Globular clusters as gamma ray sources

There are indications now that globular clusters contain a large number of low magnetic field millisecond pulsars. Since millisecond pulsars are expected to emit γ -rays due to curvature radiation, it is likely that globular clusters will themselves be sources of γ -rays bright enough to be detectable by present day instruments. Using the expression derived by Scharlemann, Arons & Fawley (1978) of the energy acquired by the electrons moving along the open magnetic field lines of the pulsars we have calculated the likely luminosity of γ -rays from globular clusters. We discuss our results in the light of the calculations reported in the literature based on some of the other models

Gamma-ray emission from pulsars

We have attempted to devise a scheme by which it may be possible to identify pulsars which are likely to be γ-ray pulsars. We apply this test to a representative population of pulsars and identify the likely candidates for γ emission. We also discuss some individual cases including the Crab and Vela pulsars

Gravitational Lensing Bound On The Average Redshift Of Gamma Ray Bursts In Models With Evolving Lenses

Identification of gravitationally lensed Gamma Ray Bursts (GRBs) in the BATSE 4B catalog can be used to constrain the average redshift $$ of the GRBs. In this paper we investigate the effect of evolving lenses on the of GRBs in different cosmological models of universe. The cosmological parameters $\Omega$ and $\Lambda$ have an effect on the of GRBs. The other factor which can change the $$is the evolution of galaxies. We consider three evolutionary model of galaxies. In particular, we find that the upper limit on$$ of GRBs is higher in evolving model of galaxies as compared to non-evolving models of galaxies.Comment: 23 pages,one plain LaTeX file with three postscript figures This is modified version with recent BATSE efficiency parameter and with the latest F paramete

Constraint On The Cosmological Constant From Gravitational Lenses In An Evolutionary Model Of Galaxies

We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Omega_{0}+lambda_{0} = 1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low--density universe, and its existence might be inferred by a statistical study of the lenses. In particular, the optical depth of the lens distribution may be used best for this purpose without depending much on the lens model. We calculate the optical depth (probabilty of a beam encountering with a lens event) for a source in a new picture of galaxy evolution based on number evolution in addition to pure luminosity evolution. It seems that present day galaxies result from the merging of a large number of building blocks. We have tried to put limit on the cosmological constant in this new picture of galaxy evolution. This evolutionary model of galaxies permits larger value of cosmological constant.Comment: Latex file with two figures, 24 page

Strange Quarks Nuggets in Space: Charges in Seven Settings

We have computed the charge that develops on an SQN in space as a result of balance between the rates of ionization by ambient gammas and capture of ambient electrons. We have also computed the times for achieving that equilibrium and binding energy of the least bound SQN electrons. We have done this for seven different settings. We sketch the calculations here and give their results in the Figure and Table II; details are in the Physical Review D.79.023513 (2009).Comment: Six pages, one figure. To appear in proceedings of the 2008 UCLA coference on dark matter and dark energ

The ground state of a class of noncritical 1D quantum spin systems can be approximated efficiently

We study families H_n of 1D quantum spin systems, where n is the number of spins, which have a spectral gap \Delta E between the ground-state and first-excited state energy that scales, asymptotically, as a constant in n. We show that if the ground state |\Omega_m> of the hamiltonian H_m on m spins, where m is an O(1) constant, is locally the same as the ground state |\Omega_n>, for arbitrarily large n, then an arbitrarily good approximation to the ground state of H_n can be stored efficiently for all n. We formulate a conjecture that, if true, would imply our result applies to all noncritical 1D spin systems. We also include an appendix on quasi-adiabatic evolutions.Comment: 9 pages, 1 eps figure, minor change

A comparative study of dexmedetomidine versus clonidine in epidural anaesthesia to assess the level of sedation in patients undergoing lower abdominal and lower limb surgery

Background: To compare study of dexmedetomidine versus clonidine in epidural anesthesia to assess the level of sedation in patients undergoing lower abdominal and lower limb surgery.Methods: This was a comparative study conducted on admitted ASA grade I and II patients undergoing lower abdominal and lower limb surgeries. The patients were divided into three groups of 30 patients each, according to the epidural medication they received:-Group A-received 15ml of bupivacaine (0.5%) and dexmedetomidine (1.0µg/kg body weight) in 1ml of normal saline; Group B-received 15ml of bupivacaine (0.5%) and clonidine (2.0µg/kg body weight) in 1ml of normal saline; Group C-received 15ml of bupivacaine (0.5%) with 1ml of normal saline. The heart rate, blood pressure, sensory dermatome level, Motor blocked level, pain and VAS were recorded at different time intervals. The side effects were also noted.Results: The baseline parameters were comparable among the groups. All the hemodynamic parameters and other study parameters were similar at Min. 0. All the hemodynamic parameters such as heart rate, blood pressure and SpO2 were variable at different time intervals. Motor block level   was significantly (p<0.05) lower in Group C than Group A and Group B from Min 50 to Min 90. The sedation score was observed to be nil in Group C. The post-op pain score became higher in Group C than Group A and Group B at subsequent time intervals. A 3 (10%) of the rescue agents was observed in Group C. Atropine (30%) and mephenteramine (10%) were common rescue agents in Group B. The bradycardia was observed in 30% patients of Group B and in 40% of Group A.Conclusions: On addition of dexmedetomidine as adjuvant to bupivacaine in epidural anesthesia provides better anesthesia and sedation than clonidine as adjuvant to bupivacaine or bupivacaine alone with mild hemodynamic changes which are easily manageable

How did the discussion go: Discourse act classification in social media conversations

We propose a novel attention based hierarchical LSTM model to classify discourse act sequences in social media conversations, aimed at mining data from online discussion using textual meanings beyond sentence level. The very uniqueness of the task is the complete categorization of possible pragmatic roles in informal textual discussions, contrary to extraction of question-answers, stance detection or sarcasm identification which are very much role specific tasks. Early attempt was made on a Reddit discussion dataset. We train our model on the same data, and present test results on two different datasets, one from Reddit and one from Facebook. Our proposed model outperformed the previous one in terms of domain independence; without using platform-dependent structural features, our hierarchical LSTM with word relevance attention mechanism achieved F1-scores of 71\% and 66\% respectively to predict discourse roles of comments in Reddit and Facebook discussions. Efficiency of recurrent and convolutional architectures in order to learn discursive representation on the same task has been presented and analyzed, with different word and comment embedding schemes. Our attention mechanism enables us to inquire into relevance ordering of text segments according to their roles in discourse. We present a human annotator experiment to unveil important observations about modeling and data annotation. Equipped with our text-based discourse identification model, we inquire into how heterogeneous non-textual features like location, time, leaning of information etc. play their roles in charaterizing online discussions on Facebook