Uptake of gases in bundles of carbon nanotubes

Model calculations are presented which predict whether or not an arbitrary gas experiences significant absorption within carbon nanotubes and/or bundles of nanotubes. The potentials used in these calculations assume a conventional form, based on a sum of two-body interactions with individual carbon atoms; the latter employ energy and distance parameters which are derived from empirical combining rules. The results confirm intuitive expectation that small atoms and molecules are absorbed within both the interstitial channels and the tubes, while large atoms and molecules are absorbed almost exclusively within the tubes.Comment: 9 pages, 12 figures, submitted to PRB Newer version (8MAR2K). There was an error in the old one (23JAN2K). Please download thi

Origin and Evolution of Saturn's Ring System

The origin and long-term evolution of Saturn's rings is still an unsolved problem in modern planetary science. In this chapter we review the current state of our knowledge on this long-standing question for the main rings (A, Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During the Voyager era, models of evolutionary processes affecting the rings on long time scales (erosion, viscous spreading, accretion, ballistic transport, etc.) had suggested that Saturn's rings are not older than 100 My. In addition, Saturn's large system of diffuse rings has been thought to be the result of material loss from one or more of Saturn's satellites. In the Cassini era, high spatial and spectral resolution data have allowed progress to be made on some of these questions. Discoveries such as the ''propellers'' in the A ring, the shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume provide new constraints on evolutionary processes in Saturn's rings. At the same time, advances in numerical simulations over the last 20 years have opened the way to realistic models of the rings's fine scale structure, and progress in our understanding of the formation of the Solar System provides a better-defined historical context in which to understand ring formation. All these elements have important implications for the origin and long-term evolution of Saturn's rings. They strengthen the idea that Saturn's rings are very dynamical and rapidly evolving, while new arguments suggest that the rings could be older than previously believed, provided that they are regularly renewed. Key evolutionary processes, timescales and possible scenarios for the rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009) 537-57

Deliberação online em consultas públicas? O caso da assembleia legislativa de Minas Gerais

Este artigo busca analisar uma consulta pública online sobre reforma política promovida em 2011 pela Assembleia Legislativa de Minas Gerais. Embasado pela teoria deliberacionista, o estudo de 752 posts guiou-se pela discussão de seis tópicos: (1) inclusividade; (2) provimento de razões; (3) reciprocidade; (4) respeito mútuo; (5) orientação para o bem comum; e (6) articulação entre arenas. Os resultados indicam: (1) uma sobrerepresentação de participantes masculinos e oriundos da Região Metropolitana de Belo Horizonte, embora não tenha havido concentração de posts em alguns comentadores; (2) o predomínio de posts on topic e que apresentam justificativas para as posições advogadas; (3) índices muito baixos de reciprocidade entre posts e de uso de marcadores de interatividade; (4) graus muito elevados de respeito; (5) diferentes formas de ligação das justificativas a ideias de bem comum; (6) o baixo impacto decisório e a conexão com outras arenas da esfera pública, destacando-se a relação com uma matéria publicada em jornal de grande circulação. Os achados são ambivalentes para os defensores da deliberação, indicando baixa probabilidade de deliberação interna ao fórum, mas algum potencial deliberativo quando se adotam lentes mais amplas. Os cruzamentos entre variáveis sugerem que as pessoas tendem a prover mais justificativas em discussões mais controversas, embora tendam a dialogar menos nesses casos. Assim, a hipótese da preferência por conversas entre like-minded encontra respaldo nos dados analisados

Epsilonproteobacteria in Humans, New Zealand

Using PCR–denaturing gradient gel electrophoresis, we examined 49 fecal samples from healthy volunteers and 128 diarrhea specimens to assess the distribution of Epsilonproteobacteria that might be routinely overlooked. Our results suggest that certain taxa that are not routinely examined for could account for a proportion of diarrhea of previously unknown etiology

First report of citrus tristeza virus in Lao PDR

Citrus tristeza virus was detected for the first time in the Lao People’s Democratic Republic. Samples were collected from citrus trees across the southern provinces for testing in Australia. RNA was extracted and tested using conventional and real-time reverse transcription polymerase chain reactions with the virus detected in 12 of 59 samples tested. Viral identities were confirmed by sequencing. Additional confirmation was obtained by an enzyme-linked immunosorbent assay. The implications of the presence of this virus for citrus production in Lao are discussed briefly

First report of apple stem grooving virus in Lao PDR, detected in citrus

Apple stem grooving virus, the causal agent of citrus tatterleaf disease, was detected for the first time in the Lao People’s Democratic Republic. Samples were collected from citrus trees across the southern provinces for testing in Australia. RNA was extracted and tested using conventional and real-time reverse transcription polymerase chain reactions with the virus detected in 1 of 59 samples tested. Viral identity was confirmed by Sanger sequencing and high throughput sequencing