974 research outputs found
Susceptibility of South African native conifers to the pitch canker pathogen, Fusarium circinatum
AbstractFusarium circinatum is an economically important pathogen of Pinus species, which also occurs on Douglas fir (Pseudotsuga menzeisii). It causes pitch canker of mature trees and root and collar rot of seedlings and cuttings. In 2007, pitch canker was observed on Pinus radiata in the Western Cape and this was the first outbreak of this disease in South Africa. The Cape flora in this area includes native coniferous species of Podocarpus and Widdringtonia. In this study, seedlings of P. latifolia, P. elongatus, P. henkelii, W. schwartzii, W. cederbergensis and W. nodiflora were inoculated with a virulent isolate of F. circinatum, to assess their susceptibility. Six weeks after inoculation, there was no lesion development in any of the species inoculated. Pinus patula seedlings used as a positive control were severely affected. Results of this study show that species of Podocarpus and Widdringtonia, native to the Western Cape, are not threatened by the pitch canker fungus
Cosmic Ray Spectra in Nambu-Goldstone Dark Matter Models
We discuss the cosmic ray spectra in annihilating/decaying Nambu-Goldstone
dark matter models. The recent observed positron/electron excesses at PAMELA
and Fermi experiments are well fitted by the dark matter with a mass of 3TeV
for the annihilating model, while with a mass of 6 TeV for the decaying model.
We also show that the Nambu-Goldstone dark matter models predict a distinctive
gamma-ray spectrum in a certain parameter space.Comment: 16 pages, 4 figure
GALPROP WebRun: an internet-based service for calculating galactic cosmic ray propagation and associated photon emissions
GALPROP is a numerical code for calculating the galactic propagation of
relativistic charged particles and the diffuse emissions produced during their
propagation. The code incorporates as much realistic astrophysical input as
possible together with latest theoretical developments and has become a de
facto standard in astrophysics of cosmic rays. We present GALPROP WebRun, a
service to the scientific community enabling easy use of the freely available
GALPROP code via web browsers. In addition, we introduce the latest GALPROP
version 54, available through this service.Comment: Accepted for publication in Computer Physics Communications. Version
2 includes improvements suggested by the referee. Metadata completed in
version 3 (no changes to the manuscript
Innovative Education in Agroecology: Experiential Learning for a Sustainable Agriculture
The transdisciplinary field of agroecology provides a platform for experiential learning based on an expanded vision of research on sustainable farming and food systems and the application of results in creating effective learning landscapes for students. With increased recognition of limitations of fossil fuels, fresh water, and available farmland, educators are changing focus from strategies to reach maximum yields to those that feature resource use efficiency and resilience of production systems in a less benign climate. To help students deal with complexity and uncertainty and a wide range of biological and social dimensions of the food challenge, a whole-systems approach that involves life-cycle analysis and consideration of long-term impacts of systems is essential. Seven educational case studies in the Nordic Region and the U.S. Midwest demonstrate how educators can incorporate theory of the ecology of food systems with the action learning component needed to develop student potentials to create responsible change in society. New roles of agroecology instructors and students are described as they pursue a co-learning strategy to develop and apply technology to assure the productivity and security of future food system
Robust implications on Dark Matter from the first FERMI sky gamma map
We derive robust model-independent bounds on DM annihilations and decays from
the first year of FERMI gamma-ray observations of the whole sky. These bounds
only have a mild dependence on the DM density profile and allow the following
DM interpretations of the PAMELA and FERMI electron/positron excesses: primary
channels mu+ mu-, mu+ mu-mu+mu- or e+ e- e+ e-. An isothermal-like density
profile is needed for annihilating DM. In all such cases, FERMI gamma spectra
must contain a significant DM component, that may be probed in the future.Comment: 16 pages, 8 figures. Final versio
The Offline Software Framework of the Pierre Auger Observatory
To be published in the ProceedingsInternational audienceThe Pierre Auger Observatory is designed to unveil the nature and the origins of the highest energy cosmic rays. The large and geographically dispersed collaboration of physicists and the wide-ranging collection of simulation and reconstruction tasks pose some special challenges for the offline analysis software. We have designed and implemented a general purpose framework which allows collaborators to contribute algorithms and sequencing instructions to build up the variety of applications they require. The framework includes machinery to manage these user codes, to organize the abundance of user-contributed configuration files, to facilitate multi-format file handling, and to provide access to event and time-dependent detector information which can reside in various data sources. A number of utilities are also provided, including a novel geometry package which allows manipulation of abstract geometrical objects independent of coordinate system choice. The framework is implemented in C++, and takes advantage of object oriented design and common open source tools, while keeping the user side simple enough for C++ novices to learn in a reasonable time. The distribution system incorporates unit and acceptance testing in order to support rapid development of both the core framework and contributed user code
Dirac gaugino as leptophilic dark matter
We investigate the leptophilic properties of Dirac gauginos in an
R--symmetric N=2 supersymmetric model with extended gauge and Higgs sectors.
The annihilation of Dirac gauginos to leptons requires no chirality flip in the
final states so that it is not suppressed as in the Majorana case. This implies
that it can be sizable enough to explain the positron excess observed by the
PAMELA experiment with moderate or no boost factors. When squark masses are
heavy, the annihilation of Dirac gauginos to hadrons is controlled by their
Higgsino fraction and is driven by the and final states.
Moreover, at variance with the Majorana case, Dirac gauginos with a
non-vanishing higgsino fraction can also have a vector coupling with the
gauge boson leading to a sizable spin--independent scattering cross section off
nuclei. Saturating the current antiproton limit, we show that Dirac gauginos
can leave a signal in direct detection experiments at the level of the
sensitivity of dark matter searches at present and in the near future.Comment: 24 pages, 10 figures, typos corrected, final version published on
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The Gamma-Ray Albedo of the Moon
We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makes it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA
Level Spacing Distribution of Critical Random Matrix Ensembles
We consider unitary invariant random matrix ensembles which obey spectral
statistics different from the Wigner-Dyson, including unitary ensembles with
slowly (~(log x)^2) growing potentials and the finite-temperature fermi gas
model. If the deformation parameters in these matrix ensembles are small, the
asymptotically translational-invariant region in the spectral bulk is
universally governed by a one-parameter generalization of the sine kernel. We
provide an analytic expression for the distribution of the eigenvalue spacings
of this universal asymptotic kernel, which is a hybrid of the Wigner-Dyson and
the Poisson distributions, by determining the Fredholm determinant of the
universal kernel in terms of a Painleve VI transcendental function.Comment: 5 pages, 1 figure, REVTeX; restriction on the parameter stressed,
figure replaced, refs added (v2); typos (factors of pi) in (35), (36)
corrected (v3); minor changes incl. title, version to appear in Phys.Rev.E
(v4
Scaling Analysis of Fluctuating Strength Function
We propose a new method to analyze fluctuations in the strength function
phenomena in highly excited nuclei. Extending the method of multifractal
analysis to the cases where the strength fluctuations do not obey power scaling
laws, we introduce a new measure of fluctuation, called the local scaling
dimension, which characterizes scaling behavior of the strength fluctuation as
a function of energy bin width subdividing the strength function. We discuss
properties of the new measure by applying it to a model system which simulates
the doorway damping mechanism of giant resonances. It is found that the local
scaling dimension characterizes well fluctuations and their energy scales of
fine structures in the strength function associated with the damped collective
motions.Comment: 22 pages with 9 figures; submitted to Phys. Rev.
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