In this paper,an improved Susceptible-Infected-Susceptible(SIS) epidemic spreading model is proposed in order to provide a theoretical method to analyze and predict the spreading of diseases.This model is based on the...In this paper,an improved Susceptible-Infected-Susceptible(SIS) epidemic spreading model is proposed in order to provide a theoretical method to analyze and predict the spreading of diseases.This model is based on the following ideas:in social networks,the contact probability between nodes is decided by their social distances and their active degrees.The contact probability of two indirectly connected nodes is decided by the shortest path between them.Theoretical analysis and simulation experiment were conducted to evaluate the performance of this improved model.Because the proposed model is independent of the network structure,simulation experiments were done in several kinds of networks,namely the ER network,the random regular network,the WS small world network,and the BA scale-free network,in order to study the influences of certain factors have on the epidemic spreading,such as the social contact active degree,the network structure,the average degree,etc.This improved model provides an idea for studying the spreading rule of computer virus,attitudes,fashion styles and public opinions in social networks.展开更多
Vertical transmission has become the most common mode of transmission of hepatitis C virus (HCV) in children.The rate of perinatal transmission from an HCVinfected mother to her child ranges from 2% to 5% and the prev...Vertical transmission has become the most common mode of transmission of hepatitis C virus (HCV) in children.The rate of perinatal transmission from an HCVinfected mother to her child ranges from 2% to 5% and the prevalence of HCV in children in developed countries ranges between 0.1% and 0.4%.Spontaneous viral clearance seems to be dependent on the genotype and has been reported between 2.4%-25%.For chronically infected patients,treatment with recombinant polyethylene glycol (PEG)-interferon α-2b and daily ribavirin has now been approved as standard treatment for children 2-17 years of age.In five large prospective studies,a total of 318 children and adolescents aged 3-17 years were treated either with subcutaneous PEG-interferon α-2b at a dose of 1-1.5 μg/kg or 60 μg/m2 once a week in combination with oral ribavirin (15 mg/kg per day) or PEG-interferon α-2a with ribavirin.Subjects with genotype 1 and 4 received the medication for 48 wk and individuals with genotype 2 and 3 mainly for 24 wk.Overall sustained viral response (SVR) was achieved in 193/318 (60.7%) of treated patients.Stratified for genotype;120/234 (51%) with genotype 1,68/73 (93%) with genotype 2/3,and 6/11 (55%) with genotype 4 showed SVR.Relapse rate was between 7.7% and 17%.Overall,treatment was well tolerated;how-ever,notable side effects were present in approximately 20%.According to recent experiences in the treatment of chronic hepatitis C in children and adolescents,a combination of PEG-interferon α with ribavirin has been found to be well tolerated and highly efficacious,particularly in individuals with genotype 2/3.Thus,this treatment can be recommended as standard of care until more effective treatment options will become available for genotype 1 patients.展开更多
Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it ...Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining contagious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli： the red-footed tortoise Geochelone carbonaria. A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions： observation of conditioned yawn, non demonstration control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a final experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions： real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes [Current Zoology 57 （4）： 477-484, 2011].展开更多
Modeling and simulation of infectious diseases help to predict the likely outcome of an epidemic. In this paper, a spatial susceptible-infective-susceptible （SIS） type of epidemiological disease model with self- and...Modeling and simulation of infectious diseases help to predict the likely outcome of an epidemic. In this paper, a spatial susceptible-infective-susceptible （SIS） type of epidemiological disease model with self- and cross-diffusion are investigated. We study the effect of diffusion on the stability of the endemic equilibrium with disease-induced mortality and nonlinear incidence rate, In the absence of diffusion the stationary solution stays stable but becomes unstable with respect to diffusion and that Turing instability takes place. We show that a standard （self-diffusion） system may be either stable or unstable, cross-diffusion response can stabilize an unstable standard system or decrease a ＂ihlring space （the space which the emergence of spatial patterns is holding） compared to the ~lhlring space with self-diffusion, i.e. the cross-diffusion response is an important factor that should not be ignored when pattern emerges. Numerical simulations are provided to illustrate and extend the theoretical results.展开更多
基金supported by National Natural Science Foundation of China 61301091Shaanxi Province Science and Technology Project 2015GY015
文摘In this paper,an improved Susceptible-Infected-Susceptible(SIS) epidemic spreading model is proposed in order to provide a theoretical method to analyze and predict the spreading of diseases.This model is based on the following ideas:in social networks,the contact probability between nodes is decided by their social distances and their active degrees.The contact probability of two indirectly connected nodes is decided by the shortest path between them.Theoretical analysis and simulation experiment were conducted to evaluate the performance of this improved model.Because the proposed model is independent of the network structure,simulation experiments were done in several kinds of networks,namely the ER network,the random regular network,the WS small world network,and the BA scale-free network,in order to study the influences of certain factors have on the epidemic spreading,such as the social contact active degree,the network structure,the average degree,etc.This improved model provides an idea for studying the spreading rule of computer virus,attitudes,fashion styles and public opinions in social networks.
文摘Vertical transmission has become the most common mode of transmission of hepatitis C virus (HCV) in children.The rate of perinatal transmission from an HCVinfected mother to her child ranges from 2% to 5% and the prevalence of HCV in children in developed countries ranges between 0.1% and 0.4%.Spontaneous viral clearance seems to be dependent on the genotype and has been reported between 2.4%-25%.For chronically infected patients,treatment with recombinant polyethylene glycol (PEG)-interferon α-2b and daily ribavirin has now been approved as standard treatment for children 2-17 years of age.In five large prospective studies,a total of 318 children and adolescents aged 3-17 years were treated either with subcutaneous PEG-interferon α-2b at a dose of 1-1.5 μg/kg or 60 μg/m2 once a week in combination with oral ribavirin (15 mg/kg per day) or PEG-interferon α-2a with ribavirin.Subjects with genotype 1 and 4 received the medication for 48 wk and individuals with genotype 2 and 3 mainly for 24 wk.Overall sustained viral response (SVR) was achieved in 193/318 (60.7%) of treated patients.Stratified for genotype;120/234 (51%) with genotype 1,68/73 (93%) with genotype 2/3,and 6/11 (55%) with genotype 4 showed SVR.Relapse rate was between 7.7% and 17%.Overall,treatment was well tolerated;how-ever,notable side effects were present in approximately 20%.According to recent experiences in the treatment of chronic hepatitis C in children and adolescents,a combination of PEG-interferon α with ribavirin has been found to be well tolerated and highly efficacious,particularly in individuals with genotype 2/3.Thus,this treatment can be recommended as standard of care until more effective treatment options will become available for genotype 1 patients.
文摘Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining contagious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli： the red-footed tortoise Geochelone carbonaria. A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions： observation of conditioned yawn, non demonstration control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a final experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions： real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes [Current Zoology 57 （4）： 477-484, 2011].
文摘Modeling and simulation of infectious diseases help to predict the likely outcome of an epidemic. In this paper, a spatial susceptible-infective-susceptible （SIS） type of epidemiological disease model with self- and cross-diffusion are investigated. We study the effect of diffusion on the stability of the endemic equilibrium with disease-induced mortality and nonlinear incidence rate, In the absence of diffusion the stationary solution stays stable but becomes unstable with respect to diffusion and that Turing instability takes place. We show that a standard （self-diffusion） system may be either stable or unstable, cross-diffusion response can stabilize an unstable standard system or decrease a ＂ihlring space （the space which the emergence of spatial patterns is holding） compared to the ~lhlring space with self-diffusion, i.e. the cross-diffusion response is an important factor that should not be ignored when pattern emerges. Numerical simulations are provided to illustrate and extend the theoretical results.
