Corrosion and Passivation of Fe and FeN Films

The role of nitrogen in corrosion and passivation of thin Fe-N films was studied. Sputtered films with different levels of nitrogen were characterized for composition, conductivity, stress, and crystallinity. Corrosion and passivation of the films were evaluated by electrochemical measurements combined with in situ ellipsometry and ex situ x-ray photoelectron spectroscopy. The results indicate that in deaerated solutions the primary action of N is to reduce the catalytic activity of the surface for the hydrogen reaction and thereby reduce corrosion. In aerated solutions the corrosion rate increases with N content. Kinetics of the protective oxide formation as a function of potential, percent N, and the presence of borate buffer are discussed in detail. The work is relevant to the behavior of oxide-free Fe-N surfaces in contact with mild, nearly neutral electrolytes, such as could be used in fabrication of magnetic recording heads

X-Ray Absorption Study of Electrochemically Grown Oxide Films on Al-Cr Sputtered Alloys I. Ex situ Studies

Oxides grown electrochemically in a borate buffer solution on the surface of sputter-deposited AlCr alloy films were studied by x-ray absorption near edge structure (XANES). The measurements were made in air immediately following polarization in solution. The oxides were also examined with x-ray photoelectron spectroscopy (XPS). The effects of alloy composition and thickness as well as applied potential were studied. Cr( VI) was found in the oxides if the applied potential was sufficiently high. The Cr(VI) was enriched at the interface with the electrolyte and the proportion of Cr(VI) in the oxide was higher for alloy films containing more Cr. The Cr(VI) in the oxides could be reversibly reduced to Cr(III) and reoxidized to Cr(VI) by subsequent potentiostatic treatments in solution.Research was carried out in part at the National Synchroton Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. A. J. D. and H. S. I. were supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016

Modyfikacje pomp protonowych plazmolemy i tonoplastu w warunkach stresu solnego

W pracy wykazano, że frakcja cytosolowa z korzeni ogórków traktowanych NaCl, stymulowała plazmolemową i tonoplastową ATPazę izolowaną z roślin nie poddanych działaniu soli. Stymulujący efekt frakcji cytosolowej był eliminowany przez wysoką temperaturę i staurosporynę. Wprowadzenie jonów wapnia z ekstraktem z roślin niepoddanych działaniu soli, do zawiesiny błon izolowanych z roślin również nietraktowanych solą, stymulowało pompy protonowe. Takie rezultaty sugerowały udział specyficznych białkowych kinaz, zależnych od wapnia w aktywacji ATPaz błonowych w warunkach stresu solnego. Doświadczenia z zastosowaniem W7, antagonisty kalmoduliny, zawęziły szeroką grupę kinaz do tych zależnych od kompleksu wapń-kalmodulina. Dodatkowo wykazano, że w błonach izolowanych z korzeni ogórków traktowanych NaCl funkcjonuje antyport Na⁺/H⁺, który wyrzuca nadmiar jonów sodu z cytoplazmy.The extract from NaCl treated cucumber roots stimulated both, the plasma membrane and tonoplast ATPases isolated from unstressed plants. Stimulatory effect of the extract from NaCl treated plants was eliminated by high temperature and staurosporine. On the other hand, addition of Ca²⁺ together with extract from unstressed plants to the membrane prepared from unstressed roots stimulated both proton pumps. Such results suggested a participation of specific Ca-dependent kinases in activation of the membrane ATPases under salt stress conditions. Experiments with W7, an antagonist of calmodulin, restricted a wide group of kinases to those dependent on the calcium-calmodulin complex. Furthermore, it was found that in membranes isolated from NaCl stressed cucumber roots operated the Na⁺/H⁺ antiport, which excluded sodium ions from cytoplasm

Chimpanzees as fauna:Comparisons of sympatric large mammals across long-term study sites

Although much research has shown otherwise, chimpanzees are still often classed as rainforest-dwellers. Most long-term studies of wild chimpanzees (Pan troglodytes) are not situated in evergreen, closed-canopy equatorial forests, but instead are conducted in more open habitats. This study aims to elucidate the extent of chimpanzee ecological diversity by scrutinizing (recently) sympatric mammalian fauna at established study sites. We compiled presence or absence data on large mammal species at eight sites: Assirik, Bossou, Budongo, Gombe, Kibale, Lopé, Mahale, and Tai. The sites were rank ordered on the most basic ecological variable: annual total rainfall. Only three of the 65 mammalian genera compiled were sympatric with chimpanzees at all sites: Potamochoerus (bushpig), Syncerus (buffalo), and Panthera pardus (leopard). Some subfamilies (e.g. colobines) were present at most sites, but some families (e.g. hyenids) were absent at most sites. Some taxa (e.g. suids, cercopithecines) correlated better than others (e.g. canids) with basic ecological variables. The most extreme chimpanzee study site for which data are available is Assirik, Senegal. Nowhere else are chimpanzees sympatric with Erythrocebus, Alcelaphus, Hippotragus, and Ourebia. As chimpanzees are often behavioral models for extinct hominins, these living faunal assemblages have implications for paleo-ecological reconstructions of ancestral habitats.</p