1,066 research outputs found
Pilot-Scale Denitrification Bioreactors for Replicated Field Research
Carbon-based denitrification bioreactors are designed to intercept tile drainage and are a promising technology for reducing NO3- export to surface water. While these systems have been tested extensively in the laboratory, the ability to study in-field bioreactors under controlled conditions with statistical replicates has been limited. Nine pilot-scale bioreactors (5.79 x 1.05 x 1.07 m) were designed and installed for systematic field testing, allowing for variation in retention time, fill material, and influent water quality parameters. Each bioreactor is constructed from a concrete trench in-line with influent flow control, dosing port, flow diffusion, and effluent water level control. Sampling ports are installed at two points in each bioreactor for access to water samples or fill materials. A potassium bromide (KBr) tracer study was conducted and Morrill Dispersion Index (MDI) values averaged 2.8 ± 0.3, indicating plug flow characteristics. The average tracer residence time () was 2.3 ± 0.3 h, in close agreement with the estimated hydraulic retention time (HRT) value of 2.1 ± 0.3 h, which was calculated using a porosity value of 0.70. Hydraulic efficiency was good (λ = 0.78 ± 0.03) and there was no evidence of short circuiting (S = 0.73 ± 0.03). This system is expected to provide useful insight regarding design for improved field performance of denitrification bioreactors
Characterization of radiolytically generated degradation products in the strip section of a TRUEX flowsheet
This report presents a summary of the work performed to meet the FCRD level 2 milestone M3FT-13IN0302053, “Identification of TRUEX Strip Degradation.” The INL radiolysis test loop has been used to identify radiolytically generated degradation products in the strip section of the TRUEX flowsheet. These data were used to evaluate impact of the formation of radiolytic degradation products in the strip section upon the efficacy of the TRUEX flowsheet for the recovery of trivalent actinides and lanthanides from acidic solution. The nominal composition of the TRUEX solvent used in this study is 0.2 M CMPO and 1.4 M TBP dissolved in n-dodecane and the nominal composition of the TRUEX strip solution is 1.5 M lactic acid and 0.050 M diethylenetriaminepentaacetic acid. Gamma irradiation of a mixture of TRUEX process solvent and stripping solution in the test loop does not adversely impact flowsheet performance as measured by stripping americium ratios. The observed increase in americium stripping distribution ratios with increasing absorbed dose indicates the radiolytic production of organic soluble degradation compounds
Patient perspectives on delays in diagnosis and treatment of cancer: a qualitative analysis of free-text data
Background: Earlier cancer diagnosis is crucial in improving cancer survival. The International Cancer Benchmarking Partnership Module 4 (ICBP4) is a quantitative survey study that explores the reasons for delays in diagnosis and treatment of breast, colorectal, lung, and ovarian cancer. To further understand the associated diagnostic processes, it is also important to explore the patient perspectives expressed in the free-text comments. Aim: To use the free-text data provided by patients completing the ICBP4 survey to augment the understanding of patients’ perspectives of their diagnostic journey. Design and setting: Qualitative analysis of the free-text data collected in Wales between October 2013 and December 2014 as part of the ICBP4 survey. Newly-diagnosed patients with either breast, ovarian, colorectal, or lung cancer were identified from registry data and then invited by their GPs to participate in the survey. Method: A thematic framework was used to analyse the free-text comments provided at the end of the ICBP4 survey. Of the 905 patients who returned a questionnaire, 530 included comments. Results: The free-text data provided information about patients’ perspectives of the diagnostic journey. Analysis identified factors that acted as either barriers or facilitators at different stages of the diagnostic process. Some factors, such as screening, doctor–patient familiarity, and private treatment, acted as both barriers and facilitators depending on the context. Conclusion: Factors identified in this study help to explain how existing models of cancer diagnosis (for example, the Pathways to Treatment Model) work in practice. It is important that clinicians are aware of how these factors may interact with individual clinical cases and either facilitate, or act as a barrier to, subsequent cancer diagnosis. Understanding and implementing this knowledge into clinical practice may result in quicker cancer diagnoses
Resolved Spectroscopy of Gravitationally-Lensed Galaxies: Recovering Coherent Velocity Fields in Sub-Luminous z~2-3 Galaxies
We present spatially-resolved dynamics for six strongly lensed star-forming
galaxies at z=1.7-3.1, each enlarged by a linear magnification factor ~8. Using
the Keck laser guide star AO system and the OSIRIS integral field unit
spectrograph we resolve kinematic and morphological detail in our sample with
an unprecedented fidelity, in some cases achieving spatial resolutions of ~100
pc. With one exception our sources have diameters ranging from 1-7 kpc, star
formation rates of 2-40 Msun/yr (uncorrected for extinction) and dynamical
masses of 10^(9.7-10.3) Msun. With this exquisite resolution we find that four
of the six galaxies display coherent velocity fields consistent with a simple
rotating disk model, which can only be recovered with the considerably improved
spatial resolution and sampling from the combination of adaptive optics and
strong gravitational lensing. Our model fits imply ratios for the systemic to
random motion, V sin(i)/sigma, ranging from 0.5-1.3 and Toomre disk parameters
Q<1. The large fraction of well-ordered velocity fields in our sample is
consistent with data analyzed for larger, more luminous sources at this
redshift. Our high resolution data further reveal that all six galaxies contain
multiple giant star-forming HII regions whose resolved diameters are in the
range 300 pc - 1.0 kpc, consistent with the Jeans length expected in the case
of dispersion support. The density of star formation in these regions is ~100
times higher than observed in local spirals; such high values are only seen in
the most luminous local starbursts. The global dynamics and demographics of
star formation in these HII regions suggest that vigorous star formation is
primarily governed by gravitational instability in primitive rotating disks.Comment: 18 pages, 8 figures, submitted to MNRA
Nebular and global properties of the gravitationally lensed galaxy "the 8 o'clock arc"
We present the analysis of new NIR, intermediate-resolution spectra of the
gravitationally lensed galaxy "the 8 o'clock arc" at z_sys = 2.7350 obtained
with VLT/X-shooter. These rest-frame optical data, combined with HST and
Spitzer images, provide very valuable information, which nicely complement our
previous detailed rest-frame UV spectral analysis. From high-resolution HST
images, we reconstruct the morphology of the arc in the source plane, and
identify that the source is formed of two majors parts, the main galaxy
component and a smaller blob separated by 1.2 kpc in projected distance. The
blob, with a twice larger magnification factor, is resolved in the spectra. The
multi-Gaussian fitting of detected nebular emission lines and the spectral
energy distribution modeling of the available multi-wavelength photometry
provide the census of gaseous and stellar dust extinctions, gas-phase
metallicities, star-formation rates (SFRs), and stellar, gas, and dynamical
masses for both the main galaxy and the blob. As a result, the 8 o'clock arc
shows a marginal trend for a more attenuated ionized gas than stars, and
supports a dependence of the dust properties on the SFR. With a high specific
star-formation rate, SSFR = 33+/-19 Gyr^{-1}, this lensed Lyman-break galaxy
deviates from the mass-SFR relation, and is characterized by a young age of
40^{+25}_{-20} Myr and a high gas fraction of about 72%. The 8 o'clock arc
satisfies the fundamental mass, SFR, and metallicity relation, and favors that
it holds up beyond z~2.5. We believe that the blob, with a gas mass M_gas =
(2.2+/-0.9)x10^{9} Msun (one order of magnitude lower than the mass of the
galaxy), a half-light radius r1/2 = 0.53+/-0.05 kpc, a star-formation rate
SFR_Halpha = 33+/-19 Msun yr^{-1}, and in rotation around the main core of the
galaxy, is one of these star-forming clumps commonly observed in z>1
star-forming galaxies. (Abridged)Comment: 15 pages, 5 figures, published in Astronomy and Astrophysic
Evolutionary consequences of fishing and their implications for salmon
We review the evidence for fisheries-induced evolution in anadromous salmonids. Salmon are exposed to a variety of fishing gears and intensities as immature or maturing individuals. We evaluate the evidence that fishing is causing evolutionary changes to traits including body size, migration timing and age of maturation, and we discuss the implications for fisheries and conservation. Few studies have fully evaluated the ingredients of fisheries-induced evolution: selection intensity, genetic variability, correlation among traits under selection, and response to selection. Most studies are limited in their ability to separate genetic responses from phenotypic plasticity, and environmental change complicates interpretation. However, strong evidence for selection intensity and for genetic variability in salmon fitness traits indicates that fishing can cause detectable evolution within ten or fewer generations. Evolutionary issues are therefore meaningful considerations in salmon fishery management. Evolutionary biologists have rarely been involved in the development of salmon fishing policy, yet evolutionary biology is relevant to the long-term success of fisheries. Future management might consider fishing policy to (i) allow experimental testing of evolutionary responses to exploitation and (ii) improve the long-term sustainability of the fishery by mitigating unfavorable evolutionary responses to fishing. We provide suggestions for how this might be done
A Two Micron All-Sky Survey View of the Sagittarius Dwarf Galaxy: II. Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream
We present moderate resolution (~6 km/s) spectroscopy of 284 M giant
candidates selected from the Two Micron All Sky Survey photometry. Radial
velocities (RVs) are presented for stars mainly in the south, with a number
having positions consistent with association to the trailing tidal tail of the
Sagittarius (Sgr) dwarf galaxy. The latter show a clear RV trend with orbital
longitude, as expected from models of the orbit and destruction of Sgr. A
minimum 8 kpc width of the trailing stream about the Sgr orbital midplane is
implied by verified RV members. The coldness of this stream (dispersion ~10
km/s) provides upper limits on the combined contributions of stream heating by
a lumpy Galactic halo and the intrinsic dispersion of released stars, which is
a function of the Sgr core mass. The Sgr trailing arm is consistent with a
Galactic halo containing one dominant, LMC-like lump, however some lumpier
halos are not ruled out. An upper limit to the total M/L of the Sgr core is 21
in solar units. A second structure that roughly mimics expectations for
wrapped, leading Sgr arm debris crosses the trailing arm in the Southern
Hemisphere; however, this may also be an unrelated tidal feature. Among the <13
kpc M giants toward the South Galactic Pole are some with large RVs that
identify them as halo stars, perhaps part of the Sgr leading arm near the Sun.
The positions and RVs of Southern Hemisphere M giants are compared with those
of southern globular clusters potentially stripped from the Sgr system and
support for association of Pal 2 and Pal 12 with Sgr debris is found. Our
discussion includes description of a masked-filtered cross-correlation
methodology that achieves better than 1/20 of a resolution element RVs in
moderate resolution spectra.Comment: 41 pages, 6 figures, Astronomical Journal, in press (submitted Nov.
24, 2003; tentatively scheduled for July 2004 issue
Does wage rank affect employees' well-being?
How do workers make wage comparisons? Both an experimental study and an analysis of 16,000 British employees are reported. Satisfaction and well-being levels are shown to depend on more than simple relative pay. They depend upon the ordinal rank of an individual's wage within a comparison group. “Rank” itself thus seems to matter to human beings. Moreover, consistent with psychological theory, quits in a workplace are correlated with pay distribution skewness
A jump-growth model for predator-prey dynamics: derivation and application to marine ecosystems
This paper investigates the dynamics of biomass in a marine ecosystem. A
stochastic process is defined in which organisms undergo jumps in body size as
they catch and eat smaller organisms. Using a systematic expansion of the
master equation, we derive a deterministic equation for the macroscopic
dynamics, which we call the deterministic jump-growth equation, and a linear
Fokker-Planck equation for the stochastic fluctuations. The McKendrick--von
Foerster equation, used in previous studies, is shown to be a first-order
approximation, appropriate in equilibrium systems where predators are much
larger than their prey. The model has a power-law steady state consistent with
the approximate constancy of mass density in logarithmic intervals of body mass
often observed in marine ecosystems. The behaviours of the stochastic process,
the deterministic jump-growth equation and the McKendrick--von Foerster
equation are compared using numerical methods. The numerical analysis shows two
classes of attractors: steady states and travelling waves.Comment: 27 pages, 4 figures. Final version as published. Only minor change
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