51,676 research outputs found
Enhancing the cosmic-ray mass sensitivity of air-shower arrays by combining radio and muon detectors
The muonic and electromagnetic components of air showers are sensitive to the
mass of the primary cosmic particle. The sizes of the components can be
measured with particle detectors on ground, and the electromagnetic component
in addition indirectly via its radio emission in the atmosphere. The
electromagnetic particles do not reach the ground for very inclined showers. On
the contrary, the atmosphere is transparent for the radio emission and its
footprint on ground increases with the zenith angle. Therefore, the radio
technique offers a reliable detection over the full range of zenith angles, and
in particular for inclined showers. In this work, the mass sensitivity of a
combination of the radio emission with the muons is investigated in a case
study for the site of the Pierre Auger Observatory using CORSIKA Monte Carlo
simulations of showers in the EeV energy range. It is shown, that the
radio-muon combination features superior mass separation power in particular
for inclined showers, when compared to established mass observables such as a
combination of muons and electrons or the shower maximum Xmax. Accurate
measurements of the energy-dependent mass composition of ultra-high energy
cosmic rays are essential to understand their still unknown origin. Thus, the
combination of muon and radio detectors can enhance the scientific performance
of future air-shower arrays and offers a promising upgrade option for existing
arrays
Electrolytically regenerative hydrogen-oxygen fuel cell Patent
Electrolytically regenerative hydrogen-oxygen fuel cell
A Survey of Metal Lines at High-redshift (I) : SDSS Absorption Line Studies - The Methodology and First Search Results for OVI
We report the results of a systematic search for signatures of metal lines in
quasar spectra of the Sloan Digital Sky Survey (SDSS) Data Release 3(DR3),
focusing on finding intervening absorbers via detection of their OVI doublet.
Here we present the search algorithm, and criteria for distinguishing
candidates from spurious Lyman {} forest lines. In addition, we compare
our findings with simulations of the Lyman {} forest in order to
estimate the detectability of OVI doublets over various redshift intervals. We
have obtained a sample of 1756 OVI doublet candidates with rest-frame
equivalent width > 0.05 \AA{} in 855 AGN spectra (out of 3702 objects with
redshifts in the accessible range for OVI detection). This sample is further
subdivided into 3 groups according to the likelihood of being real and the
potential for follow-up observation of the candidate. The group with the
cleanest and most secure candidates is comprised of 145 candidates. 69 of these
reside at a velocity separation > 5000 km/s from the QSO, and can therefore be
classified tentatively as intervening absorbers. Most of these absorbers have
not been picked up by earlier, automated QSO absorption line detection
algorithms. This sample increases the number of known OVI absorbers at
redshifts beyond z$_{abs} > 2.7 substantially.Comment: 41 pages, 10 figures, 2 tables, accepted by AJ. This is a
substantially altered version, including an appendix with details on the
validity of the search algorithm on one pixel rather than binning. Also note
that M. Pieri was added as autho
Electron-Phonon Interaction in Embedded Semiconductor Nanostructures
The modification of acoustic phonons in semiconductor nanostructures embedded
in a host crystal is investigated including corrections due to strain within
continuum elasticity theory. Effective elastic constants are calculated
employing {\em ab initio} density functional theory. For a spherical InAs
quantum dot embedded in GaAs barrier material, the electron-phonon coupling is
calculated. Its strength is shown to be suppressed compared to the assumption
of bulk phonons
The POOL Data Storage, Cache and Conversion Mechanism
The POOL data storage mechanism is intended to satisfy the needs of the LHC
experiments to store and analyze the data from the detector response of
particle collisions at the LHC proton-proton collider. Both the data rate and
the data volumes will largely differ from the past experience. The POOL data
storage mechanism is intended to be able to cope with the experiment's
requirements applying a flexible multi technology data persistency mechanism.
The developed technology independent approach is flexible enough to adopt new
technologies, take advantage of existing schema evolution mechanisms and allows
users to access data in a technology independent way. The framework consists of
several components, which can be individually adopted and integrated into
existing experiment frameworks.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 5 pages, PDF, 6 figures. PSN MOKT00
FIELD TRIALS AS AN EXTENSION TECHNIQUE: THE CASE OF SWAZILAND
One potentially serious problem in evaluating the effectiveness of extension programs is that participants are not picked at random. Self-selection can be a problem, and it can be compounded if extension officials concentrate on the most progressive farms. This study explores the relationships between adoption of maize high-yielding varieties (HYVs) and participation in field trials intended to foster HYV usage, drawing on data from Swaziland. Results indicate that it is impossible to say if field trials had any effect on adoption. Participating farms used more HYVs, but this could have been due to self-selection or the government's selection process.Teaching/Communication/Extension/Profession,
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