The basic reproduction number of an infectious agent is the average number of infections one case can generate over the course of the infectious period,in a naïve,uninfected population.It is well-known that the e...The basic reproduction number of an infectious agent is the average number of infections one case can generate over the course of the infectious period,in a naïve,uninfected population.It is well-known that the estimation of this number may vary due to several methodological issues,including different assumptions and choice of parameters,utilized models,used datasets and estimation period.With the spreading of the novel coronavirus(2019-nCoV)infection,the reproduction number has been found to vary,reflecting the dynamics of transmission of the coronavirus outbreak as well as the case reporting rate.Due to significant variations in the control strategies,which have been changing over time,and thanks to the introduction of detection technologies that have been rapidly improved,enabling to shorten the time from infection/symptoms onset to diagnosis,leading to faster confirmation of the new coronavirus cases,our previous estimations on the transmission risk of the 2019-nCoV need to be revised.By using time-dependent contact and diagnose rates,we refit our previously proposed dynamics transmission model to the data available until January 29th,2020 and re-estimated the effective daily reproduction ratio that better quantifies the evolution of the interventions.We estimated when the effective daily reproduction ratio has fallen below 1 and when the epidemics will peak.Our updated findings suggest that the best measure is persistent and strict self-isolation.The epidemics will continue to grow,and can peak soon with the peak time depending highly on the public health interventions practically implemented.展开更多
Background In December 2019,an outbreak of coronavirus disease(later named as COVID-19)was identified in Wuhan,China and,later on,detected in other parts of China.Our aim is to evaluate the effectiveness of the evolut...Background In December 2019,an outbreak of coronavirus disease(later named as COVID-19)was identified in Wuhan,China and,later on,detected in other parts of China.Our aim is to evaluate the effectiveness of the evolution of interventions and self-protection measures,estimate the risk of partial lifting control measures and predict the epidemic trend of the virus in the mainland of China excluding Hubei province based on the published data and a novel mathematical model.Methods A novel COVID-19 transmission dynamic model incorporating the intervention measures implemented in China is proposed.COVID-19 daily data of the mainland of China excluding Hubei province,including the cumulative confirmed cases,the cumulative deaths,newly confirmed cases and the cumulative recovered cases between 20 January and 3 March 2020,were archived from the National Health Commission of China(NHCC).We parameterize the model by using the Markov Chain Monte Carlo(MCMC)method and estimate the control reproduction number(Rc),as well as the effective daily reproduction ratio-Re(t),of the disease transmission in the mainland of China excluding Hubei province.Results The estimation outcomes indicate that Rc is 3.36(95%CI:3.20–3.64)and Re(t)has dropped below 1 since 31 January 2020,which implies that the containment strategies implemented by the Chinese government in the mainland of China are indeed effective and magnificently suppressed COVID-19 transmission.Moreover,our results show that relieving personal protection too early may lead to a prolonged disease transmission period and more people would be infected,and may even cause a second wave of epidemic or outbreaks.By calculating the effective reproduction ratio,we prove that the contact rate should be kept at least less than 30%of the normal level by April,2020.Conclusions To ensure the pandemic ending rapidly,it is necessary to maintain the current integrated restrict interventions and self-protection measures,including travel restriction,quarantine of entry,contact tracing followed 展开更多
In the prequel to this paper we introduced eight reproducing graph models. The simple idea behind these models is that graphs grow because the vertices within reproduce. In this paper we make our models more realistic...In the prequel to this paper we introduced eight reproducing graph models. The simple idea behind these models is that graphs grow because the vertices within reproduce. In this paper we make our models more realistic by adding the idea that vertices have a finite life span. The resulting models capture aspects of systems like social networks and biological networks where reproducing entities die after some amount of time. In the 1940’s Leslie introduced a population model where the reproduction and survival rates of individuals depends upon their ages. Our models may be viewed as extensions of Leslie’s model-adding the idea of network joining the reproducing individuals. By exploiting connections with Leslie’s model we are to describe how many aspects of graphs evolve under our systems. Many features such as degree distributions, number of edges and distance structure are described by the golden ratio or its higher order generalisations.展开更多
This paper is devoted to the study of the asymptotic behavior of the principal eigenvalue and the basic reproduction ratio associated with periodic population models in a patchy environment for small and large dispers...This paper is devoted to the study of the asymptotic behavior of the principal eigenvalue and the basic reproduction ratio associated with periodic population models in a patchy environment for small and large dispersal rates.We first deal with the eigenspace corresponding to the zero eigenvalue of the connectivity matrix.Then we investigate the limiting profile of the principal eigenvalue of an associated periodic eigenvalue problem as the dispersal rate goes to zero and infinity,respectively.We further establish the asymptotic behavior of the basic reproduction ratio in the case of small and large dispersal rates.Finally,we apply these results to a periodic Ross-Macdonald patch model.展开更多
This study describes for the first time the reproductive biology of the coastal trevally(Carangoides coeruleopinnatus)(Ruppel,1830)caught from Terengganu waters,Malaysia.Monthly sample collection from April 2019 to Ma...This study describes for the first time the reproductive biology of the coastal trevally(Carangoides coeruleopinnatus)(Ruppel,1830)caught from Terengganu waters,Malaysia.Monthly sample collection from April 2019 to March 2020 was done at Pulau Kambing fish landing port in Terengganu,Malaysia.A total of 687 individuals comprise of 362 males(52.69%)ranged from 6.3 cm to 26.6 cm(mean±SD:13.2±3.84 cm)and 325 females(47.31%)ranged from 9.0 cm to 26.4 cm(mean±SD:13.9±3.34 cm)were observed.The sex ratio significantly deviated in favor of males(1:0.90)(χ^(2)=1.99).However,there are significant differences between sexes over months in June(χ^(2)=10.89),July(χ^(2)=11.91),August(χ^(2)=6.10)and September(χ^(2)=4.41).The monthly variation of the gonadosomatic index(IG)peaked between February and April for males and females,indicating its spawning period.The interpretation between condition factor(K)and hepatosomatic index(IH)showed that the energy mobilization from the body assists the gonad maturation.The batch fecundity of 42 mature females ranged from 15.7 cm to 21.4 cm,and mass was 142.6 g-333.0 g giving 20,438 to 121,829 eggs.The length at first maturity of males and females were 12.45 cm and 15.78 cm,respectively.The male reached earlier maturity than the female.This study increases the understanding of reproductive aspects of C.coeruleopinnatus for future formulation of rules and regulations for suitable fishery management in Terengganu waters.展开更多
The outbreak of COVID-19 has attracted attention from all around the world.Governments and institutions have adopted ways to fight COVID-19, but itsprevalence is still strong. The SIR model has important reference val...The outbreak of COVID-19 has attracted attention from all around the world.Governments and institutions have adopted ways to fight COVID-19, but itsprevalence is still strong. The SIR model has important reference value for thenovel coronavirus epidemic, offering both preventive measures and the ability topredict future trends. Based on an analysis of the classical epidemiological SIRmodel along with key parameters, this paper aims to analyze the patterns ofCOVID-19, to discuss potential anti-COVID-19 measures, and to explain whywe need to conduct appropriate measures against COVID-19. The use of theSIR model can play an important role in public health emergencies. Among theparameters of the SIR model, the contact ratio and the reproduction ratio arethe factors that have the potential to mitigate the consequences of COVID-19.Anti-COVID-19 measures include wearing a mask, washing one’s hands,keeping social distance, and staying at home if possible.展开更多
基金This research was funded by the National Natural Science Foundation of China(grant numbers:11631012(YX,ST),61772017(ST))by the Canada Research Chair Program(grant number:230720(JW)the Natural Sciences and Engineering Research Council of Canada(Grant number:105588-2011(JW).
文摘The basic reproduction number of an infectious agent is the average number of infections one case can generate over the course of the infectious period,in a naïve,uninfected population.It is well-known that the estimation of this number may vary due to several methodological issues,including different assumptions and choice of parameters,utilized models,used datasets and estimation period.With the spreading of the novel coronavirus(2019-nCoV)infection,the reproduction number has been found to vary,reflecting the dynamics of transmission of the coronavirus outbreak as well as the case reporting rate.Due to significant variations in the control strategies,which have been changing over time,and thanks to the introduction of detection technologies that have been rapidly improved,enabling to shorten the time from infection/symptoms onset to diagnosis,leading to faster confirmation of the new coronavirus cases,our previous estimations on the transmission risk of the 2019-nCoV need to be revised.By using time-dependent contact and diagnose rates,we refit our previously proposed dynamics transmission model to the data available until January 29th,2020 and re-estimated the effective daily reproduction ratio that better quantifies the evolution of the interventions.We estimated when the effective daily reproduction ratio has fallen below 1 and when the epidemics will peak.Our updated findings suggest that the best measure is persistent and strict self-isolation.The epidemics will continue to grow,and can peak soon with the peak time depending highly on the public health interventions practically implemented.
文摘Background In December 2019,an outbreak of coronavirus disease(later named as COVID-19)was identified in Wuhan,China and,later on,detected in other parts of China.Our aim is to evaluate the effectiveness of the evolution of interventions and self-protection measures,estimate the risk of partial lifting control measures and predict the epidemic trend of the virus in the mainland of China excluding Hubei province based on the published data and a novel mathematical model.Methods A novel COVID-19 transmission dynamic model incorporating the intervention measures implemented in China is proposed.COVID-19 daily data of the mainland of China excluding Hubei province,including the cumulative confirmed cases,the cumulative deaths,newly confirmed cases and the cumulative recovered cases between 20 January and 3 March 2020,were archived from the National Health Commission of China(NHCC).We parameterize the model by using the Markov Chain Monte Carlo(MCMC)method and estimate the control reproduction number(Rc),as well as the effective daily reproduction ratio-Re(t),of the disease transmission in the mainland of China excluding Hubei province.Results The estimation outcomes indicate that Rc is 3.36(95%CI:3.20–3.64)and Re(t)has dropped below 1 since 31 January 2020,which implies that the containment strategies implemented by the Chinese government in the mainland of China are indeed effective and magnificently suppressed COVID-19 transmission.Moreover,our results show that relieving personal protection too early may lead to a prolonged disease transmission period and more people would be infected,and may even cause a second wave of epidemic or outbreaks.By calculating the effective reproduction ratio,we prove that the contact rate should be kept at least less than 30%of the normal level by April,2020.Conclusions To ensure the pandemic ending rapidly,it is necessary to maintain the current integrated restrict interventions and self-protection measures,including travel restriction,quarantine of entry,contact tracing followed
文摘In the prequel to this paper we introduced eight reproducing graph models. The simple idea behind these models is that graphs grow because the vertices within reproduce. In this paper we make our models more realistic by adding the idea that vertices have a finite life span. The resulting models capture aspects of systems like social networks and biological networks where reproducing entities die after some amount of time. In the 1940’s Leslie introduced a population model where the reproduction and survival rates of individuals depends upon their ages. Our models may be viewed as extensions of Leslie’s model-adding the idea of network joining the reproducing individuals. By exploiting connections with Leslie’s model we are to describe how many aspects of graphs evolve under our systems. Many features such as degree distributions, number of edges and distance structure are described by the golden ratio or its higher order generalisations.
基金supported by National Natural Science Foundation of China(Grant No.11901138)the Natural Science Foundation of Shandong Province(Grant No.ZR2019QA006)supported by the National Sciences and Engineering Research Council of Canada。
文摘This paper is devoted to the study of the asymptotic behavior of the principal eigenvalue and the basic reproduction ratio associated with periodic population models in a patchy environment for small and large dispersal rates.We first deal with the eigenspace corresponding to the zero eigenvalue of the connectivity matrix.Then we investigate the limiting profile of the principal eigenvalue of an associated periodic eigenvalue problem as the dispersal rate goes to zero and infinity,respectively.We further establish the asymptotic behavior of the basic reproduction ratio in the case of small and large dispersal rates.Finally,we apply these results to a periodic Ross-Macdonald patch model.
基金the Ministry of Higher Education(MoHE),Malaysia,for funding this research under the Fundamental Research Grant Scheme(FRGS)with reference code FRGS/1/2018/WAB13/UMT/03/2.
文摘This study describes for the first time the reproductive biology of the coastal trevally(Carangoides coeruleopinnatus)(Ruppel,1830)caught from Terengganu waters,Malaysia.Monthly sample collection from April 2019 to March 2020 was done at Pulau Kambing fish landing port in Terengganu,Malaysia.A total of 687 individuals comprise of 362 males(52.69%)ranged from 6.3 cm to 26.6 cm(mean±SD:13.2±3.84 cm)and 325 females(47.31%)ranged from 9.0 cm to 26.4 cm(mean±SD:13.9±3.34 cm)were observed.The sex ratio significantly deviated in favor of males(1:0.90)(χ^(2)=1.99).However,there are significant differences between sexes over months in June(χ^(2)=10.89),July(χ^(2)=11.91),August(χ^(2)=6.10)and September(χ^(2)=4.41).The monthly variation of the gonadosomatic index(IG)peaked between February and April for males and females,indicating its spawning period.The interpretation between condition factor(K)and hepatosomatic index(IH)showed that the energy mobilization from the body assists the gonad maturation.The batch fecundity of 42 mature females ranged from 15.7 cm to 21.4 cm,and mass was 142.6 g-333.0 g giving 20,438 to 121,829 eggs.The length at first maturity of males and females were 12.45 cm and 15.78 cm,respectively.The male reached earlier maturity than the female.This study increases the understanding of reproductive aspects of C.coeruleopinnatus for future formulation of rules and regulations for suitable fishery management in Terengganu waters.
文摘The outbreak of COVID-19 has attracted attention from all around the world.Governments and institutions have adopted ways to fight COVID-19, but itsprevalence is still strong. The SIR model has important reference value for thenovel coronavirus epidemic, offering both preventive measures and the ability topredict future trends. Based on an analysis of the classical epidemiological SIRmodel along with key parameters, this paper aims to analyze the patterns ofCOVID-19, to discuss potential anti-COVID-19 measures, and to explain whywe need to conduct appropriate measures against COVID-19. The use of theSIR model can play an important role in public health emergencies. Among theparameters of the SIR model, the contact ratio and the reproduction ratio arethe factors that have the potential to mitigate the consequences of COVID-19.Anti-COVID-19 measures include wearing a mask, washing one’s hands,keeping social distance, and staying at home if possible.
