On the behavior of titanium within thermal barrier coatings and its influence on residual stress within the TGO

This research focuses on analysing the interaction between three commercially used diffusion coatings and a nickel based superalloy CMSX-4. The coatings applied are alumide, Pt-alumide and Pt-modifed γ/γ′. The research has two main themes, firstly diffusion and secondly oxidation. Results of quantitative EPMA show that titanium diffusion towards the surface varies between coatings, and has a strong correlation with the use of platinum within coatings. The concentrations of Ti within Pt-aluminide coatings after 100 hours oxidation in air at 1100°C were found to be twice as high as those within the plain aluminised CMSX-4 samples. Furthermore uphill diffusion of Ti was observed to occur within Pt-modifed γ/γ′ after the same exposure. In order to examine the effect of platinum additions on the diffusive behavior of titanium, first principle calculations using the density functional theory implementation CASTEP have been performed. In an ordered lattice structure, diffusion of a solute species must occur via the presence of defects, either anti-site (NiAl) or vacancy (VNi). Moreover clustering of these defects leads to increased opportunities for solute diffusion and hence increased diffusion rates within that structure. We have shown that the use of Pt strengthens defect formation and defect clustering within the Ni3Al L12 phase. By increasing the amount of defect clusters Ti can diffuse more freely from the substrate through the coating to the surface

My favourite nematode – Phasmarhabditis hermaphrodita

The terrestrial gastropod parasitic nematode Phasmarhabditis hermaphrodita is the only nematode that evolved to infect and kill slugs and snails. Because of this ability it has been formulated into a biological control agent for gardeners. In this Forum article, the author outlines several reasons why P. hemaphrodita is a nematode that is worth studying, including its ability to control the behaviour and kill slug hosts. The author discusses how P. hemaphrodita is being developed as a model nematode to be used to study the genetic evolution of parasitism, as well as potential research ideas for the future

The gastropod parasitic nematode Phasmarhabditis hermaphrodita does not affect non-target freshwater snails Lymnaea stagnalis, Bithynia tentaculata and Planorbarius corneus

Phasmarhabditis hermaphroditais a lethal parasite of several slug and snail species that has been formulated into a biological control agent. However, the complete host range of this nematode is poorly understood, in particular its potential to affect non-target aquatic snail species. Here we exposed three species of juvenile and adult freshwater snail ( Lymnaea stagnalis, Planorbarius corneusand Bithynia tentaculata) to 30 and 150 P. hermaphroditacm −2and assessed survival, as well as differences in weight for 66 days. We show that P. hermaphroditahas no effect on the survival of L. stagnalis, P. corneusand B. tentaculataafter 66 days of exposure. In summary, we found little evidence of P. hermaphroditacausing mortality to three freshwater snail species at two different life stages and believe that P. hermaphroditawould have little effect on non-target snail species in the wild

On three-dimensional misorientation spaces.

Determining the local orientation of crystals in engineering and geological materials has become routine with the advent of modern crystallographic mapping techniques. These techniques enable many thousands of orientation measurements to be made, directing attention towards how such orientation data are best studied. Here, we provide a guide to the visualization of misorientation data in three-dimensional vector spaces, reduced by crystal symmetry, to reveal crystallographic orientation relationships. Domains for all point group symmetries are presented and an analysis methodology is developed and applied to identify crystallographic relationships, indicated by clusters in the misorientation space, in examples from materials science and geology. This analysis aids the determination of active deformation mechanisms and evaluation of cluster centres and spread enables more accurate description of transformation processes supporting arguments regarding provenance

The Scientific Method as a Scaffold to Enhance Communication Skills in Chemistry

Scientific success in the field of chemistry depends upon the mastery of a wide range of soft skills, most notably scientific writing and speaking. However, training for scientific communication is typically limited at the undergraduate level, where students struggle to express themselves in a clear and logical manner. The underlying issue is deeper than basic technical skills; rather, it is a problem of students’ unawareness of a fundamental and strategic framework for writing and speaking with a purpose. The methodology has been implemented for individual mentorship and in our regional summer research program to deliver a blueprint of thought and reasoning that endows students with the confidence and skills to become more effective communicators. Our didactic process intertwines undergraduate research with the scientific method and is partitioned into six steps, referred to as “phases”, to allow for focused and deep thinking on the essential components of the scientific method. The phases are designed to challenge the student in their zone of proximal development so they learn to extract and ultimately comprehend the elements of the scientific method through focused written and oral assignments. Students then compile their newly acquired knowledge to create a compelling and logical story, using their persuasive written and oral presentations to complete a research proposal, final report, and formal 20 min presentation. We find that such an approach delivers the necessary guidance to promote the logical framework that improves writing and speaking skills. Over the past decade, we have witnessed both qualitative and quantitative gains in the students’ confidence in their abilities and skills (developed by this process), preparing them for future careers as young scientists

Nematode associates and susceptibility of a protected slug (Geomalacus maculosus) to four biocontrol nematodes

The impact of selected entomopathogenic nematodes and Phasmarhabditis hermaphrodita on the European-Union-protected slug Geomalacus maculosus and the sympatric Lehmannia marginata was investigated. There was no significant difference in mortality between slugs treated with nematodes and their controls. The presence of P. hermaphrodita in two G. maculosus cadavers may be the result of necromenic behaviour. This study constitutes the first record of P. californica in Europe

Phylogenetic evidence for the invasion of a commercialized European Phasmarhabditis hermaphrodita lineage into North America and New Zealand

Biological control (biocontrol) as a component of pest management strategies reduces reliance on synthetic chemicals, and seemingly offers a natural approach that minimizes environmental impact. However, introducing a new organism to new environments as a classical biocontrol agent can have broad and unanticipated biodiversity effects and conservation consequences. Nematodes are currently used in a variety of commercial biocontrol applications, including the use of Phasmarhabditis hermaphrodita as an agent targeting pest slug and snail species. This species was originally discovered in Germany, and is generally thought to have European origins. P. hermaphrodita is sold under the trade name Nemaslug®, and is available only in European markets. However, this nematode species was discovered in New Zealand and the western United States, though its specific origins remained unclear. In this study, we analyzed 45 nematode strains representing eight different Phasmarhabditis species, collected from nine countries around the world. A segment of nematode mitochondrial DNA (mtDNA) was sequenced and subjected to phylogenetic analyses. Our mtDNA phylogenies were overall consistent with previous analyses based on nuclear ribosomal RNA (rRNA) loci. The recently discovered P. hermaphrodita strains in New Zealand and the United States had mtDNA haplotypes nearly identical to that of Nemaslug®, and these were placed together in an intraspecific monophyletic clade with high support in maximum likelihood and Bayesian analyses. We also examined bacteria that co-cultured with the nematode strains isolated in Oregon, USA, by analyzing 16S rRNA sequences. Eight different bacterial genera were found to associate with these nematodes, though Moraxella osloensis, the bacteria species used in the Nemaslug® formulation, was not detected. This study provided evidence that nematodes deriving from the Nemaslug® biocontrol product have invaded countries where its use is prohibited by regulatory agencies and not commercially available

A Functional Genomic Screen for Evolutionarily Conserved Genes Required for Lifespan and Immunity in Germline-Deficient <i>C. elegans</i>

<div><p>The reproductive system regulates lifespan in insects, nematodes and vertebrates. In <i>Caenorhabditis elegans</i> removal of germline increases lifespan by 60% which is dependent upon insulin signaling, nuclear hormone signaling, autophagy and fat metabolism and their microRNA-regulators. Germline-deficient <i>C. elegans</i> are also more resistant to various bacterial pathogens but the underlying molecular mechanisms are largely unknown. Firstly, we demonstrate that previously identified genes that regulate the extended lifespan of germline-deficient <i>C. elegans</i> (<i>daf-2</i>, <i>daf-16</i>, <i>daf-12, tcer-1</i>, <i>mir-7.1</i> and <i>nhr-80</i>) are also essential for resistance to the pathogenic bacterium <i>Xenorhabdus nematophila</i>. We then use a novel unbiased approach combining laser cell ablation, whole genome microarrays, RNAi screening and exposure to <i>X. nematophila</i> to generate a comprehensive genome-wide catalog of genes potentially required for increased lifespan and innate immunity in germline-deficient <i>C. elegans</i>. We find 3,440 genes to be upregulated in <i>C. elegans</i> germline-deficient animals in a gonad dependent manner, which are significantly enriched for genes involved in insulin signaling, fatty acid desaturation, translation elongation and proteasome complex function. Using RNAi against a subset of 150 candidate genes selected from the microarray results, we show that the upregulated genes such as transcription factor DAF-16/FOXO, the PTEN homolog lipid phosphatase DAF-18 and several components of the proteasome complex (<i>rpn-6.1</i>, <i>rpn-7</i>, <i>rpn-9</i>, <i>rpn-10</i>, <i>rpt-6</i>, <i>pbs-3</i> and <i>pbs-6</i>) are essential for both lifespan and immunity of germline deficient animals. We also identify a novel role for genes including <i>par-5</i> and T12G3.6 in both lifespan-extension and increased survival on <i>X. nematophila</i>. From an evolutionary perspective, most of the genes differentially expressed in germline deficient <i>C. elegans</i> also show a conserved expression pattern in germline deficient <i>Pristionchus pacificus</i>, a nematode species that diverged from <i>C. elegans</i> 250-400 MYA.</p></div