364,418 research outputs found
Prospects for Observing the low-density Cosmic Web in Lyman-alpha Emission
Mapping the intergalactic medium (IGM) in Lyman- emission would yield
unprecedented tomographic information on the large-scale distribution of
baryons and potentially provide new constraints on the UV background and
various feedback processes relevant to galaxy formation. Here, we use a
cosmological hydrodynamical simulation to examine the Lyman- emission
of the IGM due to collisional excitations and recombinations in the presence of
a UV background. We focus on gas in large-scale-structure filaments in which
Lyman- radiative transfer effects are expected to be moderate. At low
density the emission is primarily due to fluorescent re-emission of the
ionising UV background due to recombinations, while collisional excitations
dominate at higher densities. We discuss prospects of current and future
observational facilities to detect this emission and find that the emission of
filaments of the cosmic web will typically be dominated by the halos and
galaxies embedded in them, rather than by the lower density filament gas
outside halos. Detecting filament gas directly would require a very long
exposure with a MUSE-like instrument on the ELT. Our most robust predictions
that act as lower limits indicate this would be slightly less challenging at
lower redshifts (). We also find that there is a large amount of
variance between fields in our mock observations. High-redshift protoclusters
appear to be the most promising environment to observe the filamentary IGM in
Lyman- emission.Comment: 20 pages, 13 figures. Accepted for publication in Astronomy &
Astrophysics. Accepted version contains several revisions following
suggestions made in the review proces
Applying OGC sensor web enablement to ocean observing systems
The complexity of marine installations
for ocean observing systems has grown significantly in
recent years. In a network consisting of tens, hundreds
or thousands of marine instruments, manual
configuration and integration becomes very
challenging. Simplifying the integration process in
existing or newly established observing systems would
benefit system operators and is important for the
broader application of different sensors. This article
presents an approach for the automatic configuration
and integration of sensors into an interoperable
Sensor Web infrastructure. First, the sensor
communication model, based on OGC's SensorML
standard, is utilized. It serves as a generic driver
mechanism since it enables the declarative and
detailed description of a sensor's protocol. Finally, we
present a data acquisition architecture based on the
OGC PUCK protocol that enables storage and
retrieval of the SensorML document from the sensor
itself, and automatic integration of sensors into an
interoperable Sensor Web infrastructure. Our
approach adopts Efficient XML Interchange (EXI) as
alternative serialization form of XML or JSON. It
solves the bandwidth problem of XML and JSON.Peer ReviewedPostprint (author's final draft
An evaluation of the role of sentiment in second screen microblog search tasks
The recent prominence of the real-time web is proving both challenging and disruptive for information retrieval and web data mining research. User-generated content on the real-time web is perhaps best epitomised by content on microblogging platforms, such as Twitter. Given the substantial quantity of microblog posts that may be relevant to a user's query at a point in time, automated methods are required to sift through this information. Sentiment analysis offers a promising direction for modelling microblog content. We build and evaluate a sentiment-based filtering system using real-time user studies. We find a significant role played by sentiment in the search scenarios, observing detrimental effects in filtering out certain sentiment types. We make a series of observations regarding associations between document-level sentiment and user feedback, including associations with user profile attributes, and users' prior topic sentiment
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Technology - Empowering the Educational Researcher through Remote Observation
Observing students using computers often occurs through three methods: user-lab, on-site and remote data logging. Whilst each of these have their advantages with the new type of students such as elearners, an alternative method called web-conferencing remote observation is presented for observing students at a distance. This method collects both audio and video data of the observer through webcams and voice/video conversations. Students are able to interact with the software through application sharing facilities. Further, it allows both quantitative and qualitative data to be collected. This proof-of-concept method is presented here where it has been used in two previous studies using Windows Messenger and Netviewer. Although, video quality is not high the quality is sufficient for observational data
Interpretation of the OGLE Q2237+0305 microlensing light-curve
The four bright images of the gravitationally lensed quasar Q2237+0305 are
being monitored from the ground (eg. OGLE collaboration, Apache Point
Observatory) in the hope of observing a high magnification event (HME). Over
the past three seasons (1997-1999) the OGLE collaboration has produced
microlensing light-curves with unprecedented coverage. These demonstrate
smooth, independent (therefore microlensing) variability between the images
(Wozniak et al. 2000a,b; OGLE web page). We have retrospectively compared
probability functions for high-magnification event parameters with several
observed light-curve features. We conclude that the 1999 image C peak was due
to the source having passed outside of a cusp rather than to a caustic
crossing. In addition, we find that the image C light-curve shows evidence for
a caustic crossing between the 1997 and 1998 observing seasons involving the
appearance of new critical images. Our models predict that the next image C
event is most likely to arrive 500 days following the 1999 peak, but with a
large uncertainty (100-2000 days). Finally, given the image A light-curve
derivative at the end of the 1999 observing season, our modelling suggests that
a caustic crossing will occur between the 1999 and 2000 observing seasons,
implying a minimum for the image A light-curve ~1-1.5 magnitudes fainter than
the November 1999 level.Comment: 11 pages, 15 figures. Accepted for publication in M.N.R.A.
Sensor Webs with a Service-Oriented Architecture for On-demand Science Products
This paper describes the work being managed by the NASA Goddard Space Flight Center (GSFC) Information System Division (ISD) under a NASA Earth Science Technology Ofice (ESTO) Advanced Information System Technology (AIST) grant to develop a modular sensor web architecture which enables discovery of sensors and workflows that can create customized science via a high-level service-oriented architecture based on Open Geospatial Consortium (OGC) Sensor Web Enablement (SWE) web service standards. These capabilities serve as a prototype to a user-centric architecture for Global Earth Observing System of Systems (GEOSS). This work builds and extends previous sensor web efforts conducted at NASA/GSFC using the Earth Observing 1 (EO-1) satellite and other low-earth orbiting satellites
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