Data availabilitySummary statistics generated by COVID-19 Host Genetics Initiative are available online (https://www.covid19hg.org/results/r6/). The analyses described here use the freeze 6 data. The COVID-19 Host Genetics Initiative continues to regularly release new data freezes. Summary statistics for samples from individuals of non-European ancestry are not currently available owing to the small individual sample sizes of these groups, but the results for 23 loci lead variants are reported in Supplementary Table 3. Individual-level data can be requested directly from the authors of the contributing studies, listed in Supplementary Table 1.

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In electrical discharge machining (EDM), material is removed by a series of electrical sparks that develops a temperature in the range 8 000 C-12 000 C between the electrode and the workpiece. Due to the high temperature of the sparks, the workpiece is melted and vaporized. At the same time, the electrode material is also eroded by melting and vaporization. This erosion of the electrode is termed as electrode wear (EW). The EW process is similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrodes in EDM. Due to EW, electrodes lose their dimensions resulting in inaccuracy of the cavity formed by EDM. This paper reports on the study of the effect of electrode cooling during the EDM of titanium alloy (Ti-6Al-4V). Investigation on the effect of electrode cooling on electrode wear was carried out. Current, pulse on-time, pause off-time, and gap voltage were considered as the machining parameters while EW is the response. Analysis of the influence of electrode cooling on the response has been carried out, and it was possible to reduce EW by 27% using this method.

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The resistance of a material to an indentation on microscopic scale is an indication of its micro-hardness. To a lubrication engineer, micro-hardness is synonymous with surface wear resistance of a material. In this study, an attempt was made to enhance the surface micro-hardness of titanium alloy (Ti-6Al-4V) through modification of electrical discharge machining process parameters. These parameters are the electrode, the dielectric fluid and the electrical variables of the machine. Cu–TaC composite electrode produced through powder metallurgy method was used during the electrical discharge machining with different urea concentrations in distilled water as dielectric fluid. The electrical variables used were the peak current, the pulse duration and the duty factor. Electrical discharge machining was also conducted with copper (Cu) powder metallurgy electrode with distilled water dielectric fluid for comparison. The results showed that the micro-hardness of the electrical discharge machined surfaces with Cu–TaC electrode/urea dielectric fluid was generally higher than that of those with Cu electrode/distilled water dielectric fluid. The highest micro-hardness of 1795 Hv was attained with 10 g/L of urea concentration.