2,047 research outputs found
Density-and trait-mediated effects of a parasite and a predator in a tri-trophic food web
1. Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long-term population dynamics of non-host species or about whether such effects are density- or trait- mediated.
2. We studied a tri-trophic food chain comprised of: (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium caudatum), (iii) a top predator (Didinium nasutum), and (iv) a parasite of the intermediate consumer (Holospora undulata). A fully-factorial experimental manipulation of predator and parasite presence/absence was combined with analyses of population dynamics, modelling, and analyses of host (Paramecium) morphology and behavior.
3. Predation and parasitism each reduced the abundance of the intermediate consumer (Paramecium), and parasitism indirectly reduced the abundance of the basal resource (Serratia). However, in combination, predation and parasitism had non-additive effects on the abundance of the intermediate consumer, as well as on that of the basal resource. In both cases, the negative effect of parasitism seemed to be effaced by predation.
4. Infection of the intermediate consumer reduced predator abundance. Modelling and additional experimentation revealed that this was most likely due to parasite reduction of intermediate host abundance (a density-mediated effect), as opposed to changes in predator functional or numerical response.
5. Parasitism altered morphological and behavioural traits, by reducing host cell length and increasing the swimming speed of cells with moderate parasite loads. Additional tests showed no significant difference in Didinium feeding rate on infected and uninfected hosts, suggesting that the combination of these modifications does not affect host vulnerability to predation. However, estimated rates of encounter with Serratia based on these modifications were higher for infected Paramecium than for uninfected Paramecium.
6. A mixture of density-mediated and trait-mediated indirect effects of parasitism on non- host species creates rich and complex possibilities for effects of parasites in food webs that should be included in assessments of possible impacts of parasite eradication or introduction
Evaluation of a small municipal constructed wetland wastewater treatment system
Modifications were made to an existing wastewater wetland treatment system to improve its effluent quality. Modifications included installation of baffles in the pond and the planting of selected plant materials. Removal efficiencies for BOD, ammonianitrogen, TSS and phosphate were monitored and shown to be influenced more by water temperature, loading rate and hydraulic retention time than presence of sparsely established vegetation. This study shows that the plant materials selected were inappropriate for use in wetland systems for wastewater treatment systems in mid-Missouri. Also, the presence of bottom sludge in the wetland system prevented the propagation of the selected plants.Project # G-1572-04 Agreement # 14-08-0001-G-1572-0
CIV emission-line properties and systematic trends in quasar black hole mass estimates
Black-hole masses are crucial to understanding the physics of the connection
between quasars and their host galaxies and measuring cosmic black hole-growth.
At high redshift, z > 2.1, black hole masses are normally derived using the
velocity-width of the CIV broad emission line, based on the assumption that the
observed velocity-widths arise from virial-induced motions. In many quasars,
the CIV-emission line exhibits significant blue asymmetries (`blueshifts') with
the line centroid displaced by up to thousands of km/s to the blue. These
blueshifts almost certainly signal the presence of strong outflows, most likely
originating in a disc wind. We have obtained near-infrared spectra, including
the H emission line, for 19 luminous ( = 46.5-47.5 erg/s)
Sloan Digital Sky Survey quasars, at redshifts 2 < z < 2.7, with CIV emission
lines spanning the full-range of blueshifts present in the population. A strong
correlation between CIV-velocity width and blueshift is found and, at large
blueshifts, > 2000 km/s, the velocity-widths appear to be dominated by
non-virial motions. Black-hole masses, based on the full width at half maximum
of the CIV-emission line, can be overestimated by a factor of five at large
blueshifts. A larger sample of quasar spectra with both CIV and H, or
H, emission lines will allow quantitative corrections to CIV-based
black-hole masses as a function of blueshift to be derived. We find that
quasars with large CIV blueshifts possess high Eddington luminosity ratios and
that the fraction of high-blueshift quasars in a flux-limited sample is
enhanced by a factor of approximately four relative to a sample limited by
black hole mass.Science and Technology Facilities CouncilThis is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw136
Wavelet Transform of Fractional Integrals for Integrable Boehmians
The present paper deals with the wavelet transform of fractional integral operator (the Riemann- Liouville operators) on Boehmian spaces. By virtue of the existing relation between the wavelet transform and the Fourier transform, we obtained integrable Boehmians defined on the Boehmian space for the wavelet transform of fractional integrals
Entanglement by linear SU(2) transformations: generation and evolution of quantum vortex states
We consider the evolution of a two-mode system of bosons under the action of
a Hamiltonian that generates linear SU(2) transformations. The Hamiltonian is
generic in that it represents a host of entanglement mechanisms, which can thus
be treated in a unified way. We start by solving the quantum dynamics
analytically when the system is initially in a Fock state. We show how the two
modes get entangled by evolution to produce a coherent superposition of vortex
states in general, and a single vortex state under certain conditions. The
degree of entanglement between the modes is measured by finding the explicit
analytical dependence of the Von Neumann entropy on the system parameters. The
reduced state of each mode is analyzed by means of its correlation function and
spatial coherence function. Remarkably, our analysis is shown to be equally as
valid for a variety of initial states that can be prepared from a two-mode Fock
state via a unitary transformation and for which the results can be obtained by
mere inspection of the corresponding results for an initial Fock state. As an
example, we consider a quantum vortex as the initial state and also find
conditions for its revival and charge conjugation. While studying the evolution
of the initial vortex state, we have encountered and explained an interesting
situation in which the entropy of the system does not evolve whereas its wave
function does. Although the modal concept has been used throughout the paper,
it is important to note that the theory is equally applicable for a
two-particle system in which each particle is represented by its bosonic
creation and annihilation operators.Comment: 6 figure
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Correcting C -Based Virial Black Hole Masses
The C λλ1498,1501 broad emission line is visible in optical spectra to redshifts exceeding ∼ 5. C has long been known to exhibit significant displacements to the blue and these ‘blueshifts’ almost certainly signal the presence of strong outflows. As a consequence, single-epoch virial black hole (BH) mass estimates derived from C velocity widths are known to be systematically biased compared to masses from the hydrogen Balmer lines. Using a large sample of 230 high-luminosity ( = 10–10 erg s), redshift 1.5 < < 4.0 quasars with both C and Balmer line spectra, we have quantified the bias in C BH masses as a function of the C blueshift. C BH masses are shown to be a factor of 5 larger than the corresponding Balmer-line masses at C blueshifts of 3000 km s and are overestimated by almost an order of magnitude at the most extreme blueshifts, ≳5000 km s. Using the monotonically increasing relationship between the C blueshift and the mass ratio BH(C )/BH(H), we derive an empirical correction to all C BH masses. The scatter between the corrected C masses and the Balmer masses is 0.24 dex at low C blueshifts (∼0 km s) and just 0.10 dex at high blueshifts (∼3000 km s), compared to 0.40 dex before the correction. The correction depends only on the C line properties – i.e. full width at half-maximum and blueshift – and can therefore be applied to all quasars where C emission line properties have been measured, enabling the derivation of unbiased virial BH-mass estimates for the majority of high-luminosity, high-redshift, spectroscopically confirmed quasars in the literature.LC thanks the Science and Technology Facilities Council (STFC) for the award of a studentship. PCH acknowledges support from the STFC via a Consolidated Grant to the Institute of Astronomy, Cambridge. MB acknowledges support from STFC via an Ernest Rutherford Fellowship.
Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS website is http://www.sdss.org/.
The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory and the University of Washington.
1iraf is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation
Simulations of the OzDES AGN Reverberation Mapping Project
As part of the OzDES spectroscopic survey we are carrying out a large scale
reverberation mapping study of 500 quasars over five years in the 30
deg area of the Dark Energy Survey (DES) supernova fields. These quasars
have redshifts ranging up to 4 and have apparent AB magnitudes between
mag. The aim of the survey is to measure time lags between
fluctuations in the quasar continuum and broad emission line fluxes of
individual objects in order to measure black hole masses for a broad range of
AGN and constrain the radius-luminosity () relationship. Here we
investigate the expected efficiency of the OzDES reverberation mapping campaign
and its possible extensions. We expect to recover lags for 35-45\% of the
quasars. AGN with shorter lags and greater variability are more likely to yield
a lag, and objects with lags 6 months or 1 year are expected be
recovered the most accurately. The baseline OzDES reverberation mapping
campaign is predicted to produce an unbiased measurement of the
relationship parameters for H, Mg II 2798, and C IV
1549. However, extending the baseline survey by either increasing the
spectroscopic cadence, extending the survey season, or improving the emission
line flux measurement accuracy will significantly improve the parameter
constraints for all broad emission lines.Comment: Published online in MNRAS. 28 page
Flying-fish fishery along the Coromandel coast
The flying-fish fishery is an important seasonal fishery on the east coast of
India extending from Madras to Point CaUmere along the Coromandel
coast. Beyond this region there is no organised fishery for this species
though they have been recorded in small numbers elsewhere along the east
coast and rarely along the west coast. Along the Coromandel coast the
season starts towards the end of May and lasts till the middle of July, though
occasionally it extends up to the middle of August. It has been observed
that the flying-fishes never appear in discoloured and muddy water. It is
reported that, if the monsoons break early and discolour the sea-water with
the silt from the rivers, the fishes migrate away from the shore and the
season comes to an abrupt end
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