Compact tokamak reactors part 2 (numerical results)

The authors describe a numerical optimization scheme for fusion reactors. The particular application described is to find the smallest copper coil spherical tokamak, although the numerical scheme is sufficiently general to allow many other problems to be solved. The solution to the steady state energy balance is found by first selecting the fixed variables. The range of all remaining variables is then selected, except for the temperature. Within the specified ranges, the temperature which satisfies the power balance is then found. Tests are applied to determine that remaining constraints are satisfied, and the acceptable results then stored. Results are presented for a range of auxiliary current drive efficiencies and different scaling relationships; for the range of variables chosen the machine encompassing volume increases or remains approximately unchanged as the aspect ratio is reduced

Ticks in the South African Zoological Survey Collection. Part VIII. Two East African ticks

(1) The description of the male and the female is given; the immature stages are described for the first time, the description is based on material raised by Miss Walker at Kabete. (2) The known hosts and its geographical distribution are given.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Carotenoid-based skin ornaments reflect foraging propensity in a seabird, Sula leucogaster

Carotenoid-based ornaments are common signalling features in animals. It has long been proposed that such ornaments communicate information about foraging abilities to potential mates. However, evidence linking foraging with ornamentation is largely missing from unmanipulated, free-ranging populations. To investigate this relationship, we studied a coastal population of brown booby (Sula leucogaster brewsteri), a seabird with a carotenoid-based gular skin ornament. δ13C values from both feathers and blood plasma were negatively correlated with male gular colour, indicating birds that consumed more pelagic prey in offshore locations had more ornamented skin than those that fed on nearshore, benthic prey. This relationship was supported by our GPS tracking results, which revealed longer, more offshore foraging trips among highly ornamented males. Our data show that brown booby ornaments are honest indicators of foraging propensity; a link consistent with the rarity hypothesis and potentially driven by the concentration of carotenoids found in phytoplankton versus benthic algae. Carotenoid-based ornaments may reflect foraging tendencies in animals such as coastal predators that use food webs with distinct carotenoid profiles

Millennial-scale isotope records from a wide-ranging predator show evidence of recent human impact to oceanic food webs

Human exploitation of marine ecosystems is more recent in oceanic than near shore regions, yet our understanding of human impacts on oceanic food webs is comparatively poor. Few records of species that live beyond the continental shelves date back more than 60 y, and the sheer size of oceanic regions makes their food webs difficult to study, even in modern times. Here, we use stable carbon and nitrogen isotopes to study the foraging history of a generalist, oceanic predator, the Hawaiian petrel (Pterodroma sandwichensis), which ranges broadly in the Pacific from the equator to near the Aleutian Islands. Our isotope records from modern and ancient, radiocarbon-dated bones provide evidence of over 3,000 y of dietary stasis followed by a decline of ca. 1.8‰ in δ15N over the past 100 y. Fishery-induced trophic decline is the most likely explanation for this sudden shift, which occurs in genetically distinct populations with disparate foraging locations. Our isotope records also show that coincident with the apparent decline in trophic level, foraging segregation among petrel populations decreased markedly. Because variation in the diet of generalist predators can reflect changing availability of their prey, a foraging shift in wide-ranging Hawaiian petrel populations suggests a relatively rapid change in the composition of oceanic food webs in the Northeast Pacific. Understanding and mitigating widespread shifts in prey availability may be a critical step in the conservation of endangered marine predators such as the Hawaiian petrel

Cross-fostering reveals seasonal changes in the relative fitness of two competing species of flycatchers

Spatial and temporal heterogeneity in relative fitness of competing species is a key factor affecting the structure of communities. However, it is not intuitive why species that are ecologically similar should differ in their response to environmental changes. Here we show that two sympatric flycatchers differ in reproductive strategy and in sensitivity to harsh environment. The fitness of collared flycatchers (Ficedula albicollis), which are dominant in interference competition, is more sensitive than the fitness of pied flycatchers (Ficedula hypoleuca) to the seasonal decline in environmental conditions. In order to control for the possibility that this pattern arises solely from differences in microhabitat use (i.e. a local niche differentiation), we performed a partial cross-fostering experiment of young between the two species (i.e. resulting in nests containing young of both species). Our results show that the growth of nestling pied flycatchers is less influenced by the seasonal decline in environmental conditions. We suggest that a life-history trade-off between interference competitive ability and robustness to harsh environment promotes a regional coexistence of the two species

Laser desorption jet-cooling of organic-molecules - cooling characteristics and detection sensitivity

Contains fulltext : 99059.pdf (publisher's version ) (Open Access