The Effect of Different Magnetospheric Structures on Predictions of Gamma-ray Pulsar Light Curves

The second pulsar catalogue of the Fermi Large Area Telescope (LAT) will contain in excess of 100 gamma-ray pulsars. The light curves (LCs) of these pulsars exhibit a variety of shapes, and also different relative phase lags with respect to their radio pulses, hinting at distinct underlying emission properties (e.g., inclination and observer angles) for the individual pulsars. Detailed geometric modelling of the radio and gamma-ray LCs may provide constraints on the B-field structure and emission geometry. We used different B-field solutions, including the static vacuum dipole and the retarded vacuum dipole, in conjunction with an existing geometric modelling code, and constructed radiation sky maps and LCs for several different pulsar parameters. Standard emission geometries were assumed, namely the two-pole caustic (TPC) and outer gap (OG) models. The sky maps and LCs of the various B-field and radiation model combinations were compared to study their effect on the resulting LCs. As an application, we compared our model LCs with Fermi LAT data for the Vela pulsar, and inferred the most probable configuration in this case, thereby constraining Vela's high-altitude magnetic structure and system geometry.Comment: 6 pages, 4 figures, conference article, appears in Proceedings of SAIP2012, the 57th Annual Conference of the South African Institute of Physics, edited by Johan Janse van Rensburg, ISBN: 978-1-77592-070-

Towards ensuring scalability, interoperability and efficient access control in a multi-domain grid-based environment

The application of grid computing has been hampered by three basic challenges: scalability, interoperability and efficient access control which need to be optimized before a full-scale adoption of grid computing can take place. To address these challenges, a novel architectural model was designed for a multi-domain grid based environment (built on three domains). It was modelled using the dynamic role-based access control. The architecture’s framework assumes that each domain has an independent local security monitoring unit and a central security monitoring unit that monitors security for the entire grid. The architecture was evaluated using the Grid Security Services Simulator, a meta-query language and Java Runtime Environment 1.7.0.5 for implementing the workflows that define the model’s task. In terms of scalability, the results show that as the number of grid nodes increases, the average turnaround time reduces, and thereby increases the number of service requesters (grid users) on the grid. Grid middleware integration across various domains as well as the appropriate handling of authentication and authorisation through a local security monitoring unit and a central security monitoring unit proved that the architecture is interoperable. Finally, a case study scenario used for access control across the domains shows the efficiency of the role based access control approach used for achieving appropriate access to resources. Based on the results obtained, the proposed framework has proved to be interoperable, scalable and efficiently suitable for enforcing access control within the parameters evaluated.Department of HE and Training approved lis

Measuring micronutrient intakes at different levels of sugar consumption in a population in transition: the Transition and Health during Urbanisation in South Africa (THUSA) study

Objective: The objective was to investigate the absolute micronutrient intake and the possibility of micronutrient dilution of added sugar in thediets of an African population in nutritional transition.Design: A cross-sectional, comparative, population-based design was used. Respondents who consumed sugar were divided into four quartiles of percentage of added sugar intake.Setting: The setting was 37 randomly selected rural and urban areas of the North West province.Subjects: The subjects were 1 742 adult volunteers (739 men and 1 003 women), aged between 15-65 years. After exclusion of low-energyreporters, the sample comprised 1 045 subjects (472 men and 573 women).Outcome measures: The outcomes measures were the macronutrient and micronutrient intakes of subjects in different quartiles of addedsugar intake and body mass index (BMI).Results: The average intake of added sugar was 10.01% of total energy (67.12 g) in men and 11.2% total energy (67.10 g) in women.Respondents who consumed the most added sugar had significantly lower mean intakes of alcohol, but higher intakes of energy, macronutrientsand most micronutrients. The diets of those in the highest sugar intake group contained significantly less thiamine, riboflavin, niacin, vitaminB12, pantothenic acid, biotin, magnesium, phosphorus and zinc per 4.18 MJ. At every level of added sugar consumption, the mean intakesof fibre (men only), folate, ascorbic acid and calcium (men and women) did not meet the dietary reference intakes [estimated averagerequirements (EAR)] and pantothenic acid and biotin (women only) did not meet the adequate intake. There were no significant differencesin mean BMI across the quartiles of added sugar intakes in men, but the mean BMI of women who consumed the most added sugar wassignificantly higher than that of those who consumed less sugar. Respondents who consumed the most added sugar had significantly higherintakes of fruit (men only), bread and soft drinks, and lower intakes of maize meal and alcohol (men and women).Conclusion: Absolute intakes of most micronutrients were significantly higher in consumers with a high sugar intake [Quartile (Q) 4] comparedwith the lowest consumers of sugar (Q1). The lowest percentages of participants whose micronutrient intakes fell below the EAR were in Q4and Q3. However, expression of micronutrient intake per 4.18 kJ (micronutrient dilution) revealed significantly less of most micronutrients per 4.18 MJ for men and women who consumed the most added sugar, compared with those who consumed the least

Molecular analysis of fruit ripening: The identification of differentially expressed sequences in Vitis vinifera using cDNA-AFLP technology

Differential gene expression patterns were studied during the ripening process of grape berries (Vitis vinifera cv. Chardonnay). Thirty PstI + MseI primer combinations were used to generate 213 fragments that appeared to be differentially expressed of which 94 % were successfully re-amplified. Reverse northern dot-blot analysis indicated that 35 % of the fragments had similar gene expression profiles to cDNA-AFLPs regarding developmental-stage specificity. Northern blot analyses confirmed the tissue and/or developmental stage specific expression of three of these cDNA fragments. This work illustrates that developmentally regulated sequences can be identified from grape berry tissue using cDNA-AFLP technology