Search results for "Lower degree"
showing 3 items of 3 documents
Fitness costs of worker specialization for ant societies
2016
Division of labour is of fundamental importance for the success of societies, yet little is known about how individual specialization affects the fitness of the group as a whole. While specialized workers may be more efficient in the tasks they perform than generalists, they may also lack the flexibility to respond to rapid shifts in task needs. Such rigidity could impose fitness costs when societies face dynamic and unpredictable events, such as an attack by socially parasitic slavemakers. Here, we experimentally assess the colony-level fitness consequences of behavioural specialization in Temnothorax longispinosus ants that are attacked by the slavemaker ant T. americanus . We manipulate…
Design and synthesis of the first triply twisted Möbius annulene.
2014
As long as 50 years ago theoretical calculations predicted that Mobius annulenes with only one π surface and one edge would exhibit peculiar electronic properties and violate the Huckel rules. Numerous synthetic attempts notwithstanding, the first singly twisted Mobius annulene was not prepared until 2003. Here we present a general, rational strategy to synthesize triply or even more highly twisted cyclic π systems. We apply this strategy to the preparation of a triply twisted [24]dehydroannulene, the structure of which was confirmed by X-ray analysis. Our strategy is based on the topological transformation of 'twist' into 'writhe'. The advantage is twofold: the product exhibits a lower deg…
Investigations on the Starch Content and Ultrastructure of Spruce Needles Relative to the Occurrence of Novel Forest Decline
1989
The starch content and ultrastructure of needles of Norway spruce trees [Picea abies (L.) Karst.] taken from three natural habitats, undamaged or with symptoms of novel forest decline, were investigated during the course of three years. The starch content was clearly dependent on the seasons, with a maximum in spring and a decline during summer and autumn, leading to a minimum in winter. Needles of damaged trees from one habitat exhibited in all three years from August to October a significantly higher starch content than their undamaged counterparts. Microscopic investigations of these needle samples exhibited severe damage symptoms to the phloem in macroscopically green needles, though mo…