1,089 research outputs found
Learning by example : training users with high-quality query suggestions
The queries submitted by users to search engines often poorly describe their information needs and represent a potential bottleneck in the system. In this paper we investigate to what extent it is possible to aid users in learning how to formulate better queries by providing examples of high-quality queries interactively during a number of search sessions. By means of several controlled user studies we collect quantitative and qualitative evidence that shows: (1) study participants are able to identify and abstract qualities of queries that make them highly effective, (2) after seeing high-quality example queries participants are able to themselves create queries that are highly effective, and, (3) those queries look similar to expert queries as defined in the literature. We conclude by discussing what the findings mean in the context of the design of interactive search systems
The Christmas Island Seamount Province, Indian Ocean: Origin of Intraplate Volcanism by Shallow Recycling of Continental Lithosphere?
The east-west-trending Christmas Island Seamount
Province (CHRISP, 1800x600 km) in the northeastern Indian
Ocean is elongated orthogonal to present-day plate motion,
posing the question if a mantle plume formed this volcanic
belt. Here we report the first age (Ar/Ar) and geochemical (Sr-
Nd-Hf-Pb DS isotopic data) from the CHRISP seamount
chain. A crude E-W age decrease from the Argo Basin (136
Ma), to the Eastern Wharton Basin (115-94 Ma) to the
Vening-Meinesz seamounts (96-64 Ma) to the Cocos-Keeling
seamounts (56-47 Ma) suggests spatial migration of melting.
Christmas Island, however, yields much younger ages (44-4
Ma), inconsistent with an age progression. The isotopic
compositions (e.g. 206Pb/204Pb = 17.3-19.3; 207Pb/204Pb = 15.49-
15.67; 143Nd/144Nd = 0.51220-0.51295; 176Hf/177Hf = 0.28246-
0.28319) range from enriched MORB (or âCâ) to very
enriched mantle (EM1) type compositions more typical of
continental than oceanic volcanism. Lamproitic and
kimberlitic rocks from western Australia, India and other
continental areas, derived from metasomatized subcontinental
lithospheric mantle, could serve as the EM1 type endmembers.
The morphology, ages and chemical composition of the
CHRISP, combined with plate tectonic reconstructions, cannot
be easily explained within the framework of the mantle plume
hypotheses. We therefore propose that the seamounts are
derived through the recycling of continental lithosphere
(mantle ± lower crust) delaminated during the breakup of
Gondwana and brought to the surface at the former spreading
centers separating Argoland (western Burma), Greater India
and Australia
A Textured Silicon Calorimetric Light Detector
We apply the standard photovoltaic technique of texturing to reduce the
reflectivity of silicon cryogenic calorimetric light detectors. In the case of
photons with random incidence angles, absorption is compatible with the
increase in surface area. For the geometrically thin detectors studied, energy
resolution from athermal phonons, dominated by position dependence, is
proportional to the surface-to-volume ratio. With the CaWO4 scintillating
crystal used as light source, the time constants of the calorimeter should be
adapted to the relatively slow light-emission times.Comment: Submitted to Journal of Applied Physic
The -cleus experiment: A gram-scale fiducial-volume cryogenic detector for the first detection of coherent neutrino-nucleus scattering
We discuss a small-scale experiment, called -cleus, for the first
detection of coherent neutrino-nucleus scattering by probing nuclear-recoil
energies down to the 10 eV-regime. The detector consists of low-threshold
CaWO and AlO calorimeter arrays with a total mass of about 10 g and
several cryogenic veto detectors operated at millikelvin temperatures.
Realizing a fiducial volume and a multi-element target, the detector enables
active discrimination of , neutron and surface backgrounds. A first
prototype AlO device, operated above ground in a setup without
shielding, has achieved an energy threshold of eV and further
improvements are in reach. A sensitivity study for the detection of coherent
neutrino scattering at nuclear power plants shows a unique discovery potential
(5) within a measuring time of weeks. Furthermore, a site
at a thermal research reactor and the use of a radioactive neutrino source are
investigated. With this technology, real-time monitoring of nuclear power
plants is feasible.Comment: 14 pages, 19 figure
The CRESST Experiment: Recent Results and Prospects
The CRESST experiment seeks hypothetical WIMP particles that could account
for the bulk of dark matter in the Universe. The detectors are cryogenic
calorimeters in which WIMPs would scatter elastically on nuclei, releasing
phonons. The first phase of the experiment has successfully deployed several
262 g sapphire devices in the Gran Sasso underground laboratories. A main
source of background has been identified as microscopic mechanical fracturing
of the crystals, and has been eliminated, improving the background rate by up
to three orders of magnitude at low energies, leaving a rate close to one count
per day per kg and per keV above 10 keV recoil energy. This background now
appears to be dominated by radioactivity, and future CRESST scintillating
calorimeters which simultaneously measure light and phonons will allow
rejection of a great part of it.Comment: To appear in the proceedings of the CAPP2000 Conference, Verbier,
Switzerland, July, 2000 (eds J. Garcia-Bellido, R. Durrer, and M.
Shaposhnikov
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