Response to sub-threshold stimulus is enhanced by spatially heterogeneous activity

Sub-threshold stimuli cannot initiate excitations in active media, but surprisingly as we show in this paper, they can alter the time-evolution of spatially heterogeneous activity by modifying the recovery dynamics. This results in significant reduction of waveback velocity which may lead to spatial coherence, terminating all activity in the medium including spatiotemporal chaos. We analytically derive model-independent conditions for which such behavior can be observed.Comment: 5 pages, 5 figure

Isospectrality in Chaotic Billiards

We consider a modification of isospectral cavities whereby the classical dynamics changes from pseudointegrable to chaotic. We construct an example where we can prove that isospectrality is retained. We then demonstrate this explicitly in microwave resonators.Comment: 5 pages, 7 figure

Stellar orbits in triaxial clusters around black holes in galactic nuclei

We investigate the orbital structure of a model triaxial star cluster, centered around a supermassive black hole (BH), appropriate to galactic nuclei. Sridhar and Touma (1999) proved that the presence of the BH enforces some regularity in the dynamics within the radius of influence of the BH. We employ their averaging method to reduce the degrees of freedom from three to two. Numerical orbit integrations, together with Poincar\'e surfaces of section allow us to draw a global portrait of the orbital structure; in our calculations we employ a model cluster potential that is triaxial and harmonic. The averaged dynamics of the axisymmetric case is integrable, and we present a detailed comparison of orbits in oblate and prolate axisymmetric potentials. Both cases support resonant orbits with fixed values of eccentricity, inclination, and periapse, whose lines of nodes rotates steadily. We then systematically explore significantly triaxial potentials, possessing small oblateness, or prolateness. Resonant orbits and their families are studied both numerically, and through secular perturbation theory. Chaos appears to be suppressed for all the cases we studied, and we obtain effective third integrals. Some of the orbits appear to reinforce the shape of the potential; we provide phase space, as well as real space portraits of these orbits. A particularly promising resonant orbit exists in highly prolate, triaxial potentials

Probiotic effects of lactic acid bacteria against Vibrio alginolyticus in Penaeus (Fenneropenaeus) indicus (H. Milne Edwards)

Cell free extracts of four strains of Lactic acid bacteria (LAB) viz. Lactobacillus. acidophilus, Streptococcus.cremoris, Lactobacillus bulgaricus –56 and Lactobacillus bulgaricus –57 inhibited growth of Vibrio alginolyticus in nutrient broth. The antagonism of LAB to Vibrio alginolyticus was further confirmed by streak plating wherein suppression of growth of Vibrio was obtained. Juveniles of Penaeus indicus (average weight 0.985 ± 0.1 g) on administering orally a moist feed base containing 5 × 106 cells·g of the four LAB probionts for a period of four weeks showed better survival (56 to 72%) when challenged with V. alginolyticus by intra-muscular injection of 0.1 ml containing 3 × 109 cells·ml. Animals maintained on a diet devoid of bacterial biomass exhibited 80% mortality

Correlations due to localization in quantum eigenfunctions of disordered microwave cavities

Non-universal correlations due to localization are observed in statistical properties of experimental eigenfunctions of quantum chaotic and disordered microwave cavities. Varying energy {E} and mean free path {l} enable us to experimentally tune from localized to delocalized states. Large level-to-level Inverse Participation Ratio (IPR I_{2}) fluctuations are observed for the disordered billiards, whose distribution is strongly asymmetric about . The density auto-correlations of eigenfunctions are shown to decay exponentially and the decay lengths are experimentally determined. All the results are quantitatively consistent with calculations based upon nonlinear sigma-models.Comment: 4 pages, LaTex, 5 .jpg figures. This paper with 5 embedded postscript figures available (PS,PDF) at http://sagar.physics.neu.edu/preprints

NLO-QCD Corrections to Dilepton Production in the Randall-Sundrum Model

The dilepton production process at hadron colliders in the Randall-Sundrum (RS) model is studied at next-to-leading order in QCD. The NLO-QCD corrections have been computed for the virtual graviton exchange process in the RS model, in addition to the usual gamma, Z-mediated processes of standard Drell-Yan. K-factors for the cross-sections at the LHC and Tevatron for differential in the invariant mass, Q, and the rapidity, Y, of the lepton pair are presented. We find the K-factors are large over substantial regions of the phase space.Comment: 24 pages, 12 figure

Some Studies on life of Track Pin Rubber Bushes .

Track pin an important component in the tracks of heavy armoured vehicles is made of steel surrounded by rubber bush. This construction enables the pin to transmit the torsional loads. As the failure of track pin makes the vehicle immobilised, it is important to ensure a specified life for these pins. As the pin is made of rubber and steel, the theoretical studies become difficult. An attempt has been made to find out the parameters that influence the life of track pins. A finite element method is used to estimate the stresses in the rubber. The temperature rise due to the torsional loads, computed using the energy equation is found to be 64.86 °c for 1800 s at a speed of 30 km/hr. close to that obtained from actual field measurements