215 research outputs found

    The nature-printed British sea-weeds : a history, accompanied by figures and dissections, of the algae of the British Isles ; in four volumes

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    1. Rhodospermeae: fam. I. - IX. 2. Rhodospermeae: fam. X. - XIII. 3. Melanospermeae 4. Chlorospermea

    XMM-Newton and Chandra Observations of the Galaxy Group NGC 5044. I. Evidence for Limited Multi-Phase Hot Gas

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    Using new XMM and Chandra observations we present an analysis of the temperature structure of the hot gas within a radius of 100 kpc of the bright nearby galaxy group NGC 5044. A spectral deprojection analysis of data extracted from circular annuli reveals that a two-temperature model (2T) of the hot gas is favored over single-phase or cooling flow (M_dot = 4.5 +/- 0.2 M_{sun}/yr) models within the central ~30 kpc. Alternatively, the data can be fit equally well if the temperature within each spherical shell varies continuously from ~T_h to T_c ~ T_h/2, but no lower. The high spatial resolution of the Chandra data allows us to determine that the temperature excursion T_h --> T_c required in each shell exceeds the temperature range between the boundaries of the same shell in the best-fitting single-phase model. This is strong evidence for a multi-phase gas having a limited temperature range. The cooler component of the 2T model has a temperature (T_c \~ 0.7 keV) similar to the kinetic temperature of the stars. The hot phase has a temperature (T_h ~ 1.4 keV) characteristic of the virial temperature of the \~10^{13} M_{sun} halo expected in the NGC 5044 group. However, in view of the morphological disturbances and X-ray holes visible in the Chandra image within R ~10 kpc, bubbles of gas heated to ~T_h in this region may be formed by intermittent AGN feedback. Some additional heating at larger radii may be associated with the evolution of the cold front near R ~50 kpc, as suggested by the sharp edge in the EPIC images.Comment: 18 pages, 10 figures, Accepted for publication in ApJ, some changes in presentation for consistency with paper 2 (astro-ph/0303054), includes detailed analysis of azimuthal spectral variations in the chandra image, conclusions unchanged from previous versio

    Conflict, compromise and collusion: dilemmas for psychosocially-oriented practitioners in the mental health system

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    The nature and causes of mental health problems are contested. The dominant approach in services views them as ‘illnesses like any other’. The structure, legislative base and practices of mainstream mental health services are largely predicated on this idea, known variously as the medical, illness, disease or diagnostic model. By contrast, psychosocial theories highlight the role of the events and circumstances of peoples’ lives. The tension between these two approaches can lead to challenges and dilemmas for psychosocially oriented practitioners. Clinical psychologists participated in interviews and a focus group about these challenges and how they managed them. A grounded theory was constructed which suggested that their responses took three forms: openly ‘dissenting’ (conflict), strategically ‘stepping into’ the medical model (compromise), or inadvertently ‘slipping’ into it (colluding). Strategies for managing the challenges included focusing on clients; foregrounding clients’ contexts and understandings; holding the tension between ‘expert’ and ‘not-knowing’ approaches; using ordinary language; forging robust working relationships; being mindful of difference and of constraints on colleagues; recognising one’s power and ability to influence; self-care and work/life balance; taking encouragement from small changes; consolidating a personal philosophy; mutual support and solidarity; drawing on scholarship and finally engaging in activism outside work

    Formation of Low Mass Stars in Elliptical Galaxy Cooling Flows

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    X-ray emission from hot (T = 10^7 K) interstellar gas in massive elliptical galaxies indicates that 10^{10} M_sun has cooled over a Hubble time, but optical and radio evidence for this cold gas is lacking. We provide detailed theoretical support for the hypothesis that this gas has formed into low luminosity stars. Within several kpc of the galactic center, interstellar gas first cools to T = 10^4 K where it is heated by stellar UV and emits the observed diffuse optical line emission. This cooling occurs at a large number (10^6) of isolated sites. After less than a solar mass of gas has accumulated (10^{-6} M_sun/yr) at a typical cooling site, a neutral (HI or H_2) core develops in the HII cloud where gas temperatures drop to T = 15 K and the ionization level (from thermal X-rays) is very low (x = 10^{-6}). We show that the maximum mass of cores that become gravitationally unstable is only about 2 M_sun. No star can exceed this mass. Fragmentation of collapsing cores produces a population of low mass stars with a bottom-heavy IMF and radial orbits. Gravitational collapse and ambipolar diffusion are rapid. The total mass of star-forming (dust-free) HI or H_2 cores in a typical bright elliptical is only 10^6 M_sun, below current observational thresholds.Comment: 23 pages in AASTEX LaTeX with 8 figures; accepted by Astrophysical Journa

    Centimeter to decimeter hollow concretions and voids in Gale Crater sediments, Mars

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    Voids and hollow spheroids between ∼1 and 23 cm in diameter occur at several locations along the traverse of the Curiosity rover in Gale crater, Mars. These hollow spherical features are significantly different from anything observed in previous landed missions. The voids appear in dark-toned, rough-textured outcrops, most notably at Point Lake (sols 302-305) and Twin Cairns Island (sol 343). Point Lake displays both voids and cemented spheroids in close proximity; other locations show one or the other form. The spheroids have 1-4 mm thick walls and appear relatively dark-toned in all cases, some with a reddish hue. Only one hollow spheroid (Winnipesaukee, sol 653) was analyzed for composition, appearing mafic (Fe-rich), in contrast to the relatively felsic host rock. The interior surface of the spheroid appears to have a similar composition to the exterior with the possible exceptions of being more hydrated and slightly depleted in Fe and K. Origins of the spheroids as Martian tektites or volcanic bombs appear unlikely due to their hollow and relatively fragile nature and the absence of in-place clearly igneous rocks. A more likely explanation to both the voids and the hollow spheroids is reaction of reduced iron with oxidizing groundwater followed by some re-precipitation as cemented rind concretions at a chemical reaction front. Although some terrestrial concretion analogs are produced from a precursor siderite or pyrite, diagenetic minerals could also be direct precipitates for other terrestrial concretions. The Gale sediments differ from terrestrial sandstones in their high initial iron content, perhaps facilitating a higher occurrence of such diagenetic reactions

    An Unbiased Survey of 500 Nearby Stars for Debris Disks: A JCMT Legacy Program

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    We present the scientific motivation and observing plan for an upcoming detection survey for debris disks using the James Clerk Maxwell Telescope. The SCUBA-2 Unbiased Nearby Stars (SUNS) Survey will observe 500 nearby main sequence and sub-giant stars (100 of each of the A, F, G, K and M spectral classes) to the 850 micron extragalactic confusion limit to search for evidence of submillimeter excess, an indication of circumstellar material. The survey distance boundaries are 8.6, 16.5, 22, 25 and 45 pc for M, K, G, F and A stars, respectively, and all targets lie between the declinations of -40 deg to 80 deg. In this survey, no star will be rejected based on its inherent properties: binarity, presence of planetary companions, spectral type or age. This will be the first unbiased survey for debris disks since IRAS. We expect to detect ~125 debris disks, including ~50 cold disks not detectable in current shorter wavelength surveys. A substantial amount of complementary data will be required to constrain the temperatures and masses of discovered disks. High resolution studies will likely be required to resolve many of the disks. Therefore, these systems will be the focus of future observational studies using a variety of observatories to characterize their physical properties. For non-detected systems, this survey will set constraints (upper limits) on the amount of circumstellar dust, of typically 200 times the Kuiper Belt mass, but as low as 10 times the Kuiper Belt mass for the nearest stars in the sample (approximately 2 pc).Comment: 11 pages, 7 figures (3 color), accepted by the Publications of the Astronomical Society of the Pacifi

    Status of Muon Collider Research and Development and Future Plans

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    The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay (πμνμ\pi \to \mu \nu_{\mu}) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beam

    The X-ray cavities, filaments and cold fronts in the core of the galaxy group NGC 5044

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    We present a two-dimensional analysis of the bright nearby galaxy group NGC 5044 using the currently available Chandra and XMM data. In the inner 10 kpc a pair of cavities are evident together with a set of bright X-ray filaments. If the cavities are interpreted as gas displaced by relativistic plasma inflated by an AGN, even in the absence of extended 1.4 GHz emission, this would be consistent with a recent outburst as also indicated by the extent of dust and H_alpha emission. The soft X-ray filaments coincident with H_alpha and dust emission are cooler than the ones which do not correlate with optical and infrared emission. We suggest that dust-aided cooling contributes to form warm (T =10^4 K) gas, emitting H_alpha radiation. At 31 kpc and 67 kpc a pair of cold fronts are present, indicative of sloshing due to a dynamical perturbation caused by accretion of a less massive group, also suggested by the peculiar velocity of the brightest galaxy NGC 5044 with respect to the mean group velocity.Comment: 12 pages, 11 colour figures, ApJ accepted. Expanded discussion, results unchange

    Assessment of an in silico mechanistic model for proarrhythmia risk prediction under the CiPA initiative

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    International Council on Harmonization S7B and E14 regulatory guidelines are sensitive but not specific for predicting which drugs are proarrhythmic. In response, the Comprehensive In Vitro Proarrhythmia Assay (CiPA) was proposed that integrates multi-ion channel pharmacology data in vitro into a human cardiomyocyte model in silico for proarrhythmia risk assessment. Previously, we reported the model optimization and proarrhythmia metric selection based on CiPA training drugs. In this study, we report the application of the prespecified model and metric to independent CiPA validation drugs. Over two validation datasets, the CiPA model performance meets all pre-specified measures for ranking and classifying validation drugs, and outperforms alternatives, despite some in vitro data differences between the two datasets due to different experimental conditions and quality control procedures This suggests that the current CiPA model/metric is fit for regulatory use, and standard experimental protocols and quality control criteria could increase the model prediction accuracy even further

    The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

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    The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure
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