1,905 research outputs found
Missing and Quenched Gamow Teller Strength
Gamow-Teller strength functions in full spaces are calculated with
sufficient accuracy to ensure that all the states in the resonance region have
been populated. Many of the resulting peaks are weak enough to become
unobservable. The quenching factor necessary to bring into agreement the low
lying observed states with shell model predictions is shown to be due to
nuclear correlations. To within experimental uncertainties it is the same that
is found in one particle transfer and (e,e') reactions. Perfect consistency
between the observed peaks and the calculation is
achieved by assuming an observation threshold of 0.75\% of the total strength,
a value that seems typical in several experimentsComment: 11 pages, 6 figures avalaible upon request, RevTeX, FTUAM-94/0
On the Strength of Spin-Isospin Transitions in A=28 Nuclei
The relations between the strengths of spin-isospin transition operators
extracted from direct nuclear reactions, magnetic scattering of electrons and
processes of semi-leptonic weak interactions are discussed.Comment: LaTeX, 8 pages, 1Postscript with figur
Spatially inhomogeneous condensate in asymmetric nuclear matter
We study the isospin singlet pairing in asymmetric nuclear matter with
nonzero total momentum of the condensate Cooper pairs. The quasiparticle
excitation spectrum is fourfold split compared to the usual BCS spectrum of the
symmetric, homogeneous matter. A twofold splitting of the spectrum into
separate branches is due to the finite momentum of the condensate, the isospin
asymmetry, or the finite quasiparticle lifetime. The coupling of the isospin
singlet and triplet paired states leads to further twofold splitting of each of
these branches. We solve the gap equation numerically in the isospin singlet
channel in the case where the pairing in the isospin triplet channel is
neglected and find nontrivial solutions with finite total momentum of the
pairs. The corresponding phase assumes a periodic spatial structure which
carries a isospin density wave at constant total number of particles. The phase
transition from the BCS to the inhomogeneous superconducting phase is found to
be first order and occurs when the density asymmetry is increased above 0.25.
The transition from the inhomogeneous superconducting to the unpaired normal
state is second order. The maximal values of the critical total momentum (in
units of the Fermi momentum) and the critical density asymmetry at which
condensate disappears are and . The possible
spatial forms of the ground state of the inhomogeneous superconducting phase
are briefly discussed.Comment: 13 pages, including 3 figues, uses RevTeX; minor corrections, PRC in
pres
Making justice more accessible
From the point of view of the Citizen, Justice is not always readily
accessible. Either because it is a lengthy process, potentially
expensive, sometimes unclear or simply scary, people will often
avoid or withdraw from a judicial process, especially in those
cases that involve relatively small amounts. This results in the
giving up of a basic right, with the potential loss of rightful
benefits. In this paper we briefly analyze the main aspects that
impair access to Justice nowadays. We then move on to look at
recent technological developments in the field of Online Dispute
Resolution to argue that these can, in the near future, have a
significant role in improving access to Justice. Specifically, we
analyze the UMCourt Conflict Resolution Framework, developed
by our research team, and address the different dimensions in
which such tools contribute to make Justice more accessible,
namely through better access to useful information, support in
decision-making or more cost-effective processes.Development Fund through the COMPETE Programme
(operational programme for competitiveness) and by National
Funds through the FCT - Fundação para a CiĂȘncia e a Tecnologia
(Portuguese Foundation for Science and Technology) within
projects FCOMP-01-0124-FEDER-028980 (PTDC/EEISII/1386/
2012) and PEst-OE/EEI/UI0752/201
Nuclear Shell Model Calculations of Neutralino-Nucleus Cross Sections for Silicon 29 and Germanium 73
We present the results of detailed nuclear shell model calculations of the
spin-dependent elastic cross section for neutralinos scattering from \si29 and
\ge73. The calculations were performed in large model spaces which adequately
describe the configuration mixing in these two nuclei. As tests of the computed
nuclear wave functions, we have calculated several nuclear observables and
compared them with the measured values and found good agreement. In the limit
of zero momentum transfer, we find scattering matrix elements in agreement with
previous estimates for \si29 but significantly different than previous work for
\ge73. A modest quenching, in accord with shell model studies of other heavy
nuclei, has been included to bring agreement between the measured and
calculated values of the magnetic moment for \ge73. Even with this quenching,
the calculated scattering rate is roughly a factor of 2 higher than the best
previous estimates; without quenching, the rate is a factor of 4 higher. This
implies a higher sensitivity for germanium dark matter detectors. We also
investigate the role of finite momentum transfer upon the scattering response
for both nuclei and find that this can significantly change the expected rates.
We close with a brief discussion of the effects of some of the non-nuclear
uncertainties upon the matrix elements.Comment: 31 pages, figures avaiable on request, UCRL-JC-11408
Nucleon-Nucleon Phase Shifts and Pairing in Neutron Matter and Nuclear Matter
We consider 1S0 pairing in infinite neutron matter and nuclear matter and
show that in the lowest order approximation, where the pairing interaction is
taken to be the bare nucleon-nucleon (NN) interaction in the 1S0 channel, the
pairing interaction and the energy gap can be determined directly from the 1S0
phase shifts. This is due to the almost separable character of the NN
interaction in this partial wave. Since the most recent NN interactions are
charge-dependent, we have to solve coupled gap equations for proton-proton,
neutron-neutron, and neutron-proton pairing in nuclear matter. The results,
however, are found to be close to those obtained with charge-independent
potentials.Comment: 5 pages, 3 figures, RevTe
Associations between social isolation, pro-social behaviour and emotional development in preschool aged children:a population based survey of kindergarten staff
Peer reviewedPublisher PD
Thermodynamics of - condensate in asymmetric nuclear matter
We study the neutron-proton pairing in nuclear matter as a function of
isospin asymmetry at finite temperatures and the saturation density using
realistic nuclear forces and Brueckner-renormalized single particle spectra.
Our computation of the thermodynamic quantities shows that while the difference
of the entropies of the superconducting and normal phases anomalously changes
its sign as a function of temperature for arbitrary asymmetry, the grand
canonical potential does not; the superconducting state is found to be stable
in the whole temperature-asymmetry plane. The pairing gap completely disappears
for density-asymmetries exceeding .Comment: 7 pages, including 3 figures, uses revte
Self-diffusion in binary blends of cyclic and linear polymers
A lattice model is used to estimate the self-diffusivity of entangled cyclic
and linear polymers in blends of varying compositions. To interpret simulation
results, we suggest a minimal model based on the physical idea that constraints
imposed on a cyclic polymer by infiltrating linear chains have to be released,
before it can diffuse beyond a radius of gyration. Both, the simulation, and
recently reported experimental data on entangled DNA solutions support the
simple model over a wide range of blend compositions, concentrations, and
molecular weights.Comment: 10 pages, 2 figure
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