background : to assess the epidemiological characteristics of hypertensive patients in urban population of yazd, a cen­tral city in iran. methods: this cross sectional study was conducted from 2005-2006 and carried out on population aging 20-74 years. it is a part of the phase i of yazd healthy heart program that it is a community interventional study for prevention of car­diovascular disease. ...

nasonovia ribisnigri (mosely) is one of the most important pests of the lettuce plant and it was reported for the first time in ahvaz in 2008. in order to investigate the dominant species of its natural enemies and their population fluctuations, sample were taken arbitrarily from fifty plants twice a week during the growing season in 2010-2012. in this study, ten species of predators, three spe...

in this paper, sufficient conditions are investigated for the existence of periodic (not necessarily positive) solutions for nonlinear several time delay population system with feedback control. nonlinear system affected by an periodic external source is studied. existence of a control variable provides  the extension of  some previous results obtained in other studies. we give a illustrative e...

We present a SIR+ASI epidemic model to describe the interaction between human and dengue fever mosquito populations. A control strategy in the form of vaccination, to decrease the number of infected individuals, is used. An optimal control approach is applied in order to find the best way to fight the disease.

abstract in order to evaluate the effect of beauveria bassiana fungus on overwintering larvae populations of rice stem borer( chilo suppressalis) was studied during 2007-2008 in rice reaserch institute, rasht. this study was carried out based on factorial experiment with rcbd in 4 replications with three factors as follow: (a1) concentration of 1× 108 conidia/ml. , concentration of 1× 106 conid...

We use discrete time models to represent the dynamics of two interacting populations, a “valuable” population and a “pest” population. We investigate optimal control in the form of decreasing the growth rate of the “pest” population with the goal of maximizing the “valuable” population while minimizing the cost of the control. We compare different types of growth functions for the “valuable” po...