Something about the structure of the Galaxy

We analyse a sample of 507 evolved stars in the inner galactic Plane. We derive average ages for subsets of this sample and use those sets as beacons for the evolution of the Galaxy. In the Bulge the oldest OH/IR stars in the plane are 7.5 Gyr, in the Disk 2.7 Gyr. The vertical distribution of almost all AGB stars in the Disk is found to be nearly exponential, with scaleheight increasing from 100 pc for stars of \lsim 1 Gyr to 500 pc for stars of \gsim 5 Gyr. There may be a small, disjunct population of OH/IR stars. The radial distribution of AGB stars is dictated by the metallicity gradient. Unequivocal morphological evidence is presented for the existence of a central Bar, but parameters can be constrained only for a given spatial-density model. Using a variety of indicators, we identify the radii of the inner ultra-harmonic (2.5 kpc) and corotation resonance (3.5 kpc). We show that the 3-kpc arm is likely to be an inner ring, as observed in other barred galaxies, by identifying a group of evolved stars that is connected to the 3-kpc HI filament. Also, using several observed features, we argue that an inner-Lindblad resonance exists, at $\sim$1-1.5 kpc. The compositions of OH/IR populations within 1 kpc from the galactic Centre give insight into the bar-driven evolution of the inner regions. We suggest that the Bar is $\sim$8 Gyr old, relatively weak (SAB) and may be in a final stage of its existence.Comment: 18 pages, 15 figures, TeX, accepted for publication in MNRA

Trypsin activity as a function of variation in shrimp Penaeus indicus(Crustacea/Arthropoda)

The effect of varying ration size on trypsin activity was evaluated in postlarvae, juvenile and adult P. indicus maintained on a commercial pelleted feed. Total trypsin activity reported as 11m p-nitroanilide produced/minute/g tissue was lower (4.23-6.68 11m) in postlarvae in comparison to juvenile (7.24-8.92 11m) and adult (10.23-12.24 1lJII) animals. Highest activity was detccted at 12%,8-12% and 4-6% in postlarvae, Juveniles and adult P. indicus respectively which were the optimum ration sizes. while lowest activity was obtained in the starved animals. Specific activity however exhibIted no significant variation with regard to ration size and starvation (P > O.1J5)

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

Vision-based range estimation using helicopter flight data

Pilot aiding during low-altitude flight depends on the ability to detect and locate obstacles near the helicopter's intended flightpath. Computer-vision-based methods provide one general approach for obstacle detection and range estimation. Several algorithms have been developed for this purpose, but have not been tested with actual flight data. This paper presents results obtained using helicopter flight data with a feature-based range estimation algorithm. A method for recursively estimating range using a Kalman filter with a monocular sequence of images and knowledge of the camera's motion is described. The helicopter flight experiment and four resulting datasets are discussed. Finally the performance of the range estimation algorithm is explored in detail based on comparison of the range estimates with true range measurements collected during the flight experiment

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

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

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