7,424 research outputs found
TeV gamma rays and cosmic rays from the nucleus of M87, a mis-aligned BL Lac object
The unresolved nuclear region of M87 emits strong non-thermal emission from
radio to X-rays. Assuming this emission to originate in the pc scale jet
aligned at to the line of sight, we interpret this
emission in the context of the Synchrotron Proton Blazar (SPB) model. We find
the observed nuclear jet emission to be consistent with M87 being a mis-aligned
BL Lac Object and predict gamma-ray emission extending up to at least 100 GeV
at a level easily detectable by GLAST and MAGIC, and possibly by VERITAS
depending on whether it is high-frequency or low-frequency peaked. Predicted
neutrino emission is below the sensitivity of existing and planned neutrino
telescopes. Ultra-high energy neutrons produced in pion photoproduction
interactions decay into protons after escaping from the host galaxy. Because
energetic protons are deflected by the intergalactic magnetic field, the
protons from the decay of neutrons emitted in all directions, including along
the jet axis where the Doppler factor and hence emitted neutron energies are
higher, can contribute to the observed ultra-high energy cosmic rays. We
consider the propagation of these cosmic ray protons to Earth and conclude that
M87 could account for the observed flux if the extragalactic magnetic field
topology were favourable.Comment: 17 pages, 6 figures. 3 additional references plus minor changes,
acctepted for publication in Astroparticle Physic
Identification of zeta-carotene desaturase genes from durum wheat
Non-Peer ReviewedYellow pigment is an important quality trait in durum wheat (Triticum turgidum L. var durum). Few genes within the pathway responsible for carotenoid biosynthesis have yet to been identified in durum wheat. Zeta-carotene desaturase (ZDS) is an enzyme involved in carotenoid biosynthesis, and variation in the gene(s) coding for ZDS may partially explain the variation observed in endosperm color among durum wheat cultivars. For this study, a PCR strategy was used to clone and sequence greater than 1200 bp of the Zds genes from durum cultivars Kofa (high pigment) and W9262-D063 (medium pigment). Comparison of partial nucleotide sequences indicated the presence of four Zds genes which we temporarily designated as tdZds1, tdZds2, tdZds3, and tdZds4. Since durum wheat is a tetraploid, the presence of four genes suggests that the Zds gene may in fact be duplicated in the durum wheat genome, with two sets of homeologous genes. However, we have only obtained single clones of Zds2 and Zds4 from each of the two parents, and these results will need to be confirmed. However, we are currently in the process of mapping Zds1 and Zds3 to determine their role in the expression of yellow pigment concentration in durum wheat
Race Cartels: How Constructor Collaboration Is Curbing Innovation in Formula 1
Formula 1 is in the midst of a copycat scandal: technology has made it possible for teams to reverse engineer clones of competitorsâ race cars. This is a less than ideal state of affairs for the championship series, which prides itself on being the pinnacle of motorsport and automotive innovation, thanks in large part to the carsâ rapid rate of technological advancement. In order to address this problem, the FĂ©dĂ©ration Internationale de lâAutomobile (FIA), Formula 1âs governing body, must increase independent innovation efforts by amending the technical regulations to restrict the extent of presently allowed inter-team collaboration. Worried that the sport was becoming a âcopying championship,â the FIA adopted new measures that ban extreme reverse engineering methods. Because these new FIA regulations do not limit the degree of coordinated conduct between teams, this approach will likely fail to remedy the sportâs copying problem because team plagiarism is an anticompetitive side effect of this collusive behavior.
The FIA addresses the copying problem as one of trade secret misappropriation. By contrast, this Note approaches the issue as one of unregulated anticompetitive conduct. Analyzing the technical partnerships in Formula 1 under antitrust law elucidates their harmful effects on the racing series. This Note urges the FIA to adopt measures that limit Formula 1 teamsâ ability to collaborate, before the âA-B teamâ phenomenon further diminishes the sportâs innovation efforts
Notes on the Diatom Cylindrotheca gracilis (Breh. ex Kutz) Grun: Its Ecology and Distribution
The diatom Cylindrotheca gracilis (Breb. ex Kutz) Grun., considered by some as a Brackish water species, was found as a massive growth in isolated pools along Dugout Creek, Dickinson County, Iowa. Chemical analyses show the water to be high in S04, Mg., Ca., and low in Cl ions. Comparative data from other waters in the United States containing this species shows similar pattern of high conductivity suggesting that factors other than chlorides might be more critical for growth. United States distribution for this diatom includes: Maryland (brackish water), Ohio (fresh water) and Iowa (fresh water)
An explicit numerical model to simulate upwelling events
A three-dimensional numerical model for upwelling has been developed and tested under various boundary conditions. Gridsize and bottom topography are variable; the driving force is windstress. A version o f the model was applied to data from the â Upwelling 75â experim ent. Certain wind-induced events observed in the data are reproduced reasonably well, although wind input is done by m eans of linear approx imation. Typical upwelling conditions can be achieved and the influence of bottom topography can be shown
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Upper ocean climate of the Eastern Mediterranean Sea during the Holocene Insolation Maximum â a model study
ine thousand years ago (9 ka BP), the Northern Hemisphere experienced enhanced seasonality caused by an orbital configuration close to the minimum of the precession index. To assess the impact of this "Holocene Insolation Maximum" (HIM) on the Mediterranean Sea, we use a regional ocean general circulation model forced by atmospheric input derived from global simulations. A stronger seasonal cycle is simulated by the model, which shows a relatively homogeneous winter cooling and a summer warming with well-defined spatial patterns, in particular, a subsurface warming in the Cretan and western Levantine areas.
The comparison between the SST simulated for the HIM and a reconstruction from planktonic foraminifera transfer functions shows a poor agreement, especially for summer, when the vertical temperature gradient is strong. As a novel approach, we propose a reinterpretation of the reconstruction, to consider the conditions throughout the upper water column rather than at a single depth. We claim that such a depth-integrated approach is more adequate for surface temperature comparison purposes in a situation where the upper ocean structure in the past was different from the present-day. In this case, the depth-integrated interpretation of the proxy data strongly improves the agreement between modelled and reconstructed temperature signal with the subsurface summer warming being recorded by both model and proxies, with a small shift to the south in the model results.
The mechanisms responsible for the peculiar subsurface pattern are found to be a combination of enhanced downwelling and wind mixing due to strengthened Etesian winds, and enhanced thermal forcing due to the stronger summer insolation in the Northern Hemisphere. Together, these processes induce a stronger heat transfer from the surface to the subsurface during late summer in the western Levantine; this leads to an enhanced heat piracy in this region, a process never identified before, but potentially characteristic of time slices with enhanced insolation
AVIRIS ground data-processing system
The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has been under development at JPL for the past four years. During this time, a dedicated ground data-processing system has been designed and implemented to store and process the large amounts of data expected. This paper reviews the objectives of this ground data-processing system and describes the hardware. An outline of the data flow through the system is given, and the software and incorporated algorithms developed specifically for the systematic processing of AVIRIS data are described
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