294 research outputs found
Indocyanine green elimination test in orthotopic liver recipients.
OBJECTIVE: To determine its predictive capability on graft quality and resultant clinical outcome, the indocyanine green (ICG) elimination test was performed by a spectrophotometric method and a noninvasive finger-piece method with 50 orthotopic liver transplantations. BACKGROUND: Early detection of poor-functioning hepatic grafts is one of the most important issues in liver transplantation, but no reliable methods exist. METHODS: The ICG test was performed after 50 orthotopic liver transplantations on postoperative days 1, 3, and 7. Indocyanine green elimination constants (K(ICG)) were measured by both a standard spectrophotometric analysis (K(ICG)-B) and by a finger-piece method (K(ICG)-F). The patients were followed for a minimum of 3 months after transplantation. Results of ICG tests were correlated with various clinical determinations. RESULTS: Twelve of the 50 grafts were lost within three months, of which 7 were related to graft failure. Multivariate analysis using the Cox proportional hazard model revealed that K(ICG) on postoperative day 1 was a better predictor of liver-related graft outcome than any of the conventional liver function tests. Furthermore, K(ICG) values showed significant correlation with the severity of preservation injury, longer intensive care unit (ICU) and hospital stay, prolonged liver dysfunction, and septic complications. Correlation of K(ICG) values by the spectrophotometric method with those by the finger-piece method was highly satisfactory in the grafts that had K(ICG)-B <0.15 min-1 (y = 0.868x -0.011, r = .955). CONCLUSION: The ICG elimination test, conducted spectrophotometrically or optically on the day after liver transplantation, is a reliable indicator of graft quality and subsequent graft outcome early after liver transplantation
Optical vernier technique for in-situ measurement of the length of long Fabry-Perot cavities
We propose a method for in-situ measurement of the length of kilometer size
Fabry-Perot cavities in laser gravitational wave detectors. The method is based
on the vernier, which occurs naturally when the laser incident on the cavity
has a sideband. By changing the length of the cavity over several wavelengths
we obtain a set of carrier resonances alternating with sideband resonances.
From the measurement of the separation between the carrier and a sideband
resonance we determine the length of the cavity. We apply the technique to the
measurement of the length of a Fabry-Perot cavity in the Caltech 40m
Interferometer and discuss the accuracy of the technique.Comment: LaTeX 2e, 12 pages, 4 figure
Data analysis of gravitational-wave signals from spinning neutron stars. II. Accuracy of estimation of parameters
We examine the accuracy of estimation of parameters of the gravitational-wave
signals from spinning neutron stars that can be achieved from observations by
Earth-based laser interferometers. We consider a model of the signal consisting
of two narrowband components and including both phase and amplitude modulation.
We calculate approximate values of the rms errors of the parameter estimators
using the Fisher information matrix. We carry out extensive Monte Carlo
simulations and obtain cumulative distribution functions of rms errors of
astrophysically interesting parameters: amplitude of the signal, wobble angle,
position of the source in the sky, frequency, and spindown coefficients. We
consider both all-sky searches and directed searches. We also examine the
possibility of determination of neutron star proper motion. We perform
simulations for all laser-interferometric detectors that are currently under
construction and for several possible lengths of the observation time and sizes
of the parameter space. We find that observations of continuous
gravitational-wave signals from neutron stars by laser-interferometric
detectors will provide a very accurate information about their astrophysical
properties. We derive several simplified models of the signal that can be used
in the theoretical investigations of the data analysis schemes independently of
the physical mechanisms generating the gravitational-wave signal.Comment: LaTeX, 34 pages, 15 figures, submitted to Phys. Rev.
Operational status of TAMA300 with the seismic attenuation system (SAS)
TAMA300 has been upgraded to improve the sensitivity at low frequencies after the last observation run in 2004. To avoid the noise caused by seismic activities, we installed a new seismic isolation system —- the TAMA seismic attenuation system (SAS). Four SAS towers for the test-mass mirrors were sequentially installed from 2005 to 2006. The recycled Fabry–Perot Michelson interferometer was successfully locked with the SAS. We confirmed the reduction of both length and angular fluctuations at frequencies higher than 1 Hz owing to the SAS
Optimal combination of signals from co-located gravitational wave interferometers for use in searches for a stochastic background
This article derives an optimal (i.e., unbiased, minimum variance) estimator
for the pseudo-detector strain for a pair of co-located gravitational wave
interferometers (such as the pair of LIGO interferometers at its Hanford
Observatory), allowing for possible instrumental correlations between the two
detectors. The technique is robust and does not involve any assumptions or
approximations regarding the relative strength of gravitational wave signals in
the detector pair with respect to other sources of correlated instrumental or
environmental noise. An expression is given for the effective power spectral
density of the combined noise in the pseudo-detector. This can then be
introduced into the standard optimal Wiener filter used to cross-correlate
detector data streams in order to obtain an optimal estimate of the stochastic
gravitational wave background. In addition, a dual to the optimal estimate of
strain is derived. This dual is constructed to contain no gravitational wave
signature and can thus be used as on "off-source" measurement to test
algorithms used in the "on-source" observation.Comment: 14 pages, 4 figures, submitted to Physical Review D Resubmitted after
editing paper in response to referee comments. Removed appendices A, B and
edited text accordingly. Improved legibility of figures. Corrected several
references. Corrected reference to science run number (S1 vs. S2) in text and
figure caption
No association between fruit or vegetable consumption and the risk of colorectal cancer in Japan
In a pooled analysis of two prospective studies with 88 658 Japanese men and women, fruit and vegetable consumptions, were not associated with a lower risk of colorectal cancer (705 cases); multivariate relative risk (95% confidence interval) for the highest vs the lowest quartile of intake being 0.92 (0.70–1.19) and 1.00 (0.79–1.27), respectively
Quantum statistical properties of the radiation field in a cavity with a movable mirror
A quantum system composed of a cavity radiation field interacting with a
movable mirror is considered and quantum statistical properties of the field
are studied. Such a system can serve in principle as an idealized meter for
detection of a weak classical force coupled to the mirror which is modelled by
a quantum harmonic oscillator. It is shown that the standard quantum limit on
the measurement of the mirror position arises naturally from the properties of
the system during its dynamical evolution. However, the force detection
sensitivity of the system falls short of the corresponding standard quantum
limit. We also study the effect of the nonlinear interaction between the moving
mirror and the radiation pressure on the quadrature fluctuations of the
initially coherent cavity field.Comment: REVTeX, 9 pages, 5 figures. More info on
http://www.ligo.caltech.edu/~cbrif/science.htm
Gravitational Waves from Chaotic Dynamical System
To investigate how chaos affects gravitational waves, we study the
gravitational waves from a spinning test particle moving around a Kerr black
hole, which is a typical chaotic system. To compare the result with those in
non-chaotic dynamical system, we also analyze a spinless test particle, which
orbit can be complicated in the Kerr back ground although the system is
integrable. We estimate the emitted gravitational waves by the multipole
expansion of a gravitational field. We find a striking difference in the energy
spectra of the gravitational waves. The spectrum for a chaotic orbit of a
spinning particle, contains various frequencies, while some characteristic
frequencies appear in the case of a spinless particle.Comment: 8 pages, 13 figures. submitted to PR
Coherent Bayesian inference on compact binary inspirals using a network of interferometric gravitational wave detectors
Presented in this paper is a Markov chain Monte Carlo (MCMC) routine for
conducting coherent parameter estimation for interferometric gravitational wave
observations of an inspiral of binary compact objects using data from multiple
detectors. The MCMC technique uses data from several interferometers and infers
all nine of the parameters (ignoring spin) associated with the binary system,
including the distance to the source, the masses, and the location on the sky.
The Metropolis-algorithm utilises advanced MCMC techniques, such as importance
resampling and parallel tempering. The data is compared with time-domain
inspiral templates that are 2.5 post-Newtonian (PN) in phase and 2.0 PN in
amplitude. Our routine could be implemented as part of an inspiral detection
pipeline for a world wide network of detectors. Examples are given for
simulated signals and data as seen by the LIGO and Virgo detectors operating at
their design sensitivity.Comment: 10 pages, 4 figure
Testing the performance of a blind burst statistic
In this work we estimate the performance of a method for the detection of
burst events in the data produced by interferometric gravitational wave
detectors. We compute the receiver operating characteristics in the specific
case of a simulated noise having the spectral density expected for Virgo, using
test signals taken from a library of possible waveforms emitted during the
collapse of the core of Type II Supernovae.Comment: 8 pages, 6 figures, Talk given at the GWDAW2002 worksho
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