18 research outputs found
Forced-convection Heat-transfer Characteristics of Molten Sodium Hydroxide
The forced-convection heat-transfer characteristics of sodium hydroxide were experimentally investigated. The heat-transfer data for heating fall slightly above the McAdams correlation line, and the heat-transfer data for cooling are fairly well represented by the McAdams correlation line
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
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NACA Research Memorandums
Memorandum presenting an experimental investigation of the forced-convection heat-transfer characteristics of Flinak flowing through an electrically heated Inconel X test section. The variables included Reynolds numbers, velocities, fluid temperatures, surface temperatures, and heat flux densities
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NACA Research Memorandums
Memorandum presenting an investigation of the forced-convection heat-transfer and pressure-drop characteristics of a staggered closely spaced 0.020-inch wire metal-to-air heat exchanger. Eight wire banks were electrically heated, and the range of variables included bulk Reynolds numbers based on wire diameter and maximum velocity, from 82 to 1900, average wire temperatures up to 1109 degrees R, and heat flux densities up to 84,000 Btu per hour per square foot
Recommended from our members
NACA Research Memorandums
The forced-convection heat-transfer characteristics of sodium hydroxide were experimentally investigated. The heat-transfer data for heating fall slightly above the McAdams correlation line, and the heat-transfer data for cooling are fairly well represented by the McAdams correlation line
Recommended from our members
NACA Research Memorandums
Report describing an experiment to obtain heat-transfer and pressure-drop data for the air side of a liquid-metal to air, shell-and-tube heat exchanger. Testing was conducted in a 500 kilowatt facility using sodium as the shell-side heating fluid. Results regarding the shell-and-tube heat exchanger and finned-tube heat exchanger friction factor are provided
Sleep Apnea Symptoms and Cardiovascular Disease Risks among Haitian Medical Students
Sleep apnea is a prevalent sleep disorder that disproportionately affects blacks and has been previously studied among Caribbean-born blacks in Brooklyn, New York, but there has been negligible research in the Caribbean, specifically Haiti, and developing countries on this pressing health issue. A total of 373 medical students (mean age=20.6 years ± 2.3 years) from a medical school in Haiti participated in this study. Participants were administered a questionnaire assessing their sleep health and cardiovascular outcomes. The rate of sleep apnea symptoms was: snoring (13.2%), excessive daytime sleepiness (73.7%), and difficulty maintaining sleep (25.3%). Many reported falling asleep while watching television (68.2%) or while driving (7.8%). Based on logistic regression analysis, reported nocturnal breathing pauses was the most important predictor of the likelihood of reporting a history of cardiac disease (14.96; 95% CI=1.27–76.07). Findings suggest that more aggressive effort should be made to increase screening of sleep apnea among Haitians, thereby increasing the likelihood for early detection and treatment to reduce sleep-related risk of cardiovascular disease