PERIVITELLINE pH OF SALMONIDE EGGS IN RELATION TO AMBIENT pH1

ABSTRACT: Eggs from salmon and brown trout were reared at 6 pH levels in the pH range 4.1–7.5. By micropuncture, the pH of the perivitelline fluid (PVF) was measured at different stages of development with an antimony microelectrode system. The pH of the PVF falls with decreased pH of the ambient media, although no point of equilibrium was found at the lower pH levels. When eggs were reared at pH levels 4.1–4.7, the pH of the PVF in salmon eggs was 0.4 units above the ambient media, while that in trout eggs was 1.0 pH units above. Decreased pH of the PVF during the later, actively ion accumulation, embryonic stages will subject the embryos to ion regulating stresses similar to those registered for adult fishes.     

The effect of dynamic scheduling and routing in a solid waste management system

Solid waste collection and hauling account for the greater part of the total cost in modern solid waste management systems. In a recent initiative, 3300 Swedish recycling containers have been fitted with level sensors and wireless communication equipment, thereby giving waste collection operators access to real-time information on the status of each container. In this study, analytical modeling and discrete-event simulation have been used to evaluate different scheduling and routing policies utilizing the real-time data. In addition to the general models developed, an empirical simulation study has been performed on the downtown recycling station system in Malmoe, Sweden. From the study, it can be concluded that dynamic scheduling and routing policies exist that have lower operating costs, shorter collection and hauling distances, and reduced labor hours compared to the static policy with fixed routes and pre-determined pick-up frequencies employed by many waste collection operators today. The results of the analytical model and the simulation models are coherent, and consistent with experiences of the waste collection operators.