Stroke in the young

CITATION: De Villiers, R. V. P., February, E. & De Villiers, M. L. 2003. Stroke in the young. South African Medical Journal, 93(11):836-837.The original publication is available at http://www.samj.org.za[No abstract available]Publisher’s versio

The adjoint mehod for automotive optimisation using a sphericity based morpher

A robust workflow for shape optimisation of internal and external flows with application to automotive design is demonstrated in this paper. A gradient based approach is presented, in which the surface sensitivity with respect to the flow variables is computed with the continuous adjoint method. For aerodynamic shape optimisation cases, mesh displacement algorithms are indispensable in order to avoid re-meshing the updated geometry in each optimisation step. Keeping the same mesh topology at every optimisation cycle secures gradient consistency and the possibility to use the previous solution as initial conditions in order to converge the CFD equations faster. Simple mesh displacement algorithms, such as the spring analogy, run into problems under complex surface deformations. Thus a mesh optimisation approach can be proved to be more robust as it copes better with complex elements optimising also the base mesh. In this paper the mesh displacement algorithm is based on sphericity, which quantifies the mesh quality. Solving an extra optimisation problem for the maximisation of the sphericity value, results in the new internal mesh nodes positions. The methodology is heuristic in nature in that it does not consider known numerical quality metrics explicitly. It has shown however to be exceptionally robust and effective allowing the maintenance of high cell quality even during extreme deformation events. The suggested method is applied to automotive test cases of internal and external aerodynamics. In such cases, the use of a robust morpher which preserves geometry features and delays mesh quality deterioration is found to be crucial

Scattering of Straight Cosmic Strings by Black Holes: Weak Field Approximation

The scattering of a straight, infinitely long string moving with velocity $v$ by a black hole is considered. We analyze the weak-field case, where the impact parameter ($b_{imp}$) is large, and obtain exact solutions to the equations of motion. As a result of scattering, the string is displaced in the direction perpendicular to the velocity by an amount $\Delta b\sim -2\pi GMv\gamma/c^3 -\pi (GM)^2/ (4c^3 v b_{imp})$, where $\gamma=(1-(v/c)^2)^{-1/2}$. The second term dominates at low velocities $v/c<(GM/b_{imp})^{1/2}$ . The late-time solution is represented by a kink and anti-kink, propagating in opposite directions at the speed of light, and leaving behind them the string in a new ``phase''. The solutions are applied to the problem of string capture, and are compared to numerical results.Comment: 19 pages, 5 figure

Increase in childhood asthma admissions in an urbanising population

Objective. In South Africa, rapid urbanisation has increased the risk of childhood asthma. This report reviews the pattern of asthma admissions to the Paediatric Department of Ga-Rankuwa Hospital, South Africa, from 1986 to 1996. Design. Inpatient admission data were reviewed for 1986- 1996. A detailed analysis of the records of asthma patients admitted between 1992 and 1996 was done. Outpatient data were reviewed from 1992.Setting. Ga-Rankuwa Hospital, situated on the border of the Gauteng and orth West provinces of South Africa and serving a large black population in various stages of urbanisation.Main outcome measures. Trends in admission numbers and demographic characteristics.Results. Asthma admissions were 2.5 times higher in 1996 than 1986. The greatest increase in admissions was in the 1 - 47-month age group. The male to female ratio was 1.5:1. More patients came from urban than from rural areas. Admissions peaked during the summer. Re-admissions occurred most frequently within 3 months of the first admission.Conclusion. Paediatric asthma admissions have shown an increase in the past decade. This may be associated with changes in the environment of the community. There is a need for preventive programmes for asthma at community and national level

GENDER INDEPENDENT DISCRIMINATIVE SPEAKER RECOGNITION IN I–VECTOR SPACE

Speaker recognition systems attain their best accuracy when trained with gender dependent features and tested with known gender trials. In real applications, however, gender labels are often not given. In this work we illustrate the design of a system that does not make use of the gender labels both in training and in test, i.e. a completely Gender Independent (GI) system. It relies on discriminative training, where the trials are i–vector pairs, and the discrimination is between the hypothesis that the pair of feature vectors in the trial belong to the same speaker or to different speakers. We demonstrate that this pairwise discriminative training can be interpreted as a procedure that estimates the parameters of the best (second order) approximation of the log–likelihood ratio score function, and that a pairwise SVM can be used for training a gender independent system. Our results show that a pairwise GI SVM, saving memory and execution time, achieves on the last NIST evaluations state–of–the–art performance, comparable to a Gender Dependent(GD) system

Reissner-Nordstrom Black Holes and Thick Domain Walls

We solve numerically equations of motion for real self-interacting scalar fields in the background of Reissner-Nordstrom black hole and obtained a sequence of static axisymmetric solutions representing thick domain walls charged black hole systems. In the case of extremal Reissner-Nordstrom black hole solution we find that there is a parameter depending on the black hole mass and the width of the domain wall which constitutes the upper limit for the expulsion to occur.Comment: 18 pages, 10 figures, accepted for Phys. Rev.

Conductance of the single-electron transistor: A comparison of experimental data with Monte Carlo calculations

We report on experimental results for the conductance of metallic single-electron transistors as a function of temperature, gate voltage and dimensionless conductance. In contrast to previous experiments our transistor layout allows for a direct measurement of the parallel conductance and no ad hoc assumptions on the symmetry of the transistors are necessary. Thus we can make a comparison between our data and theoretical predictions without any adjustable parameter. Even for rather weakly conducting transistors significant deviations from the perturbative results are noted. On the other hand, path integral Monte Carlo calculations show remarkable agreement with experiments for the whole range of temperatures and conductances.Comment: 8 pages, 7 figures, revtex4, corrected typos, submitted to PR

Cohort profile: biological pathways of risk and resilience in Syrian refugee children (BIOPATH)

The BIOPATH cohort was established to explore the interplay of psychosocial and biological factors in the development of resilience and mental health problems in Syrian refugee children. Based in Lebanon, a middle-income country significantly impacted by the refugee crisis, it is the first such cohort of refugees in the Middle East. Families were recruited from informal tented settlements in the Beqaa region using purposive cluster sampling. At baseline (October 2017–January 2018), N = 3188 individuals participated [n = 1594 child–caregiver dyads; child gender, 52.6% female; mean (SD) age = 11.44 (2.44) years, range = 6–19]. Re-participation rate at 1-year follow-up was 62.8%. Individual interviews were conducted with children and primary caregivers and biological samples collected from children. Measures include: (1) children’s well-being and mental health problems (using tools validated against clinical interviews in a subsample of the cohort); (2) psychosocial risk and protective factors at the level of the individual (e.g. coping strategies), family (e.g. parent–child relationship), community (e.g. collective efficacy), and wider context (e.g. services); (3) saliva samples for genetic and epigenetic (methylation) analyses; (4) hair samples to measure cortisol, dehydroepiandrosterone (DHEA) and testosterone. This cohort profile provides details about sampling and recruitment, data collection and measures, demographic data, attrition and potential bias, key findings on resilience and mental health problems in children and strengths and limitations of the cohort. Researchers interested in accessing data should contact Professor Michael Pluess at Queen Mary University of London, UK (e-mail: [email protected]). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00127-022-02228-8