3,305 research outputs found
Logarithmic growth dynamics in software networks
In a recent paper, Krapivsky and Redner (Phys. Rev. E, 71 (2005) 036118)
proposed a new growing network model with new nodes being attached to a
randomly selected node, as well to all ancestors of the target node. The model
leads to a sparse graph with an average degree growing logarithmically with the
system size. Here we present compeling evidence for software networks being the
result of a similar class of growing dynamics. The predicted pattern of network
growth, as well as the stationary in- and out-degree distributions are
consistent with the model. Our results confirm the view of large-scale software
topology being generated through duplication-rewiring mechanisms. Implications
of these findings are outlined.Comment: 7 pages, 3 figures, published in Europhysics Letters (2005
Controlling Excitations Inversion of a Cooper Pair Box Interacting with a Nanomechanical Resonator
We investigate the action of time dependent detunings upon the excitation
inversion of a Cooper pair box interacting with a nanomechanical resonator. The
method employs the Jaynes-Cummings model with damping, assuming different decay
rates of the Cooper pair box and various fixed and t-dependent detunings. It is
shown that while the presence of damping plus constant detunings destroy the
collapse/revival effects, convenient choices of time dependent detunings allow
one to reconstruct such events in a perfect way. It is also shown that the mean
excitation of the nanomechanical resonator is more robust against damping of
the Cooper pair box for convenient values of t-dependent detunings.Comment: 11 pages, 5 figure
Nuclear effects in neutrino induced reactions
We discuss the relevance of nuclear medium effects in the analysis of some
low and medium energy neutrino reactions of current interest. In particular, we
study the Quasi-Elastic (QE) process, where RPA correlations and Final State
Interactions (FSI) are shown to play a crucial role. We have also investigated
the neutrino induced coherent pion production. We find a strong reduction of
the cross section due to the distortion of the pion wave function and the
modification of the production mechanisms in the nucleus. The sensitivity of
the results to the axial coupling has been also
investigated.Comment: To appear in the proceedings of Chiral Symmetry in Hadron and Nuclear
Physics (Chiral07), Osaka, Japan, November 13-16, 200
Border Collision Bifurcations in a Generalized Model of Population Dynamics
We analyze the dynamics of a generalized discrete time population model of a two-stage species with recruitment and capture. This generalization, which is inspired by other approaches and real data that one can find in literature, consists in considering no restriction for the value of the two key parameters appearing in the model, that is, the natural death rate and the mortality rate due to fishing activity. In the more general case the feasibility of the system has been preserved by posing opportune formulas for the piecewise map defining the model. The resulting two-dimensional nonlinear map is not smooth, though continuous, as its definition changes as any border is crossed in the phase plane. Hence, techniques from the mathematical theory of piecewise smooth dynamical systems must be applied to show that, due to the existence of borders, abrupt changes in the dynamic behavior of population sizes and multistability emerge. The main novelty of the present contribution with respect to the previous ones is that, while using real data, richer dynamics are produced, such as fluctuations and multistability. Such new evidences are of great interest in biology since new strategies to preserve the survival of the species can be suggested
Activity ageing in growing networks
We present a model for growing information networks where the ageing of a
node depends on the time at which it entered the network and on the last time
it was cited. The model is shown to undergo a transition from a small-world to
large-world network. The degree distribution may exhibit very different shapes
depending on the model parameters, e.g. delta-peaked, exponential or power-law
tailed distributions.Comment: 9 pages, 2 figure
Numerical study of interface cracking in composite structures using a novel geometrically nonlinear Linear Elastic Brittle Interface Model: Mixed-mode fracture conditions and application to structured interfaces
Interface cracking is one of the most prominent failure modes in fibre
reinforced polymer (FRP) composites. Recent trends in high-tech applications of
FRP composites exploit the limits of the load bearing capacity, generally
encompassing the development of notable nonlinear effects from geometrical and
material signatures. In this investigation, we present a comprehensive
assessment of the new Linear Elastic Brittle Interface Model (LEBIM) in
geometrically nonlinear applications undergoing mixed-mode fracture conditions.
This interface model for triggering fracture events is formulated through the
advocation of continuum-like assumptions (for initial non-zero interface
thickness) and allows the incorporation of the potential role of the in-plane
deformation effects. The performance of the present interface model is
demonstrated through the simulation of specimens with mixed-mode delamination,
with special attention for its application in samples equipped with structured
interfaces. Current predictions exhibit an excellent agreement with respect to
experimental data, validating the proposed methodology
La adulteración de productos de farmacia en los Estatutos del Colegio de Boticarios de Palermo (siglos XV-XVI)
El tema de la posible adulteración tanto de medicamentos como de cualquier otro producto que se pudiera vender en una botica fué una constante preocupación de los legisladores de la ciudad de Pelermo en los siglos XV y XVI. Aquí presentamos un estudio de los capítulos a ello dedicados por los sucesivos estatutos del Colegio de Boticarios, así como algunos datos comparativos con otros lugares del mismo área geográfica
Los trabajos de publicación de la flora peruviana et chilensis a través de la cartas de C. Gómez Ortega
Concluída la expedición científica de 1777 a Perú y Chile, ya la hora de la publicación de los trabajos, surgieron diversos problemas, que estudiamos a través de la correspondencia del director de aquella, Casimiro Gómez Ortega
Aspectos deontológicos y prácticos de la confección de medicamentos, Palermo. Siglos XV y XVI
Las normativas legales sobre el ejercicio de la farmacia en la ciudad de Palermo, en los siglo XV y XVI, contemplan como uno de sus aspectos fundamentales el de la correcta elaboración de los medicamentos y otros productos farmacéuticos por parte de los boticarios, en una etapa de la historia en que la adulteración de aquellos era moneda corriente
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