Gamow-Teller GT+ distributions in nuclei with mass A=90-97

We investigate the Gamow-Teller strength distributions in the electron-capture direction in nuclei having mass A=90-97, assuming a 88Sr core and using a realistic interaction that reasonably reproduces nuclear spectroscopy for a wide range of nuclei in the region as well as experimental data on Gamow-Teller strength distributions. We discuss the systematics of the distributions and their centroids. We also predict the strength distributions for several nuclei involving stable isotopes that should be experimentally accessible for one-particle exchange reactions in the near future.Comment: 9 pages, 10 figures (from 17 eps files), to be submitted to Phys.Rev.C; corrected typos, minor language change

Search for the second forbidden beta decay of 8B to the ground state of 8Be

A significant decay branch of 8B to the ground state of 8Be would extend the solar neutrino spectrum to higher energies than anticipated in the standard solar models. These high-energy neutrinos would affect current neutrino oscillation results and also would be a background to measurements of the hep process. We have measured the delayed alpha particles from the decay of 8B, with the goal of observing the two 46-keV alpha particles arising from the ground-state decay. The 8B was produced using an in-flight radioactive beam technique. It was implanted in a silicon PIN-diode detector that was capable of identifying the alpha-particles from the 8Be ground state. From this measurement we find an upper limit (at 90% confidence level) of 7.3 x 10^{-5} for the branching ratio to the ground state. In addition to describing this measurement, we present a theoretical calculation for this branching ratio.Comment: One reference corrected. Minor edits in tex

A QTL for osteoporosis detected in an F2 population derived from White Leghorn chicken lines divergently selected for bone index

Osteoporosis, resulting from progressive loss of structural bone during the period of egg-laying in hens, is associated with an increased susceptibility to bone breakage. To study the genetic basis of bone strength, an F cross was produced from lines of hens that had been divergently selected for bone index from a commercial pedigreed White Leghorn population. Quantitative trait loci (QTL) affecting the bone index and component traits of the index (tibiotarsal and humeral strength and keel radiographic density) were mapped using phenotypic data from 372 F individuals in 32 F families. Genotypes for 136 microsatellite markers in 27 linkage groups covering ∼80% of the genome were analysed for association with phenotypes using within-family regression analyses. There was one significant QTL on chromosome 1 for bone index and the component traits of tibiotarsal and humeral breaking strength. Additive effects for tibiotarsal breaking strength represented 34% of the trait standard deviation and 7.6% of the phenotypic variance of the trait. These QTL for bone quality in poultry are directly relevant to commercial populations

Excess nitrogen leaching and C/N decline in the Tillingbourne catchment, southern England: INCA process modelling for current and historic time series

Measurements of nitrate deposition and streamwater chemistry in the Tillingbourne Catchment, in Southern England, made in 1979-1982 and 1999-2001 show a 216% increase in Nitrogen leaching despite a reduction in N inputs. Both the historical and current data sets have been modelled using the Integrated Nitrogen Model in Catchments (INCA). The process-based model is shown to reproduce the historical patterns of N release from the catchment. However, modelling the increased leaching of N during recent years required an increase of the mineralisation control parameter in the model, suggesting enhanced mineralisation rates. Comparing historic and current soils data for C/N ratios shows that there has been a reduction in C/N from 38 to 26% in the humus layer and a reduction from 33 to 26% in the mineral soil horizon. This significant fall in C/N is consistent with the increase in N saturation in the H and Ah horizons of the major catchment soil.</p> <p style='line-height: 20px;'><b>Keywords: </b>acid deposition, recovery, nitrogen, Carbon-Nitrogen ratios, Tillingbourne, Thames, catchment studies, nutrient leaching, modelling</p

Dynamical Spin Response Functions for Heisenberg Ladders

We present the results of a numerical study of the 2 by L spin 1/2 Heisenberg ladder. Ground state energies and the singlet-triplet energy gaps for L = (4-14) and equal rung and leg interaction strengths were obtained in a Lanczos calculation and checked against earlier calculations by Barnes et al. (even L up to 12). A related moments technique is then employed to evaluate the dynamical spin response for L=12 and a range of rung to leg interaction strength ratios (0 - 5). We comment on two issues, the need for reorthogonalization and the rate of convergence, that affect the numerical utility of the moments treatment of response functions.Comment: Revtex, 3 figure

Gamow-Teller transitions and deformation in the proton-neutron random phase approximation

We investigate reliability of Gamow-Teller transition strengths computed in the proton-neutron random phase approximation, comparing with exact results from diagonalization in full $0\hbar\omega$ shell-model spaces. By allowing the Hartree-Fock state to be deformed, we obtain good results for a wide variety of nuclides, even though we do not project onto good angular momentum. We suggest that deformation is as important or more so than pairing for Gamow-Teller transitions.Comment: 8 pages, 5 figures; added references, clarified discussion with regards to stabilit