5,660 research outputs found

    Increased H2_2CO production in the outer disk around HD 163296

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    Three formaldehyde lines were observed (H2_2CO 303_{03}--202_{02}, H2_2CO 322_{22}--221_{21}, and H2_2CO 321_{21}--220_{20}) in the protoplanetary disk around the Herbig Ae star HD 163296 with ALMA at 0.5 arcsecond (60 AU) spatial resolution. H2_2CO 303_{03}--202_{02} was readily detected via imaging, while the weaker H2_2CO 322_{22}--221_{21} and H2_2CO 321_{21}--220_{20} lines required matched filter analysis to detect. H2_2CO is present throughout most of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of the H2_2CO emission is likely caused by an optically thick dust continuum. The H2_2CO radial intensity profile shows a peak at 100 AU and a secondary bump at around 300 AU, suggesting increased production in the outer disk. Different parameterizations of the H2_2CO abundance were compared to the observed visibilities with χ2\chi^2 minimization, using either a characteristic temperature, a characteristic radius or a radial power law index to describe the H2_2CO chemistry. Similar models were applied to ALMA Science Verification data of C18^{18}O. In all modeling scenarios, fits to the H2_2CO data show an increased abundance in the outer disk. The overall best-fit H2_2CO model shows a factor of two enhancement beyond a radius of 270±\pm20 AU, with an inner abundance of 2 ⁣ ⁣5×10122\!-\!5 \times 10^{-12}. The H2_2CO emitting region has a lower limit on the kinetic temperature of T>20T > 20 K. The C18^{18}O modeling suggests an order of magnitude depletion in the outer disk and an abundance of 4 ⁣ ⁣12×1084\!-\!12 \times 10^{-8} in the inner disk. The increase in H2_2CO outer disk emission could be a result of hydrogenation of CO ices on dust grains that are then sublimated via thermal desorption or UV photodesorption, or more efficient gas-phase production beyond about 300 AU if CO is photodisocciated in this region

    Classifying the embedded young stellar population in Perseus and Taurus & the LOMASS database

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    Context. The classification of young stellar objects (YSOs) is typically done using the infrared spectral slope or bolometric temperature, but either can result in contamination of samples. More accurate methods to determine the evolutionary stage of YSOs will improve the reliability of statistics for the embedded YSO population and provide more robust stage lifetimes. Aims. We aim to separate the truly embedded YSOs from more evolved sources. Methods. Maps of HCO+ J=4-3 and C18O J=3-2 were observed with HARP on the James Clerk Maxwell Telescope (JCMT) for a sample of 56 candidate YSOs in Perseus and Taurus in order to characterize emission from high (column) density gas. These are supplemented with archival dust continuum maps observed with SCUBA on the JCMT and Herschel PACS to compare the morphology of the gas and dust in the protostellar envelopes. The spatial concentration of HCO+ J=4-3 and 850 micron dust emission are used to classify the embedded nature of YSOs. Results. Approximately 30% of Class 0+I sources in Perseus and Taurus are not Stage I, but are likely to be more evolved Stage II pre-main sequence (PMS) stars with disks. An additional 16% are confused sources with an uncertain evolutionary stage. Conclusions. Separating classifications by cloud reveals that a high percentage of the Class 0+I sources in the Perseus star forming region are truly embedded Stage I sources (71%), while the Taurus cloud hosts a majority of evolved PMS stars with disks (68%). The concentration factor method is useful to correct misidentified embedded YSOs, yielding higher accuracy for YSO population statistics and Stage timescales. Current estimates (0.54 Myr) may overpredict the Stage I lifetime on the order of 30%, resulting in timescales of 0.38 Myr for the embedded phase.Comment: 33 pages, 21 figures, 6 tables, Accepted to be published in A&

    Rotational velocities of the giants in symbiotic stars: III. Evidence of fast rotation in S-type symbiotics

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    We have measured the projected rotational velocities (vsini) in a number of symbiotic stars and M giants using high resolution spectroscopic observations. On the basis of our measurements and data from the literature, we compare the rotation of mass-donors in symbiotics with vsini of field giants and find that: (1) the K giants in S-type symbiotics rotate at vsini>4.5 km/s, which is 2-4 times faster than the field K giants; (2) the M giants in S-type symbiotics rotate on average 1.5 times faster than the field M giants. Statistical tests show that these differences are highly significant: p-value < 0.001 in the spectral type bins K2III-K5III, M0III-M6III, and M2III-M5III; (3) our new observations of D'-type symbiotics also confirm that they are fast rotators. As a result of the rapid rotation, the cool giants in symbiotics should have 3-30 times larger mass loss rates. Our results suggest also that bipolar ejections in symbiotics seem to happen in objects where the mass donors rotate faster than the orbital period. All spectra used in our series of papers can be obtained upon request from the authors.Comment: MNRAS (accepted), 7 pages, 5 figure

    Synthetic Mudscapes: Human Interventions in Deltaic Land Building

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    In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are denied by traditional inhabitation. Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The social, economic, and ecological evolution of the region are defended by an expanded web of growing land

    Seasonal patterns of oral antihistamine and intranasal corticosteroid purchases from Australian community pharmacies : a retrospective observational study

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    Acknowledgments The abstract of this paper was presented at the Respiratory Effectiveness Group 2016 Annual Summit as a poster presentation with interim findings. The poster’s abstract was published in “Poster Abstracts” in The Journal of Thoracic Disease (Vol. 8, Supplement 5, 5 July 2016). http://jtd.amegroups.com/article/view/8504.Peer reviewedPublisher PD

    Stars of extragalactic origin in the solar neighborhood

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    We computed the spatial velocities and the galactic orbital elements using Hipparcos data for 77 nearest main-sequence F-G-stars with published the iron, magnesium, and europium abundances determined from high dispersion spectra and with the ages estimated from theoretical isochrones. A comparison with the orbital elements of the globular clusters that are known was accreted by our Galaxy in the past reveals stars of extragalactic origin. We show that the relative elemental abundance ratios of r- and \alpha- elements in all the accreted stars differ sharply from those in the stars that are genetically associated with the Galaxy. According to current theoretical models, europium is produced mainly in low mass Type II supernovae (SNe II), while magnesium is synthesized in larger amounts in high mass SN II progenitors. Since all the old accreted stars of our sample exhibit a significant Eu overabundance relative to Mg, we conclude that the maximum masses of the SNII progenitors outside the Galaxy were much lower than those inside it are. On the other hand, only a small number of young accreted stars exhibit low negative ratios [Eu/Mg]<0[Eu/Mg] < 0. The delay of primordial star formation burst and the explosions of high mass SNe II in a relatively small part of extragalactic space can explain this situation. We provide evidence that the interstellar medium was weakly mixed at the early evolutionary stages of the Galaxy formed from a single proto-galactic cloud and that the maximum mass of the SN II progenitors increased in it with time simultaneously with the increase in mean metallicity.Comment: Accepted for 2004, Astronomy Letters, Vol. 30, No. 3, P.148-158 15 pages, 3 figure

    Fermion zero modes at the boundary of superfluid 3He-B

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    Superfluid 3He-B belongs to the important special class of time-reversal invariant topological superfluids. It has Majorana fermions as edge states on the surface of bulk 3He-B. On the rough wall these fermion zero modes have finite density of states at E=0. It is possible that Lancaster experiments with a wire vibrating in 3He-B have already probed Majorana fermions living on the surface of the wire.Comment: 4 pages, no Figures, JETP Letters style, version to be published in JETP Letter

    Network meta-analysis of randomised trials of pharmacological, psychotherapeutic, exercise and collaborative care interventions for depressive symptoms in patients with coronary artery disease: Hybrid systematic review of systematic reviews protocol

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    This is the author accepted manuscriptBackground: Depression is common in patients with coronary artery disease (CAD) and is associated with poorer outcomes and higher costs. Several randomised controlled trials (RCTs) targeting depression, of various modalities (including pharmacological, psychotherapeutic and other approaches), have been conducted and summarised in pairwise meta-analytic reviews. However, no study has considered the cumulative evidence within a network, which can provide valuable indirect comparisons and information about the relative efficacy of interventions. Therefore, we will adopt a review of review methodology to develop a network meta-analysis (NMA) of depression interventions for depression in CAD. Methods: We will search relevant databases from inception for systematic reviews of RCTs of depression treatments for people with CAD, supplementing this with comprehensive searches for recent or ongoing studies. We will extract data from and summarise characteristics of individual RCTs, including participants, study characteristics, outcome measures and adverse events. Cochrane risk of bias ratings will also be extracted or if not present will be conducted by the authors. RCTs that compare depression treatments (grouped as pharmacological, psychotherapeutic, combined pharmacological/psychotherapeutic, exercise, collaborative care) to placebo, usual care, waitlist control or attention controls, or directly in head-to-head comparisons, will be included. Primary outcomes will be the change in depressive symptoms (summarised with a standardised mean difference) and treatment acceptability (treatment discontinuation: % of people who withdrew). Secondary outcomes will include change in 6-month depression outcomes, health-related quality of life (HRQoL), mortality, cardiovascular morbidity, health services use and adverse events. Secondary analyses will form further networks with individual anti-depressants and psychotherapies. We will use frequentist, random effects multivariate network meta-analysis to synthesise the evidence for depression intervention and to achieve a ranking of treatments, using Stata. Rankograms and surface under the cumulative ranking curves will be used for treatment ranking. Local and global methods will evaluate consistency. GRADE will be used to assess evidence quality for primary outcomes. Discussion: The present review will address uncertainties about the evidence in terms of depression management in CAD and may allow for a ranking of treatments, including providing important information for future research efforts

    Communications Biophysics

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    Contains reports on four research projects.National Institutes of Health (Grant 5 PO1 GM14940-05)National Aeronautics and Space Administration (Grant NGL 22-009-304)National Institutes of Health (Grant 5 TO1 GM01555-05)Boston City Hospital Purchase Order 10656B-D Electrodyne Division, Becton Dickinson and Compan
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