scholarly journals Contact process with exogenous infection and the scaled SIS process

2017 ◽  
Vol 5 (5) ◽  
pp. 712-733 ◽  
Author(s):  
June Zhang ◽  
José M.F. Moura ◽  
June Zhang
Keyword(s):  
Equilibrium Distribution ◽  
Equilibrium Configuration ◽  
Contact Process ◽  
Finite Size ◽  
Infection Rates ◽  
Contact Processes ◽  
Arbitrary Topology ◽  
Extended Contact ◽  
Complete Networks

Abstract Propagation of contagion in networks depends on the graph topology. This article is concerned with studying the time-asymptotic behaviour of the extended contact processes on static, undirected, finite-size networks. This is a contact process with nonzero exogenous infection rate (also known as the $\epsilon$-susceptible-infected-susceptible model). The only known analytical characterization of the equilibrium distribution of this process is for complete networks. For large networks with arbitrary topology, it is infeasible to numerically solve for the equilibrium distribution since it requires solving the eigenvalue-eigenvector problem of a matrix that is exponential in $N$, the size of the network. We derive a condition on the infection rates under which, depending on the degree distribution of the network, the equilibrium distribution of extended contact processes on arbitrary, finite-size networks is well approximated by a closed-form formulation. We confirm the goodness of the approximation with small networks answering inference questions like the distribution of the percentage of infected individuals and the most-probable equilibrium configuration. We then use the approximation to analyse the equilibrium distribution of the extended contact process on the 4941-node US Western power grid.

scholarly journals Genetic characterization of Cryptosporidium spp. and Giardia duodenalis in dogs and cats in Guangdong, China

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Jiayu Li ◽  
Xiaoyu Dan ◽  
Kexin Zhu ◽  
Na Li ◽  
Yaqiong Guo ◽  
...  
Keyword(s):  
Risk Factors ◽  
Genetic Characterization ◽  
Giardia Duodenalis ◽  
Ratio Analysis ◽  
Infection Rates ◽  
Sequence Analyses ◽  
Chi Square ◽  
Significant Difference ◽  
Chi Square Test

Abstract Background There are only limited number of reports on molecular epidemiology of Cryptosporidium spp. and Giardia duodenalis in dogs and cats in China. This study was conducted to assess the infection rates, genetic identity, and public health potential of these parasites in dogs and cats in Guangdong, China. Methods PCR and sequence analyses were used to identify and genotype Cryptosporidium spp. and G. duodenalis in fecal samples from 641 dogs and 418 cats in Guangdong. Chi-square test and odds ratio analysis were used to compare the occurrence rates of these pathogens and identify risk factors for infection. Results The overall infection rates of Cryptosporidium spp. and G. duodenalis were 6.9% (44/641) and 9.4% (60/641) in dogs, and 6.2% (26/418) and 3.6% (15/418) in cats. Purebred cats (12.4%; χ2 = 5.110, OR = 2.8, P = 0.024) and dogs (10.8%; χ2 = 5.597, OR = 4.8, P = 0.018) were more likely to be infected by Cryptosporidium spp. and G. duodenalis, respectively. Dogs (12.0%; χ2 = 7.589, OR = 2.6, P = 0.006) and cats (13.6%; χ2 = 8.235, OR = 3.5, P = 0.004) under 6 months had significantly higher infection rates of Cryptosporidium spp. than older animals. Household (13.9%; χ2 = 10.279, OR = 2.6, P = 0.008) and pet shop dogs (11.0%; χ2 = 7.182, OR = 2.0, P = 0.048) had higher occurrence of Cryptosporidium spp., as was the case for G. duodenalis occurrence in experimental dogs (13.4%; χ2 = 9.223, OR = 1.9, P = 0.017). Cryptosporidium canis (n = 42), C. muris (n = 1) and Cryptosporidium rat genotype IV (n = 1) were identified in dogs, while C. felis (n = 21), C. parvum (n = 3), C. muris (n = 1) and Cryptosporidium rat genotype IV (n = 1) were identified in cats. In contrast, the canine-specific assemblages C (n = 27) and D (n = 26) and the feline-specific assemblage F (n = 14) were almost exclusively the only genotypes of G. duodenalis in dogs and cats, respectively. There was no significant difference in infection rates of Cryptosporidium spp. and G. duodenalis between diarrheal and non-diarrheal pets. Conclusions While domestic pets in Guangdong are infected with zoonotic Cryptosporidium species, they are mainly infected with host-specific G. duodenalis genotypes. Risk factors for infections differ between Cryptosporidium spp. and G. duodenalis and between dogs and cats.

ENTROPIC AND MULTIFRACTAL ANALYSIS OF DISORDERED MORPHOLOGIES

Fractals ◽  
1993 ◽  
Vol 01 (03) ◽  
pp. 671-679 ◽  
Author(s):  
A. BEGHDADI ◽  
C. ANDRAUD ◽  
J. LAFAIT ◽  
J. PEIRO ◽  
M. PERREAU
Keyword(s):  
Multifractal Analysis ◽  
Characteristic Length ◽  
Finite Size ◽  
Morphological Parameter ◽  
Efficient Tool ◽  
Optimum Length ◽  
Maximum Information ◽  
Configuration Entropy ◽  
Simulated Images

We propose the configuration entropy as an efficient tool of characterization of the disorder of random morphologies and as a pertinent morphological parameter for describing the optical properties. When increasing the size of observation of an image, it undergoes a maximum at a characteristic length which is the optimum length at which the image must be observed to get the maximum information. When applied to computer simulated images, the configuration entropy is more powerful, less ambiguous and less sensitive to the finite size of images than the generalized fractal dimension.

scholarly journals Complex role of space in the crossing of fitness valleys by asexual populations

2014 ◽  
Vol 11 (95) ◽  
pp. 20140014 ◽  
Author(s):  
Natalia L. Komarova ◽  
Leili Shahriyari ◽  
Dominik Wodarz
Keyword(s):  
Complex Traits ◽  
Contact Process ◽  
Complex Trait ◽  
Spatial Interactions ◽  
Wild Type ◽  
Contact Processes ◽  
Rate Of Evolution ◽  
Moran Process ◽  
Asexual Populations

The evolution of complex traits requires the accumulation of multiple mutations, which can be disadvantageous, neutral or advantageous relative to the wild-type. We study two spatial (two-dimensional) models of fitness valley crossing (the constant-population Moran process and the non-constant-population contact process), varying the number of loci involved and the degree of mixing. We find that spatial interactions accelerate the crossing of fitness valleys in the Moran process in the context of neutral and disadvantageous intermediate mutants because of the formation of mutant islands that increase the lifespan of mutant lineages. By contrast, in the contact process, spatial structure can accelerate or delay the emergence of the complex trait, and there can even be an optimal degree of mixing that maximizes the rate of evolution. For advantageous intermediate mutants, spatial interactions always delay the evolution of complex traits, in both the Moran and contact processes. The role of the mutant islands here is the opposite: instead of protecting, they constrict the growth of mutants. We conclude that the laws of population growth can be crucial for the effect of spatial interactions on the rate of evolution, and we relate the two processes explored here to different biological situations.

Molecular Simulation Study of Vapor-Liquid Equilibrium of Morse Fluids

2007 ◽  
Vol 2 (3) ◽  
Author(s):  
Sang Kyu Kwak ◽  
Jayant K Singh ◽  
Jhumpa Adhikari
Keyword(s):  
Critical Temperature ◽  
Scaling Law ◽  
Finite Size ◽  
Potential Energy Function ◽  
Liquid Equilibrium ◽  
Vapor Liquid Equilibrium ◽  
Tuning Parameters ◽  
Type Relation ◽  
Vapor Liquid

The Morse potential energy function (PEF) is considered regarding the characterization of interaction forces of particles with tuning parameters. Phase coexistence of Morse fluids is predicted for different steepness and range of the PEF parameters using the grand-canonical transition matrix Monte Carlo (GC-TMMC) method, with quantification of the parameter S, which is the product of a constant with a unit of reciprocal length and the equilibrium distance between two molecules. We found that a lower limit of S exists bounded by infinite critical temperature. The critical properties of the vapor-liquid equilibrium curves are estimated using a rectilinear diameter method and a scaling law approach. A Clausius-Clayperon type relation of S and critical temperature is derived in this work. Vapor-liquid surface tension of Morse fluids by finite size scaling and GC-TMMC is also reported. Surface tensions are found to be higher at lower S.

Ultrasonic characterization of anisotropic rocks: Impact of transducers’ size and geometry on data interpretation

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. C99-C105
Author(s):  
Yevhen Kovalyshen ◽  
Joel Sarout ◽  
Jeremie Dautriat ◽  
Bruce Maney ◽  
Maxim Lebedev
Keyword(s):  
Finite Size ◽  
Data Interpretation ◽  
Point Sources ◽  
Data Sets ◽  
Ultrasonic Characterization ◽  
Multiple Data ◽  
Anisotropic Rocks ◽  
Multiple Data Sets ◽  
The Impact

Typical ultrasonic laboratory measurements of rock physical properties are conducted with ultrasonic transducers that are relatively large compared to the rock sample. We have determined the impact of the transducer size on the resulting velocity estimations. To improve data interpretation, we explore two complementary avenues: (1) explicitly account for the finite size of the transducers as part of the data interpretation/correction workflow, rather than assuming point sources, and (2) reducing the effective size of the transducers at the hardware design level. Both approaches as well as their combination have been tested successfully on multiple data sets including artificial homogeneous and isotropic samples as well as natural anisotropic rocks such as shales.

Equilibrium Distribution of Alloyed Nanowires

2011 ◽  
Vol 172-174 ◽  
pp. 676-681 ◽  
Author(s):  
Emile Maras ◽  
Isabelle Braems ◽  
Fabienne Berthier
Keyword(s):  
Size Distribution ◽  
Equilibrium Distribution ◽  
Canonical Ensemble ◽  
Complete Characterization ◽  
Total Density ◽  
Alloying Effect ◽  
One Dimensional ◽  
Analytical Formulae ◽  
Grand Canonical

The size distribution and the total density of clusters of a one-dimensional pure deposit can be expressed analytically from the Ising model. For a codeposit, the alloying effect and the presence of broken bonds at the cluster edges lead to inhomogeneities of the chemical composition of the clusters. We investigate the influence of codeposition on the size distribution of clusters in the case of an alloy that forms an ideal solution. We obtain the exact solution for the size distribution of clusters while the complete characterization of the system results from coupled analytical formulae in the grand-canonical ensemble. The results of this analytical model are successfully compared with those obtained by Monte Carlo simulations.

scholarly journals Stochastic Dynamics of a Finite-Size Spiking Neural Network

2007 ◽  
Vol 19 (12) ◽  
pp. 3262-3292 ◽  
Author(s):  
Hédi Soula ◽  
Carson C. Chow
Keyword(s):  
Neural Network ◽  
Equilibrium Distribution ◽  
Stochastic Dynamics ◽  
Mean Field Theory ◽  
Mean Field ◽  
Finite Size ◽  
Network Activity ◽  
Neural Dynamics ◽  
Spiking Neural Network ◽  
Firing Activity

We present a simple Markov model of spiking neural dynamics that can be analytically solved to characterize the stochastic dynamics of a finite-size spiking neural network. We give closed-form estimates for the equilibrium distribution, mean rate, variance, and autocorrelation function of the network activity. The model is applicable to any network where the probability of firing of a neuron in the network depends on only the number of neurons that fired in a previous temporal epoch. Networks with statistically homogeneous connectivity and membrane and synaptic time constants that are not excessively long could satisfy these conditions. Our model completely accounts for the size of the network and correlations in the firing activity. It also allows us to examine how the network dynamics can deviate from mean field theory. We show that the model and solutions are applicable to spiking neural networks in biophysically plausible parameter regimes.

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