626 research outputs found
Arsenic in the Water, Soil Bedrock, and Plants of the Ester Dome Area of Alaska
Concentrations of arsenic as large as 10 ppm (200 times the safe
limit for drinking water) occur in the groundwater of a mineralized
residential area near Fairbanks. Bedrock of the area contains 750 ppm
As, primarily as arsenopyrite and scorodite. The oxygen-poor groundwater
is enriched in As(III) and ferrous iron while the surface waters
are iron free and contain less than 50 ppb As(V). Arsenic is removed
from the water by coprecipitation with ferric hydroxide. Some iron-rich
stream sediments contain as much as 1,400 ppm arsenic.
The distribution of arsenic in the groundwater is controlled by the
distribution of arsenic in the bedrock. The arsenic content of the B soil
horizon over mineralized veins is about 150 ppm, while that over barren
rock is 30 ppm. The vegetation over the veins is not significantly
enriched in arsenic.
Lettuce, radishes and tomatoes grown with arsenic-rich water (5 ppm) contain 16, 8 and 1 ppm As, respectively; these amounts are significantly
greater than plants not treated with arsenic.
Preliminary studies by state and federal health agencies show no
detrimental effects on the health of persons drinking these arsenic-rich
waters.The work upon which this publication is based was supported in part by
funds provided by the Office of Water Research and Technology (Project
B-037-ALAS, Agreement No. 14-34-0001-8056), U.S. Department of the
Interior, Washington, D.C., as authorized by the Water Research and
Development Act of 1978
Damp Mergers: Recent Gaseous Mergers without Significant Globular Cluster Formation?
Here we test the idea that new globular clusters (GCs) are formed in the same
gaseous ("wet") mergers or interactions that give rise to the young stellar
populations seen in the central regions of many early-type galaxies. We compare
mean GC colors with the age of the central galaxy starburst. The red GC
subpopulation reveals remarkably constant mean colors independent of galaxy
age. A scenario in which the red GC subpopulation is a combination of old and
new GCs (formed in the same event as the central galaxy starburst) can not be
ruled out; although this would require an age-metallicity relation for the
newly formed GCs that is steeper than the Galactic relation. However, the data
are also well described by a scenario in which most red GCs are old, and few,
if any, are formed in recent gaseous mergers. This is consistent with the old
ages inferred from some spectroscopic studies of GCs in external systems. The
event that induced the central galaxy starburst may have therefore involved
insufficient gas mass for significant GC formation. We term such gas-poor
events "damp" mergers.Comment: 17 pages, 5 figures, ApJ accepte
Impact of the Holocene Transgression on the Atlantic Coastline of Nova Scotia
As analogs for impact of a future sea-level rise on the coast of Nova Scotia (eastern Canada), geological data and information on relative sea-level changes are examined at three different time scales. Relative sea level rose swiftly during the early Holocene, at a maximum rate of 11 m/ka at 7500 radiocarbon years BP. Freshwater, salt-marsh, and estuarine sediments that formed during this period have been located on the inner shelf. After 5000 BP the rate slackened to about 2 m/ka. Despite overall submergence and coastal retreat since that time, gravel barriers have persisted where large amounts of sediment have been added to the littoral system by erosion of glacial deposits. The barriers often display evidence of early progradational phases in the form of gravel beach ridges, partly or wholly submerged in lagoons behind contemporary storm beaches. Tide-gauge data from the past century show submergence rates averaging 3.5 mm/a, well in excess of the longterm trend. The response of the coastline to this rapid rise is complex. Unconsolidated cliffs (bluffs) retreat at up to 5 m/a during initial exposure to wave attack and during extreme storm events, but at lesser rates (8 m/a) in some locations, but low elsewhere, in some cases showing almost no movement over the past 10 years, and neighbouring beaches are sometimes observed to behave in completely different ways. Sediment released by coastal erosion finds its way into nearby estuaries, causing growth of flood-tidal deltas and marsh aggradation. If a global rise in sea level occurs, the processes of erosion and sedimentation operating along the coast of Nova Scotia during the Holocene are expected to continue in a similar fashion, but rates of change will increase at many locations.Les données géologiques et les connaissances sur les changements du niveau marin relatif sont étudiées à trois échelles temporelles en tant qu'analogues des conséquences d'une future hausse du niveau marin sur la côte de la Nouvelle-Écosse. Le niveau marin relatif s'est rapidement élevé au cours de l'Holocène inférieur, jusqu'au taux maximal de 11 m/ka à 7500 BP. Des sédiments estuariens ou issus de marais salants et d'eau douce datant de cette période ont été localisés sur le plateau continental intérieur. Après 5000 BP le taux a diminué jusqu'à 2 m/ka. En dépit de la submersion de la région côtière et de son dégagement subséquent, les cordons littoraux de gravier ont persisté là où de grandes quantités de sédiments ont été mis en place sur le littoral par érosion des dépôts glaciaires. Les cordons montrent souvent des indices de phases de progression sous la forme de crêtes de graviers, partiellement ou entièrement submergés dans les lagunes situées derrière les plages de tempêtes contemporaines. Les données marégraphiques du siècle dernier font ressortir un taux de submersion d'environ 3,5 mm/a, taux nettement plus élevé que celui de la tendance à long terme. La réponse du littoral à cette hausse rapide est complexe. Les falaises non consolidées peuvent reculer jusqu'à 5 m/a au début de leur exposition aux fortes vagues et pendant les plus fortes tempêtes et à un rythme beaucoup plus lent (8 m/a) par endroits, lent ailleurs; certaines plages sont presque immobiles depuis 10 ans, alors que les plages voisines se comportent de façon tout à fait différente. Les sédiments libérés par l'érosion littorale se retrouvent dans les estuaires les plus proches, provoquant l'expansion des deltas d'inondation et l'extension des marais. Si une hausse globale du niveau marin survenait, les processus d'érosion et de sédimentation qui se sont manifestés le long de la côte de la Nouvelle-Écosse pendant l'Holocène agiront de façon semblable, mais le rythme des changements augmentera dans plusieurs sites
The spatial distribution of esophageal and gastric cancer in Caspian region of Iran: An ecological analysis of diet and socio-economic influences
Recent studies have suggested a systematic geographic pattern of esophageal cancer (EC) and gastric cancer (GC) incidence in the Caspian region of Iran. The aims of this study were to investigate the association between these cancers and the region's dietary and socioeconomic risk factors and to map EC and GC after adjustment for the risk factors and the removal of random and geographic variations from area specific age standardised incidence ratios (SIRs)
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Moyal star product approach to the Bohr-Sommerfeld approximation
The Bohr-Sommerfeld approximation to the eigenvalues of a one-dimensional
quantum Hamiltonian is derived through order (i.e., including the
first correction term beyond the usual result) by means of the Moyal star
product. The Hamiltonian need only have a Weyl transform (or symbol) that is a
power series in , starting with , with a generic fixed point in
phase space. The Hamiltonian is not restricted to the kinetic-plus-potential
form. The method involves transforming the Hamiltonian to a normal form, in
which it becomes a function of the harmonic oscillator Hamiltonian.
Diagrammatic and other techniques with potential applications to other normal
form problems are presented for manipulating higher order terms in the Moyal
series.Comment: 27 pages, no figure
The early-type galaxies NGC 1407 and NGC 1400 - II: star formation and chemical evolutionary history
We present a possible star formation and chemical evolutionary history for
two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest
galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as
part of the Group Evolution Multi-wavelength Study (GEMS). Our analysis is
based on new high signal-to-noise spatially resolved integrated spectra
obtained at the ESO 3.6m telescope, out to 0.6 (NGC 1407) and 1.3 (NGC 1400)
effective radii. Using Lick/IDS indices we estimate luminosity-weighted ages,
metallicities and -element abundance ratios. Colour radial
distributions from HST/ACS and Subaru Suprime-Cam multi-band wide-field imaging
are compared to colours predicted from spectroscopically determinated ages and
metallicities using single stellar population models. The galaxies formed over
half of their mass in a single short-lived burst of star formation (> 100
M(sun)/year) at redshift z>5. This likely involved an outside-in mechanism with
supernova-driven galactic winds, as suggested by the flatness of the
alpha-element radial profiles and the strong negative metallicity gradients.
Our results support the predictions of the revised version of the monolithic
collapse model for galaxy formation and evolution. We speculate that, since
formation the galaxies have evolved quiescently and that we are witnessing the
first infall of NGC 1400 in the group.Comment: 14 pages, 9 tables, 6 figures, Accepted for publication in MNRA
The early-type galaxies NGC 1407 and NGC 1400 - I: spatially resolved radial kinematics and surface photometry
This is the first paper of a series focused on investigating the star
formation and evolutionary history of the two early-type galaxies NGC 1407 and
NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A)
group, one of the 60 groups studied as part of the Group Evolution
Multi-wavelength Study (GEMS). Here we present new high signal-to-noise
long-slit spectroscopic data obtained at the ESO 3.6m telescope and
high-resolution multi-band imaging data from the HST/ACS and wide-field imaging
from Subaru Suprime-Cam. We spatially resolved integrated spectra out to 0.6
(NGC 1407) and 1.3 (NGC 1400) effective radii. The radial profiles of the
kinematic parameters v(rot), sigma, h3 and h4 are measured. The surface
brightness profiles are fitted to different galaxy light models and the colour
distributions analysed. The multi-band images are modelled to derive isophotal
shape parameters and residual galaxy images. The parameters from the surface
brightness profile fitting are used to estimate the mass of the possible
central supermassive black hole in NGC 1407. The galaxies are found to be
rotationally supported and to have a flat core in the surface brightness
profiles. Elliptical isophotes are observed at all radii and no fine structures
are detected in the residual galaxy images. From our results we can also
discard a possible interaction between NGC 1400, NGC 1407 and the group
intergalactic medium. We estimate a mass of 1.03x10^9 M(sun) for the
supermassive black hole in NGC 1407 galaxy.Comment: 11 pages, 6 tables, 6 figures, Accepted for publication in MNRA
Physician decision making in selection of second-line treatments in immune thrombocytopenia in children.
Immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder which presents with isolated thrombocytopenia and risk of hemorrhage. While most children with ITP promptly recover with or without drug therapy, ITP is persistent or chronic in others. When needed, how to select second-line therapies is not clear. ICON1, conducted within the Pediatric ITP Consortium of North America (ICON), is a prospective, observational, longitudinal cohort study of 120 children from 21 centers starting second-line treatments for ITP which examined treatment decisions. Treating physicians reported reasons for selecting therapies, ranking the top three. In a propensity weighted model, the most important factors were patient/parental preference (53%) and treatment-related factors: side effect profile (58%), long-term toxicity (54%), ease of administration (46%), possibility of remission (45%), and perceived efficacy (30%). Physician, health system, and clinical factors rarely influenced decision-making. Patient/parent preferences were selected as reasons more often in chronic ITP (85.7%) than in newly diagnosed (0%) or persistent ITP (14.3%, P = .003). Splenectomy and rituximab were chosen for the possibility of inducing long-term remission (P < .001). Oral agents, such as eltrombopag and immunosuppressants, were chosen for ease of administration and expected adherence (P < .001). Physicians chose rituximab in patients with lower expected adherence (P = .017). Treatment choice showed some physician and treatment center bias. This study illustrates the complexity and many factors involved in decision-making in selecting second-line ITP treatments, given the absence of comparative trials. It highlights shared decision-making and the need for well-conducted, comparative effectiveness studies to allow for informed discussion between patients and clinicians
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