7,397 research outputs found
The Giant Monopole Resonance in Pb isotopes
The extraction of the nuclear incompressibility from the isoscalar giant
monopole resonance (GMR) measurements is analysed. Both pairing and mutually
enhanced magicity (MEM) effects play a role in the shift of the GMR energy
between the doubly closed shell Pb nucleus and other Pb isotopes.
Pairing effects are microscopically predicted whereas the MEM effect is
phenomenologically evaluated. Accurate measurements of the GMR in open-shell Pb
isotopes are called for.Comment: 4 page
Symmetry energy from the nuclear collective motion: constraints from dipole, quadrupole, monopole and spin-dipole resonances
The experimental and theoretical studies of Giant Resonances, or more
generally of the nuclear collective vibrations, are a well established domain
in which sophisticated techniques have been introduced and firm conclusions
reached after an effort of several decades. From it, information on the nuclear
equation of state can be extracted, albeit not far from usual nuclear
densities. In this contribution, which complements other contributions
appearing in the current volume, we survey some of the constraints that have
been extracted recently concerning the parameters of the nuclear symmetry
energy. Isovector modes, in which neutrons and protons are in opposite phase,
are a natural source of information and we illustrate the values of symmetry
energy around saturation deduced from isovector dipole and isovector quadrupole
states. The isotopic dependence of the isoscalar monopole energy has also been
suggested to provide a connection to the symmetry energy: relevant theoretical
arguments and experimental results are thoroughly discussed. Finally, we
consider the case of the charge-exchange spin-dipole excitations in which the
sum rule associated with the total strength gives in principle access to the
neutron skin and thus, indirectly, to the symmetry energy.Comment: Updated version, with small corrections based on comments/suggestions
from the referee. 12 pages, 9 figures; submitted to EPJA "Special Issue on
Symmetry Energy
The asymmetry term in the nuclear-matter incompressibility from measurements on the giant monopole resonance: An Update
We have investigated the isoscalar giant monopole resonances (ISGMR) in
Sn and Cd nuclei using inelastic scattering of 386-MeV
-particles at extremely forward angles, including 0. The
strength distributions for various multipoles were extracted by a multipole
decomposition analysis based on the expected angular distributions of the
respective multipoles. From the ISGMR results, a value of
MeV is obtained for the asymmetry term in the nuclear incompressibility.Comment: Zakopane Conference on Nuclear Physics: Extremes of the Nuclear
Landscape, 45th Zakopane Schools of Physics, 30. August- 5. September 2010,
Zakopane, Polan
Where we stand on structure dependence of ISGMR in the Zr-Mo region: Implications on K_\infty
Isoscalar giant resonances, being the archetypal forms of collective nuclear
behavior, have been studied extensively for decades with the goal of
constraining bulk nuclear properties of the equation of state, as well as for
modeling dynamical behaviors within stellar environments. An important such
mode is the isoscalar electric giant monopole resonance (ISGMR) that can be
understood as a radially symmetric density vibration within the saturated
nuclear volume. The field has a few key open questions, which have been
proposed and remain unresolved. One of the more provocative questions is the
extra high-energy strength in the region, which manifested in
large percentages of the sum rule in Zr and Mo above the
main ISGMR peak. The purpose of this article is to introduce these questions
within the context of experimental investigations into the phenomena in the
zirconium and molybdenum isotopic chains, and to address, via a discussion of
previously published and preliminary results, the implications of recent
experimental efforts on extraction of the nuclear incompressibility from this
data.Comment: 9 pages, 7 figures, invited to be submitted to a special issue of
EPJA honoring Prof. P. F. Bortigno
Effect of pairing correlations on incompressibility and symmetry energy in nuclear matter and finite nuclei
The role of superfluidity in the incompressibility and in the symmetry energy
is studied in nuclear matter and finite nuclei. Several pairing interactions
are used: surface, mixed and isovector dependent. Pairing has a small effect on
the nuclear matter incompressibility at saturation density, but the effects are
significant at lower densities. The pairing effect on the centroid energy of
the isoscalar Giant Monopole Resonance (GMR) is also evaluated for Pb and Sn
isotopes by using a microscopic constrained-HFB approach, and found to change
at most by 10% the nucleus incompressibility . It is shown by using the
Local Density Approximation (LDA) that most of the pairing effect on the GMR
centroid come from the low-density nuclear surface.Comment: 9 pages, 6 figure
Early postnatal caloric restriction protects adult male intrauterine growth-restricted offspring from obesity.
Postnatal ad libitum caloric intake superimposed on intrauterine growth restriction (IUGR) is associated with adult-onset obesity, insulin resistance, and type 2 diabetes mellitus (T2DM). We hypothesized that this paradigm of prenatal nutrient deprivation-induced programming can be reversed with the introduction of early postnatal calorie restriction. Ten-month-old male rats exposed to either prenatal nutrient restriction with ad libitum postnatal intake (IUGR), pre- and postnatal nutrient restriction (IPGR), or postnatal nutrient restriction limited to the suckling phase (50% from postnatal [PN]1 to PN21) (PNGR) were compared with age-matched controls (CON). Visceral adiposity, metabolic profile, and insulin sensitivity by hyperinsulinemic-euglycemic clamps were examined. The 10-month-old male IUGR group had a 1.5- to 2.0-fold increase in subcutaneous and visceral fat (P < 0.0002) while remaining euglycemic, insulin sensitive, inactive, and exhibiting metabolic inflexibility (Vo(2)) versus CON. The IPGR group remained lean, euglycemic, insulin sensitive, and active while maintaining metabolic flexibility. The PNGR group was insulin sensitive, similar to IPGR, but less active while maintaining metabolic flexibility. We conclude that IUGR resulted in obesity without insulin resistance and energy metabolic perturbations prior to development of glucose intolerance and T2DM. Postnatal nutrient restriction superimposed on IUGR was protective, restoring metabolic normalcy to a lean and active phenotype
Achieving Good Angular Resolution in 3D Arc Diagrams
We study a three-dimensional analogue to the well-known graph visualization
approach known as arc diagrams. We provide several algorithms that achieve good
angular resolution for 3D arc diagrams, even for cases when the arcs must
project to a given 2D straight-line drawing of the input graph. Our methods
make use of various graph coloring algorithms, including an algorithm for a new
coloring problem, which we call localized edge coloring.Comment: 12 pages, 5 figures; to appear at the 21st International Symposium on
Graph Drawing (GD 2013
Macroscopic Quantum Coherence in a Magnetic Nanoparticle Above the Surface of a Superconductor
We study macroscopic quantum tunneling of the magnetic moment in a
single-domain particle placed above the surface of a superconductor. Such a
setup allows one to manipulate the height of the energy barrier, preserving the
degeneracy of the ground state. The tunneling amplitude and the effect of the
dissipation in the superconductor are computed.Comment: RevTeX, 4 pages, 1 figure. Submitted to Phys. Rev. Let
High-spin structure and Band Termination in Cd
Excited states of the neutron deficient Cd nucleus have been
investigated via the Ge(Cl, p3n) reaction at beam energy of 135
MeV by use of in-beam spectroscopic methods. Gamma rays depopulating the
excited states were detected using the Gammasphere spectrometer with high-fold
-ray coincidences. A quadrupole -ray coincidence analysis
() has been used to extend the known level scheme. The positive
parity levels have been established up to and
MeV. In addition to the observation of highly-fragmented level scheme belonging
to the positive-parity sequences at E 5 MeV, the termination of a
negative-parity sequence connected by transitions has been established at
and MeV. The experimental results
corresponding to both the positive- and negative-parity sequences have been
theoretically interpreted in the framework of the core particle coupling model.
Evidence is presented for a shape change from collective prolate to
non-collective oblate above the (8011 keV) level and for a
smooth termination of the negative-parity band.Comment: 19 pages, 8 figures. Submitted to Phys. Rev.
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