Statistical gamma-ray decay studies at iThemba LABS

Abstract. A program to study the γ -ray decay from the region of high-level density has been established at iThemba LABS, where a high-resolution gamma-ray detector array is used in conjunction with silicon particle-telescopes. Results from two recent projects are presented: 1) The 74Ge(α, α γ ) reaction was used to investigate the Pygmy Dipole Resonance. The results were compared to (γ,γ ) data and indicate that the dipole states split into mixed isospin and relatively pure isovector excitations. 2) Data from the 95Mo(d,p) reaction were used to develop a novel method for the determination of spins for low-lying discrete levels utilizing statistical γ -ray decay in the vicinity of the neutron separation energy. These results provide insight into the competition of (γ ,n) and (γ,γ ) reactions and highlights the need to correct for angular momentum barrier effect

Copy Number Variation Affecting the Photoperiod-B1 and Vernalization-A1 Genes Is Associated with Altered Flowering Time in Wheat (Triticum aestivum)

The timing of flowering during the year is an important adaptive character affecting reproductive success in plants and is critical to crop yield. Flowering time has been extensively manipulated in crops such as wheat (Triticum aestivum L.) during domestication, and this enables them to grow productively in a wide range of environments. Several major genes controlling flowering time have been identified in wheat with mutant alleles having sequence changes such as insertions, deletions or point mutations. We investigated genetic variants in commercial varieties of wheat that regulate flowering by altering photoperiod response (Ppd-B1 alleles) or vernalization requirement (Vrn-A1 alleles) and for which no candidate mutation was found within the gene sequence. Genetic and genomic approaches showed that in both cases alleles conferring altered flowering time had an increased copy number of the gene and altered gene expression. Alleles with an increased copy number of Ppd-B1 confer an early flowering day neutral phenotype and have arisen independently at least twice. Plants with an increased copy number of Vrn-A1 have an increased requirement for vernalization so that longer periods of cold are required to potentiate flowering. The results suggest that copy number variation (CNV) plays a significant role in wheat adaptation

Conservation agriculture and livelihoods of smallholder farmers in Central Mozambique

This article demonstrates how conservation agriculture impacts smallholder farmers' livelihoods in Mozambique through increased crop productivity and yields, using primary data on smallholder farmers practicing conservation agriculture and others not using this technology from Nhanguo, Pumbuto, and Ruaca in Manica and Sofala provinces. Data analysis employs semiparametric propensity score matching methods. Direct correlations between conservation agriculture, higher productivity and yields; and indirect correlations with changes in household incomes and food security are suggested. Conclusively, systematic targeting of conservation agriculture to different farmer categories, can improve livelihoods, household incomes and food security. We recommend integration of conservation agriculture into the rural development policy framework in Mozambique

Use of Human Excreta as Manure in Rural China

Empirical research has shown that the use of manure significantly improves crop yield, soil fertility and water and moisture conservation. Despite these documented benefits, however, there is a concern on the downward trend of manure use in agriculture in China. This paper examines factors contributing to this downward trend, with a particular focus on human excreta used in agriculture. Empirical analysis based on data from stratified random sampling of rural households in five provinces of China shows that about 85% of human excreta was still used as manure in agriculture in 2007 which was less than a decade ago when nearly all human excreta was used as manure. Econometric results suggest that income growth, rising population density and improvement in rural transportation significantly contribute to declining use of human excreta as manure in agriculture. These results imply that the current downward trend will continue given China's rising economic growth, urbanization and rural infrastructural improvement

How connected are Chinese farmers to retail markets? New evidence of price transmission

This paper examines the extent to which Chinese farmers are connected to regional agricultural markets by looking at the intensity of price transmission from retail markets to the farmgate. This intensity is indicative of the extent to which farmers might benefit from improved marketing opportunities and be exposed to price risks. We estimate the elasticity of farmgate prices to retail prices using price data for 170 markets, in 29 out of 33 provinces of China, at the detail of 12 main products and for the five-year period 1996 to 2000. In each province we find strong linkages between retail and farmgate prices with elasticities ranging between 0.6 and 1 and intensifying over time. This suggests that Chinese farmers are generally well connected to retail markets and that this connectivity has strengthened in the period considered, creating not only new opportunities but also new risks. It is also found that linkages are relatively weak in inland provinces, which is a point of concern in view of Chinese policies to create equal opportunities and equitable growth. © 2011 Elsevier Inc

Electron spectrometer for electric monopole (E0) transition studies in nuclei

The study of electric monopole (E0) transitions between two 0+ states is important because the monopole strength carries vital information about the nuclear structure due to its direct link with the mean squared charge radius r2 and quadrupole deformation parameter β. Therefore, the measurement of internal conversion electrons (ICE) or internal pair formation (IPF) is crucial for E0 transition studies. Transitions between 0+ states do not change angular momentum. Hence, single-photon emission is forbidden, but can decay by conversion electrons or pair formation and two-photon emission which is mostly negligible. In order to implement E0 studies at iThemba LABS, an electron spectrometer that uses a solenoidal magnetic field acting as a lens and a Si(Li) detector has been refurbished and characterized using calibration sources of ICE. Figures of merit have been extracted and compared with simulations. The spectrometer coupled with an array of LaBr3:Ce detectors and Low Energy Photon Spectrometers (LEPS) was successfully implemented for in-beam experiments. Measurements of internal conversion coefficients (ICC) and monopole strengths extracted from in-beam measurements of 72As, 72Ge, and 72Se are presented