The possibilities for collecting, storing, and processing of data have increased significantly over the last decades. It has been argued that an increasing demand for health data will de...

We describe and analyse how large herbivores strongly diminished a woody vegetation, dominated by the unpalatable shrub Sambucus nigra L. and changed it into grassland. Density of woody species and cover of vegetation were measured in 1996, 2002 and 2012 in the grazed Oostvaardersplassen. In 2002 and 2012 we also measured density and cover in an ungrazed control site. In 2002 we measured intensity of browsing and bark loss of Sambucus shrubs in the grazed and control sites. In the grazed (...) site the density of Sambucus and Salix spp. declined significantly between 1996 and 2012, and large areas changed into grassland. In the control site the density of Sambucus increased significantly during this period, the density of Salix spp. did not change, and the vegetation consisted of a mixture of woody species and a field layer dominated by tall herbs. In 2002 and 2012 the percentages of dead Sambucus shrubs were significantly higher in the grazed site than in the control site. In 2002 the percentages of twigs browsed and ring barked stems of Sambucus shrubs were significantly higher in the grazed site than in the control site. Our results show that debarking caused mature Sambucus shrubs to die, but that heavy browsing may have helped this process. Our results also point to a significant neighbour effect on the break down of Sambucus, suggesting that Aggregational Resistance and Associational Palatability were both active. Essential conditions for the break down of this woody vegetation were the presence of large herbivores, the low ratio between the areas of summer and winter feeding habitats and the competition amongst herbivores. Browsing may have been responsible for seedling death, as seedlings were found only in the control site and not on the old and newly established grasslands in the grazed site. (shrink)

Ni-44 at.% Al and Ni-50 at.% Al single crystals were tested in compression in the hard d 001 ¢ orientation. The dislocation processes and deformation behaviour were studied as a function of temperature, strain and strain rate. A slip transition in NiAl occurs from a d 111 ¢ slip to non- a d 111 ¢ slip at intermediate temperatures. In Ni-50 at.% Al single crystals, only a d 010 ¢ dislocations are observed above the slip transition temperature. In contrast, a (...) d 101 ¢ {101} glide has been observed to control deformation beyond the slip transition temperature in Ni-44 at.% Al. a d 101 ¢ dislocations are observed primarily along both d 111 ¢ directions in the glide plane. High-resolution transmission electron microscopy observations show that the core of the a d 101 ¢ dislocations along these directions is decomposed into two a d 010 ¢ dislocations, separated by a distance of approximately 2 nm. The temperature window of stability for these a d 101 ¢ dislocations depends upon the strain rate. At a strain rate of 1.4 2 10 m 4 s m 1 , a d 101 ¢ dislocations are observed between 800 and 1000 K. Complete decomposition of a d 101 ¢ dislocations into a d 010 ¢ dislocations occurs beyond 1000 K, leading to a d 010 ¢ climb as the deformation mode at higher temperatures. At lower strain rates, decomposition of a d 101 ¢ dislocations has been observed to occur along the edge orientation at temperatures below 1000 K. Embedded-atom method calculations and experimental results indicate that a d 101 ¢ dislocations have a large Peierls stress at low temperatures. Based on the present microstructural observations and a survey of the literature with respect to vacancy content and diffusion in NiAl, a model is proposed for a d 101 ¢ {101} glide in Ni-44 at.% Al, and for the observed yield strength versus temperature behaviour of Ni-Al alloys at intermediate and high temperatures. (shrink)