1,578 research outputs found
New distance measures for classifying X-ray astronomy data into stellar classes
The classification of the X-ray sources into classes (such as extragalactic
sources, background stars, ...) is an essential task in astronomy. Typically,
one of the classes corresponds to extragalactic radiation, whose photon
emission behaviour is well characterized by a homogeneous Poisson process. We
propose to use normalized versions of the Wasserstein and Zolotarev distances
to quantify the deviation of the distribution of photon interarrival times from
the exponential class. Our main motivation is the analysis of a massive dataset
from X-ray astronomy obtained by the Chandra Orion Ultradeep Project (COUP).
This project yielded a large catalog of 1616 X-ray cosmic sources in the Orion
Nebula region, with their series of photon arrival times and associated
energies. We consider the plug-in estimators of these metrics, determine their
asymptotic distributions, and illustrate their finite-sample performance with a
Monte Carlo study. We estimate these metrics for each COUP source from three
different classes. We conclude that our proposal provides a striking amount of
information on the nature of the photon emitting sources. Further, these
variables have the ability to identify X-ray sources wrongly catalogued before.
As an appealing conclusion, we show that some sources, previously classified as
extragalactic emissions, have a much higher probability of being young stars in
Orion Nebula.Comment: 29 page
Remote sensing and geographic information systems: charting Sin Nombre virus infections in deer mice.
We tested environmental data from remote sensing and geographic information system maps as indicators of Sin Nombre virus (SNV) infections in deer mouse (Peromyscus maniculatus) populations in the Walker River Basin, Nevada and California. We determined by serologic testing the presence of SNV infections in deer mice from 144 field sites. We used remote sensing and geographic information systems data to characterize the vegetation type and density, elevation, slope, and hydrologic features of each site. The data retroactively predicted infection status of deer mice with up to 80% accuracy. If models of SNV temporal dynamics can be integrated with baseline spatial models, human risk for infection may be assessed with reasonable accuracy
Electrospun Polymer Fiber Lasers for Applications in Vapor Sensing
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138331/1/adom201700248_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138331/2/adom201700248.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138331/3/adom201700248-sup-0001-S1.pd
Impact of ultraviolet radiation on marine crustacean zooplankton and ichthyoplankton: a synthesis of results from the estuary and Gulf of St. Lawrence, Canada
The objectives of the research program reported upon here were (1) to measure ambient levels of UV radiation and
determine whichvariables most strongly affected its attenuation in the waters of the estuary and Gulf of St. Lawrence, Canada; and
(2) to investigate the potential direct impacts of W radiation on species of crustacean zooplankton and fish whose early life stages
are planktonic. In this geographic region, productivity-determining biophysical interactions occur in the upper 0 to 30 m of the
water column. Measurements of the diffuse attenuation coefficients for ultraviolet-B radiation (W-B, 280 to 320 nm) at various
locations in this region indicated maximum 10% depths (the depth to which 10% of the surface energy penetrates at a given wavelength)
of 3 to 4 m at a wavelength of 310 nm. Organisms residing in this layer-including the eggs and larvae of Calanus finmarchicus
and Atlantic cod Gadus morhua-are exposed to biologically damaging levels of W radiation. As a result of these physical
and biological characteristics, this system offered a relevant opportunity to assess the impacts of UV on subarctic marine
ecosystems. Eggs of C. finmarchicus were incubated under the sun, with and without the W-B and/or UV-A (320 to 400 nm) wavebands.
W-exposed eggs exhibited low percent hatchmg compared to those protected from W : W radiation had a strong negative
impact on C. finmarchicus eggs. Further, percent hatching in W-B-exposed eggs was not significantly lower than that in eggs
exposed to UV-A only: under natural sunlight, UV-A radiation appeared to be more detrimental to C. finmarchicus embryos than
was UV-B. In analogous experiments with Atlantic cod eggs, exposure to UV-B produced a significant negative effect. However,
UV-A had no negative effect on cod eggs. Additional experiments using a solar simulator (SS) revealed high wavelength-dependent
mortality in both C. finmarchicus and cod embryos exposed to UV. The strongest effects occurred under exposures to wavelengths
below 312 nm. At the shorter wavelengths (<305 nm) UV-B-induced mortality was strongly dose-dependent, but (for both
C. finmarchicus and cod) not significantly influenced by dose-rate. Thus, at least within the limits of the exposures under which the
biological weighting functions (BWFs) were generated, reciprocity held. The BWFs derived for UV-B-induced mortality in C. finmarchicus
and cod eggs were similar in shape to the action spectrum for UV-B effects on naked DNA. Further, the wavelengthdependence
of DNA damage was similar to that for the mortality effect. These observations suggest that W-induced mortality in
C. finmarchicus and cod eggs is a direct result of DNA damage. There was no evidence of a detrimental effect of UV-A radiation in
these SS-derived results. A mathematical model that includes the BWFs, vertical mixing of eggs, meteorological and hydrographic
conditions, and ozone depletion, indicates that W-induced mortality in the C. finmarchicus egg population could be as high as
32.5 %, while the impact on the cod egg population was no more than 1.2%. Variability in cloud cover, water transparency (and the
variables that affect it), and vertical distribution and displacement of planktonic organisms within the mixed layer can all have a
greater effect on the flux of UV-B radiation to which they are exposed than will ozone layer depletion at these latitudes. Our observations
indicate that C, finmarchicus and cod eggs present in the first meter of the water column (likely only a small percentage of
the total egg populations) are susceptible to W radiation. However, although exposure to UV can negatively impact crustacean
zooplankton and ichthyoplankton populations, these direct effects are likely minimal within the context of all the other environmental
factors that produce the very high levels of mortality typically observed in their planktonic early life stages. The impact of
indnect effects-which may well be of much greater import-has yet to be evaluated
Bridging the gap between marine biogeochemical and fisheries sciences; configuring the zooplankton link
Exploring climate and anthropogenic impacts on marine ecosystems requires an understanding of how trophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or modelling) are rare. Experimental investigations often concentrate on a particular group or individual species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up approach concentrating on the phytoplankton community or a top-down approach concentrating on the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton-dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling activities identifying important issues that warrant further experimental and modelling investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient history. In particular there is a need for dynamic data series in which predator and prey of known nutrient history are studied interacting under varied pH and temperature regimes
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A narrative in three acts: Using combinations of image schemas to model events
Image schemas have been proposed as conceptual building blocks corresponding to the hypothesised most fundamental embodied experiences. We formally investigate how combinations of image schemas (or 'image schematic profiles') can model essential aspects of events, and discuss benefits for artificial intelligence and cognitive systems research, in particular concerning the role of such basic events in concept formation. More specifically, as exemplary illustrations and proof of concept the image schemas Object, Contact, and Path are combined to form the events Blockage, Bouncing, and Caused-Movement. Additionally, an outline of a proposed conceptual hierarchy of levels of modelling for image schemas and similar cognitive theories is given
On-demand semiconductor single-photon source with near-unity indistinguishability
Single photon sources based on semiconductor quantum dots offer distinct
advantages for quantum information, including a scalable solid-state platform,
ultrabrightness, and interconnectivity with matter qubits. A key prerequisite
for their use in optical quantum computing and solid-state networks is a high
level of efficiency and indistinguishability. Pulsed resonance fluorescence
(RF) has been anticipated as the optimum condition for the deterministic
generation of high-quality photons with vanishing effects of dephasing. Here,
we generate pulsed RF single photons on demand from a single,
microcavity-embedded quantum dot under s-shell excitation with 3-ps laser
pulses. The pi-pulse excited RF photons have less than 0.3% background
contributions and a vanishing two-photon emission probability.
Non-postselective Hong-Ou-Mandel interference between two successively emitted
photons is observed with a visibility of 0.97(2), comparable to trapped atoms
and ions. Two single photons are further used to implement a high-fidelity
quantum controlled-NOT gate.Comment: 11 pages, 11 figure
Characteristics of transposable element exonization within human and mouse
Insertion of transposed elements within mammalian genes is thought to be an
important contributor to mammalian evolution and speciation. Insertion of
transposed elements into introns can lead to their activation as alternatively
spliced cassette exons, an event called exonization. Elucidation of the
evolutionary constraints that have shaped fixation of transposed elements
within human and mouse protein coding genes and subsequent exonization is
important for understanding of how the exonization process has affected
transcriptome and proteome complexities. Here we show that exonization of
transposed elements is biased towards the beginning of the coding sequence in
both human and mouse genes. Analysis of single nucleotide polymorphisms (SNPs)
revealed that exonization of transposed elements can be population-specific,
implying that exonizations may enhance divergence and lead to speciation. SNP
density analysis revealed differences between Alu and other transposed
elements. Finally, we identified cases of primate-specific Alu elements that
depend on RNA editing for their exonization. These results shed light on TE
fixation and the exonization process within human and mouse genes.Comment: 11 pages, 4 figure
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