1,620 research outputs found
Property management strategies for institutional investors in the '90s
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1996.Includes bibliographical references (leaves 91-92).by John A. Willand.M.S
Exact Baryon, Strangeness and Charge Conservation in Hadronic Gas Models
Relativistic heavy ion collisions are studied assuming that particles can be
described by a hadron gas in thermal and chemical equilibrium. The exact
conservation of baryon number, strangeness and charge are explicitly taken into
account. For heavy ions the effect arising from the neutron surplus becomes
important and leads to a substantial increase in e.g. the ratio.
A method is developed which is very well suited for the study of small systems.Comment: 5 pages, 5 Postscript figure
HQET chromomagnetic interaction at two loops
We present the coefficient of the chromomagnetic interaction operator, the
only unknown coefficient in the Heavy Quark Effective Theory (HQET) lagrangian
up to the level, with the two-loop accuracy by matching scattering
amplitudes of an on-shell heavy quark in an external field in full QCD and
HQET, and obtain the two-loop anomalous dimension of this operator in HQET.Comment: 10 pages, LaTeX2e, 2 eps figures included. Revised discussion of
(n_f-1)-flavour HQET include
First upper limit analysis and results from LIGO science data: stochastic background
I describe analysis of correlations in the outputs of the three LIGO
interferometers from LIGO's first science run, held over 17 days in August and
September of 2002, and the resulting upper limit set on a stochastic background
of gravitational waves. By searching for cross-correlations between the LIGO
detectors in Livingston, LA and Hanford, WA, we are able to set a 90%
confidence level upper limit of h_{100}^2 Omega_0 < 23 +/- 4.6.Comment: 7 pages; 1 eps figures; proceeding from 2003 Edoardo Amaldi Meeting
on Gravitational Wave
On the Relation between Solar Activity and Clear-Sky Terrestrial Irradiance
The Mauna Loa Observatory record of direct-beam solar irradiance measurements
for the years 1958-2010 is analysed to investigate the variation of clear-sky
terrestrial insolation with solar activity over more than four solar cycles.
The raw irradiance data exhibit a marked seasonal cycle, extended periods of
lower irradiance due to emissions of volcanic aerosols, and a long-term
decrease in atmospheric transmission independent of solar activity. After
correcting for these effects, it is found that clear-sky terrestrial irradiance
typically varies by about 0.2 +/- 0.1% over the course of the solar cycle, a
change of the same order of magnitude as the variations of the total solar
irradiance above the atmosphere. An investigation of changes in the clear-sky
atmospheric transmission fails to find a significant trend with sunspot number.
Hence there is no evidence for a yet unknown effect amplifying variations of
clear-sky irradiance with solar activity.Comment: 16 pages, 7 figures, in press at Solar Physics; minor changes to the
text to match final published versio
The Reliability of Red Flags in Spinal Cord Compression
Background: Acute low back pain is a common cause for presentation to the emergency department (ED). Since benign etiologies account for 95% of cases, red flags are used to identify sinister causes that require prompt management.
Objectives: We assessed the effectiveness of red flag signs used in the ED to identify spinal cord and cauda equine compression.
Patients and Methods: It was a retrospective cohort study of 206 patients with acute back pain admitted from the ED. The presence or absence of the red flag symptoms was assessed against evidence of spinal cord or cauda equina compression on magnetic resonance imaging (MRI).
Results: Overall, 32 (15.5%) patients had compression on MRI. Profound lower limb neurologic examination did not demonstrate a statistically significant association with this finding. The likelihood ratio (LR) for bowel and bladder dysfunction (sensitivity of 0.65 and specificity of 0.73) was 2.45. Saddle sensory disturbance (sensitivity of 0.27 and specificity of 0.87) had a LR of 2.11. When both symptoms were taken together (sensitivity of 0.27 and specificity of 0.92), they gave a LR of 3.46.
Conclusions: The predictive value of the two statistically significant red flags only marginally raises the clinical suspicion of spinal cord or cauda equina compression. Effective risk stratification of patients presenting to the ED with acute back pain is crucial; however, this study did not support the use of these red flags in their current form
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