Adaptation of the Romanomermis culicivorax CCA-Adding Enzyme to Miniaturized Armless tRNA Substrates

The mitochondrial genome of the nematode Romanomermis culicivorax encodes for miniaturized hairpin-like tRNA molecules that lack D- as well as T-arms, strongly deviating from the consensus cloverleaf. The single tRNA nucleotidyltransferase of this organism is fully active on armless tRNAs, while the human counterpart is not able to add a complete CCA-end. Transplanting single regions of the Romanomermis enzyme into the human counterpart, we identified a beta-turn element of the catalytic core that—when inserted into the human enzyme—confers full CCA-adding activity on armless tRNAs. This region, originally identified to position the 3′-end of the tRNA primer in the catalytic core, dramatically increases the enzyme’s substrate affinity. While conventional tRNA substrates bind to the enzyme by interactions with the T-arm, this is not possible in the case of armless tRNAs, and the strong contribution of the beta-turn compensates for an otherwise too weak interaction required for the addition of a complete CCA-terminus. This compensation demonstrates the remarkable evolutionary plasticity of the catalytic core elements of this enzyme to adapt to unconventional tRNA substrates.     

Thermo – mechanical properties of SPS produced self-healing thermal barrier coatings containing pure and alloyed MoSi2 particles

Yttria – partially stabilised zirconia (YPSZ) MoSi₂ composites have been designed to prolong the lifetime of the matrix by self – healing cracks during thermal cycling. The healing reaction at high temperatures is based on the decomposition of MoSi₂, leading to a volumetrically expanding reaction product, which seals the crack. In this work, coefficient of thermal expansion (CTE) and the fracture toughness of composites containing MoSi₂ particles, produced by spark plasma sintering (SPS) have been compared to conventional YPSZ. The CTE mismatch between YPSZ and MoSi₂ was found to be small, implying that thermally induced mismatch stresses will be small and the composites have a similar CTE to conventional YPSZ. Fracture toughness was found not to be affected by the particles and showed similar values to unreinforced YPSZ. Cracks introduced by indentation have been shown neither to prefer, or avoid, the particles suggesting that such a composite system is capable of autonomously activating the self – healing reaction.     

Demonstrating kHz Frequency Actuation for Conducting Polymer Microactuators

This paper reports results on ionic EAP micromuscles converting electrical into micromechanical response in open‐air. Translation of small ion motion into large deformation in bending microactuator and its amplification by fundamental resonant frequency are used as tools to demonstrate that small ion vibrations can still occur at frequency as high as 1000 Hz in electrochemical devices. These results are achieved through the microfabrication of ultrathin conducting polymer microactuators. First, the synthesis of robust interpenetrating polymer networks (IPNs) is combined with a spincoating technique in order to tune and drastically reduce the thickness of conducting IPN microactuators using a so‐called “trilayer” configuration. Patterning of electroactive materials as thin as 6 μm is demonstrated with existing technologies, such as standard photolithography and dry etching. Electrochemomechanical characterizations of the micrometer sized beams are presented and compared to existing model. Moreover, thanks to downscaling, large displacements under low voltage stimulation (±4 V) are reported at a frequency as high as 930 Hz corresponding to the fundamental eigenfrequency of the microbeam. Finally, conducting IPN microactuators are then presenting unprecedented combination of softness, low driving voltage, large displacement, and fast response speed, which are the keys for further development to develop new MEMS.     

The potential for electricity conservation and carbon dioxide emission reductions in the household sector of Brazil

Pressure is mounting in large Non-Annex 1 countries like Brazil, China, and India to accept binding commitments to reduce their greenhouse gas emissions in the second, post-2012, commitment period. In the case of Brazil, pressure is higher for the country to commit itself to reduce its emissions from land use changes but, because of the country’s recent high economic growth rates, very soon, this pressure will also turn to reducing its greenhouse gas emissions from electricity production and use in the various sectors of the economy. This paper summarizes the methodological approach, and the results, of a study aimed at assessing the potential for electricity conservation and carbon dioxide emissions reductions in the Brazilian household sector. The study splits the household sector into 20 subsectors, considering five different geographical regions and four household electricity consumption levels (a proxy for different household income levels). Technical, economic, and market potentials are determined for electricity conservation in these 20 subsectors for the period 2005–2030, and results are also translated into carbon dioxide emission reductions using the Clean Development Mechanism (CDM) combined margin (build margin plus operating margin) approach for determining the emission’s factor for the power grids. Results show significant electricity and carbon dioxide reduction potentials at negative costs for both household final consumers (market potential) and the economy as a whole (economic potential) in the residential sector of Brazil.

Extreme Enlargement of the Inverted Repeat Region in the Plastid Genomes of Diatoms from the Genus Climaconeis

We sequenced the plastid genomes of three diatoms from the genus Climaconeis, including two strains formerly designated as Climaconeis scalaris. At 208,097 and 216,580 bp, the plastid genomes of the latter strains are the largest ever sequenced among diatoms and their increased size is explained by the massive expansion of the inverted repeat region. Important rearrangements of gene order were identified among the two populations of Climaconeis cf. scalaris. The other sequenced Climaconeis chloroplast genome is 1.5 times smaller compared with those of the Climaconeis cf. scalaris strains and it features an usual quadripartite structure. The extensive structural changes reported here for the genus Climaconeis are compared with those previously observed for other algae and plants displaying large plastid genomes.     

A new expression of the Ks factor for helical ribbon agitators

The purpose of this note is to present a new model that is able to predict an effective shear rate in a vessel equipped with helical ribbon agitators, when mixing shear‐thinning fluids. This model is based on well established results obtained for non‐Newtonian flow in cylindrical ducts.     

Solid-liquid equilibria in the silicon-rich corner of the Si-O-C system

A phase diagram is proposed for the solid-liquid equilibria in the silicon-rich corner of the Si-O-C system. It is calculated from the solubility data in binary systems, using the model of a regular solution to estimate the interaction coefficient from existing standard reaction data. The solubility of carbon in solid and liquid solutions saturated with SiC is slightly increased by the effect of oxygen. A similar conclusion holds for the effect of carbon on oxygen solubility in solutions saturated with SiO₂. The effect of the third element on the partition coefficient of carbon or of oxygen is negligible. The main result of the proposed diagram is the finding that the solubility can be limited either by SiO₂ saturation or by SiC saturation according to the carbon-to-oxygen ratio.