Low temperature plasma surface modification of stainless steels for ice sliding applications

Stainless steels used in ice sliding applications, such as in the blades of ice skates, ski edges and runners of bobsleigh’s have notoriously poor tribological properties. During the study, microstructure and tribological behavior of AISI 420 and AISI 316 were studied and through the application of low temperature plasma surface modification, it has been possible to improve the base properties exhibited by the materials. Both grades of steel were subjected to a range of plasma surface modifications, using nitriding, carburizing and carbo-nitriding techniques over a set temperature range. Improvements in the surface hardness were documented in all cases. Characterization of the depth of the modified layer was carried out using SEM, GDOES and cross-sectional micro-hardness to obtain optimum conditions for treatment of replica steel blades for use in simulation wear testing. A synthetic ice substitute was created, for tribological testing, and an improvement in performance was observed following the surface modification procedure

Studies on Atmospheric Corrosion Processes in AA2024

Atmospheric corrosion of aluminium alloy AA2024 was investigated using in situ synchrotron micro-tomography, which allows visualisation in a non-destructive manner in real time. The effect of atmospheric variables such as salt type, humidity, exposure time and salt deposition density on the corrosion rate was investigated. It was found that corrosion fissures grow along grain boundaries parallel to the rolling direction of the alloy, reaching a limiting depth, and then spread laterally. The volume of corrosion increases with salt density and relative humidity. Salt type has a limited effect on the volume of corrosion in microtomography measurements where the droplet is constrained at the top of a pin, but in parallel lab-based experiments on plate surfaces, it was found that NaCl and simulated ocean water droplets spread laterally, leading to increased corrosion owing to an increase cathodic area, whereas pure MgCh and CaCh droplets do not spread. Preliminary microtomography work on cycling the relative humidity showed transient increases in localised corrosion during wetting and drying phases, often associated with rapid growth of pmt of a localised cmTosion site, or initiation of new sites

THE SMOOTH WHITNEY FIBERING CONJECTURE AND OPEN BOOKS IN WHITNEY AND BEKKA STRATIFICATIONS

Using continuous controlled liftings of vector fields, we first prove for Bekka's (c)-and hence Whitney (b)-regular stratifications S that near every point of a stratum X with depth Σ (X) = 1 there exists a local C 0,1 foliation. Then we construct a local open book structure near each point of X and use this result to prove the general smooth version of the Whitney fibering conjecture near every point of an arbitrary stratum X of S. As a consequence we improve the Thom-Mather regularity of the local trivialization maps of a proper stratified submersion f : S → M into a manifold. In a famous paper of 1965 H. Whitney proposed a local fibering property around points of a complex analytic variety. More precisely he conjectured that every complex analytic variety V admits a stratification such that a neighbourhood U of each point is fibered by copies of the intersection of U with the stratum M containing the point. He asked also that the fibers be holomorphic manifolds and that their tangent spaces vary continuously as nearby points approach M. Note that if one does not require the continuity of tangent spaces to the fibers then the Thom-Mather isotopy theorem suffices to prove a smooth version of Whitney's conjecture. In 1989 R. Hardt and D. Sullivan gave a proof of a similar conclusion for holomorphic varieties but again without the essential continuity of the tangent spaces to the fibers. From 1993 the first author studied the possibility of obtaining the analogous property in the case of smooth real stratified spaces in his thesis under the direction of the third author who conjectured this property be true for Whitney (b)-regular stratifications

Southern Ocean Seasonal Restratification Delayed by Submesoscale Wind–Front Interactions

Ocean stratification and the vertical extent of the mixed layer influence the rate at which the ocean and atmosphere exchange properties. This process has direct impacts for anthropogenic heat and carbon uptake in the Southern Ocean. Submesoscale instabilities that evolve over space (1–10 km) and time (from hours to days) scales directly influence mixed layer variability and are ubiquitous in the Southern Ocean. Mixed layer eddies contribute to mixed layer restratification, while down-front winds, enhanced by strong synoptic storms, can erode stratification by a cross-frontal Ekman buoyancy flux. This study investigates the role of these submesoscale processes on the subseasonal and interannual variability of the mixed layer stratification using four years of high-resolution glider data in the Southern Ocean. An increase of stratification from winter to summer occurs due to a seasonal warming of the mixed layer. However, we observe transient decreases in stratification lasting from days to weeks, which can arrest the seasonal restratification by up to two months after surface heat flux becomes positive. This leads to interannual differences in the timing of seasonal restratification by up to 36 days. Parameterizing the Ekman buoyancy flux in a one-dimensional mixed layer model reduces the magnitude of stratification compared to when the model is run using heat and freshwater fluxes alone. Importantly, the reduced stratification occurs during the spring restratification period, thereby holding important implications for mixed layer dynamics in climate models as well as physical–biological coupling in the Southern Ocean

Evaluation of Traditional Medicines III: The Mechanism of Immune Modulation by PHELA.

PHELA is a herbal traditional medicine that is under development for use as an immune booster in immune compromised individuals. Therefore, the aim of this study was to determine PHELA’s mechanism of action by observing for changes in cytokine profiles. Four groups of Sprague Dawley rats (n = 8) were treated daily and separately with normal-saline, cyclosporine-A, PHELA-only and PHELA+ cyclosporine-A. Thereafter, 4 animals from each group were sacrificed after 7 and 14 days of treatment. Serum Th1 cytokines (IL-2, IFN-γ and TNF-ά) and Th2 cytokines (IL-4 and IL-10) were measured by ELISA. The concentrations of Th1 cytokines in the PHELA-only treated group were similar to the control group on days 7 and 14. However, the Th1 cytokines were higher in the PHELA+cyclosporine-A treated group compared to cyclosporine-A group, and cyclosporine-A concentrations were similar in both groups. These results show that PHELA did not stimulate Th1 cytokines of a normal immune system but stimulated them when the immune system was suppressed by cyclosporine-A. In conclusion, PHELA is an immune-stimulant to a compromised immune system