2,006 research outputs found
Faster than thought: Detecting sub-second activation sequences with sequential fMRI pattern analysis
Control system maintains selected liquid level
Single-sensor control system maintains liquid hydrogen at a preselected desired level within a tank, regardless of boiloff. It calibrates output in percentage. Thus, when the fuel is at the desired level, the system output will indicate 100 percent regardless of what percent of tank capacity the fuel has reached
Octupole deformation properties of the Barcelona-Catania-Paris energy density functionals
We discuss the octupole deformation properties of the recently proposed
Barcelona-Catania-Paris (BCP) energy density functionals for two sets of
isotopes, those of radium and barium, where it is believed that octupole
deformation plays a role in the description of the ground state. The analysis
is carried out in the mean field framework (Hartree- Fock- Bogoliubov
approximation) by using the axially symmetric octupole moment as a constraint.
The main ingredients entering the octupole collective Hamiltonian are evaluated
and the lowest lying octupole eigenstates are obtained. In this way we restore,
in an approximate way, the parity symmetry spontaneously broken by the mean
field and also incorporate octupole fluctuations around the ground state
solution. For each isotope the energy of the lowest lying state and the
and transition probabilities have been computed and compared to
both the experimental data and the results obtained in the same framework with
the Gogny D1S interaction, which are used here as a well established benchmark.
Finally, the octupolarity of the configurations involved in the way down to
fission of Pu, which is strongly connected to the asymmetric fragment
mass distribution, is studied. We confirm with this thorough study the
suitability of the BCP functionals to describe octupole related phenomena.Comment: 13 pages, 13 figure
Accurate nuclear masses from a three parameter Kohn-Sham DFT approach (BCPM)
Given the promising features of the recently proposed Barcelona-Catania-Paris
(BCP) functional \cite{Baldo.08}, it is the purpose of this paper to still
improve on it. It is, for instance, shown that the number of open parameters
can be reduced from 4-5 to 2-3, i.e. by practically a factor of two. One
parameter is tightly fixed by a fine-tuning of the bulk, a second by the
surface energy. The third is the strength of the spin-orbit potential on which
the final result does not depend within the scatter of the values used in
Skyrme and Gogny like functionals. An energy rms value of 1.58 MeV is obtained
from a fit of these three parameters to the 579 measured masses reported in the
Audi and Waspra 2003 compilation. This rms value compares favorably with the
one obtained using other successful mean field theories. Charge radii are also
well reproduced when compared with experiment. The energies of some excited
states, mostly the isoscalar giant monopole resonances, are studied within this
model as well.Comment: 23 pages, 12 figure
Medium polarization in asymmetric nuclear matter
The influence of the core polarization on the effective nuclear interaction
of asymmetric nuclear matter is calculated in the framework of the induced
interaction theory. The strong isospin dependence of the density and spin
density fluctuations is studied along with the interplay between the neutron
and proton core polarizations. Moving from symmetric nuclear matter to pure
neutron matter the crossover of the induced interaction from attractive to
repulsive in the spin singlet state is determined as a function of the isospin
imbalance.The density range in which it occurs is also determined. For the spin
triplet state the induced interaction turns out to be always repulsive. The
implications of the results for the neutron star superfluid phases are shortly
discussed.Comment: 6 pages, 4 figure
BEC-BCS Crossover and the Liquid-Gas Phase Transition in Hot and Dense Nuclear Matter
The effect of nucleon-nucleon correlations in symmetric nuclear matter at
finite temperature is studied beyond BCS theory. Starting from a Hartree-Fock
description of nuclear matter with the Gogny effective interaction, we add
correlations corresponding to the formation of preformed pairs and scattering
states above the superfluid critical temperature within the in-medium T-matrix
approach, which is analogous to the Nozieres-Schmitt-Rink theory. We calculate
the critical temperature for a BEC superfluid of deuterons, of a BCS superfluid
of nucleons, and in the crossover between these limits. The effect of the
correlations on thermodynamic properties (equation of state, energy, entropy)
and the liquid-gas phase transition is discussed. Our results show that
nucleon-nucleon correlations beyond BCS play an important role for the
properties of nuclear matter, especially in the low-density region.Comment: 11 pages, 12 figures; v2: minor modifications of the text, references
adde
IRRIGATION WATER RATE REFORM AND ENDOGENOUS TECHNOLOGICAL CHANGE
Research and Development/Tech Change/Emerging Technologies, Resource /Energy Economics and Policy,
Cooper pair sizes in superfluid nuclei in a simplified model
Cooper pair sizes are evaluated in a simple harmonic oscillator model
reproducing the values of sophisticated HFB calculations. Underlying reasons
for the very small sizes of 2.0-2.5 fm of Cooper pairs in the surface of nuclei
are analysed. It is shown that the confining properties of the nuclear volume
is the dominating effect. It is argued that for Cooper pair sizes LDA is
particularly inadapted.Comment: 8 pages, 6 figure
Critical Temperature for -Particle Condensation within a Momentum Projected Mean Field Approach
Alpha-particle (quartet) condensation in homogeneous spin-isospin symmetric
nuclear matter is investigated. The usual Thouless criterion for the critical
temperature is extended to the quartet case. The in-medium four-body problem is
strongly simplified by the use of a momentum projected mean field ansatz for
the quartet. The self-consistent single particle wave functions are shown and
discussed for various values of the density at the critical temperature
Generic strong coupling behavior of Cooper pairs in the surface of superfluid nuclei
With realistic HFB calculations, using the D1S Gogny force, we reveal a
generic behavior of concentration of small sized Cooper pairs (2-3 fm) in the
surface of superfluid nuclei. This study confirms and extends previous results
given in the literature that use more schematic approaches.Comment: 5 pages, 5 figure
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