4,127 research outputs found
A conditional compression distance that unveils insights of the genomic evolution
We describe a compression-based distance for genomic sequences. Instead of
using the usual conjoint information content, as in the classical Normalized
Compression Distance (NCD), it uses the conditional information content. To
compute this Normalized Conditional Compression Distance (NCCD), we need a
normal conditional compressor, that we built using a mixture of static and
dynamic finite-context models. Using this approach, we measured chromosomal
distances between Hominidae primates and also between Muroidea (rat and mouse),
observing several insights of evolution that so far have not been reported in
the literature.Comment: Full version of DCC 2014 paper "A conditional compression distance
that unveils insights of the genomic evolution
Information profiles for DNA pattern discovery
Finite-context modeling is a powerful tool for compressing and hence for
representing DNA sequences. We describe an algorithm to detect genomic
regularities, within a blind discovery strategy. The algorithm uses information
profiles built using suitable combinations of finite-context models. We used
the genome of the fission yeast Schizosaccharomyces pombe strain 972 h- for
illustration, unveilling locations of low information content, which are
usually associated with DNA regions of potential biological interest.Comment: Full version of DCC 2014 paper "Information profiles for DNA pattern
discovery
Gravitational wave background in perfect fluid quantum cosmologies
We discuss the gravitational wave background produced by bouncing models
based on a full quantum evolution of a universe filled with a perfect fluid.
Using an ontological interpretation for the background wave function allows us
to solve the mode equations for the tensorial perturbations, and we find the
spectral index as a function of the fluid equation of state.Comment: 12 pages, 5 figures, to appear in Phys. Rev. D (2006
Updated constraints on spatial variations of the fine-structure constant
Recent work by Webb {\it et al.} has provided indications of spatial
variations of the fine-structure constant, , at a level of a few parts
per million. Using a dataset of 293 archival measurements, they further show
that a dipole provides a statistically good fit to the data, a result
subsequently confirmed by other authors. Here we show that a more recent
dataset of dedicated measurements further constrains these variations: although
there are only 10 such measurements, their uncertainties are considerably
smaller. We find that a dipolar variation is still a good fit to the combined
dataset, but the amplitude of such a dipole must be somewhat smaller:
ppm for the full dataset, versus ppm for the Webb {\it
et al.} data alone, both at the confidence level. Constraints on the
direction on the sky of such a dipole are also significantly improved. On the
other hand the data can't yet discriminate between a pure spatial dipole and
one with an additional redshift dependence.Comment: 10 pages, 4 figure
A new approach on the stability analysis in ELKO cosmology
In this work it has been developed a new approach to study the stability of a
system composed by an ELKO field interacting with dark matter, which could give
some contribution in order to alleviate the cosmic coincidence problem. It is
assumed that the potential which characterizes the ELKO field is not specified,
but it is related to a constant parameter . The strength of the
interaction between matter and ELKO field is characterized by a constant
parameter and it is also assumed that both ELKO field as matter energy
density are related to their pressures by equations of state parameters
and , respectively. The system of equations is analysed
by a dynamical system approach. It has been found the conditions of stability
between the parameters and in order to have stable fixed
points for the system for different values of the equation of state parameters
and , and the results are presented in form of tables.
The possibility of decay of ELKO field into dark matter or vice versa can be
read directly from the tables, since the parameters and
satisfy some inequalities. It allows us to constrain the potential assuming
that we have a stable system for different interactions terms between the ELKO
field and dark matter. The cosmic coincidence problem can be alleviated for
some specific relations between the parameters of the model.Comment: 16 pages, some new comments in the Introduction and at the begining
of Section I
Constraining spatial variations of the fine-structure constant in symmetron models
We introduce a methodology to test models with spatial variations of the
fine-structure constant , based on the calculation of the angular power
spectrum of these measurements. This methodology enables comparisons of
observations and theoretical models through their predictions on the statistics
of the variation. Here we apply it to the case of symmetron models. We
find no indications of deviations from the standard behavior, with current data
providing an upper limit to the strength of the symmetron coupling to gravity
() when this is the only free parameter, and not able to
constrain the model when also the symmetry breaking scale factor is
free to vary.Comment: Phys. Lett. B (in press
Portraits of change by farmers in Southern Guinea-Bissau
This photo essay, whose images and captions were created by farmers living in Cantanhez National Park, Guinea-Bissau, illustrates and analyzes the diverse ways in which these West African photographers and collaborative researchers chose to represent change. Some of the visual and narrative devices employed by the photographers include staging the past; representing before/after situations; and thoughtful composition in the visual depiction of changed and changing physical environments. Beyond our initial research focus on perceptions of climatic changes, these farmers turned photographers shared compelling portrayals of change in its social, economic, ecological and cultural complexity, in some cases offering counter-narratives to the dominant environmentalist narrative about this protected area.info:eu-repo/semantics/publishedVersio
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