High-throughput synthesis of thermoelectric Ca3_3Co4_4O9_9 films

Properties of complex oxide thin films can be tuned over a range of values as a function of mismatch, composition, orientation, and structure. Here, we report a strategy for growing structured epitaxial thermoelectric thin films leading to improved Seebeck coefficient. Instead of using single-crystal sapphire substrates to support epitaxial growth, Ca$_3$Co$_4$O$_9$ films are deposited, using the Pulsed Laser Deposition technique, onto Al$_2$O$_3$ polycrystalline substrates textured by Spark Plasma Sintering. The structural quality of the 2000 \AA thin film was investigated by Transmission Electron Microscopy, while the crystallographic orientation of the grains and the epitaxial relationships were determined by Electron Back Scatter Diffraction. The use of a polycrystalline ceramic template leads to structured films that are in good local epitaxial registry. The Seebeck coefficient is about 170 $\mu$V/K at 300 K, a typical value of misfit material with low carrier density. This high-throughput process, called combinatorial substrate epitaxy, appears to facilitate the rational tuning of functional oxide films, opening a route to the epitaxial synthesis of high quality complex oxides.Comment: Submitted to Applied Physics Letters (2013

Crystallographic and Seismic Anisotropies of Calcite at Different Depths : a Study Using Quantitative Texture Analysis by Neutron Diffraction

Eight samples of limestones and marbles were studied by neutron diffraction to collect quantitative texture (i.e., crystallographic preferred orientations or CPO) of calcite deforming at different depths in the crust. We studied the different Texture patterns developed in shear zones at different depth and their influence on seismic anisotropies. Samples were collected in the French and Italian Alps, Apennines, and Paleozoic Sardinian basement. They are characterized by isotropic to highly anisotropic (e.g., mylonite shear zone) fabrics. Mylonite limestones occur as shear zone horizons within the Cenozoic Southern Domain in Alpine thrust-and-fold belts (Italy), the Brian\ue7onnais domain of the Western Alps (Italy-France border), the Sardinian Paleozoic back-thrusts, or in the Austroalpine intermediate units. The analyzed marbles were collected in the Carrara Marble, in the Austroalpine Units in the Central (Mortirolo) and Western Alps (Valpelline). The temperature and depth of development of fabrics vary from <100\u25e6C, to 800\u25e6C and depth from <10 km to about 30 km, corresponding from upper to lower crust conditions. Quantitative Texture Analysis shows different types of patterns for calcite: random to strongly textured. Textured types may be further separated in orthorhombic and monoclinic (Types A and B), based on the angle defined with the mesoscopic fabrics. Seismic anisotropies were calculated by homogenizing the single-crystal elastic tensor, using the Orientation Distribution Function calculated by Quantitative Texture Analysis. The resulting P-and S-wave anisotropies show a wide variability due to the textural types, temperature and pressure conditions, and dip of the shear planes

X-ray textural and microstructural characterisations by using the Combined Analysis Approach for the optical optimisation of micro-and nano-structured thin films

Nano/micro-crystalline silicon, silicon carbide and zinc selenide sputtered films are chosen to illustrate the potentialities of the X-ray Combined Analysis methodology in characterising textures, structures, residual stresses, phase amounts, twin faults, layer thicknesses and crystallite sizes and shapes. The observed textures range from weak (in Si and SiC films) to very strong (in ZnSe). In all films, crystallites are found anisotropic in shapes and sizes. In nc-Si, no residual stress is observed, but the cell parameters deviate from bulk values due to crystal size reduction. The layer thickness as probed by X-ray diffraction imposes films porosities. In unstressed SiC films the two polymorph phases (hexagonal and cubic) are present and both are textured. In ZnSe films, a ratio of around 55/45 for the cubic and hexagonal phases respectively is quantified and large tensile in-plane residual stresses reaching several hundreds of MPa calculated

Growth and texture of Spark Plasma Sintered Al2O3 ceramics: a combined analysis of X-rays and Electron Back Scatter Diffraction

Textured alumina ceramics were obtained by Spark Plasma Sintering (SPS) of undoped commercial a-Al2O3 powders. Various parameters (density, grain growth, grain size distribution) of the alumina ceramics, sintered at two typical temperatures 1400{\deg}C and 1700{\deg}C, are investigated. Quantitative textural and structural analysis, carried out using a combination of Electron Back Scattering Diffraction (EBSD) and X-ray diffraction (XRD), are represented in the form of mapping, and pole figures. The mechanical properties of these textured alumina ceramics include high elastic modulus and hardness value with high anisotropic nature, opening the door for a large range of applicationsComment: 16 pages, 6 figures, submitted to J. Appl. Phy

A pentatricopeptide repeat protein acts as a site-specificity factor at multiple RNA editing sites with unrelated cis-acting elements in plastids

In plant organelles, RNA editing alters specific cytidine residues to uridine in transcripts. All of the site-specificity factors of RNA editing identified so far are pentatricopeptide repeat (PPR) proteins. A defect in a specific PPR protein often impairs RNA editing at multiple sites, at which the cis-acting elements are not highly conserved. The molecular mechanism for sharing a single PPR protein over multiple sites is still unclear. We focused here on the PPR proteins OTP82 and CRR22, the putative target elements of which are, respectively, partially and barely conserved. Recombinant OTP82 specifically bound to the −15 to 0 regions of its target sites. Recombinant CRR22 specifically bound to the −20 to 0 regions of the ndhB-7 and ndhD-5 sites and to the −17 to 0 region of the rpoB-3 site. Taking this information together with the genetic data, we conclude that OTP82 and CRR22 act as site-specificity factors at multiple sites in plastids. In addition, the high-affinity binding of CRR22 to unrelated cis-acting elements suggests that only certain specific nucleotides in a cis-acting element are sufficient for high-affinity binding of a PPR protein. The cis-acting elements can therefore be rather divergent and still be recognized by a single PPR protein

The representation of coupling interactions in the Material Properties Open Database (MPOD)

International audience; The Material Properties Open Database (MPOD, http//mpod.cimav.edu.mx) is a functional element of the web-based open databases system linked with crystallography. MPOD delivers single-crystal tensor properties in several representations, ranging from numerical matrices to 3D printing. Longitudinal moduli surfaces can be displayed in computers as well as in smart cell phones. Properties are stored as '.mpod' files. IUCr formatting standards (CIF) are followed. The original published paper containing the data is cited. Structural and experimental information is also registered and linked. 'Coupling properties', say piezo-effects and magnetoelectricity, represent interactions linking different subsystems in a material. Currently, piezoelectricity occupies a significant fraction of cases in MPOD. The implications of crystal symmetry in piezoelectricity are systematically taken into account. Matrices' elements and longitudinal moduli surfaces are checked for consistency with the Neumann principle. The inclusion of magnetoelectric axial tensors introduces exciting features into MPOD

A rapid high-throughput method for the detection and quantification of RNA editing based on high-resolution melting of amplicons

We describe a rapid, high-throughput method to scan for new RNA editing sites. This method is adapted from high-resolution melting (HRM) analysis of amplicons, a technique used in clinical research to detect mutations in genomes. The assay was validated by the discovery of six new editing sites in different chloroplast transcripts of Arabidopsis thaliana. A screen of a collection of mutants uncovered a mutant defective for editing of one of the newly discovered sites. We successfully adapted the technique to quantify editing of partially edited sites in different individuals or different tissues. This new method will be easily applicable to RNA from any organism and should greatly accelerate the study of the role of RNA editing in physiological processes as diverse as plant development or human health

Breeding grasses for capacity to biofuel production or silage feeding value: an updated list of genes involved in maize secondary cell wall biosynthesis and assembly

In the near future, maize, sorghum, or switchgrass stovers and cereal straws will be a significant source of carbohydrates for sustainable biofuel production, in addition to the current use of grass silage in cattle feeding. However, cell wall properties, including the enzymatic degradability of structural polysaccharides in industrial fermenters or animal rumen, is greatly influenced by the embedding of cell wall carbohydrates in lignin matrix, and the linkages between lignins, p-hydroxycinnamic acids, and arabinoxylans. Breeding for higher and cheaper biofuel or silage production will thus be based on the discovery of genetic traits involved in each cell wall component biosynthesis and deposition in each lignified tissue. Due to its considerable genetic and genomic backgrounds, maize is the relevant model species for identifying traits underlying cell wall degradability variations in grasses. Maize genes involved or putatively involved in the biosynthesis of cell wall phenolic compounds, cell wall carbohydrates and regulation factors were therefore searched for using data available in grass, Arabidopsis, and woody species (mostly poplar and eucalyptus). All maize ortholog genes were searched for using protein sequences and a “blastp” strategy against data available in the www.maizesequence.org database. Genes were also mapped in silico considering their physical position in the same database. Finally, 409 candidate genes putatively involved in secondary cell wall biosynthesis and assembly were shown in the maize genome, out of which 130 were related to phenolic compound biosynthesis, 81 were related to cell wall carbohydrate biosynthesis, and 198 were involved in more or less known regulation mechanisms. Most probable candidate genes involved in regulation and assembly of secondary cell wall belonged to the MYB (45 genes) and NAC (38 genes) families, but also included zinc finger and HDZipIII encoding genes. While genes involved in ferulic acid cross-linkages with other cell wall components were little known, several families putatively involved in (arabino)-xylan chain biosynthesis and in feruloyl transfer were shown, including especially arabinosyl-CoA-acyltransferases, feruloyl-AX b-1,2-xylosyl transferases, and xylan-O-3-arabinosyl transferases. This candidate gene list, which focused on genes and orthologs known to be involved in cell wall component biosynthesis and regulation, cannot be considered as exhaustive. Other genes, whose role in cell wall lignification and deposition have not yet been defined, should very likely be added to the list of candidates required for secondary cell wall assembly. Genes encoding proteins of still unknown function should also be added to the list, as several of the latter are probably involved in lignified tissue biosynthesis and deposition