453 research outputs found
Social Network Reciprocity as a Phase Transition in Evolutionary Cooperation
In Evolutionary Dynamics the understanding of cooperative phenomena in
natural and social systems has been the subject of intense research during
decades. We focus attention here on the so-called "Lattice Reciprocity"
mechanisms that enhance evolutionary survival of the cooperative phenotype in
the Prisoner's Dilemma game when the population of darwinian replicators
interact through a fixed network of social contacts. Exact results on a "Dipole
Model" are presented, along with a mean-field analysis as well as results from
extensive numerical Monte Carlo simulations. The theoretical framework used is
that of standard Statistical Mechanics of macroscopic systems, but with no
energy considerations. We illustrate the power of this perspective on social
modeling, by consistently interpreting the onset of lattice reciprocity as a
thermodynamical phase transition that, moreover, cannot be captured by a purely
mean-field approach.Comment: 10 pages. APS styl
Prevalence and distribution of intestinal parasites in stray dogs in the northwest area of Mexico
Zoonotic parasitic infections are a major global public and veterinary health problem and widespread among stray dogs. The objective of this study was to establish the prevalence of intestinal parasites in stray dogs in the urban, rural and coastal areas of Mexicali County in northwest Mexico. In 2014, from January to December, 380 stray dogs were captured. The entire small intestine, cecum and faeces samples were collected and examined by using simple zinc sulfate flotation and Lugol’s solution staining. Data were statistically analysed. Overall, about 21.5% of examined dogs were found positive for intestinal parasites. Toxocara canis was the most frequent detected parasite, with a prevalence of 7.1%, followed by Toxascaris leonina (5.5%), Cystoisospora spp. (5.0%), Taenia spp. (3.9%) and Dipylidium caninum (2.8%). Dogs were more frequently found to be infected with a single genus of intestinal parasite (18.7%) than co-infected (2.8%). Intestinal parasites were more prevalent in samples from the coastal area (25%) than in those from the rural (24.4%) and urban (20.6%) areas, however, only statistical association was found between capture area and specific intestinal parasitic infection. There were significant differences in the prevalence of taeniasis among two age groups (P<0.01). A seasonal peak of prevalence for intestinal parasitic infections was found during spring (P<0.05), corresponding with a seasonal peak of prevalence of T. canis (P<0.05). The wide range of isolated parasites indicated that people residing in this area are at risk of exposure to these potentially hazardous zoonotic pathogens
Problem-based learning supported by semantic techniques
Problem-based learning has been applied over the last three decades to a diverse range of learning environments. In this educational approach, different problems are posed to the learners so that they can develop different solutions while learning about the problem domain. When applied to conceptual modelling, and particularly to Qualitative Reasoning, the solutions to problems are models that represent the behaviour of a dynamic system. The learner?s task then is to bridge the gap between their initial model, as their first attempt to represent the system, and the target models that provide solutions to that problem. We propose the use of semantic technologies and resources to help in bridging that gap by providing links to terminology and formal definitions, and matching techniques to allow learners to benefit from existing models
Relativistic spine jets from Schwarzschild black holes: "Application to AGN radioloud sources"
The two types of Fanaroff-Riley radio loud galaxies, FRI and FRII, exhibit
strong jets but with different properties. These differences may be associated
to the central engine and/or the external medium. Aims: The AGN classification
FRI and FRII can be linked to the rate of electromagnetic Poynting flux
extraction from the inner corona of the central engine by the jet. The
collimation results from the distribution of the total electromagnetic energy
across the jet, as compared to the corresponding distribution of the thermal
and gravitational energies. We use exact solutions of the fully relativistic
magnetohydrodynamical (GRMHD) equations obtained by a nonlinear separation of
the variables to study outflows from a Schwarzschild black hole corona. A
strong correlation is found between the jet features and the energetic
distribution of the plasma of the inner corona which may be related to the
efficiency of the magnetic rotator. It is shown that observations of FRI and
FRII jets may be partially constrained by our model for spine jets. The
deceleration observed in FRI jets may be associated with a low magnetic
efficiency of the central magnetic rotator and an important thermal confinement
by the hot surrounding medium. Conversely, the strongly collimated and
accelerated FRII outflows may be self collimated by their own magnetic field
because of the high efficiency of the central magnetic rotator.Comment: Accepted for publication in the A&
Models to represent linguistic linked data
As the interest of the Semantic Web and computational linguistics communities in linguistic linked data (LLD) keeps increasing and the number of contributions that dwell on LLD rapidly grows, scholars (and linguists in particular) interested in the development of LLD resources sometimes find it difficult to determine which mechanism is suitable for their needs and which challenges have already been addressed. This review seeks to present the state of the art on the models, ontologies and their extensions to represent language resources as LLD by focusing on the nature of the linguistic content they aim to encode. Four basic groups of models are distinguished in this work: models to represent the main elements of lexical resources (group 1), vocabularies developed as extensions to models in group 1 and ontologies that provide more granularity on specific levels of linguistic analysis (group 2), catalogues of linguistic data categories (group 3) and other models such as corpora models or service-oriented ones (group 4). Contributions encompassed in these four groups are described, highlighting their reuse by the community and the modelling challenges that are still to be faced
Mesoporous Silicon Microparticles Enhance MHC Class I Cross-Antigen Presentation by Human Dendritic Cells
The mesoporous silicon microparticles (MSMPs) are excellent vehicles for releasing molecules inside the cell. The aim of this work was to use MSMPs to deliver viral specific MHC class I restricted epitopes into human antigen presenting cells (monocyte derived dendritic cells, MDDCs) to facilitate their capture, processing, and presentation to CD8+ (cytotoxic) T lymphocytes. We show for the first time that MSMPs vehiculation of antigenic peptides enhances their MHC class I presentation by human MDDCs to CD8 T lymphocytes
Postcranial morphology of the middle Pleistocene humans from Sima de los Huesos, Spain
Current knowledge of the evolution of the postcranial skeleton in the genus Homo is hampered by a geographically and chronologically scattered fossil record. Here we present a complete characterization of the postcranium of the middle Pleistocene paleodeme from the Sima de los Huesos (SH) and its paleobiological implications. The SH hominins show the following: (i) wide bodies, a plesiomorphic char- acter in the genus Homo inherited from their early hominin ancestors; (ii) statures that can be found in modern human middle-latitude pop- ulations that first appeared 1.6–1.5 Mya; and (iii) large femoral heads in some individuals, a trait that first appeared during the middle Pleistocene in Africa and Europe. The intrapopulational size variation in SH shows that the level of dimorphism was similar to modern humans (MH), but the SH hominins were less encephalized than Ne- andertals. SH shares many postcranial anatomical features with Ne- andertals. Although most of these features appear to be either plesiomorphic retentions or are of uncertain phylogenetic polarity, a few represent Neandertal apomorphies. Nevertheless, the full suite of Neandertal-derived features is not yet present in the SH popula- tion. The postcranial evidence is consistent with the hypothesis based on the cranial morphology that the SH hominins are a sister group to the later Neandertals. Comparison of the SH postcranial skeleton to other hominins suggests that the evolution of the postcranium oc- curred in a mosaic mode, both at a general and at a detailed level
Exploring the Free Energy Landscape: From Dynamics to Networks and Back
The knowledge of the Free Energy Landscape topology is the essential key to
understand many biochemical processes. The determination of the conformers of a
protein and their basins of attraction takes a central role for studying
molecular isomerization reactions. In this work, we present a novel framework
to unveil the features of a Free Energy Landscape answering questions such as
how many meta-stable conformers are, how the hierarchical relationship among
them is, or what the structure and kinetics of the transition paths are.
Exploring the landscape by molecular dynamics simulations, the microscopic data
of the trajectory are encoded into a Conformational Markov Network. The
structure of this graph reveals the regions of the conformational space
corresponding to the basins of attraction. In addition, handling the
Conformational Markov Network, relevant kinetic magnitudes as dwell times or
rate constants, and the hierarchical relationship among basins, complete the
global picture of the landscape. We show the power of the analysis studying a
toy model of a funnel-like potential and computing efficiently the conformers
of a short peptide, the dialanine, paving the way to a systematic study of the
Free Energy Landscape in large peptides.Comment: PLoS Computational Biology (in press
The neglected role of LITHOlogy in the response of Mediterranean FORest ecosystems to climate change: rationale and endorsing results from project LITHOFOR
XV Congreso Nacional de la AEET (El valor ,de la Naturaleza para una sociedad global), 18-21 de octubre, Plasencia, Cáceres.One of the main concerns of ecologists is to understand which factors (biogeographical, physiographical, disturbance, etc.) control ecosystem structure and function. It is surprising that lithology has rarely been considered despite its potential cascading effects on resource availability and ecological conditions. The project LITHOFOR aims to shed light on the role of lithology in forest ecosystem responses to climate change by focusing on pine (Pinus pinaster), Andalusian-fir (Abies pinsapo) and cork-oak (Quercus suber) forests across the unique natural laboratory representedby the Baetic and Rif ranges (S. Spain- N.-Morocco). In the western Mediterranean-Alborán region, climate conditions shift from hyperhumid to semiarid in scarcely a hundred kilometers along West to East longitudinal gradients, and its world-wide renowned geotectonic and lithological complexity allows for abundant forest stands across contrasting lithological contacts. The project is a coordinated multidisciplinary effort of forest ecologists, plant physiologists, geologists, soil scientists, biodiversity researchers and modelers to compare forest structure and functio n among three contrasting lithologies (carbonated, metapelites and ultramafic rocks). Results illustrate that lithological types influence the shape and intensity of patterns along climatic gradients (and in respo nse to drought) for variables as stand structure, tree growth, foliar and root functional traits, litter decomposition and nutrient cycling, and bi ological communities composition (plants, soil nematodes and microbes). This advocates that litho/edaphological factors deserve greater attention
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