3,048 research outputs found

    Some Intuition behind Large Cardinal Axioms, Their Characterization, and Related Results

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    We aim to explain the intuition behind several large cardinal axioms, give characterization theorems for these axioms, and then discuss a few of their properties. As a capstone, we hope to introduce a new large cardinal notion and give a similar characterization theorem of this new notion. Our new notion of near strong compactness was inspired by the similar notion of near supercompactness, due to Jason Schanker

    The osmotic stress response of ale and lager yeast

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    Brewing ale (Saccharomyces cerevisiae) and lager (Saccharomyces cerevisiae (syn S. pastorianus) yeast populations are subject to biological, chemical and physical stress during the brewing process. Osmotic stress is evident at discreet points throughout this industrial process, yet the impact of this stress on yeast tolerance, defence and repair has not been investigated. Haploid strains of Saccharomyces cerevisiae exhibit different tolerances to hyper-osmotic stress in which the solute concentration of the surrounding medium exceeds the cell's cytoplasm. The osmotolerance of ale and lager yeast to sorbitol and NaCI-induced osmotic stress has not been previously investigated but was observed to be strain, growth phase and solute dependent, reflecting inherent genetic differences in the management of this stress in all cases. It has been postulated that the yeast vacuole plays a central role in the maintenance of physiological activity during osmotic stress. The gross morphological changes occurring in this organelle during osmotic stress were examined. The vacuole of brewing yeast strains was demonstrated to exhibit a highly fragmented morphology, independent of strain, growth phase and osmotic stress. The fragmentation of the yeast vacuole could not be correlated to one external parameter, and was therefore not observed to be a good biomarker of osmotic stress. Saccharomyces cerevisiae exhibits a series of responses to osmotic stress. Cells may demonstrate an innate ability to withstand osmotic stress. In most instances however, osmotolerance is achieved when cells accumulate compatible solutes in order to increase intracellular osmolarity thus promoting retention of cellular water and as a result maintenance of turgor and viability. Yeast cells preferentially accumulate the polyhydric alcohol glycerol, although a detailed study on glycerol accumulation in brewing yeast strains during osmotic stress has not been previously reported. Intracellular compatible solute accumulation was observed to be complex in brewing yeast strains. Analysis of the cytosolic pool of amino acids demonstrated that there were discreet compositional changes during osmotic stress, however no single amino acid was hyper-accumulated. Glycerol accumulation could not be correlated to the intensity of osmotic stress, however the response observed was strain, growth-phase and solute type dependent. PCR detection revealed that the elucidated genes involved in glycerol biosynthesis were present in all production brewing strains examined. Sequence analysis of the GPDJ gene (encoding a cytoplasmic glycerol-3-phosphate dehydrogenase) revealed point mutations in the sequence of the SCB2 (lager) strain sufficient to affect the primary structure of Gpdlp but not its' functionality. In the ale strain SCB8 no such differences occurred. The unusual glycerol profile observed with both strains appeared to be a function of GPDJ and Gpd 1p production. However it was noted that glycerol export may have also contributed to this phenomenon

    Genetic associations with childhood brain growth, defined in two longitudinal cohorts

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    Genome-wide association studies (GWASs) are unraveling the genetics of adult brain neuroanatomy as measured by cross-sectional anatomic magnetic resonance imaging (aMRI). However, the genetic mechanisms that shape childhood brain development are, as yet, largely unexplored. In this study we identify common genetic variants associated with childhood brain development as defined by longitudinal aMRI. Genome-wide single nucleotide polymorphism (SNP) data were determined in two cohorts: one enriched for attention-deficit/hyperactivity disorder (ADHD) (LONG cohort: 458 participants; 119 with ADHD) and the other from a population-based cohort (Generation R: 257 participants). The growth of the brain's major regions (cerebral cortex, white matter, basal ganglia, and cerebellum) and one region of interest (the right lateral prefrontal cortex) were defined on all individuals from two aMRIs, and a GWAS and a pathway analysis were performed. In addition, association between polygenic risk for ADHD and brain growth was determined for the LONG cohort. For white matter growth, GWAS meta-analysis identified a genome-wide significant intergenic SNP (rs12386571, P = 9.09 × 10-9 ), near AKR1B10. This gene is part of the aldo-keto reductase superfamily and shows neural expression. No enrichment of neural pathways was detected and polygenic risk for ADHD was not associated with the brain growth phenotypes in the LONG cohort that was enriched for the diagnosis of ADHD. The study illustrates the use of a novel brain growth phenotype defined in vivo for further study

    Engineering soil organic matter quality: Biodiesel Co-Product (BCP) stimulates exudation of nitrogenous microbial biopolymers

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    Biodiesel Co-Product (BCP) is a complex organic material formed during the transesterification of lipids. We investigated the effect of BCP on the extracellular microbial matrix or ‘extracellular polymeric substance’ (EPS) in soil which is suspected to be a highly influential fraction of soil organic matter (SOM). It was hypothesised that more N would be transferred to EPS in soil given BCP compared to soil given glycerol. An arable soil was amended with BCP produced from either 1) waste vegetable oils or 2) pure oilseed rape oil, and compared with soil amended with 99% pure glycerol; all were provided with 15N labelled KNO3. We compared transfer of microbially assimilated 15N into the extracellular amino acid pool, and measured concomitant production of exopolysaccharide. Following incubation, the 15N enrichment of total hydrolysable amino acids (THAAs) indicated that intracellular anabolic products had incorporated the labelled N primarily as glutamine and glutamate. A greater proportion of the amino acids in EPS were found to contain 15N than those in the THAA pool, indicating that the increase in EPS was comprised of bioproducts synthesised de novo. Moreover, BCP had increased the EPS production efficiency of the soil microbial community (μg EPS per unit ATP) up to approximately double that of glycerol, and caused transfer of 21% more 15N from soil solution into EPS-amino acids. Given the suspected value of EPS in agricultural soils, the use of BCP to stimulate exudation is an interesting tool to consider in the theme of delivering sustainable intensification

    Early Responses of Brassica oleracea Roots to Zinc Supply Under Sufficient and Sub-Optimal Phosphorus Supply

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    © Copyright © 2020 Pongrac, Fischer, Thompson, Wright and White. Shoot zinc (Zn) concentration in Brassica oleracea is affected by soil Zn and phosphorus (P) supply. Most problematic is the negative impact of P fertilizers on Zn concentrations in crops, which makes balancing yield and mineral quality challenging. To evaluate early molecular mechanisms involved in the accumulation of large shoot Zn concentrations regardless of the P supply, two B. oleracea accessions differing in root architecture and root exudates were grown hydroponically for two weeks with different combinations of P and Zn supply. Ionome profiling and deep RNA sequencing of roots revealed interactions of P and Zn in planta, without apparent phenotypic effects. In addition, increasing P supply did not reduce tissue Zn concentration. Substantial changes in gene expression in response to different P and/or Zn supplies in roots of both accessions ensured nutritionally sufficient P and Zn uptake. Numerous genes were differentially expressed after changing Zn or P supply and most of them were unique to only one accession, highlighting their different strategies in achieving nutrient sufficiency. Thus, different gene networks responded to the changing P and Zn supply in the two accessions. Additionally, enrichment analysis of gene ontology classes revealed that genes involved in lipid metabolism, response to starvation, and anion transport mechanisms were most responsive to differences in P and Zn supply in both accessions. The results agreed with previously studies demonstrating alterations in P and Zn transport and phospholipid metabolism in response to reduced P and Zn supply. It is anticipated that improved knowledge of genes responsive to P or Zn supply will help illuminate the roles in uptake and accumulation of P and Zn and might identify candidate genes for breeding high-yield-high-Zn brassicas
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