Most aviation fuels are jet fuels originating from crude oil. Crude oil must be refined to be useful and jet fuel is only one of many products that can be derived from crude oil. Jet fuel is extracted from the middle distillates fraction and competes, for example, with the production of diesel.Crude oil is a limited natural resource subject to depletion and several reports indicate that the world's crude oil production is close to the maximum level and that it will start to decrease after reaching this maximum. A post Kyoto political agenda to reduce oil consumption will have the same effect on aviation fuel production as a natural decline in the crude oil production. On the other hand, it is predicted by the aviation industry that aviation traffic will keep on increasing.The industry has put ambitious goals on increases in fuel efficiency for the aviation fleet. Traffic is predicted to grow by 5% per year to 2026, fuel demand by about 3% per year. At the same time aviation fuel production is predicted to decrease by several per cent each year after the crude oil production peak is reached resulting in a substantial shortage of jet fuel by 2026. The aviation industry will have a hard time replacing this with fuel from other sources, even if air traffic remains at current levels.

Migratory populations often stop over for short periods of time at predictable sites along their migration routes. These staging areas can be heavily used and are potentially critical to the survival of the migrants. This paper presents a method for estimating the number of individuals using such an area and their average residence time. The estimator is based on daily population estimates and records of repeat sightings of identifiable individuals. Its application is illustrated with observations on a population of migrating birds, some of which could be identified from bands that were readable from a distance.

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<p>TaqMan gene expression assays used for qPCR.</p>