614 research outputs found
Does the shape of inflow velocity profiles affect hemodynamics in computational coronary artery models?
In this study, the impact of velocity inflow profiles shape on computational hemodynamic models of coronary arteries was investigated. To this purpose, 3D realistic velocity profiles were generated analytically and prescribed as inflow boundary condition and the impact on near-wall and intravascular flow was assessed. The results suggest that the impact of the shape of inflow velocity profiles on simulated coronary hemodynamics is limited to the proximal segment, while the global hemodynamics is poorly affected
Experimental evidence of antiproton reflection by a solid surface
We report here experimental evidence of the reflection of a large fraction of
a beam of low energy antiprotons by an aluminum wall. This derives from the
analysis of a set of annihilations of antiprotons that come to rest in rarefied
helium gas after hitting the end wall of the apparatus. A Monte Carlo
simulation of the antiproton path in aluminum indicates that the observed
reflection occurs primarily via a multiple Rutherford-style scattering on Al
nuclei, at least in the energy range 1-10 keV where the phenomenon is most
visible in the analyzed data. These results contradict the common belief
according to which the interactions between matter and antimatter are dominated
by the reciprocally destructive phenomenon of annihilation.Comment: 5 pages with 5 figure
Antiparticle cloud temperatures for antihydrogen experiments
An analysis of positron and antiproton cloud temperatures under condition similar to those found in antihydrogen experiments.Some simple general trends are brought out in the analysis, which includes the effects of cloud expansion for the first time
Limits on the low energy antinucleon-nucleus annihilations from the Heisenberg principle
We show that the quantum uncertainty principle puts some limits on the
effectiveness of the antinucleon-nucleus annihilation at very low energies.
This is caused by the fact that the realization a very effective short-distance
reaction process implies information on the relative distance of the reacting
particles. Some quantitative predictions are possible on this ground, including
the approximate A-independence of antinucleon-nucleus annihilation rates.Comment: 10 pages, no figure
Exploring novel arterio-venous graft designs to reduce vascular access failure risk
Although arterio-venous grafts (AVGs) are the second best option as permanent vascular access for hemodialysis, this solution is still affected by a relevant failure rate associated with neointimal hyperplasia (IH), mainly located at the venous anastomosis, where abnormal hemodynamics occurs. In this study we use computational fluid dynamics (CFD) to investigate the impact of six innovative AVG designs on reducing the IH risk at the distal anastomosis in AVGs. Findings from simulations clearly show that using a helical shaped flow divider located in the venous side of the graft could assure a reduced hemodynamic risk of failure at the distal anastomosis, with a clinically irrelevant increase in pressure drop over the graft
Coulomb corrections to low energy antiproton annihilation cross sections on protons and nuclei
We calculate, in a systematic way, the enhancement effect on
antiproton-proton and antiproton-nucleus annihilation cross sections at low
energy due to the initial state electrostatic interaction between the
projectile and the target nucleus. This calculation is aimed at future
comparisons between antineutron and antiproton annihilation rates on different
targets, for the extraction of pure isospin channels.Comment: 18 pages, 4 figures (latex format
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