A fire-mediated recruitment bottleneck provides a possible explanation for the coexistence of trees and grasses in mesic savannas. Nike Air Force 1 Nz The key element of this hypothesis is that saplings are particularly vulnerable to fire because they are small enough to be top-killed by grass fires, but unlike juveniles, they take several years to recover their original size. This limits the number of recruits into the adult size classes. http://www.nikeairforce1nz.nu Thus savanna vegetation may be maintained by a feedback whereby fire restricts the density of adult trees and allows a grass layer to develop, which provides fuel for subsequent fires. Here, we use results from a landscape-scale fire experiment in tropical Australia, to explore the possible existence of a recruitment bottleneck. This experiment compared tree recruitment… and survival over 4 y under regimes of no fire, annual early and annual late dry-season fire. Stem mortality decreased with increasing stem height in the fire treatments but not in the unburnt treatment. Tree recruitment was 76-84% lower in the fire treatments than the unburnt treatment. Cheap Nike Air Max Plus Such fire-induced stem loss of saplings and reduced recruitment to the canopy layer in this eucalypt savanna are consistent with the predictions of the fire-mediated recruitment bottleneck hypothesis.
Following birth, the northern elephant seal ( Mirounga angustirostris ) pups rapidly gain weight by ingesting milk with a high fat content, Cheap Nike Air Max Nz as much as 50%. To better understand the metabolism of the pups during the suckling period, the positional distributions of triacylglycerol fatty acids in both the milk and chylomicra were determined. Extracts of enzymatically digested lipids were separated by thin layer chromatography and the constituent fatty acids were separated and quantified by gas liquid chromatography. http://www.nikeairforce1nz.nu Over 84% of the fatty acids were either monoenoic or saturated, with the ratio of monoenoic to saturated fatty acids ranging between 2.9-4.0. Positional distributional analyses revealed that the very long chain monoenoics (20:1 and 22:1) were located primarily at the sn -1,3… positions of milk triacylglycerols. In the interval between the onset of lactation to the time of weaning, the content of these very long chain monoenoic fatty acids at the sn-1,3 positions increased from 13–37%. At the sn -2 position, the percentage of 18:1 was 3–5-fold higher than 16:1. Analyses indicated that the triacylglycerols in both milk and suckling pup chylomicra were similar. Cheap Nike Air Max 90 Nz This particularly was true for the distributions at the sn -2 position, indicating that milk fats are being absorbed primarily via the 2-monoacylglycerol pathway.
Frequency locking of edge localized modes (ELMs) to the vertical plasma movements induced by magnetic perturbations first demonstrated in TCV was successfully repeated in ASDEX Upgrade. However, the ELMs were triggered in ASDEX Upgrade when the plasma was moving down towards the X-point with a consequent decrease in the plasma current density in the edge region, Air Max 1 Essential in contrast to the previous observation on TCV in which ELMs were triggered when the edge current was increased by an upward plasma movement. http://www.nikeairforce1nz.nu This opposite behaviour observed in the magnetic triggering of ELMs has been investigated by using a free-boundary tokamak simulator, DINA-CH. The passive stabilization loops (PSLs) located inside the vacuum vessel of ASDEX Upgrade produce similar external linking flux changes to those… generated by the G-coil sets in TCV for opposite vertical plasma movements. Therefore, both plasmas experience similar local flux surface expansions near the upper G-coil set and PSL when the ELMs are triggered. Air Max 1 Black In ASDEX Upgrade, however, the localized expansion of the plasma flux surfaces near the upper PSL is observed with the global shrinkage of the plasma column accompanied by the downward plasma movement.