13,206 research outputs found
Dinâmica de características físicas e químicas de solos em diferentes sistemas de manejo/uso da terra em áreas de pequenos produtores.
Caracterização química dos solos e a dinâmica dessas características em diferentes sistemas de manejo/uso da terra em áreas de pequenos produtores.
Caracterização morfológica, física e química dos solos e a dinâmica dessas características em diferentes sistemas de manejo e uso da terra em áreas de pequenos produtores.
Mutual information in random Boolean models of regulatory networks
The amount of mutual information contained in time series of two elements
gives a measure of how well their activities are coordinated. In a large,
complex network of interacting elements, such as a genetic regulatory network
within a cell, the average of the mutual information over all pairs is a
global measure of how well the system can coordinate its internal dynamics. We
study this average pairwise mutual information in random Boolean networks
(RBNs) as a function of the distribution of Boolean rules implemented at each
element, assuming that the links in the network are randomly placed. Efficient
numerical methods for calculating show that as the number of network nodes
N approaches infinity, the quantity N exhibits a discontinuity at parameter
values corresponding to critical RBNs. For finite systems it peaks near the
critical value, but slightly in the disordered regime for typical parameter
variations. The source of high values of N is the indirect correlations
between pairs of elements from different long chains with a common starting
point. The contribution from pairs that are directly linked approaches zero for
critical networks and peaks deep in the disordered regime.Comment: 11 pages, 6 figures; Minor revisions for clarity and figure format,
one reference adde
Dynamical analysis of the cluster pair: A3407 + A3408
We carried out a dynamical study of the galaxy cluster pair A3407 \& A3408
based on a spectroscopic survey obtained with the 4 meter Blanco telescope at
the CTIO, plus 6dF data, and ROSAT All-Sky-Survey. The sample consists of 122
member galaxies brighter than . Our main goal is to probe the galaxy
dynamics in this field and verify if the sample constitutes a single galaxy
system or corresponds to an ongoing merging process. Statistical tests were
applied to clusters members showing that both the composite system A3407 +
A3408 as well as each individual cluster have Gaussian velocity distribution. A
velocity gradient of was identified around
the principal axis of the projected distribution of galaxies, indicating that
the global field may be rotating. Applying the KMM algorithm to the
distribution of galaxies we found that the solution with two clusters is better
than the single unit solution at the 99\% c.l. This is consistent with the
X-ray distribution around this field, which shows no common X-ray halo
involving A3407 and A3408. We also estimated virial masses and applied a
two-body model to probe the dynamics of the pair. The more likely scenario is
that in which the pair is gravitationally bound and probably experiences a
collapse phase, with the cluster cores crossing in less than 1
Gyr, a pre-merger scenario. The complex X-ray morphology, the gas temperature,
and some signs of galaxy evolution in A3408 suggests a post-merger scenario,
with cores having crossed each other Gyr ago, as an
alternative solution.Comment: 17 pages, 12 figures, submitted to MNRAS, accepted 2016 May 9.
Received 2016 May 9; in original form 2016 April 1
Demonstration of the Complementarity of One- and Two-Photon Interference
The visibilities of second-order (single-photon) and fourth-order
(two-photon) interference have been observed in a Young's double-slit
experiment using light generated by spontaneous parametric down-conversion and
a photon-counting intensified CCD camera. Coherence and entanglement underlie
one-and two-photon interference, respectively. As the effective source size is
increased, coherence is diminished while entanglement is enhanced, so that the
visibility of single-photon interference decreases while that of two-photon
interference increases. This is the first experimental demonstration of the
complementarity between single- and two-photon interference (coherence and
entanglement) in the spatial domain.Comment: 21 pages, 7 figure
Produção de frutos de inajazeiro (Maximiliana maripa (aubl) Drude) na região do Pacuí e Cutias do Araguari.
Avaliação da produção de sementes secas de inajazeiros (Maximiliana maripa (aubl) Drude) na região do Pacuí e Cutias do Araguari no Estado do Amapá.
The Apparent Fractal Conjecture: Scaling Features in Standard Cosmologies
This paper presents an analysis of the smoothness problem in cosmology by
focussing on the ambiguities originated in the simplifying hypotheses aimed at
observationally verifying if the large-scale distribution of galaxies is
homogeneous, and conjecturing that this distribution should follow a fractal
pattern in perturbed standard cosmologies. This is due to a geometrical effect,
appearing when certain types of average densities are calculated along the past
light cone. The paper starts reviewing the argument concerning the possibility
that the galaxy distribution follows such a scaling pattern, and the premises
behind the assumption that the spatial homogeneity of standard cosmology can be
observable. Next, it is argued that to discuss observable homogeneity one needs
to make a clear distinction between local and average relativistic densities,
and showing how the different distance definitions strongly affect them,
leading the various average densities to display asymptotically opposite
behaviours. Then the paper revisits Ribeiro's (1995: astro-ph/9910145) results,
showing that in a fully relativistic treatment some observational average
densities of the flat Friedmann model are not well defined at z ~ 0.1, implying
that at this range average densities behave in a fundamentally different manner
as compared to the linearity of the Hubble law, well valid for z < 1. This
conclusion brings into question the widespread assumption that relativistic
corrections can always be neglected at low z. It is also shown how some key
features of fractal cosmologies can be found in the Friedmann models. In view
of those findings, it is suggested that the so-called contradiction between the
cosmological principle, and the galaxy distribution forming an unlimited
fractal structure, may not exist.Comment: 30 pages, 2 figures, LaTeX. This paper is a follow-up to
gr-qc/9909093. Accepted for publication in "General Relativity and
Gravitation
Adequação do leite produzido no Rio Grande do Sul à instrução normativa 51 do MAPA.
bitstream/item/31104/1/COMUNICADO-143.pd
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