This paper gives a precise characterization for the complexity of the problem of proving equal two streams defined with a finite number of equations: Π2. Since the Π 0 2 class includes properly both the recursively enumerable and the co-recursively enumerable classes, this result implies that neither the set of pairs of equal streams nor the set of pairs of unequal streams is recursively enumer...

There are two types of high-speed solar wind streams classified in two categories: coronal hole associated and flare generated streams. These two types of streams are classified in two categories base on magnetic field and solar wind plasma parameters. We studied the dependence of cosmic ray depressions due to high-speed solar wind streams during low amplitude days. Cosmic ray intensity data wa...

Land use has an important role influencing stream ecosystem processes, such as leaf litter breakdown. Here, we assessed rates of leaf litter breakdown in low-order tropical streams draining forest, agriculture, and urban land uses in Puerto Rico. To measure leaf breakdown rates, we placed litter bags made of coarse mesh in nine streams, three for each land use type. At each stream, we measured ...

Background: HIV/AIDS control are one of the most important goals of the health systems. The aim of this study was to determine how HIV/AIDS control was initiated among policy makers’ agenda setting in Iran.   Methods: A qualitative research (semi-structured interview) was conducted using Kingdon’s framework (problem, policy and politics streams, and policy windows and policy...