In this paper,we investigate a two-dimensional avian influenza model with Allee effect and stochasticity.We first show that a unique global positive solution always exists to the stochastic system for any positive ini...In this paper,we investigate a two-dimensional avian influenza model with Allee effect and stochasticity.We first show that a unique global positive solution always exists to the stochastic system for any positive initial value.Then,under certain conditions,this solution is proved to be stochastically ultimately bounded.Furthermore,by constructing a suitable Lyapunov function,we obtain sufficient conditions for the existence of stationary distribution with ergodicity.The conditions for the extinction of infected avian population are also analytically studied.These theoretical results are conformed by computational simulations.We numerically show that the environmental noise can bring different dynamical outcomes to the stochastic model.By scanning different noise intensities,we observe that large noise can cause extinction of infected avian population,which suggests the repression of noise on the spread of avian virus.展开更多
In this paper,the dynamic behaviors are studied for a stochastic delayed avian influenza model with mutation and temporary immunity.First,we prove the existence and uniqueness of the global positive solution for the s...In this paper,the dynamic behaviors are studied for a stochastic delayed avian influenza model with mutation and temporary immunity.First,we prove the existence and uniqueness of the global positive solution for the stochastic model.Second,we give two different thresholds R_(01)^(s) and,R_(02)^(s) and further establish the sufficient conditions of extinction and persistence in the mean for the avian-only subsystem and avian-human system,respectively.Compared with the corresponding deterministic model,the thresholds affected by the white noises are smaller than the ones of the deterministic system.Finally,numerical simulations are carried out to support our theoretical results.It is concluded that the vaccination immunity period can suppress the spread of avian influenza during poultry and human populations,while prompt the spread of mutant avian influenza in human population.展开更多
In this paper,we investigate the stochastic avian influenza model with human-to-human transmission,which is disturbed by both white and telegraph noises.First,we show that the solution of the stochastic system is posi...In this paper,we investigate the stochastic avian influenza model with human-to-human transmission,which is disturbed by both white and telegraph noises.First,we show that the solution of the stochastic system is positive and global.Furthermore,by using stochastic Lyapunov functions,we establish sufficient conditions for the existence of a unique ergodic stationary distribution.Then we obtain the conditions for extinction.Finally,numerical simulations are employed to demonstrate the analytical results.展开更多
Five models of Indonesian H274Y mutant neuralminidase type 1 (N1) were generated from the template 3CKZ by homology modeling. The template has the best similarity percentage 97% with the model sequence. The models was...Five models of Indonesian H274Y mutant neuralminidase type 1 (N1) were generated from the template 3CKZ by homology modeling. The template has the best similarity percentage 97% with the model sequence. The models was evaluated to search the best model with DOPE, 3D-profiles and PROCHECK in a good rank. The results show model 3 as a potential model to be used in the simulation with the lowest DOPE score, highest verify-3D score and from Ramachandran plots we inferred that it also shared the 1st rank with model 4 based on the 99.4% of the residues found, without Glycine and Proline, at the most favoured and additionally allowed region of both model structures.展开更多
Background: A number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and e...Background: A number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and extent desired, resulting in inefficient use of conservation resources.Such a situation presented itself in our attempt to develop waterfowl distribution models as part of a multi-disciplinary team targeting the control of the highly pathogenic H5N1 avian influenza virus in China.Methods: Faced with limited data, we built species distribution models using a habitat suitability approach for China's breeding and non-breeding(hereafter, wintering) waterfowl.An extensive review of the literature was used to determine model parameters for habitat modeling.Habitat relationships were implemented in GIS using land cover covariates.Wintering models were validated using waterfowl census data, while breeding models, though developed for many species, were only validated for the one species with sufficient telemetry data available.Results: We developed suitability models for 42 waterfowl species(30 breeding and 39 wintering) at 1 km resolution for the extent of China, along with cumulative and genus level species richness maps.Breeding season models showed highest waterfowl suitability in wetlands of the high-elevation west-central plateau and northeastern China.Wintering waterfowl suitability was highest in the lowland regions of southeastern China.Validation measures indicated strong performance in predicting species presence.Comparing our model outputs to China's protected areas indicated that breeding habitat was generally better covered than wintering habitat, and identified locations for which additional research and protection should be prioritized.Conclusions: These suitability models are the first available for many of China's waterfowl species, and have direct utility to conservation and habitat planning and prioritizing management of critically important areas, providing an example of how this approach may aid others faced with the challenge of addressing conservation issues with little data to inform decision making.展开更多
A logistic model was employed to correlate the outbreak of highly pathogenic avian influenza (HPAI) with related environmental factors and the migration of birds. Based on MODIS data of the normalized difference veget...A logistic model was employed to correlate the outbreak of highly pathogenic avian influenza (HPAI) with related environmental factors and the migration of birds. Based on MODIS data of the normalized difference vegetation index, environmental factors were considered in generating a probability map with the aid of logistic regression. A Bayesian maximum entropy model was employed to explore the spatial and temporal correlations of HPAI incidence. The results show that proximity to water bodies and national highways was statistically relevant to the occurrence of HPAI. Migratory birds, mainly waterfowl, were important infection sources in HPAI transmission. In addition, the HPAI outbreaks had high spatiotemporal autocorrelation. This epidemic spatial range fluctuated 45 km owing to different distribution patterns of cities and water bodies. Furthermore, two outbreaks were likely to occur with a period of 22 d. The potential risk of occurrence of HPAI in China's Mainland for the period from January 23 to February 17, 2004 was simulated based on these findings, providing a useful meta-model framework for the application of environmental factors in the prediction of HPAI risk.展开更多
基金This study is supported by the National Key Research and Development Program of China(2018YFA0801103)the National Natural Science Foundation of China(Grant No.12071330 to Ling Yang,Grant No.11701405 to Jie Yan).
文摘In this paper,we investigate a two-dimensional avian influenza model with Allee effect and stochasticity.We first show that a unique global positive solution always exists to the stochastic system for any positive initial value.Then,under certain conditions,this solution is proved to be stochastically ultimately bounded.Furthermore,by constructing a suitable Lyapunov function,we obtain sufficient conditions for the existence of stationary distribution with ergodicity.The conditions for the extinction of infected avian population are also analytically studied.These theoretical results are conformed by computational simulations.We numerically show that the environmental noise can bring different dynamical outcomes to the stochastic model.By scanning different noise intensities,we observe that large noise can cause extinction of infected avian population,which suggests the repression of noise on the spread of avian virus.
基金The research was supported by Ningxia Natural Science Foundation Project(2019AAC03069).
文摘In this paper,the dynamic behaviors are studied for a stochastic delayed avian influenza model with mutation and temporary immunity.First,we prove the existence and uniqueness of the global positive solution for the stochastic model.Second,we give two different thresholds R_(01)^(s) and,R_(02)^(s) and further establish the sufficient conditions of extinction and persistence in the mean for the avian-only subsystem and avian-human system,respectively.Compared with the corresponding deterministic model,the thresholds affected by the white noises are smaller than the ones of the deterministic system.Finally,numerical simulations are carried out to support our theoretical results.It is concluded that the vaccination immunity period can suppress the spread of avian influenza during poultry and human populations,while prompt the spread of mutant avian influenza in human population.
文摘In this paper,we investigate the stochastic avian influenza model with human-to-human transmission,which is disturbed by both white and telegraph noises.First,we show that the solution of the stochastic system is positive and global.Furthermore,by using stochastic Lyapunov functions,we establish sufficient conditions for the existence of a unique ergodic stationary distribution.Then we obtain the conditions for extinction.Finally,numerical simulations are employed to demonstrate the analytical results.
文摘Five models of Indonesian H274Y mutant neuralminidase type 1 (N1) were generated from the template 3CKZ by homology modeling. The template has the best similarity percentage 97% with the model sequence. The models was evaluated to search the best model with DOPE, 3D-profiles and PROCHECK in a good rank. The results show model 3 as a potential model to be used in the simulation with the lowest DOPE score, highest verify-3D score and from Ramachandran plots we inferred that it also shared the 1st rank with model 4 based on the 99.4% of the residues found, without Glycine and Proline, at the most favoured and additionally allowed region of both model structures.
基金supported by the United States Geological Survey(Ecosystems Mission Area)the National Science Foundation Small Grants for Exploratory Research(No.0713027)Wetlands International
文摘Background: A number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and extent desired, resulting in inefficient use of conservation resources.Such a situation presented itself in our attempt to develop waterfowl distribution models as part of a multi-disciplinary team targeting the control of the highly pathogenic H5N1 avian influenza virus in China.Methods: Faced with limited data, we built species distribution models using a habitat suitability approach for China's breeding and non-breeding(hereafter, wintering) waterfowl.An extensive review of the literature was used to determine model parameters for habitat modeling.Habitat relationships were implemented in GIS using land cover covariates.Wintering models were validated using waterfowl census data, while breeding models, though developed for many species, were only validated for the one species with sufficient telemetry data available.Results: We developed suitability models for 42 waterfowl species(30 breeding and 39 wintering) at 1 km resolution for the extent of China, along with cumulative and genus level species richness maps.Breeding season models showed highest waterfowl suitability in wetlands of the high-elevation west-central plateau and northeastern China.Wintering waterfowl suitability was highest in the lowland regions of southeastern China.Validation measures indicated strong performance in predicting species presence.Comparing our model outputs to China's protected areas indicated that breeding habitat was generally better covered than wintering habitat, and identified locations for which additional research and protection should be prioritized.Conclusions: These suitability models are the first available for many of China's waterfowl species, and have direct utility to conservation and habitat planning and prioritizing management of critically important areas, providing an example of how this approach may aid others faced with the challenge of addressing conservation issues with little data to inform decision making.
基金supported by the National Basic Research Program of China (2007CB714404)the National Natural Science Foundation of China (40871173)the Spe-cial Grant for the Prevention and Treatment of Infectious Diseases (2008ZX10004-012)
文摘A logistic model was employed to correlate the outbreak of highly pathogenic avian influenza (HPAI) with related environmental factors and the migration of birds. Based on MODIS data of the normalized difference vegetation index, environmental factors were considered in generating a probability map with the aid of logistic regression. A Bayesian maximum entropy model was employed to explore the spatial and temporal correlations of HPAI incidence. The results show that proximity to water bodies and national highways was statistically relevant to the occurrence of HPAI. Migratory birds, mainly waterfowl, were important infection sources in HPAI transmission. In addition, the HPAI outbreaks had high spatiotemporal autocorrelation. This epidemic spatial range fluctuated 45 km owing to different distribution patterns of cities and water bodies. Furthermore, two outbreaks were likely to occur with a period of 22 d. The potential risk of occurrence of HPAI in China's Mainland for the period from January 23 to February 17, 2004 was simulated based on these findings, providing a useful meta-model framework for the application of environmental factors in the prediction of HPAI risk.
基金supported by grants 2005B20201019 and 2004B20201028 from the Agricultural Science & Technology Project of Guangdong Provincegrants 06023011 from the Natural Science Project of Guangdong Province
