975 research outputs found
Randomized controlled trial of a minimal versus extended Internet-based intervention for problem drinkers: study protocol
Infrared Dark Clouds in the Small Magellanic Cloud?
We have applied the unsharp-masking technique to the 24 m image of the
Small Magellanic Cloud (SMC), obtained with the Spitzer Space Telescope, to
search for high-extinction regions. This technique has been used to locate very
dense and cold interstellar clouds in the Galaxy, particularly infrared dark
clouds (IRDCs). Fifty five candidate regions of high-extinction, namely
high-contrast regions (HCRs), have been identified from the generated
decremental contrast image of the SMC. Most HCRs are located in the southern
bar region and mainly distributed in the outskirts of CO clouds, but most
likely contain a significant amount of H2. HCRs have a peak-contrast at 24
m of 2 - 2.5 % and a size of 8 - 14 pc. This corresponds to the size of
typical and large Galactic IRDCs, but Galactic IRDCs are 2 - 3 times darker at
24 m than our HCRs. To constrain the physical properties of the HCRs, we
have performed NH3, N2H+, HNC, HCO+, and HCN observations toward one of the
HCRs, HCR LIRS36-EAST, using the Australia Telescope Compact Array and the
Mopra single-dish radio telescope. We did not detect any molecular line
emission, however, our upper limits to the column densities of molecular
species suggest that HCRs are most likely moderately dense with n ~ 10^{3}
cm-3. This volume density is in agreement with predictions for the cool atomic
phase in low metallicity environments. We suggest that HCRs may be tracing
clouds at the transition from atomic to molecule-dominated medium, and could be
a powerful way to study early stages of gas condensation in low metallicity
galaxies. Alternatively, if made up of dense molecular clumps < 0.5 pc in size,
HCRs could be counterparts of Galactic IRDCs, and/or regions with highly
unusual abundance of very small dust grains.Comment: accepted for publication in the Astronomical Journa
PRODIGE -- Envelope to Disk with NOEMA II. Small-scale temperature structure and a streamer feeding the SVS13A protobinary using CH3CN and DCN
Aims. We present high sensitivity and high-spectral resolution NOEMA
observations of the Class 0/I binary system SVS13A, composed of the low-mass
protostars VLA4A and VLA4B with a separation of ~90 au. VLA4A is undergoing an
accretion burst that enriches the chemistry of the surrounding gas. This gives
us an excellent opportunity to probe the chemical and physical conditions as
well as the accretion process. Methods. We observe the (12K-11K) lines of CH3CN
and CH313CN, the DCN (3-2) line, and the C18O (2-1) line toward SVS13A using
NOEMA. Results. We find complex line profiles at disk scales which cannot be
explained by a single component or pure Keplerian motion. By adopting two
velocity components to model the complex line profiles, we find that the
temperatures and densities are significantly different between these two
components. This suggests that the physical conditions of the emitting gas
traced via CH3CN can change dramatically within the circumbinary disk. In
addition, combining our observations of DCN (3-2) with previous ALMA
high-angular-resolution observations, we find that the binary system (or VLA4A)
might be fed by an infalling streamer from envelope scales (~700 au). If this
is the case, this streamer contributes to the accretion of material onto the
system with a rate of at least 1.4x10-6 Msun yr-1. Conclusions. We conclude
that the CH3CN emission in SVS13A traces hot gas from a complex structure. This
complexity might be affected by a streamer that is possibly infalling and
funneling material into the central region.Comment: 20 pages, 19 figures, accepted to A&
Ultra-brief intervention for problem drinkers: research protocol
Background: Helping the large number of problem drinkers who will never seek treatment is a challenging issue. Public health initiatives employing educational materials or mass media campaigns
have met with mixed success. However, clinical research has developed effective brief interventions to help problem drinkers. This project will employ an intervention that has been validated in clinical settings and then modified into an ultra-brief format suitable for use as a public health intervention. The major objective of this study is to conduct a randomized controlled trial to establish the effectiveness of an ultra-brief, personalized feedback intervention for problem drinkers.
Methods/design: Problem drinkers recruited on a baseline population telephone survey conducted in a major metropolitan city in Canada will be randomized to one of three conditions -
a personalized feedback pamphlet condition, a control pamphlet condition, or a no intervention control condition. In the week after the baseline survey, households in the two pamphlet conditions will be sent their respective pamphlets. Changes in drinking will be assessed post intervention at three-month and six-month follow-ups. Drinking outcomes will be compared between
experimental conditions using Structural Equation Modeling. The primary hypothesis is that problem drinkers from households who receive the personalized feedback pamphlet intervention will display significantly improved drinking outcomes at three and six-month follow-ups as compared to problem drinkers from households in the no intervention control condition. Secondary hypotheses will test the impact of the intervention on help seeking, and explore the mediating or moderating role of perceived drinking norms, perceived alcohol risks and the problem drinker's social reasons for drinking.
Discussion: This trial will provide information on the effectiveness of a pamphlet-based personalized feedback intervention for problem drinkers in a community setting.
Trial registration: ClinicalTrials.gov registration #NCT00688584.This study is funded by the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Grant #R01 AA015680-01A2
Gravitational Lensing by Black Holes
We review the theoretical aspects of gravitational lensing by black holes,
and discuss the perspectives for realistic observations. We will first treat
lensing by spherically symmetric black holes, in which the formation of
infinite sequences of higher order images emerges in the clearest way. We will
then consider the effects of the spin of the black hole, with the formation of
giant higher order caustics and multiple images. Finally, we will consider the
perspectives for observations of black hole lensing, from the detection of
secondary images of stellar sources and spots on the accretion disk to the
interpretation of iron K-lines and direct imaging of the shadow of the black
hole.Comment: Invited article for the GRG special issue on lensing (P. Jetzer, Y.
Mellier and V. Perlick Eds.). 31 pages, 12 figure
Insights into the function of silver as an oxidation catalyst by ab initio, atomistic thermodynamics
To help understand the high activity of silver as an oxidation catalyst,
e.g., for the oxidation of ethylene to epoxide and the dehydrogenation of
methanol to formaldehyde, the interaction and stability of oxygen species at
the Ag(111) surface has been studied for a wide range of coverages. Through
calculation of the free energy, as obtained from density-functional theory and
taking into account the temperature and pressure via the oxygen chemical
potential, we obtain the phase diagram of O/Ag(111). Our results reveal that a
thin surface-oxide structure is most stable for the temperature and pressure
range of ethylene epoxidation and we propose it (and possibly other similar
structures) contains the species actuating the catalysis. For higher
temperatures, low coverages of chemisorbed oxygen are most stable, which could
also play a role in oxidation reactions. For temperatures greater than about
775 K there are no stable oxygen species, except for the possibility of O atoms
adsorbed at under-coordinated surface sites Our calculations rule out thicker
oxide-like structures, as well as bulk dissolved oxygen and molecular
ozone-like species, as playing a role in the oxidation reactions.Comment: 15 pages including 9 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
PRODIGE -- Envelope to disk with NOEMA I. A 3000 au streamer feeding a Class I protostar
Context. In the past few years, there has been a rise in the detection of
streamers, asymmetric flows of material directed toward the protostellar disk
with material from outside the star's natal core. It is unclear how they affect
the process of mass accretion, in particular beyond the Class 0 phase. Aims. We
investigate the gas kinematics around Per-emb-50, a Class I source in the
crowded star-forming region NGC 1333. Our goal is to study how the mass infall
proceeds from envelope to disk scales in this source. Results. We discover a
streamer delivering material toward Per-emb-50 in HCO and CO
emission. The streamer's emission can be well described by the analytic
solutions for an infalling parcel of gas along a streamline with conserved
angular momentum, both in the image plane and along the line of sight
velocities. The streamer has a mean infall rate of M yr, times higher than the current accretion rate of the
protostar. SO and SO emission reveal asymmetric infall motions in the inner
envelope, additional to the streamer around Per-emb-50. Furthermore, the
presence of SO could mark the impact zone of the infalling material.
Conclusions. The streamer delivers sufficient mass to sustain the protostellar
accretion rate and might produce an accretion burst, which would explain the
protostar's high luminosity with respect to other Class I sources. Our results
highlight the importance of late infall for protostellar evolution: streamers
might provide a significant amount of mass for stellar accretion after the
Class 0 phase.Comment: 20 pages, 14 figures, accepted for publication in A&
GASKAP -- The Galactic ASKAP Survey
A survey of the Milky Way disk and the Magellanic System at the wavelengths
of the 21-cm atomic hydrogen (HI) line and three 18-cm lines of the OH molecule
will be carried out with the Australian Square Kilometre Array Pathfinder
telescope. The survey will study the distribution of HI emission and absorption
with unprecedented angular and velocity resolution, as well as molecular line
thermal emission, absorption, and maser lines. The area to be covered includes
the Galactic plane (|b|< 10deg) at all declinations south of delta = +40deg,
spanning longitudes 167deg through 360deg to 79deg at b=0deg, plus the entire
area of the Magellanic Stream and Clouds, a total of 13,020 square degrees. The
brightness temperature sensitivity will be very good, typically sigma_T ~ 1 K
at resolution 30arcsec and 1 km/s. The survey has a wide spectrum of scientific
goals, from studies of galaxy evolution to star formation, with particular
contributions to understanding stellar wind kinematics, the thermal phases of
the interstellar medium, the interaction between gas in the disk and halo, and
the dynamical and thermal states of gas at various positions along the
Magellanic Stream.Comment: 45 pages, 8 figures, Pub. Astron. Soc. Australia (in press
Association Between Nutritional Status and the Immune response in HIV + Patients under HAART: Protocol for a Systematic Review.
Over 850 million people worldwide and 200 million adults in Sub-Saharan Africa suffer from malnutrition. Countries most affected by HIV are also stricken by elevated rates of food insecurity and malnutrition. HIV infection and insufficient nutritional intake are part of a vicious cycle that contributes to immunodeficiency and negative health outcomes. However, the effect of the overlap between HIV infection and undernutrition on the immune response following antiretroviral initiation remains unclear. A possible explanation could be the lack of consensus concerning the definition and assessment of nutritional status. Our objectives are to investigate the existence of an association between undernutrition and immune response at antiretroviral treatment initiation and the following year in low- and middle-income countries where malnutrition is most prevalent. Our systematic review will identify studies originating from low- and middle-income countries (LMICs) published from 1996 onwards, through searches in MEDLINE (PubMed interface), EMBASE (OVID interface), Cochrane Central (OVID interface) and grey literature. No language restrictions will be applied. We will seek out studies of any design investigating the association between the nutritional status (for example, undernourished versus well nourished) and the immune response, either in terms of CD4 count or immune failure, in seropositive patients initiating antiretroviral therapy or in their first year of treatment. Two reviewers will independently screen articles, extract data and assess scientific quality using standardized forms and published quality assessment tools tailored for each study design. Where feasible, pooled measures of association will be obtained through meta-analyses. Results will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement. This protocol has been registered in the PROSPERO database (registration number: CRD42014005961). Undernutrition and weight loss are prevalent amongst highly active antiretroviral therapy (HAART)-treated patients in LMICs and contribute to excess early mortality. A possible intermediate pathway could be poor immune reconstitution secondary to deficient nutritional status. In the face of limited access to second line treatments, raising HIV resistance and cut backs to HIV programs, it is crucial to identify the factors associated with suboptimal response and therapeutic failure in order to better customize the care strategies employed in LMICs
Sensitivity to Gravitational Waves from Compact Binary Coalescences Achieved during LIGO's Fifth and Virgo's First Science Run
We summarize the sensitivity achieved by the LIGO and Virgo gravitational
wave detectors for compact binary coalescence (CBC) searches during LIGO's
fifth science run and Virgo's first science run. We present noise spectral
density curves for each of the four detectors that operated during these
science runs which are representative of the typical performance achieved by
the detectors for CBC searches. These spectra are intended for release to the
public as a summary of detector performance for CBC searches during these
science runs.Comment: 12 pages, 5 figure
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