A STUDY OF THE DYNAMICAL CROSS CORRELATION FUNCTION IN A BLACK HOLE SOURCE XTE J1550-564

SRIRAM, K.,CHOI, C.S.,RAO, A.R. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

The short time scale X-ray variability associated with the accretion disk around compact objects is complex and is vaguely understood. The study of the cross correlation function gives an insight into the energy dependent behavior of the variations and hence connected processes. Using high resolution RXTE data, we investigate the dynamical cross correlation function of an observation of a black hole source XTE J1550-564 in the steep power law state. The cross correlation between soft and hard X- ray energy bands revealed both correlated and anti-correlated delays (${\leq}{\pm}15s$) on a correlation time scale of 50 s. It was noticed that the observed delays were similar to the delays between X-ray and optical/IR bands in other black hole and neutron star sources. We discuss the possible mechanisms/processes to explain the observed delays in the dynamical CCF.

A Novel, Potent, Small Molecule AKT Inhibitor Exhibits Efficacy against Lung Cancer Cells In Vitro

Saketh S. Dinavahi,Rajagopalan Prasanna,Sriram Dharmarajan,Yogeeswari Perumal,Srikant Viswanadha 대한암학회 2015 Cancer Research and Treatment Vol.47 No.4

Purpose Anomalies of Akt regulation, including overexpression in lung cancer, impart resistance toconventional chemotherapy and radiation, thereby implicating this kinase as a therapeuticintervention point. A novel scaffold of Akt inhibitors was developed through virtual screeningof chemical databases available at Birla Institute of Technology and Science, Pilani, Hyderabad,based on docking studies using Maestro. A benzothienopyrimidine derivative (BIA-6)was identified as a potential lead molecule that inhibited Akt1 enzyme activity with an IC50of 256 nM. Materials and MethodsBIA-6 was tested for in vitro Akt1 inhibition using a fluorescence resonance energy transferkit. Anti-proliferative activity was tested in NCI-H460, A549, NCI-H1975, and NCI-H2170cell lines. The effect of the compound on p-Akt (S473) was estimated. ResultsBIA-6 allosterically caused a dose dependent reduction of growth of cell lines with a halfmaximal growth inhibition (GI50) range of 0.49 !M to 6.6 !M. Cell cycle analysis indicatedthat BIA-6 caused a G1 phase arrest at < 100 nM but led to apoptosis at higher doses. BIA-6 also exhibited synergism with standard chemotherapeutic agents. ConclusionBIA-6 is a novel, allosteric Akt inhibitor with potent anti-cancer activity in lung cancer celllines, that effectively blocks the phosphoinositide-3 kinase/Akt pathway with a high marginselectivity towards normal cells.

Optically Controlled Silicon MESFET Modeling Considering Diffusion Process

S. N. Chattopadhyay,N. Motoyama,A. Rudra,A. Sharma,S. Sriram,C. B. Overton,P. Pandey 대한전자공학회 2007 Journal of semiconductor technology and science Vol.7 No.3

An analytical model is proposed for an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), known as Optical Field Effect Transistor (OPFET) considering the diffusion fabrication process. The electrical parameters such as threshold voltage, drain-source current, gate capacitances and switching response have been determined for the dark and various illuminated conditions. The Photovoltaic effect due to photogenerated carriers under illumination is shown to modulate the channel cross-section, which in turn significantly changes the threshold voltage, drainsource current, the gate capacitances and the device switching speed. The threshold voltage VT is reduced under optical illumination condition, which leads the device to change the device property from enhancement mode to depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current IDS for different gate-source voltage Vgs is significantly increased with optical illumination for photon flux densities of Φ = 10<SUP>15</SUP> and 10<SUP>17</SUP> /㎠s compared to the dark condition. Further more, the drain-source current as a function of drain-source voltage VDS is evaluated to find the I-V characteristics for various pinch-off voltages VP for optimization of impurity flux density QDiff by diffusion process. The resulting I-V characteristics also show that the diffusion process introduces less process-induced damage compared to ion implantation, which suffers from current reduction due to a large number of defects introduced by the ion implantation process. Further the results show significant increase in gate-source capacitance Cgs and gate-drain capacitance Cgd for optical illuminations, where the photo-induced voltage has a significant role on gate capacitances. The switching time τ of the OPFET device is computed for dark and illumination conditions. The switching time τ is greatly reduced by optical illumination and is also a function of device active layer thickness and corresponding impurity flux density QDiff. Thus it is shown that the diffusion process shows great potential for improvement of optoelectronic devices in quantum efficiency and other performance areas.

Some results on inequalities of intuitionistic fuzzy matrices

S. Sriram,J. Boobalan 원광대학교 기초자연과학연구소 2019 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.17 No.1

In this paper, we study certain inequalities of intuitionistic fuzzy matrices with respect to algebraic sum and algebraic product.

Possible Presence of a Third Body in the<i>Kepler K2</i>Variable EPIC 202073314

Sriram, K.,Malu, S.,Choi, C. S.,Rao, P. Vivekananda American Astronomical Society 2018 The Astronomical journal Vol.155 No.4

A Study of the<i>Kepler K2</i>Variable EPIC 211957146 Exhibiting a Variable O’ Connell Effect

Sriram, K.,Malu, S.,Choi, C. S.,Rao, P. Vivekananda American Astronomical Society 2017 The Astronomical journal Vol.153 No.5

<P>We present the multi-band photometric and spectroscopic study of an over-contact binary system, EPIC 211957146. The light curves exhibit a variable O' Connell effect, confirmed from our observational data and the Kepler K2 data. The best photometric solution incorporating a dark spot over the primary component unveils that the system has a low-mass ratio (q similar to 0.17) and a high inclination (i similar to 85 degrees). To confirm the solution and constrain the uncertainty, Monte-Carlo simulations are performed and the results are reported. Based on the O-C diagram analysis, we see that the variable shows a period increase at the rate of dP/dt similar to 1.06. x. 10(-6) days yr(-1), which is higher than the theoretically predicted value. Presence of a third body having a period of similar to 16.23 years is evident from the O-C diagram. No filled-in effect is observed in the Ha line, while the effect is vividly present in the Na line. From the Kepler K2 data, we found that the primary and secondary minima exhibit an anti-correlated O-C variation followed by an erratic behavior. This is possibly caused by the longitudinal motion of the spot, and hence, we set a lower limit of similar to 40 days for the spot modulation. We also observe a possibly associated photometric difference in the primary depth by comparing our light curves with Kepler K2 normalized light curves. This system has a low-mass ratio and a high fill-out factor, and, theoretically, such a physical configuration would lead to a merger.</P>

ASAS J083241+2332.4: A NEW EXTREME LOW MASS RATIO OVERCONTACT BINARY SYSTEM

Sriram, K.,Malu, S.,Choi, C. S.,Vivekananda Rao, P. American Astronomical Society 2016 The Astronomical journal Vol.151 No.3

<P>We present the R-and V-band CCD photometry and H alpha line studies of an overcontact binary ASAS J083241+2332.4. The light curves exhibit totality along with a trace of the O'Connell effect. The photometric solution indicates that this system falls into the category of extreme low-mass ratio overcontact binaries with a mass ratio, q similar to 0.06. Although a trace of the O' Connell effect is observed, constancy of the H alpha line along various phases suggest that a relatively higher magnetic activity is needed for it to show a prominent fill-in effect. The study of O-C variations reveals that the period of the binary shows a secular increase at the rate of dP/dt similar to 0.0765 s years(-1), which is superimposed by a low, but significant, sinusoidal modulation with a period of similar to 8.25 years. Assuming that the sinusoidal variation is due to the presence of a third body, orbital elements have been derived. There exist three other similar systems, SX Crv, V857 Her, and E53, which have extremely low mass ratios and we conclude that ASAS J083241+2332.4 resembles SX Crv in many respects. Theoretical studies indicate that at a critical mass ratio range, q(critical) = 0.07-0.09, overcontact binaries should merge and form a fast rotating star, but it has been suggested that q(critical) can continue to fall up to 0.05 depending on the primary's mass and structure. Moreover, the obtained fill-out factors (50%-70%) indicate that mass loss is considerable and hydrodynamical simulations advocate that mass loss from L-2 is mandatory for a successful merging process. Comprehensively, the results indicate that ASAS J083241+2332.4 is at a stage of merger. The pivotal role played by the subtle nature of the derived mass ratio in forming a rapidly rotating star has been discussed.</P>

Optically Controlled Silicon MESFET Modeling Considering Diffusion Process

Chattopadhyay, S.N.,Motoyama, N.,Rudra, A.,Sharma, A.,Sriram, S.,Overton, C.B.,Pandey, P. The Institute of Electronics and Information Engin 2007 Journal of semiconductor technology and science Vol.7 No.3

An analytical model is proposed for an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), known as Optical Field Effect Transistor (OPFET) considering the diffusion fabrication process. The electrical parameters such as threshold voltage, drain-source current, gate capacitances and switching response have been determined for the dark and various illuminated conditions. The Photovoltaic effect due to photogenerated carriers under illumination is shown to modulate the channel cross-section, which in turn significantly changes the threshold voltage, drainsource current, the gate capacitances and the device switching speed. The threshold voltage $V_T$ is reduced under optical illumination condition, which leads the device to change the device property from enhancement mode to depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current IDS for different gate-source voltage $V_{gs}$ is significantly increased with optical illumination for photon flux densities of ${\Phi}=10^{15}\;and\;10^{17}/cm^2s$ compared to the dark condition. Further more, the drain-source current as a function of drain-source voltage $V_{DS}$ is evaluated to find the I-V characteristics for various pinch-off voltages $V_P$ for optimization of impurity flux density $Q_{Diff}$ by diffusion process. The resulting I-V characteristics also show that the diffusion process introduces less process-induced damage compared to ion implantation, which suffers from current reduction due to a large number of defects introduced by the ion implantation process. Further the results show significant increase in gate-source capacitance $C_{gs}$ and gate-drain capacitance $C_{gd}$ for optical illuminations, where the photo-induced voltage has a significant role on gate capacitances. The switching time ${\tau}$ of the OPFET device is computed for dark and illumination conditions. The switching time ${\tau}$ is greatly reduced by optical illumination and is also a function of device active layer thickness and corresponding impurity flux density $Q_{Diff}$. Thus it is shown that the diffusion process shows great potential for improvement of optoelectronic devices in quantum efficiency and other performance areas.

ANTI-CORRELATED SOFT LAGS IN THE INTERMEDIATE STATE OF BLACK HOLE SOURCE GX 339-4

Sriram, K.,Rao, A. R.,Choi, C. S. IOP Publishing 2010 The Astrophysical journal Vol.725 No.1

Inkjet Printing of Yttria Stabilized Zirconia Nano Particles on Metal Substrates

S. H. Rahul,K. Balasubramanian,Sriram Venkatesh 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

This paper describes a novel methodology of coating Yttria stabilized Zirconia (YSZ) suspensions on AISI316L steel substrates and involves a micro structural investigation to understand the sintering behavior. Nano sized particles are used at lowering of sintering temperature. Nano particle suspension inks prepared through high energy milling process is visibly stable due to ionic charge carriers in binder and solvent. Deposition of suspended material was done through inkjet printing (IJP) and spin coating (SC) processes. Print head offset in X and Y directions lead to fabrication of homogeneous layers. Inkjet printing at elevated temperatures is useful especially in controlling nano particle seepage through porous substrates. Low temperature sintering of suspended particles in the ink leads to development of porous YSZ films due to the presence of carrier solvent and binder/dispersants in the ink. Sintered films exhibit completely stable tetragonal zirconia with uniformly porous microstructure. Pore sizes of 50 nm and 100 nm have been reported at least for inkjet printed and spin coated films respectively. The homogeneity observed in pores of YSZ film is a typical characteristic of inkjet printing process which is attributed to the layer by layer stacking of nano particles during the deposition process.