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Development of a Triggering Arrangement For the KALI-30GW MARX Generator
S. Mitra,T. S. Kolge,Ritu Agarwal,P. C. Saroj,Ankur Patel,K. Senthil,Vishnu Sharma,S. V. Tewari,Archana Sharma,K. C. Mittal 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.4
This paper reports the design methodology and implementation experiments for a solid-statebasedtriggering arrangement for the MARX generator of the KALI-30GW (1 MV, 30 kA, 80 ns)pulsed power system. The 15-stage bipolar MARX generator of the KALI-30GW system is triggeredusing a trigatron-type spark gap. An insulated-gate bipolar-transistor (IGBT)-based trigger supplyis used to trigger the first spark gap, and the next two spark gaps are triggered by using internallygeneratedtrigger pulses. Optically-isolated arrangements are provided for a human interface. Theentire assembly was tested with a dummy copper sulphate load, and an excellent triggering rangeof 7 − 12 kV was achieved. The circuit diagram, analysis and experimental results of the triggeringarrangement are presented in the paper.
A New coumarin from the seeds of Jute (Corchorus olitorius L.)
K. K. Mukherjee,S. K. Mitra,S. N. Ganguly 한국생약학회 1998 Natural Product Sciences Vol.4 No.1
From the chloroform extract of the defatted seeds of jute a new coumarin C_9H_6O<sub>4</sub>, m.p. 178-179℃, was isolated. The structure of the compound was established as 4,7-dihydroxy coumarin on the basis of physical methods viz. ^1H NMR, ^13C NMR and Ms.
A. Mathur,S.S. Roy,M. Tweedie,S. Mukhopadhyay,S.K. Mitra,J.A. McLaughlin 한국물리학회 2009 Current Applied Physics Vol.9 No.6
In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp microstructure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU- 8) stamp includes microchannel arrays of approximately 30 ㎛ in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 ㎛ wide and 6 ㎛ in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 ℃ embossing temperature were optimum for transferring the microstructure to the PMMA substrate. In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp microstructure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU- 8) stamp includes microchannel arrays of approximately 30 ㎛ in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 ㎛ wide and 6 ㎛ in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 ℃ embossing temperature were optimum for transferring the microstructure to the PMMA substrate.
김종성,최세곤,( J . S . Kim,S . G . Choi,B . Chatterjee,P . K . Banerjee,S . S . Mitra ) 한국센서학회 1993 센서학회지 Vol.2 No.2
Boron nitride films were deposited by rf reactive sputtering. Optical properties of resultant films were studied as a function of deposition parameters such as nitrogen pressure and substrate bias. Resultant films showed optical characteristics similar to those of hexagonal boron nitride. Composition of the film was determined by X-ray photoelectron spectroscopy. From the IR reflectivity data, transverse optical mode(TO) and longitudinal optical mode(LO) were derived by Kramers-Kronig model. Absorption coefficient was also determined from IR transmission data. Resultant TO and LO frequencies showed that substrate bias caused broadening of reststrahlen band of rf sputtered boron nitride. Refractive index of boron nitride films varied from 1.67 to 3.05 for different deposition conditions. Optical gap of rf sputtered boron nitride films was in the range of 3.8-4.5 eV.
S. Maitra,R. Mitra,T.K. Nath 한국물리학회 2020 Current Applied Physics Vol.20 No.5
In this work, we have successfully synthesized MgNiO2 using a sol-gel wet chemical synthesis technique named MNO - 3. Electrochemical measurements in the presence of aqueous 1 M Li2SO4 electrolyte indicate that MNO - 3 samples exhibit a capacitance value of about 30 F/g and an energy density of about 20 Wh/kg. Subsequently, in the experiment involving aqueous 0.5 M Na2SO4 electrolyte system, it has been found that the capacitance for MNO - 3 sample is about 34 F/g and the energy density is about 23 Wh/kg for MNO - 3 sample. Finally, in the presence of aqueous-based 1 M Mg(ClO4)2 electrolyte, MNO - 3 sample is found to exhibit a capacitance of about 26 F/g and an energy density of about 17 Wh/kg, respectively. In all three electrolyte systems, the MNO -3 sample exhibit a long cycle capacitance retention of greater than 85% for 1000 charge-discharge cycles.
S. Maitra,P.K. Chakraborty,R. Mitra,T.K. Nath 한국물리학회 2020 Current Applied Physics Vol.20 No.12
We report here the cost-effective synthesis of Magnesium Cobalt Oxide (MgCoO2) sample by the sol-gel synthesis route labeled as MCO - 3. In presence of aqueous 1 M Lithium Sulphate (Li2SO4) electrolyte, we obtained a capacitance of 56 F/g, an energy density of 38 Wh/kg and a capacitance retention of 92.53 % (at 5 A/g) after undergoing 1000 charge-discharge cycles. For the aqueous 1 M Sodium Perchlorate (NaClO4) electrolyte system, we found the capacitance, energy density and capacitance retention of 47 F/g, 31 Wh/kg and 91.41% (at 3.5 A/g for 1000 charge-discharge cycles), respectively. These results establish MgCoO2 as suitable electrode material in aqueous lithium-ion and sodium-ion supercapacitor devices. Further, MCO - 3 in the presence of aqueous 1 M Potassium Hydroxide (KOH) electrolyte showed an overpotential of 400 mV and a Tafel slope of 174 mV/dec, making it a suitable candidate for alkaline Hydrogen Evolution Reaction (HER) electrocatalyst.
Maitra S.,Mitra R.,Nath T.K. 한국물리학회 2021 Current Applied Physics Vol.27 No.-
Herein this work, we have used the sol-gel chemical synthesis method to prepare spherical shaped MgFe2O4 nanoparticles having size 45–50 nm. Using 1 mol L 1 Sodium Perchlorate (NaClO4) electrolyte, a capacitance of 61 F/g, a capacitance retention of 82.91% (after undergoing 1000 cycles), and an energy density of 41 Wh/kg have been achieved. Using 1 mol L 1 Magnesium Perchlorate (Mg(ClO4)2) as electrolyte, a capacitance of 43 F/g, a capacitance retention of 82.15%, and an energy density of 29 Wh/kg have been realized. Furthermore, MgFe2O4 nanospheres exhibited an overpotential (η) = 1.09 V, a Tafel slope (b) = 317 mV/dec in regard to alkaline Oxygen Evolution Reaction (OER) electrocatalyst. It also achieved η = 402 mV and b = 241 mV/dec in regard towards alkaline Hydrogen Evolution Reaction (HER) electrocatalyst. These results signify the suitability of MgFe2O4 nanoparticles for high energy density aqueous supercapacitor and water splitting electrocatalyst applications.
Crude oil and stock market co-movement: Evidence from G7 and BRICS nations
( Vaneet Bhatia ),( S K Mitra ) 한양대학교 경제연구소 2018 JOURNAL OF ECONOMIC RESEARCH Vol.23 No.1
This paper examines the dynamic correlation between crude oil and stock market indices of major developed (G7) and emerging (BRICS) economies by analyzing weekly data from January 2000 to March 2017. Results suggest an existence of dynamic correlation between crude oil and stock markets throughout the study period. Results also indicate a considerable increase in dynamic correlation between crude oil and stock markets during the recent crisis. Interestingly, crude oil and indices of developed nations exhibit almost similar co-movements, but the correlation movements between crude oil and the stock indices of BRICS nations show weak homogeneity in the group. The impulse response function in variance (volatility) was employed to investigate the response of stock market indices of G7 and BRICS nations to the shock in the crude oil market and vice versa. Overall, these findings have significant implications for policy makers, investors and portfolio managers.
Dual targeting of EphA2 and FAK in ovarian carcinoma.
Shahzad, Mian M K,Lu, Chunhua,Lee, Jeong-Won,Stone, Rebecca L,Mitra, Rahul,Mangala, Lingegowda S,Lu, Yiling,Baggerly, Keith A,Danes, Christopher G,Nick, Alpa M,Halder, Jyotsnabaran,Kim, Hye-Sun,Vivas- Landes Bioscience 2009 Cancer Biology & Therapy Vol.8 No.11
<P>EphA2 gene silencing has been shown to result in antitumor efficacy. Here we considered whether silencing additional targets downstream of EphA2 would further enhance the therapeutic effect. EphA2 targeted siRNA was tested in combination with either FAK or Src targeted siRNA using DOPC nanoliposomes in orthotopic models of ovarian carcinoma. The effects of therapy were determined by changes in tumor weight, proliferation (Ki-67), and microvessel density (CD31). In our initial in vivo study, EphA2 plus FAK silencing resulted in the greatest reduction in tumor growth (by 73%, p < 0.005) as compared to control siRNA alone. In the SKOV3ip1 and HeyA8 ovarian cancer models, EphA2 siRNA-DOPC treatment resulted in a 50-67% decrease in tumor growth (p < 0.02, for both), and FAK siRNA-DOPC resulted in a 61-62% decrease in tumor growth (p < 0.009, p < 0.05, respectively). EphA2 plus FAK siRNA-DOPC treatment resulted in a significant reduction (SKOV3ip1: 76%, p < 0.007, HeyA8: 90%, p < 0.003) in tumor growth compared to control siRNA-DOPC. Combination treatment with EphA2 + FAK siRNA-DOPC resulted in significant decreases in tumor cell proliferation (p < 0.001) and microvessel density compared to control siRNA-DOPC (80%; p < 0.001), or the monotherapy groups (p values <0.001). These data suggest that the antitumor efficacy of in vivo EphA2 targeting is enhanced in combination with FAK silencing. Dual targeting of EphA2 and FAK may have therapeutic implications for ovarian cancer management.</P>