11,076 research outputs found
DEMAND THEORY: TIME ALLOCATION AND OUTDOOR RECREATION
Resource /Energy Economics and Policy,
Recommended from our members
Lepidochelys kempii
Number of Pages: 8Integrative BiologyGeological Science
IMPORT DEMAND FOR RICE IN THE EEC: IMPLICATIONS OF U.S. MARKET PROMOTION
Demand and Price Analysis,
EVALUATING INCENTIVE PAYMENT PROGRAMS THROUGH AGGREGATE PRODUCTION RESPONSE: THE CASE OF MOHAIR
Production Economics,
The V471 Tauri System: A Multi-datatype Probe
V471 Tauri, a white dwarf--red dwarf eclipsing binary in the Hyades, is well
known for stimulating development of common envelope theory, whereby novae and
other cataclysmic variables form from much wider binaries by catastrophic orbit
shrinkage. Our evaluation of a recent imaging search that reported negative
results for a much postulated third body shows that the object could have
escaped detection or may have actually been seen. The balance of evidence
continues to favor a brown dwarf companion about 12 AU from the eclipsing
binary. A recently developed algorithm finds unified solutions from three
datatypes. New radial velocities (RVs) of the red dwarf and BV RCIC light
curves are solved simultaneously along with white dwarf and red dwarf RVs from
the literature, uvby data, the MOST mission light curve, and 40 years of
eclipse timings. Precision-based weighting is the key to proper information
balance among the various datasets. Timewise variation of modeled starspots
allows unified solution of multiple data eras. Light curve amplitudes strongly
suggest decreasing spottedness from 1976 to about 1980, followed by
approximately constant spot coverage from 1981 to 2005. An explanation is
proposed for lack of noticeable variation in 1981 light curves, in terms of
competition between spot and tidal variations. Photometric spectroscopic
distance is estimated. The red dwarf mass comes out larger than normal for a
K2V star, and even larger than adopted in several structure and evolution
papers. An identified cause for this result is that much improved red dwarf RVs
curves now exist
Modulations in Multi-Periodic Blue Variables in the LMC
As shown by Mennickent, et al(2003), a subset of the blue variable stars in
the Large Magellanic Cloud exhibit brightness variability of small amplitude in
the period range 2.4 to 16 days as well as larger amplitude variability with
periods of 140 to 600 days, with a remarkably tight relation between the long
and the short periods. Our re-examination of these objects has led to the
discovery of additional variability. The Fourier spectra of 11 of their 30
objects have 3 or 4 peaks above the noise level and a linear relation of the
form f_a = 2(f_b - f_L) among three of the frequencies. An explanation of this
relation requires an interplay between the binary motion and that of a third
object. The two frequency relations together with the Fourier amplitude ratios
pose a challenging modeling problem.Comment: 4 pages, 3 figures, Astrophysical Journal (in press
Awareness of stroke warning signs, risk factors and response to stroke: a hospital based survey
Background: Stroke is the third most common cause of mortality and a significant cause of disability in India. Knowledge about stroke risk factors, warning signs and appropriate response to stroke are important to reduce the morbidity. Aim was to evaluate the awareness and response to stroke among the public.
Methods: In this prospective, observational study, stroke awareness questioner was administered to 105 participants, who were relatives of patients without history of stroke attending the outpatient department of a tertiary care hospital.
Results: The mean age of the study participants was 49.7±11.9 years (range 24-69years) with 46 (44%) women. Thirty six percent of the subjects recognized brain as the affected organ in stroke. The common risk factors identified by the participants were diabetes mellitus in 30 (28.6%), hypertension in 27 (25.7%), high cholesterol in 15 (14.3%). Commonly identified warning signs were paralysis of one side of the body (56; 53%), deviation of mouth (21; 20%), speech impairment (17; 16%). On having/seeing a warning sign, 27 (25.7%) replied the appropriate response of rushing to emergency department of a hospital. Eleven (10.5%) were aware of clot lysis as the treatment for stroke and 9 (8.7%) the availability of this treatment at free of cost in Government hospitals in Tamil Nadu. Five (4.8%) participants responded that they should rush to hospital within the golden hour.
Conclusions: Knowledge about organ involved, etiology, and response to stroke warning signs are lacking and continuous education programs are necessary to improve the public awareness
Fluorescence and Chromospheric Activity of V471 Tau
The red dwarf + white dwarf eclipsing binary V471 Tau shows a variable Hα feature that varies from absorption during eclipse to maximum emission during white dwarf transit. In 1998 we obtained simultaneous BVRI photometry and Hα spectroscopy, with thorough phase coverage of the 12.5 hour orbital period. A binary star model was used with our light curve, radial velocity, and Hα data to refine stellar and orbital parameters. Combined absorption-emission profiles were generated by the model and fit to the observations, yielding a red star radius of 0.94⊙. Orbital inclination 78° is required with this size and other known parameters. The model includes three spots 1,000 K cooler than the surrounding photosphere. The variable Hα profile was modeled as a chromospheric region (essentially on the surface of the red star) centered at the substellar point. Additional emission seen outside our modeled profiles may be large co-rotating prominences that complicate the picture
Quarkonia in Hamiltonian Light-Front QCD
A constituent parton picture of hadrons with logarithmic confinement
naturally arises in weak coupling light-front QCD. Confinement provides a mass
gap that allows the constituent picture to emerge. The effective renormalized
Hamiltonian is computed to , and used to study charmonium and
bottomonium. Radial and angular excitations can be used to fix the coupling
, the quark mass , and the cutoff . The resultant hyperfine
structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much
more reader-friendly); corrected error in self-energ
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