Upper bound for the conductivity of nanotube networks

Films composed of nanotube networks have their conductivities regulated by the junction resistances formed between tubes. Conductivity values are enhanced by lower junction resistances but should reach a maximum that is limited by the network morphology. By considering ideal ballistic-like contacts between nanotubes we use the Kubo formalism to calculate the upper bound for the conductivity of such films and show how it depends on the nanotube concentration as well as on their aspect ratio. Highest measured conductivities reported so far are approaching this limiting value, suggesting that further progress lies with nanowires other than nanotubes.Comment: 3 pages, 1 figure. Minor changes. Accepted for publication in Applied Physics Letter

Produção de alpínia em cultivo protegido na região litorânea do estado do Ceará.

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Manejo da malformação vegetativa e floral - embonecamento (Fusarium subglutinans) na produção integrada de manga.

O Programa de Produção Integrada de Frutas proporciona maior segurança de cultivo, garantia de maiores produções ou de menores perdas de frutos por doenças e maior sanidade na pós-colheita. Esta garantia é possibilitada pela prática de monitoramento fitossanitário que visa prever e controlar o início do problema em toda a cadeia produtiva.bitstream/CPATSA/33058/1/INT66.pd

Alfvenic Heating of Protostellar Accretion Disks

We investigate the effects of heating generated by damping of Alfven waves on protostellar accretion disks. Two mechanisms of damping are investigated, nonlinear and turbulent, which were previously studied in stellar winds (Jatenco-Pereira & Opher 1989a, b). For the nominal values studied, f=delta v/v_{A}=0.002 and F=varpi/Omega_{i}=0.1, where delta v, v_{A} and varpi are the amplitude, velocity and average frequency of the Alfven wave, respectively, and Omega_{i} is the ion cyclotron frequency, we find that viscous heating is more important than Alfven heating for small radii. When the radius is greater than 0.5 AU, Alfvenic heating is more important than viscous heating. Thus, even for the relatively small value of f=0.002, Alfvenic heating can be an important source of energy for ionizing protostellar disks, enabling angular momentum transport to occur by the Balbus-Hawley instability.Comment: 21 pages, 9 figures. Accepted for publication in Ap

Gravitational Collapse of a Massless Scalar Field and a Perfect Fluid with Self-Similarity of the First Kind in (2+1) Dimensions

Self-similar solutions of a collapsing perfect fluid and a massless scalar field with kinematic self-similarity of the first kind in 2+1 dimensions are obtained. Their local and global properties of the solutions are studied. It is found that some of them represent gravitational collapse, in which black holes are always formed, and some may be interpreted as representing cosmological models.Comment: 13 page

Estudo de desbaste em Pinus taeda L.

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Answer to photo quiz: Tunga penetrans

For both patients, considering the characteristics of the lesions, the epidemiological history of travel, and the microscopic study, a diagnosis of tungiasis was made. Tunga penetrans (sand flea) is a hematophagous flea 1 mm in length, whose habitat is warm, dry, sandy soils. This flea is widely distributed in parts of East and West Africa, South America, and the Caribbean and in countries bordering the Indian Ocean. This flea presents a wide range of wild and domestic hosts, humans being an accidental host. Occasionally, tourists from developed countries are diagnosed with tungiais after becoming infected in areas where the disease is endemic...