27,446 research outputs found
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.
bitstream/item/33803/1/Ct-137.pd
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.
bitstream/item/101258/1/PA-1983-Pereira-estudoDesbaste.pd
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...
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