8,041 research outputs found
Caracterização do óleo de pinhão-manso (Jatropha curcas L.).
O pinhão manso (Jatropha curcas L.), pertencente a familia Euphorbiaceae, e uma planta nativa da America tropical, naturalizada em partes tropicais e subtropicais da Africa e Asia. Sua distribuição geografica e bastante vasta devido a sua rusticidade, resistencia a longas estiagens, bem como a pragas e doencas, sendo adaptavel a condicoes edafoclimaticas muito variaveis. O fruto de J.curcas contem oleo viscoso que pode ser usado na industria de cosmeticos, como substituto do querosene, e na fabricacao de sabao e combustivel para motores diesel. Este trabalho tem como objetivo caracterizar o oleo de pinhao manso segundo sua composicao quimica e parâmetros fisico-quimicos, tendo em vista sua utilizacao para a producao de biocombustivel..
Ecologia microbiana do solo.
Fatores abióticos que afetam os microrganismos; Temperatura do solo; pH do solo; Fontes de energia e substratos orgânicos; Nutrientes minerais; Práticas de manejo e cultivo dos solos; Interação entre microrganismos; Interações microbianas de importância para a produção agrícola.bitstream/item/35904/1/Doc164.pd
Temperature oscillations of magnetization observed in nanofluid ferromagnetic graphite
We report on unusual magnetic properties observed in the nanofluid
room-temperature ferromagnetic graphite (with an average particle size of
l=10nm). More precisely, the measured magnetization exhibits a low-temperature
anomaly (attributed to manifestation of finite size effects below the quantum
temperature) as well as pronounced temperature oscillations above T=50K
(attributed to manifestation of the hard-sphere type pair correlations between
ferromagnetic particles in the nanofluid)
Árvores e arbustos do sistema agrossilvipastoril caprinos e ovinos.
bitstream/item/29100/1/UMT-Doc-96.pd
Screening effects in flow through rough channels
A surprising similarity is found between the distribution of hydrodynamic
stress on the wall of an irregular channel and the distribution of flux from a
purely Laplacian field on the same geometry. This finding is a direct outcome
from numerical simulations of the Navier-Stokes equations for flow at low
Reynolds numbers in two-dimensional channels with rough walls presenting either
deterministic or random self-similar geometries. For high Reynolds numbers,
when inertial effects become relevant, the distribution of wall stresses on
deterministic and random fractal rough channels becomes substantially dependent
on the microscopic details of the walls geometry. In addition, we find that,
while the permeability of the random channel follows the usual decrease with
Reynolds, our results indicate an unexpected permeability increase for the
deterministic case, i.e., ``the rougher the better''. We show that this complex
behavior is closely related with the presence and relative intensity of
recirculation zones in the reentrant regions of the rough channel.Comment: 4 pages, 5 figure
Invasion Percolation Between two Sites
We investigate the process of invasion percolation between two sites
(injection and extraction sites) separated by a distance r in two-dimensional
lattices of size L. Our results for the non-trapping invasion percolation model
indicate that the statistics of the mass of invaded clusters is significantly
dependent on the local occupation probability (pressure) Pe at the extraction
site. For Pe=0, we show that the mass distribution of invaded clusters P(M)
follows a power-law P(M) ~ M^{-\alpha} for intermediate values of the mass M,
with an exponent \alpha=1.39. When the local pressure is set to Pe=Pc, where Pc
corresponds to the site percolation threshold of the lattice topology, the
distribution P(M) still displays a scaling region, but with an exponent
\alpha=1.02. This last behavior is consistent with previous results for the
cluster statistics in standard percolation. In spite of these discrepancies,
the results of our simulations indicate that the fractal dimension of the
invaded cluster does not depends significantly on the local pressure Pe and it
is consistent with the fractal dimension values reported for standard invasion
percolation. Finally, we perform extensive numerical simulations to determine
the effect of the lattice borders on the statistics of the invaded clusters and
also to characterize the self-organized critical behavior of the invasion
percolation process.Comment: 7 pages, 11 figures, submited for PR
Gravity with extra dimensions and dark matter interpretation: Phenomenological example via Miyamoto-Nagai galaxy
A configuration whose density profile coincides with the Newtonian potential
for spiral galaxies is constructed from a 4D isotropic metric plus extra
dimensional components. A Miyamoto-Nagai ansatz is used to solve Einstein
equations. The stable rotation curves of such system are computed and, without
fitting techniques, we recover with accuracy the observational data for flat or
not asymptotically flat galaxy rotation curves. The density profiles are
reconstructed and compared to that obtained from the Newtonian potential.Comment: 10 pages, 10 figures, submitted to Brazilian Journal of Physic
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