Dynamics of a Heroin Epidemic Model with Very Population

Based on the model provided by the Mulone and Straughan [1], we relax the population which are constant and obtain the drug-free equilibrium which is global asymptotically stable under some conditions. The system has only uniqueness positive endemic equilibrium which is globally asymptotically stable by using the second compound matrix.

DYNAMICS OF A NONLOCAL DISPERSAL FOOT-AND-MOUTH DISEASE MODEL IN A SPATIALLY HETEROGENEOUS ENVIRONMENT

Foot-and-mouth disease is one of the major contagious zoonotic diseases in the world.It is caused by various species of the genus Aphthovirus of the family Picornavirus,and it always brings a large number of infections and heavy financial losses.The disease has become a major public health concern.In this paper,we propose a nonlocal foot-and-mouth disease model in a spatially heterogeneous environment,which couples virus-to-animals and animals-to-animals transmission pathways,and investigate the dynamics of the disperal.The basic reproduction number R_(0)is defined as the spectral radius of the next generation operator R(x)by a renewal equation.The relationship between R_(0)and a principal eigenvalue of an operator L_(0)is built.Moreover,the proposed system exhibits threshold dynamics in terms of R_(0),in the sense that R_(0)determines whether or not foot-and-mouth disease invades the hosts.Through numerical simulations,we have found that increasing animals'movements is an effective control measure for preventing prevalence of the disease.

Effect of helium concentration on irradiation damage of Fe-ion irradiated SIMP steel at 300℃and 450℃

SIMP steel is newly developed fully martensitic steel for lead-cooled fast reactors and accelerator-driven systems.It is important to evaluate its radiation resistance via high flux neutron irradiation,where dense He atoms can be formed via(n,α)transmutation reaction.Co-irradiation with Fe and He ions,instead of neutron,was performed.Specimens were irradiated with 6.4-MeV Fe ions to the damage dose of 5 dpa at a depth of 600 nm.Three different helium injection ratios of 60-appm He/dpa(dpa:displacements per atom),200-appm He/dpa and 600-appm He/dpa at a depth of 600 nm,were performed.Two different irradiation temperatures of 300℃and 450℃were carried out.The effect of helium concentration on the microstructure of Fe-irradiated SIMP steel was investigated.Microstructural damage was observed using transmission electron microscopy.The formed dislocation loops and bubbles depended on the helium injection ratio and irradiation temperature.Lots of dislocation loops and helium bubbles were homogeneously distributed at 300℃,but not at 450℃.The causes of observed effects are discussed.

Parameter identifiability of a within-host SARS-CoV-2 epidemic model

Parameter identification involves the estimation of undisclosed parameters within a system based on observed data and mathematical models.In this investigation,we employ DAISY to meticulously examine the structural identifiability of parameters of a within-host SARS-CoV-2 epidemic model,taking into account an array of observable datasets.Furthermore,Monte Carlo simulations are performed to offer a comprehensive practical analysis of model parameters.Lastly,sensitivity analysis is employed to ascertain that decreasing the replication rate of the SARS-CoV-2 virus and curbing the infectious period are the most efficacious measures in alleviating the dissemination of COVID-19 amongst hosts.

Nonpharmaceutical interventions contribute to the control of COVID-19 in China based on a pairwise model

Nonpharmaceutical interventions(NPIs),particularly contact tracing isolation and household quarantine,play a vital role in effectively bringing the Coronavirus Disease 2019(COVID-19)under control in China.The pairwise model,has an inherent advantage in characterizing those two NPIs than the classical well-mixed models.Therefore,in this paper,we devised a pairwise epidemic model with NPIs to analyze COVID-19 outbreak in China by using confirmed cases during February 3rde22nd,2020.By explicitly incorporating contact tracing isolation and family clusters caused by household quarantine,our model provided a good fit to the trajectory of COVID-19 infections.We calculated the reproduction number R=1.345(95%CI:1.230-1.460)for Hubei province and R=1.217(95%CI:1.207-1.227)for China(except Hubei).We also estimated the peak time of infections,the epidemic duration and the final size,which are basically consistent with real observation.We indicated by simulation that the traced high-risk contacts from incubated to susceptible decrease under NPIs,regardless of infected cases.The sensitivity analysis showed that reducing the exposure of the susceptible and increasing the clustering coefficient bolster COVID-19 control.With the enforcement of household quarantine,the reproduction number R and the epidemic prevalence declined effectively.Furthermore,we obtained the resumption time of work and production in China(except Hubei)on 10th March and in Hubei at the end of April 2020,respectively,which is broadly in line with the actual time.Our results may provide some potential lessons from China on the control of COVID-19 for other parts of the world.

An edge-based model for non-Markovian sexually transmitted infections in coupled network

In this paper,allowing for general transmission and recovery times distributions,we proposed an edge-based age-structured-like compartmental model for STIs(EBACMS)in a coupled nctwork.We considered sexual transmissions between men with also heterosexual contacts.Mathematically,we gave the general approach of proving the nonnegativity of solutions for the system coupling ordinary and partial differen-tial equations,which can be applied to all edge-based compartment models.We then analyzed the epidemic threshold Ro with different distributions which couples the thresholds of the single-layer and bipartite networks in the percolation theory.We also studied the global stability of disease-free equilibrium with R0<1 and the final epidemic size F(the proportion of the population experiencing infection during the epidemic)with R0>1.In addition,numerical simulations indicated that given a fixed exponential transmission distribution,a higher variance(with same mean)in general recovery distribution gives smaller R0 and F.Sensitivity analysis on Ro and F in terms of the parameters illustrated that male-to-male transmission routes have a greater impact on Rg and F than the heterosexual transmission routes for the Markovian transmission process and arbitrary recovery process.The results provide a good theoretical guideline to consider the distributions of real-world STIs.

Global dynamics of a heroin epidemic model with age structure and nonlinear incidence

A heroin model with nonlinear incidence rate and age structure is investigated. The basic reproduction number is determined whether or not a heroin epidemic breaks out. By employing the Lyapunov functionals, the drug-free equilibrium is globally asymptotically stable if R0 ≤1; while the drug spread equilibrium is also globally asymptotically stable if R0≤ 1. Our results imply that improving detected rates and drawing up the efficient prevention play more important role than increasing the treatment for drug users.

Optimal control and cost-effective analysis of an agestructured emerging infectious disease model

Emerging infectious diseases are one of the global public health problems which may lead to widespread epidemics and potentially life-threatening infection.Integrated vaccination and physical distancing interventions are two elementary methods for preventing infectious diseases transmission.In this paper,we construct a continuous age-structured model for investigating the transmission dynamics of an emerging infection disease during a short period.We derive the basic regeneration number R 0,the spectral radius of the next generation operator K,which determines the disease outbreak or not.Furthermore,we propose an optimal control problem to take account for the cost-effectiveness of social distancing intervention and vaccination.We rigorously obtain sufficient conditions for a L1 control problem.Numerical simulations show that coupling integrated vaccination and physical distancing intervention could effectively eliminate the infection,and such control strategy is more sensitive for people aged 10e39 and over 60.

Rational Design of Bioactive Materials for Bone Hemostasis and Defect Repair

Everyday unnatural events such as trauma,accidents,military conflict,disasters,and even medical malpractice create open wounds and massive blood loss,which can be life-threatening.Fractures and large bone defects are among the most common types of injuries.Traditional treatment methods usually involve rapid hemostasis and wound closure,which are convenient and fast but may result in various complications such as nerve injury,deep infection,vascular injury,and deep hematomas.To address these complications,various studies have been conducted on new materials that can be degraded in the body and reduce inflammation and abscesses in the surgical area.This review presents the latest research progress in biomaterials for bone hemostasis and repair.The mechanisms of bone hemostasis and bone healing are first introduced and then principles for rational design of biomaterials are summarized.After providing representative examples of hemostatic biomaterials for bone repair,future challenges and opportunities in the field are proposed.

A note on an age-of-infection SVIR model with nonlinear incidence

In this paper, nonlinear incidence rate is incorporated into an age-of-infection SVIR epidemiological model. By the method of Lyapunov functionals, it is shown that the basic reproduction number R0 of the model is a threshold parameter in the sense that if R0 〈 1, the disease dies out, while if R0〉1, the disease persists.