6,093 research outputs found
Absorption of High Energy Gamma-Rays by Low Energy Intergalactic Photons
Following our previously proposed technique, we have used the recent
gamma-ray observations of Mrk 421 to place theoretically significant
constraints on and possible estimates of the intergalactic infrared radiation
field (IIRF) which are consistent with normal galactic IR production by stars
and dust and rule out exotic mechanisms proposed to produce a larger IIRF.
Using models for the low energy intergalactic photon spectrum from microwave to
UV energies, we calculate the opacity of inter- galactic space to gamma-rays as
a function of energy and redshift. These calculations indicate that the GeV
gamma-ray burst recently observed by the EGRET experiment on CGRO originates at
a redshift less than approximately 1.5.Comment: 12 pg., uuencoded, Z-compressed ps file (includes figures), To be
published in Space Sci. Re
Flavor decomposition of the elastic nucleon electromagnetic form factors
The u- and d-quark contributions to the elastic nucleon electromagnetic form
factors have been determined using experimental data on GEn, GMn, GpE, and GpM.
Such a flavor separation of the form factors became possible up to 3.4 GeV2
with recent data on GEn from Hall A at JLab. At a negative four-momentum
transfer squared Q2 above 1 GeV2, for both the u- and d-quark components, the
ratio of the Pauli form factor to the Dirac form factor, F2/F1, was found to be
almost constant, and for each of F2 and F1 individually, the d-quark portions
of both form factors drop continuously with increasing Q2.Comment: 4 pages, 3 figure
HESS J1507-622: an unique unidentified source off the Galactic Plane
Galactic very high energy (VHE, > 100 GeV) gamma ray sources in the inner
Galaxy H.E.S.S. survey tend to cluster within 1 degree in latitude around the
Galactic plane. HESS J1507-622 instead is unique, since it is located at
latitude of ~3.5 degrees. HESS J1507-622 is slightly extended over the PSF of
the instrument and hence its Galactic origin is clear. The search for
counterparts in other wavelength regimes (radio, infrared and X-rays) failed to
show any plausible counterparts; and given its position off the Galactic plane
and hence the absorption almost one order of magnitude lower, it is very
surprising to not see any counterparts especially at X-rays wavelengths (by
ROSAT, XMM Newton and Chandra). Its latitude implies that it is either rather
close, within about 1 kpc, or is located well off the Galactic plane. And also
the models reflect the uniqueness of this object: a leptonic PWN scenario would
place this source due to its quite small extension to multi-kpc distance
whereas a hadronic scenario would preferentially locate this object at
distances of < 1 kpc where the density of target material is higher
A holistic approach to enhance the use of neglected and underutilized species: the case of Andean grains in Bolivia and Peru
The IFAD-NUS project, implemented over the course of a decade in two phases, represents the first UN-supported global effort on neglected and underutilized species (NUS). This initiative, deployed and tested a holistic and innovative value chain framework using multi-stakeholder, participatory, inter-disciplinary, pro-poor gender- and nutrition-sensitive approaches. The project has been linking aspects often dealt with separately by R&D, such as genetic diversity, selection, cultivation, harvest, value addition, marketing, and final use, with the goal to contribute to conservation, better incomes, and improved nutrition and strengthened livelihood resilience. The project contributed to the greater conservation of Andean grains and their associated indigenous knowledge, through promoting wider use of their diversity by value chain actors, adoption of best cultivation practices, development of improved varieties, dissemination of high quality seed, and capacity development. Reduced drudgery in harvest and postharvest operations, and increased food safety were achieved through technological innovations. Development of innovative food products and inclusion of Andean grains in school meal programs is projected to have had a positive nutrition outcome for targeted communities. Increased income was recorded for all value chain actors, along with strengthened networking skills and self-reliance in marketing. The holistic approach taken in this study is advocated as an effective strategy to enhance the use of other neglected and underutilized species for conservation and livelihood benefits
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