the purpose of this study is the analysis of the farmers economic behavior to reduce the adverse environmental effects of agricultural chemical inputs by using contingent valuation approach and tobit model by heckman's two stage. to achieve the desired goal, 100 questionnaires collected by a random sampling from farmers of kashaf- rood basin in mashhad city in 2013. results showed that variable...

In dynamical systems examples are common in which two or more attractors coexist, and in such cases the basin boundary is nonempty and the basins often have fractal basin boundaries. The purpose of this paper is to describe the structure and properties of unbounded basins and their boundaries for two-dimensional diffeomorphisms. Frequently, if not always, there is a periodic saddle on the bound...

[1] Among countries with river basin organizations to manage their water resources, Spain’s experience is one of the longest. One of the first basin agencies established in Spain was for the Guadalquivir River in the south. A case study of that river basin and its management indicates how basin management is shaped by political economy factors such as the historical path of the agency’s evoluti...

New data on the distribution of fossil fish together with floral and tetrapod evidence are used to develop an internal correlation of the strata of the early Mesozoic Newark Supergroup of eastern North America. Within the Newark, we recognize five informal biostratigraphic zones, each characterized by a particular fish fauna. These fish zones are then related to other Mesozoic freshwater deposi...

BACKGROUND Aquatic insects are the major groups of arthropods that spend some parts of their life cycle in the water. These insects play an important role for transmission of some human and animal diseases. There is few information about the aquatic insects fauna of Iran. METHODS To study the aquatic insects fauna, adult, nymphal and larval collections were carried out from different habitats...

Large closed basins are often associated with regions of active tectonics. In contrast, we provide the example of the Great Divide Basin, in southern Wyoming, where climate change, through its impact on erosion and fl exure, provides the primary mechanism of basin closure. Twoand three-dimensional fl exural models that incorporate the effects of local basin abandonment due to aridity as well as...

Background: Zayandeh-rud river is the most important in central regions of Iran and present study aimed to provide new insights into microplastics (MPs) pollution surface water sediments this river. Methods: Water sediment samples were collected July 2021 from 19 sampling sites along Organics matters removed by wet peroxide oxidation (WPO), MPs extracted floatation ZnCl2 -saturated salt filtrat...