Continuous and Collective Grain Rotation in Nanoscale Thin Films during Silicidation.

Texture evolution is an important issue in materials and nanosciences. Understanding it is fundamental for controlling the final orientation, which in fine controls the desired properties of nanodevices. Here, we reveal the formation of a peculiar texture during the silicidation of nanoscale Pd thin films. We demonstrate that the crystallographic relationship observed between the silicide and the Si(001) substrate, named gyroaxy, evolves continuously and collectively during silicidation. This continuous rotation of the nanosized grains over a wide angular range is proposed to be associated with a diffusional mechanism.

Internal contamination by actinides after wounding: a robust rodent model for assessment of local and distant actinide retention.

Internal contamination by actinides following wounding may occur in nuclear fuel industry workers or subsequent to terrorist activities, causing dissemination of radioactive elements. Contamination by alpha particle emitting actinides can result in pathological effects, either local or distant from the site of entry. The objective of the present study was to develop a robust experimental approach in the rat for short- and long- term actinide contamination following wounding by incision of the skin and muscles of the hind limb. Anesthetized rats were contaminated with Mixed OXide (MOX, uranium, plutonium oxides containing 7.1% plutonium) or plutonium nitrate (Pu nitrate) following wounding by deep incision of the hind leg. Actinide excretion and tissue levels were measured as well as histological changes from 2 h to 3 mo. Humid swabs were used for rapid evaluation of contamination levels and proved to be an initial guide for contamination levels. Although the activity transferred from wound to blood is higher after contamination with a moderately soluble form of plutonium (nitrate), at 7 d most of the MOX (98%) or Pu nitrate (87%) was retained at the wound site. Rapid actinide retention in liver and bone was observed within 24 h, which increased up to 3 mo. After MOX contamination, a more rapid initial urinary excretion of americium was observed compared with plutonium. At 3 mo, around 95% of activity remained at the wound site, and excretion of Pu and Am was extremely low. This experimental approach could be applied to other situations involving contamination following wounding including rupture of the dermal, vascular, and muscle barriers.

Computer processing of electron microscope cross sections of multilayer mirrors.

A method is developed for determining interface profiles of extreme ultraviolet- (EUV-) layered synthetic microstructures (LSM's). It is based on computer processing digitized LSM electron micrographs. This study was carried out on a tungsten/carbon multilayer. Interfacial roughness has been characterized by means of two statistical parameters, i.e., the root mean square (rms) roughness height and the autocorrelation length varsigma. Additionally, knowledge of interface profiles should enable one to study more accurately the structural behavior of the stack, from the substrate to the top, and, in turn, help one better understand its EUV optical properties.

Influence of the Number of Bilayers on the Optical Performances of X-UV Multilayer Interferential Mirrors.

The influence of the number of bilayers on the optical performances of actual X-UV multilayer interferential mirrors (MIMs) has been studied in order to emphasize the experimental restrictions in the designing of "thick" mirrors used for the development of etched multilayer gratings. Several sets of samples (W/C, Mo/Si) with increasing number of bilayers have been manufactured in the very same conditions by means of a sputtering technique. X-ray diffraction characterization at Cu-Kα radiation (λ = 1.54018 Å) exhibits technical constraints in the achievement of multilayer structures with large number of bilayers. We obtain a gradual loss of reflectivity for deposition times greater than 1h 30 min to 2h without significant drift of the MIM's geometrical parameters (period and division parameter). In the same time, absolute reflectivity measurements at Cu-Lα radiation (λ = 1.333 nm) emphasize satisfying optical and spectroscopic performances of W/C thick samples ( 150 bilayers).

Mechanism of protein C deficiency in a patient with arginine 358 alpha 1-antitrypsin (Pittsburgh mutation): role in the maintenance of hemostatic balance.

We recently described a new case of alpha 1-antithrombin (alpha 1-AT) Pittsburgh, a mutation that transforms alpha 1-AT into a potent inhibitor of thrombin. In contrast to the originally described patient, who had a severe hemorrhagic diathesis, our proband had only a mild bleeding tendency. The current article explores possible mechanisms for the relative hemostatic competence of our patient. The levels of both normal and mutant alpha 1-AT were similar to those of the previously reported case, as was the rise in plasma antithrombin level during an acute phase reaction. The level of protein C, however, was found on several occasions to be approximately 20% of normal. Family studies and examination of the patient's protein C gene on a denaturing gel failed to identify an abnormality. Moreover, the patient's protein C showed no abnormalities suggestive of faulty intracellular processing. However, the protein C in his plasma was for the most part in the activated form and bound to the mutant alpha 1-AT. Thus it is likely that the strong affinity of mutant alpha 1-AT for protein C leads to an increased turnover and thus to a low circulating level. A seeming flaw in that scenario is that the mutant alpha 1-AT also has a very high affinity for thrombin and might be expected therefore to block the activation of protein C. When thrombin was complexed with thrombomodulin (as it is when protein C is physiologically activated at the endothelial surface), mutant alpha 1-AT was far less able to inhibit thrombin than was the case for the free enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a Clostridium cocleatum strain involved in an anti-Clostridium difficile barrier effect and determination of its mucin-degrading enzymes.

We isolated Gram-positive circular bacterium HB1 from intestinal microflora showing resistance to colonization by Clostridium difficile in mice (Su et. al., 1986a,b). We studied its enzymatic capacity to degrade mucin the first potential barrier to implantation of strains in the intestine. Its biochemical characteristics, terminal metabolites and the electrophoretic profiles of proteins and DNA-DNA homology indicated that it was a strain of Clostridium cocleatum. This strain displayed numerous glucosidase activities which were assumed to play a role in the degradation of mucin oligosaccharide chains in the digestive tract. These enzymes included alpha- and beta-galactosidases, beta-glucosidase, beta-N-acetylglucosaminidase, sialidase and alpha-N-acetylgalactosaminidase.