811 research outputs found
No two without three: Modelling dynamics of the trio RNA virus-defective interfering genomes-RNA satellite
Almost all viruses, regardless of their genomic material, produce defective
viral genomes (DVG) as an unavoidable byproduct of their error-prone
replication. Defective interfering (DI) elements are a subgroup of DVGs that
have been shown to interfere with the replication of the wild-type (WT) virus.
Along with DIs, other genetic elements known as satellite RNAs (satRNAs), that
show no genetic relatedness with the WT virus, can co-infect cells with WT
helper viruses and take advantage of viral proteins for their own benefit.
These satRNAs have effects that range from reduced symptom severity to enhanced
virulence. The interference dynamics of DIs over WT viruses has been thoroughly
modelled at within-cell, within-host, and population levels. However, nothing
is known about the dynamics resulting from the nonlinear interactions between
WT viruses and DIs in the presence of satellites, a process that is frequently
seen in plant RNA viruses and in biomedically relevant pathosystems like
hepatitis B virus and its satellite. Here, we look into a
phenomenological mathematical model that describes how a WT virus replicates
and produces DIs in presence of a satRNA at the intra-host level. The WT virus
is subject to mechanisms of complementation, competition, and various levels of
interference from DIs and the satRNA. Examining the dynamics analytically and
numerically reveals three possible stable states: (i) full extinction, (ii)
satellite extinction and virus-DIs coexistence and (iii) full coexistence.
Assuming DIs replicate faster than the satRNA owed to their smaller size drives
to scenario (ii), which implies that DIs could wipe out the satRNA. In
addition, a small region of the parameter space exists wherein the system is
bistable (either scenarios (ii) or (iii) are concurrently stable).Comment: 22 pages, 9 figure
Co-evolutionnary network approach to cultural dynamics controlled by intolerance
Starting from Axelrod's model of cultural dissemination, we introduce a
rewiring probability, enabling agents to cut the links with their unfriendly
neighbors if their cultural similarity is below a tolerance parameter. For low
values of tolerance, rewiring promotes the convergence to a frozen monocultural
state. However, intermediate tolerance values prevent rewiring once the network
is fragmented, resulting in a multicultural society even for values of initial
cultural diversity in which the original Axelrod model reaches globalization
Semiclassical quantification of some two degree of freedom potentials: a Differential Galois approach
In this work we explain the relevance of the Differential Galois Theory in
the semiclassical (or WKB) quantification of some two degree of freedom
potentials. The key point is that the semiclassical path integral
quantification around a particular solution depends on the variational equation
around that solution: a very well-known object in dynamical systems and
variational calculus. Then, as the variational equation is a linear ordinary
differential system, it is possible to apply the Differential Galois Theory to
study its solvability in closed form. We obtain closed form solutions for the
semiclassical quantum fluctuations around constant velocity solutions for some
systems like the classical Hermite/Verhulst, Bessel, Legendre, and Lam\'e
potentials. We remark that some of the systems studied are not integrable, in
the Liouville-Arnold sense
Avulsión del tubérculo tibial asociada a epifisiólisis proximal de tibia
Las lesiones de la tuberosidad tibial anterior son fracturas poco frecuentes que se
presentan generalmente en adolescentes. Su extensión fisaria hacia la cortical posterior constituye
un hecho infrecuente. Algunos autores consideran necesaria la modificación de la clasifícacion
de Watson-Jones añadiéndole un tipo IV. Se presenta un caso de epifisiólisis proximal de tibia asociada
a avulsión del tubérculo tibial, se discute dicha clasificación, el mecanismo de producción
y revisión de la literaturaFractures of the anterior tibial tubercle are uncommon lesions, adolescents being
more frequently affected. Physeal extension through the posterior tibial cortical bone is rare. Some
authors have suggested that a new type IV can be added to the Watson-Jones classiflcation. In
this paper, we report a case with epiphysiolisis of the proximal tibia associated to an avulsion fracture
of the anterior tibial tubercle. The Watson-Jones classiflcation, the mechanism of injury are
discussed together a review of the literature
Physical activity quantification in elder women
Cuantificación de la actividad física en mujeres mayores
An eclipsing post-common-envelope binary in the field of the Kepler mission
We present a new eclipsing post-common-envelope binary, identified inside the Kepler field prior to the launch of the spacecraft. Multifilter photometry and radial velocity data are analysed with an eclipsing-binary modelling code to determine the physical parameters of the binary. Spectra of the system within the primary eclipse and uneclipsed allow us to identify the spectral characteristics of the primary and secondary components. The primary component of the binary is a DA white dwarf, with M≃ 0.61 M⊙, log g≃ 7.95 and Teff≃ 20 500 K. The detection of two flares and the emission signatures displayed in the spectra show that the secondary component of the system is chromospherically active and is classified as an active M4 main-sequence star. Its mass, radius and temperature are estimated as M≃ 0.39 M⊙, R≃ 0.37 R⊙ and Teff≃ 3200 K. The ephemeris of the system is HJD = 245 3590.436 126(10) + 0.350 468 722(6) ×E. This binary is a new post-common-envelope binary (PCEB), with physical parameters within the range found in other systems of this small group of evolved binarie
Wisdom of groups promotes cooperation in evolutionary social dilemmas
Whether or not to change strategy depends not only on the personal success of
each individual, but also on the success of others. Using this as motivation,
we study the evolution of cooperation in games that describe social dilemmas,
where the propensity to adopt a different strategy depends both on individual
fitness as well as on the strategies of neighbors. Regardless of whether the
evolutionary process is governed by pairwise or group interactions, we show
that plugging into the "wisdom of groups" strongly promotes cooperative
behavior. The more the wider knowledge is taken into account the more the
evolution of defectors is impaired. We explain this by revealing a dynamically
decelerated invasion process, by means of which interfaces separating different
domains remain smooth and defectors therefore become unable to efficiently
invade cooperators. This in turn invigorates spatial reciprocity and
establishes decentralized decision making as very beneficial for resolving
social dilemmas.Comment: 8 two-column pages, 7 figures; accepted for publication in Scientific
Report
Ejercicio interlaboratorio de bioensayos marinos para la evaluación de la calidad ambiental de sedimentos costeros. IV. Ensayo de toxicidad sobre sedimento con crustáceos anfípodos
9 páginas, 2 figuras, 3 tablas.[EN] Interlaboratory variability was studied for the bioassay using crustacean amphipods. Nine series of data were obtained from different laboratories using four different species (Ampelisca brevicornis, Corophium volutator, Corophium multisetosum and Microdeutopus gryllotalpa), all previously used for sediment toxicity assessment in Spain. Results were studied for interlaboratory variability and according to different confounding factors. The coefficients of variation were similar to those previously reported for this bioassay and sample classification was homogeneous among the laboratories that successfully completed the exercise. No significant tendencies related to test species were identified and it seems that the factor most critically affecting test results and the classification of samples is storage time before testing.[ES] Se estudió la precisión interlaboratorio del bioensayo con crustáceos anfípodos. Se recogieron nueve series de datos procedentes de distintos laboratorios europeos y de cuatro especies distintas (Ampelisca brevicornis, Corophium volutator, Corophium multisetosum y Microdeutopus gryllotalpa), todas ellas usadas previamente para la caracterización de la toxicidad de sedimentos en España. Esos resultados se estudiaron para evaluar la variabilidad interlaboratorio de acuerdo a las diferentes especies y los distintos tiempos de almacenamiento de las muestras antes del ensayo. Los resultados mostraron coeficientes de variación similares a los encontrados en estudios previos y permitieron una clasificación homogénea de las muestras entre los laboratorios que completaron el ejercicio con éxito. No se identificaron tendencias significativas debidas al uso de distintas especies y, al parecer, el factor que puede afectar más críticamente la clasificación de las muestras y, por lo tanto, el uso de los resultados para la toma de decisiones, es el tiempo de almacenamiento de los sedimentos previamente al desarrollo del ensayo.This study was carried out under a joint research project between CEDEX and the University of Cádiz. Part of the work was funded by the Spanish Ministry of Science and Technology REN2002_01699/TECNO). The first author was supported by a grant (FPI) from the Spanish Ministry of Education and Science.Peer reviewe
Interdependent network reciprocity in evolutionary games
Besides the structure of interactions within networks, also the interactions between networks are of the outmost
importance. We therefore study the outcome of the public goods game on two interdependent networks that are
connected by means of a utility function, which determines how payoffs on both networks jointly influence the
success of players in each individual network. We show that an unbiased coupling allows the spontaneous
emergence of interdependent network reciprocity, which is capable to maintain healthy levels of public
cooperation even in extremely adverse conditions. The mechanism, however, requires simultaneous formation of
correlated cooperator clusters on both networks. If this does not emerge or if the coordination process is
disturbed, network reciprocity fails, resulting in the total collapse of cooperation. Network interdependence can
thus be exploited effectively to promote cooperation past the limits imposed by isolated networks, but only if the
coordination between the interdependent networks is not disturbe
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