女性内调，从饵食开始——一个关于挽留青春美丽的话题

从秦始皇派五千童男童女寻觅长生不老药?到《西游记》中妖魔鬼怪都想吃唐僧肉?以令自身长生不老?可见“延缓衰老”是人们的一种愿望、一种追求，而当今这种愿望成了一种信念后，有很多人便身体力行地开始了探索，从某种意义上说，这种被披上浓厚神秘色彩的探素无疑成了人类研究生命科学的先驱……

Effects of Different Live Food Extracts on Fish Attraction Activities

[Objective] This study was to determine the effect of green biological feeds that little affected natural environment on fish attraction activities with the aim to explore new research direction for the recreational fishing area. [Method] The ef- fective constituents of live natural foods, including chironomid larvae, earthworm, mussels, winkles, were separated by using soaking solution extraction and centrifu- gal extraction. The extracted live foods were used to attract the carp, young cru- cian, and fishes of 100-150 days old and over 1 year old, respectively. The feed nutrition formulation of the added food attractants was designed and applied to feed- ing in the aquaculture farm. The test results were practised in bait study to conduct field fishing test and collect the data. [Results] Compared with the control group, feeding with live foods had significantly improved the growth rates of fishes at dif- ferent ages, and greatly reduced food coefficients. [Conclusion] The feeds made from live food addictives had excellent attraction ability, which not only reduced the negative effects on natural environment but also made the aquaculture mode more organic and greener.

Dynamic Behavior of a Predator-prey System with Stage-structure for Prey

In this paper, we considered the predator-prey system with stage-structure for prey, where the predators predate immature preys only. The positivity and boundedness of the solutions and asymptotic stability of equilibrium were firstly discussed, and then uniformly persistent sufficient conditions of populations were found.

Permanence and Periodic Solution of an Impulsive Delay Two-prey One-predator System with Variable Coefficients

two-prey one-predator system with a special Holling-Ⅱ functional response is discussed. That w-periodic solution of the predator extinction is global asymptotically stable is proved by some new methods. Furthermore, by the comparison theorem of impulsive differential equation, the sufficient conditions are derived for the permanence and the existence of periodic solution of the system.

Positive Periodic Solutions for Prey-predator Model with Saturation

By the theory of periodic parabolic operators, Shauder estimates and bifurcation, the existence of positive periodic solutions for periodic prey-predator model with saturation is discussed. The necessary and sufficient conditions to coexistence of periodic system are obtained.

A Leslie-Gower Holling Type-II Predator-Prey Mathematical Model with Disease in Prey Population Incorporating a Prey Refuge

We formulate and analyze a predator-prey model followed by Leslie-Gower model in which the prey population is infected by disease. We assume that the disease can only spread over prey population. As a result prey population has been classified into two categories, namely susceptible prey, infected prey where as the predator population remains free from infection. To investigate the behaviour of prey population we incorporate prey refuge in this model. Since the prey refuge decreases the predation rate then it has an important effect in our predator-prey interaction model. We have discussed the existence of various equilibrium points and local stability analysis at those equilibrium points. We investigate the Hopf-bifurcation analysis about the interior equilibrium point by taking the rate of infection parameter and the prey refuge parameter as bifurcation parameters. The numerical analysis is carried out to support the analytical results and to discuss some interesting results that our model exhibits.

青鱼的食性与钓饵

青鱼是摄食动物性饵食为主的鱼类。它的食性决定了田螺，河蚬，幼蚌，小虾，蚕蛹是它的喜好食物。在它所生存的环境中，如果水体中有这些动物性饵食的话，它的食性必然倾向于符合自己食性的食物。一般的塘主，养殖青鱼时，不可能专门针对青鱼的食性，去投放动物性饵食，在青鱼失去喜好食物的前提下，它不得不使自己的食性有所改变，去选择被动食物，如麦子，麸皮，菜籽饼，玉米面团等许多种植物类饵。食用这种饵，完全处于一种被动的状态，

王八钩钓鲶

钓鲶鱼的方法很多,用泥鳅钓、大蚯蚓钓、大青虫钓等,但多为单钩钓。而笔者根据多年经验,认为最好方法,莫过于“王八钩”钓鲶。 所谓“王八钩”,就是组钩形式如同“王八”(如图)。中间圆形身子为诱饵包,周围伸出5只钩。

PERIODIC SOLUTION AND PERSISTENCE FOR A THREE-SPECIES RATIO-DEPENDENT PREDATOR-PREY MODEL WITH TIME DELAYS IN TWO-PATCH ENVIRONMENTS

The author considers a three-species ratio-dependent predator-prey model with time delay in a two-patch environments. This model is of periodic coefficients, which incorporates the periodicity of the environment. By means of the coincidence degree theory, sufficient conditions for the existence of at least one positive periodic solution of this model are established. Moreover, The author shows that the system is uniformly persistent under the conditions.

DYNAMICS ON A HOLLING II PREDATOR-PREY MODEL WITH STATE-DEPENDENT IMPULSIVE CONTROL

to biological and chemical control strategy for pest control, a Holling II func- tional response predator-prey system concerning state-dependent impulsive control is investigated. We define the successor functions of semi-continuous dynamic system and give an existence theorem of order 1 periodic solution of such a system. By means of sequence convergence rules and quMitative analysis, we successfully get the conditions of existence and attractiveness of order 1 periodic solution. Our results show that our method used in this paper is more efficient and easier than the existing methods to prove the existence and attractiveness of order 1 periodic solution.

ANALYSIS OF A PREDATOR-PREY MODEL WITH DISEASE IN THE PREY

In this paper, we discuss the behavior of a predator-prey model with disease in the prey with and without stochastic perturbation, respectively. First, we briefly give the dynamic of the deterministic system, by analyzing stabilities of its four equilibria. Then, we consider the asymptotic behavior of the stochastic system. By Lyapunov analysis methods, we show the stochastic stability and its long time behavior around the equi- librium of the deterministic system. We obtain there are similar properties between the stochastic system and its corresponding deterministic system, when white noise is small. But large white noise can make a unstable deterministic system to be stable.

Dynamics of a non-autonomous density-dependent predator-prey model with Beddington-DeAngelis type

The goal of this paper is to investigate the dynamics of a non-autonomous density- dependent predator-prey system with Beddington-DeAngelis functional response, where not only the prey density dependence but also the predator density dependence are considered, such that the studied predator-prey system conforms to the realistically biological environment. We firstly introduce a sufficient condition for the permanence of the system and then use a specific set to obtain a weaker sufficient condition. Afterward, we provide corresponding conditions for the extinction of the system and the existence of boundary periodical solutions, respectively. ~rther, we get a sufficient condition for global attractiveness of the boundary periodic solution by constructing a Lyapunov function, arriving at the uniqueness of boundary periodic solutions since the uniqueness of boundary periodic solutions can be ensured by global attractiveness. Finally, based on the existence of positive periodic solutions, which can be ensured by the Brouwer fixed- point theorem, we provide a sufficient condition for the uniqueness of positive periodic solutions.

Optimal harvesting of a prey-predator model with variable carrying capacity

This work deals with a prey-predator model in an environment where the carrying capacities are assumed to be variable with time and one species feeds upon the other. Independent harvesting efforts are applied in either species and asymmetrical intraguild predation occurs. A common resource is consumed by two competing species and at the same time predator also consumes the prey. At first we discuss the model under constant carrying capacity and make the conclusion that no limit cycle exists in this case. Then we discuss the model without intraspecific competition. Our main concern is to cover the above mentioned two cases together, i.e. the model with variable carrying capacity and intraspecific competition. We determine the steady states and examine the dynamical behavior. We also analyze the local and global stability of the interior equilibrium by Routh-Hurwitz criterion and a suitable Lyapunov function respectively. A Hopf bifur- cation occurs with respect to a parameter which is the ratio of predator＇s and prey＇s intrinsic growth rate. The possibility of bionomic equilibrium has been considered. The optimal harvest policy is formulated and solved with Pontryagin＇s maximum principle. Some numerical simulations are given to explain most of the analytical results.

Sleeping site use of the white-headed langur Trachypithecus leucocephalus： The role of predation risk, territorial defense, and proximity to feeding sites

We collected data on sleeping site use from two groups of white-headed langurs Trachypithecus leucocephalus living in Fusui Nature Reserve, China between August 2007 and July 2008. This information was used to test several hypotheses regarding ultimate causes of sleeping site use in this primate. White-headed langurs slept either in caves （17 sites） or on a cliffledge （one site）. They used all sleeping sites repeatedly, and reused some of them on consecutive nights; three nights was the longest consecutive use of any one sleep site. We suggest that langurs use sleeping sites to make approach and attack by predators difficult, and to increase their own familiarity with a location so as to improve chances for escape. Langurs＇ cryptic behaviors with an increased level of vigilance before entering sleeping sites may also help in decreasing the possibility of detection by predators. Group 1 spent more sleeping nights in the central area of their territory than expected; in contrast, group 2 spent more sleeping nights in the periphery of their territory, which overlaps with that of another groups, than expected. The position of sleeping site relative to the last feeding site of the day and the first feeding site of the subsequent morning indicated a strategy closer to that of a multiple central place forager than of a central place forager. These results suggest that territory defense and food access may play an important role in sleeping site use of white-headed langurs [Current Zoology 57 （3）： 260-268, 2011].

Permanence of a diffusive Leslie-Gower predator-prey model incorporating a prey refuge

The diffusive Leslie-Clower predator-prey model incorporating a prey refuge is recon- sidered here. Sufficient and necessary conditions which guarantee the predator and the prey species to be permanent are obtained, and our results supplement earlier ones.

Stability and Hopf bifurcation analysis of a diffusive predator-prey model with Smith growth

In this paper, we consider a diffusive Holling-Tanner predator prey model with Smith growth subject to Neumann boundary condition. We analyze the local stability, exis- tence of a Hopf bifurcation at the co-existence of the equilibrium and stability of bifur- cating periodic solutions of the system in the absence of diffusion. Furthermore the Turing instability and Hopf bifurcation analysis of the system with diffusion are studied. Finally numerical simulations are given to demonstrate the effectiveness of the theoretical analysis.

Global stability of a stochastic predator-prey model with Allee effect

In this paper, we study a stochastic predator-prey model with Beddington-DeAngelis functional response and Allee effect, and show that there is a unique global positive solution to the system with the positive initial value. Sufficient conditions for global asymptotic stability are established. Some simulation figures are introduced to support the analytical findings.

Permanence and almost periodic solution of a predator-prey discrete system with Holling IV functional response

A predator-prey discrete-time model with non-monotone functional response and den- sity dependence is investigated in this paper. By using the comparison theorem of the difference equation, some sufficient conditions are obtained for the permanence of the system with variable coefficients. At the same time, a set of sufficient conditions about permanent of the system with almost periodic coefficients is also set up, which utilizes almost periodic characteristics of the system. Furthermore, the criteria which guarantee the existence of a globally attractive positive almost periodic solution of the system is established. An example is given to illustrate the feasibility of the obtained results.

Globally asymptotic stability of a predator-prey model with stage structure incorporating prey refuge

This paper focuses on the stabilities of the equilibria to a predator-prey model with stage structure incorporating prey refuge. By analyzing the characteristic functions, we obtain that the equilibria of the model are locally stable when some suitable conditions are being satisfied. According to the comparison theorem and iteration technique, the globally asymptotic stability of the positive equilibrium is discussed. And, the sufficient conditions of the global stability to the trivial equilibrium and the boundary equilibrium are derived. The study shows that the prey refuge will enhance the density of the prey species, and it will decrease the density of predator species. Finally, some numerical simulations are carried out to show the efficiency of our main results.

NONCONSTANT PREY HARVESTING IN RATIO-DEPENDENT PREDATOR-PREY SYSTEM INCORPORATING A CONSTANT PREY REFUGE

This paper deals with the problem of nonconstant harvesting of prey in a ratio-dependent predator-prey system incorporating a constant prey refuge. Here we use the reasonable catch-rate function instead of usual catch-per-unit-effort hypothesis. The existence, as well as the stability of possible equilibria, is carried out. Bionomic equilibrium of the system is determined and optimal harvest policy is studied with the help of Pontryagin＇s maximum principle. The key results developed in this paper are illustrated using numer- ical simulations. Our results indicate that dynamic behavior of the system very much depends on the prey refuge parameter and increasing amount of refuge could increase prey density and may lead to the extinction of predator population density.