Mechanisms of damage formation in Eu-implanted AlN

International audienceX-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate the evolution of damage during implantation of 300 keV Eu ions at room temperature in AlN. At low fluence, a strain increase is observed in a buried layer where clusters of point defects and stacking faults (SFs) coexist. At higher fluence, a saturation of the strain is observed in this layer, and the XRD curves exhibit characteristic features which coupled with TEM results enable the identification of additional, spatially separated, dilated and contracted regions. From these observations, the following damage mechanisms are proposed. As the SFs grow by trapping point defects, a dense network of basal and prismatic SFs forms, which leads to the ejection of point defects from the buried damaged layer and consequently to the saturation of the strain. In this process, interstitials in excess migrate towards the undamaged bulk where they form clusters inducing large strain values. In contrast, defects ejected towards the surface either remain isolated or form isolated dislocation loops and SFs depending on their nature, i.e., interstitial or vacancy. This is probably the main difference with GaN where the defects ejected from the buried damaged layer contribute to the fast propagation of the dense SFs network towards the surface due to their relatively low formation energies. As a consequence, whilst nanocrystallization occurs at the surface of GaN, the relative confinement of defects and implanted atoms in the buried layer of AlN results in its amorphization, although at extremely high fluences (∼10^17 Eu/cm^2)

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This document contains a formal description of the Rhodium language. Section 1 presents the Rhodium syntax. Section 2 presents our composing framework, which is used to formalize Rhodium analyses. Section 3 presents forward analyses and transformations, whereas section 4 presents backward analyses and transformations. Sections 5 and 6 present the frameworks for flow-insensitive and interprocedural analyses, respectively. Finally, appendix A is a transcript of all of our Rhodium code. 1 Chapter

Bilirubin protects astrocytes from its own toxicity by inducing up-regulation and translocation of multidrug resistance-associated protein 1 (Mrp1)

Unconjugated bilirubin (UCB) causes encephalopathy in severely jaundiced neonates by damaging astrocytes and neurons. Astrocytes, which help defend the brain against cytotoxic insults, express the ATP-dependent transporter, multidrug resistance-associated protein 1 (Mrp1), which mediates export of organic anions, probably including UCB. We therefore studied whether exposure to UCB affects the expression and intracellular localization of Mrp1 in cultured mouse astroglial cells (>95% astrocytes). Mrp1 was localized and quantitated by confocal laser scanning microscopy and double immunofluorescence labeling by using specific antibodies against Mrp1 and the astrocyte marker glial fibrillary acidic protein, plus the Golgi marker wheat germ agglutinin (WGA). In unexposed astrocytes, Mrp1 colocalized with WGA in the Golgi apparatus. Exposure to UCB at a low unbound concentration (B(f))of 40 nM caused rapid redistribution of Mrp1 from the Golgi throughout the cytoplasm to the plasma membrane, with a peak 5-fold increase in Mrp1 immunofluorescence intensity from 30 to 120 min. B(f) above aqueous saturation produced a similar but aborted response. Exposure to this higher B(f) for 16 h markedly decreased Trypan blue exclusion and methylthiazoletetrazoilum activity and increased apoptosis 5-fold by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay. These toxic effects were modestly increased by inhibition of Mrp1 activity with 3-([3-(2-[7-chloro-2-quinolinyl]ethenyl)phenyl-(3-dimethylamino-3-oxopropyl)-thio-methyl]thio)propanoic acid (MK571). By contrast, B(f) = 40 nM caused injury only if Mrp1 activity was inhibited by MK571, which also blocked translocation of Mrp1. Our conclusion is that in astrocytes, UCB up-regulates expression of Mrp1 and promotes its trafficking from the Golgi to the plasma membrane, thus moderating cytotoxicity from UCB, presumably by limiting its intracellular accumulation