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200-nm-thick La- and Sm-doped BaTiO3 thin films with A/B ratio of unity fabricated by magnetron sputtering on the Pt/Ti/SiO2/Si substrate have been characterized. The effects of post-annealing and the amount of dopant on structure and electrical properties were studied. X-ray diffraction studies reveal that the films annealed at 750 °C show tetragonal BaTiO3 crystal structure without any detectable second phase formation. X-ray photoelectron spectroscopy results confirm that La substitutes the A site and Sm is in the B site in lightly doped films. La2O3 or Sm2O3 is present in the BaTiO3 structure when the dopant content is more than 1.4 at. % La or 1.0% Sm. The permittivity increases with increasing annealing temperature up to 750 °C due to the coarse grains and better crystallinity. The leakage current property is found to vary with the type of dopant. [ABSTRACT FROM AUTHOR]

Presents information on a study which assessed calculations for some properties of x-ray diffractors having the shape of a logarithmic spiral in one direction. Calculation of the effective area of the diffractor; Calculation of the collection solid angle; Results and discussion.

Presents a study that examined a procedure for synthesizing the x-ray intensity profile for x-ray optical systems employing curved diffractors. Synthesis of the intensity profile; Broadening effects; Effect of x-ray doublets.

Presents a study on the effect of the rocking curve of a diffracting material and also the effect of varying solid angle on the intensity distribution in an x-ray topograph obtained on a photographic film located between the diffractor and the focal plane. Calculation of the intensity distribution in an x-ray topograph; Schematic diagram of the focal circle of a curved diffractor; Discussion on the effect of misalignment on the intensity distribution.

Presents a study which examined the effect of the diffracting material's rocking curve and the effect of varying solid angle on the intensity distribution in an x-ray topography obtained on a photographic film located between the diffractor and the focal plane. Steps in calculating the intensity distribution; Description of the experimental procedure used; Effect of improper bending for the Johann geometry.

Discusses the calculations of focus characteristics for x-ray focusing systems using either flat or bent crystals with two-dimensional modulated surfaces. Computational formulas; Influence of the Bragg diffraction function on modulation; Optimization of the performance of X-ray optical system in conjunction with the Fresnel diffraction function.

Provides information on a study which presented a wave optics approach to the calculations of the intensity distribution of an X-ray point source image with a two-dimensional focusing geometry. Reason for deriving analytical formulas; Factor considered with the use of the approach; Aspects important in the fields of X-ray spectroscopy; Theory used to describe X-ray diffraction properties.

Presents a study which detailed calculations and analysis of an extended X-ray source image with a two-dimensional focusing geometry. Source of theoretical expressions based upon the calculations for an x-ray point source image; Relationship between the source and the image at the focal plane; Characteristics of all X-ray point sources.

Sm-doped BaTiO3 thin films with ~200 nm thickness fabricated by rf magnetron sputtering system onto Pt/Ti/SiO2/Si substrates have been investigated. The effects of postannealing and the dopant content in a range of 0.1 to 2.2 at.% on microstructure and electrical properties were studied. The films were found to be amorphous in the as-deposited state and became fully crystallized after annealing at 750°C and above. The addition of Sm in the BaTiO3 films resulted in the inhibition of grain growth. Electrical characterizations show that the dielectric permittivity increased with increasing annealing temperatures and the 2.2% Sm-doped film had the low leakage current of 1.29×10-9 A at an applied electric field of 100 KV/cm. [ABSTRACT FROM AUTHOR]

BaTiO3 (BTO) thin films doped with various Sc contents up to 1.1 atom % sputter deposited on Pt/Ti/SiO2/Si substrates were prepared and characterized. The leakage current densities of BTO films were strongly dependent on the Sc content. After annealing at 600°C, the leakage current density measured at 100 kV/cm was 7.1 X 10-6 A/cm² for a 1.1 atom % Sc-doped film, about 3 orders of magnitude lower than 3.7 X 10-3 A/cm² for a pure BTO film. The relatively low leakage current densities of the doped films are thought to be attributed to combined effects of refined grain structures and oxygen vacancies, as confirmed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

The formation of aminoacyl-transfer RNA is a crucial step in ensuring the accuracy of protein synthesis. Despite the central importance of this process in all living organisms, it remains unknown how archaea and some bacteria synthesize Asn-tRNA and Gln-tRNA. These amide aminoacyl-tRNAs can be formed by the direct acylation of tRNA, catalysed by asparaginyl-tRNA synthetase and glutaminyl-tRNA synthetase, respectively. A separate, indirect pathway involves the formation of mis-acylated Asp-tRNA(Asn) or Glu-tRNA(Gln), and the subsequent amidation of these amino acids while they are bound to tRNA, which is catalysed by amidotransferases. Here we show that all archaea possess an archaea-specific heterodimeric amidotransferase (encoded by gatD and gatE) for Gln-tRNA formation. However, Asn-tRNA synthesis in archaea is divergent: some archaea use asparaginyl-tRNA synthetase, whereas others use a heterotrimeric amidotransferase (encoded by the gatA, gatB and gatC genes). Because bacteria primarily use transamidation, and the eukaryal cytoplasm uses glutaminyl-tRNA synthetase, it appears that the three domains use different mechanisms for Gln-tRNA synthesis; as such, this is the only known step in protein synthesis where all three domains have diverged. Closer inspection of the two amidotransferases reveals that each of them recruited a metabolic enzyme to aid its function; this provides direct evidence for a relationship between amino-acid metabolism and protein biosynthesis.