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  • Author: J. R. Lee x
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Official Journal of the World Association of Perinatal Medicine

Abstract

Eighty six full-sib Corymbia F1 hybrid families (crosses between C. torelliana and four spotted gum taxa: C. citriodora subsp. variegata, C. citriodora subsp. citriodora, C. henryi and C. maculata), were planted in six trials across six disparate sites in south-eastern Queensland to evaluate their productivity and determine their potential utility for plantation forestry. In each trial, the best-growing 20% of hybrid families grew significantly faster (P = 0.05) than open-pollinated seedlots of the parent species Corymbia citriodora subsp. variegata, ranging from 107% to 181% and 127% to 287% of the height and diameter respectively. Relative performance of hybrid families growing on more than one site displayed consistency in ranking for growth across sites and analysis showed low genotype-by-environment interaction. Heritability estimates based on female and male parents across two sites at age six years for height and diameter at breast height, were high (0.62 ± 0.28 to 0.64 ± 0.35 and 0.31 ± 0.21 to 0.69 ± 0.37 respectively), and low to moderate (0.03 ± 0.04 to 0.33 ± 0.22) for stem straightness, branch size, incidence of ramicorns, and frost and disease resistance traits at ages one to three years. The proportion of dominance variance for height and diameter had reduced to zero by age six years. Based on these promising results, further breeding and pilot-scale family forestry and clonal forestry deployment is being undertaken. These results have also provided insights regarding the choice of a future hybrid breeding strategy.

The oxidation state of iron (Fe) in the crystal structure of smectite clay minerals profoundly alters their physical-chemical properties. Among the properties affected are layer charge, cation exchange and fixation capacity, swelling in water, particle size, specific surface area, layer stacking order, magnetic exchange interactions, octahedral site occupancy, surface acidity, and reduction potential. Also affected is the surface chemistry of the clay, which alters clay–water and clay–organic interaction mechanisms. Rates and extents of degradation of pesticides are increased in the presence of reduced smectites compared to oxidized and reduced-reoxidized counterparts. A hypothesis regarding the mechanism for Fe reduction in clay minerals was first developed in 1963, and subsequent modifications have been proposed periodically through the present time. Recent studies clearly reveal that the process of Fe reduction involves more than the mere transfer of an electron to octahedral Fe(III) in the clay crystal. Ancillary reactions occur that produce significant structural modifications, some of which are reversible and others of which are not. Such changes in the crystal-chemical environment of structural Fe are thought to play a dominant role in altering the clay surface chemistry.

Abstract

A Li ion from a 10B(n,α γ) 7Li reaction induced by a thermal neutron undergoes a large degradation due to its high stopping power in a medium. This phenomenon influences the peak line shape of the 477.6 keV gamma line emitted from an excited 7Li nucleus recoiled by an energetic alpha particle and the peak line shape in a spectrum varies according to the slowing-down media. A numerical study for the analysis of the line shape has been conducted by performing a parametric search and fitting the measured spectrum in a least squares approach by Choi et al. and implemented in a recent version of HYPERGAM code. In this study, the gamma-ray spectra were measured for various media like elemental boron, boric acid, borax, boron carbide, boron steel and so on at a SNU-KAERI prompt gamma activation analysis facility of the HANARO research reactor in Korea Atomic Energy Research Institute. The degradation constant was determined for various slowing-down media.