Extended analysis of Skylab experiment M558 data

A careful review of the data from Skylab M558 was made in an effort to explain the apparent anomaly of the existence of radial concentration gradients whereas none should bave been observed. The very close modelling of the experimental axial concentration profiles by the unsteady-state one-dimensional solution of Fick's Law of self-diffusion in liquid zinc, and the condition of initial uniform concentration in the radioactive pellet portion of the experimental specimens would have precluded the appearance of such radial concentration gradients. Statistical analyses were used to test the significance of the observed deviation from radial-concentration homogeneity. A student t-distribution test of significance showed that, at 90% or even at 80% level of significance, there were no significant deviations from uniformity in radial concentrations. It was also concluded that the two likely causes of any deviation that existed were the zinc to zinc-65 bonding procedure and surface phenomena such as surface tension and capillary action

Diffusion in liquid metal systems

Physical properties of twenty liquid metals are reported; some of the data on such liquid metal properties as density, electrical resistivity, thermal conductivity, and heat capacity are summarized in graphical form. Data on laboratory handling and safety procedure are summarized for each metal; heat-transfer-correlations for liquid metals under various conditions of laminar and turbulent flow are included. Where sufficient data were available, temperature equations of properties were obtained by the method of least-squares fit. All values of properties given are valid in the given liquid phase ranges only. Additional tabular data on some 40 metals are reported in the appendix. Included is a brief description of experiments that were performed to investigate diffusion in liquid indium-gallium systems

Phase change solidification phenomena for thermal control Annual summary report, 21 Nov. 1968 - 31 Dec. 1969

Solidification effects on performance and suitability of phase-change materials in thermal control device

Thermal modeling of phase change solidification in thermal control devices including natural convection effects

Natural convection effects in phase change thermal control devices were studied. A mathematical model was developed to evaluate natural convection effects in a phase change test cell undergoing solidification. Although natural convection effects are minimized in flight spacecraft, all phase change devices are ground tested. The mathematical approach to the problem was to first develop a transient two-dimensional conduction heat transfer model for the solidification of a normal paraffin of finite geometry. Next, a transient two-dimensional model was developed for the solidification of the same paraffin by a combined conduction-natural-convection heat transfer model. Throughout the study, n-hexadecane (n-C16H34) was used as the phase-change material in both the theoretical and the experimental work. The models were based on the transient two-dimensional finite difference solutions of the energy, continuity, and momentum equations

An analysis of the uptake of anti-retroviral treatment among pregnant women in Nigeria from 2015 to 2020.

The percentage of Human Immunodeficiency Virus (HIV) positive pregnant women that receive anti-retroviral treatment in Nigeria is low and has been declining. Consequently, 14% of all new infections among children in 2020 occurred in Nigeria. A detailed analysis of available data was undertaken to generate evidence to inform remedial actions. Data from routine service delivery, national surveys and models were analyzed for the six-year period from 2015 to 2020. Numbers and percentages were calculated for antenatal registrations, HIV testing, HIV positive pregnant women and HIV positive pregnant women on antiretroviral treatment. The Mann-Kendall Trend Test was used to determine the presence of time trends when the p-value was less than 0.05. In 2020, only 35% of an estimated 7.8 million pregnant women received antenatal care at a health facility that provided and reported PMTCT services. Within these facilities, the percentage of HIV-positive pregnant women on anti-retroviral treatment from 71% in 2015 to 88% in 2020. However, declining HIV positivity rates at these antenatal clinics and an absence of expansion of PMTCT services to other pregnant women due to cost-efficiency considerations contributed to a progressive decline in national PMTCT coverage rates. To achieve elimination of mother-to-child transmission of HIV, all pregnant women should be offered a HIV test, all who are HIV positive should be given anti-retroviral treatment, and all PMTCT services should be reported