8,167 research outputs found

    Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles

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    yesA range of twelve stabilised phosphonium ylides containing tetrahydrofuran, tetrahydropyran or 2,2- dimethyl-1,3-dioxolane rings have been prepared and fully characterised, including one X-ray structure determination of each type. The X-ray structures confirm the PvC and CvO functions to be syn and all the compounds undergo thermal extrusion of Ph3PO to give the corresponding alkynes. In some cases there is also competing loss of Ph3P to give different carbene-derived products and evidence has been obtained for the generation of 2-phenyloxete in this way. Raising the pyrolysis temperature leads in several cases to new secondary reactions of the alkyne products involving a sequence of alkyne to vinylidene isomerisation, intramolecular CH insertion, and retro Diels Alder reaction

    Assessing cardiovascular status: a guide for acute nurses

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    Many patients admitted to acute care areas of a hospital experience cardiovascular compromise due to conditions such as acute myocardial infarction (AMI), acute coronary syndrome or exacerbations of chronic heart failure. Additionally, patients can experience cardiovascular collapse due to bleeding or cardiac arrhythmias postoperatively. As a consequence, nurses in acute care settings need to be competent in assessing the cardiovascular status of adult patients. The authors provide a framework for assessing the cardiovascular status of patients in acute care settings using the determinants of cardiac output. They provide a brief review of the determinants of cardiac output before discussing both the aims of cardiovascular assessment and how to perform, such an assessment. (non- author abstract)<br /

    Volatile hydrocarbons inhibit methanogenic crude oil degradation

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    Methanogenic degradation of crude oil in subsurface sediments occurs slowly, but without the need for exogenous electron acceptors, is sustained for long periods and has enormous economic and environmental consequences. Here we show that volatile hydrocarbons are inhibitory to methanogenic oil biodegradation by comparing degradation of an artificially weathered crude oil with volatile hydrocarbons removed, with the same oil that was not weathered. Volatile hydrocarbons (nC5-nC10, methylcyclohexane, benzene, toluene, and xylenes) were quantified in the headspace of microcosms. Aliphatic (n-alkanes nC12-nC34) and aromatic hydrocarbons (4-methylbiphenyl, 3-methylbiphenyl, 2-methylnaphthalene, 1-methylnaphthalene) were quantified in the total hydrocarbon fraction extracted from the microcosms. 16S rRNA genes from key microorganisms known to play an important role in methanogenic alkane degradation (Smithella and Methanomicrobiales) were quantified by quantitative PCR. Methane production from degradation of weathered oil in microcosms was rapid (1.1 ± 0.1 μmol CH4/g sediment/day) with stoichiometric yields consistent with degradation of heavier n-alkanes (nC12-nC34). For non-weathered oil, degradation rates in microcosms were significantly lower (0.4 ± 0.3 μmol CH4/g sediment/day). This indicated that volatile hydrocarbons present in the non-weathered oil inhibit, but do not completely halt, methanogenic alkane biodegradation. These findings are significant with respect to rates of biodegradation of crude oils with abundant volatile hydrocarbons in anoxic, sulphate-depleted subsurface environments, such as contaminated marine sediments which have been entrained below the sulfate-reduction zone, as well as crude oil biodegradation in petroleum reservoirs and contaminated aquifers
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