2,039 research outputs found
Digital image analysis of flatfish bleeding injury
To improve accuracy of post-release mortality predictions and facilitate the routine collection of information about physical condition of catches after commercial fishing capture, traditional visual assessment by potentially subjective human observers or raters may be automated by digital image analysis. The purpose of this study was to develop a method and device that can eliminate subjectivity in scoring external injury of commercially beam-trawled flatfish by taking standardized, high resolution images to allow for automated calculation of the % surface area of visible bleeding injury relative to the whole fish based on digital image analysis. A reference library was compiled by photographing ventral sides of 67 fish of six flatfish species of different sizes and freshness (fresh vs defrosted). All fish were sourced from the R/V Simon Stevin while beam-trawling in the Belgian coastal zone of the Southern North Sea. All images that were neither over- nor under-exposed were compiled (n = 51) and scored for the extent (%) of multifocal cutaneous petechial ('point bleeding'), and suffusion or haemorrhaging ('bruising') of the ventral head and body region, respectively, by three experienced raters using a continuous scale (between 0 and 100 %). Then, several state-of-the-art computer vision algorithms were tested on the dataset to develop a protocol that can 1) align each image; 2) identify fin, body and head regions; and 3) quantify the surface area of bleeding injury of each region by using appropriate thresholding techniques. For validation of the computer-derived % surface coverage estimates of bleeding injury, these were compared to the average rater's score. For bruising injury, a significant difference between human- vs computer-derived scores persisted. For point bleeding of the head region, computer-based estimates of % coverage were not different from those of the human raters. Overall, species, size and their freshness did not have a significant effect. By consistently recording the coverage of externally visible bleeding injury, this image analysis protocol may find its application in measuring the effect of different capture techniques on whole fish quality, and in improving vitality assessments as part of the transition towards a more sustainable fishery and the implementation of the European Landing Obligation
Model-Based Edge Detector for Spectral Imagery Using Sparse Spatiospectral Masks
Two model-based algorithms for edge detection in spectral imagery are developed that specifically target capturing intrinsic features such as isoluminant edges that are characterized by a jump in color but not in intensity. Given prior knowledge of the classes of reflectance or emittance spectra associated with candidate objects in a scene, a small set of spectral-band ratios, which most profoundly identify the edge between each pair of materials, are selected to define a edge signature. The bands that form the edge signature are fed into a spatial mask, producing a sparse joint spatiospectral nonlinear operator. The first algorithm achieves edge detection for every material pair by matching the response of the operator at every pixel with the edge signature for the pair of materials. The second algorithm is a classifier-enhanced extension of the first algorithm that adaptively accentuates distinctive features before applying the spatiospectral operator. Both algorithms are extensively verified using spectral imagery from the airborne hyperspectral imager and from a dots-in-a-well midinfrared imager. In both cases, the multicolor gradient (MCG) and the hyperspectral/spatial detection of edges (HySPADE) edge detectors are used as a benchmark for comparison. The results demonstrate that the proposed algorithms outperform the MCG and HySPADE edge detectors in accuracy, especially when isoluminant edges are present. By requiring only a few bands as input to the spatiospectral operator, the algorithms enable significant levels of data compression in band selection. In the presented examples, the required operations per pixel are reduced by a factor of 71 with respect to those required by the MCG edge detector
Mean-field interacting multi-type birth-death processes with a view to applications in phylodynamics
Multi-type birth-death processes underlie approaches for inferring
evolutionary dynamics from phylogenetic trees across biological scales, ranging
from deep-time species macroevolution to rapid viral evolution and somatic
cellular proliferation. A limitation of current phylogenetic birth-death models
is that they require restrictive linearity assumptions that yield tractable
likelihoods, but that also preclude interactions between individuals. Many
fundamental evolutionary processes -- such as environmental carrying capacity
or frequency-dependent selection -- entail interactions, and may strongly
influence the dynamics in some systems. Here, we introduce a multi-type
birth-death process in mean-field interaction with an ensemble of replicas of
the focal process. We prove that, under quite general conditions, the
ensemble's stochastically evolving interaction field converges to a
deterministic trajectory in the limit of an infinite ensemble. In this limit,
the replicas effectively decouple, and self-consistent interactions appear as
nonlinearities in the infinitesimal generator of the focal process. We
investigate a special case that is amenable to calculations in the context of a
phylogenetic birth-death model, and is rich enough to model both carrying
capacity and frequency-dependent selection.Comment: 30 pages, 1 figur
Effects of privatization and agencification on citizens and citizenship: an international comparison
Effects of privatization and agencification on citizens and citizenship: an international comparison
Effects of privatization and agencification on citizens and citizenship: an international comparison
This study has been compiled as an internationally comparative contribution to the
parliamentary inquiry by the Dutch Senate into the effects of privatization and agencification
on the relationship between citizens and the (national) government. Knowledge on this topic
is scarce and scattered across different sources. Therefore, this paper consists of three
different sections. Each section deals with a different question and uses different sources. In
this overview we summarize the main findings of the three sections
Dynamic pathway of the photoinduced phase transition of TbMnO
We investigate the demagnetization dynamics of the cycloidal and sinusoidal
phases of multiferroic TbMnO by means of time-resolved resonant soft x-ray
diffraction following excitation by an optical pump. Using orthogonal linear
x-ray polarizations, we suceeded in disentangling the response of the
multiferroic cycloidal spin order from the sinusoidal antiferromagnetic order
in the time domain. This enables us to identify the transient magnetic phase
created by intense photoexcitation of the electrons and subsequent heating of
the spin system on a picosecond timescale. The transient phase is shown to be a
spin density wave, as in the adiabatic case, which nevertheless retains the
wave vector of the cycloidal long range order. Two different pump photon
energies, 1.55 eV and 3.1 eV, lead to population of the conduction band
predominantly via intersite - transitions or intrasite -
transitions, respectively. We find that the nature of the optical excitation
does not play an important role in determining the dynamics of magnetic order
melting. Further, we observe that the orbital reconstruction, which is induced
by the spin ordering, disappears on a timescale comparable to that of the
cycloidal order, attesting to a direct coupling between magnetic and orbital
orders. Our observations are discussed in the context of recent theoretical
models of demagnetization dynamics in strongly correlated systems, revealing
the potential of this type of measurement as a benchmark for such complex
theoretical studies
GEMS Survey Data and Catalog
We describe the data reduction and object cataloging for the GEMS survey, a large-area (800 arcmin(2)) two-band (F606W and F850LP) imaging survey with the Advanced Camera for Surveys on the Hubble Space Telescope, centered on the Chandra Deep Field-South.STScI HST-GO-9500.01NASA GO-9500, NAS5-26555, NAG5-13063, NAG5-13102European Communityâs Human Potential Programunder contractHPRN-CT-2002-00316, HPRN-CT-2002-00305McDonald Observator
An eolian dust origin for clastic fines of Devono-Mississippian mudrocks of the greater North American midcontinent
Upper Devonian and LowerâMiddle Mississippian strata of the North American midcontinent are ubiquitously fine-grained and silt-rich, comprising both so-called shale as well as argillaceous limestone (or calcareous siltstone) that accumulated in the Laurentian epeiric sea. Although long recognized as recording marine deposition, the origin and transport of the fine-grained siliciclastic material in these units remains enigmatic because they do not connect to any proximal deltaic feeder systems. Here, we present new data on grain size, whole-rock geochemistry, mineralogy, and U-Pb detrital-zircon geochronology from units across Oklahoma; we then integrate these data with models of surface wind circulation, refined paleogeographic reconstructions, and correlations from the greater midcontinent to test the hypothesis that wind transported the siliciclastic fraction to the marine system. The exclusively very fine silt to very fine sand grain size, clear detrital origin, widespread distribution over large regions of the epeiric sea, Appalachian sources, and paleogeographic setting in the subtropical arid belt far-removed from contemporaneous deltaic feeder systems are most consistent with eolian transport of dust lofted from subaerial delta plains of the greater Appalachian orogen and incorporated into subaqueous depositional systems. Delivery of dust that was minimally chemically weathered to Devono-Mississippian epeiric seas likely provided essential nutrients that stimulated organic productivity in these commonly organic-rich units
An Explanation for the Observed Weak Size Evolution of Disk Galaxies
Surveys of distant galaxies with the Hubble Space Telescope and from the
ground have shown that there is only mild evolution in the relationship between
radial size and stellar mass for galactic disks from z~1 to the present day.
Using a sample of nearby disk-dominated galaxies from the Sloan Digital Sky
Survey (SDSS), and high redshift data from the GEMS (Galaxy Evolution from
Morphology and SEDs) survey, we investigate whether this result is consistent
with theoretical expectations within the hierarchical paradigm of structure
formation. The relationship between virial radius and mass for dark matter
halos in the LCDM model evolves by about a factor of two over this interval.
However, N-body simulations have shown that halos of a given mass have less
centrally concentrated mass profiles at high redshift. When we compute the
expected disk size-stellar mass distribution, accounting for this evolution in
the internal structure of dark matter halos and the adiabatic contraction of
the dark matter by the self-gravity of the collapsing baryons, we find that the
predicted evolution in the mean size at fixed stellar mass since z~1 is about
15-20 percent, in good agreement with the observational constraints from GEMS.
At redshift z~2, the model predicts that disks at fixed stellar mass were on
average only 60% as large as they are today. Similarly, we predict that the
rotation velocity at a given stellar mass (essentially the zero-point of the
Tully-Fisher relation) is only about 10 percent larger at z~1 (20 percent at
z~2) than at the present day.Comment: 13 pages, 6 figures, accepted for publication in ApJ. Revised in
response to referee's comments to improve clariry. Results are unchange
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