9,955 research outputs found

    Neutron Skins and Halo Orbits in the sd and pf Shells

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    open3siThe strong dependence of Coulomb energies on nuclear radii makes it possible to extract the latter from calculations of the former. The resulting estimates of neutron skins indicate that two mechanisms are involved. The first one --isovector monopole polarizability—amounts to noting that when a particle is added to a system it drives the radii of neutrons and protons in different directions, tending to equalize the radii of both fluids independently of the neutron excess. This mechanism is well understood and the Duflo- Zuker (small) neutron skin values derived 14 years ago are consistent with recent measures and estimates. The alternative mechanism involves halo orbits whose huge sizes tend to make the neutron skins larger and have a subtle influence on the radial behavior of sd and f shell nuclei. In particular, they account for the sudden rise in the isotope shifts of nuclei beyond N=28 and the near constancy of radii in the A=40–56 region. This mechanism, detected here for the first time, is not well understood and may well go beyond the Efimov physics usually associated with halo orbits.openBonnard, JEREMY CHRISTIAN FREDERIC; Lenzi, SILVIA MONICA; Zuker, A. P.Bonnard, JEREMY CHRISTIAN FREDERIC; Lenzi, SILVIA MONICA; Zuker, A. P

    Nilsson-SU3 selfconsistency in heavy N=Z nuclei

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    It is argued that there exist natural shell model spaces optimally adapted to the operation of two variants of Elliott' SU3 symmetry that provide accurate predictions of quadrupole moments of deformed states. A selfconsistent Nilsson-like calculation describes the competition between the realistic quadrupole force and the central field, indicating a {\em remarkable stability of the quadruplole moments}---which remain close to their quasi and pseudo SU3 values---as the single particle splittings increase. A detailed study of the N=ZN=Z even nuclei from 56^{56}Ni to 96^{96}Cd reveals that the region of prolate deformation is bounded by a pair of transitional nuclei 72^{72}Kr and 84^{84}Mo in which prolate ground state bands are predicted to dominate, though coexisting with oblate ones,Comment: Replacement I) Title simplified. II) Major revision: structure of paper kept but two thirds totally rewritten (same number of pages); 20 references adde

    Coulomb displacement energies, energy differenced and neutron skins

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    A Fock space representation of the monopole part of the Coulomb potential is presented. Quantum effects show through a small orbital term in l(l+1)l(l+1). Once it is averaged out, the classical electrostatic energy emerges as an essentially exact expression, which makes it possible to eliminate the Nolen-Schiffer anomaly, and to estimate neutron skins and the evolution of radii along yrast states of mirror nuclei. The energy differences of the latter are quantitatively reproduced by the monopole term and a schematic multipole one.Comment: 4 pages, 3 figures, Revte

    On the dynamics of bubbles in boiling water

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    We investigate the dynamics of many interacting bubbles in boiling water by using a laser scattering experiment. Specifically, we analyze the temporal variations of a laser intensity signal which passed through a sample of boiling water. Our empirical results indicate that the return interval distribution of the laser signal does not follow an exponential distribution; contrariwise, a heavy-tailed distribution has been found. Additionally, we compare the experimental results with those obtained from a minimalist phenomenological model, finding a good agreement.Comment: Accepted for publication in Chaos, Solitons & Fractal

    Intravitreal injection of Ozurdex(®) implant in patients with persistent diabetic macular edema, with six-month follow-up

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    AIM: To evaluate the efficacy of intravitreal dexamethasone injections in diabetic macular edema (DME). METHODS: A 700 μg slow-release intravitreal dexamethasone implant (Ozurdex®) was placed in the vitreal cavity of 17 patients (19 eyes) affected with persistent DME. Best corrected visual acuity (BCVA) was assessed through Early Treatment Diabetic Retinopathy Study (ETDRS). Central macular thickness (CMT) was measured by spectral-domain optical coherence tomography. BCVA and CMT examinations were carried out at baseline (T0) and repeated after three days, one month (T1), three months (T3), four months (T4), and six months (T6) post injection. RESULTS: Dexamethasone implant induced an improvement in ETDRS at T1, T3, T4, and T6 post injection. CMT was reduced at T1, T3, and T4, while at T6, CMT values were not statistically different from baseline. No complications were observed during the follow-up. CONCLUSION: Our data suggest that dexamethasone implant is effective in reducing DME symptoms within a six-month frame
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