An investigation into the process mineralogy of the Merensky reef at Northam Platinum Limited

Includes abstract.Includes bibliographical references (p. 107-114).This dissertation has investigated the links between the mineralogical characteristics of the Normal, NP2 and P2 Merensky reefs at Northam Platinum Ltd and their flotation performances. Flotation performance was measured in terms of the grade and recovery of the base metal sulphides (chalcopyrite, pentlandite, pyrrhotite and total sulphide) as well as through investigation of mass-water recoveries

An investigation into the link between anomalous PGE concentrations and chromite composition in chromitites within ophiolites

For all three ophiolites, variations in chromitite major and trace element geochemistry occur on several different scales. At the smallest level, single thin sections of chromite may sometimes display large variations in composition. At the next level, intrapod chemical variation can be extensive, though predominantly displaying an inverse correlation between Cr# and Mg#. Finally, interpod variation, and its relationship to stratigraphic height, changes a great deal between ophiolites, sometimes providing an apparently continuous change with height (e.g. Al 'Ays) and in other places (e.g. Shetland) varying discontinuously with height. These differences can provide important clues to the process controlling chromite composition. They suggest that multiple controls may sometimes be involved including, the number of phase crystallizing, post-solidus re-equilibration, fractionation, melt-rock reaction and volatile unmixing.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An investigation into the link between anomalous PGE concentrations and chromite composition in chromitites within ophiolites

For all three ophiolites, variations in chromitite major and trace element geochemistry occur on several different scales. At the smallest level, single thin sections of chromite may sometimes display large variations in composition. At the next level, intrapod chemical variation can be extensive, though predominantly displaying an inverse correlation between Cr# and Mg#. Finally, interpod variation, and its relationship to stratigraphic height, changes a great deal between ophiolites, sometimes providing an apparently continuous change with height (e.g. Al 'Ays) and in other places (e.g. Shetland) varying discontinuously with height. These differences can provide important clues to the process controlling chromite composition. They suggest that multiple controls may sometimes be involved including, the number of phase crystallizing, post-solidus re-equilibration, fractionation, melt-rock reaction and volatile unmixing

Potential of ophiolite complexes to host PGE deposits

All six PGE have been recorded as concentrated at parts per million (ppm) in a number of ophiolite complexes. Occurrences of PGE concentrations in ophiolites are common in podiform chromitite where Os, Ir and Ru may be concentrated to give negative slope chondrite normalised patterns. If sulphur saturation of the magma occurred during chromite crystallisation then Pt and Pd + Rh will also be concentrated in the chromitite giving positive chondrite normalised patterns. PGE-rich ophiolite complexes are those where there has been sufficient mantle melting, in a subduction zone, to extract the PGE at a critical melting interval. Too much melting will dilute this melt with PGEbarren melt and too little melting will not extract the PGE. The Scottish Shetland ophiolite is an example in which all 6 PGE have been concentrated in base metal sulphide-bearing podiform chromitite. It is proposed that if all the PGE are concentrated in podiform chromitite then they crystallised from one PGE-rich melt that was close to sulphur saturation. Exploration for PGE within ophiolites is likely to be enhanced by growing evidence that there is a link between chromite composition and PGE concentration

A study of central galaxy rotation with stellar mass and environment

© 2017. The American Astronomical Society. All rights reserved. We present a pilot analysis of the influence of galaxy stellar mass and cluster environment on the probability of slow rotation in 22 central galaxies at mean redshift z = 0.07. This includes new integral-field observations of five central galaxies selected from the Sloan Digital Sky Survey, observed with the SPIRAL integral-field spectrograph on the Anglo-Australian Telescope. The composite sample presented here spans a wide range of stellar masses, 10.9 < log(M∗/M⊙)lt; 12.0, and are embedded in halos ranging from groups to clusters, 12.9 < log(M 200 Ṁ) < 15.6. We find a mean probability of slow rotation in our sample of P(SR) = 54 ± 7%. Our results show an increasing probability of slow rotation in central galaxies with increasing stellar mass. However, when we examine the dependence of slow rotation on host cluster halo mass, we do not see a significant relationship. We also explore the influence of cluster dominance on slow rotation in central galaxies. Clusters with low dominance are associated with dynamically younger systems. We find that cluster dominance has no significant effect on the probability of slow rotation in central galaxies. These results conflict with a paradigm in which halo mass alone predetermines central galaxy properties

The 6df galaxy survey: The near-infrared fundamental plane of early-type galaxies

We determine the near-infrared Fundamental Plane (FP) for ~10 4 early-type galaxies in the 6-degree Field Galaxy Survey (6dFGS). We fit the distribution of central velocity dispersion, near-infrared surface brightness and half-light radius with a 3D Gaussian model using a maximum-likelihood method. The model provides an excellent empirical fit to the observed FP distribution and the method proves robust and unbiased. Tests using simulations show that it gives superior results to regression techniques in the presence of significant and correlated uncertainties in all three parameters, censoring of the data by various selection effects and outliers in the data sample. For the 6dFGS J-band sample we find an FP with Re∝σ01.52±0.03Ie-0.89±0.01, similar to previous near-infrared determinations and consistent with the H- and K-band FPs once allowance is made for differences in mean colour. The overall scatter in R e about the FP is σ r = 29 per cent, and is the quadrature sum of an 18 per cent scatter due to observational errors and a 23 per cent intrinsic scatter. Because of the Gaussian distribution of galaxies in FP space, σ r is not the distance error, which we find to be σ d = 23 per cent. Using group richness and local density as measures of environment, and morphologies based on visual classifications, we find that the FP slopes do not vary with environment or morphology. However, for fixed velocity dispersion and surface brightness, field galaxies are on average 5 per cent larger than galaxies in groups or higher density environments, and the bulges of early-type spirals are on average 10 per cent larger than ellipticals and lenticulars. The residuals about the FP show significant trends with environment, morphology and stellar population. The strongest trend is with age, and we speculate that age is the most important systematic source of offsets from the FP, and may drive the other trends through its correlations with environment, morphology and metallicity. These results will inform our use of the near-infrared FP in deriving relative distances and peculiar velocities for 6dFGS galaxies

Baby Steps - a structured group education programme with accompanying mobile web application designed to promote physical activity in women with a history of gestational diabetes: study protocol for a randomised controlled trial.

Background A diagnosis of gestational diabetes (GDM) is associated with an over sevenfold increase in the risk of developing type 2 diabetes (T2D), while among parous women with T2D, up to 30% have a history of GDM. Lifestyle interventions have been shown to reduce the risk of incident T2D in adults with impaired glucose tolerance, including in women with a history of GDM. The aim of this study is to establish whether a group self-management education programme, supported by a mobile web application, can improve levels of physical activity at 12 months in women who have had GDM. Methods The study is a randomised controlled trial with follow-up at 6 and 12 months. Primary outcome is change in objectively measured average daily physical activity at 12 months. Secondary outcomes include lipid profile, blood pressure, glycated haemoglobin, obesity, smoking and alcohol status, self-reported physical activity, anxiety, depression and quality of life. Participants are recruited from maternity and diabetes departments in hospital trusts in two sites in the UK. Women aged > 18 years, with a diagnosis of GDM during any pregnancy in the previous 60 months are eligible. Participants need to have a good understanding of written and verbal English, be able to give informed consent and have access to a smart-phone. Women who are pregnant or have type 1 or type 2 diabetes are not eligible. In total, 290 participants will be recruited and randomly assigned, with stratification for age and ethnicity, to either the control group, receiving usual care, or the intervention group who are invited to participate in the Baby Steps programme. This comprises a group education programme and access to a mobile web application which provides an education component and interacts with a wrist-worn activity monitor providing automated messages, setting challenges and encouraging motivation. Discussion If effective, the Baby Steps programme could be translated into a primary care-based intervention that women with GDM are referred to in the postnatal period. This could help them make lifestyle changes that could reduce their future risk of T2D. Trial registration ISRCTN, ISRCTN17299860. Registered on 5 April 2017