109 research outputs found
Exact results for curvature-driven coarsening in two dimensions
We consider the statistics of the areas enclosed by domain boundaries
(`hulls') during the curvature-driven coarsening dynamics of a two-dimensional
nonconserved scalar field from a disordered initial state. We show that the
number of hulls per unit area that enclose an area greater than has, for
large time , the scaling form , demonstrating
the validity of dynamical scaling in this system, where is a
universal constant. Domain areas (regions of aligned spins) have a similar
distribution up to very large values of . Identical forms are
obtained for coarsening from a critical initial state, but with replaced by
.Comment: 4 pages, 4 figure
Geometric properties of two-dimensional coarsening with weak disorder
The domain morphology of weakly disordered ferromagnets, quenched from the
high-temperature phase to the low-temperature phase, is studied using numerical
simulations. We find that the geometrical properties of the coarsening domain
structure, e.g., the distributions of hull enclosed areas and domain perimeter
lengths, are described by a scaling phenomenology in which the growing domain
scale R(t) is the only relevant parameter. Furthermore, the scaling functions
have forms identical to those of the corresponding pure system, extending the
'super-universality' property previously noted for the pair correlation
function.Comment: 6 pages, 6 figure
Curvature-driven coarsening in the two dimensional Potts model
We study the geometric properties of polymixtures after a sudden quench in
temperature. We mimic these systems with the -states Potts model on a square
lattice with and without weak quenched disorder, and their evolution with Monte
Carlo simulations with non-conserved order parameter. We analyze the
distribution of hull enclosed areas for different initial conditions and
compare our results with recent exact and numerical findings for (Ising)
case. Our results demonstrate the memory of the presence or absence of
long-range correlations in the initial state during the coarsening regime and
exhibit super-universality properties.Comment: 12 pages, 16 figure
Kibble-Zurek mechanism and infinitely slow annealing through critical points
We revisit the Kibble-Zurek mechanism by analyzing the dynamics of phase
ordering systems during an infinitely slow annealing across a second order
phase transition. We elucidate the time and cooling rate dependence of the
typical growing length and we use it to predict the number of topological
defects left over in the symmetry broken phase as a function of time, both
close and far from the critical region. Our results extend the Kibble-Zurek
mechanism and reveal its limitations.Comment: 5 pages, 4 fig
A domain categorisation of vocabularies based on a deep learning classifier.
The publication of large amounts of open data has become a major trend nowadays. This is a consequence of pro-jects like the Linked Open Data (LOD) community, which publishes and integrates datasets using techniques like Linked Data. Linked Data publishers should follow a set of principles for dataset design. This information is described in a 2011 document that describes tasks as the consideration of reusing vocabularies. With regard to the latter, another project called Linked Open Vocabularies (LOV) attempts to compile the vocabularies used in LOD. These vocabularies have been classified by domain following the subjective criteria of LOV members, which has the inherent risk introducing personal biases. In this paper, we present an automatic classifier of vocabularies based on the main categories of the well-known knowledge source Wikipedia. For this purpose, word-embedding models were used, in combination with Deep Learning techniques. Results show that with a hybrid model of regular Deep Neural Network (DNN), Recurrent Neural Network (RNN) and Convolutional Neural Network (CNN), vocabularies could be classified with an accuracy of 93.57 per cent. Specifically, 36.25 per cent of the vocabularies belong to the Culture category.pre-print304 K
On the graph structure of the Web of Data
This article describes how the Web of Data has emerged as the realization of a machine readable web relying on the resource description framework language as a way to provide richer semantics to datasets. While the web of data is based on similar principles as the original web, being interlinked in the principal mechanism to relate information, the differences in the structure of the information is evident. Several studies have analysed the graph structure of the web, yielding important insights that were used in relevant applications. However, those findings cannot be transposed to the Web of Data, due to fundamental differences in the production, link creation and usage. This article reports on a study of the graph structure of the Web of Data using methods and techniques from similar studies for the Web. Results show that the Web of Data also complies with the theory of the bow-tie. Other characteristics are the low distance between nodes or the closeness and degree centrality are low. Regarding the datasets, the biggest one is Open Data Euskadi but the one with more connections to other datasets is Dbpedia.European Commissio
Geometry of phase separation
We study the domain geometry during spinodal decomposition of a 50:50 binary
mixture in two dimensions. Extending arguments developed to treat non-conserved
coarsening, we obtain approximate analytic results for the distribution of
domain areas and perimeters during the dynamics. The main approximation is to
regard the interfaces separating domains as moving independently. While this is
true in the non-conserved case, it is not in the conserved one. Our results can
therefore be considered as a first-order approximation for the distributions.
In contrast to the celebrated Lifshitz-Slyozov-Wagner distribution of
structures of the minority phase in the limit of very small concentration, the
distribution of domain areas in the 50:50 case does not have a cut-off. Large
structures (areas or perimeters) retain the morphology of a percolative or
critical initial condition, for quenches from high temperatures or the critical
point respectively. The corresponding distributions are described by a tail, where and are exactly known. With increasing time,
small structures tend to have a spherical shape with a smooth surface before
evaporating by diffusion. In this regime the number density of domains with
area scales as , as in the Lifshitz-Slyozov-Wagner theory. The
threshold between the small and large regimes is determined by the
characteristic area, . Finally, we study the
relation between perimeters and areas and the distribution of boundary lengths,
finding results that are consistent with the ones summarized above. We test our
predictions with Monte Carlo simulations of the 2d Ising Model.Comment: 10 pages, 8 figure
Combining VIVO and Google Scholar data as sources for CERIF linked data: a case in the agricultural domain
The needs of global science have fostered open access to the results and contextual information of research organizations at an international scale. This requires the use of standards or shared data models to exchange information preserving its semantics when transferred between systems. In that direction, standards as CERIF or projects as VIVO were developed to exchange or expose the scientific knowledge. Also, there are other sources of scientific information in the Web that are useful to complement institutional repositories and CRISes. The heterogeneity of data models behind each source in turn raises the need for mappings between them to ease interchange and aggregate information. In this paper, we present a tool that integrates three sources of research information and enables their aggregating and export into both VIVO and CERIF models. We present a case study in agriculture using OpenAGRIS, a bibliographic database linked to Web sources with more than 7 million records. Concretely, we describe the methods to combine Google Scholar data for the scholarly content indexed in OpenAGRIS and aggregating new information provided by the first one, using our tool. Finally the information is stored in a VIVO instance and then translated into CERIF using a conversion process mapping both data models. The case demonstrates the possibilities of mapping tools to aggregate and translate CRIS information
Can BODIPY Dimers Act as Photosensitizers in Photodynamic Therapy? A Theoretical Prediction
The photophysical properties of some monomeric and dimeric BODIPY systems were investigated at the density functional theory level and herein reported. In particular, the absorption spectra were fully characterized, low energy singlet and triplet excited states were discussed also focusing on the energy difference gaps between them and computing the spin-orbit couplings values for the possible intersystem crossing channels. The heavy atom effect of iodine substituents on the photophysical properties of a monomer and on a dimer under investigation was also estimated. Results obtained on the considered compounds allow us to predict which is the most promising candidate to be suggested as a photosensitizer in photodynamic therapy
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