20,022 research outputs found
The KINDRA project. Sharing and evaluating groundwater research and knowledge in Europe
Groundwater knowledge and research in the European Union is often scattered and non-standardised, because of different subjects involved and different approaches from Member States. The Horizon2020 project KINDRA has conducted an EU-wide assessment of existing groundwater-related practical and scientific knowledge based on a new Hydrogeological Research Classification System, identifying more than 280 keywords related to three main categories (namely Operational Actions, Research topics and Societal Challenges) to be intersected in a 3D-diagram approach. The classification is supported by a web-service, the European Inventory of Groundwater Research, which acts not only as knowledge repository but also as a tool to help identify relevant researchm topics, existing research trends and critical research challenges. The records have been uploaded during the project by 20 national experts from National Associations of Geologists, under the umbrella of the European Federation of Geologists. The total number of metadata included in the inventory at the end of the project are about 2300, and the analysis of the results is considered useful for producing synergies, implementing policies and optimising water management in Europe. By the use of additional indicators, the database content has been analysed by occurrence of keywords, type of document, level of innovation. Using the three-axes classification, more easily understandable by 2D diagrams as bubble
plots, occurrence and relationship of different topics (main categories) in groundwater research have been highlighted. This article summarizes the activities realized in relation to the common classification system and to the metadata included in the EIGR, showing the distribution of thecollected information in different categories and attributes identified by the classification
On the rapid demise of Lyman-alpha emitters at z>7 due to the increasing incidence of optically thick absorption systems
A variety of independent observational studies have now reported a
significant decline in the fraction of Lyman-break galaxies which exhibit Ly-a
emission over the redshift interval z=6-7. In combination with the strong
damping wing extending redward of Ly-a in the spectrum of the bright z=7.085
quasar ULAS 1120+0641, this has strengthened suggestions that the hydrogen in
the intergalactic medium (IGM) is still substantially neutral at z~7. Current
theoretical models imply HI fractions as large as 40-90 per cent may be
required to explain these data assuming there is no intrinsic evolution in the
Ly-a emitter population. We propose that such large neutral fractions are not
necessary. Based on a hydrodynamical simulation which reproduces the absorption
spectra of high-redshift (z~6-7) quasars, we demonstrate that the opacity of
the intervening IGM redward of rest-frame Ly-a can rise rapidly in average
regions of the Universe simply because of the increasing incidence of
absorption systems which are optically thick to Lyman continuum photons as the
tail-end of reionisation is approached. Our simulations suggest these data do
not require a large change in the IGM neutral fraction by several tens of per
cent from z=6-7, but may instead be indicative of the rapid decrease in the
typical mean free path for ionising photons expected during the final stages of
reionisation.Comment: 11 pages, 6 figures, accepted to MNRA
Designing an Adaptive Web Navigation Interface for Users with Variable Pointing Performance
Many online services and products require users to point and interact with user interface elements. For individuals who experience variable pointing ability due to physical impairments, environmental issues or age, using an input device (e.g., a computer mouse) to select elements on a website can be difficult. Adaptive user interfaces dynamically change their functionality in response to user behavior. They can support individuals with variable pointing abilities by 1) adapting dynamically to make element selection easier when a user is experiencing pointing difficulties, and 2) informing users about these pointing errors. While adaptive interfaces are increasingly prevalent on the Web, little is known about the preferences and expectations of users with variable pointing abilities and how to design systems that dynamically support them given these preferences.
We conducted an investigation with 27 individuals who intermittently experience pointing problems to inform the design of an adaptive interface for web navigation. We used a functional high-fidelity prototype as a probe to gather information about user preferences and expectations. Our participants expected the system to recognize and integrate their preferences for how pointing tasks were carried out, preferred to receive information about system functionality and wanted to be in control of the interaction. We used findings from the study to inform the design of an adaptive Web navigation interface, PINATA that tracks user pointing performance over time and provides dynamic notifications and assistance tailored to their specifications. Our work contributes to a better understanding of users' preferences and expectations of the design of an adaptive pointing system
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Mashup cartography: cartographic issues of using Google Earth for tag maps
Slashdot, open news and informated media: exploring the intersection of imagined futures and web publishing technology
"In this essay, my interest is in how imagined media futures are implicated in the work of producing novel web publishing technology. I explore the issue through an account of the emergence of Slashdot, the tech news and discussion site that by 1999 had implemented a number of recommendation features now associated with social media and web 2.0 platforms. Specifically, I aim to understand the connection between the development of Slashdot’s influential content-management system (CMS) - an elaborate publishing infrastructure called “Slash” that allowed editors to choose reader submissions for publication and automatically distributed the work of moderating the comments sections among trusted users - and two distinct visions of a web-enabled transformation of media production.
How algorithmic popularity bias hinders or promotes quality
Algorithms that favor popular items are used to help us select among many
choices, from engaging articles on a social media news feed to songs and books
that others have purchased, and from top-raked search engine results to
highly-cited scientific papers. The goal of these algorithms is to identify
high-quality items such as reliable news, beautiful movies, prestigious
information sources, and important discoveries --- in short, high-quality
content should rank at the top. Prior work has shown that choosing what is
popular may amplify random fluctuations and ultimately lead to sub-optimal
rankings. Nonetheless, it is often assumed that recommending what is popular
will help high-quality content "bubble up" in practice. Here we identify the
conditions in which popularity may be a viable proxy for quality content by
studying a simple model of cultural market endowed with an intrinsic notion of
quality. A parameter representing the cognitive cost of exploration controls
the critical trade-off between quality and popularity. We find a regime of
intermediate exploration cost where an optimal balance exists, such that
choosing what is popular actually promotes high-quality items to the top.
Outside of these limits, however, popularity bias is more likely to hinder
quality. These findings clarify the effects of algorithmic popularity bias on
quality outcomes, and may inform the design of more principled mechanisms for
techno-social cultural markets
Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
Observations of the high-redshift Universe with the 21 cm hyperfine line of
neutral hydrogen promise to open an entirely new window onto the early phases
of cosmic structure formation. Here we review the physics of the 21 cm
transition, focusing on processes relevant at high redshifts, and describe the
insights to be gained from such observations. These include measuring the
matter power spectrum at z~50, observing the formation of the cosmic web and
the first luminous sources, and mapping the reionization of the intergalactic
medium. The epoch of reionization is of particular interest, because large HII
regions will seed substantial fluctuations in the 21 cm background. We also
discuss the experimental challenges involved in detecting this signal, with an
emphasis on the Galactic and extragalactic foregrounds. These increase rapidly
toward low frequencies and are especially severe for the highest redshift
applications. Assuming that these difficulties can be overcome, the redshifted
21 cm line will offer unique insight into the high-redshift Universe,
complementing other probes but providing the only direct, three-dimensional
view of structure formation from z~200 to z~6.Comment: extended review accepted by Physics Reports, 207 pages, 44 figures
(some low resolution); version with high resolution figures available at
http://pantheon.yale.edu/~srf28/21cm/index.htm; minor changes to match
published versio
Fingerprint of Galactic Loop I on polarized microwave foregrounds
Context: Currently, detection of the primordial gravitational waves by the
B-mode of Cosmic Microwave Background (CMB) is primarily limited by our
knowledge of the polarized microwave foreground emissions. Thus improvements of
the foreground analysis are necessary. As revealed
in~\cite{2018arXiv180410382L}, the E-mode and B-mode of the polarized
foreground have noticeable different properties, both in morphology and
frequency spectrum, suggesting that they arise from different physical
processes, and need to be studied separately.
Aims: I will study the polarized emission from Galactic loops, especially
Loop I, and mainly focus on the following issues: Does it contribute
predominantly to the E-mode or B-mode? In which frequency bands and in which
sky regions can it be identified?
Methods: Based on a well known result about the magnetic field alignment in
supernova explosions, a theoretical expectation is established that the loop
polarizations should be predominantly E-mode. In particular, the expected
polarization angles of Loop I are compared with those from the real microwave
band data of WMAP and Planck.
Results and conclusions: The comparison between model and data shows
remarkable consistency between data and expectation at all bands and for a
large area of the sky. This result suggests that the polarized emission of
Galactic Loop I is a major polarized component in all microwave bands from 23
to 353 GHz, and a considerable part of the polarized foreground is likely
originated from a local bubble associated with Loop I, instead of the far more
distant Galactic emission. The result also provides a possible way to explain
the reported E-to-B excess~\citep{2016A&A...586A.133P} by contribution of the
loops. Finally, this work may also provide the first geometrical evidence that
the Earth was hit by a supernova explosion.Comment: Updated using the Planck 2018 data, and the main conclusion is now
even better supporte
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