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Search Results: 1 - 10 of 1177 matches for " Chakrabarti Sudipta "
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Unusual Change in Critical Frequency of F2 Layer during and Prior to Earthquakes  [PDF]
Soujan Ghosh, Sudipta Sasmal, Subrata Kumar Midya, Sandip K. Chakrabarti
Open Journal of Earthquake Research (OJER) , 2017, DOI: 10.4236/ojer.2017.64012
The unusualness in the critical frequency of different layers of earth’s ionosphere is commensurate to be associated with seismic events. We present study of critical frequency of F2 layer (denoted as f0F2) during some major earthquakes in South American region. We use the semi-empirical Barbier’s theorem of air-glow and define a parameter using the critical frequency and virtual height of F2 layer and named it as “F Parameter”. To investigate the variation of this parameter, we consider five large earthquakes in the junction of Nazca plate and South American plate having magnitude greater than M > 6.5 and study the temporal variation of F parameter during these earthquakes. The F Parameter is measured using the ionograms as recorded from the Ionosonde in Jicamarca Radio Observatory (lat. 11.95°S, long 76.87°W) in Chile which lies within the earthquake preparation zones of these five earthquakes. We examine the F Parameter within a span of ±15 days during earthquakes and observed significant change in the evaluated F Parameter in 12 to 3 days prior to the earthquakes. The increment is over +3σ from the normal variation. We also observe significant changes during aftershock events. The solar geomagnetic indices were found to be low which ensures that these anomalies in F Parameter are due to seismic events.
Equilibrium study of Protein/DNA Complexes from Crystal Structure Data
Sudipta Samanta,J. Chakrabarti,Dhananjay Bhattacharyya
Physics , 2006,
Abstract: From the crystal structure data and using the concept of equilbrium statistical mechanics we show how to calculate the thermodynamics of protein/DNA complexes. We apply the method to the TATA-box binding protein (TBP)/TATA sequence complex. We have estimated the change in free energy and entropy for each of the base pair (bp). The local rigidity of the DNA is estimated from the curvature of the free energy. We also estimate the free energy gain of the protein due to bond formation with a particular bp. We thus figure out the bps responsible for specific binding.
The Keith Edward scoring system: A case control study
Sarkar Supriya,Paul Dilip,Chakrabarti Sudipta,Mandal Nirmal
Lung India , 2009,
Abstract: Objective: The World health organization (WHO) has accepted Keith Edward scoring system for the diagnosis of childhood tuberculosis (TB). In the present study, we evaluated this scoring system. Methods and Results: We included 53 children with confirmed TB involving different organs, admitted in NB Medical College, during two years period as cases; and 50 randomly selected, age, sex, and organ matched confirmed non-TB cases as controls. We noticed 15.1% false negative and 22% false positive results in our study, and the scoring system had 84.9% sensitivity, 78% specificity, and 80.36% positive predictive value. Likelihood ratio positive (LR+) was 3.86, likelihood ratio negative (LR-) was 0.19, and overall agreement was 81.55%. We observed that Keith Edward scoring system was less effective in children suffering from non-TB chronic diseases (false positive rate: 45.5%). We found no significant difference in nutritional status between study and control groups (P = 0.65). We noticed that more than 15-mm indurations for tuberculin test were specific for TB in children. Conclusion: We concluded that Keith Edward scoring system is good for public health purpose, but there is a scope for improvement, and further study is required for this purpose.
Retiform hemangioendothelioma with lymph node metastasis: A rare entity
Bhutoria Bhawna,Konar Abantika,Chakrabarti Sudipta,Das Shikha
Indian Journal of Dermatology, Venereology and Leprology , 2009,
Abstract: Retiform hemangioendothelioma (RH) is a rare, recently described, unique kind of low grade angiosarcoma. The tumor is characterized by distinctive arborizing blood vessels that mimic the appearance of rete testis. The tumor chiefly originates from the skin and subcutaneous tissue and has a tendency to recur locally. Only one case with lymph node metastasis has been reported previously. Another such rare case of RH is being reported in an adult female who presented with a subcutaneous nodule, underwent multiple recurrences and uniquely metastasized to regional lymph node.
Extraovarian granulosa cell tumor
Paul Prabir,Chakraborty Jayati,Chakrabarti Sudipta,Chattopadhyay Bitan
Indian Journal of Pathology and Microbiology , 2009,
Abstract: Extraovarian granulosa cell tumor (GCT) is a very uncommon tumor, assumed to arise from the ectopic gonadal tissue along the embryonal route of the genital ridge. One such rare case of extraovarian GCT was encountered in a 58-year-old female who presented with a large intraabdominal lump. Computerized tomography revealed one large retroperitoneal mass measuring 15cm x 16cm and another mesenteric mass of 8cm x 5cm size. The patient had a history of hysterectomy with bilateral salpingooophorectomy 20 years ago for uterine leiomyoma. Ultrasonography-guided aspiration smears revealed cytological features suggestive of GCT. Histopathological examination of the excised masses showed features of adult-type GCT. Because metastatic epithelial tumors, particularly from the ovaries, may show identical morphology, immunostains for inhibin and epithelial membrane antigen (EMA) were performed. The tumor showed positivity for inhibin while EMA was negative thus confirming the diagnosis of GCT. As this patient had no previous history of GCT and was oophorectomized 20 years ago, the tumor was considered as extraovarian. A diagnosis of extraovarian GCT should be carried out after excluding any previous history of GCT of the ovary. Immunostains help to differentiate GCTs from other neoplasms.
Studies on Physico-Chemical and Microbiological Parameters of Water Samples Before and After Jute Retting
Biswapriya Das,Sudipta Tripathi,Ashis Chakraborty,Kalyan Chakrabarti
Journal of Biological Sciences , 2011,
Abstract: The aim of the research was to study the effect of jute retting on various physico-chemical and microbiological parameters of retting water and water samples were collected before and after retting, from three well-known jute growing areas of N-24 Parganas viz., Sonatikari, Baduria and Swarupnagar, West Bengal, India. Standard methods were applied to determine pH, Ec, Chemical Oxygen Demand (COD), hardness, Calcium (Ca), Magnesium (Mg), bicarbonate, chloride content, bacterial, fungal, pectinolytic and spore forming bacterial colony forming units. Irrespective of the locations, the pH of the post-retting water samples was more acidic than the pre-retting water samples. Other physico-chemical parameters like Ec, COD, hardness and metal contents increased in the post-retting water samples. The post-retting water samples also registered higher bacterial, fungal, pectinolytic and spore forming bacterial colony forming units.
Black hole phase transitions via Bragg-Williams
Souvik Banerjee,Sayan K. Chakrabarti,Sudipta Mukherji,Binata Panda
Physics , 2010, DOI: 10.1142/S0217751X11053845
Abstract: We argue that a convenient way to analyze instabilities of black holes in AdS space is via Bragg-Williams construction of a free energy function. Starting with a pedagogical review of this construction in condensed matter systems and also its implementation to Hawking-Page transition, we study instabilities associated with hairy black holes and also with the $R$-charged black holes. For the hairy black holes, an analysis of thermal quench is presented.
Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys
Sunil Wilfred D'Souza,Tufan Roy,Sudipta Roy Barman,Aparna Chakrabarti
Physics , 2013, DOI: 10.1088/0953-8984/26/50/506001
Abstract: Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn$_2$NiGa and Mn$_{1+x}$Ni$_{2-x}$Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn$_2$NiGa is ferrimagnetic and its total spin moment increases when disorder in the occupancy of Mn$_{\rm Ni}$ (Mn atom in Ni position) is considered. The moment further increases when Mn-Ga antisite defect[1] is included in the calculation. A reasonable estimate of $T_C$ for Mn$_2$NiGa is obtained from the exchange parameters for the disordered structure. Disorder influences the electronic structure of Mn$_2$NiGa through overall broadening of the density of states and a decrease in the exchange splitting. Inclusion of antisite defects marginally broaden the minority spin partial DOS (PDOS), while the majority spin PDOS is hardly affected. For Mn$_{1+x}$Ni$_{2-x}$Ga where 1$\geq$$x$$\geq$0, as $x$ decreases, Mn$_{\rm Mn}$ moment increases while Mn$_{\rm Ni}$ moment decreases in both austenite and martensite phases. For $x$$\geq$ 0.25, the total moment of the martensite phase is smaller compared to the austenite phase, which indicates possible occurrence of inverse magnetocaloric effect. We find that the redistribution of Ni 3$d$- Mn$_{\rm Ni}$ 3$d$ minority spin electron states close to the Fermi level is primarily responsible for the stability of the martensite phase in Mn-Ni-Ga.
First VLF detections of ionospheric disturbances due to Soft Gamma ray Repeater SGR J1550-5418 and Gamma Ray Burst GRB 090424
Sandip K. Chakrabarti,Sushanta K. Mondal,Sudipta Sasmal,Debashis Bhowmick,Asit K. Chowdhuri,Narendra N. Patra
Physics , 2011, DOI: 10.1007/s12648-010-0145-5
Abstract: We present the first report of the detection of sudden ionospheric disturbances (SIDs) due to a Soft Gamma Ray Repeater (SGR) SGR J1550-5418 and a Gamma Ray Burst (GRB) GRB 090424. These detections were made with receiving stations of Indian Centre for Space Physics which were monitoring Very Low Frequency signals (VLFs) from the VTX transmitter located at the southern tip of Indian sub-continent. These positive detections add to the list of a handful of similar detections of other GRBs and SGRs throughout the world.
Kinetic Studies for an Aerobic Packed Bed Biofilm Reactor for Treatment of Organic Wastewater with and without Phenol  [PDF]
Sudipta Dey, Somnath Mukherjee
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.28084
Abstract: A laboratory scale aerobic fixed film bioreactor packed with glass beads for biofilm growth was used to evaluate the removal efficiencies of COD and phenol for a carbohydrate—phenol mixture in wastewater. It was done by an indigenous mixed culture inoculums developed after collecting sludge from a return line of an activated sludge plant. The test result on continuous flow in the above biofilm reactor indicated an optimum hydraulic loading range of 4-6.4 m3day-1m-2 for attainment of reasonable amount of COD removal in case of carbohydrate substrate only. The COD removal efficiency, however, gradually depleted from 100% to 54% by gradual increase in organic loading (OLR) from 0.72-4.32 kgday-1m-3, beyond which removal was not significant. For the identical loading conditions, in presence of phenol in the substrate along with carbohydrate, the COD removal was observed varying from 100-40% in the above organic loading range. The COD removal kinetics in presence of phenol also shows a decreasing trend compared to data obtained without the presence of phenol in wastewater that reveals biological inhibition. The experimental data were fitted in a simple plug flow model for evaluating the zero order, first order and Monod form of rate equations to evaluate the kinetics. It was found that Monod type rate equations combining a zero and first order rate expression is the best fit for the above hydraulic and organic loading that gives a best fit half velocity constant value of 35 mgL-1 (R2 = 0.9612).
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