191 research outputs found
Passagem RetrĂłgrada PercutĂąnea De Uma LesĂŁo Estenosante CrĂtica Do Tronco CelĂaco Via ArtĂ©ria MesentĂ©rica Superior Como Manobra Adjuvante Na Abordagem AnterĂłgrada
We describe the case of a 63-year-old woman with chronic mesenteric ischemia, persistent postprandial upper abdominal pain and progressive weight loss. Retrograde recanalization was performed via the superior mesenteric artery in order to achieve the goal of crossing the near-occlusion, showing that retrograde catheterization of the celiac trunk can be a feasible approach in challenging cases in which an antegrade approach fails as a single maneuver. © 2016, Sociedade Brasileira de Angiologia e Cirurgia Vascular. All rights reserved.151616
Chiral Behaviour of the Rho Meson in Lattice QCD
In order to guide the extrapolation of the mass of the rho meson calculated
in lattice QCD with dynamical fermions, we study the contributions to its
self-energy which vary most rapidly as the quark mass approaches zero; from the
processes and . It turns out that in
analysing the most recent data from CP-PACS it is crucial to estimate the
self-energy from using the same grid of discrete momenta as
included implicitly in the lattice simulation. The correction associated with
the continuum, infinite volume limit can then be found by calculating the
corresponding integrals exactly. Our error analysis suggests that a factor of
10 improvement in statistics at the lowest quark mass for which data currently
exists would allow one to determine the physical rho mass to within 5%.
Finally, our analysis throws new light on a long-standing problem with the
J-parameter.Comment: 13 pages, 7 figures. Full analytic forms of the self-energies are
included and a correction in the omega-pi self-energ
Nonresonant Semileptonic Heavy Quark Decay
In both the large N_c limit and the valence quark model, semileptonic decays
are dominated by resonant final states. Using Bjorken's sum rule in an
"unquenched" version of the quark model, I demonstrate that in the heavy quark
limit nonresonant final states should also be produced at a significant rate.
By calculating the individual strengths of a large number of exclusive two-body
nonresonant channels, I show that the total rate for such processes is highly
fragmented. I also describe some very substantial duality-violating suppression
factors which reduce the inclusive nonresonant rate to a few percent of the
total semileptonic rate for the finite quark masses of B decay, and comment on
the importance of nonresonant decays as testing grounds for very basic ideas on
the structure, strength, and significance of the quark-antiquark sea and on
quark-hadron duality in QCD.Comment: 51 pages, 2 Postscript figure
Clones with finitely many relative R-classes
For each clone C on a set A there is an associated equivalence relation
analogous to Green's R-relation, which relates two operations on A iff each one
is a substitution instance of the other using operations from C. We study the
clones for which there are only finitely many relative R-classes.Comment: 41 pages; proofs improved, examples adde
The Generalized Liquid Drop Model Alpha-Decay Formula: Predictability Analysis and Super-Heavy Element Alpha Half-Lives
The predictive accuracy of the generalized liquid drop model (GLDM) formula
for alpha decay half-lives has been investigated in a detailed manner and a
variant of the formula with improved coefficients is proposed. The method
employs the experimental alpha half-lives of the well-known alpha standards
(REFERENCE) to obtain the coefficients of the analytical formula using the
experimental Qalpha values (the DSR-E formula), as well as the finite range
droplet model (FRDM) derived Qalpha values (the FRDMFRDM formula). The
predictive accuracy of these formulae were checked against the experimental
alpha half-lives of an independent set of nuclei (TEST) that span approximately
the same Z,A region as the standards and possess reliable alpha spectroscopic
data, and were found to yield good results for the DSR-E formula but not for
the FRDM-FRDM formula. The two formulae were used to obtain the alpha
half-lives of super-heavy (SHE) and heavy nuclides where the relative accuracy
was found to markedly improve for the FRDM-FRDM, which corroborates the
appropriateness of the FRDM masses and the GLDM prescription for high Z,A
nuclides. Further improvement resulted, especially for the FRDM-FRDM formula,
after a simple linear optimization over the calculated and experimental
half-lives of TEST was used to re-calculate the half-lives of the SHE and heavy
nuclides. The advantage of this optimization was that it required no
recalculation of the coefficients of the basic DSR-E or FRDM-FRDM formulae. The
halflives for 324 medium-mass to super-heavy alpha decaying nuclides,
calculated using these formulae and the comparison with experimental
half-lives, are presented.Comment: 61 pages, 6 figures, PDF file, to appear in Atomic Data and Nuclear
Data Table
Electromagnetic form factors of light vector mesons
The electromagnetic form factors G_E(q^2), G_M(q^2), and G_Q(q^2), charge
radii, magnetic and quadrupole moments, and decay widths of the light vector
mesons rho^+, K^{*+} and K^{*0} are calculated in a Lorentz-covariant,
Dyson-Schwinger equation based model using algebraic quark propagators that
incorporate confinement, asymptotic freedom, and dynamical chiral symmetry
breaking, and vector meson Bethe-Salpeter amplitudes closely related to the
pseudoscalar amplitudes obtained from phenomenological studies of pi and K
mesons. Calculated static properties of vector mesons include the charge radii
and magnetic moments: r_{rho+} = 0.61 fm, r_{K*+} = 0.54 fm, and r^2_{K*0} =
-0.048 fm^2; mu_{rho+} = 2.69, mu_{K*+} = 2.37, and mu_{K*0} = -0.40. The
calculated static limits of the rho-meson form factors are similar to those
obtained from light-front quantum mechanical calculations, but begin to differ
above q^2 = 1 GeV^2 due to the dynamical evolution of the quark propagators in
our approach.Comment: 8 pages of RevTeX, 5 eps figure
A Cross-Nations, Cross-Cultures, and Cross-Conditions Analysis on the Equivalence of the Balanced Inventory of Desirable Responding (BIDR)
Space-time evolution and HBT analysis of relativistic heavy ion collisions in a chiral SU(3) x SU(3) model
The space-time dynamics and pion-HBT radii in central heavy ion-collisions at
CERN-SPS and BNL-RHIC are investigated within a hydrodynamic simulation. The
dependence of the dynamics and the HBT-parameters on the EoS is studied with
different parametrisations of a chiral SU(3) sigma-omega model. The
selfconsistent collective expansion includes the effects of effective hadron
masses, generated by the nonstrange and strange scalar condensates. Different
chiral EoS show different types of phase transitions and even a crossover. The
influence of the order of the phase transition and of the difference in the
latent heat on the space-time dynamics and pion-HBT radii is studied. A small
latent heat, i.e. a weak first-order chiral phase transition, or even a smooth
crossover leads to distinctly different HBT predictions than a strong first
order phase transition. A quantitative description of the data, both at SPS
energies as well as at RHIC energies, appears difficult to achieve within the
ideal hydrodynamical approach using the SU(3) chiral EoS. A strong first-order
quasi-adiabatic chiral phase transition seems to be disfavored by the pion-HBT
data from CERN-SPS and BNL-RHIC
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