Solar cycle variability of Mars dayside exospheric temperatures: Model evaluation of underlying thermal balances

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95086/1/grl25450.pd

A functional peptidyl-tRNA hydrolase, ICT1, has been recruited into the human mitochondrial ribosome

Bioinformatic analysis classifies the human protein encoded by immature colon carcinoma transcript-1 (ICT1) as one of a family of four putative mitochondrial translation release factors. However, this has not been supported by any experimental evidence. As only a single member of this family, mtRF1a, is required to terminate the synthesis of all 13 mitochondrially encoded polypeptides, the true physiological function of ICT1 was unclear. Here, we report that ICT1 is an essential mitochondrial protein, but unlike the other family members that are matrix-soluble, ICT1 has become an integral component of the human mitoribosome. Release-factor assays show that although ICT1 has retained its ribosome-dependent PTH activity, this is codon-independent; consistent with its loss of both domains that promote codon recognition in class-I release factors. Mutation of the GGQ domain common to ribosome-dependent PTHs causes a loss of activity in vitro and, crucially, a loss of cell viability, in vivo. We suggest that ICT1 may be essential for hydrolysis of prematurely terminated peptidyl-tRNA moieties in stalled mitoribosomes

Advanced Combustion in Natural Gas-Fueled Engines

Current energy and emission regulations set the requirements to increase the use of natural gas in engines for transportation and power generation. The characteristics of natural gas are high octane number, less amount of carbon in the molecule, suitable to lean combustion, less ignitibility, etc. There are some advantages of using natural gas for engine combustion. First, less carbon dioxide is emitted due to its molecular characteristics. Second, higher thermal efficiency is achieved owing to the high compression ratio compared to that of gasoline engines. Natural gas has higher octane number so that knock is hard to occur even at high compression ratios. However, this becomes a disadvantage in homogeneous charge compression ignition (HCCI) engines or compression ignition engines because the initial auto-ignition is difficult to be achieved. When natural gas is used in a diesel engine, primary natural gas–air mixture is ignited with small amount of diesel fuel. It was found that under high pressure, lean conditions, and with the control of certain parameters, the end gas is auto-ignited without knock and improves the engine combustion efficiency. Recently, some new fuel ignition technologies have been developed to be applied to natural gas engines. These are the laser-assisted and plasma-assisted ignition systems with high energy and compact size