Grain morphology of as-cast wrought aluminium alloys

Two of the most important microstructural features of alloys are the grain size and the dendrite arm spacing (DAS). Both grain refinement and the DAS depend upon alloy composition through constitutional undercooling, but in different ways. Grain size tends to be related to the initial rate of development of constitutional undercooling, whilst the DAS is more related to the amount of solute build-up towards the end of the solidification process. This means that element additions that have a large effect on the grain size, e.g. Ti, have much less effect on the DAS. With examples from a range of wrought Al alloys, this paper investigates how the interaction between alloy content, grain refiner additions and cooling rate affect the grain size, DAS and the grain morphology obtained in an alloy

Effects of forming route and heat treatment on the distortion behaviour of case-hardened martensitic steel type S156

The distortion behaviour of carburised and fully heat treated Ni-Cr-Mo martensitic steel (S156) has been experimentally evaluated. Dimensional measurements of Navy c-ring distortion coupons during interrupted heat treatment process for parts manufactured from two forming routes, hot forging and machined from as received bar, was performed. Metallurgical analysis was carried out to attempt to relate the observed microstructural characteristics with measured process induced distortion. The carburisation process was found to be the most severe in terms of inducing distortion. It was found that additional heat treatments during the process results in a larger final distortion. Machining parts from forgings results in higher distortions than that of those machined directly from as received bar due to the added thermal processing history. An FE simulation of the carburisation process for a c-ring coupon is presented

Exploring the possibilities for sustainable future growth in business and technology management, pp664-671.

A paper which examines the professionalisation of political campaigns in Southern Africa, using comparative methodology to examine the cases of Malawi and South Africa, selecting prominent political organisations in each

The application of metabolomic profiling to the effects of physical activity

Physical activity and exercise are potent lifestyle interventions for the reduction of several psychosomatic risks, including cardiovascular disease, diabetes and mild-to-moderate depression. The current review describes the studies which have utilised a metabolomics/ metabolite profiling approach in combination with exercise in the period between 1999-2014 in predominantly healthy subjects (N:64) and in a smaller subset of patient cohorts (N:10) between 2011-2014. A broad range of intervention types were used in both healthy and patient cohorts with varying exercise regimes with or without supplement use. Effects on purine metabolism, which have been known for over 40 years, were by far the most well-cited and persistent finding. Other reported effects included observations of: glucocorticoid and androgen metabolism, glycolysis and Krebs cycle, gluconeogenesis, fatty acid metabolism, fatty acid oxidation and pantothenic acid, amino acid oxidation, tryptophan metabolism and effects on microbiome metabolites. The discussion section draws observations from the very disparate studies together and links them to the general aspects of human metabolism

Social life and political trust in China: Searching for machers and schmoozers

Previous literature has provided little evidence regarding the ways in which China’s burgeoning social life and rapid urbanization shape Chinese people’s level of trust in their government leaders. This article builds on Robert Putnam’s conceptualization of maching and schmoozing as formal and informal forms of social involvement, respectively. Using the 2012 Chinese General Social Survey, we identify four types of participants in social involvement, namely the inactives, machers, schmoozers and all-rounders, to untangle various aspects of social life in China. Our empirical analysis shows that the sociodemographic positions of the four types of social involvement are largely distinct. Our findings also contribute to the study of political trust by offering insight into the complicated associations between social involvement, hukou status and political trust in contemporary Chinese society

Structure and Metal Binding Properties of ZnuA, a Periplasmic Zinc Transporter from \u3cem\u3eEscherichia coli\u3c/em\u3e

ZnuA is the periplasmic Zn2+-binding protein associated with the high-affinity ATP-binding cassette ZnuABC transporter from Escherichia coli. Although several structures of ZnuA and its homologs have been determined, details regarding metal ion stoichiometry, affinity, and specificity as well as the mechanism of metal uptake and transfer remain unclear. The crystal structures of E. coli ZnuA (Eco-ZnuA) in the apo, Zn2+-bound, and Co2+-bound forms have been determined. ZnZnuA binds at least two metal ions. The first, observed previously in other structures, is coordinated tetrahedrally by Glu59, His60, His143, and His207. Replacement of Zn2+ with Co2+ results in almost identical coordination geometry at this site. The second metal binding site involves His224 and several yet to be identified residues from the His-rich loop that is unique to Zn2+ periplasmic metal binding receptors. Electron paramagnetic resonance and X-ray absorption spectroscopic data on CoZnuA provide additional insight into possible residues involved in this second site. The second site is also detected by metal analysis and circular dichroism (CD) titrations. Eco-ZnuA binds Zn2+ (estimated K d \u3c 20 nM), Co2+, Ni2+, Cu2+, Cu+, and Cd2+, but not Mn2+. Finally, conformational changes upon metal binding observed in the crystal structures together with fluorescence and CD data indicate that only Zn2+ substantially stabilizes ZnuA and might facilitate recognition of ZnuB and subsequent metal transfer

Metabolomic profiling of submaximal exercise at a standardised relative intensity in healthy adults

Ten physically active subjects underwent two cycling exercise trials. In the first, aerobic capacity (VO2max) was determined and the second was a 45 min submaximal exercise test. Urine samples were collected separately the day before (day 1) , the day of (day 2), and the day after (day 3) the submaximal exercise test (12 samples per subject). Metabolomic profiling of the samples was carried out using hydrophilic interaction chromatography (HILIC) coupled to an Orbitrap Exactive mass spectrometer. Data were extracted, database searched and then subjected to principle components (PCA) and orthogonal partial least squares (OPLSDA) modelling. The best results were obtained from pre-treating the data by normalising the metabolites to their mean output on days 1 and 2 of the trial. This allowed PCA to separate the day 2 first void samples (D2S1) from the day 2 post-exercise samples (D2S3) PCA also separated the equivalent samples obtained on day 1 (D1S1 and D1S3). OPLSDA modelling separated both the D2S1 and D2S3 samples and D1S1 and D1S3 samples. The metabolites affected by the exercise samples included a range of purine metabolites and several acyl carnitines. Some metabolites were subject to diurnal variation these included bile acids and several amino acids, the variation of these metabolites was similar on day 1 and day 2 despite the exercise intervention on day 2. Using OPLS modelling it proved possible to identify a single abundant urinary metabolite provisionally identified as oxo-aminohexanoic acid (OHA) as being strongly correlated with VO2max when the levels in the D2S3 samples were considered

Brazing development and interfacial metallurgy study of tungsten and copper joints with eutectic gold copper brazing alloy

Current proposals for the divertor component of a thermonuclear fusion reactor include tungsten and copper as potentially suitable materials. This paper presents the procedures developed for the successful brazing of tungsten to oxygen free high conductivity (OFHC) copper using a fusion appropriate gold based brazing alloy, Orobraze 890 (Au80Cu20). The objectives were to develop preparation techniques and brazing procedures in order to produce a repeatable, defect free butt joint for tungsten to copper. Multiple brazing methods were utilised and brazing parameters altered to achieve the best joint possible. Successful and unsuccessful brazed specimens were sectioned and analysed using optical and scanning electron microscopy, EDX analysis and ultrasonic evaluation. It has been determined that brazing with Au80Cu20 has the potential to be a suitable joining method for a tungsten to copper joint