In this paper, the existence of periodic solutions for a time dependent age-structured population model is studied. The averaged net reproductive number is introduced as the main parameter to determine the dynamical b...In this paper, the existence of periodic solutions for a time dependent age-structured population model is studied. The averaged net reproductive number is introduced as the main parameter to determine the dynamical behaviors of the model. The existence of a global parameterized branch of periodic solutions of the model is obtained by using the contracting mapping theorem in a periodic and continuous function space. The global stability of the trivial equilibrium is studied and a very practical stability criteria for the model is obtained. The dynamics of the linear time-periodic model is similar to that of the linear model.展开更多
This paper presents a novel analysis for the solution of nonlinear age-structured prob- lem which is of extreme importance in biological sciences. The presented model is very useful but quite complicated. Modified var...This paper presents a novel analysis for the solution of nonlinear age-structured prob- lem which is of extreme importance in biological sciences. The presented model is very useful but quite complicated. Modified variational iteration method （MVIM） coupled with auxiliary parameter is used to cope with the complexity of the model which subse- quently shows better results as compared to some existing results available in literature. Furthermore, an appropriate way is used for the identification of auxiliary parameter by means of residual function. Numerical examples are presented for the analysis of the pro- posed algorithm. Graphical results along with the discussions re-confirm the efficiency of proposed algorithm. The work proposes a new algorithm where He＇s polynomials and an auxiliary parameter are merged with correction functional. The suggested scheme is implemented on nonlinear age-structured population models. Graphs are plotted for the residual function that reflects the accuracy and convergence of the presented algorithm.展开更多
In this study, Haar wavelet method is implemented for solving the nonlinear age- structured population model which is the nonclassic type of partial differential equation associated with boundary integral equation. Th...In this study, Haar wavelet method is implemented for solving the nonlinear age- structured population model which is the nonclassic type of partial differential equation associated with boundary integral equation. This paper develops the flexibility of Haar wavelet method for reduction of the partial differential equation with nonlocal boundary conditions to an algebraic system. In fact, the simple structure of piecewise orthogonM Haar basis functions which leads to sparse matrices causes the convergence and com- putational efficiency. Some illustrative results show the reliability and accuracy of the presented method.展开更多
A nonlinear optimal control problem in the Lotka-McKendrick population model is studied.It describes rational management of age-structured farmed populations in aquaculture and indoor farms.Employing generalized funct...A nonlinear optimal control problem in the Lotka-McKendrick population model is studied.It describes rational management of age-structured farmed populations in aquaculture and indoor farms.Employing generalized functions,we prove the impulse nature of optimal harvesting.Exact analytic solutions for sustainable harvesting strategies are obtained and used to analyze the optimal dynamics of harvesting age and rotation under technological innovations.展开更多
In this paper,we establish and study a single-species logistic model with impulsive age-selective harvesting.First,we prove the ultimate boundedness of the solutions of the system.Then,we obtain conditions for the asy...In this paper,we establish and study a single-species logistic model with impulsive age-selective harvesting.First,we prove the ultimate boundedness of the solutions of the system.Then,we obtain conditions for the asymptotic stability of the trivial solution and the positive periodic solution.Finally,numerical simulations are presented to validate our results.Our results show that age-selective harvesting is more conducive to sustainable population survival than non-age-selective harvesting.展开更多
Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution.This study constructed a three-dimensional hydrodynamic model(EFDC)of the plateau l...Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution.This study constructed a three-dimensional hydrodynamic model(EFDC)of the plateau lake Erhai,China using accuracy wind field observation,runoff data and monthly algae data during 2022–2023.The model successfully reproduced the circulation characteristics of Erhai under prevailing wind directions.The results showed that the lake flow velocity in Lake Erhai is higher in winter than in summer,with lower velocities near shore particularly in the northern and central parts of the lake.There is a negative correlation between algal biomass and flow velocity(FV)in different zones,with lower FV favoring the accumulation of algal biomass,particularly for Microcystis,Dolichospermum,and Peridinium.Additionally,due to buoyancy,cyanobacteria are highly affected by wind direction and tend to accumulate in downwind regions of the prevailing wind direction.This study demonstrates that wind-induced circulation is a crucial factor affecting the spatial distribution of dominant algae populations in shallow plateau lakes with weak hydrodynamic force.Further,the risk of bloom occurrence in Lake Erhai will be higher due to the background of global climate change and the lake’s wind speed decline.In conclusion,we suggest implementing targeted zoning measures to control algal blooms and establishing stricter regulations for nitrogen and phosphorus control to counterbalance the promotion of algal bloom accumulation in low-velocity zones caused by reduced wind speed.展开更多
BACKGROUND In an era leaning toward a personalized alignment of total knee arthroplasty,coronal plane alignment of the knee(CPAK)phenotypes for each population are studied;furthermore,other possible variables affectin...BACKGROUND In an era leaning toward a personalized alignment of total knee arthroplasty,coronal plane alignment of the knee(CPAK)phenotypes for each population are studied;furthermore,other possible variables affecting the alignment,such as ankle joint alignment,should be considered.AIM To determine CPAK distribution in the North African(Egyptian)population with knee osteoarthritis and to assess ankle joint line orientation(AJLO)adaptations across different CPAK types.METHODS A cross-sectional study was conducted on patients with primary knee osteoarthritis and normal ankle joints.Radiographic parameters included the mechanical lateral distal femoral angle,medial proximal tibial angle,and the derived calculations of joint line obliquity(JLO)and arithmetic hip-knee-ankle angle(aHKA).The tibial plafond horizontal angle(TPHA)was used for AJLO assessment,where 0°is neutral(type N),<0°is varus(type A),and>0°is valgus(type B).The nine CPAK types were further divided into 27 subtypes after incorporating the three AJLO types.RESULTS A total of 527 patients(1054 knees)were included for CPAK classification,and 435 patients(870 knees and ankles)for AJLO assessment.The mean age was 57.2±7.8 years,with 79.5%females.Most knees(76.4%)demonstrated varus alignment(mean aHKA was-5.51°±4.84°)and apex distal JLO(55.3%)(mean JLO was 176.43°±4.53°).CPAK types I(44.3%),IV(28.6%),and II(10%)were the most common.Regarding AJLO,70.2%of ankles exhibited varus orientation(mean TPHA was-5.21°±6.45°).The most frequent combined subtypes were CPAK type I-A(33.7%),IV-A(21.5%),and I-N(6.9%).A significant positive correlation was found between the TPHA and aHKA(r=0.40,P<0.001).CONCLUSION In this North African cohort,varus knee alignment with apex distal JLO and varus AJLO predominated.CPAK types I,IV,and II were the most common types,while subtypes I-A,IV-A,and I-N were commonly occurring after incorporating AJLO types;furthermore,the AJLO was significantly correlated to aHKA.展开更多
In this paper, we derive a lattice model for a single species on infinite patches of one-dimensional space with that the maturation could occur at any age. The formulation involves a distribution of possible ages of m...In this paper, we derive a lattice model for a single species on infinite patches of one-dimensional space with that the maturation could occur at any age. The formulation involves a distribution of possible ages of maturation and a probability density function on which ecological assumptions are made. The following results are obtained： the existence and isotropy of the unique nonnegative solution for initial value problem, the extinction of the species provided with the non-existence of positive equilibria, and the existence of wavefronts with the wave speed c 〉 c＊.展开更多
In this paper,we are concerned with the stability for a model in the form of system of integro-partial differential equations,which governs the evolution of two competing age-structured populations.The age-specified e...In this paper,we are concerned with the stability for a model in the form of system of integro-partial differential equations,which governs the evolution of two competing age-structured populations.The age-specified environment is incorporated in the vital rates,which displays the hierarchy of ages.By a non-zero fixed-point result,we show the existence of positive equilibria.Some conditions for the stability of steady states are derived by means of semigroup method.Furthermore,numerical experiments are also presented.展开更多
The present paper deals with the periodic behaviours of an age-structured populationmodel.The period-similarity is proposed,which reveals a certain similar structure between thosepopulation models with distinct age st...The present paper deals with the periodic behaviours of an age-structured populationmodel.The period-similarity is proposed,which reveals a certain similar structure between thosepopulation models with distinct age structure.In addition,other results show that the fluctuations ofan age-structured population are closely related with the age structure.展开更多
We propose a class of new hierarchical model for the evolution of two interacting age-structured populations,which is a system of integro-partial differential equations with global feedback boundary conditions and may...We propose a class of new hierarchical model for the evolution of two interacting age-structured populations,which is a system of integro-partial differential equations with global feedback boundary conditions and may describe the interactions such as competition,cooperation and predator-prey relation.Based upon a group of natural conditions,the existence and uniqueness of solutions on infinite time interval are proved by means of fixed point and extension principle,and the continuous dependence of the solution on the initial age distribution is established.These results lay a sound basis for the investigation of stability,controllability and variable optimal control problems.展开更多
We formulate a model describing the dynamics for the spatial propagation of an SIS epidemic within a population,with age structure,living in an environment divided into two sites.An analysis of the model is given.We p...We formulate a model describing the dynamics for the spatial propagation of an SIS epidemic within a population,with age structure,living in an environment divided into two sites.An analysis of the model is given.We prove the existence of a unique disease free equilibrium (DFE)and its (local and global)stability.Further,we assume that fast infection processes and fast migration processes take place in the above-mentioned model;i.e.such processes last only a few days (less than a week).In opposition to such processes,demographic processes such as birth,death and maturation last quite a lot of years.Such a gap between the time scales gives rise to a multiple time scales model,in particular a singularly perturbed model.Through a singular perturbation analysis,based on Tikhonov theorem,we prove that for certain classes of initial conditions the nonlinear perturbed model can be approximated with very good accuracy by lower-dimensional linear models.展开更多
It analyses the Castanopsis carlesii, Camellia oleifera and Symplocos launnapopulations' status and role in the Castanopsis carlesii community basing on the study on thedominant population size structure, survival...It analyses the Castanopsis carlesii, Camellia oleifera and Symplocos launnapopulations' status and role in the Castanopsis carlesii community basing on the study on thedominant population size structure, survival curve and dynamic. It reveals the Castanopsis carlesipopulation acts as a main role in the community which maintains the stabilization and renovation ofthe community. The populations of Camellia oleifera and Symplocos laurina act as a secondaryposition. The development and succession dynamics of dominant populations is also discussed. Themanagement method is preliminary drawn out which offers a theoretical basis for the evergreenbroad-leaved forest restoration and reconstruction in the lower hilly of the west edge of theSichuan basin.展开更多
Background Cotton crop is infested by numerous arthropod pests from sowing to harvesting,causing substantial direct and indirect yield losses.Knowledge of seasonal population trends and the relative occurrence of pest...Background Cotton crop is infested by numerous arthropod pests from sowing to harvesting,causing substantial direct and indirect yield losses.Knowledge of seasonal population trends and the relative occurrence of pests and their natural enemies is required to minimize the pest population and yield losses.In the current study,analysis of the seasonal population trend of pests and natural enemies and their relative occurrence on cultivars of three cotton species in Central India has been carried out.Results A higher number and diversity of sucking pests were observed during the vegetative cotton growth stage(60 days after sowing),declining as the crop matured.With the exception of cotton jassid(Amrasca biguttula biguttula Ishida),which caused significant crop damage mainly from August to September;populations of other sucking insects seldom reached economic threshold levels(ETL)throughout the studied period.The bollworm complex populations were minimal,except for the pink bollworm(Pectinophora gossypiella Saunders),which re-emerged as a menace to cotton crops during the cotton cropping season 2017–2018 due to resistance development against Bt-cotton.A reasonably good number of predatory arthropods,including coccinellids,lacewings,and spiders,were found actively preying on the arthropod pest complex of the cotton crop during the early vegetative growth stage.Linear regression indicates a significant relationship between green boll infestations and pink bollworm moths in pheromone traps.Multiple linear regression analyse showed mean weekly weather at one-or two-week lag periods had a significant impact on sucking pest population(cotton aphid,cotton jassid,cotton whitefly,and onion thrips)fluctuation.Gossypium hirsutum cultivars RCH 2 and DCH 32,and G.barbadense cultivar Suvin were found susceptible to cotton jassid and onion thrips.Phule Dhanvantary,an G.arboreum cotton cultivar,demonstrated the highest tolerance among all evaluated cultivars against all sucking pests.Conclusion These findings have important implications for pest management in cotton crops.Susceptible cultivars warrant more attention for plant protection measures,making them more input-intensive.The choice of appropriate cultivars can help minimize input costs,thereby increasing net returns for cotton farmers.展开更多
Atrial fibrillation(AF)/atrial flutter(AFL)is the most common sustained cardiac arrhythmia.The known risk factors for developing AF/AFL include age,structural heart disease,hypertension,diabetes mellitus,or hyperthyro...Atrial fibrillation(AF)/atrial flutter(AFL)is the most common sustained cardiac arrhythmia.The known risk factors for developing AF/AFL include age,structural heart disease,hypertension,diabetes mellitus,or hyperthyroidism.This study aims to attribute the trends in AF/AFL-related mortalities over the past two decades 1999-2020 concerning race and sex and disparity among them.To the best of our knowledge,this is the first study that estimates the trends and mortality due to AF/AFL from 1999-2020 in older adults in the United States.In this 21-year analysis of mortality data,we found a constant increase in mortality rates due to AF/AFL in older adults.From 1999 to 2020,the overall mortality in older adults aged 65 and above,regardless of sex and race,is found to be almost doubled i.e.about a 50.2%increase in the number of deaths due to AF/AFL.Furthermore,other confounding risk factors such has obesity,prior myocardial infarction,inflammation,hypertension,birth weight,diabetes mellitus,hyperthyroidism,hormone replacement therapy in menopausal women increases the risk in the occurrence or recurrent occurrence of AF.展开更多
Assessing the threat status of species in response to global change is critical for biodiversity monitoring and conservation efforts.However,current frameworks,even the IUCN Red List,often neglect critical factors suc...Assessing the threat status of species in response to global change is critical for biodiversity monitoring and conservation efforts.However,current frameworks,even the IUCN Red List,often neglect critical factors such as genetic diversity and the impacts of climate and land-use changes,hindering effective conservation planning.To address these limitations,we developed an enhanced extinction risk assessment framework using Diploderma lizards as a model.This framework incorporates long-term field surveys,environmental data,and land-use information to predict distributional changes for 10 recently described Diploderma species on the Qinghai-Xizang Plateau,which hold ecological significance but remain underassessed in conservation assessment.By integrating the distribution data and genetically inferred effective population sizes(Ne),we conducted scenario analyses and used a rank-sum approach to calculate Risk ranking scores(RRS)for each species.This approach revealed significant discrepancies with the IUCN Red List assessments.Notably,D.yangi and D.qilin were identified as facing the highest extinction risk.Furthermore,D.vela,D.batangense,D.flaviceps,D.dymondi,D.yulongense,and D.laeviventre,currently classified as“Least Concern”,were found to warrant reclassification as“Vulnerable”due to considerable threat from projected range contractions.Exploring the relationship between morphology and RRS revealed that traits such as snout-vent length and relative tail length could serve as potential predictors of extinction risk,offering preliminary metrics for assessing species vulnerability when comprehensive data are unavailable.This study enhances the precision of extinction risk assessment frameworks and demonstrates their capacity to refine and update risk assessments,especially for lesser-known taxa.展开更多
Bangladesh has a denser population in comparison with many other countries. Though the rate of population increase has been regarded as a concerning issue, estimation of the population instability in the upcoming year...Bangladesh has a denser population in comparison with many other countries. Though the rate of population increase has been regarded as a concerning issue, estimation of the population instability in the upcoming years may be useful for national planning. To predict Bangladesh’s future population, this study compares the estimated populations of two popular population models, the Malthusian and the logistic population models, with the country’s census population published by BBS. We also tried to find out which model gives a better approximation for forecasting the past, present, and future population between these two models.展开更多
Objective:Keratoconus(KC)is a progressive corneal ectasia disorder,arising from a myriad of causes including genetic predispositions,environmental factors,biomechanical influences,and inflammatory reactions.This study...Objective:Keratoconus(KC)is a progressive corneal ectasia disorder,arising from a myriad of causes including genetic predispositions,environmental factors,biomechanical influences,and inflammatory reactions.This study aims to identify potential pathogenetic gene mutations in patients with sporadic KC in the Han Chinese population.Methods:Twenty-five patients with primary KC as well as 50 unrelated population matched healthy controls,were included in this study to identify potential pathogenic gene mutations among sporadic KC patients in the Han Chinese population.Sanger sequencing and whole-exome sequencing(WES)were used to analyze mutations in the zinc finger protein 469(ZNF469)gene.Bioinformatics analysis was conducted to explore the potential role of ZNF469 in KC pathogenesis.Results:Five novel heterozygous missense variants were identified in KC patients.Among them,2 compound heterozygous variants,c.8986G>C(p.E2996Q)with c.11765A>C(p.D3922A),and c.4423C>G(p.L1475V)with c.10633G>A(p.G3545R),were determined to be possible pathogenic factors for KC.Conclusion:Mutations in the ZNF469 gene may contribute to the development of KC in the Han Chinese population.These mutation sites may provide valuable information for future genetic screening of KC patients and their families.展开更多
In this paper,we investigate the periodic traveling wave solutions problem for a single population model with advection and distributed delay.By the bifurcation analysis method,we can obtain periodic traveling wave so...In this paper,we investigate the periodic traveling wave solutions problem for a single population model with advection and distributed delay.By the bifurcation analysis method,we can obtain periodic traveling wave solutions for this model under the influence of advection term and distributed delay.The obtained results indicate that weak kernel and strong kernel can both deduce the existence of periodic traveling wave solutions.Finally,we apply the main results in this paper to Logistic model and Nicholson’s blowflies model.展开更多
Lung cancer, the leading cause of cancer deaths worldwide and in China, has a 19.7% five-year survival rate due to terminal-stage diagnosis^([1-3]).Although low-dose computed tomography(CT) screening can reduce mortal...Lung cancer, the leading cause of cancer deaths worldwide and in China, has a 19.7% five-year survival rate due to terminal-stage diagnosis^([1-3]).Although low-dose computed tomography(CT) screening can reduce mortality, high false positive rates can create economic and psychological burdens.展开更多
文摘In this paper, the existence of periodic solutions for a time dependent age-structured population model is studied. The averaged net reproductive number is introduced as the main parameter to determine the dynamical behaviors of the model. The existence of a global parameterized branch of periodic solutions of the model is obtained by using the contracting mapping theorem in a periodic and continuous function space. The global stability of the trivial equilibrium is studied and a very practical stability criteria for the model is obtained. The dynamics of the linear time-periodic model is similar to that of the linear model.
文摘This paper presents a novel analysis for the solution of nonlinear age-structured prob- lem which is of extreme importance in biological sciences. The presented model is very useful but quite complicated. Modified variational iteration method （MVIM） coupled with auxiliary parameter is used to cope with the complexity of the model which subse- quently shows better results as compared to some existing results available in literature. Furthermore, an appropriate way is used for the identification of auxiliary parameter by means of residual function. Numerical examples are presented for the analysis of the pro- posed algorithm. Graphical results along with the discussions re-confirm the efficiency of proposed algorithm. The work proposes a new algorithm where He＇s polynomials and an auxiliary parameter are merged with correction functional. The suggested scheme is implemented on nonlinear age-structured population models. Graphs are plotted for the residual function that reflects the accuracy and convergence of the presented algorithm.
文摘In this study, Haar wavelet method is implemented for solving the nonlinear age- structured population model which is the nonclassic type of partial differential equation associated with boundary integral equation. This paper develops the flexibility of Haar wavelet method for reduction of the partial differential equation with nonlocal boundary conditions to an algebraic system. In fact, the simple structure of piecewise orthogonM Haar basis functions which leads to sparse matrices causes the convergence and com- putational efficiency. Some illustrative results show the reliability and accuracy of the presented method.
文摘A nonlinear optimal control problem in the Lotka-McKendrick population model is studied.It describes rational management of age-structured farmed populations in aquaculture and indoor farms.Employing generalized functions,we prove the impulse nature of optimal harvesting.Exact analytic solutions for sustainable harvesting strategies are obtained and used to analyze the optimal dynamics of harvesting age and rotation under technological innovations.
基金Supported by the National Natural Science Foundation of China(12261018)Universities Key Laboratory of Mathematical Modeling and Data Mining in Guizhou Province(2023013)。
文摘In this paper,we establish and study a single-species logistic model with impulsive age-selective harvesting.First,we prove the ultimate boundedness of the solutions of the system.Then,we obtain conditions for the asymptotic stability of the trivial solution and the positive periodic solution.Finally,numerical simulations are presented to validate our results.Our results show that age-selective harvesting is more conducive to sustainable population survival than non-age-selective harvesting.
基金supported by the Open Research Fund of Key Laboratory for Lake Pollution Control of the Ministry of Ecology and Environment(No.2024HPYKFZD04)the Fundamental Research Funds for the Central Publicinterest Scientific Institution(No.2025YSKY-04)the National Natural Science Foundation of China(Nos.U1902207 and 42207265).
文摘Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution.This study constructed a three-dimensional hydrodynamic model(EFDC)of the plateau lake Erhai,China using accuracy wind field observation,runoff data and monthly algae data during 2022–2023.The model successfully reproduced the circulation characteristics of Erhai under prevailing wind directions.The results showed that the lake flow velocity in Lake Erhai is higher in winter than in summer,with lower velocities near shore particularly in the northern and central parts of the lake.There is a negative correlation between algal biomass and flow velocity(FV)in different zones,with lower FV favoring the accumulation of algal biomass,particularly for Microcystis,Dolichospermum,and Peridinium.Additionally,due to buoyancy,cyanobacteria are highly affected by wind direction and tend to accumulate in downwind regions of the prevailing wind direction.This study demonstrates that wind-induced circulation is a crucial factor affecting the spatial distribution of dominant algae populations in shallow plateau lakes with weak hydrodynamic force.Further,the risk of bloom occurrence in Lake Erhai will be higher due to the background of global climate change and the lake’s wind speed decline.In conclusion,we suggest implementing targeted zoning measures to control algal blooms and establishing stricter regulations for nitrogen and phosphorus control to counterbalance the promotion of algal bloom accumulation in low-velocity zones caused by reduced wind speed.
基金approved by Institutional Review Board of Faculty of Medicine in Assiut University,No.04-2024-300470.
文摘BACKGROUND In an era leaning toward a personalized alignment of total knee arthroplasty,coronal plane alignment of the knee(CPAK)phenotypes for each population are studied;furthermore,other possible variables affecting the alignment,such as ankle joint alignment,should be considered.AIM To determine CPAK distribution in the North African(Egyptian)population with knee osteoarthritis and to assess ankle joint line orientation(AJLO)adaptations across different CPAK types.METHODS A cross-sectional study was conducted on patients with primary knee osteoarthritis and normal ankle joints.Radiographic parameters included the mechanical lateral distal femoral angle,medial proximal tibial angle,and the derived calculations of joint line obliquity(JLO)and arithmetic hip-knee-ankle angle(aHKA).The tibial plafond horizontal angle(TPHA)was used for AJLO assessment,where 0°is neutral(type N),<0°is varus(type A),and>0°is valgus(type B).The nine CPAK types were further divided into 27 subtypes after incorporating the three AJLO types.RESULTS A total of 527 patients(1054 knees)were included for CPAK classification,and 435 patients(870 knees and ankles)for AJLO assessment.The mean age was 57.2±7.8 years,with 79.5%females.Most knees(76.4%)demonstrated varus alignment(mean aHKA was-5.51°±4.84°)and apex distal JLO(55.3%)(mean JLO was 176.43°±4.53°).CPAK types I(44.3%),IV(28.6%),and II(10%)were the most common.Regarding AJLO,70.2%of ankles exhibited varus orientation(mean TPHA was-5.21°±6.45°).The most frequent combined subtypes were CPAK type I-A(33.7%),IV-A(21.5%),and I-N(6.9%).A significant positive correlation was found between the TPHA and aHKA(r=0.40,P<0.001).CONCLUSION In this North African cohort,varus knee alignment with apex distal JLO and varus AJLO predominated.CPAK types I,IV,and II were the most common types,while subtypes I-A,IV-A,and I-N were commonly occurring after incorporating AJLO types;furthermore,the AJLO was significantly correlated to aHKA.
基金This research is Supported by Natural Science Fundation of China and Guangdong Province(04010364).
文摘In this paper, we derive a lattice model for a single species on infinite patches of one-dimensional space with that the maturation could occur at any age. The formulation involves a distribution of possible ages of maturation and a probability density function on which ecological assumptions are made. The following results are obtained： the existence and isotropy of the unique nonnegative solution for initial value problem, the extinction of the species provided with the non-existence of positive equilibria, and the existence of wavefronts with the wave speed c 〉 c＊.
基金supported by the National Natural Science Foundation of China(11871185)the Zhejiang Provincial Nat ural Science Foundation of China(LY18A010010).
文摘In this paper,we are concerned with the stability for a model in the form of system of integro-partial differential equations,which governs the evolution of two competing age-structured populations.The age-specified environment is incorporated in the vital rates,which displays the hierarchy of ages.By a non-zero fixed-point result,we show the existence of positive equilibria.Some conditions for the stability of steady states are derived by means of semigroup method.Furthermore,numerical experiments are also presented.
文摘The present paper deals with the periodic behaviours of an age-structured populationmodel.The period-similarity is proposed,which reveals a certain similar structure between thosepopulation models with distinct age structure.In addition,other results show that the fluctuations ofan age-structured population are closely related with the age structure.
基金supported by the National Natural Science Foundation of China(Grant No.11871185)the Natural Science Foundation of Zhejiang Province(No.LY18A010010).
文摘We propose a class of new hierarchical model for the evolution of two interacting age-structured populations,which is a system of integro-partial differential equations with global feedback boundary conditions and may describe the interactions such as competition,cooperation and predator-prey relation.Based upon a group of natural conditions,the existence and uniqueness of solutions on infinite time interval are proved by means of fixed point and extension principle,and the continuous dependence of the solution on the initial age distribution is established.These results lay a sound basis for the investigation of stability,controllability and variable optimal control problems.
文摘We formulate a model describing the dynamics for the spatial propagation of an SIS epidemic within a population,with age structure,living in an environment divided into two sites.An analysis of the model is given.We prove the existence of a unique disease free equilibrium (DFE)and its (local and global)stability.Further,we assume that fast infection processes and fast migration processes take place in the above-mentioned model;i.e.such processes last only a few days (less than a week).In opposition to such processes,demographic processes such as birth,death and maturation last quite a lot of years.Such a gap between the time scales gives rise to a multiple time scales model,in particular a singularly perturbed model.Through a singular perturbation analysis,based on Tikhonov theorem,we prove that for certain classes of initial conditions the nonlinear perturbed model can be approximated with very good accuracy by lower-dimensional linear models.
文摘It analyses the Castanopsis carlesii, Camellia oleifera and Symplocos launnapopulations' status and role in the Castanopsis carlesii community basing on the study on thedominant population size structure, survival curve and dynamic. It reveals the Castanopsis carlesipopulation acts as a main role in the community which maintains the stabilization and renovation ofthe community. The populations of Camellia oleifera and Symplocos laurina act as a secondaryposition. The development and succession dynamics of dominant populations is also discussed. Themanagement method is preliminary drawn out which offers a theoretical basis for the evergreenbroad-leaved forest restoration and reconstruction in the lower hilly of the west edge of theSichuan basin.
基金Funding support for the Crop Pest Surveillance and Advisory Project(CROPSAP)。
文摘Background Cotton crop is infested by numerous arthropod pests from sowing to harvesting,causing substantial direct and indirect yield losses.Knowledge of seasonal population trends and the relative occurrence of pests and their natural enemies is required to minimize the pest population and yield losses.In the current study,analysis of the seasonal population trend of pests and natural enemies and their relative occurrence on cultivars of three cotton species in Central India has been carried out.Results A higher number and diversity of sucking pests were observed during the vegetative cotton growth stage(60 days after sowing),declining as the crop matured.With the exception of cotton jassid(Amrasca biguttula biguttula Ishida),which caused significant crop damage mainly from August to September;populations of other sucking insects seldom reached economic threshold levels(ETL)throughout the studied period.The bollworm complex populations were minimal,except for the pink bollworm(Pectinophora gossypiella Saunders),which re-emerged as a menace to cotton crops during the cotton cropping season 2017–2018 due to resistance development against Bt-cotton.A reasonably good number of predatory arthropods,including coccinellids,lacewings,and spiders,were found actively preying on the arthropod pest complex of the cotton crop during the early vegetative growth stage.Linear regression indicates a significant relationship between green boll infestations and pink bollworm moths in pheromone traps.Multiple linear regression analyse showed mean weekly weather at one-or two-week lag periods had a significant impact on sucking pest population(cotton aphid,cotton jassid,cotton whitefly,and onion thrips)fluctuation.Gossypium hirsutum cultivars RCH 2 and DCH 32,and G.barbadense cultivar Suvin were found susceptible to cotton jassid and onion thrips.Phule Dhanvantary,an G.arboreum cotton cultivar,demonstrated the highest tolerance among all evaluated cultivars against all sucking pests.Conclusion These findings have important implications for pest management in cotton crops.Susceptible cultivars warrant more attention for plant protection measures,making them more input-intensive.The choice of appropriate cultivars can help minimize input costs,thereby increasing net returns for cotton farmers.
文摘Atrial fibrillation(AF)/atrial flutter(AFL)is the most common sustained cardiac arrhythmia.The known risk factors for developing AF/AFL include age,structural heart disease,hypertension,diabetes mellitus,or hyperthyroidism.This study aims to attribute the trends in AF/AFL-related mortalities over the past two decades 1999-2020 concerning race and sex and disparity among them.To the best of our knowledge,this is the first study that estimates the trends and mortality due to AF/AFL from 1999-2020 in older adults in the United States.In this 21-year analysis of mortality data,we found a constant increase in mortality rates due to AF/AFL in older adults.From 1999 to 2020,the overall mortality in older adults aged 65 and above,regardless of sex and race,is found to be almost doubled i.e.about a 50.2%increase in the number of deaths due to AF/AFL.Furthermore,other confounding risk factors such has obesity,prior myocardial infarction,inflammation,hypertension,birth weight,diabetes mellitus,hyperthyroidism,hormone replacement therapy in menopausal women increases the risk in the occurrence or recurrent occurrence of AF.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP,2019QZKK0402)Science and Technology Plan Project of Xizang Autonomous Region to Y.Q. (XZ202201ZY0030G)National Natural Science Foundation of China (32201424 to Z.Y.L.and 31872233 to Y.Q.)。
文摘Assessing the threat status of species in response to global change is critical for biodiversity monitoring and conservation efforts.However,current frameworks,even the IUCN Red List,often neglect critical factors such as genetic diversity and the impacts of climate and land-use changes,hindering effective conservation planning.To address these limitations,we developed an enhanced extinction risk assessment framework using Diploderma lizards as a model.This framework incorporates long-term field surveys,environmental data,and land-use information to predict distributional changes for 10 recently described Diploderma species on the Qinghai-Xizang Plateau,which hold ecological significance but remain underassessed in conservation assessment.By integrating the distribution data and genetically inferred effective population sizes(Ne),we conducted scenario analyses and used a rank-sum approach to calculate Risk ranking scores(RRS)for each species.This approach revealed significant discrepancies with the IUCN Red List assessments.Notably,D.yangi and D.qilin were identified as facing the highest extinction risk.Furthermore,D.vela,D.batangense,D.flaviceps,D.dymondi,D.yulongense,and D.laeviventre,currently classified as“Least Concern”,were found to warrant reclassification as“Vulnerable”due to considerable threat from projected range contractions.Exploring the relationship between morphology and RRS revealed that traits such as snout-vent length and relative tail length could serve as potential predictors of extinction risk,offering preliminary metrics for assessing species vulnerability when comprehensive data are unavailable.This study enhances the precision of extinction risk assessment frameworks and demonstrates their capacity to refine and update risk assessments,especially for lesser-known taxa.
文摘Bangladesh has a denser population in comparison with many other countries. Though the rate of population increase has been regarded as a concerning issue, estimation of the population instability in the upcoming years may be useful for national planning. To predict Bangladesh’s future population, this study compares the estimated populations of two popular population models, the Malthusian and the logistic population models, with the country’s census population published by BBS. We also tried to find out which model gives a better approximation for forecasting the past, present, and future population between these two models.
基金supported by the National Natural Science Foundation(82271057)the Natural Science Foundation of Hunan Province(2023JJ30818),China。
文摘Objective:Keratoconus(KC)is a progressive corneal ectasia disorder,arising from a myriad of causes including genetic predispositions,environmental factors,biomechanical influences,and inflammatory reactions.This study aims to identify potential pathogenetic gene mutations in patients with sporadic KC in the Han Chinese population.Methods:Twenty-five patients with primary KC as well as 50 unrelated population matched healthy controls,were included in this study to identify potential pathogenic gene mutations among sporadic KC patients in the Han Chinese population.Sanger sequencing and whole-exome sequencing(WES)were used to analyze mutations in the zinc finger protein 469(ZNF469)gene.Bioinformatics analysis was conducted to explore the potential role of ZNF469 in KC pathogenesis.Results:Five novel heterozygous missense variants were identified in KC patients.Among them,2 compound heterozygous variants,c.8986G>C(p.E2996Q)with c.11765A>C(p.D3922A),and c.4423C>G(p.L1475V)with c.10633G>A(p.G3545R),were determined to be possible pathogenic factors for KC.Conclusion:Mutations in the ZNF469 gene may contribute to the development of KC in the Han Chinese population.These mutation sites may provide valuable information for future genetic screening of KC patients and their families.
基金Supported by the National Natural Science Foundation of China(12261050)Science and Technology Project of Department of Education of Jiangxi Province(GJJ2201612 and GJJ211027)Natural Science Foundation of Jiangxi Province of China(20212BAB202021)。
文摘In this paper,we investigate the periodic traveling wave solutions problem for a single population model with advection and distributed delay.By the bifurcation analysis method,we can obtain periodic traveling wave solutions for this model under the influence of advection term and distributed delay.The obtained results indicate that weak kernel and strong kernel can both deduce the existence of periodic traveling wave solutions.Finally,we apply the main results in this paper to Logistic model and Nicholson’s blowflies model.
基金supported by the National Natural Science Foundation of China(grant numbers 82204127 and 72204172)。
文摘Lung cancer, the leading cause of cancer deaths worldwide and in China, has a 19.7% five-year survival rate due to terminal-stage diagnosis^([1-3]).Although low-dose computed tomography(CT) screening can reduce mortality, high false positive rates can create economic and psychological burdens.
