Current hyperelastic constitutive models of hydrogels face difficulties in capturing the stress-strain behaviors of hydrogels under extremely large deformation because the effect of non-affine deformation of the polym...Current hyperelastic constitutive models of hydrogels face difficulties in capturing the stress-strain behaviors of hydrogels under extremely large deformation because the effect of non-affine deformation of the polymer network inside is ambiguous.In this work,we construct periodic random network(PRN)models for the effective polymer network in hydrogels and investigate the non-affine deformation of polymer chains intrinsically originates from the structural randomness from bottom up.The non-affine deformation in PRN models is manifested as the actual stretch of polymer chains randomly deviated from the chain stretch predicted by affine assumption,and quantified by a non-affine ratio of each polymer chain.It is found that the non-affine ratios of polymer chains are closely related to bulk deformation state,chain orientation,and initial chain elongation.By fitting the non-affine ratio of polymer chains in all PRN models,we propose a non-affine constitutive model for the hydrogel polymer network based on micro-sphere model.The stress-strain curves of the proposed constitutive models under uniaxial tension condition agree with the simulation results of different PRN models of hydrogels very well.展开更多
Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials（tailings） are produced, which are typically stored in large tailing po...Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials（tailings） are produced, which are typically stored in large tailing ponds. Thickened Tailings Disposal（TTD） is an alternative to conventional tailings ponds. In TTD, a considerable amount of water is extracted from the tailings before their deposition. Once a thickened tailings layer is deposited, it loses water and it shrinks, forming a relatively regular structure of tailings blocks with vertical cracks in between, which are then filled up with ＂fresh＂ tailings once the new upper layer is deposited. The dynamic response of a representative column of this complex structure made out of tailings blocks with softer material in between was analyzed using a periodic half-space finite element model. The tailings＇ behavior was modeled using an elasto-plastic multi-yielding constitutive model, and Chilean earthquake records were used for the seismic analyses. Special attention was given to the liquefaction potential evaluation of TTD.展开更多
Electron-diffraction pattern with 'tenfold rotational symmetry' of Al-Fe alloyphase is assumed to be produced by periodic structure. One 3D periodic structure is presentedbased on so-called C polyhedra. The st...Electron-diffraction pattern with 'tenfold rotational symmetry' of Al-Fe alloyphase is assumed to be produced by periodic structure. One 3D periodic structure is presentedbased on so-called C polyhedra. The structure can be used as atomic model to describethe Al-Fe alloy phase. The Fourier transform patterns of the model are in good agreementwith the corresponding electron-diffraction patterns. Several other models with' tenfold symmetry' Fourier transform patterns have briefly been mentioned.展开更多
Rank-1 attractors play a vital role in biological systems and the circuit systems.In this paper,we consider a periodically kicked Chua model with two delays in a circuit system.We first analyze the local stability of ...Rank-1 attractors play a vital role in biological systems and the circuit systems.In this paper,we consider a periodically kicked Chua model with two delays in a circuit system.We first analyze the local stability of the equilibria of the Chua system and obtain the existence conditions of supercritical Hopf bifurcations.Then,we derive some explicit formulas about Hopf bifurcation,which could help us find the form of Hopf bifurcation and the stability of bifurcating period solutions through the Hassards method.Also,we show that rank-1 chaos occurs when the Chua model with two delays undergoes a supercritical Hopf bifurcation and encounters a periodic kick,which shows the effect of two delays on the circuit system.Finally,we illustrate the theoretical analysis by simulations and try to explain the mechanism of delay in our system.展开更多
Periodic Anderson model is one of the most important models in the field of strongly correlated electrons. With the recent developed numerical method density matriX embedding theory, we study the ground state properti...Periodic Anderson model is one of the most important models in the field of strongly correlated electrons. With the recent developed numerical method density matriX embedding theory, we study the ground state properties of the periodic Anderson model on a two-dimensional square lattice. We systematically investigate the phase diagram away from half filling. We find three different phases in this region, which are distinguished by the local moment and the spin-spin correlation functions. The phase transition between the two antiferromagnetic phases is of first order. It is the so-called Lifshitz transition accompanied by a reconstruction of the Fermi surface. As the filling is close to half filling, there is no difference between the two antiferromagnetic phases. From the results of the spin-spin correlation, we find that the Kondo singlet is formed even in the antiferromagnetic phase.展开更多
A stochastic model is developed to predict the peniodic operation performance ofthe continuous counter-current adsorption process. The model takes into account theeffects of random backmixing of particles, axial dispe...A stochastic model is developed to predict the peniodic operation performance ofthe continuous counter-current adsorption process. The model takes into account theeffects of random backmixing of particles, axial dispersion of liquid phase, liquid- film mass transfer, intraparticle diffusion and panticle shape, and can revealclearly the behavior of solid and liquid phase in adsorption process. The simulation results agree with the experimental data rather well.展开更多
Transgenic mice carrying mutations that cause Autism Spectrum Disorders（ASDs） continue to be valuable for determining the molecular underpinnings of the disorders. Recently, researchers have taken advantage of such ...Transgenic mice carrying mutations that cause Autism Spectrum Disorders（ASDs） continue to be valuable for determining the molecular underpinnings of the disorders. Recently, researchers have taken advantage of such models combined with Cre-lox P and similar systems to manipulate gene expression over space and time. Thus, a clearer picture is starting to emerge of the cell types, circuits, brain regions, and developmental time periods underlying ASDs. ASD-causing mutations have been restricted to or rescued speci？cally in excitatory or inhibitory neurons, different neurotransmitter systems, and cells speci？c to the forebrain or cerebellum. In addition,mutations have been induced or corrected in adult mice,providing some evidence for the plasticity and reversibility of core ASD symptoms. The limited availability of Cre lines that are highly speci？c to certain cell types or time periods provides a challenge to determining the cellular and circuitry bases of autism, but other technological advances may eventually overcome this obstacle.展开更多
Magnetic adatoms in the honeycomb lattice have received tremendous attention due to the interplay between Ruderman-Kittel-Kasuya-Yosida interaction and Kondo coupling leading to very rich physics. Here we study the co...Magnetic adatoms in the honeycomb lattice have received tremendous attention due to the interplay between Ruderman-Kittel-Kasuya-Yosida interaction and Kondo coupling leading to very rich physics. Here we study the competition between the antiferromagnetism and Kondo screening of local moments by the conduction electrons on the honeycomb lattice using the determinant quantum Monte Carlo method. While changing the interband hybridization V, we systemat- ically investigate the antiferromagnetic-order state and the Kondo singlet state transition, which is characterized by the behavior of the local moment, antiferromagnetic structure factor, and the short range spin-spin correlation. The evolution of the single particle spectrum are also calculated as a function of hybridization V, we find that the system presents a small gap in the antiferromagnetic-order region and a large gap in the Kondo singlet region in the Fermi level. We also find that the localized and itinerant electrons coupling leads to the midgap states in the conduction band in the Fermi level at very small V. Moreover, the formation of antiferromagnetic order and Kondo singlet are studied as on-site interaction U or temperature T increasing, we have derived the phase diagrams at on-site interaction U （or temperature T） and hybridization V plane.展开更多
This paper is concerned with interactional models for adults of two species delayed by their mature periods. The existence and local stability of equilibria are discussed thoroughly for competitive systems, cooperativ...This paper is concerned with interactional models for adults of two species delayed by their mature periods. The existence and local stability of equilibria are discussed thoroughly for competitive systems, cooperative systems and predator-prey systems, respectively. For systems with interaction of competition and cooperation, it is found that the two populations are uniformly persistent if the positive equilibrium is stable. For predator-prey interaction, however, some further conditions are needed to guarantee the persistence of the systems.展开更多
The greatest risks to mammalian pregnancy occur during the peri-implantation period (passage through the uterotubal junction, blastulation, zona shedding, embryonic signaling and recognition, blastocyst attachment, po...The greatest risks to mammalian pregnancy occur during the peri-implantation period (passage through the uterotubal junction, blastulation, zona shedding, embryonic signaling and recognition, blastocyst attachment, postattachment events initiating placentation). Conventional markers and screening methods do not provide the means to clarify the relationship between exposure of a reproductively competent woman to a xenobiotic compound and the specific error in the functional expression of an embryogenetic process identified by impairment or deletion of that process. Laboratory models which provide the flexibility of in vitro culture methods and allow integration of cellular and molecular techniques have identified cell-specific, stage-specific markers that could focus on the mechanism of xenobiotic action. In vitro models have been used to define postattachment trophoblast cell differentiation. Trophoblast specific peptide hormones prove to be valid markers of established pregnancy. They provide no assessment of the risk to the embryo during the peri-implantation period. The relationship between developmental time of exposure and risk is discussed in terms of trophoblast differentiation.展开更多
There are many cases within epidemiology where infections compete to persist within a population.In studying models for such cases,one of the goals is to determine which infections can invade a population and persist ...There are many cases within epidemiology where infections compete to persist within a population.In studying models for such cases,one of the goals is to determine which infections can invade a population and persist when other infections are already resident within the population.Invasion reproductive numbers(IRN),which are tied to the stability of boundary endemic equilibria,can address this question.By reinterpreting resident infections epidemiologically,this study extends methods for finding IRNs to periodic systems,and presents some examples which illustrate the often complex computations required.Results identify conditions under which a simple time-average can be used to derive IRNs,and apply the methods to examine how seasonal fluctuations in influenza incidence facilitate the year-round persistence of bacterial respiratory infections.展开更多
Dynamical behaviors of a siocluustic periodic SIRS epidemic model with time delay are investigated.By constructing suitable Lyapunov functions and applying Ito's formula,the existence of the global positive soluti...Dynamical behaviors of a siocluustic periodic SIRS epidemic model with time delay are investigated.By constructing suitable Lyapunov functions and applying Ito's formula,the existence of the global positive solution and the property of stochastically ultimate boundedness of model(1.1)are proved.Moreover,the extinction and the persistence of the disease are established.The results are verified by numerical simulations.展开更多
This paper considers the optimal investment problem for an insurer in the sense of maximizing the adjustment coefficient of the risk process.The authors propose a modified periodic risk model in which the periodic ris...This paper considers the optimal investment problem for an insurer in the sense of maximizing the adjustment coefficient of the risk process.The authors propose a modified periodic risk model in which the periodic risk process is perturbed by a standard Brownian motion.The insurer can invest in multiple risky assets and one risk-free asset and the correlations between the risky assets and the risk process are considered.Optimal strategy is obtained explicitly,which is a function of time and related to the risk process.The effects of market parameters on the optimal strategy are discussed and a numerical example is also given.展开更多
In this paper we seek the solutions of the time dependent Ginzburg-Landau model for type-Ⅱ superconductors such that the associated physical observables are spatially periodic with respect to some lattice whose basic...In this paper we seek the solutions of the time dependent Ginzburg-Landau model for type-Ⅱ superconductors such that the associated physical observables are spatially periodic with respect to some lattice whose basic lattice cell is not necessarily rectangular. After appropriately foring the gange, the model can be formulated as a system of nonlinear parabolic partial differential equations with quasi-periodic boundary conditions. We first give some results concerning the existence, uniqueness and regularity of solutions and then we propose a semiimplicit finite element scheme solving the system of nonlinear partial dmerential equations and show the optimal error estimates both in the L2 and energy norm.We also report on some numerical results at the end of the paper.展开更多
This is a very attractive article. It combines fascinating new methodology with a most interesting dataset, and a highly motivating presentation. However, despite the many
The authors are to be congratulated for an innovative paper in terms of both modelling methodology and subject matter significance. The analysis of short time series is known to be
Background:Asthma imposes a large healthcare burden in China and the United States(US).However,the trends of asthma mortality and the relative risk factors have not been comparatively analyzed between the countries.Th...Background:Asthma imposes a large healthcare burden in China and the United States(US).However,the trends of asthma mortality and the relative risk factors have not been comparatively analyzed between the countries.The aim of this study was to compare the mortality and risk factors between China and the US.Methods:The deaths,and mortality rates of asthma in China and the US during 1990–2019 were obtained from the Global Burden of Disease Study 2019.The age–period–cohort model was used to estimate these mortality rates based on a log-linear scale with additive age,period,and cohort effects.The population attributable fractions of risk factors for asthma were estimated.Results:In 1990–2019,the asthma mortality rate was higher in China than in the US.The crude and age-standardized asthma mortality rates trended downward in both China and the US from 1990 to 2019.The decline in mortality was more obvious in China.Mortality gap between the two countries was narrowing.A sex difference in asthma mortality was observed with higher mortality in males in China and females in the US.The age effects showed that mortality increased with age in adults older than 20 years,particularly in the elderly.Downward trends were generally observed in the period and cohort rate ratios in both countries,with China experiencing a more obvious decrease.Smoking and high body mass index(BMI)were the leading risk factors for asthma mortality in China and the US,respectively.Mortality attributable to occupational asthmagens and smoking decreased the most in China and the US,respectively.Conclusions:In 1990–2019,the asthma mortality rate was higher in China than in the US;however,the mortality gap has narrowed.Mortality increased with age in adults.The improvements in asthma death risk with period and birth cohort were more obvious in China than in the US.Smoking,high BMI,and aging are major health problems associated with asthma control.The role of occupational asthmagens in asthma mortality underscores the importance of management and prevention of occupational asthma.展开更多
Background Food-borne trematodiases(FBTs),mainly encompassing clonorchiasis,fascioliasis,fasciolopsiasis,opisthorchiasis,and paragonimiasis,is a neglected public health problem,particularly in the WHO South-East Asia ...Background Food-borne trematodiases(FBTs),mainly encompassing clonorchiasis,fascioliasis,fasciolopsiasis,opisthorchiasis,and paragonimiasis,is a neglected public health problem,particularly in the WHO South-East Asia and the Western Pacific regions.This study evaluates the global,regional,and national disease burden of FBTs from 1990 to 2021 and projects trends to 2030,underscore the need for targeted prevention and control.Methods Using the Global Burden of Disease 2021 database,the crude and the age-standardized prevalence rate(ASPR)and age-standardized prevalence disability-adjusted life years rate(ASDR)of FBTs at the global,regional and national level from 1990 to 2021 were described.The pivotal years of trend changes were identified using joinpoint regression analysis.The effects of age,period,cohort on FBTs prevalence and correlation with the sociode-mographic index(SDI)was analyzed.Finally,the worldwide disability-adjusted life years(DALYs)for FBTs,projected up to 2030 using the Bayesian age-period-cohort model,were analyzed.Results In 2021,44,466,329 FBTs cases[95%uncertainty interval(UI):40,017,217,50,034,921],and 998,028 DALYs[95%UI:569,766,1,638,112]were estimated across 17 countries.The Western Pacific region exhibited the highest ASPR and ASDR,with the values of 1649.26(95%UI:1461.95,1881.64)and 36.54(95%UI:19.77,64.16),respectively.From 1990 to 2021,Lao PDR,Thailand,and the Philippines showed the most substantial declines in FBTs,while Kazakhstan had the largest average annual percentage change in DALYs(-6.60,95%UI:-7.10,-6.10).High-middle and middle SDI countries exhibited higher burden,with ASDR values of 28.03(95%UI:15.41,48.73)and 16.63(95%UI:9.32,27.68),respectively.The disease burden was greater among males,peaking in the 50-59 age group.The projected ASDR in 2030 is 13.10 for males and 8.40 for females.Conclusions FBTs remain a public health threat,with the global ASDR projected to remain stable,showing only a slight decrease by 2030.Low-income countries face ambiguous mortality rates and underestimated disease burdens,highlighting the need for improved surveillance.To achieve the 2030 NTD goal,comprehensive surveillance and integrated strategies derived using a One Health approach should be prioritized to control FBTs effectively.展开更多
The analysis of the relationship between sea ice in Arctic and Antarctic, and the Southern Oscillation Index (SOI) variation on the temporal scale of month, season and year is made in this paper. The negative correlat...The analysis of the relationship between sea ice in Arctic and Antarctic, and the Southern Oscillation Index (SOI) variation on the temporal scale of month, season and year is made in this paper. The negative correlation between sea ice in Arctic and the SOI. and the positive correlation between sea ice in Antarctic and the SOI are found. The variation of sea ice in Antarctic Pacific seems to play an important role in the influence to atmosphere. Their nonlinear relationships present more strongly than the linear relationship between them. The relationship between sea ice in Arctic and Antarctic and the SOI in the early stage is investigated. Their variation shows periodic phenomena. The maximum correlation is used to build the model for forecasting the variation of the SOI on the condition of the sea ice in Arctic and Antarctic. The explained variance of the simulated series is greater than 0.90. There exists a 17-month period in the relationship between sea ice in Arctic and Antarctic and SOI. The existing of the common factor with larger scale is discussed in this paper.展开更多
Singular spectrum analysis （SSA） is a technique that decomposes a time series into a set of components, such as, trend, harmonics, and residuals. Leaving out the residual components and adding up the others, the tim...Singular spectrum analysis （SSA） is a technique that decomposes a time series into a set of components, such as, trend, harmonics, and residuals. Leaving out the residual components and adding up the others, the time series can be smoothed. This procedure has been used to model Brazilian electricity consumption and flow series. The PAR（p）, periodic autoregressive models, has been broadly used in modelling energy series in Brazil. This paper presents an approach of this decomposition method, by fitting the PAR（p）, considering its multivariate version known as multivariate SSA （MSSA）. The method was applied to a vector of two wind speed series recorded at two locations in the Brazilian Northeast region. The obtained results, when compared to the univariate decomposition of each series, were far superior, showing that the spatial correlation between the two series were considered by MSSA decomposition stage.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12202339 and 12172273)Xi’an Jiaotong University Tang Scholar.
文摘Current hyperelastic constitutive models of hydrogels face difficulties in capturing the stress-strain behaviors of hydrogels under extremely large deformation because the effect of non-affine deformation of the polymer network inside is ambiguous.In this work,we construct periodic random network(PRN)models for the effective polymer network in hydrogels and investigate the non-affine deformation of polymer chains intrinsically originates from the structural randomness from bottom up.The non-affine deformation in PRN models is manifested as the actual stretch of polymer chains randomly deviated from the chain stretch predicted by affine assumption,and quantified by a non-affine ratio of each polymer chain.It is found that the non-affine ratios of polymer chains are closely related to bulk deformation state,chain orientation,and initial chain elongation.By fitting the non-affine ratio of polymer chains in all PRN models,we propose a non-affine constitutive model for the hydrogel polymer network based on micro-sphere model.The stress-strain curves of the proposed constitutive models under uniaxial tension condition agree with the simulation results of different PRN models of hydrogels very well.
基金National Research Center for Integrated Natural Disaster Management,CONICYT/FONDAP/15110017
文摘Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials（tailings） are produced, which are typically stored in large tailing ponds. Thickened Tailings Disposal（TTD） is an alternative to conventional tailings ponds. In TTD, a considerable amount of water is extracted from the tailings before their deposition. Once a thickened tailings layer is deposited, it loses water and it shrinks, forming a relatively regular structure of tailings blocks with vertical cracks in between, which are then filled up with ＂fresh＂ tailings once the new upper layer is deposited. The dynamic response of a representative column of this complex structure made out of tailings blocks with softer material in between was analyzed using a periodic half-space finite element model. The tailings＇ behavior was modeled using an elasto-plastic multi-yielding constitutive model, and Chilean earthquake records were used for the seismic analyses. Special attention was given to the liquefaction potential evaluation of TTD.
文摘Electron-diffraction pattern with 'tenfold rotational symmetry' of Al-Fe alloyphase is assumed to be produced by periodic structure. One 3D periodic structure is presentedbased on so-called C polyhedra. The structure can be used as atomic model to describethe Al-Fe alloy phase. The Fourier transform patterns of the model are in good agreementwith the corresponding electron-diffraction patterns. Several other models with' tenfold symmetry' Fourier transform patterns have briefly been mentioned.
基金supported by the National Natural Science Foundation of China(Grant Nos.11772291 and 12002297)Youth Talent Support Project of Henan,China(Grant No.2020HYTP012)+1 种基金Basic Research Project of Universities in Henan Province,China(Grant No.21zx009)Program for Science&Technology Innovation Talents in Universities of Henan Province,China(Grant No.22HASTIT018)。
文摘Rank-1 attractors play a vital role in biological systems and the circuit systems.In this paper,we consider a periodically kicked Chua model with two delays in a circuit system.We first analyze the local stability of the equilibria of the Chua system and obtain the existence conditions of supercritical Hopf bifurcations.Then,we derive some explicit formulas about Hopf bifurcation,which could help us find the form of Hopf bifurcation and the stability of bifurcating period solutions through the Hassards method.Also,we show that rank-1 chaos occurs when the Chua model with two delays undergoes a supercritical Hopf bifurcation and encounters a periodic kick,which shows the effect of two delays on the circuit system.Finally,we illustrate the theoretical analysis by simulations and try to explain the mechanism of delay in our system.
基金Project supported by the National Natural Science Foundation of China(Grant No.11504023)
文摘Periodic Anderson model is one of the most important models in the field of strongly correlated electrons. With the recent developed numerical method density matriX embedding theory, we study the ground state properties of the periodic Anderson model on a two-dimensional square lattice. We systematically investigate the phase diagram away from half filling. We find three different phases in this region, which are distinguished by the local moment and the spin-spin correlation functions. The phase transition between the two antiferromagnetic phases is of first order. It is the so-called Lifshitz transition accompanied by a reconstruction of the Fermi surface. As the filling is close to half filling, there is no difference between the two antiferromagnetic phases. From the results of the spin-spin correlation, we find that the Kondo singlet is formed even in the antiferromagnetic phase.
文摘A stochastic model is developed to predict the peniodic operation performance ofthe continuous counter-current adsorption process. The model takes into account theeffects of random backmixing of particles, axial dispersion of liquid phase, liquid- film mass transfer, intraparticle diffusion and panticle shape, and can revealclearly the behavior of solid and liquid phase in adsorption process. The simulation results agree with the experimental data rather well.
基金supported by a Weatherstone Predoctoral Fellowship from Autism Speakssupported by NIH Grants 5R01MH098114-03,1R21-HD077197-01,and 1R21-MH104316-01
文摘Transgenic mice carrying mutations that cause Autism Spectrum Disorders（ASDs） continue to be valuable for determining the molecular underpinnings of the disorders. Recently, researchers have taken advantage of such models combined with Cre-lox P and similar systems to manipulate gene expression over space and time. Thus, a clearer picture is starting to emerge of the cell types, circuits, brain regions, and developmental time periods underlying ASDs. ASD-causing mutations have been restricted to or rescued speci？cally in excitatory or inhibitory neurons, different neurotransmitter systems, and cells speci？c to the forebrain or cerebellum. In addition,mutations have been induced or corrected in adult mice,providing some evidence for the plasticity and reversibility of core ASD symptoms. The limited availability of Cre lines that are highly speci？c to certain cell types or time periods provides a challenge to determining the cellular and circuitry bases of autism, but other technological advances may eventually overcome this obstacle.
基金supported by the National Key Basic Research Special Foundation of China(Grants Nos.2011CB921502 and 2012CB821305)the National Natural Science Foundation of China(Grants Nos.61227902,61378017,and 11434015)the State Key Laboratory for Quantum Optics and Quantum Optical Devices,China(Grant No.KF201403)
文摘Magnetic adatoms in the honeycomb lattice have received tremendous attention due to the interplay between Ruderman-Kittel-Kasuya-Yosida interaction and Kondo coupling leading to very rich physics. Here we study the competition between the antiferromagnetism and Kondo screening of local moments by the conduction electrons on the honeycomb lattice using the determinant quantum Monte Carlo method. While changing the interband hybridization V, we systemat- ically investigate the antiferromagnetic-order state and the Kondo singlet state transition, which is characterized by the behavior of the local moment, antiferromagnetic structure factor, and the short range spin-spin correlation. The evolution of the single particle spectrum are also calculated as a function of hybridization V, we find that the system presents a small gap in the antiferromagnetic-order region and a large gap in the Kondo singlet region in the Fermi level. We also find that the localized and itinerant electrons coupling leads to the midgap states in the conduction band in the Fermi level at very small V. Moreover, the formation of antiferromagnetic order and Kondo singlet are studied as on-site interaction U or temperature T increasing, we have derived the phase diagrams at on-site interaction U （or temperature T） and hybridization V plane.
基金National Natural science Foundation of China(10771048,10671209).
文摘This paper is concerned with interactional models for adults of two species delayed by their mature periods. The existence and local stability of equilibria are discussed thoroughly for competitive systems, cooperative systems and predator-prey systems, respectively. For systems with interaction of competition and cooperation, it is found that the two populations are uniformly persistent if the positive equilibrium is stable. For predator-prey interaction, however, some further conditions are needed to guarantee the persistence of the systems.
基金Support for these studies was provided by grants from the National Institutes of Health (HD-22785,HD-25189, HD-07495).
文摘The greatest risks to mammalian pregnancy occur during the peri-implantation period (passage through the uterotubal junction, blastulation, zona shedding, embryonic signaling and recognition, blastocyst attachment, postattachment events initiating placentation). Conventional markers and screening methods do not provide the means to clarify the relationship between exposure of a reproductively competent woman to a xenobiotic compound and the specific error in the functional expression of an embryogenetic process identified by impairment or deletion of that process. Laboratory models which provide the flexibility of in vitro culture methods and allow integration of cellular and molecular techniques have identified cell-specific, stage-specific markers that could focus on the mechanism of xenobiotic action. In vitro models have been used to define postattachment trophoblast cell differentiation. Trophoblast specific peptide hormones prove to be valid markers of established pregnancy. They provide no assessment of the risk to the embryo during the peri-implantation period. The relationship between developmental time of exposure and risk is discussed in terms of trophoblast differentiation.
文摘There are many cases within epidemiology where infections compete to persist within a population.In studying models for such cases,one of the goals is to determine which infections can invade a population and persist when other infections are already resident within the population.Invasion reproductive numbers(IRN),which are tied to the stability of boundary endemic equilibria,can address this question.By reinterpreting resident infections epidemiologically,this study extends methods for finding IRNs to periodic systems,and presents some examples which illustrate the often complex computations required.Results identify conditions under which a simple time-average can be used to derive IRNs,and apply the methods to examine how seasonal fluctuations in influenza incidence facilitate the year-round persistence of bacterial respiratory infections.
基金This work is supported by the National Natural Science Foundation of China(No.11701495)Scientific and Technological Key Projects of Henan Province(No.192102310193)Nanhu Scholars Program for Young Scholars of XYNU.
文摘Dynamical behaviors of a siocluustic periodic SIRS epidemic model with time delay are investigated.By constructing suitable Lyapunov functions and applying Ito's formula,the existence of the global positive solution and the property of stochastically ultimate boundedness of model(1.1)are proved.Moreover,the extinction and the persistence of the disease are established.The results are verified by numerical simulations.
基金supported by the Natural Science Foundation of Tianjin under Grant No.09JCYBJC01800
文摘This paper considers the optimal investment problem for an insurer in the sense of maximizing the adjustment coefficient of the risk process.The authors propose a modified periodic risk model in which the periodic risk process is perturbed by a standard Brownian motion.The insurer can invest in multiple risky assets and one risk-free asset and the correlations between the risky assets and the risk process are considered.Optimal strategy is obtained explicitly,which is a function of time and related to the risk process.The effects of market parameters on the optimal strategy are discussed and a numerical example is also given.
文摘In this paper we seek the solutions of the time dependent Ginzburg-Landau model for type-Ⅱ superconductors such that the associated physical observables are spatially periodic with respect to some lattice whose basic lattice cell is not necessarily rectangular. After appropriately foring the gange, the model can be formulated as a system of nonlinear parabolic partial differential equations with quasi-periodic boundary conditions. We first give some results concerning the existence, uniqueness and regularity of solutions and then we propose a semiimplicit finite element scheme solving the system of nonlinear partial dmerential equations and show the optimal error estimates both in the L2 and energy norm.We also report on some numerical results at the end of the paper.
文摘This is a very attractive article. It combines fascinating new methodology with a most interesting dataset, and a highly motivating presentation. However, despite the many
文摘The authors are to be congratulated for an innovative paper in terms of both modelling methodology and subject matter significance. The analysis of short time series is known to be
文摘Background:Asthma imposes a large healthcare burden in China and the United States(US).However,the trends of asthma mortality and the relative risk factors have not been comparatively analyzed between the countries.The aim of this study was to compare the mortality and risk factors between China and the US.Methods:The deaths,and mortality rates of asthma in China and the US during 1990–2019 were obtained from the Global Burden of Disease Study 2019.The age–period–cohort model was used to estimate these mortality rates based on a log-linear scale with additive age,period,and cohort effects.The population attributable fractions of risk factors for asthma were estimated.Results:In 1990–2019,the asthma mortality rate was higher in China than in the US.The crude and age-standardized asthma mortality rates trended downward in both China and the US from 1990 to 2019.The decline in mortality was more obvious in China.Mortality gap between the two countries was narrowing.A sex difference in asthma mortality was observed with higher mortality in males in China and females in the US.The age effects showed that mortality increased with age in adults older than 20 years,particularly in the elderly.Downward trends were generally observed in the period and cohort rate ratios in both countries,with China experiencing a more obvious decrease.Smoking and high body mass index(BMI)were the leading risk factors for asthma mortality in China and the US,respectively.Mortality attributable to occupational asthmagens and smoking decreased the most in China and the US,respectively.Conclusions:In 1990–2019,the asthma mortality rate was higher in China than in the US;however,the mortality gap has narrowed.Mortality increased with age in adults.The improvements in asthma death risk with period and birth cohort were more obvious in China than in the US.Smoking,high BMI,and aging are major health problems associated with asthma control.The role of occupational asthmagens in asthma mortality underscores the importance of management and prevention of occupational asthma.
基金supported by Jiangsu Science and Technology Department(K20221061)the Guizhou Provincial Scientifc and Technological Program(Qian Ke He(2023)General 183).
文摘Background Food-borne trematodiases(FBTs),mainly encompassing clonorchiasis,fascioliasis,fasciolopsiasis,opisthorchiasis,and paragonimiasis,is a neglected public health problem,particularly in the WHO South-East Asia and the Western Pacific regions.This study evaluates the global,regional,and national disease burden of FBTs from 1990 to 2021 and projects trends to 2030,underscore the need for targeted prevention and control.Methods Using the Global Burden of Disease 2021 database,the crude and the age-standardized prevalence rate(ASPR)and age-standardized prevalence disability-adjusted life years rate(ASDR)of FBTs at the global,regional and national level from 1990 to 2021 were described.The pivotal years of trend changes were identified using joinpoint regression analysis.The effects of age,period,cohort on FBTs prevalence and correlation with the sociode-mographic index(SDI)was analyzed.Finally,the worldwide disability-adjusted life years(DALYs)for FBTs,projected up to 2030 using the Bayesian age-period-cohort model,were analyzed.Results In 2021,44,466,329 FBTs cases[95%uncertainty interval(UI):40,017,217,50,034,921],and 998,028 DALYs[95%UI:569,766,1,638,112]were estimated across 17 countries.The Western Pacific region exhibited the highest ASPR and ASDR,with the values of 1649.26(95%UI:1461.95,1881.64)and 36.54(95%UI:19.77,64.16),respectively.From 1990 to 2021,Lao PDR,Thailand,and the Philippines showed the most substantial declines in FBTs,while Kazakhstan had the largest average annual percentage change in DALYs(-6.60,95%UI:-7.10,-6.10).High-middle and middle SDI countries exhibited higher burden,with ASDR values of 28.03(95%UI:15.41,48.73)and 16.63(95%UI:9.32,27.68),respectively.The disease burden was greater among males,peaking in the 50-59 age group.The projected ASDR in 2030 is 13.10 for males and 8.40 for females.Conclusions FBTs remain a public health threat,with the global ASDR projected to remain stable,showing only a slight decrease by 2030.Low-income countries face ambiguous mortality rates and underestimated disease burdens,highlighting the need for improved surveillance.To achieve the 2030 NTD goal,comprehensive surveillance and integrated strategies derived using a One Health approach should be prioritized to control FBTs effectively.
基金This study is supported by the "National Key Program for Developing Basic Science G1998040901-1".
文摘The analysis of the relationship between sea ice in Arctic and Antarctic, and the Southern Oscillation Index (SOI) variation on the temporal scale of month, season and year is made in this paper. The negative correlation between sea ice in Arctic and the SOI. and the positive correlation between sea ice in Antarctic and the SOI are found. The variation of sea ice in Antarctic Pacific seems to play an important role in the influence to atmosphere. Their nonlinear relationships present more strongly than the linear relationship between them. The relationship between sea ice in Arctic and Antarctic and the SOI in the early stage is investigated. Their variation shows periodic phenomena. The maximum correlation is used to build the model for forecasting the variation of the SOI on the condition of the sea ice in Arctic and Antarctic. The explained variance of the simulated series is greater than 0.90. There exists a 17-month period in the relationship between sea ice in Arctic and Antarctic and SOI. The existing of the common factor with larger scale is discussed in this paper.
文摘Singular spectrum analysis （SSA） is a technique that decomposes a time series into a set of components, such as, trend, harmonics, and residuals. Leaving out the residual components and adding up the others, the time series can be smoothed. This procedure has been used to model Brazilian electricity consumption and flow series. The PAR（p）, periodic autoregressive models, has been broadly used in modelling energy series in Brazil. This paper presents an approach of this decomposition method, by fitting the PAR（p）, considering its multivariate version known as multivariate SSA （MSSA）. The method was applied to a vector of two wind speed series recorded at two locations in the Brazilian Northeast region. The obtained results, when compared to the univariate decomposition of each series, were far superior, showing that the spatial correlation between the two series were considered by MSSA decomposition stage.
