9,424 research outputs found
A New Approach in Risk Stratification by Coronary CT Angiography.
For a decade, coronary computed tomographic angiography (CCTA) has been used as a promising noninvasive modality for the assessment of coronary artery disease (CAD) as well as cardiovascular risks. CCTA can provide more information incorporating the presence, extent, and severity of CAD; coronary plaque burden; and characteristics that highly correlate with those on invasive coronary angiography. Moreover, recent techniques of CCTA allow assessing hemodynamic significance of CAD. CCTA may be potentially used as a substitute for other invasive or noninvasive modalities. This review summarizes risk stratification by anatomical and hemodynamic information of CAD, coronary plaque characteristics, and burden observed on CCTA
Boundary Dynamics of Sweeping Interface
A new type of boundary dynamics is proposed to describe the interface that
sweeps space to collect distributed material. Based upon geometrical
consideration on a simple physical process representing a certain experiment,
the dynamics is formulated as the small diffusion limit of Mullins-Sekerka
problem of crystal growth. It is demonstrated that a steadily extending finger
solution exists for a finite range of propagation speed, but numerical
simulations suggest they are unstable and the interface shows a complex time
development.Comment: 4 pages, 4 figure
Characters in Conformal Field Theories from Thermodynamic Bethe Ansatz
We propose a new -series formula for a character of parafermion conformal
field theories associated to arbitrary non-twisted affine Lie algebra
. We show its natural origin from a thermodynamic Bethe ansatz
analysis including chemical potentials.Comment: 12 pages, harvmac, 1 postscript figure file, (some confusion on PF
Hilbert space was modified) HUTP-92/A06
Preliminary measurements of plasma fluctuations in an 8-cm mercury ion thruster
The rms magnitude, spectra, and cross correlations for the fluctuations in the beam current, the neutralizer keeper current, and the discharge current and voltage were measured for an 8-cm diameter, dished grid ion thruster for a beam current of 72 milliamps. The ratio of the rms magnitude of the fluctuations to the time-mean neutralizer keeper current was found to depend significantly on the neutralizer time-mean keeper current, the flow rate, and keeper hold diameter. The maxima of the spectra of the beam current fluctuations did not depend on the discharge fluctuations. It was found that: (1) the discharge current fluctuations do not directly contribute to the beam current fluctuations; and (2) the neutralizer contributions to the beam fluctuations are small (for good neutralizer-to-beam coupling) but not negligible and appear mostly in the higher frequency range measured
Diffusion and spectral dimension on Eden tree
We calculate the eigenspectrum of random walks on the Eden tree in two and
three dimensions. From this, we calculate the spectral dimension and the
walk dimension and test the scaling relation (
for an Eden tree). Finite-size induced crossovers are observed, whereby the
system crosses over from a short-time regime where this relation is violated
(particularly in two dimensions) to a long-time regime where the behavior
appears to be complicated and dependent on dimension even qualitatively.Comment: 11 pages, Plain TeX with J-Phys.sty style, HLRZ 93/9
The Virgo High-Resolution CO Survey. II. Rotation Curves and Dynamical Mass Distributions
Based on a high-resolution CO survey of Virgo spirals with the Nobeyama
Millimeter-wave Array, we determined the dynamical centers using velocity
fields, and derived position-velocity diagrams (PVDs) along the major axes of
the galaxies across their dynamical centers. We applied a new iteration method
to derive rotation curves (RCs), which reproduce the observed PVDs. The
obtained high-accuracy RCs generally show steep rise in the central 100 to 200
pc regions, followed by flat rotation in the disk. We applied a deconvolution
method to calculate the surface-mass density (SMD) using the RCs based on two
extreme assumptions that the mass distribution is either spherical or thin-disk
shaped. Both assumptions give nearly identical results, agreeing with each
other within a factor of two at any radii. The SMD distributions revealed
central massive cores with peak SMD of 10^4 - 10^5 Msun pc^-2 and total mass
within 200 pc radius of the order of about 10^9 Msun Correlation analysis among
the derived parameters show that the central CO-line intensity is positively
correlated with the central SMD, which suggests that the deeper is the
gravitational potential, the higher is the molecular gas concentration in the
nuclei regardless morphological types.Comment: PASJ 2003 in press, Latex 12 pages, 6 figures (Bigger gif/ps figures
available at http://www.ioa.s.u-tokyo.ac.jp/radio/virgo2
Bethe-Salpeter equation: 3D reductions, heavy mass limits and abnormal solutions
We show that the 3D reductions of the Bethe-Salpeter equation have the same
bound state spectrum as the original equation, with the possible exception of
some solutions for which the corresponding 3D wave function vanishes. The
abnormal solutions of the Bethe-Salpeter equation (corresponding to excitations
in the relative time-energy degree of freedom), when they exist, are recovered
in the 3D reductions via a complicated dependence of the final potential on the
total energy. We know however that the one-body (or one high mass) limit of
some 3D reductions of the exact Bethe-Salpeter equation leads to a compact 3D
equation (by a mutual cancellation of the ladder and crossed graph
contributions), which does not exhibit this kind of dependence on the total
energy anymore. We conclude that the exact Bethe-Salpeter equation has no
abnormal solution at this limit, or has only solutions for which our 3D wave
function vanishes. This is in contrast with the results of the ladder
approximation, where no such cancellation occurs. We draw the same conclusions
for the static model, which we obtain by letting the mass of the lighter
particle go also to infinity. These results support Wick's conjecture that the
abnormal solutions are a spurious consequence of the ladder approximation.Comment: 11 pages Latex, 1 figure Postscript. Submitted to Journal of Physics
The Dog on the Ship: The "Canis Major Dwarf Galaxy" as an Outlying Part of the Argo Star System
Overdensities in the distribution of low latitude, 2MASS giant stars are
revealed by systematically peeling away from sky maps the bulk of the giant
stars conforming to ``isotropic'' density laws generally accounting for known
Milky Way components. This procedure, combined with a higher resolution
treatment of the sky density of both giants and dust allows us to probe to
lower Galactic latitudes than previous 2MASS giant star studies. While the
results show the swath of excess giants previously associated with the
Monoceros ring system in the second and third Galactic quadrants at distances
of 6-20 kpc, we also find a several times larger overdensity of giants in the
same distance range concentrated in the direction of the ancient constellation
Argo. Isodensity contours of the large structure suggest that it is highly
elongated and inclined by about 3 deg to the disk, although details of the
structure -- including the actual location of highest density, overall extent,
true shape -- and its origin, remain unknown because only a fraction of it lies
outside highly dust-obscured, low latitude regions. Nevertheless, our results
suggest that the 2MASS M giant overdensity previously claimed to represent the
core of a dwarf galaxy in Canis Major (l ~ 240 deg) is an artifact of a dust
extinction window opening to the overall density rise to the more significant
Argo structure centered at larger longitude (l ~ 290 +- 10 deg, b ~ -4 +- 2
deg).Comment: 4 pages, 4 figure
Geometry of fully coordinated, two-dimensional percolation
We study the geometry of the critical clusters in fully coordinated
percolation on the square lattice. By Monte Carlo simulations (static
exponents) and normal mode analysis (dynamic exponents), we find that this
problem is in the same universality class with ordinary percolation statically
but not so dynamically. We show that there are large differences in the number
and distribution of the interior sites between the two problems which may
account for the different dynamic nature.Comment: ReVTeX, 5 pages, 6 figure
- …