Calibrating GESPECOR model of computing the full-energy peak efficiency of coaxial high-purity germanium detectors by Monte Carlo simulation.

In this work, a classical approach was used for calibrating the GESPECOR detector model for computing the full-energy peak efficiency of p-type coaxial HPGe detectors that is based on the use of linear least squares optimization. The key element of the work is the multiplicative model developed for approximating the values of the full-energy peak efficiency provided by GESPECOR code. It was linearized using the logarithmic transformation to allow an easy use of the linear least squares optimization. A procedure was also developed to estimate the optimal values of the parameters, describing the p-type coaxial HPGe detectors. Its application to a Canberra detector GC3018 showed that it is possible to determine accurate values of the full-energy peak efficiency computed by GESPECOR code using the optimized parameter values.

16+ spin-gap isomer in 96Cd.

A ß-decaying high-spin isomer in (96)Cd, with a half-life T(1/2)=0.29(-0.10)(+0.11) s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of (124)Xe on a (9)Be target. From the half-life and the observed γ decays in the daughter nucleus, (96)Ag, we conclude that the ß-decaying state is the long predicted 16(+) "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πν(p(1/2),g(9/2)) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N=Z=50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the πν(g,d,s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer.

Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes.

The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

Observation of isomeric decays in the r-process waiting-point nucleus 130Cd82.

The gamma decay of excited states in the waiting-point nucleus (130)Cd(82) has been observed for the first time. An 8(+) two-quasiparticle isomer has been populated both in the fragmentation of a (136)Xe beam as well as in projectile fission of 238U, making (130)Cd the most neutron-rich N = 82 isotone for which information about excited states is available. The results, interpreted using state-of-the-art nuclear shell-model calculations, show no evidence of an N = 82 shell quenching at Z = 48. They allow us to follow nuclear isomerism throughout a full major neutron shell from (98)Cd(50) to (130)Cd(82) and reveal, in comparison with (76)Ni(48) one major proton shell below, an apparently abnormal scaling of nuclear two-body interactions.

[Phacoemulsification and pseudoexfoliative syndrome]. / Facoemulsificarea în sindromul pseudoexfoliativ.

PURPOSE: To compare the results and the complications of cataract surgery by phacoemulsification in eyes with pseudoexfoliation syndrome (PEX) and without pseudoexfoliation syndrome. METHODS: A retrospective clinical study (January 2001 - January 2004; mean follow-up 21.5 months) of 116 cases divided in two groups: group A (55 eyes) with senile cataract and pseudoexfoliation syndrome and group B (61 eyes) with senile cataract but without pseudoexfoliation syndrome. The eyes were without another associated ophthalmological diseases and the phacoemulsifications were performed by the same surgeon. Intraoperative observations included anterior chamber depth, pupil size after maximal mydriasis, zonular dehiscence, capsule tear, vitreous loss and postoperatively: best corrected visual acuity, intraocular pressure (IOP), aqueous flare response and IOL stability were evaluated at 1 day, 1 week, 1 month and until 3 years. The Student-t test was used for statistical analyses. RESULTS: There were determined significant correlations between pupil size, anterior chamber depth and the rate of complications in the group A. The visual acuities were similar in both groups. IOP reduction was superior in the eyes with PEX as compared with control group, but without statistically significantly difference. In group A, there were a non-statistically significantly percentage of IOL dislocation as compared with group B. In the eyes with PEX, it is necessary to utilize IOLs with bigger optic size. CONCLUSIONS: Phacoemulsification represents a safe method in cataract surgery in eyes with pseudoexfoliation syndrome in the presence of careful surgical technique: maximal mydriasis, circular continuous curvilinear capsulorhexis, adequate hydrodissection. On the long run, the postoperative results were comparable between eyes with PEX and the control group (without PEX).