2,509 research outputs found

    Spectral triples for higher-rank graph C*-algebras

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    Author's accepted version (postprint).This is an Accepted Manuscript of an article published by Royal Danish Library in Mathematica Scandinavica on 06/05/2020.Available online: https://www.mscand.dk/article/view/119260acceptedVersio

    Purification of platinum metal refinery crystalliser effluent using ion-exchange

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    Impala Platinum Metal Refinery (PMR) produces about 30 tonnes of salt every month after crystallisation of effluent from the refining processes. These crystallised salts contain impurities (heavy metals) and are discarded. This poses a danger to the environment and it costs the company large amount money to correctly dump them. There is need to find ways of purifying these salts and find its alternative industrial uses. Major sectors identified using industrial salt were paper mills, pharmaceutical, textile, tanning and paint industrial sectors (Department of Minerals and Energy, 2001). Comparison of the salt composition with salt specifications required for these uses revealed that the salt needed further purification in order to find application in these industrial sectors. Two approaches were proposed; treatment of the crystallized salt to remove impurities and treatment of the crystallizer influent stream before crystallization to ensure a more pure salt is produced..

    Flow Measurements in a Blood-Perfused Collagen Vessel Using X-Ray Micro-Particle Image Velocimetry.

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    Blood-perfused tissue models are joining the emerging field of tumor engineering because they provide new avenues for modulation of the tumor microenvironment and preclinical evaluation of the therapeutic potential of new treatments. The characterization of fluid flow parameters in such in-vitro perfused tissue models is a critical step towards better understanding and manipulating the tumor microenvironment. However, traditional optical flow measurement methods are inapplicable because of the opacity of blood and the thickness of the tissue sample. In order to overcome the limitations of optical method we demonstrate the feasibility of using phase-contrast x-ray imaging to perform microscale particle image velocimetry (PIV) measurements of flow in blood perfused hydrated tissue-representative microvessels. However, phase contrast x-ray images significantly depart from the traditional PIV image paradigm, as they have high intensity background, very low signal-to-noise ratio, and volume integration effects. Hence, in order to achieve accurate measurements special attention must be paid to the image processing and PIV cross-correlation methodologies. Therefore we develop and demonstrate a methodology that incorporates image preprocessing as well as advanced PIV cross-correlation methods to result in measured velocities within experimental uncertainty

    Detecting heterozygosity in shotgun genome assemblies: Lessons from obligately outcrossing nematodes

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    The majority of nematodes are gonochoristic (dioecious) with distinct male and female sexes, but the best-studied species, Caenorhabditis elegans, is a self-fertile hermaphrodite. The sequencing of the genomes of C. elegans and a second hermaphrodite, C. briggsae, was facilitated in part by the low amount of natural heterozygosity, which typifies selfing species. Ongoing genome projects for gonochoristic Caenorhabditis species seek to approximate this condition by intense inbreeding prior to sequencing. Here we show that despite this inbreeding, the heterozygous fraction of the whole genome shotgun assemblies of three gonochoristic Caenorhabditis species, C. brenneri, C. remanei, and C. japonica, is considerable. We first demonstrate experimentally that independently assembled sequence variants in C. remanei and C. brenneri are allelic. We then present gene-based approaches for recognizing heterozygous regions of WGS assemblies. We also develop a simple method for quantifying heterozygosity that can be applied to assemblies lacking gene annotations. Consistently we find that ∼10% and 30% of the C. remanei and C. brenneri genomes, respectively, are represented by two alleles in the assemblies. Heterozygosity is restricted to autosomes and its retention is accompanied by substantial inbreeding depression, suggesting that it is caused by multiple recessive deleterious alleles and not merely by chance. Both the overall amount and chromosomal distribution of heterozygous DNA is highly variable between assemblies of close relatives produced by identical methodologies, and allele frequencies have continued to change after strains were sequenced. Our results highlight the impact of mating systems on genome sequencing projects

    Molecular Dating, Evolutionary Rates, and the Age of the Grasses

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    Many questions in evolutionary biology require an estimate of divergence times but, for groups with a sparse fossil record, such estimates rely heavily on molecular dating methods. The accuracy of these methods depends on both an adequate underlying model and the appropriate implementation of fossil evidence as calibration points. We explore the effect of these in Poaceae (grasses), a diverse plant lineage with a very limited fossil record, focusing particularly on dating the early divergences in the group. We show that molecular dating based on a data set of plastid markers is strongly dependent on the model assumptions. In particular, an acceleration of evolutionary rates at the base of Poaceae followed by a deceleration in the descendants strongly biases methods that assume an autocorrelation of rates. This problem can be circumvented by using markers that have lower rate variation, and we show that phylogenetic markers extracted from complete nuclear genomes can be a useful complement to the more commonly used plastid markers. However, estimates of divergence times remain strongly affected by different implementations of fossil calibration points. Analyses calibrated with only macrofossils lead to estimates for the age of core Poaceae ∼51-55 Ma, but the inclusion of microfossil evidence pushes this age to 74-82 Ma and leads to lower estimated evolutionary rates in grasses. These results emphasize the importance of considering markers from multiple genomes and alternative fossil placements when addressing evolutionary issues that depend on ages estimated for important group

    Teamwork enables high level of early mobilization in critically ill patients

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    Additional file 2. Physiological responses of physiotherapy session. Values expressed as mean ± standard deviation; IB = In bed, IC = In chair, * different from baseline, ≈ different from 0 min
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