Angular Resolution of the Pachmarhi Array of Cerenkov Telescopes

The Pachmarhi Array of Cerenkov Telescopes consists of a distributed array of 25 telescopes that are used to sample the atmospheric Cerenkov Photon showers. Each telescope consists of 7 parabolic mirrors each viewed by a single photo-multiplier tube. Reconstruction of photon showers are carried out using fast timing information on the arrival of pulses at each PMT. The shower front is fitted to a plane and the direction of arrival of primary particle initiating the shower is obtained. The error in the determination of the arrival direction of the primary has been estimated using the {\it split} array method. It is found to be $\sim 2.4^\prime ~$ for primaries of energy $> 3 \~TeV$. The dependence of the angular resolution on the separation between the telescopes and the number of detectors are also obtained from the data.Comment: 26 pages, 11 Postscript figures; uses elsart.cls. To appear in Astroparticle Physic

Scintillation Counters for the D0 Muon Upgrade

We present the results of an upgrade to the D0 muon system. Scintillating counters have been added to the existing central D0 muon system to provide rejection for cosmic ray muons and out-of-time background, and to provide additional fast timing information for muons in an upgraded Tevatron. Performance and results from the 1994-1996 Tevatron run are presented.Comment: 30 pages, 25 postscript figure

Anti-coagulant activity of a metalloprotease: Further characterization from the Indian cobra (Naja naja) venom

A high molecular mass, non toxic metalloprotease the NN-PF3 with the bound Ca2+ and Zn2+ from the Naja naja venom has been studied further for its anticoagulant property. The molecular mass by MALDI-TOF mass spectrometry was 67.81 kDa. The NN-PF3 exhibited fibrin(ogen)olytic activity. In addition to fibrinogen, NN-PF3 hydrolyzed blood and plasma clot with the later hydrolyzed about one fold higher. The α polymer of fibrin was preferentially hydrolyzed over the α chain but the β chain and γ-γ dimer remained untouched. It was devoid of plasminogen activation property. It prolonged the activated partial thromboplastin time, prothrombin time and the thrombin clotting time of citrated human plasma. It did not affect the thrombin activity. In mice, defibrinogentaion, prolonged bleeding time (P <0.01) and reduced fibrinogen level were observed following intravenous injection. Human plasma or α2-macroglobulin did not, but the polyvalent anti-venom inhibited the NN-PF3 activity. In contrast to most snake venom metalloproteases, it did not degrade extra cellular matrix proteins. © Springer Science+Business Media, LLC 2009

VHE Gamma-ray Observation of Crab Nebula with HAGAR Telescope Array

International audienceHAGAR is a system of seven Non-imaging Atmospheric Cherenkov Telescopes located at Hanle in the Ladakh region of the Indian Himalayas at an altitude of 4270 meters amsl. Since 2008, we have observed the Crab Nebula to assess the performance of the HAGAR telescopes. We describe the analysis technique for the estimation of γ-ray signal amidst cosmic ray background. The consolidated results spanning nine years of the Crab nebula observations show long term performance of the HAGAR telescopes. Based on about 219 hours of data, we report the detection of γ-rays from the Crab Nebula at a significance level of about 20σ, corresponding to a time averaged flux of (1.64±0.09) × 10$^{− 10}$ photons cm$^{− 2}$ sec$^{− 1}$ above 230 GeV. Also, we perform a detailed study of possible systematic effects in our analysis method on data taken with the HAGAR telescopes