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Engineering the thermal properties in solids is important for both fundamental physics (e.g. electric and phonon transport) and device applications (e.g. thermal insulating coating, thermoelectrics). In this paper, we report low thermal transport properties of four selenide compounds (BaAg 2 SnSe 4 , BaCu 2 GeSe 4 , BaCu 2 SnSe 4 and SrCu 2 GeSe 4 ) with experimentally-measured thermal conductivity as low as 0.31 ± 0.03 W m -1 K -1 at 673 K for BaAg 2 SnSe 4 . Density functional theory calculations predict κ < 0.3 W m -1 K -1 for BaAg 2 SnSe 4 due to scattering from weakly-bonded Ag-Ag dimers. Defect calculations suggest that achieving high hole doping levels in these materials could be challenging due to monovalent (e.g., Ag) interstitials acting as hole killers, resulting in overall low electrical conductivity in these compounds.

Electronic resistance in lithium‐ion battery positive electrodes is typically attributed to the bulk resistance of the active material and the network resistance of the carbon additive. Expected overpotentials from these bulk components are minimal relative to that from charge‐transfer resistance. However, literature reports show that cell overpotentials are often much more sensitive to conductive additives than the expected level from bulk or percolating‐network transport. This discrepancy motivated a detailed examination of the contact resistance between the active material and conductive additive. The contact and bulk resistances are simultaneously measured using dense bar samples of lithium‐layered oxides (LixNi1 /3Mn1/3Co1/3O2 and LixNi0.5Mn0.3Co0.2O2) in contact with carbon black. It is found that the contact resistance dominates the overall electronic resistance when the length scale is smaller than millimeters; after correcting for contact effects, bulk conductivity of layered oxides is determined to be orders‐of‐magnitude higher than previously reported. In porous electrodes, it is found from three‐electrode electrochemical impedance spectroscopy that the carbon content most heavily influences the low‐frequency regime (≈0.01 Hz), as opposed to the high frequency (>103 Hz) regime expected from electronic percolating properties. Constriction effects within the layered oxide are identified as the dominant mechanism for contact resistance and its implication is investigated for porous electrodes. [ABSTRACT FROM AUTHOR]

When the stop codons TGA, TAA, and TAG are found in the second and third reading frames of a protein-encoding gene, they are considered premature stop codons (PSC). Deinococcus radiodurans disproportionately favored TGA more than the other two triplets as a PSC. The TGA triplet was also found more often in noncoding regions and as a stop codon, though the bias was less pronounced. We investigated this phenomenon in 72 bacterial species with widely differing chromosomal GC contents. Although TGA and TAG were compositionally similar, we found a great variation in use of TGA but a very limited range of use of TAG. The frequency of use of TGA in the gene sequences generally increased with the GC content of the chromosome, while the frequency of use of TAG, like that of TAA, was inversely proportional to the GC content of the chromosome. The patterns of use of TAA, TGA and TAG as real stop codons were less biased and less influenced by the GC content of the chromosome. Bacteria with higher chromosomal GC contents often contained fewer PSC trimers in their genes. Phylogenetically related bacteria often exhibited similar PSC ratios. In addition, metabolically versatile bacteria have significantly fewer PSC trimers in their genes. The bias toward TGA but against TAG as a PSC could not be explained either by the preferential usage of specific codons or by the GC contents of individual chromosomes. We proposed that the quantity and the quality of the PSC in the genome might be important in bacterial evolution.

In this study, the microbial community of the anode-associated soil in sediment microbial fuel cells (MFCs) was investigated. Sediments from the drainage ditch (D) and rice field (RF) were treated with or without autoclaving for single-chamber and mediator-free MFCs. Without sterilization, the voltage output reached a maximum of 124 and 120 mV for the sediments from D and RF on days 30 and 56, respectively. By day 40, the voltage output of the MFCs with sterilization became positive and continued to increase. The microbial communities of the different sediments were clustered together, indicating that the voltage release correlated positively with the presence of soil microbes. Spearman rank correlation analysis showed that the genus Geobacter was positively correlated with Defluviicoccus, Desulfatiglans, Sulfurimonas, Synthrophobacter, Thiobacillus, and Thermodesulfovibrio and negatively correlated with Holophaga, Opitutus, Paludibacter, and Pseudomonas. The genera Geothrix showed the dominant changes in the sediments with sterilization. These results indicate that the sediment MFC device could change the microbial composition adapted to the anodic environment. [ABSTRACT FROM AUTHOR]