Corrosion of Aluminum in Alkaline Solutions

Aluminum has been an important member of the metal group since its isolation about 100 years ago. It has sprung into prominence in the commercial field and in household use in the last thirty years. The metal is light, possesses good thermal and electrical conductivity and as an alloy with other metals takes on a surprising degree of strength. The problem of producing aluminum cheaply enough to make it practical has finally been overcome to a great extent. It now remains to be seen just what further uses there are to which this new metal may be put. Aluminum may be hardened and strengthened by addition of other metals but the attack which it suffers from acids and alkalines is a major shortcoming. Many experiments have been carried out to reveal methods by which corrosion o-r aluminum may be minimized. Some of these methods are practical while others are not. However, the problem of coping with the greatest problem in metallurgy appealed to the author to such an extent that he has tended his efforts toward the general information which experimental corrosion may afford. From this information, certain conclusions can be drawn which may be of value in facing the corrosion problem

The edge of the M87 halo and the kinematics of the diffuse light in the Virgo cluster core

We present high resolution FLAMES/VLT spectroscopy of intracluster planetary nebula (ICPN) candidates, targeting three new fields in the Virgo cluster core with surface brightness down to mu_B = 28.5. Based on the projected phase space information we separate the old and 12 newly-confirmed PNs into galaxy and intracluster components. The M87 PNs are confined to the extended stellar envelope of M87, within a projected radius of ~ 160 kpc, while the ICPNs are scattered across the whole surveyed region between M87 and M86. The velocity dispersions determined from the M87 PNs at projected radii of 60 kpc and 144 kpc show that the galaxy's velocity dispersion profile decreases in the outer halo, down to 78 +/- 25 km/s. A Jeans model for the M87 halo stars in the gravitational potential traced by the X-ray emission fits the observed velocity dispersion profile only if the stellar orbits are strongly radially anisotropic (beta ~= 0.4 at r ~= 10 kpc increasing to 0.8 at the outer edge), and if additionally the stellar halo is truncated at ~= 150 kpc average elliptical radius. From the spatial and velocity distribution of the ICPNs we infer that M87 and M86 are falling towards each other and that we may be observing them just before the first close pass. The inferred luminosity-specific PN numbers for the M87 halo and the ICL are in the range of values observed for old (> 10 Gyr) stellar populations (abridged).Comment: Accepted for publication in Astronomy and Astrophysics. 16 pages, 14 figures and 4 table

Microplasma technology for influencing cell-surface interactions

Cataracts are the most common cause of preventable blindness worldwide. During cataract surgery a polymeric intraocular lens (IOL) is used to replace the cloudy natural lens. The most common post-operative complication is posterior capsule opacification (PCO). PCO is a wound healing response related to scarring, in which cellular changes disrupt the light path to the back of the eye through various processes, requiring a costly surgery to restore vision. The material of the IOL has been shown to affect PCO and it is hypothesised that the surface modification of IOL materials may be able to reduce the incidence of PCO. The use of plasmas established in the field of biomaterials modification and atmospheric pressure processes have significant benefits over the previous low pressure systems. In this work investigates the use of an atmospheric pressure plasma jet to modify the surface properties of polymeric materials, with the aim of developing a surface treatment method for use on IOLs. Materials and Methods The centre of polystyrene (PS) and poly(methyl methacrylate)(PMMA) surfaces were treated with an atmospheric pressure microplasma jet. The modification of surfaces was characterised by spatially resolved water contact angle, x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). LECs were seeded onto surfaces and grown for 1-7 days. Cell attachment, growth and morphology were examined microscopically. The concentrations of some cytokines implicated in PCO (transforming growth factor-β2, basic fibroblast growth factor, interleukin-1, interleukin-6, and tumour necrosis factor-α) in culture medium were examined at specific time points. Tissue culture polystyrene and untreated materials served as controls. Atmospheric pressure plasma polymerisation of amine containing monomers using a plasma jet was also investigated. Results and Discussions The size of surface treatment could be tailored by altering flow rate and sample-nozzle distance. Surface treatment was due to an increase in surface oxygen content and plasma treatment did not cause a significant change in surface roughness. Plasma treatment increased the LEC adhesion to substrates. LECs were densely populated in the centre of treated materials and cells lacked the cobblestone morphology typical of epithelial cells. The secretion of inflammatory cytokines by LECs grown on plasma treated surfaces did not appear to be up-regulated in comparison to tissue culture polystyrene, however these results are preliminary. This work demonstrated that atmospheric pressure plasma polymerisation can be achieved using the plasma jet system to incorporate nitrogen functionalisation onto PS surfaces; however oxygen was also incorporated onto surfaces. Conclusions This work demonstrates that an atmospheric pressure microplasma jet can be used to modify surfaces in a spatially defined manner, without damaging the polymer surfaces. The increase in surface oxygen promotes cell adhesion which can be confined to an are