Rumor is an important form of social interaction, and its spreading has a significant impact on people’s lives. In the age of Web, people are using electronic media more frequently than ever before, ...and blog has become one of the main online social interactions. Therefore, it is essential to learn the evolution mechanism of rumor spreading on homogeneous network in consideration of the forgetting mechanism of spreaders. Here we study a rumor spreading model on an online social blogging platform called LiveJournal. In comparison with the Susceptible–Infected–Removed (SIR) model, we provide a more detailed and realistic description of rumor spreading process with combination of forgetting mechanism and the SIR model of epidemics. A mathematical model has been presented and numerical solutions of the model were used to analyze the impact factors of rumor spreading, such as the average degree, forgetting rate and stifling rate. Our results show that there exist a threshold of the average degree of LiveJournal and above which the influence of rumor reaches saturation. Forgetting mechanism and stifling rate exert great influence on rumor spreading on online social network. The analysis results can guide people’s behaviors in view of the theoretical and practical aspects.
► We presented the structure chart of rumor spreading process on LiveJournal. ► New constraint of spreading rules is considered. ► We studied how average degree, forgetting and stifling rate influence spreading. ► The final fraction of nodes depends greatly on the average degree of LiveJournal.
Coronavirus disease-2019 (COVID-19) is a viral infection that rose in a city in the Chinese province of Hubei, Wuhan. The world did not wait too long until the virus spread to reach Europe, Africa, ...and America to be a global pandemic. Due to the lack of information about the behaviour of the virus, several prediction models are in use all over around the world for decision making and taking precautionary actions. Therefor, in this paper, a new model named MSIR based on SIR model is proposed. The model is used to predict the spread of the disease in three cities Riyadh, Hufof and Jeddah in the kingdom of Saudi Arabia. Also the estimation of disease propagation with and without containment measure is carried out. We think that the results could be used to enhance the predictability of the pandemic outbreaks in other cities and to build long term artificial intelligence prediction model.
Marine Protected Areas (MPAs) are increasingly advocated for the protection of key functional groups like elasmobranchs (sharks and rays). However, substantial uncertainty remains regarding which ...species can benefit from MPAs, crucial information to support policy and management plans. Using Baited Remote Underwater Video Surveys (BRUVS), a study was conducted on Sir Bu Nair Island in the United Arab Emirates encompassing a range of depths and habitat types within the MPA borders. A total of 96 deployments with 117 video hours recorded were analysed to assess the diversity, relative abundance and habitat associations of elasmobranchs. Surveys recorded 40 elasmobranchs including two species of sharks and seven species of rays. Overall, catch per unit effort for elasmobranchs was slightly higher overall, lower for sharks, and higher for rays compared to a similar study using BRUVS across United Arab Emirates waters. Two reef-associated species in early life stages, blacktip reef shark (Carcharhinus melanopterus) and Halavi guitarfish (Glaucostegus halavi) listed as Near Threatened and Critically Endangered on the IUCN Red List of Threatened Species respectively showed the highest frequency of occurrence of species representing 44.4% of all sightings. These results show the value of this MPA in protecting critical habitats for elasmobranchs while suggesting its limitation in protecting adult life stages and other elasmobranchs with wider ranging movements that are likely threatened by fishing in waters adjacent to the MPA. This study provides critical information to support the development of a Sir Bu Nair management plan and highlights further research needs around the island. Finally, it reinforces the need of additional management measures to protect and promote the recovery of elasmobranchs in the United Arab Emirates and broader Arabian Gulf.
•We assessed the diversity and relative abundance of sharks and rays.•Baited Remote Underwater Video Surveys were deployed at Sir Bu Nair island, UAE.•Overall, Catch Per Unit Effort was slightly higher than similar studies in the UAE.•Two reef-associated species in early life stages were the most abundant species.•This MPA provides limited protection to elasmobranchs.
Under the dispute between China and the United States, the international field of public opinion is dominated by increasing tensions, and the network rumors triggered by the COVID-19 epidemic are ...intensifying. In view of the above-mentioned context, this paper focuses on the development and the evolution process of public opinions. Since the evolution of public opinion is often accompanied by the spread and diffusion of information, this paper combines the process of information diffusion with the development process of polarization behavior, and brings in the dynamic network and the timeliness factor of public opinion dissemination, so as to better explore the polarization process of public opinion under the dynamic network. Then, this paper focuses on the analysis of the parameters of the model and through the dynamic adjustment of parameters, finding out the main factors that affect the trend and development of network public opinion. In addition, this paper introduces an actual case, and takes the actual case data as the support to demonstrate the reliability and practical application value of the model. Finally, based on the simulation results and analysis of actual cases, this paper puts forward the corresponding preventive measures to alleviate the polarization behavior of the group.
In this paper, we consider an impulsive SIR model with incidence rate stochastically perturbed. First, we prove the existence and uniqueness of the global positive solution by constructing the ...equivalent system without impulse. Second, we obtain a sufficient condition which determines epidemic to extinct. Then we demonstrate the existence and global attraction of the boundary periodic solution under the certain condition. Finally, we present a sufficient condition which allows the existence of a positive periodic solution.
•A stochastic SIR epidemic model under pulse vaccination is studied.•We establish sufficient conditions for extinction of the diseases.•We show the existence and global attraction of the disease-free periodic solution under certain condition.•We establish a sufficient condition which allows the existence of a positive periodic solution which means the infection will persist.
Abstract
We examine several extensions to the basic Susceptible-Infected-Recovered model, which are able to induce recurrent outbreaks (the basic Susceptible-Infected-Recovered model by itself does ...not exhibit recurrent outbreaks). We first analyse how slow seasonal variations can destabilise the endemic equilibrium, leading to recurrent outbreaks. In the limit of slow immunity loss, we derive asymptotic thresholds that characterise this transition. In the outbreak regime, we use asymptotic matching to obtain a two-dimensional discrete map which describes outbreak times and strength. We then analyse the resulting map using linear stability and numerics. As the frequency of forcing is increased, the map exhibits a period-doubling route to chaos which alternates with periodic outbreaks of increasing frequency. Other extensions that can lead to recurrent outbreaks include the addition of noise, state-dependent variation and fine-graining of model classes.
Optimal Dynamic Control of an Epidemic
We analyze how to optimally engage in social distancing in order to minimize the spread of an infectious disease. We identify conditions under which any optimal ...policy first engages in increasingly more social distancing and subsequently decreases its intensity. We show that an optimal policy might substantially delay measures that decrease the transmission rate to create herd immunity and that engaging in social distancing suboptimally early can increase the number of fatalities. Finally, we find that optimal social distancing can be an effective measure to reduce the death rate of a disease.
We analyze how to optimally engage in social distancing in order to minimize the spread of an infectious disease. We identify conditions under which any optimal policy is single peaked (i.e., first engages in increasingly more social distancing and subsequently decreases its intensity). We show that an optimal policy might substantially delay measures that decrease the transmission rate to create herd immunity and that engaging in social distancing suboptimally early can increase the number of fatalities. Finally, we find that optimal social distancing can be an effective measure to reduce the death rate of a disease.
Funding:
P. Strack was supported by a Sloan Fellowship.
The severe acute respiratory syndrome COVID-19 has been in the center of the ongoing global health crisis in 2020. The high prevalence of mild cases facilitates sub-notification outside hospital ...environments and the number of those who are or have been infected remains largely unknown, leading to poor estimates of the crude mortality rate of the disease. Here we use a simple model to describe the number of accumulated deaths caused by COVID-19. The close connection between the proposed model and an approximate solution of the SIR model provides estimates of epidemiological parameters. We find values for the crude mortality between 10−4 and 10−3 which are lower than estimated numbers obtained from laboratory-confirmed patients. We also calculate quantities of practical interest such as the basic reproduction number and subsequent increment after relaxation of lockdown and other control measures.
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