Large Array (VLA) in A, B and D
configurations at 1.36, 1.66 and 4.85 GHz, and/or with the Westerbork Synthesis
Radio Telescope (WSRT) at 1.40 GHz. In this paper we present high sensitivity
images at arcsecond resolution of the 18 objects showing extended structure in
our images, and of another source from the FIRST (Faint Images of the Radio Sky
at Twenty-cm) survey (Becker et al. 1995). In general our high sensitivity
images reveal an amount of extended emission larger than previously reported.
In some objects the luminosity of the extended structure is comparable with
that of FR~II radio sources. A future paper will be devoted to the
interpretation of these results.Comment: 12 pages, 35 figures, to appear on A&A Supp. Ser., postscript file
with figures included available at
http://www.ira.noto.cnr.it/staff/carlo/ds1030.ps.g
Magnetically Accreting Isolated Old Neutron Stars
Previous work on the emission from isolated old neutron stars (IONS)
accreting the inter-stellar medium (ISM) focussed on gravitational capture -
Bondi accretion. We propose a new class of sources which accrete via magnetic
interaction with the ISM. While for the Bondi mechanism, the accretion rate
decreases with increasing NS velocity, in magnetic accretors (MAGACs="magics")
the accretion rate increases with increasing NS velocity. MAGACs will be
produced among high velocity (~> 100 km s-1) high magnetic field (B> 1e14 G)
radio pulsars - the ``magnetars'' - after they have evolved first through
magnetic dipole spin-down, followed by a ``propeller'' phase (when the object
sheds angular momentum on a timescale ~< 1e10 yr). The properties of MAGACS may
be summarized thus: dipole magnetic fields of B~>1e14 G; minimum velocities
relative to the ISM of >25-100 km s-1, depending on B, well below the median in
the observed radio-pulsar population; spin-periods of >days to years; accretion
luminosities of 1e28- 1e31 ergs s-1 ; and effective temperatures kT=0.3 - 2.5
keV if they accrete onto the magnetic polar cap. We find no examples of MAGACs
among previously observed source classes (anomalous X-ray pulsars,
soft-gamma-ray repeaters or known IONS). However, MAGACs may be more prevelant
in flux-limited X-ray catalogs than their gravitationally accreting
counterparts.Comment: ApJ, accepte
The Gravitational and Electrostatic Fields Far from an Isolated Einstein-Maxwell Source
The exterior solution for an arbitrary charged, massive source, is studied as
a static deviation from the Reissner-Nordstr\o m metric. This is reduced to two
coupled ordinary differential equations for the gravitational and electrostatic
potential functions. The homogeneous equations are explicitly solved in the
particular case , obtaining a multipole expansion with radial
hypergeometric dependence for both potentials. In the limiting case of a
neutral source, the equations are shown to coincide with recent results by
Bondi and Rindler.Comment: 11 pages, revTe
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