236 research outputs found
Establishing a More Effective Phytosanitary Regulatory System: A Zambian Case Study
Zambia, a landlocked country importing plants and plant products is vulnerable to the trading risks associated with agricultural products. By virtue of its geographical location, traded plants and plant products also transit through the country. Importations and the transit of plants and plant products have the potential for introducing plant pests that affect agricultural production and limit access to export markets. Globally, government institutions, especially National Plant Protection Organizations (NPPOs), play an important role in preventing the introductions of plant pests resulting from international trade. For this reason, Zambia requires an effective phytosanitary regulatory system. One of the essential components of such a system is an internationally acceptable Pest Risk Analysis (PRA) process. In this context, PRA is a systematic evaluation of the risks associated with the movement of plants and plant products in international trade. It is the basis on which scientifically based phytosanitary measures aimed at preventing the introduction of quarantine pests are developed. This paper highlights the essential components of a PRA process and describes a critical assessment of Zambiaâs phytosanitary system and its capacity to undertake PRAs. Keywords: National Plant Protection Organization, quarantine pests, phytosanitary measures, Pest Risk Analysis, trad
Oriented rotational wave-packet dynamics studies via high harmonic generation
We produce oriented rotational wave packets in CO and measure their
characteristics via high harmonic generation. The wavepacket is created using
an intense, femtosecond laser pulse and its second harmonic. A delayed 800 nm
pulse probes the wave packet, generating even-order high harmonics that arise
from the broken symmetry induced by the orientation dynamics. The even-order
harmonic radiation that we measure appears on a zero background, enabling us to
accurately follow the temporal evolution of the wave packet. Our measurements
reveal that, for the conditions optimum for harmonic generation, the
orientation is produced by preferential ionization which depletes the sample of
molecules of one orientation
Optical properties of silicon-implanted polycrystalline diamond membranes
We investigate the optical properties of polycrystalline diamond membranes
containing silicon-vacancy (SiV) color centers in combination with other
nano-analytical techniques. We analyze the correlation between the Raman
signal, the SiV emission, and the background luminescence in the crystalline
grains and in the grain boundaries, identifying conditions for the
addressability of single SiV centers. Moreover, we perform a scanning
transmission electron microscopy (STEM) analysis, which associates the
microscopic structure of the membranes and the evolution of the diamond crystal
along the growth direction with the photoluminescence properties, as well as a
time-of-flight secondary ion mass spectrometry (ToF-SIMS) to address the
distribution of silicon in implanted and un-implanted membranes. The results of
the STEM and ToF-SIMS studies are consistent with the outcome of the optical
measurements and provide useful insight into the preparation of polycrystalline
samples for quantum nano-optics.Comment: 21 pages, 8 figure
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the
distribution of arrival directions of the cosmic rays with energies
eV. These show a correlation with the distribution
of nearby extragalactic objects, including an apparent excess around the
direction of Centaurus A. If the particles responsible for these excesses at
are heavy nuclei with charge , the proton component of the
sources should lead to excesses in the same regions at energies . We here
report the lack of anisotropies in these directions at energies above
(for illustrative values of ). If the anisotropies
above are due to nuclei with charge , and under reasonable
assumptions about the acceleration process, these observations imply stringent
constraints on the allowed proton fraction at the lower energies
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
Effect of COMBinAtion therapy with remote ischemic conditioning and exenatide on the Myocardial Infarct size: a two-by-two factorial randomized trial (COMBAT-MI)
Remote ischemic conditioning (RIC) and the GLP-1 analog exenatide activate different cardioprotective pathways and may have additive effects on infarct size (IS). Here, we aimed to assess the efficacy of RIC as compared with sham procedure, and of exenatide, as compared with placebo, and the interaction between both, to reduce IS in humans. We designed a two-by-two factorial, randomized controlled, blinded, multicenter, clinical trial. Patients with ST-segment elevation myocardial infarction receiving primary percutaneous coronary intervention (PPCI) within 6 h of symptoms were randomized to RIC or sham procedure and exenatide or matching placebo. The primary outcome was IS measured by late gadolinium enhancement in cardiac magnetic resonance performed 3â7 days after PPCI. The secondary outcomes were myocardial salvage index, transmurality index, left ventricular ejection fraction and relative microvascular obstruction volume. A total of 378 patients were randomly allocated, and after applying exclusion criteria, 222 patients were available for analysis. There were no significant interactions between the two randomization factors on the primary or secondary outcomes. IS was similar between groups for the RIC (24â±â11.8% in the RIC group vs 23.7â±â10.9% in the sham group, Pâ=â0.827) and the exenatide hypotheses (25.1â±â11.5% in the exenatide group vs 22.5â±â10.9% in the placebo group, Pâ=â0.092). There were no effects with either RIC or exenatide on the secondary outcomes. Unexpected adverse events or side effects of RIC and exenatide were not observed. In conclusion, neither RIC nor exenatide, or its combination, were able to reduce IS in STEMI patients when administered as an adjunct to PPCI
Lead isotopic evidence for synextensional lithospheric ductile flow in the Colorado River extensional corridor, western United States
This is the published version. Copyright 1998 American Geophysical Union. All Rights Reserved.Temporal changes in the Pb isotopic compositions of Miocene lavas erupted in the northern Colorado River extensional corridor suggest that lithospheric mantle and middle to deep crust migrated from beneath the Colorado Plateau into the corridor during extension. Basaltic to rhyolitic lavas erupted in the extensional corridor prior to 12.2 Ma have Pb isotopic values that are similar to those of Tertiary to Quaternary lavas erupted through Proterozoic Mojave crust, which comprises surface exposures of basement in the corridor and much of the extended territory to the west. In contrast, most post-12.2 Ma lavas from the same region have Pb isotopic compositions similar to those of lavas erupted through Arizona crust, which forms the basement of the Colorado Plateau. The changes in isotopic compositions of the basaltic lavas, and perhaps a portion of the changes in isotopic compositions of silicic lavas, are attributed to a change in the composition of the mantle source. However, the 206Pb/204Pb ratios for lavas erupted before and after 12.2 Ma in the corridor decrease with decreasing MgO concentrations, suggesting that the Pb isotopic compositions of crustal assimilants changed at about the same time as the composition of the mantle. In the area of the Black Mountains accommodation zone, the surface boundary between the Arizona and Mojave crustal provinces lies a minimum of 60â80 km to the east of the westernmost lava with an Arizona Pb isotopic signature. This distance cannot be accounted for by displacements along nearby major faults, suggesting that middle to deep Arizona crust flowed a significant distance to the west during extension
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