9,339 research outputs found
Resolved Spectroscopy of the T8.5 and Y0-0.5 Binary WISEPC J121756.91+162640.2AB
We present 0.9 - 2.5 um resolved spectra for the ultracool binary WISEPC
J121756.91+162640.2AB. The system consists of a pair of brown dwarfs that
straddles the currently defined T/Y spectral type boundary. We use synthetic
spectra generated by model atmospheres that include chloride and sulfide clouds
(Morley et al.), the distance to the system (Dupuy & Kraus), and the radius of
each component based on evolutionary models (Saumon & Marley) to determine a
probable range of physical properties for the binary. The effective temperature
of the T8.5 primary is 550 - 600 K, and that of the Y0 - Y0.5 secondary is 450
K. The atmospheres of both components are either free of clouds or have
extremely thin cloud layers. We find that the masses of the primary and
secondary are 30 and 22 M_Jup, respectively, and that the age of the system is
4 - 8 Gyr. This age is consistent with astrometric measurements (Dupuy & Kraus)
that show that the system has kinematics intermediate between those of the thin
and thick disks of the Galaxy. An older age is also consistent with an
indication by the H - K colors that the system is slightly metal-poor.Comment: 21 pages which include 6 Figures and 3 Tables. Accepted on November 8
2013 for publication in Ap
An L Band Spectrum of the Coldest Brown Dwarf
The coldest brown dwarf, WISE 0855, is the closest known planetary-mass,
free-floating object and has a temperature nearly as cold as the solar system
gas giants. Like Jupiter, it is predicted to have an atmosphere rich in
methane, water, and ammonia, with clouds of volatile ices. WISE 0855 is faint
at near-infrared wavelengths and emits almost all its energy in the
mid-infrared. Skemer et al. 2016 presented a spectrum of WISE 0855 from 4.5-5.1
micron (M band), revealing water vapor features. Here, we present a spectrum of
WISE 0855 in L band, from 3.4-4.14 micron. We present a set of atmosphere
models that include a range of compositions (metallicities and C/O ratios) and
water ice clouds. Methane absorption is clearly present in the spectrum. The
mid-infrared color can be better matched with a methane abundance that is
depleted relative to solar abundance. We find that there is evidence for water
ice clouds in the M band spectrum, and we find a lack of phosphine spectral
features in both the L and M band spectra. We suggest that a deep continuum
opacity source may be obscuring the near-infrared flux, possibly a deep
phosphorous-bearing cloud, ammonium dihyrogen phosphate. Observations of WISE
0855 provide critical constraints for cold planetary atmospheres, bridging the
temperature range between the long-studied solar system planets and accessible
exoplanets. JWST will soon revolutionize our understanding of cold brown dwarfs
with high-precision spectroscopy across the infrared, allowing us to study
their compositions and cloud properties, and to infer their atmospheric
dynamics and formation processes.Comment: 19 pages, 21 figures. Accepted for publication in Ap
Cannabis and depression: A twin model approach to co-morbidity
Cannabis use disorder (CUD) co-occurs with major depressive disorder (MDD) more frequently than would be expected by chance. However, studies to date have not produced a clear understanding of the mechanisms underlying this co-morbidity. Genetically informative studies can add valuable insight to this problem, as they allow the evaluation of competing models of co-morbidity. This study uses data from the Australian Twin Registry to compare 13 co-morbidity twin models initially proposed by Neale and Kendler (Am J Hum Genet 57:935ā953, 1995). The analysis sample comprised 2410 male and female monozygotic and dizygotic twins (average age 32) who were assessed on CUD and MDD using the SSAGA-OZ interview. Data were analyzed in OpenMx. Of the 13 different co-morbidity models, two fit equally well: CUD causes MDD and Random Multiformity of CUD. Both fit substantially better than the Correlated Liabilities model. Although the current study cannot differentiate between them statistically, these models, in combination, suggest that CUD risk factors may causally influence the risk to develop MDD, but only when risk for CUD is high
The aging male: investigation, treatment and monitoring of late-onset hypogonadism in males
Androgen deficiency in the aging male has become a topic of increasing interest and debate throughout the world. The demographics clearly demonstrate the increasing percentage of the population that is in the older age groups. The data also support the concept that testosterone falls progressively with age and that a significant percentage of men over the age of 60 years have serum testosterone levels that are below the lower limits of young adults (age 20-30 years) men. The principal questions raised by these observations are whether older hypogonadal men will benefit from testosterone treatment and what will be the risks associated with such intervention. The past decade has brought evidence of benefit of androgen treatment on multiple target organs of hypogonadal men and recent studies show short-term beneficial effects of testosterone in older men that are similar to those in younger men. Long-term data on the effects of testosterone treatment in the older population are limited and specific risk data on the prostate and cardiovascular systems are needed. Answers to key questions of functional benefits that may retard frailty of the elderly are not yet available. The recommendations described below were prepared for the International Society of Andrology (ISA) and the International Society for the Study of the Aging Male (ISSAM) following a panel discussion with active participation from the audience sponsored by the ISA on the topic at the 4th ISSAM Congress in Prague in February 2004.peer-reviewe
An analytical model for the detection of levitated nanoparticles in optomechanics
Interferometric position detection of levitated particles is crucial for the
centre-of-mass (CM) motion cooling and manipulation of levitated particles. In
combination with balanced detection and feedback cooling, this system has
provided picometer scale position sensitivity, zeptonewton force detection, and
sub-millikelvin CM temperatures. In this article, we develop an analytical
model of this detection system and compare its performance with experimental
results allowing us to explain the presence of spurious frequencies in the
spectra
Framework for better living with HIV in England
Duration: April 2007 - May 2009
Sigma Research was funded by Terrence Higgins Trust to co-ordinate the development of a framework to address the health, social care, support and information needs of people with diagnosed HIV in England. It has now been published as the Framework for better living with HIV in England.
The over-arching goal of the framework is that all people with diagnosed HIV in England "are enabled to have the maximum level of health, well-being, quality of life and social integration". In its explanation of how this should occur the document presents a road map for social care, support and information provision to people with diagnosed HIV in England. By establishing and communicating aims and objectives, the framework should build consensus and provide a means to establish how interventions could be prioritised and coordinated. The key drivers for the framework were clearly articulated ethical principles, agreed by all those who sign up to it, and an inclusive social development / health promotion approach.
Sigma Research worked on the framework with a range of other organisations who sent representatives to a Framework Development Group (see below for membership). The framework is evidence-based and seeks to:
Promote and protect the rights and well-being of all people with HIV in England.
Maximise the capacity of individuals and groups of people with HIV to care for, advocate and represent themselves effectively.
Improve and protect access to appropriate information, social support, social care and clinical services.
Minimise social, economic, governmental and judicial change detrimental to the health and well being of people with HIV.
Alongside the development of the framework, Sigma Research undertook a national needs assessment among people with diagnosed HIV across the UK called What do you need?. These two projects informed and supported each other.
Framework Development Group included:
African HV Policy Network
Black Health Agency
George House Trust
NAM
NAT (National AIDS Trust)
Positively Women
Terrence Higgins Trus
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