6,061 research outputs found
Estratégias de manejo e alimentação visando a melhoria da pecuária leiteira familiar das regiões Sul e Centro-Sul Fluminense.
bitstream/item/132474/1/Livro-Estrategias-de-manejo-e-alimentacao-visando-a-melhoria-pecuaria.pdfAutores e editores: Alberto Duran Cabrera; Alessandro Torres Campos; Aloísio Torres de Campos; Alziro Vasconcelos Carneiro; Carla Aparecida Florentino Rodrigues; Emílio Pereira Brito Neto; João Ricardo de Souza Martins; John Furlong; Jorge Ronaldo Corrêa Machado; José Nestor de Souza; Márcia Cristina de Azevedo Prata; Márcio Roberto Silva; Nivaldo Micheti; Octaviano Alves Pereira Neto; Paulo Márcio Mundim; Rodolpho de Almeida Torres; Rui da Silva Verneque; Vânia Maria de Oliveira
Asymptotically Matched Spacetime Metric for Non-Precessing, Spinning Black Hole Binaries
We construct a closed-form, fully analytical 4-metric that approximately
represents the spacetime evolution of non-precessing, spinning black hole
binaries from infinite separations up to a few orbits prior to merger. We
employ the technique of asymptotic matching to join a perturbed Kerr metric in
the neighborhood of each spinning black hole to a near-zone, post-Newtonian
metric farther out. The latter is already naturally matched to a far-zone,
post-Minkowskian metric that accounts for full temporal retardation. The result
is a 4-metric that is approximately valid everywhere in space and in a small
bundle of spatial hypersurfaces. We here restrict our attention to quasi-
circular orbits, but the method is valid for any orbital motion or physical
scenario, provided an overlapping region of validity or buffer zone exists. A
simple extension of such a metric will allow for future studies of the
accretion disk and jet dynamics around spinning back hole binaries
Power-Law Sensitivity to Initial Conditions within a Logistic-like Family of Maps: Fractality and Nonextensivity
Power-law sensitivity to initial conditions, characterizing the behaviour of
dynamical systems at their critical points (where the standard Liapunov
exponent vanishes), is studied in connection with the family of nonlinear 1D
logistic-like maps The main ingredient of our approach is the generalized deviation
law \lim_{\Delta x(0) -> 0} \Delta x(t) / \Delta x(0)} = [1+(1-q)\lambda_q
t]^{1/(1-q)} (equal to for q=1, and proportional, for large
t, to for is the entropic index appearing in
the recently introduced nonextensive generalized statistics). The relation
between the parameter q and the fractal dimension d_f of the onset-to-chaos
attractor is revealed: q appears to monotonically decrease from 1
(Boltzmann-Gibbs, extensive, limit) to -infinity when d_f varies from 1
(nonfractal, ergodic-like, limit) to zero.Comment: LaTeX, 6 pages , 5 figure
Thermodynamic Description of the Relaxation of Two-Dimensional Euler Turbulence Using Tsallis Statistics
Euler turbulence has been experimentally observed to relax to a
metaequilibrium state that does not maximize the Boltzmann entropy, but rather
seems to minimize enstrophy. We show that a recent generalization of
thermodynamics and statistics due to Tsallis is capable of explaining this
phenomenon in a natural way. The maximization of the generalized entropy
for this system leads to precisely the same profiles predicted by the
Restricted Minimum Enstrophy theory of Huang and Driscoll. This makes possible
the construction of a comprehensive thermodynamic description of Euler
turbulence.Comment: 15 pages, RevTe
Measurement of the production of the four-fermion final states mediated by neutral current processes
Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP
An experimental study of the normalized three-jet rate of b quark events with
respect to light quarks events (light= \ell \equiv u,d,s) has been performed
using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by
the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are
found to agree with theoretical predictions treating mass corrections at
next-to-leading order. Measurements of the b quark mass have also been
performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data
are found to be better described when using the running mass. The measurement
yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12
(theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise
measurement of the b mass derived from a high energy process. When compared to
other b mass determinations by experiments at lower energy scales, this value
agrees with the prediction of Quantum Chromodynamics for the energy evolution
of the running mass. The mass measurement is equivalent to a test of the
flavour independence of the strong coupling constant with an accuracy of 7
permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.
Study of Leading Hadrons in Gluon and Quark Fragmentation
The study of quark jets in e+e- reactions at LEP has demonstrated that the
hadronisation process is reproduced well by the Lund string model. However, our
understanding of gluon fragmentation is less complete. In this study enriched
quark and gluon jet samples of different purities are selected in three-jet
events from hadronic decays of the Z collected by the DELPHI experiment in the
LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are
defined by requiring a rapidity gap and their sum of charges is studied. An
excess of leading systems with total charge zero is found for gluon jets in all
cases, when compared to Monte Carlo Simulations with JETSET (with and without
Bose-Einstein correlations included) and ARIADNE. The corresponding leading
systems of quark jets do not exhibit such an excess. The influence of the gap
size and of the gluon purity on the effect is studied and a concentration of
the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is
observed, indicating that gluon jets might have an additional hitherto
undetected fragmentation mode via a two-gluon system. This could be an
indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.
Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance
This paper presents DELPHI measurements and interpretations of
cross-sections, forward-backward asymmetries, and angular distributions, for
the e+e- -> ffbar process for centre-of-mass energies above the Z resonance,
from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are
consistent with the predictions of the Standard Model and are used to study a
variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering
and several models which include physics beyond the Standard Model: the
exchange of Z' bosons, contact interactions between fermions, the exchange of
gravitons in large extra dimensions and the exchange of sneutrino in R-parity
violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.
A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events
Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the
Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy
and momentum constraint methods. The results are expressed as deviations from
the nominal LEP centre-of-mass energy, measured using other techniques. The
results are found to be compatible with the LEP Energy Working Group estimates
for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.
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