An experimental investigation into resonance dry grinding of hardened steel and nickel alloys with element of MQL

Current policies on environmental issues put extra pressures on manufacturing processes to be resource efficient and eco-friendly. However, in grinding processes, large amounts of cutting fluids are used. These fluids are not environmental friendly thus require proper management before disposal with associated cost. Hence, this work sets to explore low-frequency vibration in grinding in order to improve coolant application in conventional grinding at the first stage with the aim to introduce this into high efficiency deep grinding (HEDG) at latter stage. An attempt is made to grind nickel alloys with minimum quantity lubricant (MQL) as oppose to flood cooling. To achieve this with minimum alterations to the machine tool, a piezo-driven workpiece holder was developed for surface grinding. This simple innovative workpiece holder allowed oscillating during actual grinding process. However, this paper presents the results of low-frequency oscillatory grinding in dry and near-dry conditions. The response of the machine tool spindle unit is presented alongside with the workpiece holder response. In this investigation, hardened steels and nickel alloys were ground with vibration assistance. The grinding forces are illustrated together with the surface finish. The wheel performance is given in terms of grinding ratio

Genetic variability and ontogeny predict microbiome structure in a disease-challenged montane amphibian

Amphibian populations worldwide are at risk of extinction from infectious diseases, including chytridiomycosis caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). Amphibian cutaneous microbiomes interact with Bd and can confer protective benefits to the host. The composition of the microbiome itself is influenced by many environment- and host-related factors. However, little is known about the interacting effects of host population structure, genetic variation and developmental stage on microbiome composition and Bd prevalence across multiple sites. Here we explore these questions in Amietia hymenopus, a disease-affected frog in southern Africa. We use microsatellite genotyping and 16S amplicon sequencing to show that the microbiome associated with tadpole mouthparts is structured spatially, and is influenced by host genotype and developmental stage. We observed strong genetic structure in host populations based on rivers and geographic distances, but this did not correspond to spatial patterns in microbiome composition. These results indicate that demographic and host genetic factors affect microbiome composition within sites, but different factors are responsible for host population structure and microbiome structure at the between-site level. Our results help to elucidate complex within- and among- population drivers of microbiome structure in amphibian populations. That there is a genetic basis to microbiome composition in amphibians could help to inform amphibian conservation efforts against infectious diseases

IBD genetics and the gut microbiome

The pathogenesis of inflammatory bowel disease (IBD) is determined by multiple genetic variants and by gut microbiota. The role of interactions between these two factors has emerged recently. In this chapter, we focus on the crosstalk of gut microbiota and IBD genetic risk factors and give a review on the current progress and perspective of this research field.</p

The transcriptional architecture of phenotypic dimorphism

The profound differences between the sexes in gene expression are increasingly used to study the molecular basis of sexual dimorphism, sexual selection and sexual conflict . Studies of transcriptional architecture, based on comparisons of gene expression, have been implemented on a wide variety of other intra - specific variation. These efforts are based on key assumptions regarding the relationship between transcriptional architecture, phenotypic variation and the target of selection. Some of these assumptions are better supported by available evidence than others. In all cases, the evidence is largely circumstantial, leaving considerable gaps in our understanding of the relationship between transcriptional and phenotypic dimorphism