1,786 research outputs found
Evidence of traffic-related pollutant control in soil-based Sustainable Urban Drainage Systems (SUDS)
SUDS are being increasingly employed to control highway runoff and have the potential to protect groundwater and surface water quality by minimising the risks of both point and diffuse sources of pollution. While these systems are effective at retaining polluted solids by filtration and sedimentation processes, less is known of the detail of pollutant behaviour within SUDS structures. This paper reports on investigations carried out as part of a co-ordinated programme of controlled studies and field measurements at soft-engineered SUDS undertaken in the UK, observing the accumulation and behaviour of traffic-related heavy metals, oil and PAHs. The field data presented were collected from two extended detention basins serving the M74 motorway in the south-west of Scotland. Additional data were supplied from an experimental lysimeter soil core leaching study. Results show that basin design influences pollutant accumulation and behaviour in the basins. Management and/or control strategies are discussed for reducing the impact of traffic-related pollutants on the aqueous environment
Morphological optimization for access to dual oxidants in biofilms
A major theme driving research in biology is the relationship
between form and function. In particular, a longstanding goal has
been to understand how the evolution of multicellularity conferred
fitness advantages. Here we show that biofilms of the bacterium
Pseudomonas aeruginosa produce structures that maximize cellular
reproduction. Specifically, we develop a mathematical model of resource
availability and metabolic response within colony features.
This analysis accurately predicts the measured distribution of two
types of electron acceptors: oxygen, which is available from the
atmosphere, and phenazines, redox-active antibiotics produced by
the bacterium. Using this model, we demonstrate that the geometry
of colony structures is optimal with respect to growth efficiency.
Because our model is based on resource dynamics, we also can anticipate
shifts in feature geometry based on changes to the availability
of electron acceptors, including variations in the external
availability of oxygen and genetic manipulation that renders the
cells incapable of phenazine production
Method of Mutation Analysis May Contribute to Discrepancies in Reports of V599EBRAF Mutation Frequencies in Melanocytic Neoplasms
WFPC2 Observations of the Cooling Flow Elliptical in Abell 1795
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 H
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 R 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 M\solar\ and is more likely to be 6.5 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
Hubble Space Telescope Observations of the Draco Dwarf Spheroidal
We present an F606W-F814W color-magnitude diagram for the Draco dwarf
spheroidal galaxy based on Hubble Space Telescope WFPC2 images. The luminosity
function is well-sampled to 3 magnitudes below the turn-off. We see no evidence
for multiple turnoffs and conclude that, at least over the field of the view of
the WFPC2, star formation was primarily single-epoch. If the observed number of
blue stragglers is due to extended star formation, then roughly 6% (upper
limit) of the stars could be half as old as the bulk of the galaxy. The color
difference between the red giant branch and the turnoff is consistent with an
old population and is very similar to that observed in the old, metal-poor
Galactic globular clusters M68 and M92. Despite its red horizontal branch,
Draco appears to be older than M68 and M92 by 1.6 +/- 2.5 Gyrs, lending support
to the argument that the ``second parameter'' which governs horizontal branch
morphology must be something other than age. Draco's observed luminosity
function is very similar to that of M68, and the derived initial mass function
is consistent with that of the solar neighborhood.Comment: 16 pages, AASTeX, 9 postscript figures, figures 1 and 2 available at
ftp://bb3.jpl.nasa.gov/pub/draco/. Accepted for publication in the
Astronomical Journa
Restriction endonuclease TseI cleaves A:A and T:T mismatches in CAG and CTG repeats.
The type II restriction endonuclease TseI recognizes the DNA target sequence 5'-G^CWGC-3' (where W = A or T) and cleaves after the first G to produce fragments with three-base 5'-overhangs. We have determined that it is a dimeric protein capable of cleaving not only its target sequence but also one containing A:A or T:T mismatches at the central base pair in the target sequence. The cleavage of targets containing these mismatches is as efficient as cleavage of the correct target sequence containing a central A:T base pair. The cleavage mechanism does not apparently use a base flipping mechanism as found for some other type II restriction endonuclease recognizing similarly degenerate target sequences. The ability of TseI to cleave targets with mismatches means that it can cleave the unusual DNA hairpin structures containing A:A or T:T mismatches formed by the repetitive DNA sequences associated with Huntington's disease (CAG repeats) and myotonic dystrophy type 1 (CTG repeats)
Observations and Implications of the Star Formation History of the LMC
We present derivations of star formation histories based on color-magnitude
diagrams of three fields in the LMC from HST/WFPC2 observations. A significant
component of stars older than 4 Gyr is required to match the observed
color-magnitude diagrams. Models with a dispersion-free age-metallicity
relation are unable to reproduce the width of the observed main sequence;
models with a range of metallicity at a given age provide a much better fit.
Such models allow us to construct complete ``population boxes'' for the LMC
based entirely on color-magnitude diagrams; remarkably, these qualitatively
reproduce the age-metallicity relation observed in LMC clusters. We discuss
some of the uncertainties in deriving star formation histories. We find,
independently of the models, that the LMC bar field has a larger relative
component of older stars than the outer fields. The main implications suggested
by this study are: 1) the star formation history of field stars appears to
differ from the age distribution of clusters, 2) there is no obvious evidence
for bursty star formation, but our ability to measure bursts shorter in
duration than 25% of any given age is limited by the statistics of the
observed number of stars, 3) there may be some correlation of the star
formation rate with the last close passage of the LMC/SMC/Milky Way, but there
is no dramatic effect, and 4) the derived star formation history is probably
consistent with observed abundances, based on recent chemical evolution models.Comment: Accepted by AJ, 36 pages including 12 figure
Addition of abiraterone to first-line long-term hormone therapy in prostate cancer (STAMPEDE): Model to estimate long-term survival, quality-adjusted survival, and cost-effectiveness
Background: Results from randomised trials show adding abiraterone acetate plus prednisolone (AAP) to standard of care (SOC) improves disease-free and overall survival in men with prostate cancer (PC) starting long-term hormone therapy for first time. Formal assessment is required of whether funding AAP here shows appropriate use of resources. This cost-effectiveness decision model tests if giving AAP to these patients is cost-effective using costs from English National Health Service, the largest nation where STAMPEDE recruited. / Methods: Health outcomes and costs were modelled using patient data from AAP comparison of STAMPEDE (recruitment 2011-14). This included 1917 men with high-risk, locally advanced metastatic or recurrent PC starting 1st-line hormone therapy. SOC was hormone therapy for â„2 years with radiotherapy in pre-selected patients. If allocated to research group, AAP (AA 1000mg/day, P 5mg/day) was added to SOC. The model makes lifetime predictions of survival, costs and quality-adjusted lifeyears (QALYs), with costs and QALYs discounted at 3.5% annually. Sensitivity analyses were performed. / Results: The model predicted AAP would extend survival (discounted quality-adjusted survival) by 2.68y (1.46 QALYs) for metastatic patients and 0.30y (0.29 QALYs) for non-metastatic. The cost of AAP means it is not currently cost-effective in this setting, including with Patient Access Scheme costs for AAP and enzalutamide and similar reductions for cabazitaxel and Ra. If AAPâs price reduces after patent expiry as expected (90% reduction on BNF cost), it would be cost-effective in both patient groups, with incremental cost-effectiveness ratios below ÂŁ10,000 (US$12,665) per QALY. AAP could also dominate in non-metastatic patients (i.e. lower costs and higher QALYs than SOC alone). / Conclusions: AAP could be cost-effective for patients with non-metastatic and metastatic disease with expected future pricing and may be cost-saving in the former. Policymakers should encourage license submissions and generic price reductions to facilitate use of AAP given cost-saving potential in addition to improving survival. / Clinical trial information: NCT00268476
Identifying spatial variability and complexity in wetland vegetation using an object-based approach
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