4,127 research outputs found
A simple functional form for proton-Pb total reaction cross sections
A simple functional form has been found that gives a good representation of
the total reaction cross sections for the scattering from Pb of
protons with energies in the range 30 to 300 MeV.Comment: 7 pages, 2 figure
Is friction responsible for the reduction of fusion rates far below the Coulomb barrier?
The fusion of two interacting heavy ions traditionally has been interpreted
in terms of the penetration of the projectile into the target. Observed rates
well below the Coulomb barrier are considerably lower than estimates obtained
from penetration factors. One approach in the analysis of the data invokes
coupling to non-elastic channels in the scattering as the source of the
depletion. Another is to analyze those data in terms of tunneling in
semi-classical models, with the observed depletion being taken as evidence of a
``friction'' under the barrier. A complementary approach is to consider such
tunneling in terms of a fully quantal model. We investigate tunneling with both
one-dimensional and three-dimensional models in a fully quantal approach to
investigate possible sources for such a friction. We find that the observed
phenomenon may not be explained by friction. However, we find that under
certain conditions tunneling may be enhanced or diminished by up to 50%, which
finds analogy with observation, without the invocation of a friction under the
barrier.Comment: 18 pages, 15 figures embedde
Modeling, Analysis, and Optimization Issues for Large Space Structures
Topics concerning the modeling, analysis, and optimization of large space structures are discussed including structure-control interaction, structural and structural dynamics modeling, thermal analysis, testing, and design
Comparison of optical model results from a microscopic Schr\"odinger approach to nucleon-nucleus elastic scattering with those from a global Dirac phenomenology
Comparisons are made between results of calculations for intermediate energy
nucleon-nucleus scattering for 12C, 16O, 40Ca, 90Zr, and 208Pb, using optical
potentials obtained from global Dirac phenomenology and from a microscopic
Schr\"odinger model. Differential cross sections and spin observables for
scattering from the set of five nuclei at 65 MeV and 200 MeV have been studied
to assess the relative merits of each approach. Total reaction cross sections
from proton-nucleus and total cross sections from neutron-nucleus scattering
have been evaluated and compared with data for those five targets in the energy
range 20 MeV to 800 MeV. The methods of analyses give results that compare well
with experimental data in those energy regimes for which the procedures are
suited.Comment: 22 pages, 12 figure
Nucleon-nucleus optical potential in the particle-hole approach
Feshbach's projection formalism in the particle-hole model space leads to a
microscopic description of scattering in terms of the many-body self-energy. To
investigate the feasibility of this approach, an optical potential for O-16 is
constructed starting from two previous calculations of the self-energy for this
nucleus. The results reproduce the background phase shifts for positive parity
waves and the resonances beyond the mean field.
The latter can be computed microscopically for energies of astrophysical
interest using Green's function theory.Comment: 8 pages, 6 figures. Submitted to Phys. Rev.
Anti-nociceptive and Anti-inflammatory Effects of the Methanol Extract of \u3cem\u3eAnnona senegalensis\u3c/em\u3e Root Bark
Objective: To investigate the antinociceptive and anti-inflammatory effect of Annona senegalensis in mice and rats. Materials and Methods: The analgesic effects of the methanolic extract were studied using acetic acid-induced writhing test, hot plate test and formalin test, while the anti-inflammatory effect was evaluated using the egg-albumin induced hind paw oedema in rats. Results: The methanolic extract exhibited antinociceptive activity against the acetic acid writhing test, hot plate test and the late phase of formaline induced nociception and significant anti-inflammatory activity. Conclusion: The analgesic and anti-inflammatory effect of the methanolic extract might be through peripheral mechanisms and thus justifying its folkloric use in the treatement of rheumatic pain
Predicting total reaction cross sections for nucleon-nucleus scattering
Nucleon total reaction and neutron total cross sections to 300 MeV for 12C
and 208Pb, and for 65 MeV spanning the mass range, are predicted using
coordinate space optical potentials formed by full folding of effective
nucleon-nucleon interactions with realistic nuclear ground state densities.
Good to excellent agreement is found with existing data.Comment: 10 pages, 4 figure
IRAS versus POTENT Density Fields on Large Scales: Biasing and Omega
The galaxy density field as extracted from the IRAS 1.2 Jy redshift survey is
compared to the mass density field as reconstructed by the POTENT method from
the Mark III catalog of peculiar velocities. The reconstruction is done with
Gaussian smoothing of radius 12 h^{-1}Mpc, and the comparison is carried out
within volumes of effective radii 31-46 h^{-1}Mpc, containing approximately
10-26 independent samples. Random and systematic errors are estimated from
multiple realizations of mock catalogs drawn from a simulation that mimics the
observed density field in the local universe. The relationship between the two
density fields is found to be consistent with gravitational instability theory
in the mildly nonlinear regime and a linear biasing relation between galaxies
and mass. We measure beta = Omega^{0.6}/b_I = 0.89 \pm 0.12 within a volume of
effective radius 40 h^{-1}Mpc, where b_I is the IRAS galaxy biasing parameter
at 12 h^{-1}Mpc. This result is only weakly dependent on the comparison volume,
suggesting that cosmic scatter is no greater than \pm 0.1. These data are thus
consistent with Omega=1 and b_I\approx 1. If b_I>0.75, as theoretical models of
biasing indicate, then Omega>0.33 at 95% confidence. A comparison with other
estimates of beta suggests scale-dependence in the biasing relation for IRAS
galaxies.Comment: 35 pages including 10 figures, AAS Latex, Submitted to The
Astrophysical Journa
- …