Comparison of sulfuric and oxalic acid anodizing for preparation of thermal control coatings for spacecraft

The development of thermal control surfaces, which maintain stable solar absorptivity and infrared emissivity over long periods, is challenging due to severe conditions in low-Earth orbit (LEO). Some candidate coatings are second-surface silver-coated Teflon; second-surface, silvered optical solar reflectors made of glass or quartz; and anodized aluminum. Sulfuric acid anodized and oxalic acid anodized aluminum was evaluated under simulated LEO conditions. Oxalic acid anodizing shows promise of greater stability in LEO over long missions, such as the 30 years planned for the Space Station. However, sulfuric acid anodizing shows lower solar absorptivity

Coexisting Clinpyroxene/Spinel and Amphibole/Spinel Symplectites in Metatroctolites from the Buck Creek Ultramafic Body, North Carolina Blue Ridge, USA

Buck Creek metatroctolites preserve evidence of three stages in the geologic history of the region: a relict igneous stage; a high-pressure, granulite-facies metamorphic stage; and a hydrous alteration stage. During high-pressure granulite-facies metamorphism, adjacent olivine and plagioclase reacted to produce complex coronitic textures. Relict olivine is surrounded by radial, columnar orthopyroxene, and plagioclase is rimmed by fine-grained symplectite composed of separate grains of clinopyroxene/spinel, tschermakitic amphibole/spinel symplectite and minor clinopyroxene/sapphirine symplectite. Examination of textural relationships in back-scattered electron images and X-ray element maps of the symplectites demonstrates that amphibole/spinel and clinopyroxene/spinel symplectites grew simultaneously at high temperature to replace plagioclase in these rocks. Clinopyroxene/sapphirine symplectite grew in the latest stages of plagioclase replacement in some samples. A successful model for the main corona-forming reaction in sample BC7, 1.00 Pl + 1.72 Ol + 0.17 H2O = 0.59 Di + 0.17 Amp + 0.68 Spl + 0.79 Opx, results only if amphibole is included. The model predicts relative volumes of product clinopyroxene, amphibole and spinel that are generally consistent with the proportions in imaged symplectites. Proportions of clinopyroxene-and amphibole-hosted symplectite appear to have been governed by local mass-balance of Na and Al in plagioclase and/or availability of H2O. The most successful model for formation of the inner clinopyroxene/sapphirine corona, 1.00 Pl + 1.47 Ol + 0.17 H2O = 0.59 Di + 0.17 Amp + 0.30 Spr (10 ox.) + 0.57 Opx, also includes amphibole, which is present in association with clinopyroxene/sapphirine symplectite. Sufficient H2O for formation of symplectic amphibole must have been present in the intergranular fluid of relict igneous troctolites or have infiltrated during metamorphism at high P-T conditions

Evaluation of phenotypic markers associated with pathogenicity in the genus Listeria Avaliação de marcadores fenotípicos associados à patogenicidade no gênero Listeria

A total of 130 Listeria strains were tested in order to evaluate lecithinase production and capacity for Congo red adsorption as markers of pathogenicity. The strains were identified according to acid production from sugars and by the CAMP test and the data were correlated with the ability to produce keratoconjunctivitis in guinea pigs. L. monocytogenes cultures presented 51.8% and 88.8% positivity rates for Congo red adsorption and lecithinase production, respectively, whereas 80.8% and 100% for L. innocua cultures were negative for the two test, respectively<br>Com propósito de avaliar a produção de lecitinase e a capacidade de adsorção do corante vermelho Congo como marcadores de patogenicidade, foram estudadas 130 amostras de Listeria. Estas amostras foram identificadas segundo a produção de ácido a partir de açúcares aliada ao teste CAMP, correlacionando-se estes dados à capacidade de produção de ceratoconjuntivite em cobaio. As culturas de L. monocytogenes apresentaram taxas de positividade para a adsorção do corante e produção de lecitinase de 51,8 e 88,8%, respectivamente, enquanto 80,8% e 100% das culturas de L. innocua foram negativas para os referidos testes