OPTIMAL CONTROL PROBLEM FOR A PERIODIC PREDATOR-PREY MODEL WITH AGE-DEPENDENCE

In this paper,we investigate optimal policy for periodic predator-prey system with age-dependence.Namely,we consider the model with periodic vital rates and initial distribution.The existence of optimal control strategy is discussed by Mazur’s theorem and optimality condition is derived by means of normal cone.

Optimal harvesting for an age-dependent n-dimensional food chain model

This paper is concerned with optimal harvesting policy for an age-dependent n-dimensional food chain model. The existence and uniqueness of non-negative solution of the system are proved using the fixed point theorem. By Mazur＇s theorem, the existence of optimal control strategy is demonstrated and optimality conditions derived by means of normal cone.

A promising approach for quantifying focal stroke modeling and assessing stroke progression:optical resolution photoacoustic microscopy photothrombosis

To investigate the mechanisms underlying the onset and progression of ischemic stroke,some methods have been proposed that can simultaneously monitor and create embolisms in the animal cerebral cortex.However,these methods often require complex systems and the effect of age on cerebral embolism has not been adequately studied,although ischemic stroke is strongly age-related.In this study,we propose an optical-resolution photoacoustic microscopy-based visualized photothrombosis methodology to create and monitor ischemic stroke in mice simultaneously using a 532 nm pulsed laser.We observed the molding process in mice of different ages and presented age-dependent vascular embolism differentiation.Moreover,we integrated optical coherence tomography angiography to investigate age-associated trends in cerebrovascular variability following a stroke.Our imaging data and quantitative analyses underscore the differential cerebrovascular responses to stroke in mice of different ages,thereby highlighting the technique's potential for evaluating cerebrovascular health and unraveling age-related mechanisms involved in ischemic strokes.

A General Model for Hepatitis B Disease with Age-Dependent Susceptibility and Transmission Probabilities

A SEI model for hepatitis B is constructed where the susceptibility and other crucial transmission probabilities depend on the chronological age and the basic reproduction rate R0 is derived. Under suitable (biological and mathematical) assumptions in a closed population, results of Houpa D. D. E. et al. [1] are extended from constant case of p and q to age-dependent case: the disease-free equilibrium is globally asymptotically stable (GAS) if R0 . On the other hand, R0 > 1 induces that endemic equilibrium is GAS and the system is uniformly persistent.

Existence results and behavior analysis for nonlinear age-dependent population dynamics problems with conformable fractional operator

In this paper,we investigate the existence of solutions and analyze the large-time behavior for Gurtin-Maccamy population model involving conformable fractional derivatives.As a preliminary step,we construct a generic structure of the solution associated with our proposed model by utilizing some basic properties and tools of conformable fractional calculus.We establish the existence of a unique solution of the given model with the given initial conditions.At last,by using the upper and lower solutions for the characteristic equation,we define the upper and lower boundaries for the obtained solution and describe the large-time behavior of the total population.

Limb Muscle Hemodynamics and Arterial Distensibility Depend on Atmospheric Pressure in Hypertensive Men

Objective To verify whether peripheral blood circulation and arterial wall distensibility are influenced by atmospheric pressure （AtPr） and to examine if their association is dependent on age and/or sex. Methods Associations among natural AtPr levels （on the examination day as well as 1 and 2 days prior）, limb muscle hemodynamics, and distensibility of conduit arteries were retrospectively examined in an observational study of 276 untreated patients with primary moderate hypertension （mean age 56.4 years, 194 men）. Forearm and calf circulations at rest and 3 min after ischemia were measured by venous occlusion plethysmography. Compliance of the brachial and shank arteries was assessed by oscillometry. Results After adjustment for age, degree of hypertension, and season, correlation and multiple resression analyses revealed a season-independent but age-dependent direct correlation between the stiffness of limb arteries and AtPr levels on the examination day in men, but not women. The association weakened with the degree of hypertension, disappeared with age, and was more evident in the arms than in the legs. Conclusion Parameters of arterial wall distensibility in adult hypertensive men are susceptible to AtPr changes within the usually observed limits （730-770 mmHg）. It is proposed that reduction of arterial wall barometric responsiveness in women and aging men is a likely mechanism underlying their meteosensitivity.

Natural history and long-term clinical course of Crohn's disease

Crohn’s disease is a chronic inflammatory disease process involving different sites in the gastrointestinal tract. Occasionally, so-called metastatic disease occurs in extra-intestinal sites. Granulomatous inflammation may be detected in endoscopic biopsies or resected tissues. Genetic, epigenetic and environmental factors appear to play a role. Multiple susceptibility genes have been described in both familial and non-familial forms while the disease is phenotypically heterogeneous with a female predominance. The disorder occurs over a broad age spectrum, from early childhood to late adulthood. More than 80% are diagnosed before age 40 years usually with terminal ileal and colonic involvement. Pediatric-onset disease is more severe and more extensive, usually with a higher chance of upper gastrointestinal tract disease, compared to adult-onset disease. Long-term studies have shown that the disorder may evolve with time into more complex disease with stricture formation and penetrating disease complications (i.e., fistula, abscess). Although prolonged remission may occur, discrete periods of symptomatic disease may re-appear over many decades suggesting recurrence or re-activation of this inflammatory process. Eventual development of a cure will likely depend on identification of an etiologic cause and a fundamental understanding of its pathogenesis. Until now, treatment has focused on removing risk factors, particularly cigarette smoking, and improving symptoms. In clinical trials, clinical remission is largely defined as improved numerical and endoscopic indices for “mucosal healing”. “Deep remission” is a conceptual, more “extended” goal that may or may not alter the long-term natural history of the disease in selected patients, albeit at a significant risk for treatment complications, including serious and unusual opportunistic infections.

Long-term natural history of Crohn’s disease

Crohn’s disease is a chronic inflammatory granulomatous process that usually involves different sites in the intestinal tract. Genetic and environmental factors are thought to play a role in its etiology and pathogenesis. The disorder has a heterogeneous clinical expression and data from tertiary care settings have documented its female predominance, occasional familial nature, and high rate of stricture formation and penetrating disease. It may appear from early childhood to late adulthood, although over 80% are currently diagnosed before age 40 years, usually with terminal ileal and colonic involvement. Several studies have now shown differences in phenotypic clinical expression depending on the initial age at diagnosis, with pediatric-onset disease being more severe and more extensive with more involvement of the upper gastrointestinal tract compared to adult-onset disease. In addition, long- term studies from these tertiary care settings have documented that the disorder may evolve with time into a more complex disease with stricture formation and penetrating disease complications (i.e. fistula and abscess). Although prolonged remission with no evidence of inflammatory disease may occur, discrete periods of symptomatic and active granulomatous inflammatory disease may re-appear over many decades. Long-term studies on the natural history have also suggested that discrete events (or agents) may precipitate this granulomatous inflammatory process.

Effect of auditory stress agents on heterozygous German waltzing guinea pigs

The German waltzing guinea pig is a strain of animals expressing deafness and severe balance disorders at birth.The mutation arose spontaneously in a breeding facility in Germany and as the affected animals show a characteristic waltzing behavior,the strain is named the German waltzing guinea pig.The strain is presently bred only at Karolinska Institutet.The hereditary inner ear impairment has a recessive mode of inheritance and the strain thus produces not only affected homozygotes but also symptom-free heterozygotes and fully normal offspring.The outcome depends solely on the genotype of the parents.The heterozygotes,which have obtained the 'waltzing' gene from one parent only,have normal hearing and no balance dysfunction.The heterozygous animals appear normal but will,in turn,carry the genetic defect to the next generation.The present thesis is focused on these animals.Noise and ototoxic drugs are well known stress factors that interfere negatively with the hearing organ in both humans and animals,causing hearing impairment.However,the inter-individual variability in susceptibility to auditory stress factors is surprisingly large,most likely due to different genetic predisposition.In this study,heterozygous animals of the German waltzing guinea pig,animals carrying a genetic defect known to cause severe hearing impairment,were used to study how an unexplored gene for deafness interacts with auditory stress agents,i.e.noise exposure and the ototoxic drugs gentamicin and cisplatin.Animals were exposed to both narrowband as well as broadband noise at different ages and hearing thresholds were measured using ABRs.Heterozygotes of the German waltzing guinea pig showed less threshold shifts compared to control strains.Older animals were less affected by the noise trauma than younger animals.To test the hypothesis that the efferent system contributes to protection of the inner ear against noise trauma,measurements using a new method of post onset adaptation of DPOAEs and maximum adaptation magnitude were conducted.The post onset adaptation of DPOAEs detected a strain difference at the higher frequency region while in the maximum adaptation magnitude method showed no difference between the strains.The heterozygous German waltzing guinea pigs displayed a distinctly increased resistance to noise exposures,manifested as reduced threshold shifts and faster recovery following acoustic overstimulation.However,when exposed to ototoxic drugs,the heterozygous carriers suffered from a more pronounced hearing loss.It is concluded that endogenous resistance to noise in the heterozygotes does not offer any protection against ototoxic drugs.The detailed mechanisms remain to be explored.

OPTIMAL BIRTH CONTROL FOR AN AGE-DEPENDENT COMPETITION SYSTEM OF N SPECIES

In this paper, we investigate optimal policies for an age-dependent n-dimensional competition system, which is controlled by fertility. By using Dubovitskii-Milyutin＇s general theory, the maximum principles are obtained for the problems with free terminal states, infinite horizon, and target sets, respectively.

Age-dependent expression of forkhead box O proteins in the duodenum of rats

The O subfamily of forkhead box(FoxO) proteins is the downstream effector of the insulin-like growth factor-1/phosphoinositide 3-kinase/protein kinase B(IGF-1/PI3K/PKB) signal pathway.The objective of the present study was to examine the expressions of three members of FoxO proteins,FoxO1,FoxO3a,and FoxO4 in the duodenum of Sprague-Dawley rats at different ages.The result demonstrated that the expression of FoxO4 in rat duodenum showed an age-dependent manner.At Day 21,there were no detectable localization and expression of FoxO4 in the duodenum,while,at Months 2 and 6,localization and expression of FoxO4 were distinct.In addition,FoxO4 staining was primarily concentrated in the cell nuclei of the lamina propria around the intestinal gland of the duodenum in 2-month-old rats,but was not detectable in the same area in 6-month-old rats.Our results showed also that although FoxO3a existed in the cytoplasm of the lamina propria at a low level at the 2-and 6-month marks,it was still not detectable at Day 21.Besides,FoxO1 was not detectable in all parts and stages.Taken together,our findings suggested that the cell-specific and age-dependent expressional patterns of FoxO4 and FoxO3a proteins in the duodenum play some roles in the development and growth performance of the rat duodenum.

OVERTAKING OPTIMAL HARVESTING FOR AN AGE-DEPENDENT n-DIMENSIONAL FOOD CHAIN MODEL

This paper is concerned with an optimal harvesting problem over an infinite horizon for age-dependent n-dimensional food chain model and the analysis of long-term behaviors of the optimal-controlled system. The existence of overtaking optimal policy is proved and a maximum principle is carefully derived by means of Dubovitskii-Milyutin functional analytical extremum theory. Weak and strong turnpike properties of optimal trajectories are established.

Age-dependent branching processes in random environments

We consider an age-dependent branching process in random environments. The environments are represented by a stationary and ergodic sequence ξ = (ξ 0, ξ 1,…) of random variables. Given an environment ξ, the process is a non-homogenous Galton-Watson process, whose particles in n-th generation have a life length distribution G(ξ n ) on ?+, and reproduce independently new particles according to a probability law p(ξ n ) on ?. Let Z(t) be the number of particles alive at time t. We first find a characterization of the conditional probability generating function of Z(t) (given the environment ξ) via a functional equation, and obtain a criterion for almost certain extinction of the process by comparing it with an embedded Galton-Watson process. We then get expressions of the conditional mean E ξ Z(t) and the global mean EZ(t), and show their exponential growth rates by studying a renewal equation in random environments.

Mean-square Stability of Stochastic Age-dependent Delay Population Systems with Jumps

In this paper, we present the compensated stochastic θ method for stochastic age-dependent delay population systems（SADDPSs） with Poisson jumps. The definition of mean-square stability of the numerical solution is given and a sufficient condition for mean-square stability of the numerical solution is derived. It is shown that the compensated stochastic θ method inherits stability property of the numerical solutions. Finally,the theoretical results are also confirmed by a numerical experiment.

OPTIMAL CONTROL FOR A NONLINEAR n-DIMENSIONAL COMPETING SYSTEM WITH AGE-STRUCTURE

This paper is concerned with optimal harvesting control of a first order partial differential equation system representing a nonlinear n-dimensional competitive population model with age-structure. By the Ekeland＇s variational principle, the existence and unique char- acterization of the optimal control strategy are established. The optimality conditions for the control problem are obtained by the concept of the normal cone.

MODELLING AND STABILITY ANALYSIS OF POPULATION GROWTH WITH SPATIAL DIFFUSION

In recent years, population growth models with spatial diffusion have beenextensively studied by many authors (for example, see [1-5]). In this paper, a populationgrowth model is considered with a discrete age-dependence and spatial diffusion, and isinvestigated in a semigroup framework. The spectral properties of the population oper-ator are given. On the basis of such spectral consideration, the asymptotic behaviourof the semigroup generated by the population operator is obtained. Finally, a nonlinearpopulation growth model is considered and its stability is analyzed.

Characterization of Changes and Driver Microbes in Gut Microbiota During Healthy Aging Using A Captive Monkey Model

Recent population studies have significantly advanced our understanding of how age shapes the gut microbiota.However,the actual role of age could be inevitably confounded due to the complex and variable environmental factors in human populations.A well-controlled environment is thus necessary to reduce undesirable confounding effects,and recapitulate age-dependent changes in the gut microbiota of healthy primates.Herein we performed 16S rRNA gene sequencing,characterized the age-associated gut microbial profiles from infant to elderly crab-eating macaques reared in captivity,and systemically revealed the lifelong dynamic changes of the primate gut microbiota.While the most significant age-associated taxa were mainly found as commensals such as Faecalibacterium,the abundance of a group of suspicious pathogens such as Helicobacter was exclusively increased in infants,underlining their potential role in host development.Importantly,topology analysis indicated that the network connectivity of gut microbiota was even more agedependent than taxonomic diversity,and its tremendous decline with age could probably be linked to healthy aging.Moreover,we identified key driver microbes responsible for such age-dependent network changes,which were further linked to altered metabolic functions of lipids,carbohydrates,and amino acids,as well as phenotypes in the microbial community.The current study thus demonstrates the lifelong age-dependent changes and their driver microbes in the primate gut microbiota,and provides new insights into their roles in the development and healthy aging of their hosts.

Automated rapid iterative negative geotaxis assay and its use in a genetic screen for modifi ers of Aβ_(42)-induced locomotor decline in Drosophila

The negative-geotaxis climbing assay is used to efficiently study aging and neurodegeneration in Drosophila.To make it suitable for large-scale study,a method called the rapid iterative negative geotaxis（RING） assay has been established by simultaneously photographing the climbing of multiple groups of flies when they are manually tapped down in test tubes.Here,we automated the assay by using a well-controlled electric motor to drive the tapping,and a homemade program to analyze the climbing height of flies.Using the automated RING（aRING） assay,we found that the climbing ability of a strain of wild-type flies,males in particular,declined rapidly before day 21 after eclosion,but slowly from day 21 to 35.We also found that the expression of arctic mutant Aβ_（42） accelerated the age-dependent decline in the climbing ability of flies.Moreover,using aRING,we examined the effect of third chromosome deficiencies on the accelerated locomotor decline in Aβ_（42）-expressing flies,and isolated 7 suppressors and15 enhancers.

Global stability for an SEI model of infectious diseases with immigration and age structure in susceptibility

In this paper, we propose an SEI age-structured model for infectious diseases where the susceptibility depends on the age and with immigration of new individuals into the susceptible, exposed and infectious classes. The existence of a global attractor and the asymptotic smoothness of the solution semi-flow generated by the model are addressed. Using a Lyapunov functional, we show that the unique endemic equilibrium is globally asymptotically stable.

Sexual behavior and male volatile compounds in wild and mass-reared strains of the Mexican fruit fly Anastrepha ludens （Diptera： Tephritidae） held under different colony management regimes

We compared the calling and mating behavior and volatile release of wild males Anastrepha ludens （Loew） with males from 4 mass-reared strains： （i） a stan- dard mass-reared colony （control）, （ii） a genetic sexing strain （Tap-7）, （iii） a colony started from males selected on their survival and mating competitiveness abilities （selected）, and （iv） a hybrid colony started by crossing wild males with control females. Selected and wild males were more competitive, achieving more matings under field cage conditions. Mass-reared strains showed higher percentages of pheromone calling males under field conditions except for Tap-7 males, which showed the highest percentages of pheromone calling males under laboratory cage conditions. For mature males of all strains, field-cage calling behavior increased during the last hour before sunset, with almost a 2 fold increase exhibited by wild males during the last half hour. The highest peak mating activity of the 4 mass-reared strains occurred 30 rain earlier than for wild males. By means of solid phase microextraction （SPME） plus gas chromatography-mass spectrometry （GC- MS）, the composition of volatiles released by males was analyzed and quantified, Wild males emitted significantly less amounts of （E,E）-α-farnesene but emitted significantly more amounts of （E,E）-suspensolide as they aged than mass-reared males. Within the 4 mass-reared strains, Tap-7 released significantly more amounts of （E,E）-α-farnesene and hybrid more of （E,E）-suspensolide. Differences in chemical composition could be ex- plained by the intrinsic characteristics of the strains and the colony management regimes. Characterization of calling behavior and age changes of volatile composition between wild and mass-reared strains could explain the differences in mating competitiveness and may be useful for optimizing the sterile insect technique in A. ludens.