Chaos and Regularity in the Doubly Magic Nucleus

High-resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation energy of E_{x}=6.20 MeV in ^{208}Pb [Heusler et al., Phys. Rev. C 93, 054321 (2016)PRVCAN2469-998510.1103/PhysRevC.93.054321]. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach, we group states with the same spin and parity into 14 subspectra, analyze standard statistical measures for short- and long-range correlations, i.e., the nearest-neighbor spacing distribution, the number variance Σ^{2}, the Dyson-Mehta Δ_{3} statistics, and the novel distribution of the ratios of consecutive spacings of adjacent energy levels in each energy sequence, and then compute their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian orthogonal ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter [Phys. Rev. 120, 1698 (1960)PHRVAO0031-899X10.1103/PhysRev.120.1698], we consider the complete spectrum composed of the independent subspectra. We analyze their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f≈0.9. This is so far the closest agreement with a GOE observed in the spectra of bound states in a nucleus. The same analysis is also performed with spectra computed on the basis of shell model calculations with different interactions (surface-delta interaction, Kuo-Brown, Michigan-three-Yukawa). While the simple surface-delta interaction exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values.

Effective charge of the (pi)h(11/2) orbital and the electric field gradient of Hg from the Yrast structure of 206Hg.

The gamma-ray decay of excited states of the two-proton hole nucleus, 206Hg, has been identified using Gammasphere and 208Pb+238U collisions. The yrast states found include a T(1/2) = 92(8) ns 10(+) isomer located above the known 5(-) isomer. The B(E2;10(+)-->8(+)) strength is used to derive the quadrupole polarization charge induced by the h(11/2) proton hole. Also, the implied quadrupole moment has been used to provide an absolute scale for the electric field gradient of Hg in Hg metal.

ADCON-T/N reduces in vivo perineural adhesions in a rat sciatic nerve reoperation model.

Excessive perineural scarring may affect the result of peripheral nerve surgery. The ability of a novel implant material (ADCON-T/N) to prevent this complication was tested in 38 rats. Four weeks after a bilateral sciatic nerve external neurolysis, a secondary bilateral lysis of the adhesions was performed; ADCON-T/N was locally implanted at one side, while the contralateral side was left untreated. Four or 8 weeks later, perineural adhesions were dissected in 24 animals and graded blindly. Significantly fewer perineural adhesions were found in ADCON-T/N treated nerves compared with controls at both 4 and 8 weeks. Residual implant material or adverse effects were not observed at either time. Histological examination of the neurolysis sites in another 14 animals confirmed these findings at both time intervals. This study shows that ADCON-T/N is effective in inhibiting perineural adhesions, is resorbed within 4 weeks and is well tolerated.

A carbohydrate polymer that effectively prevents epidural fibrosis at laminectomy sites in the rat.

We demonstrate that a carbohydrate polymer, designated GL402, effectively inhibits epidural fibrosis in a rat laminectomy model. A total laminectomy in Lewis rats was performed at lumbar vertebrae 3 and 5. GL402 or phosphate buffer solutions in gelatin sponges were applied to the laminectomy sites. Epidural fibrosis was measured, using a double-blind protocol, 2 weeks postoperatively either by gross anatomical evaluation (blunt dissection) or by histological evaluation. Local application of GL402 produced nearly complete inhibition of epidural fibrosis, whereas extensive scar formation and bone growth occurred after local application of buffer or other purported anti-fibrotics. In laminectomy sites treated with GL402 the dura mater was essentially free of adhering fibrosis and bone growth was dramatically decreased. With reduction of postlaminectomy fibrosis, the spinal nerve roots are more mobile and therefore may be less prone to recurrent nerve root compression. The dramatic reduction of epidural fibrosis by GL402 will make reoperative disc surgery safer due to greater accessibility of the laminectomy site. This compound may be useful in preventing surgical adhesions in other sites as well.