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
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
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
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
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
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
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
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 ()
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
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
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
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
- …