Commentary on Ferguson, et al., "Impact of Non-pharmaceutical Interventions (NPIs) to Reduce COVID-19 Mortality and Healthcare Demand".

A recent manuscript (Ferguson et al. in Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand, Imperial College COVID-19 Response Team, London, 2020. https://www.imperial.ac.uk/media/imperial-college/medicine/sph/ide/gida-fellowships/Imperial-College-COVID19-NPI-modelling-16-03-2020.pdf) from Imperial College modelers examining ways to mitigate and control the spread of COVID-19 has attracted much attention. In this paper, we will discuss a coarse taxonomy of models and explore the context and significance of the Imperial College and other models in contributing to the analysis of COVID-19.

Relationships between water balance properties and habitat characteristics in the sibling Hawaiian Drosophilids, D. mimica and D. kambysellisi.

Four populations of Drosophila mimica and 1 population of D. kambysellisi collected at sites which differed in wetness were examined for several water balance characteristics. Net water loss per hour increased as av (relative humidity/100) decreased in all populations, but the rate of increase was lower in populations from dry sites. When exposed to 0.70 av, D. kambysellisi, which were from a rain forest, lost water faster and died sooner than did D. mimica. Two D. mimica collecting sites were divided into smaller units based on substrate type at one site and on litter wettness at the other site. The D. mimica at the first site were homogeneous with respect to the water balance properties studied here, but in the second site, there was evidence of population differentiation associated with litter wettness.

A Modified Model of Segregation Distortion in DROSOPHILA MELANOGASTER.

Elements of the Segregation Distorter (SD) system of Drosophila melanogaster, Sd and Rsp, were analyzed and the following points were established: (1) The model of multiple alleles at the Rsp(s) locus proposed by Martin and Hiraizumi (1979) is supported by our observations. (2) A modifier of SD, tentatively symbolized M(SD), was found close to cn (2R-57.5). (3) Sd heterozygous males were found to show, under certain genotypic condition, almost complete sterility.-Based upon these observations, the following modified model of segregation distortion is proposed: (1) The M(SD) locus produces a multimeric repressor protein that binds to the Rsp locus as a necessary condition for normal spermiogenesis. M(SD) homozygotes produce a repressor M(SD)/M(SD); whereas, a homozygote for its normal allele M(+)(SD) produces a M(+)(SD)/M(+)(SD) repressor. M(SD)/M(+)(SD) heterzygotes produce a M(SD)/M(+)(SD) repressor. (2) The Sd locus produces a certain product that, like an inducer in the lactose system of E. coli, tends to bind with the repressor complexed with the Rsp locus. This binding disrupts the repressor-Rsp complex, causing Rsp locus to be turned on. The product of Rsp transcription, in turn, results in sperm dysfunction. (3) Rsp(i), an allele of Rsp, has a strong complexing affinity with the repressor such that the Rsp(i)-repressor complex is "resistant" to the inducing activity of Sd product. Rsp(s), on the other hand, has a weaker complexing affinity than that of Rsp(i), and the degree of affinity varies among different Rsp(s) alleles.-A possible extension of the above model is discussed.