3,088 research outputs found
Caracterização das celulases produzidas pelos fungos Pleorotus ostreatus e Pleorotus eryngii por fermentação da palha do sorgo forrageiro.
Testing feasibility of scalar-tensor gravity by scale dependent mass and coupling to matter
We investigate whether there are any cosmological evidences for a scalar
field with a mass and coupling to matter which change accordingly to the
properties of the astrophysical system it "lives in", without directly focusing
on the underlying mechanism that drives the scalar field scale-dependent
properties. We assume a Yukawa type of coupling between the field and matter
and also that the scalar field mass grows with density, in order to overcome
all gravity constraints within the solar system. We analyse three different
gravitational systems assumed as "cosmological indicators": supernovae type Ia,
low surface brightness spiral galaxies and clusters of galaxies. Results show
that: a) a quite good fit to the rotation curves of low surface brightness
galaxies only using visible stellar and gas mass components is obtained; b) a
scalar field can fairly well reproduce the matter profile in clusters of
galaxies, estimated by X-ray observations and without the need of any
additional dark matter; c) there is an intrinsic difficulty in extracting
information about the possibility of a scale-dependent massive scalar field (or
more generally about a varying gravitational constant) from supernovae type Ia.Comment: 30 pages, 15 figures, to appear in Phys. Rev.
Effective interactions and large-scale diagonalization for quantum dots
The widely used large-scale diagonalization method using harmonic oscillator
basis functions (an instance of the Rayleigh-Ritz method, also called a
spectral method, configuration-interaction method, or ``exact diagonalization''
method) is systematically analyzed using results for the convergence of Hermite
function series. We apply this theory to a Hamiltonian for a one-dimensional
model of a quantum dot. The method is shown to converge slowly, and the
non-smooth character of the interaction potential is identified as the main
problem with the chosen basis, while on the other hand its important advantages
are pointed out. An effective interaction obtained by a similarity
transformation is proposed for improving the convergence of the diagonalization
scheme, and numerical experiments are performed to demonstrate the improvement.
Generalizations to more particles and dimensions are discussed.Comment: 7 figures, submitted to Physical Review B Single reference error
fixe
A Method to Tackle First Order Differential Equations with Liouvillian Functions in the Solution - II
We present a semi-decision procedure to tackle first order differential
equations, with Liouvillian functions in the solution (LFOODEs). As in the case
of the Prelle-Singer procedure, this method is based on the knowledge of the
integrating factor structure.Comment: 11 pages, late
Use of sorghum straw (sorghum bicolor) for second generation ethanol production: pretreatment and enzymatic hydrolysis.
Agronomic biomass yields of forage sorghum BRS 655 presented similar results to other energy crops, producing 9 to 12.6 tons/ha (dry mass) of sorghum straw. The objective of this study was to evaluate the lignocellulosic part of this cultivar in terms of its potential in the different unit processes in the production of cellulosic ethanol, measuring the effects of pretreatment and enzymatic hydrolysis. Three types of pre-treatments for two reaction times were conducted to evaluate the characteristics of the pulp for subsequent saccharification. The pulp pretreated by alkali, and by acid followed by delignification, attained hydrolysis rates of over 90%
The present universe in the Einstein frame, metric-affine R+1/R gravity
We study the present, flat isotropic universe in 1/R-modified gravity. We use
the Palatini (metric-affine) variational principle and the Einstein
(metric-compatible connected) conformal frame. We show that the energy density
scaling deviates from the usual scaling for nonrelativistic matter, and the
largest deviation occurs in the present epoch. We find that the current
deceleration parameter derived from the apparent matter density parameter is
consistent with observations. There is also a small overlap between the
predicted and observed values for the redshift derivative of the deceleration
parameter. The predicted redshift of the deceleration-to-acceleration
transition agrees with that in the \Lambda-CDM model but it is larger than the
value estimated from SNIa observations.Comment: 11 pages; published versio
Improving the Global Fitting Method on Non-Linear Time Series Analysis
In this paper, we are concerned with improving the forecast capabilities of
the Global approach to Time Series. We assume that the normal techniques of
Global mapping are applied, the noise reduction is performed, etc. Then, using
the mathematical foundations behind such approaches, we propose a method that,
without a great computational cost, greatly increase the accuracy of the
corresponding forecasting
Corynebacterium pseudotuberculosis experimental infection of gioats mamary gland.
Objetivou-se com este trabalho descrever alguns aspectos da patogenia da infecção da glândula mamária por Corynebacterium pseudotuberculosis isolado de um caso natural de linfadenite caseosa. Os animais em número de seis, foram separados em dois grupos, no primeiro (GI) foi realizada inoculação da cepa de C. pseudotuberculosis pela via intradérmica e no segundo grupo (GII) pela via intramamária. Esses animais foram acompanhados diariamente por exame clÃnico e por hemogramas em diferentes tempos. Apenas dois animais do GII apresentaram alteração ao exame clÃnico caracterizada por hipertermia. Todos os animais (GI e GII) apresentaram pápula e edema no local da inoculação. No eritrograma, não foram observadas alterações significativas, contudo no leucograma, observou-se leucocitose por neutrofilia em dois animais do GII. A análise da celularidade das glândulas demonstrou que apenas dois animais do GII apresentaram mastite aguda. Comprovou-se com este experimento que o C. pseudotuberculosis isolado de infecção natural de linfadenite caseosa, pode ocasionar mastite clÃnica, causando prejuÃzos para caprinocultura, assim como a citologia de expressão pode ser utilizada como método de diagnóstico alternativo nos casos de mastite
Diffusive conductors as Andreev interferometers
We present a novel mechanism of phase-dependent electric transport in
diffusive normal metal-superconductor structures. We provide a detailed
theoretical and numerical analysis of recent unexplained experiments
essentially explaining them.Comment: Self extracting file, 7 pages latex and 4 postscript figures. The
paper is also available at http://www.tn.tudelft.nl/tn/thspap.html In this
revision we resolved some printing problems concerning figures 2 and
Dynamics of the self-interacting chameleon cosmology
In this article we study the properties of the flat FRW chameleon cosmology
in which the cosmic expansion of the Universe is affected by the chameleon
field and dark energy. In particular, we perform a detailed examination of the
model in the light of numerical analysis. The results illustrate that the
interacting chameleon filed plays an important role in late time universe
acceleration and phantom crossing.Comment: 13 pages, 8 figures, to appear in Astrophysics and Space Sc
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