431 research outputs found
AplicaciĂłn de la biologĂa molecular a la detecciĂłn de portadores de fibrosis quĂstica de pĂĄncreas
Extraction of Transcript Diversity from Scientific Literature
Transcript diversity generated by alternative splicing and associated mechanisms contributes heavily to the functional complexity of biological systems. The numerous examples of the mechanisms and functional implications of these events are scattered throughout the scientific literature. Thus, it is crucial to have a tool that can automatically extract the relevant facts and collect them in a knowledge base that can aid the interpretation of data from high-throughput methods. We have developed and applied a composite text-mining method for extracting information on transcript diversity from the entire MEDLINE database in order to create a database of genes with alternative transcripts. It contains information on tissue specificity, number of isoforms, causative mechanisms, functional implications, and experimental methods used for detection. We have mined this resource to identify 959 instances of tissue-specific splicing. Our results in combination with those from EST-based methods suggest that alternative splicing is the preferred mechanism for generating transcript diversity in the nervous system. We provide new annotations for 1,860 genes with the potential for generating transcript diversity. We assign the MeSH term âalternative splicingâ to 1,536 additional abstracts in the MEDLINE database and suggest new MeSH terms for other events. We have successfully extracted information about transcript diversity and semiautomatically generated a database, LSAT, that can provide a quantitative understanding of the mechanisms behind tissue-specific gene expression. LSAT (Literature Support for Alternative Transcripts) is publicly available at http://www.bork.embl.de/LSAT/
Statistical distributions in the folding of elastic structures
The behaviour of elastic structures undergoing large deformations is the
result of the competition between confining conditions, self-avoidance and
elasticity. This combination of multiple phenomena creates a geometrical
frustration that leads to complex fold patterns. By studying the case of a rod
confined isotropically into a disk, we show that the emergence of the
complexity is associated with a well defined underlying statistical measure
that determines the energy distribution of sub-elements,``branches'', of the
rod. This result suggests that branches act as the ``microscopic'' degrees of
freedom laying the foundations for a statistical mechanical theory of this
athermal and amorphous system
ââLozengeââ contour plots in scattering from polymer networks
We present a consistent explanation for the appearance of âlozengeâ shapes in contour plots of the two dimensional scattering intensity from stretched polymer networks. By explicitly averaging over quenched variables in a tube model, we show that lozenge patterns arise as a result of chain material that is not directly deformed by the stretch. We obtain excellent agreement with experimental data
First Order Phase Transition of a Long Polymer Chain
We consider a model consisting of a self-avoiding polygon occupying a
variable density of the sites of a square lattice. A fixed energy is associated
with each -bend of the polygon. We use a grand canonical ensemble,
introducing parameters and to control average density and average
(total) energy of the polygon, and show by Monte Carlo simulation that the
model has a first order, nematic phase transition across a curve in the
- plane.Comment: 11 pages, 7 figure
Temperature suppression of Kelvin-wave turbulence in superfluids
Kelvin waves propagating on quantum vortices play a crucial role in the
phenomenology of energy dissipation of superfluid turbulence. Previous
theoretical studies have consistently focused on the zero-temperature limit of
the statistical physics of Kelvin-wave turbulence. In this letter, we go beyond
this athermal limit by introducing a small but finite temperature in the form
of non-zero mutual friction dissipative force; A situation regularly
encountered in actual experiments of superfluid turbulence. In this case we
show that there exists a new typical length-scale separating a quasi-inertial
range of Kelvin wave turbulence from a far dissipation range. The letter
culminates with analytical predictions for the energy spectrum of the
Kelvin-wave turbulence in both of these regimes
Dissipation in planar resonant planetary systems
Close-in planetary systems detected by the Kepler mission present an excess
of periods ratio that are just slightly larger than some low order resonant
values. This feature occurs naturally when resonant couples undergo dissipation
that damps the eccentricities. However, the resonant angles appear to librate
at the end of the migration process, which is often believed to be an evidence
that the systems remain in resonance.
Here we provide an analytical model for the dissipation in resonant planetary
systems valid for low eccentricities. We confirm that dissipation accounts for
an excess of pairs that lie just aside from the nominal periods ratios, as
observed by the Kepler mission. In addition, by a global analysis of the phase
space of the problem, we demonstrate that these final pairs are non-resonant.
Indeed, the separatrices that exist in the resonant systems disappear with the
dissipation, and remains only a circulation of the orbits around a single
elliptical fixed point. Furthermore, the apparent libration of the resonant
angles can be explained using the classical secular averaging method. We show
that this artifact is only due to the severe damping of the amplitudes of the
eigenmodes in the secular motion.Comment: 18 pages, 20 figures, accepted to A&
Polarization of thick polyvinylidene fluoride/trifluoroethylene copolymer films
Version of RecordPublishe
Anisotropic q-Gaussian velocity distributions in LambdaCDM halos
The velocity distribution function (VDF) of dark matter (DM) halos in
CDM dissipationless cosmological simulations, which must be
non-separable in its radial and tangential components, is still poorly known.
We present the first single-parameter, non-separable, anisotropic model for the
VDF in CDM halos, built from an isotropic -Gaussian (Tsallis) VDF
of the isotropic set of dimensionless spherical velocity components (after
subtraction of streaming motions), normalized by the respective velocity
dispersions. We test our VDF on 90 cluster-mass halos of a dissipationless
cosmological simulation.
Beyond the virial radius, , our model VDF adequately reproduces
that measured in the simulated halos, but no -Gaussian model can adequately
represent the VDF within , as the speed distribution function is
then flatter-topped than any -Gaussian can allow. Nevertheless, our VDF fits
significantly better the simulations than the commonly used Maxwellian
(Gaussian) distribution, at virtually all radii within . Within
0.4 (1) , the non-Gaussianity index is (roughly) linearly
related to the slope of the density profile and also to the velocity anisotropy
profile. We provide a parametrization of the modulation of with radius for
both the median fits and the fit of the stacked halo. At radii of a few percent
of , corresponding to the Solar position in the Milky Way, our
best-fit VDF, although fitting better the simulations than the Gaussian one,
overproduces significantly the fraction of high velocity objects, indicating
that one should not blindly use these -Gaussian fits to make predictions on
the direct detection rate of DM particles.Comment: This version consolidates the published version and the Erratum
(changes in red
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