2,328 research outputs found
Correlation of mechanical factors and gallbladder pain
Acalculous biliary pain occurs in patients with no gallstones, but is similar to that experienced by patients with gallstones. Surgical removal of the gallbladder (GB) in these patients is only successful in providing relief of symptoms to about half of those operated on, so a reliable pain-prediction model is needed. In this paper, a mechanical model is developed for the human biliary system during the emptying phase, based on a clinical test in which GB volume changes are measured in response to a standard stimulus and a recorded pain profile. The model can describe the bile emptying behaviour, the flow resistance in the biliary ducts, the peak total stress, including the passive and active stresses experienced by the GB during emptying. This model is used to explore the potential link between GB pain and mechanical factors. It is found that the peak total normal stress may be used as an effective pain indicator for GB pain. When this model is applied to clinical data of volume changes due to Cholecystokinin stimulation and pain from 37 patients, it shows a promising success rate of 88.2% in positive pain prediction
Relativistic many-body calculations of electric-dipole matrix elements, lifetimes and polarizabilities in rubidium
Electric-dipole matrix elements for ns-n'p, nd-n'p, and 6d-4f transitions in
Rb are calculated using a relativistic all-order method. A third-order
calculation is also carried out for these matrix elements to evaluate the
importance of the high-order many-body perturbation theory contributions. The
all-order matrix elements are used to evaluate lifetimes of ns and np levels
with n=6, 7, 8 and nd levels with n=4, 5, 6 for comparison with experiment and
to provide benchmark values for these lifetimes. The dynamic polarizabilities
are calculated for ns states of rubidium. The resulting lifetime and
polarizability values are compared with available theory and experiment.Comment: 8 pages, 2 figure
The effect of two-temperature post-shock accretion flow on the linear polarization pulse in magnetic cataclysmic variables
The temperatures of electrons and ions in the post-shock accretion region of
a magnetic cataclysmic variable (mCV) will be equal at sufficiently high mass
flow rates or for sufficiently weak magnetic fields. At lower mass flow rates
or in stronger magnetic fields, efficient cyclotron cooling will cool the
electrons faster than the electrons can cool the ions and a two-temperature
flow will result. Here we investigate the differences in polarized radiation
expected from mCV post-shock accretion columns modeled with one- and
two-temperature hydrodynamics. In an mCV model with one accretion region, a
magnetic field >~30 MG and a specific mass flow rate of ~0.5 g/cm/cm/s, along
with a relatively generic geometric orientation of the system, we find that in
the ultraviolet either a single linear polarization pulse per binary orbit or
two pulses per binary orbit can be expected, depending on the accretion column
hydrodynamic structure (one- or two-temperature) modeled. Under conditions
where the physical flow is two-temperature, one pulse per orbit is predicted
from a single accretion region where a one-temperature model predicts two
pulses. The intensity light curves show similar pulse behavior but there is
very little difference between the circular polarization predictions of one-
and two-temperature models. Such discrepancies indicate that it is important to
model some aspect of two-temperature flow in indirect imaging procedures, like
Stokes imaging, especially at the edges of extended accretion regions, were the
specific mass flow is low, and especially for ultraviolet data.Comment: Accepted for publication in Astrophysics & Space Scienc
Chiral And Parity Anomalies At Finite Temperature And Density
Two closely related topological phenomena are studied at finite density and
temperature. These are chiral anomaly and Chern-Simons term. By using different
methods it is shown that is the crucial point for Chern-Simons at
zero temperature. So when --influence disappears and we get
the usual Chern-Simons term. On the other hand when the
Chern-Simons term vanishes because of non-zero density of background fermions.
It is occurs that the chiral anomaly doesn't depend on density and temperature.
The connection between parity anomalous Chern-Simons and chiral anomaly is
generalized on finite density. These results hold in any dimension as in
abelian, so as in nonabelian cases
D-branes in 2d Lorentzian black hole
We study D-branes in the Lorentzian signature 2D black hole string theory. We
use the technique of gauged WZW models to construct the associated boundary
conformal field theories. The main focus of this work is to discuss the
(semi-classical) world-volume geometries of the D-branes. We also discuss
comparison of our work with results in related gauged WZW models.Comment: 24 pages, 5 figures, uses JHEP3.cl
Non-perturbative gauge superpotentials from supergravity
We study U(N) SQCD with N_f <= N flavors of quarks and antiquarks by
engineering it with a configuration of fractional D3-branes on a C^3 / Z_2 x
Z_2 orbifold. In particular we show how the moduli space of the gauge theory
naturally emerges from the classical geometry produced by the D3-branes, and
how the non-perturbatively generated superpotential is recovered from
geometrical data.Comment: LaTeX, 18 pages, 4 figures; v2: published version with minor changes
and an added referenc
Fractional Exclusion Statistics and Anyons
Do anyons, dynamically realized by the field theoretic Chern-Simons
construction, obey fractional exclusion statistics? We find that they do if the
statistical interaction between anyons and anti-anyons is taken into account.
For this anyon model, we show perturbatively that the exchange statistical
parameter of anyons is equal to the exclusion statistical parameter. We obtain
the same result by applying the relation between the exclusion statistical
parameter and the second virial coefficient in the non-relativistic limit.Comment: 9 pages, latex, IFT-498-UN
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