Helium additions to MIG shielding gas - an economic option?

An investigation has been carried out to establish the technical and economic benefits of adding two levels of helium to a normal shielding gas. Technically no adverse issues were established using the two levels of helium, and the most significant positive one was the highly beneficial effects on travel speed increase and heat input decrease. Although helium gas carries a significant cost premium, the economic evaluation showed that overall this was a beneficial approach as the man-hour reduction associated with the welding process dominated the process cost effects

Evaluation of gas metal arc welding with alterating shielding gases for use on AA6082T6

Studies have been carried out to determine the effects of implementing alternating shielding gases for 6082T6 aluminium alloy welding. Alternating shielding gases is a newly developed method of supplying shielding gases to the weld area to enhance the efficiency of the standard Gas Metal Arc Welding (GMAW) process. This method involves discretely supplying two different shielding gases to the weld zone at a pre-determined frequency which creates a dynamic action in the weld pool. Several benefits have been identified in relation to supplying shielding gases in this manner including increased travel speed, reduced distortion, reduced porosity and, in the case of specific alternating frequencies, marginal improvements in mechanical properties. All in all, this method of shielding gas delivery presents attractive benefits to the manufacturing community, namely the increased productivity and quality in addition to a reduction in the amount of post-weld straightening required. However, the literature available on this advanced joining process is very scant, especially so for aluminium alloys. For this reason, an evaluation has been carried out on the application of alternating shielding gases for the GMAW process on 6082T6 aluminium alloys

Aspects of the aetiopathogenesis and diagnosis of ovine footrot

Footrot is prevalent in most sheep-producing countries. Two forms are generally recognised: virulent and benign. Virulent footrot has major economic and animal welfare impacts. Footrot has a complex aetiology; the clinical manifestations of the disease result from interactions between the essential causative agent, Dichelobacter nodosus, and the bacterial community of the foot. The severity of these manifestations varies according to environmental conditions and host susceptibility, thus clinical diagnosis of virulent footrot can be challenging, and laboratory tests are used to assist diagnosis. A comparative evaluation of phenotypic and genotypic virulence tests was undertaken, including the elastase test and a qPCR test targeting the aprV2 protease gene, which is thought to be a key virulence marker. The qPCR had a low diagnostic specificity, with aprV2-positive D. nodosus strains detected flocks with clinically benign footrot. As such, aprV2 was deemed an unreliable virulence marker. In contrast, expression of elastase was closely associated with virulence. D. nodosus strains are divisible into ten immunologically distinct serogroups (A to I, M). A culture-independent testing procedure was developed that enhanced the speed and accuracy of serogrouping, and a cPCR test targeting serogroup M was developed. Such a test was previously unavailable. The foot microbiomes of healthy and footrot-affected Merino sheep were characterised and compared using next-generation sequencing and analysis of the bacterial 16S rRNA gene. Fifteen bacterial genera were found to be preferentially abundant on the feet of footrot-affected Merino sheep, several of which were not previously known to contribute to the disease process. A pasture-based experimental model was also developed that provides a more accurate representation of the conditions in which footrot is naturally transmitted and expressed

Optimization of Nanoscale Zero-Valent Iron for the Remediation of Groundwater Contaminants

Nanoscale zero-valent iron (nZVI) is an emerging tool for the remediation of groundwater contaminants. The nanoparticles are capable of reductively destroying or immobilizing a wide range of contaminants. Their small size results in a high surface area to mass ratio, making them much more reactive compared to their more-coarse predecessors. Small particle size also allows nZVI particles to be injected directly into contaminated areas via a well, limiting the above-ground footprint and allowing access to contaminated areas that are beyond the reach of some conventional methods. nZVI technology has the potential to facilitate remediation in difficult situations, improve remediation outcomes, and reduce remediation costs. Using bench-scale laboratory experiments, this research investigates three methods for improving the reactivity and transport characteristics of nZVI, including: optimizing the nanoparticle synthesis process, addition of a polyelectrolyte stabilizer, and amendment of the particles with a palladium catalyst. Optimizing the synthesis method improved reactivity by 72%. Addition of a polyelectrolyte stabilizer further increased nZVI reactivity by 452%, while decreasing mean particle size from 29.3 to 4.6 nm and inhibiting aggregation. Finally, amendment with an optimized amount of 3.3% (w/w) palladium catalyst increased reactivity by another 375% while decreasing the formation of toxic byproducts during contaminant degradation