37,777 research outputs found
Yoga practice in the UK: a cross- sectional survey of motivation, health benefits and behaviours
Objectives Despite the popularity of yoga and evidence of its positive effects on physical and mental health, little is known about yoga practice in the UK. This study investigated the characteristics of people who practise yoga, reasons for initiating and maintaining practice, and perceived impact of yoga on health and well-being.
Design, setting and participants A cross-sectional online anonymous survey distributed through UK-based yoga organisations, studios and events, through email invites and flyers. 2434 yoga practitioners completed the survey, including 903 yoga teachers: 87% were women, 91% white and 71% degree educated; mean age was 48.7 years.
Main outcome measures Perceived impact of yoga on health conditions, health outcomes and injuries. Relationships between yoga practice and measures of health, lifestyle, stress and well-being.
Results In comparison with national population norms, participants reported significantly higher well-being but also higher anxiety; lower perceived stress, body mass index and incidence of obesity, and higher rates of positive health behaviours. 47% reported changing their motivations to practise yoga, with general wellness and fitness key to initial uptake, and stress management and spirituality important to current practice. 16% of participants reported starting yoga to manage a physical or mental health condition. Respondents reported the value of yoga for a wide range of health conditions, most notably for musculoskeletal and mental health conditions. 20.7% reported at least one yoga-related injury over their lifetime. Controlling for demographic factors, frequency of yoga practice accounted for small but significant variance in health-related regression models (p<0.001).
Conclusion The findings of this first detailed UK survey were consistent with surveys in other Western countries. Yoga was perceived to have a positive impact on physical and mental health conditions and was linked to positive health behaviours. Further investigation of yoga’s role in self-care could inform health-related challenges faced by many countries
Determinants of the Timing and Incidence of Exploratory Drilling on Offshort Wildcat Tracts
This paper documents exploratory drilling activity on offshore wildcat oil and gas leases in the Gulf of Mexico that were sold between 1954 and 1990, with emphasis on the period before 1980. For each year of the lease, we study the determinants of the decision whether or not to begin exploratory drilling, and the outcome of any drilling activity. Our results indicate that equilibrium predictions of plausible noncooperative models are reasonably accurate, and more descriptive than those of cooperative models of drilling timing. We discuss why noncooperative behavior may occur, and the potential gains from coordination.
A homotopy double groupoid of a Hausdorff space II: a van Kampen theorem
This paper is the second in a series exploring the properties of a functor
which assigns a homotopy double groupoid with connections to a Hausdorff space.
We show that this functor satisfies a version of the van Kampen theorem, and
so is a suitable tool for nonabelian, 2-dimensional, local-to-global problems.
The methods are analogous to those developed by Brown and Higgins for similar
theorems for other higher homotopy groupoids.
An integral part of the proof is a detailed discussion of commutative cubes
in a double category with connections, and a proof of the key result that any
composition of commutative cubes is commutative. These results have recently
been generalised to all dimensions by Philip Higgins.Comment: 19 pages, uses picte
Patterns of Trade in the Market for Used Durables: Theory and Evidence
The consumption value of a durable good diminishes as it ages due to physical deterioration and consumers' preference for the new. We develop a model of consumer specialization and trade in the market for used durables based on imperfect substitutability. Imperfect substitutability across vintages is reflected in a declining market price over time. Heterogeneous consumers maximize utility by specializing in durables of differing ages. Consumers must trade to acquire their preferred vintage each period. When there are transaction costs in the secondhand market, the volume of trade due to specialization increases with imperfect substitutability. We examine the determinants of vehicle ownership transfers in Illinois, a measure of trade volume. Observed patterns of trade across automobile model years are consistent with our model, and inconsistent with a model of adverse selection.
Ohio School Milk Markets: An Analysis of Bidding
We examine the institutional details of the school milk procurement process, bidding data, statements of dairy executives, and supply characteristics in Ohio during the 1980's. We compare the bidding behavior of a group of firms to a control group. We find that the behavior of each of the firms differs from that of the control group. We argue that the behavior of these firms is consistent with collusion. The estimated average effect of collusion on market prices is about six and one half percent, or roughly the cost of shipping school milk about 50 miles.
The Abundances of Light Neutron-Capture Elements in Planetary Nebulae III. The Impact of New Atomic Data on Nebular Selenium and Krypton Abundance Determinations
The detection of neutron(n)-capture elements in several planetary nebulae
(PNe) has provided a new means of investigating s-process nucleosynthesis in
low-mass stars. However, a lack of atomic data has inhibited accurate
trans-iron element abundance determinations in astrophysical nebulae. Recently,
photoionization and recombination data were determined for Se and Kr, the two
most widely detected n-capture elements in nebular spectra. We have
incorporated these new data into the photoionization code Cloudy. To test the
atomic data, numerical models were computed for 15 PNe that exhibit emission
lines from multiple Kr ions. We found systematic discrepancies between the
predicted and observed emission lines that are most likely caused by inaccurate
photoionization and recombination data. These discrepancies were removed by
adjusting the Kr--Kr photoionization cross sections within their
cited uncertainties and the dielectronic recombination rate coefficients by
slightly larger amounts. From grids of models spanning the physical conditions
encountered in PNe, we derive new, broadly applicable ionization correction
factor (ICF) formulae for calculating Se and Kr elemental abundances. The ICFs
were applied to our previous survey of near-infrared [Kr III] and [Se IV]
emission lines in 120 PNe. The revised Se and Kr abundances are 0.1-0.3 dex
lower than former estimates, with average values of [Se/(O, Ar)]=0.120.27
and [Kr/(O, Ar)]=0.820.29, but correlations previously found between their
abundances and other nebular and stellar properties are unaffected. We also
find a tendency for high-velocity PNe that can be associated with the Galactic
thick disk to exhibit larger s-process enrichments than low-velocity PNe
belonging to the thin disk population.Comment: 73 pages, 6 figures, 18 tables, accepted for publication in ApJ
Bayesian Semiparametric Hierarchical Empirical Likelihood Spatial Models
We introduce a general hierarchical Bayesian framework that incorporates a
flexible nonparametric data model specification through the use of empirical
likelihood methodology, which we term semiparametric hierarchical empirical
likelihood (SHEL) models. Although general dependence structures can be readily
accommodated, we focus on spatial modeling, a relatively underdeveloped area in
the empirical likelihood literature. Importantly, the models we develop
naturally accommodate spatial association on irregular lattices and irregularly
spaced point-referenced data. We illustrate our proposed framework by means of
a simulation study and through three real data examples. First, we develop a
spatial Fay-Herriot model in the SHEL framework and apply it to the problem of
small area estimation in the American Community Survey. Next, we illustrate the
SHEL model in the context of areal data (on an irregular lattice) through the
North Carolina sudden infant death syndrome (SIDS) dataset. Finally, we analyze
a point-referenced dataset from the North American Breeding Bird survey that
considers dove counts for the state of Missouri. In all cases, we demonstrate
superior performance of our model, in terms of mean squared prediction error,
over standard parametric analyses.Comment: 29 pages, 3 figue
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