Studies on the reaction of the 5 prime -phosphorimidazolide of adenosine with Cu(II)-exchanged hectorite

The role of clay minerals in the prebiotic synthesis of nucleotide oligomers has received considerable attention in recent years. Scanning force microscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry are used to identify oligomers of adenylic acid formed on the clay mineral Cu(II)-exchanged hectorite in simulated prebiotic cycling experiments. Electron-spin resonance and x-ray diffraction data indicate that the monomer (5 prime -phosphorimidazolide of adenosine, or ImpA) penetrates into the intergallery regions of the mineral substrate, and complexes the gallery Cu(II) cations. It is postulated that polymerization of the monomer is initiated in the clay intergallery regions, producing oligomers of adenylic acid up to 8 units in length or more. 1999 American Institute of Physics

An eddy-correlation measurement of NO2 flux to vegetation and comparison to O3 flux

Eddy-correlation measurements with a newly developed fast-response NOx sensor indicate that the deposition velocity at a height of about 6m above a soybean field has a maximum value near 0.6cms-1 for NOx and is usually about 2/3 ofthat found for ozone. In these studies, over 90% of the NOx is NO2. The corresponding minimum surface resistance for NOx calculated as the quantity remaining after atmospheric resistances are subtracted is about 1.3 s cm-1, which is larger than expected on the basis of leaf stomatal resistance alone. Emission of NO from sites in the plant canopy and soil where NO2 is deposited and reduced to NO or release of NOx as a result of biological activity may have lessened the downward fluxes of NOx as measured. During windy conditions at night, surface resistances are found to have values of about 15scm-1 for NOx (again, greater than 90% NO2) and 1.8scm-1 for O3, corresponding to deposition velocities of 0.05cms-1 and 0.3cms-1, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24138/1/0000395.pd

THE MELTING AND CASTING OF URANIUM IN SULFIDE CRUCIBLES

Uranium was successfully cast at temperatures as high as 1900 to 2000 deg C in crucibles made from CeS, CeS/sub 1.38/, ThS, ThS/sub 1.75/, and ThU/sub 0.7/S/sub 2/ with the sulfur pickup in all cases less than 0.15 wt.%, in some cases at low temperatures being less than 0.005%. A summary of actual sulfur absorption for different experimental temperatures and crucible types is given. The effect of the molten mixture of U and UBr/sub 3/(Br/U =2) upon some sulfide refractories was investigated. The results indicate that only ThS/sub 2/ and divalent sulfides like ThUS/sub 2/, US, ThS, etc., would withstand the U--UBr/sub 3/ mixture. Uranium may be separated from metal salt mixtures (CaCl/sub 2/, SrBr/ sub 2/, BaI/sub 2/, etc.) by distillation of the salt and fusion of the U in a sulfide crucible. (auth

Geoprocessamento e sensoriamento remoto aplicados à análise de recursos florestais Geoprocessing and remote sensing applied to the analysis of forestal resources

Este trabalho tem como objetivo apresentar uma proposta metodológica para o levantamento e análise dos recursos florestais dos povoamentos naturais e implantados, obtido através da utilização de técnicas de geoprocessamento e sensoriamento remoto e localizados na carta topográfica SH. 22-Y-A, Cachoeira do Sul, RS. Para tal, utilizaram-se imagens de satélites associadas ao sistema de informações geográficas, processadas por técnicas de classificação digital e funções matemáticas. Dessa forma, realizou-se o levantamento e a quantificação das diferentes bases temáticas. As variáveis e bases temáticas foram obtidas através das imagens de satélite, trabalho de campo, carta topográfica e cruzamentos geoespaciais, obtendo o uso da terra, espécie implantada, área ocupada, além da localização dos povoamentos florestais quanto à declividade, tipo de solo, rede hidrográfica e disponibilidade viária. Assim, essas informações permitiram analisar a situação da cobertura florestal da região de estudo, fornecendo subsídios ao gerenciamento dos recursos florestais e a preservação do meio ambiente.<br>This study presents a methodology for survey and analysis of the forestal resources of natural and implanted populating located in the topographic leaf SH.22Y-A, Cachoeira do Sul, RS, (Brazil) by using geoprocessing and remote sensing technics. For this purpose, the Geographic Information Systems, associated to satellite images, processed by digital classification and mathematics&#8217; functions were used. In so doing data gathering and quantification of different thematic bases of the studied area. Variables and thematic bases eere accomplished the satellite images, assessed in the field and topographic maps and the geospacials crossings obtaining the land use, implanted species, taken area, besides the localization of the forest concerning slope, edaphic, hydrographic and road availability. Thus, these information obtained by comparing these variables, made it possible to analyze the forestal cover of the study area, supplying subsidy to the forestal resources management and the environmental preservation