ABSTRACT
Electron BackScatter Diffraction (EBSD) is often used for semi-quantitative analysis of dislocations in metals. In general, disorientation is used to assess Geometrically Necessary Dislocations (GNDs) densities. In the present paper, we demonstrate that the use of disorientation can lead to inaccurate results. For example, using the disorientation leads to different GND density in recrystallized grains which cannot be physically justified. The use of disorientation gradients allows accounting for measurement noise and leads to more accurate results. Misorientation gradient is then used to analyze dislocations boundaries following the same principle applied on TEM data before. In previous papers, dislocations boundaries were defined as Geometrically Necessary Boundaries (GNBs) and Incidental Dislocation Boundaries (IDBs). It has been demonstrated in the past, through transmission electron microscopy data, that the probability density distribution of the disorientation of IDBs and GNBs can be described with a linear combination of two Rayleigh functions. Such function can also describe the probability density of disorientation gradient obtained through EBSD data as reported in this paper. This opens the route for determining IDBs and GNBs probability density distribution functions separately from EBSD data, with an increased statistical relevance as compared to TEM data. The method is applied on deformed Tantalum where grains exhibit dislocation boundaries, as observed using electron channeling contrast imaging.
ABSTRACT
The self-assembly of condensable amphiphile molecules in water is an attractive approach for the synthesis of mesostructured hybrid materials. In this article, we focus on aminoundecyltriethoxysilane (AUT), a condensable "bola-amphiphile", i.e., an amphiphilic molecule possessing two polar heads on both sides of an aliphatic chain. In the present case, one side is a condensable triethoxysilane, and the other side is an amino group. We report on the self-assembly of AUT in mixtures of water and tetraethoxysilane (TEOS). In situ small-angle X-ray scattering (SAXS) measurements allowed us to follow the evolution of the structure from the liquid state up to the solid material formed upon catalytic polycondensation. Depending on the medium composition, hexagonal or lamellar structures can be observed in the final material. These observations allowed us to propose a model for the self-assembly of AUT in water/TEOS mixtures that we were able to validate by simulations of the SAXS profiles. By taking advantage of the modularity of such a system, it proves possible to prepare in a simple way various structured hybrid materials possessing a high number of available organic functions without using sacrificial surfactant molecules.
ABSTRACT
Spiramycin, a true macrolide antibiotic, is the only agent which can be used for the preventive treatment of congenital toxoplasmosis. It gives very high levels in the human placenta, but its transplacental transfer is likely to be very poor, so that it may not cure an already infected foetus. We studied the human placental transfer of spiramycin by an in vitro perfusion model of placentas obtained at term of uncomplicated pregnancies. The transfer rate of spiramycin was found to be close to 9% of the maternal circulating concentrations and 23% of the antipyrine transfer rate, which is only flow-limited. Possible therapeutic implications of these results are discussed.
Subject(s)
Leucomycins/metabolism , Maternal-Fetal Exchange , Antipyrine/blood , Female , Fetus/metabolism , Humans , In Vitro Techniques , Kinetics , Perfusion , PregnancyABSTRACT
Lutzomyia umbratilis is confirmed as the vector of Leishmania braziliensis guyanensis, the cause of "pian bois" in man in French Guiana. Although spending most of the year in the forest canopy, this sandfly is abundant at ground level for about two weeks at the beginning of the long rainy season. The maximum number of infective bites per man per hour (3.9) was reached at the end of November 1979. Infections were found in one of seven Potos flavus, seven of 15 Choleopus didactylus and two of 19 rodents examined. C. didactylus seems likely to be the main reservoir.
