479 research outputs found

    Effect of High-Protein Breakfast Meals on Within-Day Appetite and Food Intake in Healthy Men and Women

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    The Rowett Institute and Biomathematics and Statistics Scotland are grateful to the Scottish Government for funding this work. We thank the Rowett Human Nutrition Unit staff for their technical help with the interventions. Staff members who helped include Jean Bryce, Nina Lamza and Karen Taylor. The Rowett Institute and Biomathematics and Statistics Scotland are grateful to the Scottish Government for funding this work.Peer reviewedPublisher PD

    Oxygen Absorption in M87: Evidence for a Warm+Hot ISM

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    We present a re-analysis of the ROSAT PSPC data within the central 100 kpc of M87 to search for intrinsic oxygen absorption similar to that recently measured in several galaxies and groups. Using a spatial-spectral deprojection analysis we find the strongest evidence to date for intrinsic oxygen absorption in the hot gas of a galaxy, group, or cluster. Single-phase plasma models modified by intervening Galactic absorption cannot fit the 0.2-2.2 keV PSPC data as they under-predict the 0.2-0.4 keV region and over-predict the 0.5-0.8 keV region where the emission and absorption residuals are obvious upon visual inspection of the spectral fits. Since the excess emission between 0.2-0.4 keV rules out intrinsic absorption from cold gas or dust, the most reasonable model for the excess emission and absorption features is warm, collisionally ionized gas with a temperature of ~10^6 K. Simple multiphase models (cooling flow, two phases) modified by both intervening Galactic absorption and by a single oxygen edge provide good fits and yield temperatures and Fe abundances of the hot gas that agree with previous determinations by ASCA and SAX. The multiphase models of M87 inferred from the PSPC can account for the excess EUV emission observed with EUVE and the excess X-ray absorption inferred from EINSTEIN and ASCA data above 0.5 keV. Although the total mass of the warm gas implied by the oxygen absorption is consistent with the matter deposited by a cooling flow, the suppression of the mass deposition rate and the distortion of the X-ray isophotes in the region where the radio emission is most pronounced suggest some feedback effect from the AGN on the cooling gas. (Abridged)Comment: 17 pages (13 figures), Accepted for Publication in The Astrophysical Journa

    The mechanism of formation of 8,8-dimethyl[4.2.1.0 3,7]nonan-6-yl acetate (fortesyl acetate) during acetolysis of nopyl toluene-psulfonate

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    Attempts to prepare 2-(2-hydroxyethyl)-6,6-dimethylbicyclo[3.1.1]hept-2-ene (nopol; 1) labelled with deuterium at C-10 by a process of oxidation of the primary alcohol group of nopol to the aldehyde, followed by H/D exchange and reduction back to alcohol, were unsuccessful because various oxidation procedures, including reaction with N-chlorosuccinimide at 278 8C, gave instead a carboxylic acid having an oxygen at C-3. Nopol, labelled at C-11 with deuterium, was obtained through a Prins reaction of b-pinene with deuteriated paraformaldehyde. This labelled nopol was converted into its toluene-p-sulfonate ester, and was solvolysed in acetic acid containing acetate ion to give 8,8-dimethyltricyclo[4.2.1.03,7]nonan-6-yl acetate, which is an earlier reported novel fused ring system (fortesyl acetate; 2 acetate). The position of the label in the product showed that the mechanism of this deep-seated carbon skeletal rearrangement proceeds through the intermediate formation of a cyclobutane ring, followed by shift of a methylene bridge to expand the original cyclobutane ring and then subsequent expansion of the new cyclobutane ring. Calculations of heats of formation of possible ions involved in these shifts confirm the proposed mechanism as the most likely pathway.Junta Nacional de Investigação Científica e Tecnológica. Kuwait. Eschenmoser Trust UK

    Conduction and cooling flows

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    Chandra and XMM-Newton observations have confirmed the presence of large temperature gradients within the cores of many relaxed clusters of galaxies. Here we investigate whether thermal conduction operating over those gradients can supply sufficient heat to offset radiative cooling. Narayan & Medvedev (2001) and Gruzinov (2002) have noted, using published results on cluster temperatures, that conduction within a factor of a few of the Spitzer rate is sufficient to balance bremsstrahlung cooling. From a detailed study of the temperature and emission measure profiles of Abell 2199 and Abell 1835, we find that the heat flux required by conduction is consistent with or below the rate predicted by Spitzer in the outer regions of the core. Conduction may therefore explain the lack of observational evidence for large mass cooling rates inferred from arguments based simply on radiative cooling, provided that conductivity is suppressed by no more than a factor of three below the full Spitzer rate. To stem cooling in the cluster centre, however, would necessitate conductivity values at least a factor of two larger than the Spitzer values, which we consider implausible. This may provide an explanation for the observed star formation and optical nebulosities in cluster cores. The solution is likely to be time dependent. We briefly discuss the possible origin of the cooler gas and the implications for massive galaxies.Comment: 5 pages, 4 figures, accepted by MNRAS. Minor changes following referee's comment

    ROSAT Evidence for Intrinsic Oxygen Absorption in Cooling Flow Galaxies and Groups

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    Using spatially resolved, deprojected ROSAT PSPC spectra of 10 of the brightest cooling flow galaxies and groups with low Galactic column densities we have detected intrinsic absorption over energies ~0.4-0.8 keV in half of the sample. Since no intrinsic absorption is indicated for energies below ~0.4 keV, the most reasonable model for the absorber is collisionally ionized gas at temperatures T=10^{5-6} K with most of the absorption arising from ionized states of oxygen but with a significant contribution from carbon and nitrogen. The soft X-ray emission of this warm gas can explain the sub-Galactic column densities of cold gas inferred within the central regions of most of the systems. Attributing the absorption to ionized gas reconciles the large columns of cold H and He inferred from EINSTEIN and ASCA with the lack of such columns inferred from ROSAT. Within the central ~10-20 kpc, where the constraints are most secure, the estimated mass of the ionized absorber is consistent with most (perhaps all) of the matter deposited by a cooling flow over the lifetime of the flow. Since the warm absorber produces no significant H or He absorption the large absorber masses are consistent with the negligible atomic and molecular H inferred from HI and CO observations of cooling flows. It is also found that if T > ~2x10^5 K then the optical and UV emission implied by the warm gas does not violate published constraints. Finally, we discuss how the prediction of warm ionized gas as the product of mass drop-out in these and other cooling flows can be verified with new CHANDRA and XMM observations. (Abridged)Comment: 17 pages (5 figures), Accepted for publication in ApJ, expanded discussion of multiphase spectral models, theoretical implications of warm gas in cooling flows, and the statistical significance of the oxygen absorptio

    Investigations into the mechanism of action of nitrobenzene as a mild dehydrogenating agent under acid-catalysed conditions

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    Protonated nitrobenzene can be used to dehydrogenate a range of hydrocarbons, which already possess at least one double bond. Kinetic and spectroscopic results, together with known electrode potentials, yield approximate limits within which protonated nitrobenzenes can be expected to effect dehydrogenation of hydroaromatic compounds. A high yielding synthesis of benzo[ j ]fluoranthene is described

    Filtering Genes for Cluster and Network Analysis

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    <p>Abstract</p> <p>Background</p> <p>Prior to cluster analysis or genetic network analysis it is customary to filter, or remove genes considered to be irrelevant from the set of genes to be analyzed. Often genes whose variation across samples is less than an arbitrary threshold value are deleted. This can improve interpretability and reduce bias.</p> <p>Results</p> <p>This paper introduces modular models for representing network structure in order to study the relative effects of different filtering methods. We show that cluster analysis and principal components are strongly affected by filtering. Filtering methods intended specifically for cluster and network analysis are introduced and compared by simulating modular networks with known statistical properties. To study more realistic situations, we analyze simulated "real" data based on well-characterized E. coli and S. cerevisiae regulatory networks.</p> <p>Conclusion</p> <p>The methods introduced apply very generally, to any similarity matrix describing gene expression. One of the proposed methods, SUMCOV, performed well for all models simulated.</p

    WFPC2 Observations of the Cooling Flow Elliptical in Abell 1795

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    We present WFPC2 images of the core of the cooling flow cD galaxy in Abell 1795. An irregular, asymmetric dust lane extends 7 \h75 kpc in projection to the north-northwest. The dust shares the morphology observed in the Hα\alpha and excess UV emission. We see both diffuse and knotty blue emission around the dust lane, especially at the ends. The dust and emission features lie on the edge of the radio lobes, suggesting star formation induced by the radio source or the deflection of the radio jets off of pre-existing dust and gas. We measure an apparent RV_V significantly less than 3.1, implying that the extinction law is not Galactic in the dust lane, or the presence of line emission which is proportional to the extinction. The dust mass is at least 2×105h75−2\times10^{5} h_{75}^{-2} M\solar\ and is more likely to be 6.5×105h75−2\times10^{5} h_{75}^{-2} M\solar.Comment: 14 pages, LaTeX, Figure 4 included, Postscript Figs. 1-3 available at ftp://astro.nmsu.edu/pub/JASON/A1795/, accepted for publication in ApJ Letter

    Toxicity Profile and Pharmacokinetic Study of A Phase I Low-Dose Schedule–Dependent Radiosensitizing Paclitaxel Chemoradiation Regimen for Inoperable Non–Small-Cell Lung Cancer

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    We report the toxicity profile and pharmacokinetic data of a schedule-dependent chemoradiation regimen using pulsed low-dose paclitaxel for radiosensitization in a phase I study for inoperable non-small cell lung cancer (NSCLC)
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