In the context of active galactic nucleus (AGN) unification schemes, rapid variability properties... more In the context of active galactic nucleus (AGN) unification schemes, rapid variability properties play an important role in understanding any intrinsic differences between sources in different classes. In this respect, any clue based on spectral properties will be very useful toward understanding the mechanisms responsible for the origin of rapid small-scale optical variations or microvariability. Here we have added spectra of 46 radio-quiet quasars (RQQSOs) and Seyfert 1 galaxies to those of our previous sample of 37 such objects, all of which had been previously searched for microvariability. We took new optical spectra of 33 objects and obtained 13 others from the literature. Their Hβ and Mg II emission lines were carefully fitted to determine line widths (FWHM) as well as equivalent widths (EW) due to the broad emission-line components. The line widths were used to estimate black hole masses and Eddington ratios, ℓ. Both EW and FWHM are anticorrelated with ℓ. Nearly all trends were in agreement with our previous work, although the tendency for sources exhibiting microvariability to be of lower luminosity was not confirmed. Most importantly, this whole sample of EW distributions provides no evidence for the hypothesis that a weak jet component in radio-quiet AGNs is responsible for their microvariability.
Brazilian Journal of Infectious Diseases, May 23, 2015
Plasmodium falciparum and Plasmodium vivax malaria are endemic infections in India and are common... more Plasmodium falciparum and Plasmodium vivax malaria are endemic infections in India and are commonly associated with mild hematological abnormalities. Severe thrombocytopenia is common in isolated falciparum and mixed falciparum/vivax malaria, but is very rare in isolated P.vivax infection. We hereby report a case of severe thrombocytopenia (platelet count of 8x10(9)/L) in a case of vivax malaria. This is only the second case ever reported in the literature of such profound thrombocytopenia in a case of isolated P.vivax malaria.
Page 1. 1 Growth and Sustainability of Managed Security Services Networks: An Economic Perspectiv... more Page 1. 1 Growth and Sustainability of Managed Security Services Networks: An Economic Perspective Alok Gupta Dmitry Zhdanov Department of Information and Decision Sciences University of Minnesota Minneapolis, MN 55455 (agupta, dzhdanov@csom.umn.edu,) Abstract ...
ABSTRACT Blazars show strong and rapid flux variations over the entire electromagnetic spectrum o... more ABSTRACT Blazars show strong and rapid flux variations over the entire electromagnetic spectrum on diverse timescales ranging from a few tens of minutes to less than a day (intra day variation), a few days to several weeks (short term variation) and a few months to several years (long term variation). We have analyzed blazar X-ray fluxes taken by the RXTE and XMM-Newton satellites and optical archival data. We found strong evidence of the dection of quasi-periodic oscillations (QPOs) in a few blazars over a range of timescales, including S5 0716+714 (25 -73 minutes), PKS 2155-304 (4.6 hours), AO 0235+164 (17 days) and 1ES 2321+419 (420 days). We discuss possible explanations for blazar QPOs and we suggest which models are most likely to explain such variations in blazars over these diverse timescales.
We present multi-colour broad band CCD photometric observations of a few thousands of stars locat... more We present multi-colour broad band CCD photometric observations of a few thousands of stars located region of the galactic globular clusters NGC 1904 and NGC 6341. These observations are used to generate their deep colour magnitude diagrams (CMDs) to study overall morphologies of sub giant, red giant, asymptotic giant and horizontal branches. We also determine the main sequence morphology of the NGC 6341. A comparison of their CMDs with the theoretical isochrones given by Demarque et al. (1996) indicates an age of 14 and 16 Gyr for NGC 1904 and NGC 6341 GGCs respectively. We present a new method for artificial add star experiment. Using this method on the photometric data of galactic globular cluster NGC 6341, we determined the completeness factor in B, V and I pass bands. We have determined the luminosity function of the main sequence stars down to V $\sim$ 21.0 (M$_{V} \sim$ 6.5) from the V Vs (B-V) colour magnitude diagram of this cluster. Using accurate parameters of 64 GGCs, we derived relations between galactocentric distance R, distance from the galactic plane Z$_{g}$ and metalicity [Fe/H] of GGCs.
Management Information Systems Quarterly, Sep 1, 2012
Page 1. Electronic copy available at: http://ssrn.com/abstract=1557826 0 On the Use of Neurophysi... more Page 1. Electronic copy available at: http://ssrn.com/abstract=1557826 0 On the Use of Neurophysiological Tools in IS Research: 1 Developing a Research Agenda for NeuroIS 1 2 3 4 Angelika Dimoka 5 Temple University 6 7 Rajiv D. Banker 8 Temple University 9 10 ...
ABSTRACT To search for optical outbursts and intra-day variability (IDV) in blazars, we have carr... more ABSTRACT To search for optical outbursts and intra-day variability (IDV) in blazars, we have carried out multi-band optical photometric monitoring of half a dozen blazars using 1.04 meter Sam-puranand optical telescope (ST) of Aryabhatta Research Institute of observational sciencES (ARIES), Nainital, India. The telescope is equipped with cryogenically cooled 2K * 2K CCD detector which is mounted at f/13 Cassegrain focus of the telescope. We detected optical out-bursts in the blazars OJ 287 and Mrk 421. We also found strong evidence of rapid IDV in all the blazars which we have monitored. We briefly discuss the various emission mechanism responsible for rapid IDV.
International Journal of Electronic Commerce, 2006
ABSTRACT: This article analyzes the price dispersion for products observed on the Internet and re... more ABSTRACT: This article analyzes the price dispersion for products observed on the Internet and reaffirms the existence of substantial price dispersion across e-tailers. Comparison of advertised vs. unadvertised products reveals that predictions of search theory on adver-tising effect ...
Internet traffic pricing is necessary for the vitality of electronic commerce because uncontrolle... more Internet traffic pricing is necessary for the vitality of electronic commerce because uncontrolled congestion creates a detrimental effect on quality of the Internet services. Pricing approaches based on negative externality have potential to address the issue of congestion. ...
Advances in the Economics of Information Systems, 2005
Internet-based selling offers firms many new opportunities regarding the strategies for design of... more Internet-based selling offers firms many new opportunities regarding the strategies for design of mechanisms to support consumer transactions. This chapter examines the use of transparency as a strategy for Internet-based selling for maximizing firms' value from their selling ...
In the context of active galactic nucleus (AGN) unification schemes, rapid variability properties... more In the context of active galactic nucleus (AGN) unification schemes, rapid variability properties play an important role in understanding any intrinsic differences between sources in different classes. In this respect, any clue based on spectral properties will be very useful toward understanding the mechanisms responsible for the origin of rapid small-scale optical variations or microvariability. Here we have added spectra of 46 radio-quiet quasars (RQQSOs) and Seyfert 1 galaxies to those of our previous sample of 37 such objects, all of which had been previously searched for microvariability. We took new optical spectra of 33 objects and obtained 13 others from the literature. Their Hβ and Mg II emission lines were carefully fitted to determine line widths (FWHM) as well as equivalent widths (EW) due to the broad emission-line components. The line widths were used to estimate black hole masses and Eddington ratios, ℓ. Both EW and FWHM are anticorrelated with ℓ. Nearly all trends were in agreement with our previous work, although the tendency for sources exhibiting microvariability to be of lower luminosity was not confirmed. Most importantly, this whole sample of EW distributions provides no evidence for the hypothesis that a weak jet component in radio-quiet AGNs is responsible for their microvariability.
Brazilian Journal of Infectious Diseases, May 23, 2015
Plasmodium falciparum and Plasmodium vivax malaria are endemic infections in India and are common... more Plasmodium falciparum and Plasmodium vivax malaria are endemic infections in India and are commonly associated with mild hematological abnormalities. Severe thrombocytopenia is common in isolated falciparum and mixed falciparum/vivax malaria, but is very rare in isolated P.vivax infection. We hereby report a case of severe thrombocytopenia (platelet count of 8x10(9)/L) in a case of vivax malaria. This is only the second case ever reported in the literature of such profound thrombocytopenia in a case of isolated P.vivax malaria.
Page 1. 1 Growth and Sustainability of Managed Security Services Networks: An Economic Perspectiv... more Page 1. 1 Growth and Sustainability of Managed Security Services Networks: An Economic Perspective Alok Gupta Dmitry Zhdanov Department of Information and Decision Sciences University of Minnesota Minneapolis, MN 55455 (agupta, dzhdanov@csom.umn.edu,) Abstract ...
ABSTRACT Blazars show strong and rapid flux variations over the entire electromagnetic spectrum o... more ABSTRACT Blazars show strong and rapid flux variations over the entire electromagnetic spectrum on diverse timescales ranging from a few tens of minutes to less than a day (intra day variation), a few days to several weeks (short term variation) and a few months to several years (long term variation). We have analyzed blazar X-ray fluxes taken by the RXTE and XMM-Newton satellites and optical archival data. We found strong evidence of the dection of quasi-periodic oscillations (QPOs) in a few blazars over a range of timescales, including S5 0716+714 (25 -73 minutes), PKS 2155-304 (4.6 hours), AO 0235+164 (17 days) and 1ES 2321+419 (420 days). We discuss possible explanations for blazar QPOs and we suggest which models are most likely to explain such variations in blazars over these diverse timescales.
We present multi-colour broad band CCD photometric observations of a few thousands of stars locat... more We present multi-colour broad band CCD photometric observations of a few thousands of stars located region of the galactic globular clusters NGC 1904 and NGC 6341. These observations are used to generate their deep colour magnitude diagrams (CMDs) to study overall morphologies of sub giant, red giant, asymptotic giant and horizontal branches. We also determine the main sequence morphology of the NGC 6341. A comparison of their CMDs with the theoretical isochrones given by Demarque et al. (1996) indicates an age of 14 and 16 Gyr for NGC 1904 and NGC 6341 GGCs respectively. We present a new method for artificial add star experiment. Using this method on the photometric data of galactic globular cluster NGC 6341, we determined the completeness factor in B, V and I pass bands. We have determined the luminosity function of the main sequence stars down to V $\sim$ 21.0 (M$_{V} \sim$ 6.5) from the V Vs (B-V) colour magnitude diagram of this cluster. Using accurate parameters of 64 GGCs, we derived relations between galactocentric distance R, distance from the galactic plane Z$_{g}$ and metalicity [Fe/H] of GGCs.
Management Information Systems Quarterly, Sep 1, 2012
Page 1. Electronic copy available at: http://ssrn.com/abstract=1557826 0 On the Use of Neurophysi... more Page 1. Electronic copy available at: http://ssrn.com/abstract=1557826 0 On the Use of Neurophysiological Tools in IS Research: 1 Developing a Research Agenda for NeuroIS 1 2 3 4 Angelika Dimoka 5 Temple University 6 7 Rajiv D. Banker 8 Temple University 9 10 ...
ABSTRACT To search for optical outbursts and intra-day variability (IDV) in blazars, we have carr... more ABSTRACT To search for optical outbursts and intra-day variability (IDV) in blazars, we have carried out multi-band optical photometric monitoring of half a dozen blazars using 1.04 meter Sam-puranand optical telescope (ST) of Aryabhatta Research Institute of observational sciencES (ARIES), Nainital, India. The telescope is equipped with cryogenically cooled 2K * 2K CCD detector which is mounted at f/13 Cassegrain focus of the telescope. We detected optical out-bursts in the blazars OJ 287 and Mrk 421. We also found strong evidence of rapid IDV in all the blazars which we have monitored. We briefly discuss the various emission mechanism responsible for rapid IDV.
International Journal of Electronic Commerce, 2006
ABSTRACT: This article analyzes the price dispersion for products observed on the Internet and re... more ABSTRACT: This article analyzes the price dispersion for products observed on the Internet and reaffirms the existence of substantial price dispersion across e-tailers. Comparison of advertised vs. unadvertised products reveals that predictions of search theory on adver-tising effect ...
Internet traffic pricing is necessary for the vitality of electronic commerce because uncontrolle... more Internet traffic pricing is necessary for the vitality of electronic commerce because uncontrolled congestion creates a detrimental effect on quality of the Internet services. Pricing approaches based on negative externality have potential to address the issue of congestion. ...
Advances in the Economics of Information Systems, 2005
Internet-based selling offers firms many new opportunities regarding the strategies for design of... more Internet-based selling offers firms many new opportunities regarding the strategies for design of mechanisms to support consumer transactions. This chapter examines the use of transparency as a strategy for Internet-based selling for maximizing firms' value from their selling ...
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