1,375 research outputs found
Choptuik scaling in six dimensions
We perform numerical simulations of the critical gravitational collapse of a
spherically symmetric scalar field in 6 dimensions. The critical solution has
discrete self-similarity. We find the critical exponent \gamma and the
self-similarity period \Delta.Comment: 8 pages, 3 figures RevTe
Collapse of a Circular Loop of Cosmic String
We study the collapse of a circular loop of cosmic string. The gravitational
field of the string is treated using the weak field approximation. The
gravitational radiation from the loop is evaluated numerically. The memtric of
the loop near the point of collapse is found analytically.Comment: 15 page
Barriers to guideline-concordant antibiotic use among inpatient physicians: A case vignette qualitative study
BACKGROUND:
Greater adherence to antibiotic-prescribing guidelines may promote more judicious antibiotic use, which could benefit individual patients and society at large.
OBJECTIVE:
To assess physician knowledge and acceptance of antibiotic-prescribing guidelines through the use of case vignettes.
DESIGN:
We conducted semistructured interviews with 30 inpatient physicians. Participants were asked to respond to 3 hypothetical case vignettes: (1) a skin and soft tissue infection (SSTI), (2) suspected hospital-acquired pneumonia (HAP), and (3) asymptomatic bacteriuria (ASB). All participants received feedback according to guidelines from the Infectious Diseases Society of America (IDSA) and were asked to discuss their level of comfort with following these guidelines.
SETTING:
Two acute care teaching hospitals for adult patients.
INTERVENTION:
None.
MEASUREMENTS:
Data from transcribed interviews were analyzed using emergent thematic analysis.
RESULTS:
Participants were receptive to guidelines and believed they were useful. However, participants' responses to the case vignettes demonstrated that IDSA guideline recommendations were not routinely followed for SSTI, HAP, and ASB. We identified 3 barriers to guideline-concordant care: (1) physicians' lack of awareness of specific guideline recommendations; (2) tension between adhering to guidelines and the desire to individualize patient care; and (3) skepticism of certain guideline recommendations.
CONCLUSIONS:
Case vignettes may be useful tools to assess physician knowledge and acceptance of antibiotic-prescribing guidelines. Using case vignettes, we identified 3 barriers to following IDSA guidelines. Efforts to improve guideline-concordant antibiotic prescribing should focus on reducing such barriers at the local level
Scaling of curvature in sub-critical gravitational collapse
We perform numerical simulations of the gravitational collapse of a
spherically symmetric scalar field. For those data that just barely do not form
black holes we find the maximum curvature at the position of the central
observer. We find a scaling relation between this maximum curvature and
distance from the critical solution. The scaling relation is analogous to that
found by Choptuik for black hole mass for those data that do collapse to form
black holes. We also find a periodic wiggle in the scaling exponent.Comment: Revtex, 2 figures, Discussion modified, to appear in Phys. Rev.
Tensor mass and particle number peak at the same location in the scalar-tensor gravity boson star models - an analytical proof
Recently in boson star models in framework of Brans-Dicke theory, three
possible definitions of mass have been identified, all identical in general
relativity, but different in scalar-tensor theories of gravity.It has been
conjectured that it's the tensor mass which peaks, as a function of the central
density, at the same location where the particle number takes its maximum.This
is a very important property which is crucial for stability analysis via
catastrophe theory. This conjecture has received some numerical support. Here
we give an analytical proof of the conjecture in framework of the generalized
scalar-tensor theory of gravity, confirming in this way the numerical
calculations.Comment: 9 pages, latex, no figers, some typos corrected, reference adde
Black holes and a scalar field in an expanding universe
We consider a model of an inhomogeneous universe including a massless scalar
field, where the inhomogeneity is assumed to consist of many black holes. This
model can be constructed by following Lindquist and Wheeler, which has already
been investigated without including scalar field to show that an averaged scale
factor coincides with that of the Friedmann model. In this work we construct
the inhomogeneous universe with an massless scalar field, where we assume that
the averaged scale factor and scalar field are given by those of the Friedmann
model including a scalar field. All of our calculations are carried out in the
framework of Brans-Dicke gravity. In constructing the model of an inhomogeneous
universe, we define the mass of a black hole in the Brans-Dicke expanding
universe which is equivalent to ADM mass if the mass evolves adiabatically, and
obtain an equation relating our mass to the averaged scalar field and scale
factor. As the results we find that the mass has an adiabatic time dependence
in a sufficiently late stage of the expansion of the universe, and that the
time dependence is qualitatively diffenrent according to the sign of the
curvature of the universe: the mass increases decelerating in the closed
universe case, is constant in the flat case and decreases decelerating in the
open case. It is also noted that the mass in the Einstein frame depends on
time. Our results that the mass has a time dependence should be retained even
in the general scalar-tensor gravitiy with a scalar field potential.
Furthermore, we discuss the relation of our results to the uniqueness theorem
of black hole spacetime and gravitational memory effect.Comment: 16 pages, 3 tables, 5 figure
Inhomogeneity of Spatial Curvature for Inflation
We study how the initial inhomogeneities of the spatial curvature affect the
onset of inflation in the closed universe. We consider a cosmological model
which contains a radiation and a cosmological constant. In order to treat the
inhomogeneities in the closed universe, we improve the long wavelength
approximation such that the non-small spatial curvature is tractable in the
lowest order. Using the improved scheme, we show how large inhomogeneities of
the spatial curvature prevent the occurrence of inflation.Comment: 17 pages, revtex, 6 figures included using eps
The Budget Enforcement Act in 1992: Necessary But Not Sufficient
The 1992 budget process followed the Budget Enforcement Act of 1990 (BEA) script,
although not without a protracted conflict concerning the walls separating the three
categories of discretionary spending. The walls were retained, spending caps were
met, and the process was timely. What deficit reduction occurred was the result of
spending below the FY 1993 defense cap. Congress neither raised taxes nor cut
entitlements to reduce the deficit further. The deficit grew significantly, driven by
entitlement spending, chiefly health care programs. The limits of the BEA approach to
spending control and deficit reduction became apparent
Long-wavelength approximation for string cosmology with barotropic perfect fluid
The field equations derived from the low energy string effective action with
a matter tensor describing a perfect fluid with a barotropic equation of state
are solved iteratively using the long-wavelength approximation, i.e. the field
equations are expanded by the number of spatial gradients. In the zero order, a
quasi-isotropic solution is presented and compared with the general solution of
the pure dilaton gravity. Possible cosmological models are analyzed from the
point of view of the pre-big bang scenario. The second order solutions are
found and their growing and decaying parts are studied.Comment: 19 pages, 1 figur
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