the geometry of a system of second order differential equations is the geometry of a semispray, which is a globally defined vector field on tm. the metrizability of a given semispray is of special importance. in this paper, the metric associated with the semispray s is applied in order to study some types of foliations on the tangent bundle which are compatible with sode structure. indeed, suff...

aquatic invertebrates are the major group of freshwater animals in aquatic ecosystems in terms of biology and food chain. this study was conducted to identify benthic communities in four stations of the abgarmeh river (saleh abad, the ilam province) during 2007-2008. in this study eighteen families of benthose such as naididae, tubificidae, lumbricidae, erpobdellidae, gammaridae, haliplidae, co...