3,823 research outputs found
The Second Galex Ultraviolet Variability (GUVV-2) Catalog
We present the second Galaxy Evolution Explorer (GALEX) Ultraviolet
Variability (GUVV-2) Catalog that contains information on 410 newly discovered
time-variable sources gained through simultaneous near (NUV 1750-2750A) and far
(FUV 1350-1750A) ultraviolet photometric observations. Source variability was
determined by comparing the NUV and/or FUV fluxes derived from orbital
exposures recorded during a series of multiple observational visits to 169
GALEX fields on the sky. These sources, which were contained within a sky-area
of 161 square deg, varied on average by amplitudes of NUV = 0.6 mag and FUV =
0.9 mag during these observations. Of the 114 variable sources in the catalog
with previously known identifications, 67 can be categorized as being active
galaxies (QSO's, Seyfert 1 or BL Lac objects). The next largest groups of UV
variables are RR Lyrae stars, X-ray sources and novae.
By using a combination of UV and visible color-color plots we have been able
to tentatively identify 36 possible RR Lyrae and/or Delta Scuti type stars, as
well as 35 probable AGN's, many of which may be previously unidentified QSO's
or blazars. Finally, we show data for 3 particular variable objects: the
contact binary system of SDSS J141818.97+525006.7, the eclipsing dwarf nova
system of IY UMa and the highly variable unidentified source SDSS
J104325.06+563258.1.Comment: Astronomical Journal accepte
Ontological theory for ontological engineering: Biomedical systems information integration
Software application ontologies have the potential to become the keystone in state-of-the-art information management techniques. It is expected that these ontologies will support the sort of reasoning power required to navigate large and complex terminologies correctly and efficiently. Yet, there is one problem in particular that continues to stand in our way. As these terminological structures increase in size and complexity, and the drive to integrate them inevitably swells, it is clear that the level of consistency required for such navigation will become correspondingly difficult to maintain. While descriptive semantic representations are certainly a necessary component to any adequate ontology-based system, so long as ontology engineers rely solely on semantic information, without a sound ontological theory informing their modeling decisions, this goal will surely remain out of reach. In this paper we describe how Language and Computing nv (L&C), along with The Institute for Formal Ontology and Medical Information Sciences (IFOMIS), are working towards developing and implementing just such a theory, combining the open
software architecture of L&Câs LinkSuiteTM with the philosophical rigor of IFOMISâs Basic Formal Ontology. In this way we aim to move beyond the more or less simple controlled vocabularies that have dominated the industry to date
Does money matter in inflation forecasting?
This paper provides the most fully comprehensive evidence to date on whether or not monetary aggregates are valuable for forecasting US inflation in the early to mid 2000s. We explore a wide range of different definitions of money, including different methods of aggregation and different collections of included monetary assets. In our forecasting experiment we use two non-linear techniques, namely, recurrent neural networks and kernel recursive least squares regression - techniques that are new to macroeconomics. Recurrent neural networks operate with potentially unbounded input memory, while the kernel regression technique is a finite memory predictor. The two methodologies compete to find the best fitting US inflation forecasting models and are then compared to forecasts from a naive random walk model. The best models were non-linear autoregressive models based on kernel methods. Our findings do not provide much support for the usefulness of monetary aggregates in forecasting inflation.Forecasting ; Inflation (Finance) ; Monetary theory
GALEX observations of quasar variability in the ultraviolet
Using archival observations recorded over a 5+ year timeframe with the NASA
Galaxy Evolution Explorer (GALEX) satellite, we present a study of the
ultraviolet (UV) variability of 4360 quasars of redshifts up to z=2.5 that have
optical counterparts in the Sloan Digital Sky Survey DR5 spectroscopic catalog.
The observed changes in both the far UV (FUV: 1350-1785A) and near UV (NUV:
1770-2830A) AB magnitudes as a function of time may help differentiate between
models of the emission mechanisms thought to operate in these active galaxies.
A list of NUV and FUV variable quasars was derived from the UV light-curves of
sources with 5 or more observational visits by GALEX that spanned a time-frame
greater than 3 months. By measuring the error in the derived mean UV magnitude
from the series of GALEX observations for each source, quasars whose UV
variability was greater than the 3-sigma variance from the mean observed value
were deemed to be (intrinsically) UV variable. This conservative selection
criterion (which was applied to both FUV and NUV observations) resulted in
identifying 550 NUV and 371 FUV quasars as being statistically significant UV
variable objects.Comment: A&A Accepted, spelling of author's name corrected (Neill
Angular two-photon interference and angular two-qubit states
Using angular-position-orbital-angular-momentum entangled photons, we study angular two-photon interference in a scheme in which entangled photons are made to pass through apertures in the form of double angular slits, and using this scheme, we demonstrate an entangled two-qubit state that is based on the angular-position correlations of entangled photons. The entanglement of the two-qubit state is quantified in terms of concurrence. These results provide an additional means for preparing entangled quantum states for use in quantum information protocols
Objectively discerning Autler-Townes Splitting from Electromagnetically Induced Transparency
Autler-Townes splitting (ATS) and electromagnetically-induced transparency
(EIT) both yield transparency in an absorption profile, but only EIT yields
strong transparency for a weak pump field due to Fano interference. Empirically
discriminating EIT from ATS is important but so far has been subjective. We
introduce an objective method, based on Akaike's information criterion, to test
ATS vs. EIT from experimental data and determine which pertains. We apply our
method to a recently reported induced-transparency experiment in
superconducting circuit quantum electrodynamics.Comment: Extended discussion of ATS vs. EIT testing in realistic systems is
given. Two figures were combined and one new was adde
Assimilation of satellite images into a sediment transport model of Lake Michigan
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95634/1/wrcr11678.pd
Bayesian inference for high-dimensional discrete-time epidemic models: spatial dynamics of the UK COVID-19 outbreak
In the event of a disease outbreak emergency, such as COVID-19, the ability
to construct detailed stochastic models of infection spread is key to
determining crucial policy-relevant metrics such as the reproduction number,
true prevalence of infection, and the contribution of population
characteristics to transmission. In particular, the interaction between space
and human mobility is key to prioritising outbreak control resources to
appropriate areas of the country. Model-based epidemiological intelligence must
therefore be provided in a timely fashion so that resources can be adapted to a
changing disease landscape quickly. The utility of these models is reliant on
fast and accurate parameter inference, with the ability to account for large
amount of censored data to ensure estimation is unbiased. Yet methods to fit
detailed spatial epidemic models to national-level population sizes currently
do not exist due to the difficulty of marginalising over the censored data. In
this paper we develop a Bayesian data-augmentation method which operates on a
stochastic spatial metapopulation SEIR state-transition model, using
model-constrained Metropolis-Hastings samplers to improve the efficiency of an
MCMC algorithm. Coupling this method with state-of-the-art GPU acceleration
enabled us to provide nightly analyses of the UK COVID-19 outbreak, with timely
information made available for disease nowcasting and forecasting purposes
Translocation of Crohn's disease Escherichia coli across M-cells: contrasting effects of soluble plant fibres and emulsifiers
Background Crohns disease is common in developed nations where the typical diet is low in fibre and high in processed food. Primary lesions overlie Peyers patches and colonic lymphoid follicles where bacterial invasion through M-cells occurs. We have assessed the effect of soluble non-starch polysaccharide (NSP) and food emulsifiers on translocation of Escherichia coli across M-cells. Methods To assess effects of soluble plant fibres and food emulsifiers on translocation of mucosa-associated E coli isolates from Crohns disease patients and from non-Crohns controls, we used M-cell monolayers, generated by co-culture of Caco2-cl1 and Raji B cells, and human Peyers patches mounted in Ussing chambers. Results E coli translocation increased across M-cells compared to parent Caco2-cl1 monocultures; 15.8-fold (IQR 6.2-32.0) for Crohns disease E coli (N=8) and 6.7-fold (IQR 3.7-21.0) for control isolates (N=5). Electronmicroscopy confirmed E coli within M-cells. Plantain and broccoli NSP markedly reduced E coli translocation across M-cells at 5 mg/ml (range 45.3-82.6% inhibition, pandlt;0.01); apple and leek NSP had no significant effect. Polysorbate-80, 0.01% vol/vol, increased E coli translocation through Caco2-cl1 monolayers 59-fold (pandlt;0.05) and, at higher concentrations, increased translocation across M-cells. Similarly, E coli translocation across human Peyers patches was reduced 45+/-7% by soluble plantain NSP (5 mg/ml) and increased 2-fold by polysorbate-80 (0.1% vol/vol). Conclusions Translocation of E coli across M-cells is reduced by soluble plant fibres, particularly plantain and broccoli, but increased by the emulsifier Polysorbate-80. These effects occur at relevant concentrations and may contribute to the impact of dietary factors on Crohns disease pathogenesis
Cognitive Information Processing
Contains research objectives and summary of research.Madeline Moses FundNational Science Foundation (Grant GK-33736X1)National Institutes of Health (Grant 5 PO1 GM19428-02)Peter Bent Brigham Hospital, Purchase Order G-33196Associated Press (Grant)National Institutes of Health (Grant 5 PO1 GM14940-07
- âŠ