Maximum heat transfer rate density from a rotating multiscale array of cylinders

This work investigated a numerical approach to the search of a maximum heat transfer rate density (the overall heat transfer dissipated per unit of volume) from a two-dimensional laminar multiscale array of cylinders in cross-flow under an applied fixed pressure drop and subject to the constraint of fixed volume. It was furthermore assumed that the flow field was steady state and incompressible. The configuration had two degrees of freedom in the stationary state, that is, the spacing between the cylinders and the diameter of the smaller cylinders. The angular velocity of the cylinders was in the range 0 ≤ ϖ, ≤ 0.1. Two cylinders of different diameters were used, in the first case, the cylinders were aligned along a plane which lay on their centrelines. In the second case, the cylinder leading edge was aligned along the plane that received the incoming fluid at the same time. The diameter of the smaller cylinder was fixed at the optimal diameter obtained when the cylinders were stationary. Tests were conducted for co-rotating and counterrotating cylinders. The results were also compared with results obtained in the open literature and the trend was found to be the same. Results showed that the heat transfer from a rotating array of cylinders was enhanced in certain cases and this was observed for both directions of rotation from an array which was aligned on the centreline. For rotating cylinders with the same leading edge, there is heat transfer suppression and hence the effect of rotation on the maximum heat transfer rate density is insignificant. This research is important in further understanding of heat transfer from rotating cylinders, which can be applied to applications ranging from contact cylinder dryers in the chemical processes industry and rotating cylinder electrodes to devices used for roller hearth furnaces.Dissertation (MEng)--University of Pretoria, 2011.Mechanical and Aeronautical Engineeringunrestricte

Those who have and those who don't; an investigation into the limited scope of application of social security in South Africa

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Biological sample donation and informed consent for neurobiobanking: Evidence from a community survey in Ghana and Nigeria

Copyright: \ua9 2022 Singh et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Introduction Genomic research and neurobiobanking are expanding globally. Empirical evidence on the level of awareness and willingness to donate/share biological samples towards the expansion of neurobiobanking in sub-Saharan Africa is lacking. Aims To ascertain the awareness, perspectives and predictors regarding biological sample donation, sharing and informed consent preferences among community members in Ghana and Nigeria. Methods A questionnaire cross-sectional survey was conducted among randomly selected community members from seven communities in Ghana and Nigeria. Results Of the 1015 respondents with mean age 39.3 years (SD 19.5), about a third had heard of blood donation (37.2%, M: 42.4%, F: 32.0%, p = 0.001) and a quarter were aware of blood sample storage for research (24.5%; M: 29.7%, F: 19.4%, p = 0.151). Two out of ten were willing to donate brain after death (18.8%, M: 22.6%, F: 15.0%, p<0.001). Main reasons for unwillingness to donate brain were; to go back to God complete (46.6%) and lack of knowledge related to brain donation (32.7%). Only a third of the participants were aware of informed consent (31.7%; M: 35.9%, F: 27.5%, p<0.001). Predictors of positive attitude towards biobanking and informed consent were being married, tertiary level education, student status, and belonging to select ethnic groups. Conclusion There is a greater need for research attention in the area of brain banking and informed consent. Improved context-sensitive public education on neurobiobanking and informed consent, in line with the sociocultural diversities, is recommended within the African sub region

Novel functional insights into ischemic stroke biology provided by the first genome-wide association study of stroke in indigenous Africans

\ua9 The Author(s) 2024. Background: African ancestry populations have the highest burden of stroke worldwide, yet the genetic basis of stroke in these populations is obscure. The Stroke Investigative Research and Educational Network (SIREN) is a multicenter study involving 16 sites in West Africa. We conducted the first-ever genome-wide association study (GWAS) of stroke in indigenous Africans. Methods: Cases were consecutively recruited consenting adults (aged > 18 years) with neuroimaging-confirmed ischemic stroke. Stroke-free controls were ascertained using a locally validated Questionnaire for Verifying Stroke-Free Status. DNA genotyping with the H3Africa array was performed, and following initial quality control, GWAS datasets were imputed into the NIH Trans-Omics for Precision Medicine (TOPMed) release2 from BioData Catalyst. Furthermore, we performed fine-mapping, trans-ethnic meta-analysis, and in silico functional characterization to identify likely causal variants with a functional interpretation. Results: We observed genome-wide significant (P-value < 5.0E−8) SNPs associations near AADACL2 and miRNA (MIR5186) genes in chromosome 3 after adjusting for hypertension, diabetes, dyslipidemia, and cardiac status in the base model as covariates. SNPs near the miRNA (MIR4458) gene in chromosome 5 were also associated with stroke (P-value < 1.0E−6). The putative genes near AADACL2, MIR5186, and MIR4458 genes were protective and novel. SNPs associations with stroke in chromosome 2 were more than 77 kb from the closest gene LINC01854 and SNPs in chromosome 7 were more than 116 kb to the closest gene LINC01446 (P-value < 1.0E−6). In addition, we observed SNPs in genes STXBP5-AS1 (chromosome 6), GALTN9 (chromosome 12), FANCA (chromosome 16), and DLGAP1 (chromosome 18) (P-value < 1.0E−6). Both genomic regions near genes AADACL2 and MIR4458 remained significant following fine mapping. Conclusions: Our findings identify potential roles of regulatory miRNA, intergenic non-coding DNA, and intronic non-coding RNA in the biology of ischemic stroke. These findings reveal new molecular targets that promise to help close the current gaps in accurate African ancestry-based genetic stroke’s risk prediction and development of new targeted interventions to prevent or treat stroke

The suitability of South African flaxseed oilcake for inclusion in bread

M. Tech. Food Technology.Flaxseed oilcake as produced by a South African local Oil Mill has not been used directly in human food. The research problem was to evaluate the local flaxseed oilcake for its chemical and microbiological quality and shelf-life. Its suitability for incorporation into bread was investigated. Methods and procedures used included proximate analysis, determinations for total dietary fibre, fatty acid profile, mineral composition and water activity (aw); shelf-life studies and microbiological testing for spoilage micro-organisms and possible pathogenic bacteria. The effect of flaxseed oilcake inclusion in brown bread on the sensory quality of the bread was determined using a trained sensory panel and a consumer panel. A texture analyzer was used to measure the staling of the products. The main findings were that the flaxseed oilcake was high in protein and dietary fibre. The oil was rich in alpha linolenic acid. Toxic mineral content was such that it should be safe at suggested inclusion levels. The oilcake had a low microbial count and no pathogenic bacteria were found. The shelf-life study showed the oil to be relatively stable. Sensory analyses revealed that an 11% inclusion level of oilcake in brown bread was acceptable. In conclusion, it can be recommended that the locally produced oilcake is suitable for use in food and an 11% inclusion level will be safe and acceptable with nutritional benefits to the consumer

Constructal multiscale cylinders rotating in cross-flow

This work describes the effect of steady-state laminar forced convection on multiscale rotating cylinders in cross-flow. The objective was to numerically maximise the heat-transfer-rate-density from the multiscale cylinder assembly under a prescribed pressure drop. Two main configurations were studied, the first was with two different-sized cylinders aligned along the same centreline, and the second configuration was that in which the axis of rotation of the two cylinders was not on the same centreline but the leading edges of the cylinders were on the same line. In both configurations, the cylinders were subjected to two types of rotations, counter-rotation and co-rotation. Numerical solutions for stationary and rotational cylinders were solved to determine the optimum cylinder diameter, spacing and the corresponding maximum heat transfer rate density. The effects of different centres of rotation and the dimensionless pressure drop on the cylinder-to-cylinder spacing, optimal diameter of the cylinder and the maximum heat transfer rate density were reported. Results show that the optimal smaller cylinder diameter was robust with respect to the dimensionless pressure drop number, for both configurations. Results further showed that rotation was only beneficial for cylinders with the same axis of rotation and the effect was minimal when the axis of rotation is different.ai201

Vapor phase nucleation of the short-chain n-alkanes (n-pentane, n-hexane and n-heptane): Experiments and Monte Carlo simulations

We measured the nucleation rates of n-pentane through n-heptane in a supersonic nozzle at temperatures ranging from ca. 109 K to 168 K. For n-pentane and n-hexane, these are the first nucleation rate measurements that have been made, and the trends in the current data agree well with those in the earlier work of Ghosh et al. [J. Chem. Phys. 132, 024307 (2010)] for longer chain alkanes. Complementary Monte Carlo simulations, using the transferable potentials for phase equilibria-united atom potentials, suggest that despite the high degree of supercooling, the critical clusters remain liquid like under experimental conditions for n-pentane through n-heptane, but adopt more ordered structures for n-octane and n-nonane. For all three alkanes, the experimental and simulated nucleation rates are offset by ∼3 orders of magnitude when plotted as a function of ln S/(T/T - 1). Explicitly accounting for the surface tension difference between the real and model substances, or alternatively using the Hale [Phys. Rev. A 33, 4156 (1986); Metall. Mater. Trans. A 23, 1863 (1992)] scaling parameter, Ω, consistent with the model potential, increases the offset to ∼6 orders of magnitude

Perception of Farm Succession Planning by Poultry Farmers in Southwest, Nigeria

This study assessed poultry farm characteristics and poultry farmers’ perception of farm succession planning in southwest Nigeria.  A multistage sampling procedure was used in selecting poultry farmers in Oyo and Osun states.  Data were analyzed using descriptive and inferential statistics. Results reveal that poultry farmers are predominantly small and medium scale farmers. They are mostly sole proprietors (72.5%) and family farm owners (11.9 %).  Most (73.4%) farmers operated on full time basis, while others are either part – time or occasional farmers.  The majority (95.9%) of the farmers had favourable perception towards farm succession planning, 30.3% had complete succession plan and 22.9% had commenced successor participation. There were no significant associations between farm ownership structure, but significant associations exist with farming status (χ2 = 9.7), total farm debt (χ2 = 19.2), and succession planning among the poultry farmers (p≤ 0.05). The study concluded that succession planning is new in the study area and must be further investigated in order to provide a data base for policy decision with regards to livestock (especially poultry) farming and aging proprietorship.Â