Effectiveness of PVC coatings as thermal insulation for domestic hot-water piping

A 2 mm polyvinyl chloride (PVC) coating was predicted by computer modelling to be effective in reducing heat losses from pipes when they were exposed to draughts. However, the same coating was predicted to be of little benefit to pipes installed in stagnant air; a situation that would occur in many building cavities. The results predicted by the computer simulation were confirmed by wind tunnel tests at a range of air velocities. The explanation for the apparent anomaly was found in the different proportions of convected and radiated heat loss in the two situations. Where a pipe is exposed to draughts, the convective component of heat transfer is many times the magnitude of the radiative component. In these situations the addition of a PVC coating makes a significant reduction to the convective component and a less significant increase in radiated heat loss. Hence, adding the PVC produces a net reduction in the total heat loss rate. However, in relatively stagnant air the radiated component of heat transfer is more significant. Adding a PVC coating, having a higher emissivity than bare copper, increases the rate of radiant heat losses and compromises the insulation effect.

A Fifth Locus for Primary Autosomal Recessive Microcephaly Maps to Chromosome 1q31

Primary microcephaly is a genetic disorder in which an affected individual has a head circumference >3 SDs below the age- and sex-related mean. A small but apparently normally formed brain is the reason for the reduced head circumference, and, probably because of this, all affected individuals are mentally retarded. The condition is genetically heterogeneous, and four loci have already been identified. We now report a fifth locus, MCPH5, which is an 8-cM region mapping to chromosome 1q31, defined by the markers GATA135F02 and D1S1678