3,003 research outputs found
Pepino mosaic virus
Pepino mosaic virus (PepMV) is a relatively new plant virus that has become a signifi cant agronomical problem in a relatively short period of time. It is a member of the genus Potexvirus within the family Flexiviridae and is readily mechanically transmissible. It is capable of infecting tomato (Solanum lycopersicum) and other Solaneceous host plants. Since its description in 1980 from pepino plants (Solanum muricatum) collected in 1974 in Peru, the virus remained unknown for a long time until it manifested itself in commercial tomato crops in Europe in 1999. Since then the virus has been reported worldwide and the disease it causes has become important in commercial tomato production. Since 1999, new strains of the virus have been described which diff er from the original pepino isolate. The fast spread of the virus and the appearance of mixed infections with the new strains may play an important role in the increase of the agricultural importance of this viral diseas
How AGN feedback drives the size growth of the first quasars
Quasars at are powered by accretion onto supermassive black holes
with masses . Their rapid assembly
requires efficient gas inflow into the galactic nucleus, sustaining black hole
accretion at a rate close to the Eddington limit, but also high central star
formation rates. Using a set of cosmological 'zoom-in' hydrodynamic simulations
performed with the moving mesh code Arepo, we show that quasar host
galaxies develop extremely tightly bound stellar bulges with peak circular
velocities - km s and half-mass radii . Despite their high binding energy, we find that these compact bulges
expand at , with their half-mass radii reaching kpc
by . The circular velocity drops by factors from their
initial values to - km s at and the
stellar profile undergoes a cusp-core transformation. By tracking individual
stellar populations, we find that the gradual expansion of the stellar
component is mainly driven by fluctuations in the gravitational potential
induced by bursty AGN feedback. We also find that galaxy size growth and the
development of a cored stellar profile does not occur if AGN feedback is
ineffective. Our findings suggest that AGN-driven outflows may have profound
implications for the internal structure of massive galaxies, possibly
accounting for their size growth, the formation of cored ellipticals as well as
for the saturation of the - seen at high velocity
dispersions .Comment: 17 pages, 11 figures, 2 tables, accepted for publication in MNRA
The coset weight distributions of certain BCH codes and a family of curves
We study the distribution of the number of rational points in a family of
curves over a finite field of characteristic 2. This distribution determines
the coset weight distribution of a certain BCH code.Comment: Plain Tex, 15 pages; some numerical data adde
On the Existence of Supersingular Curves of Given Genus
We give a method to construct explicitly a supersingular curve of given genus
g in characteristic 2.Comment: 9 pages, plain TeX, UvA-report 94-1
Generalized Reed-Muller codes and curves with many points
The weight hierarchy of generalized Reed-Muller codes over arbitrary finite
fields was determined by Heijnen and Pellikaan. In this paper we produce curves
over finite fields with many points which are closely related to this weight
hierarchy.Comment: Plain Tex, 11 page
Quadratic forms, generalized Hamming weights of codes and curves with many points
We use the relations between quadrics, trace codes and algebraic curves to
construct algebraic curves over finite fields with many points and to compute
generalized Hamming weights of codes.Comment: 14 pages, Plain Te
Kummer Covers with Many Points
We give a method for constructing Kummer covers with many points over finite
fields.Comment: Plain Tex, 13 page
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