11,147 research outputs found
A New Low-Mass Eclipsing Binary from SDSS-II
We present observations of a new low-mass double-lined eclipsing binary
system discovered using repeat observations of the celestial equator from the
Sloan Digital Sky Survey II. Using near-infrared photometry and optical
spectroscopy we have measured the properties of this short-period
[P=0.407037(14) d] system and its two components. We find the following
parameters for the two components: M_1=0.272+/-0.020 M_sun, R_1=0.268+/-0.010
R_sun, M_2=0.240+/-0.022 M_sun, R_2=0.248+/-0.0090 R_sun, T_1=3320+/-130 K,
T_2=3300+/-130 K. The masses and radii of the two components of this system
agree well with theoretical expectations based on models of low-mass stars,
within the admittedly large errors. Future synoptic surveys like Pan-STARRS and
LSST will produce a wealth of information about low-mass eclipsing systems and
should make it possible, with an increased reliance on follow-up observations,
to detect many systems with low-mass and sub-stellar companions. With the large
numbers of objects for which these surveys will produce high-quality
photometry, we suggest that it becomes possible to identify such systems even
with sparse time sampling and a relatively small number of individual
observations.Comment: 15 Pages, 9 Figures, 6 Tables. Replaced with version accepted to Ap
Who is in the transition gap? Transition from CAMHS to AMHS in the Republic of Ireland
Objective: The ITRACK study explored the process and predictors of transition between Child and Adolescent Mental Health Services (CAMHS) and Adult Mental Health Services (AMHS) in the Republic of Ireland. Method: Following ethical approval, clinicians in each of Ireland's four Health Service Executive (HSE) areas were contacted, informed about the study and invited to participate. Clinicians identified all cases who had reached the transition boundary (i.e. upper age limit for that CAMHS team ) between January and December 2010. Data were collected on clinical and socio-demographic details and factors that informed the decision to refer or not refer to AMHS and case notes were scrutinised to ascertain the extent of information exchanged between services during transition
Successful ageing in an area of deprivation: Part 1—A qualitative exploration of the role of life experiences in good health in old age
Objectives: To determine the life histories and current circumstances of healthy and unhealthy older people who share an ecology marked by relative deprivation and generally poor health.
Study design: In-depth interview study with a qualitative analysis.
Methods: Matched pairs of healthy and unhealthy ‘agers’ were interviewed face-to-face. Healthy ageing was assessed in terms of hospital morbidity and self-reported health. Study participants consisted of 22 pairs (44 individuals), aged 72–89 years, matched for sex, age and deprivation category, and currently resident in the West of Scotland. All study participants were survivors of the Paisley/Renfrew (MIDSPAN) survey, a longitudinal study commenced in 1972 with continuous recording of morbidity and mortality since.
Detailed life histories were obtained which focused on family, residence, employment, leisure and health. This information was supplemented by more focused data on ‘critical incidents’, financial situation and position in social hierarchies.
Results: Data provided rich insights into life histories and current circumstances but no differences were found between healthy and unhealthy agers.
Conclusions: It is important to understand what differentiates individuals who have lived in circumstances characterized by relative deprivation and poor health, yet have aged healthily. This study collected rich and detailed qualitative data. Yet, no important differences were detected between healthy and unhealthy agers. This is an important negative result as it suggests that the phenomenon of healthy ageing and the factors that promote healthy ageing over a lifetime are so complex that they will require even more detailed studies to disentangle
Multiepoch Radial Velocity Observations of L Dwarfs
We report on the development of a technique for precise radial-velocity
measurements of cool stars and brown dwarfs in the near infrared. Our technique
is analogous to the Iodine (I2) absorption cell method that has proven so
successful in the optical regime. We rely on telluric CH4 absorption features
to serve as a wavelength reference, relative to which we measure Doppler shifts
of the CO and H2O features in the spectra of our targets. We apply this
technique to high-resolution (R~50,000) spectra near 2.3 micron of nine L
dwarfs taken with the Phoenix instrument on Gemini-South and demonstrate a
typical precision of 300 m/s. We conduct simulations to estimate our expected
precision and show our performance is currently limited by the signal-to-noise
of our data. We present estimates of the rotational velocities and systemic
velocities of our targets. With our current data, we are sensitive to
companions with M sin i > 2MJ in orbits with periods less than three days. We
identify no companions in our current data set. Future observations with
improved signal-to-noise should result in radial-velocity precision of 100 m/s
for L dwarfs.Comment: Accepted for publication in ApJ, 24 pages, 7 figure
Option value: improving resource allocation efficiency
Measuring consumer benefits associated with a policy or a project in a world where prices and outcomes are known with certainty is, at least in theory, straightforward. Changes in consumer surplus provide an appropriate measure of a policy's contribution to consumer welfare. But, in a world where prices and outcomes are uncertain, there is a strong case for concluding that measuring expected consumer surplus alone is inadequate (Bishop, 1982), and in many natural resource situations, uncertainty is the rule rather than the exception. Option value is the adjustment, if any, that is made to expected consumer surplus when there is uncertainty about the demand or supply of an environmental asset.
The concept of option value is based on Weisbrod's (1964) argument that consumers, uncertain about their future demands for a commodity, would be willing to pay something above expected consumer surplus to maintain an option to consume the commodity in the future. As we have noted, this additional ""payment"" is option value. While Weisbrod's argument suggests that option value is positive, this need not be the case. A variety of authors have proven that option value can take either sign, depending on the specific circumstances, and especially on the type of uncertainty involved. We begin with an overview of the origin of option value in economics and its relevance to decision making under uncertainty. The next chapter considers compensation tests and identifies an ex ante compensation test as being appropriate for uncertain situations. Option value is then located within a total value framework that includes use values and existence values. Uncertainty in both demand and supply is then shown to provide justification for considering option value as an adjustment that individuals make to allow for uncertainty. However, we will show that there are few situations where the sign of option value can be unambiguously established in theory. The final chapters of the publication describe how option value can be measured and incorporated into cost-benefit analysis.This research was supported by a grant from the Foundation for Research
Science and Technology, It constitutes Project 2 in the Centre for Resource Management's research
programme for 1990/91
GAP WORK project report: training for youth practitioners on tackling gender-related violence
This project sought to challenge gender-related violence against (and by) children and young people by developing training for practitioners who have everyday contact with general populations of children and young people (‘youth practitioners’). Through improved knowledge and understanding practitioners can better identify and challenge sexist, sexualising, homophobic or controlling language and behaviour, and know when and how to refer children and young people to the most appropriate support services. This summary outlines the Project and our initial findings about the success of the four training programmes developed and piloted.Co-funded by the DAPHNE III programme of the EU
Nonmarket valuation of water quality: Addressing spatially heterogeneous preferences using GIS and a random parameter logit model
The spatial distribution of agri-environmental policy benefits has important implications for the efficient allocation of management effort. The practical convenience of relying on sample mean values of individual benefits for aggregation can come at the cost of biased aggregate estimates. The main objective of this paper is to test spatial hypotheses regarding respondents' local water quality and quantity, and their willingness-to-pay for improvements in water quality attributes. This paper combines choice experiment and spatially related water quality data via a Geographical Information System (GIS) to develop a method that evaluates the influence of respondents' local water quality on willingness-to-pay for river and stream conservation programmes in Canterbury, New Zealand. Results showed that those respondents who live in the vicinity of low quality waterways are willing to pay more for improvements relative to those who live near to high quality waterways. The study also found that disregarding the influence of respondents' local water quality data has a significant impact on the magnitude of welfare estimates and causes substantial underestimation of aggregated benefits
Sampling Time Effects for Persistence and Survival in Step Structural Fluctuations
The effects of sampling rate and total measurement time have been determined
for single-point measurements of step fluctuations within the context of
first-passage properties. Time dependent STM has been used to evaluate step
fluctuations on Ag(111) films grown on mica as a function of temperature
(300-410 K), on screw dislocations on the facets of Pb crystallites at 320K,
and on Al-terminated Si(111) over the temperature range 770K - 970K. Although
the fundamental time constant for step fluctuations on Ag and Al/Si varies by
orders of magnitude over the temperature ranges of measurement, no dependence
of the persistence amplitude on temperature is observed. Instead, the
persistence probability is found to scale directly with t/Dt where Dt is the
time interval used for sampling. Survival probabilities show a more complex
scaling dependence which includes both the sampling interval and the total
measurement time tm. Scaling with t/Dt occurs only when Dt/tm is a constant. We
show that this observation is equivalent to theoretical predictions that the
survival probability will scale as Dt/L^z, where L is the effective length of a
step. This implies that the survival probability for large systems, when
measured with fixed values of tm or Dt should also show little or no
temperature dependence.Comment: 27 pages, 10 figure
- …
