2,351 research outputs found
HMO Penetration, Ownership Status, and the Rise of Hospital Advertising
We examine the recent increase in hospital advertising expenditures. We first illustrate that the rise in hospital advertising has not been universal. Large, not-for-profit, teaching hospitals have, by far, experienced the largest increase in spending. Adjusting for size, for-profit hospitals over this period have actually decreased their marketing expenses. This increase in advertising spending is best explained by managed care penetration. There is a small and marginally significant relationship between increases in for-profit presence in hospital markets and an increase in advertising spending by the not-for-profit hospitals in those markets.
A Multi-Wavelength Study of Luminous Infrared Galaxies across Cosmic Time.
Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017
Collisionless energy transfer in kinetic turbulence: field-particle correlations in Fourier space
Turbulence is ubiquitously observed in nearly collisionless heliospheric
plasmas, including the solar wind and corona and the Earth's magnetosphere.
Understanding the collisionless mechanisms responsible for the energy transfer
from the turbulent fluctuations to the particles is a frontier in kinetic
turbulence research. Collisionless energy transfer from the turbulence to the
particles can take place reversibly, resulting in non-thermal energy in the
particle velocity distribution functions (VDFs) before eventual collisional
thermalization is realized. Exploiting the information contained in the
fluctuations in the VDFs is valuable. Here we apply a recently developed method
based on VDFs, the field-particle correlation technique, to a ,
solar-wind-like, low-frequency Alfv\'enic turbulence simulation with well
resolved phase space to identify the field-particle energy transfer in velocity
space. The field-particle correlations reveal that the energy transfer,
mediated by the parallel electric field, results in significant structuring of
the ion and electron VDFs in the direction parallel to the magnetic field.
Fourier modes representing the length scales between the ion and electron
gyroradii show that energy transfer is resonant in nature, localized in
velocity space to the Landau resonances for each Fourier mode. The energy
transfer closely follows the Landau resonant velocities with varying
perpendicular wavenumber and plasma . This resonant signature,
consistent with Landau damping, is observed in all diagnosed Fourier modes that
cover the dissipation range of the simulation.Comment: 31 pages, accepted by JPP, minor improvements compared to v
Dusty Disks Around Central Stars of Planetary Nebulae
Only a few percent of cool, old white dwarfs (WDs) have infrared excesses
interpreted as originating in small hot disks due to the infall and destruction
of single asteroids that come within the star's Roche limit. Infrared excesses
at 24 micron were also found to derive from the immediate vicinity of younger,
hot WDs, most of which are still central stars of planetary nebulae (CSPN). The
incidence of CSPN with this excess is 18%. The Helix CSPN, with a 24 micron
excess, has been suggested to have a disk formed from collisions of Kuiper
belt-like objects (KBOs). In this paper, we have analyzed an additional sample
of CSPN to look for similar infrared excesses. These CSPN are all members of
the PG 1159 class and were chosen because their immediate progenitors are known
to often have dusty environments consistent with large dusty disks. We find
that, overall, PG 1159 stars do not present such disks more often than other
CSPN, although the statistics (5 objects) are poor. We then consider the entire
sample of CSPN with infrared excesses, and compare it to the infrared
properties of old WDs, as well as cooler post-AGB stars. We conclude with the
suggestion that the infrared properties of CSPN more plausibly derive from
AGB-formed disks rather than disks formed via the collision of KBOs, although
the latter scenario cannot be ruled out. We finally remark that there seems to
be an association between CSPN with a 24 micron excess and confirmed or
possible binarity of the central star.Comment: 11 pages, 5 figures, AJ, in pres
Effect of metallization on electrical performance of surface acoustic wave resonators
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaf 79).by Jason W. Chu.M.Eng
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