Lorentz Violation for Photons and Ultra-High Energy Cosmic Rays

Lorentz symmetry breaking at very high energies may lead to photon dispersion relations of the form omega^2=k^2+xi_n k^2(k/M_Pl)^n with new terms suppressed by a power n of the Planck mass M_Pl. We show that first and second order terms of size xi_1 > 10^(-14) and xi_2 < -10^(-6), respectively, would lead to a photon component in cosmic rays above 10^(19) eV that should already have been detected, if corresponding terms for electrons and positrons are significantly smaller. This suggests that Lorentz invariance breakings suppressed up to second order in the Planck scale are unlikely to be phenomenologically viable for photons.Comment: 4 revtex pages, 3 postscript figures included, version published in PR

Purification and characterization of digestive amylase from the tasar silkworm, Antheraea mylitta (Lepidoptera: Saturniidae)

Digestive amylase was purified from larvae of Indian tasar silkworm, Antheraea mylitta using ammonium sulphate precipitation, glycogen complex precipitation and gel filtration chromatography. Specific activity increased from 0.673 AU/mg in the crude digestive juice to 94.80 AU/mg in the final purified sample. Activity of the purified enzyme was 15-fold less than that of the digestive amylase of silkworm. Bombyx mori. The zymogram pattern of the purified amylase was similar to that of crude digestive juice on 7.5% native PAGE. The purified enzyme exhibited five bands on native PAGE. IEF of the purified enzyme also revealed five bands with pls of 6.5, 6.15, 5.9, 5.8 and 4.7, respectively. The purified enzyme is a single polypeptide chain with a Mr of 58 kDa. The amylase is most active at pH 9.5 and is a Ca2+ dependent endoenzyme which hydrolyses starch into maltose, maltotriose and maltotetrose and hence behaves as an &#945;-amylase (EC 3.2.1.1). The enzyme was unaffected by the presence or absence of CI-, with Km for soluble starch of 0.113%

Stepping up food production in Kerala-Problems, Perspectives and Strategies

A disturbing factor of the agricultural scenario in Kerala is that in spite of significant developments in agricultural technology, the productivity of rice has remained stagnant during the past over two decades. The annual rice production in the State has been stagnant, at about 1.3 million tonnes for nearly a decade' as against the present requirement of 2.8 million tonnes per year, while the population bas been growing at an annual rate of 1.79 per cent, resulting in a progressively widening gap between internal production and requirements

Cosmological Origin of the Stellar Velocity Dispersions in Massive Early-Type Galaxies

We show that the observed upper bound on the line-of-sight velocity dispersion of the stars in an early-type galaxy, sigma<400km/s, may have a simple dynamical origin within the LCDM cosmological model, under two main hypotheses. The first is that most of the stars now in the luminous parts of a giant elliptical formed at redshift z>6. Subsequently, the stars behaved dynamically just as an additional component of the dark matter. The second hypothesis is that the mass distribution characteristic of a newly formed dark matter halo forgets such details of the initial conditions as the stellar "collisionless matter" that was added to the dense parts of earlier generations of halos. We also assume that the stellar velocity dispersion does not evolve much at z<6, because a massive host halo grows mainly by the addition of material at large radii well away from the stellar core of the galaxy. These assumptions lead to a predicted number density of ellipticals as a function of stellar velocity dispersion that is in promising agreement with the Sloan Digital Sky Survey data.Comment: ApJ, in press (2003); matches published versio

Casimir interactions in Ising strips with boundary fields: exact results

An exact statistical mechanical derivation is given of the critical Casimir forces for Ising strips with arbitrary surface fields applied to edges. Our results show that the strength as well as the sign of the force can be controled by varying the temperature or the fields. An interpretation of the results is given in terms of a linked cluster expansion. This suggests a systematic approach for deriving the critical Casimir force which can be used in more general models.Comment: 10 pages, 4 figure

Observational evidence of spin-induced precession in active galactic nuclei

We show that it is possible to explain the physical origin of jet precession in active galactic nuclei (AGNs) through the misalignment between the rotation axes of the accretion disk and of the Kerr black hole. We apply this scenario to quasars, Seyfert galaxies and also to the Galactic Center black hole Sgr A*, for which signatures of either jet or disk precession have been found. The formalism adopted is parameterized by the ratio of the precession period to the black hole mass and can be used to put constraints to the physical properties of the accretion disk as well as to the black hole spin in those systems.Comment: 10 pages, 1 figure, accepted for publication in ApJ Letter