We study a class of first order quasilinear equations on bounded domains in the L ∞ framework. Using the "semi Kružkov entropy-flux pairs", we define a weak-entropy solution, state an existence and uniqueness result, and a maximum principle.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Fluctuating prey populations and their effects on avian predator population dynamics have been studied particularly at high latitudes, where prey populations, especially microtines, are known to be cyclic; raptors show both numerical and functional responses to variations in their prey. In this paper, we investigate the response of a migratory raptor (Montagu's Harrier, Circus pygargus) to variations in abundance of its main prey (common vole, Microtus arvalis) in France. We document multiannual fluctuation in the abundance of common voles. The numerical response of Montagu's Harrier to this variable food supply was studied using breeding parameters (breeding density, breeding phenology, and various measures of breeding success). Breeding density and mean clutch size were strongly correlated with spring vole abundance, whereas mean brood size at fledging was correlated positively with summer vole abundance. The mechanism involved in the numerical response of Montagu's Harrier indicates that dispersal and colonization by yearlings may be more important than natality per se. Pellets collected between 1986 and 1997 were used to determine the functional response of Montagu's Harrier to variations in vole abundance. In terms of biomass, Montagu's Harrier diet consisted mainly of voles (33.7-86.6%, between 1986 and 1997). Vole biomass in pellets was closely related to vole abundance estimated by trapping. A type II functional response was detected, with satiation at high prey density, as the shapes of many relationships between breeding parameters and vole abundance were more curvilinear than linear. Our results fit the pattern of relationships between predators and cyclic prey found in Fennoscandia, in which specialist predators show a strong numerical response, although at such a temperate latitude, a more pronounced functional response might have been expected.

This study is the first to demonstrate training-related benefits to gross motor performance stemming from cognitive dual-task training. The results support the view that motor control in aging is influenced by executive control and have implications for theories of cognitive training and transfer.