8,264 research outputs found
The non-uniform, dynamic atmosphere of Betelgeuse observed at mid-infrared wavelengths
We present an interferometric study of the continuum surface of the red
supergiant star Betelgeuse at 11.15 microns wavelength, using data obtained
with the Berkeley Infrared Spatial Interferometer each year between 2006 and
2010. These data allow an investigation of an optically thick layer within 1.4
stellar radii of the photosphere. The layer has an optical depth of ~1 at 11.15
microns, and varies in temperature between 1900 K and 2800 K and in outer
radius between 1.16 and 1.36 stellar radii. Electron-hydrogen atom collisions
contribute significantly to the opacity of the layer. The layer has a
non-uniform intensity distribution that changes between observing epochs. These
results indicate that large-scale surface convective activity strongly
influences the dynamics of the inner atmosphere of Betelgeuse, and mass-loss
processes.Comment: 13 pages, 5 figures, in press (ApJ
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Improving Hospital Efficiency: A Process Model of Organizational Change Commitments
Improving hospital efficiency is a critical goal for managers and policy makers. We draw on participant observation of the perioperative coaching program in seven Ontario hospitals to develop knowledge of the process by which the content of change initiatives to increase hospital efficiency is defined. The coaching program was a change initiative involving the use of external facilitators with the goal of increasing perioperative efficiency. Focusing on the role of subjective understandings in shaping initiatives to improve efficiency, we show that physicians, nurses, administrators, and external facilitators all have differing frames of the problems that limit efficiency, and propose different changes that could enhance efficiency. Dynamics of strategic and contested framing ultimately shaped hospital change commitments. We build on work identifying factors that enhance the success of change efforts to improve hospital efficiency, highlighting the importance of subjective understandings and the politics of meaning-making in defining what hospitals change
The Bose-Einstein correlation function from a Quantum Field Theory point of view
We show that a recently proposed derivation of Bose-Einstein correlations
(BEC) by means of a specific version of thermal Quantum Field Theory (QFT),
supplemented by operator-field evolution of the Langevin type, allows for a
deeper understanding of the possible coherent behaviour of the emitting source
and a clear identification of the origin of the observed shape of the BEC
function . Previous conjectures in this matter obtained by other
approaches are confirmed and have received complementary explanation.Comment: Some misprints corrected. To be publishe in Phys. Rev.
Capture Velocity for a Magneto-Optical Trap in a Broad Range of Light Intensity
In a recent paper, we have used the dark-spot Zeeman tuned slowing technique
[Phys. Rev. A 62, 013404-1, (2000)] to measure the capture velocity as a
function of laser intensity for a sodium magneto optical trap. Due to technical
limitation we explored only the low light intensity regime, from 0 to 27
mW/cm^2. Now we complement that work measuring the capture velocity in a
broader range of light intensities (from 0 to 400 mW/cm^2). New features,
observed in this range, are important to understant the escape velocity
behavior, which has been intensively used in the interpretation of cold
collisions. In particular, we show in this brief report that the capture
velocity has a maximum as function of the trap laser intensity, which would
imply a minimum in the trap loss rates.Comment: 2 pages, 2 figure
An algebraic Haag's theorem
Under natural conditions (such as split property and geometric modular action
of wedge algebras) it is shown that the unitary equivalence class of the net of
local (von Neumann) algebras in the vacuum sector associated to double cones
with bases on a fixed space-like hyperplane completely determines an algebraic
QFT model. More precisely, if for two models there is unitary connecting all of
these algebras, then --- without assuming that this unitary also connects their
respective vacuum states or spacetime symmetry representations --- it follows
that the two models are equivalent. This result might be viewed as an algebraic
version of the celebrated theorem of Rudolf Haag about problems regarding the
so-called "interaction-picture" in QFT.
Original motivation of the author for finding such an algebraic version came
from conformal chiral QFT. Both the chiral case as well as a related conjecture
about standard half-sided modular inclusions will be also discussed
The Biotechnology Cluster in Vancouver
There is a strong biotechnology cluster in Vancouver yet there is no major manufacturing facility. The Vancouver cluster is unlike other biotech clusters in that its output is solely intellectual property. This ongoing study not only examines the usual structure of a cluster, but also will focus on the issue of intellectual environment, and seek to determine whether a strong cluster can be built without the presence of a large, globally-competitive, manufacturer
Biomarkers of Tuberculosis Severity and Treatment Effect: A Directed Screen of 70 Host Markers in a Randomized Clinical Trial.
More efficacious treatment regimens are needed for tuberculosis, however, drug development is impeded by a lack of reliable biomarkers of disease severity and of treatment effect. We conducted a directed screen of host biomarkers in participants enrolled in a tuberculosis clinical trial to address this need. Serum samples from 319 protocol-correct, culture-confirmed pulmonary tuberculosis patients treated under direct observation as part of an international, phase 2 trial were screened for 70 markers of infection, inflammation, and metabolism. Biomarker assays were specifically developed for this study and quantified using a novel, multiplexed electrochemiluminescence assay. We evaluated the association of biomarkers with baseline characteristics, as well as with detailed microbiologic data, using Bonferroni-adjusted, linear regression models. Across numerous analyses, seven proteins, SAA1, PCT, IL-1β, IL-6, CRP, PTX-3 and MMP-8, showed recurring strong associations with markers of baseline disease severity, smear grade and cavitation; were strongly modulated by tuberculosis treatment; and had responses that were greater for patients who culture-converted at 8weeks. With treatment, all proteins decreased, except for osteocalcin, MCP-1 and MCP-4, which significantly increased. Several previously reported putative tuberculosis-associated biomarkers (HOMX1, neopterin, and cathelicidin) were not significantly associated with treatment response. In conclusion, across a geographically diverse and large population of tuberculosis patients enrolled in a clinical trial, several previously reported putative biomarkers were not significantly associated with treatment response, however, seven proteins had recurring strong associations with baseline radiographic and microbiologic measures of disease severity, as well as with early treatment response, deserving additional study
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