Further evidence for intra-night optical variability of radio-quiet quasars

Although well established for BL Lac objects and radio-loud quasars, the occurrence of intra-night optical variability (INOV) in radio-quiet quasars is still debated, primarily since only a handful of INOV events with good statistical significance, albeit small amplitude, have been reported so far. This has motivated us to continue intra-night optical monitoring of bona-fide radio-quiet quasars (RQQs). Here we present the results for a sample of 11 RQQs monitored by us on 19 nights. On 5 of these nights a given RQQ was monitored simultaneously from two well separated observatories. In all, two clear cases and two probable case of INOV were detected. From these data, we estimate an INOV duty cycle of $\sim$8% for RQQs which would increase to 19% if the `probable variable' cases are also included. Such comparatively small INOV duty cycles for RQQs, together with the small INOV amplitudes ($\sim$1%), are in accord with the previously deduced characteristics of this phenomenon.Comment: 15 Pages, 4 Tables, 24 Figures; Accepted in BAS

The multifrequency behaviour of the recurrent nova RS Ophiuchi

This review concentrates on the multifrequency behaviour of RS Ophiuchi and in particular during its latest outburst. Confirmation of the 1945 outburst, bipolar outflows and its possible fate as a Type Ia Supernova are discussed.Comment: 5 pages, 5 figures, in The Golden Age of Cataclysmic Variables and Related Objects, F. Giovannelli & L. Sabau-Graziati (eds.), Mem. SAIt. 83 N.2 (in press

GASTROPROTECTIVE EFFECT OF ABRUS PRECATORIUS ON ETHANOL-INDUCED AND ASPIRIN + PYLORUS LIGATION-INDUCED PEPTIC ULCER IN RATS

Objective: The present work deals with investigation of Gastroprotective effect of Abrus precatorius on ethanol-induced and aspirin + pylorus ligation-induced peptic ulcer in rats. Methods: In ethanol-induced ulcer, after the pretreatment period of one hour, peptic ulcer was induced with absolute ethanol at a dose of 1 ml/200g (p.o.). Whereas, in aspirin + pylorus ligation-induced peptic ulcer, after the pretreatment with aspirin dose of 200mg/kg for 2 days then ulcer also induced by tight ligation of pylorus portion of stomach.Results: In ethanol-induced and aspirin + pylorus ligation-induced peptic ulcer in rats models, Abrus precatorius (AP) has shown significant decrease in ulcer area and significant increase in the mucosal production and also decreased the level of lipid peroxidase (LPO), and increased the levels of superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT).Conclusion: The present findings elucidate the therapeutic value of ethanolic extract of leaves of AP in the prevention of experimental peptic ulcer by virtue of its antioxidant, antisecretary and cytoprotective mechanisms.Key words:  Abrus precatorius, ethanol induced ulcer, aspirin + pylorus ligation, antioxidant.Â

Heavy Quarks Above the Top at the Tevatron

Recent developments in models with warped extra dimensions have opened new possibilities for vector-like quark studies at hadron colliders. These new vector-like quarks can mix sizably with light Standard Model quarks without violating low energy constraints. We perform a model-independent analysis to determine the Tevatron reach in the search for new quarks. We find that the Tevatron has great potential to observe such quarks via their electroweak single production due to their mixing with valence quarks. With 4 (8) fb-1 integrated luminosity, one may reach a 5\sigma statistical significance for a heavy quark of mass 580 (630) GeV if the heavy quark-Standard Model quark mixing parameter is order one.Comment: Version published in Phys. Rev. D; 19 pages, 4 figures; extended version including model building example; added Table

SECURING MULTIHOP NETWORK BY DETECTING AND LOCATING POLLUTION ATTACKS USING SPACEMAC.

It has been widely observed that providing security is one of the challenging task in Wireless sensor network(WSN). Program images need to be updated continuously as network programming happens in WSN. Many Networking protocols provide an efficient way to update these program images running on sensor nodes. One of the cryptographically strong protocol called DELUGE exists to address this challenge, but it involves high computational cost such as power consumption and communication costs. So Multiple one way key chain is proposed to secure a multihop network programming protocol which is lower in power consumption and communication costs. Even though one way key chain is used to provide security, network with static topology is considered. Network is made dynamic by adding mobility nodes to it. But the extra node added may not always be the genuine node. If it is an attacker node, there can be several pollution attacks. Attacker node travels through the network, and pollute the entire network. Wirelesss sensor network may not be able to detect these pollution attacks. In this paper, we are proposing a MAC scheme called Spacemac. It expands the network by adding nodes to it. Using SpaceMac, i) it detects the polluted packets early at the intermediate nodes. ii) it identifies the exact location of an attacker and eliminates them