4,772 research outputs found
Are spectroscopic factors from transfer reactions consistent with asymptotic normalisation coefficients?
It is extremely important to devise a reliable method to extract
spectroscopic factors from transfer cross sections. We analyse the standard
DWBA procedure and combine it with the asymptotic normalisation coefficient,
extracted from an independent data set. We find that the single particle
parameters used in the past generate inconsistent asymptotic normalization
coefficients. In order to obtain a consistent spectroscopic factor,
non-standard parameters for the single particle overlap functions can be used
but, as a consequence, often reduced spectroscopic strengths emerge. Different
choices of optical potentials and higher order effects in the reaction model
are also studied. Our test cases consist of: C(d,p)C(g.s.) at
MeV, O(d,p)O(g.s.) at MeV and
Ca(d,p)Ca(g.s.) at MeV. We underline the
importance of performing experiments specifically designed to extract ANCs for
these systems.Comment: 15 pages, 12 figures, Phys. Rev. C (in press
Jacobi-Nijenhuis algebroids and their modular classes
Jacobi-Nijenhuis algebroids are defined as a natural generalization of
Poisson-Nijenhuis algebroids, in the case where there exists a Nijenhuis
operator on a Jacobi algebroid which is compatible with it. We study modular
classes of Jacobi and Jacobi-Nijenhuis algebroids
Coulomb and nuclear breakup of B
The cross sections for the (B,Be-) breakup reaction on Ni
and Pb targets at the beam energies of 25.8 MeV and 415 MeV have been
calculated within a one-step prior-form distorted-wave Born approximation. The
relative contributions of Coulomb and nuclear breakup of dipole and quadrupole
multipolarities as well as their interference have been determined. The nuclear
breakup contributions are found to be substantial in the angular distributions
of the Be fragment for angles in the range of 30 - 80 at
25.8 MeV beam energy. The Coulomb-nuclear interference terms make the dipole
cross section larger than that of quadrupole even at this low beam energy.
However, at the incident energy of 415 MeV, these effects are almost negligible
in the angular distributions of the (Be-p) coincidence cross sections at
angles below 4.Comment: Revised version, accepted for publication in Phys. Rev.
Transfer/Breakup Modes in the 6He+209Bi Reaction Near and Below the Coulomb Barrier
Reaction products from the interaction of 6He with 209Bi have been measured
at energies near the Coulomb barrier. A 4He group of remarkable intensity,
which dominates the total reaction cross section, has been observed. The
angular distribution of the group suggests that it results primarily from a
direct nuclear process. It is likely that this transfer/breakup channel is the
doorway state that accounts for the previously observed large sub-barrier
fusion enhancement in this system.Comment: 4 pages; 3 figure
The role of the alloy structure in the magnetic behavior of granular systems
The effect of grain size, easy magnetization axis and anisotropy constant
distributions in the irreversible magnetic behavior of granular alloys is
considered. A simulated granular alloy is used to provide a realistic grain
structure for the Monte Carlo simulation of the ZFC-FC curves. The effect of
annealing and external field is also studied. The simulation curves are in good
agreement with the FC and ZFC magnetization curves measured on melt spun Cu-Co
ribbons.Comment: 13 pages, 10 figures, submitted to PR
Epidemiologia dos nematódeos gastrintestinais em bovinos de corte nos cerrados e o controle estratégico no Brasil.
Prevalência das espécies. OPG e imunidade adquirida. Larvas na pastagem. Hipobiose. Mortalidade de animais. Integração entre os helmintos do abomaso. Anorexia. Faixa etária, prejuízos e controle. Custo/Benefício.bitstream/item/104809/1/Epidemiologia-dos-nematoideos-gastrintestinais.pd
Montagem e operação de um sistema familiar de aquaponia para produção de peixes e hortaliças.
bitstream/item/144938/1/CT-72.pd
Direct reaction measurements with a 132Sn radioactive ion beam
The (d,p) neutron transfer and (d,d) elastic scattering reactions were
measured in inverse kinematics using a radioactive ion beam of 132Sn at 630
MeV. The elastic scattering data were taken in a region where Rutherford
scattering dominated the reaction, and nuclear effects account for less than 8%
of the cross section. The magnitude of the nuclear effects was found to be
independent of the optical potential used, allowing the transfer data to be
normalized in a reliable manner. The neutron-transfer reaction populated a
previously unmeasured state at 1363 keV, which is most likely the
single-particle 3p1/2 state expected above the N=82 shell closure. The data
were analyzed using finite range adiabatic wave calculations and the results
compared with the previous analysis using the distorted wave Born
approximation. Angular distributions for the ground and first excited states
are consistent with the previous tentative spin and parity assignments.
Spectroscopic factors extracted from the differential cross sections are
similar to those found for the one neutron states beyond the benchmark
doubly-magic nucleus 208Pb.Comment: 22 pages, 7 figure
Truncation of power law behavior in "scale-free" network models due to information filtering
We formulate a general model for the growth of scale-free networks under
filtering information conditions--that is, when the nodes can process
information about only a subset of the existing nodes in the network. We find
that the distribution of the number of incoming links to a node follows a
universal scaling form, i.e., that it decays as a power law with an exponential
truncation controlled not only by the system size but also by a feature not
previously considered, the subset of the network ``accessible'' to the node. We
test our model with empirical data for the World Wide Web and find agreement.Comment: LaTeX2e and RevTeX4, 4 pages, 4 figures. Accepted for publication in
Physical Review Letter
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