Porous Silicon and Thermoelectrics

The motivation for, and performance of, silicon nanostructures including porous silicon in thermoelectrics is reviewed. A high thermoelectric figure of merit ZT ~1 has been achieved with a single silicon nanowire and ZT ~0.5 for a porous nanowire array. Very high Seebeck coefficients (3.2 mVK−1) have been achieved in compressed nanoparticles. Data is also presented relevant to two key factors limiting performance in bulk powders. The original size of silicon particles has a significant effect on the thermal conductivities of densified pellets. The intrinsic low electric conductivity can be improved by doping either nanocrystals or surface conductive ligands

Mutant phenotypes for thousands of bacterial genes of unknown function.

One-third of all protein-coding genes from bacterial genomes cannot be annotated with a function. Here, to investigate the functions of these genes, we present genome-wide mutant fitness data from 32 diverse bacteria across dozens of growth conditions. We identified mutant phenotypes for 11,779 protein-coding genes that had not been annotated with a specific function. Many genes could be associated with a specific condition because the gene affected fitness only in that condition, or with another gene in the same bacterium because they had similar mutant phenotypes. Of the poorly annotated genes, 2,316 had associations that have high confidence because they are conserved in other bacteria. By combining these conserved associations with comparative genomics, we identified putative DNA repair proteins; in addition, we propose specific functions for poorly annotated enzymes and transporters and for uncharacterized protein families. Our study demonstrates the scalability of microbial genetics and its utility for improving gene annotations