6,495 research outputs found
"State Dependence and Long Term Site Capital in a Random Utility Model of Recreation Demand"
Conventional discrete choice Random Utility Maximization (RUM) models of recreation demand ignore the influence of knowledge, or site capital, gained over past trips on current site choice, despite its obvious impact. We develop a partially dynamic RUM model that incorporates a measure of site capital as an explanatory variable in an effort to address this shortcoming. To avoid the endogeneity of past and current trip choices, we estimate an auxiliary instrumental variable regression to purge site capital of its correlation with the error terms in current site utility. Our instrumental variable regression gives a fitted value ranging between 0 and 1 for each alternative for each person – a prediction of whether or not a person visited a site. Results suggest that the presence of accumulated site capital is an important predictor of current trips, and that failure to account for site capital will likely lead to underestimates of potential welfare effects.Random Utility Model; State Dependence; Non-Market Valuation
FAMILIAR AND FAVORITE SITES IN A RANDOM UTILITY MODEL OF BEACH RECREATION
We estimate a random utility model of recreation demand accounting for choice set familiarity and favorite sites. Our approach differs from existing approaches by retaining all sites in estimating the parameters of site utility. Familiar and unfamiliar sites are specified with different utility functions. Favored sites are assumed to have higher utility than nonfavored sites in estimation.Resource /Energy Economics and Policy,
Biologics May Prevent Cardiovascular Events in Rheumatoid Arthritis by Inhibiting Coronary Plaque Formation and Stabilizing High-Risk Lesions.
ObjectiveTo evaluate whether biologic disease-modifying antirheumatic drugs (DMARDs) decrease cardiovascular disease (CVD) risk in rheumatoid arthritis (RA) and whether biologic DMARDs might have a beneficial effect on coronary plaque formation or progression.MethodsIn this single-center observational cohort study, 150 patients underwent computed tomographic angiography for evaluation of coronary atherosclerosis (total, noncalcified, mixed/calcified, and low-attenuation plaque); 101 had repeat assessments within a mean ± SD of 6.9 ± 0.3 years to evaluate plaque progression. All CVD events were prospectively recorded, including cardiac death, myocardial infarction, unstable angina, revascularization, stroke, claudication, and hospitalization for heart failure. The Framingham-D'Agostino score was used to assess cardiovascular risk. The segment stenosis score was used to measure plaque burden. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated.ResultsAfter adjustment for the segment stenosis score, the Framingham-D'Agostino score, and time-varying Disease Activity Score in 28 joints using the C-reactive protein level using marginal structural models, current biologic DMARD use was associated with lower long-term CVD risk (OR 0.15 [95% CI 0.04-0.60]). Noncalcified and low-attenuation plaque presence moderated the effect of biologic DMARDs on CVD risk; specifically, biologic DMARD use was associated with lower CVD risk in patients with noncalcified or low-attenuation plaque at baseline (OR 0.21 [95% CI 0.04-0.99] and OR 0.08 [95% CI 0.01-0.70], respectively), but not in those without noncalcified or low-attenuation plaque. Per-segment plaque progression analyses showed that biologic DMARD exposure was associated with transition of noncalcified to mixed/calcified plaque (OR 4.00 [95% CI 1.05-15.32]). Biologic DMARD exposure predicted a lower likelihood of new plaque forming in segments without plaque among patients without mixed/calcified plaque in other coronary segments (OR 0.40 [95% CI 0.17-0.93]), but not among those with calcification. Biologic DMARD treatment also predicted low-attenuation plaque loss (P = 0.042).ConclusionOur findings indicate that in RA, biologic DMARD use is associated with reduced CVD risk, protective calcification of noncalcified lesions, and lower likelihood of new plaque formation in patients with early atherosclerosis
X-ray observations of the galaxy cluster PKS 0745-191: To the virial radius, and beyond
We measure X-ray emission from the outskirts of the cluster of galaxies PKS
0745-191 with Suzaku, determining radial profiles of density, temperature,
entropy, gas fraction, and mass. These measurements extend beyond the virial
radius for the first time, providing new information about cluster assembly and
the diffuse intracluster medium out to ~1.5 r_200, (r_200 ~ 1.7 Mpc ~ 15'). The
temperature is found to decrease by roughly 70 per cent from 0.3-1 r_200. We
also see a flattening of the entropy profile near the virial radius and
consider the implications this has for the assumption of hydrostatic
equilibrium when deriving mass estimates. We place these observations in the
context of simulations and analytical models to develop a better understanding
of non-gravitational physics in the outskirts of the cluster.Comment: 10 pages, 11 figures, accepted to MNRAS; expanded discussion of
analysis and uncertainties, results qualitatively unchange
The Unbearable Lightness of Debating: Performance Ambiguity and Social Influence
This chapter considers three sets of studies on how social influence affects perceptions of candidates\u27 performances in presidential debates. The first set shows that perceptions are influenced markedly by the reactions of peers watching the debate at the same time or by televised audiences shown on broadcast debates. The second set shows that expectations created by news accounts prior to debates also have significant impact and that different kinds of news accounts affect different viewers in distinct ways. Individuals with a high need for cognition respond well to more complicated messages that advance some reason as to why an apparently negative candidate characteristic may actually work in his or her favor. Those individuals do not respond well to simple assertions that a particular candidate will perform well. On the other hand, individuals with a low need for cognition show the opposite pattern. They respond to the simple but not the more complex messages. The third set of studies considers postdebate spin as well as predebate predictions. Although campaigns often use the strategy of lowering expectations before a debate by arguing that their candidate is disadvantaged and will not perform well, and then after the debate declare a surprising victory, our research suggests that this strategy is unlikely to work. It appears too manipulative. Generally, when campaign set expectations low, viewers perceive their candidate\u27s performance as weak
Integral Field Unit Observations of NGC 891: Kinematics of the Diffuse Ionized Gas Halo
We present high and moderate spectral resolution spectroscopy of diffuse
ionized gas (DIG) emission in the halo of NGC 891. The data were obtained with
the SparsePak integral field unit at the WIYN Observatory. The wavelength
coverage includes the [NII]6548,6583, Halpha, and [SII]6716,6731 emission
lines. Position-velocity (PV) diagrams, constructed using spectra extracted
from four SparsePak pointings in the halo, are used to examine the kinematics
of the DIG. Using two independent methods, a vertical gradient in azimuthal
velocity is found to be present in the northeast quadrant of the halo, with
magnitude approximately 15-18 km/s/kpc, in agreement with results from HI
observations. The kinematics of the DIG suggest that this gradient begins at
approximately 1 kpc above the midplane. In another part of the halo, the
southeast quadrant, the kinematics are markedly different, and suggest rotation
at about 175 km/s, much slower than the disk but with no vertical gradient. We
utilize an entirely ballistic model of disk-halo flow in an attempt to
reproduce the kinematics observed in the northeast quadrant. Analysis shows
that the velocity gradient predicted by the ballistic model is far too shallow.
Based on intensity cuts made parallel to the major axis in the ballistic model
and an Halpha image of NGC 891 from the literature, we conclude that the DIG
halo is much more centrally concentrated than the model, suggesting that
hydrodynamics dominate over ballistic motion in shaping the density structure
of the halo. Velocity dispersion measurements along the minor axis of NGC 891
seem to indicate a lack of radial motions in the halo, but the uncertainties do
not allow us to set firm limits.Comment: 31 pages, 10 figures. Accepted for publication in the Astrophysical
Journa
Is it the shape of the cavity, or the shape of the water in the cavity?
Historical interpretations of the thermodynamics characterizing biomolecular recognition have marginalized the role of water. An important (even, perhaps, dominant) contribution to molecular recognition in water comes from the “hydrophobic effect,” in which non-polar portions of a ligand interact preferentially with non-polar regions of a protein. Water surrounds the ligand, and water fills the binding pocket of the protein: when the protein-ligand complex forms, and hydrophobic surfaces of the binding pocket and the ligand approach one another, the molecules (and hydrogen-bonded networks of molecules) of water associated with both surfaces rearrange and, in part, entirely escape into the bulk solution. It is now clear that neither of the two most commonly cited rationalizations for the hydrophobic effect—an entropy-dominated hydrophobic effect, in which ordered waters at the surface of the ligand, and water at the surface of the protein, are released to the bulk upon binding, and a “lock-and-key” model, in which the surface of a ligand interacts directly with a surface of a protein having a complementary shape–can account for water-mediated interactions between the ligand and the protein, and neither is sufficient to account for the experimental observation of both entropy- andenthalpy-dominated hydrophobic effects. What is now clear is that there is no single hydrophobic effect, with a universally applicable, common, thermodynamic description: different processes (i.e., partitioning between phases of different hydrophobicity, aggregation in water, and binding) with different thermodynamics, depend on the molecular-level details of the structures of the molecules involved, and of the aggregates that form. A “water-centric” description of the hydrophobic effect in biomolecular recognition focuses on the structures of water surrounding the ligand, and of water filling the binding pocket of the protein, both before and after binding. This view attributes the hydrophobic effect to changes in the free energy of the networks of hydrogen bonds that are formed, broken, or re-arranged when two hydrophobic surfaces approach (but do not necessarily contact) one another. The details of the molecular topography (and the polar character) of the mole- cular surfaces play an important role in determining the structure of these networks of hydrogen-bonded waters, and in the thermodynamic description of the hydrophobic effect(s). Theorists have led the formulation of this “water-centric view”, although experiments are now supplying support for it. It poses complex problems for would-be “designers” of protein-ligand interactions, and for so-called “rational drug design”.Chemistry and Chemical Biolog
Magnification by Galaxy Group Dark Matter Halos
We report on the detection of gravitational lensing magnification by a
population of galaxy groups, at a significance level of 4.9 sigma. Using X-ray
selected groups in the COSMOS 1.64 deg^2 field, and high-redshift Lyman break
galaxies as sources, we measure a lensing-induced angular cross-correlation
between the samples. After satisfying consistency checks that demonstrate we
have indeed detected a magnification signal, and are not suffering from
contamination by physical overlap of samples, we proceed to implement an
optimally weighted cross-correlation function to further boost the signal to
noise of the measurement. Interpreting this optimally weighted measurement
allows us to study properties of the lensing groups. We model the full
distribution of group masses using a composite-halo approach, considering both
the singular isothermal sphere and Navarro-Frenk-White profiles, and find our
best fit values to be consistent with those recovered using the weak-lensing
shear technique. We argue that future weak-lensing studies will need to
incorporate magnification along with shear, both to reduce residual systematics
and to make full use of all available source information, in an effort to
maximize scientific yield of the observations.Comment: 6 pages, 3 figures, Accepted by Ap
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