114 research outputs found
Effect of Phytosanitary Irradiation on the Quality of Two Varieties of Pummelos (\u3cem\u3eCitrus maxima\u3c/em\u3e (Burm.) Merr.)
Phytosanitary treatments prevent the introduction of pests such as fruit flies into pest free zones, and are often required for international trade. Irradiation is increasingly being considered as an alternative to cold and chemical phytosanitary treatments, such as methyl bromide. In this study, the effect of low dose gamma irradiation on the post-harvest quality of two varieties of pummelos (Citrus maxima (Burm.) Merr.), an emerging crop of interest in the US was evaluated. Two varieties of pummelos grown in California were irradiated at the phytosanitary target dose of 150 Gy and a higher dose of 1000 Gy to exaggerate and hence confirm the effects of treatment. The fruit was stored at 12 °C for 3 weeks and at 20 °C for the 4th week to reflect three weeks of sea shipment at the ideal temperature for storage of pummelos and an additional week of retail under ambient conditions. Neither irradiation nor storage affected juice content, organic acids, sugars, peel or pulp color and consumer sensory preference, although numerous volatiles increased in concentration as a result of irradiation treatment. Irradiation caused an immediate reduction in whole fruit and pulp firmness in âChandlerâ but not âSarawakâ pummelos at both 150 Gy and 1000 Gy. The quality of irradiated pummelos stored at refrigerated temperature for 3 weeks was similar to untreated pummelos, however, physical handling and exposure to higher temperature resulted in increased peel pitting of irradiated fruit compared to non-treated fruit. The results suggest that irradiation could serve as a potential phytosanitary treatment for Chandler and Sarawak pummelos, provided that the fruit is subjected to minimal handling and not temperature abused
Improved Simulation of Stabilizer Circuits
The Gottesman-Knill theorem says that a stabilizer circuit -- that is, a
quantum circuit consisting solely of CNOT, Hadamard, and phase gates -- can be
simulated efficiently on a classical computer. This paper improves that theorem
in several directions. First, by removing the need for Gaussian elimination, we
make the simulation algorithm much faster at the cost of a factor-2 increase in
the number of bits needed to represent a state. We have implemented the
improved algorithm in a freely-available program called CHP
(CNOT-Hadamard-Phase), which can handle thousands of qubits easily. Second, we
show that the problem of simulating stabilizer circuits is complete for the
classical complexity class ParityL, which means that stabilizer circuits are
probably not even universal for classical computation. Third, we give efficient
algorithms for computing the inner product between two stabilizer states,
putting any n-qubit stabilizer circuit into a "canonical form" that requires at
most O(n^2/log n) gates, and other useful tasks. Fourth, we extend our
simulation algorithm to circuits acting on mixed states, circuits containing a
limited number of non-stabilizer gates, and circuits acting on general
tensor-product initial states but containing only a limited number of
measurements.Comment: 15 pages. Final version with some minor updates and corrections.
Software at http://www.scottaaronson.com/ch
Large scale cosmic-ray anisotropy with KASCADE
The results of an analysis of the large scale anisotropy of cosmic rays in
the PeV range are presented. The Rayleigh formalism is applied to the right
ascension distribution of extensive air showers measured by the KASCADE
experiment.The data set contains about 10^8 extensive air showers in the energy
range from 0.7 to 6 PeV. No hints for anisotropy are visible in the right
ascension distributions in this energy range. This accounts for all showers as
well as for subsets containing showers induced by predominantly light
respectively heavy primary particles. Upper flux limits for Rayleigh amplitudes
are determined to be between 10^-3 at 0.7 PeV and 10^-2 at 6 PeV primary
energy.Comment: accepted by The Astrophysical Journa
Primary Proton Spectrum of Cosmic Rays measured with Single Hadrons
The flux of cosmic-ray induced single hadrons near sea level has been
measured with the large hadron calorimeter of the KASCADE experiment. The
measurement corroborates former results obtained with detectors of smaller size
if the enlarged veto of the 304 m^2 calorimeter surface is encounted for. The
program CORSIKA/QGSJET is used to compute the cosmic-ray flux above the
atmosphere. Between E_0=300 GeV and 1 PeV the primary proton spectrum can be
described with a power law parametrized as
dJ/dE_0=(0.15+-0.03)*E_0^{-2.78+-0.03} m^-2 s^-1 sr^-1 TeV^-1. In the TeV
region the proton flux compares well with the results from recent measurements
of direct experiments.Comment: 13 pages, accepted by Astrophysical Journa
Dissecting the knee - Air shower measurements with KASCADE
Recent results of the KASCADE air shower experiment are presented in order to
shed some light on the astrophysics of cosmic rays in the region of the knee in
the energy spectrum. The results include investigations of high-energy
interactions in the atmosphere, the analysis of the arrival directions of
cosmic rays, the determination of the mean logarithmic mass, and the unfolding
of energy spectra for elemental groups
KASCADE: Astrophysical results and tests of hadronic interaction models
KASCADE is a multi-detector setup to get redundant information on single air
shower basis. The information is used to perform multiparameter analyses to
solve the threefold problem of the reconstruction of (i)the unknown primary
energy, (ii) the primary mass, and (iii) to quantify the characteristics of the
hadronic interactions in the air-shower development. In this talk recent
results of the KASCADE data analyses are summarized concerning cosmic ray
anisotropy studies, determination of flux spectra for different primary mass
groups, and approaches to test hadronic interaction models. Neither large scale
anisotropies nor point sources were found in the KASCADE data set. The energy
spectra of the light element groups result in a knee-like bending and a
steepening above the knee. The topology of the individual knee positions shows
a dependency on the primary particle. Though no hadronic interaction model is
fully able to describe the multi-parameter data of KASCADE consistently, the
more recent models or improved versions of older models reproduce the data
better than few years ago.Comment: to appear in Nucl. Phys. B (Proc. Suppl.), Proc. of the XIII
ISVHECRI, Pylos 2004 - with a better quality of the figure
The KASCADE-Grande Experiment and the LOPES Project
KASCADE-Grande is the extension of the multi-detector setup KASCADE to cover
a primary cosmic ray energy range from 100 TeV to 1 EeV. The enlarged EAS
experiment provides comprehensive observations of cosmic rays in the energy
region around the knee. Grande is an array of 700 x 700 sqm equipped with 37
plastic scintillator stations sensitive to measure energy deposits and arrival
times of air shower particles. LOPES is a small radio antenna array to operate
in conjunction with KASCADE-Grande in order to calibrate the radio emission
from cosmic ray air showers. Status and capabilities of the KASCADE-Grande
experiment and the LOPES project are presented.Comment: To appear in Nuclear Physics B, Proceedings Supplements, as part of
the volume for the CRIS 2004, Cosmic Ray International Seminar: GZK and
Surrounding
Radio detection of cosmic ray air showers with LOPES
In the last few years, radio detection of cosmic ray air showers has
experienced a true renaissance, becoming manifest in a number of new
experiments and simulation efforts. In particular, the LOPES project has
successfully implemented modern interferometric methods to measure the radio
emission from extensive air showers. LOPES has confirmed that the emission is
coherent and of geomagnetic origin, as expected by the geosynchrotron
mechanism, and has demonstrated that a large scale application of the radio
technique has great potential to complement current measurements of ultra-high
energy cosmic rays. We describe the current status, most recent results and
open questions regarding radio detection of cosmic rays and give an overview of
ongoing research and development for an application of the radio technique in
the framework of the Pierre Auger Observatory.Comment: 8 pages; Proceedings of the CRIS2006 conference, Catania, Italy; to
be published in Nuclear Physics B, Proceedings Supplement
Radio emission of highly inclined cosmic ray air showers measured with LOPES
LOPES-10 (the first phase of LOPES, consisting of 10 antennas) detected a
significant number of cosmic ray air showers with a zenith angle larger than
50, and many of these have very high radio field strengths. The most
inclined event that has been detected with LOPES-10 has a zenith angle of
almost 80. This is proof that the new technique is also applicable
for cosmic ray air showers with high inclinations, which in the case that they
are initiated close to the ground, can be a signature of neutrino events.Our
results indicate that arrays of simple radio antennas can be used for the
detection of highly inclined air showers, which might be triggered by
neutrinos. In addition, we found that the radio pulse height (normalized with
the muon number) for highly inclined events increases with the geomagnetic
angle, which confirms the geomagnetic origin of radio emission in cosmic ray
air showers.Comment: A&A accepte
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