29 research outputs found
Competition between surface relaxation and ballistic deposition models in scale free networks
In this paper we study the scaling behavior of the fluctuations in the steady
state with the system size for a surface growth process given by the
competition between the surface relaxation (SRM) and the Ballistic Deposition
(BD) models on degree uncorrelated Scale Free networks (SF), characterized by a
degree distribution , where is the degree of a node.
It is known that the fluctuations of the SRM model above the critical dimension
() scales logarithmically with on euclidean lattices. However,
Pastore y Piontti {\it et. al.} [A. L. Pastore y Piontti {\it et. al.}, Phys.
Rev. E {\bf 76}, 046117 (2007)] found that the fluctuations of the SRM model in
SF networks scale logarithmically with for and as a constant
for . In this letter we found that for a pure ballistic
deposition model on SF networks scales as a power law with an exponent
that depends on . On the other hand when both processes are in
competition, we find that there is a continuous crossover between a SRM
behavior and a power law behavior due to the BD model that depends on the
occurrence probability of each process and the system size. Interestingly, we
find that a relaxation process contaminated by any small contribution of
ballistic deposition will behave, for increasing system sizes, as a pure
ballistic one. Our findings could be relevant when surface relaxation
mechanisms are used to synchronize processes that evolve on top of complex
networks.Comment: 8 pages, 6 figure
Temporal percolation of a susceptible adaptive network
In the past decades, many authors have used the susceptible?infected?recovered model to study the impact of the disease spreading on the evolution of the infected individuals. However, few authors focused on the temporal unfolding of the susceptible individuals. In this paper, we study the dynamic of the susceptible-infected-recovered model in an adaptive network that mimics the transitory deactivation of permanent social contacts, such as friendship and work-ship ties. Using an edge-based compartmental model and percolation theory, we obtain the evolution equations for the fraction susceptible individuals in the susceptible biggest component. In particular, we focus on how the individualÂŽs behavior impacts on the dilution of the susceptible network. We show that, as a consequence, the spreading of the disease slows down, protecting the biggest susceptible cluster by increasing the critical time at which the giant susceptible component is destroyed. Our theoretical results are fully supported by extensive simulations.Fil: Valdez, Lucas Daniel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Mar del Plata. Instituto de Investigaciones FĂsicas de Mar del Plata; ArgentinaFil: Macri, Pablo Alejandro. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Mar del Plata. Instituto de Investigaciones FĂsicas de Mar del Plata; ArgentinaFil: Braunstein, L. A.. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Mar del Plata. Instituto de Investigaciones FĂsicas de Mar del Plata; Argentina. Boston University; Estados Unido
Study of a market model with conservative exchanges on complex networks
Many models of market dynamics make use of the idea of conservative wealth exchanges among economic agents. A few years ago an exchange model using extremal dynamics was developed and a very interesting result was obtained: a self-generated minimum wealth or poverty line. On the other hand, the wealth distribution exhibited an exponential shape as a function of the square of the wealth. These results have been obtained both considering exchanges between nearest neighbors or in a mean field scheme. In the present paper we study the effect of distributing the agents on a complex network. We have considered archetypical complex networks: ErdösâRĂ©nyi random networks and scale-free networks. The presence of a poverty line with finite wealth is preserved but spatial correlations are important, particularly between the degree of the node and the wealth. We present a detailed study of the correlations, as well as the changes in the Gini coefficient, that measures the inequality, as a function of the type and average degree of the considered networks.Fil: Braunstein, Lidia A.. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de FĂsica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Mar del Plata. Instituto de Investigaciones FĂsicas de Mar del Plata; Argentina. Boston University; Estados UnidosFil: Macri, Pablo Alejandro. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de FĂsica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Mar del Plata. Instituto de Investigaciones FĂsicas de Mar del Plata; ArgentinaFil: Iglesias, JosĂ© Roberto. Universidade Federal do Rio Grande do Sul; Brasi
Jamming in complex networks with degree correlation
We study the effects of the degree-degree correlations on the pressure
congestion J when we apply a dynamical process on scale free complex networks
using the gradient network approach. We find that the pressure congestion for
disassortative (assortative) networks is lower (bigger) than the one for
uncorrelated networks which allow us to affirm that disassortative networks
enhance transport through them. This result agree with the fact that many real
world transportation networks naturally evolve to this kind of correlation. We
explain our results showing that for the disassortative case the clusters in
the gradient network turn out to be as much elongated as possible, reducing the
pressure congestion J and observing the opposite behavior for the assortative
case. Finally we apply our model to real world networks, and the results agree
with our theoretical model
Epidemics in partially overlapped multiplex networks
Many real networks exhibit a layered structure in which links in each layer
reflect the function of nodes on different environments. These multiple types
of links are usually represented by a multiplex network in which each layer has
a different topology. In real-world networks, however, not all nodes are
present on every layer. To generate a more realistic scenario, we use a
generalized multiplex network and assume that only a fraction of the nodes
are shared by the layers. We develop a theoretical framework for a branching
process to describe the spread of an epidemic on these partially overlapped
multiplex networks. This allows us to obtain the fraction of infected
individuals as a function of the effective probability that the disease will be
transmitted . We also theoretically determine the dependence of the epidemic
threshold on the fraction of shared nodes in a system composed of two
layers. We find that in the limit of the threshold is dominated by
the layer with the smaller isolated threshold. Although a system of two
completely isolated networks is nearly indistinguishable from a system of two
networks that share just a few nodes, we find that the presence of these few
shared nodes causes the epidemic threshold of the isolated network with the
lower propagating capacity to change discontinuously and to acquire the
threshold of the other network.Comment: 13 pages, 4 figure
Clinical utility of chromosomal microarray analysis in invasive prenatal diagnosis
Novel methodologies for detection of chromosomal abnormalities have been made available in the recent years but their clinical utility in prenatal settings is still unknown. We have conducted a comparative study of currently available methodologies for detection of chromosomal abnormalities after invasive prenatal sampling. A multicentric collection of a 1-year series of fetal samples with indication for prenatal invasive sampling was simultaneously evaluated using three screening methodologies: (1) karyotype and quantitative fluorescent polymerase chain reaction (QF-PCR), (2) two panels of multiplex ligation-dependent probe amplification (MLPA), and (3) chromosomal microarray-based analysis (CMA) with a targeted BAC microarray. A total of 900 pregnant women provided informed consent to participate (94% acceptance rate). Technical performance was excellent for karyotype, QF-PCR, and CMA (~1% failure rate), but relatively poor for MLPA (10% failure). Mean turn-around time (TAT) was 7Â days for CMA or MLPA, 25 for karyotype, and two for QF-PCR, with similar combined costs for the different approaches. A total of 57 clinically significant chromosomal aberrations were found (6.3%), with CMA yielding the highest detection rate (32% above other methods). The identification of variants of uncertain clinical significance by CMA (17, 1.9%) tripled that of karyotype and MLPA, but most alterations could be classified as likely benign after proving they all were inherited. High acceptability, significantly higher detection rate and lower TAT, could justify the higher cost of CMA and favor targeted CMA as the best method for detection of chromosomal abnormalities in at-risk pregnancies after invasive prenatal sampling
Bycatch of franciscana dolphins Pontoporia blainvillei and the dynamic of artisanal fisheries in the species' southernmost area of distribution
Na Argentina, a toninha Ă© um dos cetĂĄceos mais vulnerĂĄveis devido Ă s capturas por rede de pesca artesanal. O presente estudo teve como objetivo estimar as capturas acidentais no sul da provĂncia de Buenos Aires, atravĂ©s de entrevistas aos capitĂŁes de barcos de pesca artesanal, entre os anos 2006-2009. As capturas foram reportadas para redes de emalhe e de camarĂŁo; com as mais altas frequĂȘncias entre outubro e fevereiro, a 5 km da costa e 10-20 m de profundidade. A mortalidade acidental mĂ©dia anual estimada foi de 107 golfinhos (IC 95% = 87-129), 92 em redes de emalhe (IC 95% = 73-112) e 15 em redes de camarĂŁo (IC 95% = 8-25), com uma captura de 0,029 golfinhos/km de rede de emalhe (IC 95% = 0,023-0,036) e 0,024/rede de camarĂŁo (IC 95% = 0,012-0,035). As flutuaçÔes anuais responderam principalmente Ă s diferenças nos dias de pesca. Considerando o Ășltimo levantamento estimativo feito para o norte costeiro da provĂncia, estima-se uma mortalidade entre 360-539 golfinhos/ano em toda a provĂncia de Buenos Aires. Esses valores correspondem de 2,5-3,7% da abundĂąncia populacional da Argentina; o que traria como consequĂȘncia um declĂnio populacional da espĂ©cie, tornando-se fundamental encontrar alternativas de pesca para a ĂĄrea.In Argentina, the franciscana dolphin is one of the most vulnerable cetaceans regularly entangled in coastal artisanal fishery nets. The aim of this paper is to estimate the species' incidental mortality on the Southern coast of Buenos Aires province through interviews with the captains of artisanal fishing vessels, in the period 2006-2009. Franciscana bycatch was reported for gillnets and shrimper gear all year round but it occurred more frequently between October and February, at 5 km offshore and 10-20 m depth. The estimated mean annual incidental mortality was 107 dolphins (CI 95% = 87-129), 92 caught in gillnets (CI 95% = 73-112) and 15 in shrimpers' gear (CI 95% = 8-25) with a capture per unit effort of 0.029 dolphins per km of gillnet (CI 95% = 0.023-0.036) and 0.022 per shrimpe r's net (CI 95% = 0.012-0.035). Annual fluctuations were due to differences in the number of gillnetting fishing days. If mortality estimates for the Northern coast are also taken into account, values attain a maximum of 360-539 dolphins bycaught in the entire Buenos Aires province, representing 2.5-3.7% of the species' abundance in Argentina. This will inevitably lead to the decline of franciscana dolphin populations in the near future unless alternative fishing grounds are identified and alternative gearadopted