The transmission of schistosomiasis involves latent periods of infected hosts. In this paper, considering the latent periods of infected human, infected bovines and infected snails, we propose a delayed Barbour＇s mod...The transmission of schistosomiasis involves latent periods of infected hosts. In this paper, considering the latent periods of infected human, infected bovines and infected snails, we propose a delayed Barbour＇s model with two definitive hosts and define basic reproductive number. The stability of equilibria for the systems with and without time delays are both investigated. To study the impact of the latent periods on the transmission of schistosomiasis, some sensitivity analysis of the basic reproductive number on the three time delays are carried out. It is shown that the basic reproductive number decreases as the three time delays increase. Furthermore, the impact of the latent periods of infected snails on the system is stronger than that of the latent periods of infected human and infected bovines. Thus, to reduce the prevalence of schistosomiasis infection, prolonging the latent periods of infected snails by some measures could achieve better results than prolonging the latent periods of infected definitive hosts.展开更多
There are several good reasons for correlating the Nanking-loess(Hsiashu-loam)not with the deposits of the Choukoutien-stage,but with the Malan-loess.EothNanking-and Malan-loess are the last great eolian deposits in t...There are several good reasons for correlating the Nanking-loess(Hsiashu-loam)not with the deposits of the Choukoutien-stage,but with the Malan-loess.EothNanking-and Malan-loess are the last great eolian deposits in their respective areas.The land--snails found by S.Chu in the Nanking-loess,correspond to 80%to theliying gastropods,whereas the Land-snails of the Choukoution-stage studied byTeilhard and Barbour do not contain more than25%of living types.展开更多
文摘The transmission of schistosomiasis involves latent periods of infected hosts. In this paper, considering the latent periods of infected human, infected bovines and infected snails, we propose a delayed Barbour＇s model with two definitive hosts and define basic reproductive number. The stability of equilibria for the systems with and without time delays are both investigated. To study the impact of the latent periods on the transmission of schistosomiasis, some sensitivity analysis of the basic reproductive number on the three time delays are carried out. It is shown that the basic reproductive number decreases as the three time delays increase. Furthermore, the impact of the latent periods of infected snails on the system is stronger than that of the latent periods of infected human and infected bovines. Thus, to reduce the prevalence of schistosomiasis infection, prolonging the latent periods of infected snails by some measures could achieve better results than prolonging the latent periods of infected definitive hosts.
文摘There are several good reasons for correlating the Nanking-loess(Hsiashu-loam)not with the deposits of the Choukoutien-stage,but with the Malan-loess.EothNanking-and Malan-loess are the last great eolian deposits in their respective areas.The land--snails found by S.Chu in the Nanking-loess,correspond to 80%to theliying gastropods,whereas the Land-snails of the Choukoution-stage studied byTeilhard and Barbour do not contain more than25%of living types.
