Effects of mechanically separated dairy cow slurry on grazing performance

No abstract available

Calibration of Large BGO and NAI Detectors Using 270 MeV 3-He Ions

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

A macronutrient bulletin for the prairies

Non-Peer ReviewedThis paper briefly highlights some of the contents of a recently completed bulletin, which provides an up-to-date record of the status of our knowledge with regards to crop responses to, and impact on the environment of N, P, K and s, on the Canadian prairies. This 12 Chapter, 527 page book presents information on nutrient balances, trends in fertility levels of soils, nitrogen use efficiency, N, P, K and S cycles, fertilizer N practices, the influence of nutrients on soil organic matter, response of. forages to nutrients, biotechnology and crop nutrition, and the impact of nutrients on the environment. This manuscript, which was prepared through funding provided under the Canada-Saskatchewan Environmental Sustainability Initiative (ESI), should be of considerable assistance to students, educators, scientists and agricultural extensionists in the three prairie provinces

A new apparatus for determining the shrinkage limit of clay soils

A new apparatus for the determination of shrinkage limit is described. Two versions have been produced: a manually operated prototype ‘version1' followed by an automated version named SHRINKiT. Test results using the former for British and overseas clay soils are described and comparisons made with the British Standards preferred method. A further set of test results is described for SHRINKiT. However, it was not possible to compare these with the BS 1377 method owing to the introduction of a ban on the use of mercury in the British Geological Survey's geotechnical laboratories. The new method is set in the context of the huge cost of shrink/swell-related subsidence damage in Britain and the relative disuse of both BS 1377 methods for shrinkage limit, for reasons of safety. The shrinkage behaviour of different soils types and sample states is discussed, in addition to the advantages and disadvantages of the new method

Faster juvenile growth promotes earlier sex change in a protandrous hermaphrodite (barramundi Lates calcarifer)

The relationship between growth and sexual maturation is central to understanding the dynamics of animal populations which exhibit indeterminate growth. In sequential hermaphrodites, which undergo post-maturation sex change, the size and age at which sex change occurs directly affects reproductive output and hence population productivity. However, these traits are often labile, and may be strongly influenced by heterogenous growth and mortality rates. We analysed otolith microstructure of a protandrous (i.e., male-to-female) fish (barramundi Lates calcarifer) to examine growth in relation to individual variation in the timing of sex change. Growth trajectories of individuals with contrasting life histories were examined to elucidate the direction and extent to which growth rate influences the size and age individuals change sex. Then, the relationships between growth rate, maturation schedules and asymptotic maximum size were explored to identify potential trade-offs between age at female maturity and growth potential. Rapid growth was strongly associated with decreased age at sex change, but this was not accompanied by a decrease in size at sex change. Individuals that were caught as large females grew faster than those caught as males, suggesting that fast-growing individuals ultimately obtain higher fitness and therefore make a disproportionate contribution to population fecundity. These results indicate that individual-level variation in maturation schedules is not reflective of trade-offs between growth and reproduction. Rather, we suggest that conditions experienced during the juvenile phase are likely to be a key determinant of post-maturation fitness. These findings highlight the vulnerability of sex-changing species to future environmental change and harvest

Deglacial changes in flow and frontal structure through the Drake Passage

The oceanic gateways of the Drake Passage and the Agulhas Current are critical locations for the inflow of intermediate-depth water masses to the Atlantic, which contribute to the shallow return flow that balances the export of deep water from the North Atlantic. The thermohaline properties of northward flowing intermediate water are ultimately determined by the inflow of water through oceanic gateways. Here, we focus on the less well-studied “Cold Water Route” through the Drake Passage. We present millennially-resolved bottom current flow speed and sea surface temperature records downstream of the Drake Passage spanning the last 25,000 yr. We find that prior to 15 ka, bottom current flow speeds at sites in the Drake Passage region were dissimilar and there was a marked anti-phasing between sea surface temperatures at sites upstream and downstream of the Drake Passage. After 14 ka, we observe a remarkable convergence of flow speeds coupled with a sea surface temperature phase change at sites upstream and downstream of Drake Passage. We interpret this convergence as evidence for a significant southward shift of the sub-Antarctic Front from a position north of Drake Passage. This southward shift increased the through-flow of water from the Pacific, likely reducing the density of Atlantic Intermediate Water. The timing of the southward shift in the sub-Antarctic Front is synchronous with a major re-invigoration of Atlantic Meridional Overturning Circulation, with which, we argue, it may be linked

Domain Wall Resistance in Perpendicular (Ga,Mn)As: dependence on pinning

We have investigated the domain wall resistance for two types of domain walls in a (Ga,Mn)As Hall bar with perpendicular magnetization. A sizeable positive intrinsic DWR is inferred for domain walls that are pinned at an etching step, which is quite consistent with earlier observations. However, much lower intrinsic domain wall resistance is obtained when domain walls are formed by pinning lines in unetched material. This indicates that the spin transport across a domain wall is strongly influenced by the nature of the pinning.Comment: 9 pages, 3 figure

The endogenous cannabinoid anandamide increases human airway epithelial cell permeability through an arachidonic acid metabolite

Injury to the bronchial epithelium in respiratory diseases such as asthma and COPD results in the lossof barrier function and an elevated sensitivity to environmental insults. An increased release of theendogenous cannabinoid, anandamide in response to inhalation of allergen in asthmatic patients hasbeen reported. The aim of this study was, therefore, to determine the effects of endocannabinoids onbronchial epithelial cell permeability and to investigate the mechanisms involved.Calu-3 human bronchial epithelial cells were cultured at air–liquid interface to allow developmentof tight junctions. Changes in Transepithelial Electrical Resistance (TEER), a reflection of epithelial per-meability, were measured at various time points post-treatment, and expression of the tight junctionproteins, occludin and ZO-1, were determined using Western immunoblotting.Anandamide produced a significant reduction in TEER, which was unaffected by cannabinoid receptorantagonists, but attenuated by URB597, an inhibitor of fatty acid amide hydrolase, and by a combinationof cyclooxygenase (COX) and lipoxygenase (LOX) blockade. The anandamide metabolite, arachidonicacid, showed similar TEER decrease that was also prevented in the presence of COX and LOX inhibitor.Expression of occludin and ZO-1 were also reduced by anandamide.These findings indicate a pro-inflammatory-like effect of anandamide on bronchial epithelial per-meability, mediated by cyclooxygenase and lipoxygenase metabolites, and suggest that inhibition ofanandamide degradation might provide a novel approach to treat airway inflammation

Relative Equilibria in the Four-Vortex Problem with Two Pairs of Equal Vorticities

We examine in detail the relative equilibria in the four-vortex problem where two pairs of vortices have equal strength, that is, \Gamma_1 = \Gamma_2 = 1 and \Gamma_3 = \Gamma_4 = m where m is a nonzero real parameter. One main result is that for m > 0, the convex configurations all contain a line of symmetry, forming a rhombus or an isosceles trapezoid. The rhombus solutions exist for all m but the isosceles trapezoid case exists only when m is positive. In fact, there exist asymmetric convex configurations when m < 0. In contrast to the Newtonian four-body problem with two equal pairs of masses, where the symmetry of all convex central configurations is unproven, the equations in the vortex case are easier to handle, allowing for a complete classification of all solutions. Precise counts on the number and type of solutions (equivalence classes) for different values of m, as well as a description of some of the bifurcations that occur, are provided. Our techniques involve a combination of analysis and modern and computational algebraic geometry