2,784 research outputs found
The characteristics of the spectra of superior venae cavae in patients with right heart failure
BACKGROUND: Aimed to elucidate the characteristics of the spectra of superior venae cavae (SVC) in respiratory cycles in patients with right heart failure. METHODS: The spectra of SVC of 30 patients with right heart failure and 30 paired healthy subjects were recorded through right supraclavicular fossa view. The profiles of spectra of superior venae cavae were observed, and peak velocity and velocity time integral (VTI) of every wave of SVC under spontaneous respiration were measured for statistical analysis. RESULTS: In healthy subjects, the peak velocities and VTI of S wave and D wave increased in inspiratory phase and diminished in expiratory phase, and which of S wave were larger than which of D wave in whole respiratory cycle. In patients with right heart failure, spectral variations of SVC could be classified into three patterns: Pattern I: peak velocities and VTI of S wave were larger than that of D wave in early inspiratory phase, but peak velocities and VTI of D wave were larger than those of S wave in late inspiratory phase and early expiratory phase [Pattern I-1], even in whole respiratory cycle [Pattern I-2]; Pattern II: the S wave disappeared and was substituted by inverse wave with low amplitude in whole respiratory cycle. Pattern III: the profiles of the spectra of SVC in patients were similar to those of healthy subjects. In the whole, the respiratory variation ratios of peak velocities and VTI of S wave and D wave were diminished in patients compared with those in healthy subjects. CONCLUSION: The spectra of superior venae cavae in patients with right heart failure were abnormal, and these characteristics could be used as signs in evaluating right heart failure
ROSAT/ASCA Observations of a Serendipitous BL Lac Object PKS 2316-423: The Variable High-Energy Tail of Synchrotron Radiation
We present the analysis of archival data from ROSAT and ASCA of a
serendipitous BL Lac object PKS 2316-423. Because of its featureless
non-thermal radio/optical continuum, PKS 2316-423 has been called as a BL Lac
candidate in the literature. PKS 2316-423 was evidently variable over the
multiple X-ray observations, in particular, a variable high-energy tail of the
synchrotron radiation is revealed. The X-ray spectral analysis provides further
evidence of the synchrotron nature of its broad-band spectrum: a steep and
downward curving spectrum between 0.1--10 keV, typical of high-energy peaked BL
Lacs (HBL). The spectral energy distribution (SED) through radio-to-X-ray
yields the synchrotron radiation peak at frequency Vp=7.3 10^{15} Hz, with
integrated luminosity of Lsyn=2.1 10^{44} ergs s^{-1}. The averaged SED
properties of PKS 2316-423 are very similar to those ``intermediate'' BL Lac
objects (IBL) found recently in several deep surveys, such as Deep X-ray Radio
Blazar, Radio-Emitting X-ray, and ROSAT-Green Bank surveys. We suggest that PKS
2316-423 is an IBL though it also shows some general features of a HBL.
Actually, this double attribute of PKS 2316-423 provides a good test of the
prediction that an IBL object can show either synchrotron or inverse-Compton
characteristics in different variability states.Comment: 12 pages, including 4 figures, to appear in ApJ, 2000 July 2
Final State Interactions in
It is believed that the production rate of is almost
solely determined by final state interactions (FSI) and hence provides an ideal
place to test FSI models. Here we examine model calculations of the
contributions from s-channel resonance and t-channel exchange to
the FSI effects in . The contribution from s-channel
is sma The results from
two methods are roughly consistent with each other and can reproduce the large
rate of reasonably well$Comment: Latex, 16 pages, with 2 figure
An interpretation for the entropy of a black hole
We investigate the meaning of the entropy carried away by Hawking radiations
from a black hole. We propose that the entropy for a black hole measures the
uncertainty of the information about the black hole forming matter's
precollapsed configurations, self-collapsed configurations, and inter-collapsed
configurations. We find that gravitational wave or gravitational radiation
alone cannot carry all information about the processes of black hole
coalescence and collapse, while the total information locked in the hole could
be carried away completely by Hawking radiation as tunneling
Pseudoscalar Higgs boson production associated with a single bottom quark at hadron colliders
We compute the complete next-to-leading order (NLO) SUSY-QCD corrections for
the associated production of a pseudoscalar Higgs boson with a bottom quark via
bottom-gluon fusion at the CERN Large Hadron Collider (LHC) and the Fermilab
Tevatron. We find that the NLO QCD correction in the MSSM reaches
at the LHC and at the Tevatron in our chosen parameter space
Next-to-leading order QCD predictions for production at LHC
We calculate the complete next-to-leading order (NLO) QCD corrections to the
production in association with a jet at the LHC. We study the impacts
of the NLO QCD radiative corrections to the integrated and differential cross
sections and the dependence of the cross section on the
factorization/renormalization scale. We present the transverse momentum
distributions of the final -, Higgs-boson and leading-jet. We find that
the NLO QCD corrections significantly modify the physical observables, and
obviously reduce the scale uncertainty of the LO cross section. The QCD
K-factors can be 1.183 and 1.180 at the and
LHC respectively, when we adopt the inclusive event selection scheme with
, and . Furthermore, we make the comparison between the two scale
choices, and , and find the scale choice seems to be more
appropriate than the fixed scale .Comment: 18 pages, 7 figure
Comparison of tricuspid inflow and superior vena caval Doppler velocities in acute simulated hypovolemia: new non-invasive indices for evaluating right ventricular preload
BACKGROUND: Assessment of cardiac preload is important for clinical management of some emergencies related to hypovolemia. Effects of acute simulated hypovolemia on Doppler blood flow velocity indices of tricuspid valve (TV) and superior vena cava (SVC) were investigated in order to find sensitive Doppler indices for predicting right ventricular preload. METHODS: Doppler flow patterns of SVC and TV in 12 healthy young men were examined by transthoracic echocardiography (TTE) during graded lower body negative pressure (LBNP) of up to -60 mm Hg which simulated acute hypovolemia. Peak velocities of all waves and their related ratios (SVC S/D and tricuspid E/A) were measured, calculated and statistically analyzed. RESULTS: Except for the velocity of tricuspid A wave, velocities of all waves and their related ratios declined during volume decentralization. Of all indices measured, the peak velocities of S wave and AR wave in SVC correlated most strongly with levels of LBNP (r = -0.744 and -0.771, p < 0.001). CONCLUSION: The S and AR velocities are of good values in assessing right ventricular preload. Monitoring SVC flow may provide a relatively noninvasive means to assess direct changes in right ventricular preload
A simulation study on the measurement of D0-D0bar mixing parameter y at BES-III
We established a method on measuring the \dzdzb mixing parameter for
BESIII experiment at the BEPCII collider. In this method, the doubly
tagged events, with one decays to
CP-eigenstates and the other decays semileptonically, are used to
reconstruct the signals. Since this analysis requires good separation,
a likelihood approach, which combines the , time of flight and the
electromagnetic shower detectors information, is used for particle
identification. We estimate the sensitivity of the measurement of to be
0.007 based on a fully simulated MC sample.Comment: 6 pages, 7 figure
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