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Inference on disk-jet connection of MAXI J1836–194 from spectral analysis with the TCAF solution

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Research in Astronomy and Astrophysics 2020年第3期20卷 28-41页

作者： Arghajit Jana Dipak Debnath Sandip KChakrabarti debjit Chatterjee Indian Centre for Space Physics 43 ChalantikaGaria St.Rd.Kolkata700084India

Galactic transient black hole candidate(BHC)MAXI J1836–194 was discovered on 2011 Aug30,by MAXI/GSC and Swift/*** source activity during this outburst continued for^3 months before entering into the quiescent *** again became active in March 2012 and continued for another^2 *** this paper,3-25 keV RXTE/PCA spectra from the 2011 outburst and 0.5-10.0 keV Swift/XRT data during its 2012 outburst are analyzed with the two-component advective flow(TCAF)model based fits files in *** calculate the X-ray contributions coming from jets/outflow using a newly developed method based on the deviation of the TCAF model *** also study the correlation between observed radio and estimated jet X-ray *** correlation indices(b)are found to be 1.79 and 0.61,when the 7.45 GHz Very Large Array(VLA)radio flux is correlated with the total X-ray and jet X-ray fluxes in 3-25 keV range *** has been found that the jet contributes in X-rays up to a maximum of 86%during its 2011 *** makes the BHC MAXI J1836–194 strongly jet dominated during the initial rising phase.

关键词： X-Rays:binaries stars individual:(MAXI J1836–194) stars:black holes accretion,accretion disks ISM:jets and outflows radiation:dynamics

Doxycycline blocks gastric ulcer by regulating matrix metalloproteinase-2 activity and oxidative stress

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World Journal of Gastroenterology 2011年第28期17卷 3310-3321页

作者： Laishram Pradeepkumar Singh Amartya Mishra debjit Saha Snehasikta Swarnakar Department of Physiology Drug Development Diagnostics and Biotechnology DivisionIndian Institute of Chemical Biology

AIM: To examine the effect of doxycycline on the activity of matrix metalloproteinases (MMPs) and oxidative stress in gastric tissues of rats following gastric ***: Gastric ulcers were generated in rats by administration of 70% ethanol,and activity of doxycycline was tested by administration 30 min prior to ***,the effect of doxycycline was tested in an indomethacin-induced gastric ulcer *** activities and expression of MMPs were examined by zymography and Western blot ***: Gastric injury in rats as judged by elevated ulcer indices following exposure to ulcerogen,either indomethacin or ethanol,was reversed significantly by ***-induced ulcerated gastric tissues exhibited about 12-fold higher proMMP-9 activity and about 5-fold higher proMMP-3 activity as compared to control ***,ethanol induced about 22-fold and about 6-fold higher proMMP-9 and proMMP-3 activities,respectively,in rat gastric *** proMMP-9 and MMP-3 activities were markedly decreased by doxycycline in ulcerogen treated rat gastric *** contrast,the reduced MMP-2 activity in ulcerated tissues was increased by doxycycline during ulcer *** the other hand,doxycycline inhibited significantly proMMP-9,-2 and -3 activities in *** addition,doxycycline reduced oxidative load in gastric tissues and scavenged H2O2 in *** results suggest a novel regulatory role of doxycycline on MMP-2 activity in addition to inhibitory action on MMP-9 and MMP-3 during prevention of gastric ***: This is the first demonstration of dual action of doxycycline,that is,regulation of MMP activity and reduction of oxidative stress in arresting gastric injury.

关键词： Doxycycline Extracellular matrix Matrix metalloproteinases Reactive oxygen species Tissue inhibitor of metalloproteinase

Accretion flow properties of XTE J1118+480 during its 2005 outburst

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Research in Astronomy and Astrophysics 2020年第11期20卷 222-230页

作者： Dipak Debnath debjit Chatterjee Arghajit Jana Sandip K.Chakrabarti Kaushik Chatterjee Indian Centre for Space Physics 43 ChalantikaGaria St.Rd.Kolkata700084India Physical Research Laboratory NavrangpuraAhmedabad 380009India

We study spectral and temporal properties of Galactic short orbital period transient black hole XTE J1118+480 during its 2005 outburst using archival data of RXTE PCA and HEXTE instruments in the combined energy range of 3−100 *** analysis with the physical two component advective flow(TCAF)model allows us to understand the accretion flow properties of the *** found that this outburst of XTE J1118+480 is an unconventional outburst as the source was only in the hard state(HS).Our spectral analysis suggests that during the entire outburst,the source was highly dominated by the low angular momentum sub-Keplerian halo *** the source was active in radio throughout the outburst,we make an effort to estimate X-ray contribution of jets to total observed X-ray emissions from the spectral analysis with the TCAF *** total X-ray intensity shows a similar nature of evolution as that of radio and jet X-ray *** allowed us to define this‘outburst’also as a jet dominated‘outburst’.Total X-ray flux is also found to subside when jet activity *** detailed spectral analysis also indicated that although the source was only in the HS during the outburst,in the late declining phase the spectrum became slightly softer due to the slow rise in the Keplerian disk rate.

关键词： X-Rays binaries-stars black holes-stars individual (XTE J1118+480)-accretion,accretion disks-ISM jets and outflows-radiation dynamics

Hepatoprotective activity of Macrothelypteris torresiana (Gaudich.) aerial parts against CCl4-induced hepatotoxicity in rodents and analysis of polyphenolic compounds by HPTLC

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Journal of Pharmaceutical Analysis 2017年第3期7卷 181-189页

作者： Sumanta Mondal debjit Ghosh Seru Ganapaty Surya Vamsi Gokul Chekuboyina Manisha Samal GITAM Institute of Pharmacy GITAM University Visakhapatnam-530045 Andhra Pradesh India Department of Chemistry GITAM Institute of ScienceGITAM UniversityVisakhapatnam-530045Andhra PradeshIndia

Macrothelypteris torresiana is a fern species belonging to the family Thelypteridaceae. The present study was conducted to evaluate hepatoprotective potential of ethanol extract from M. torresiana aerial parts(EEMTAP)and detect the polyphenolic compounds present in the extract using high performance thin layer chromatography(HPTLC). Hepatoprotective potential of EEMTAP were tested at doses of 300 and 600 mg/kg, per os(p.o.), on Wistar albino rats. The extract and silymarin treated animal groups showed significant decrease in activities of different biochemical parameters like serum glutamic oxaloacetic transaminase(SGOT), serum glutamate-pyruvate transaminase(SGPT), and alkaline phosphatase(ALP), which were elevated by carbon tetrachloride(CCl_4) intoxication. The levels of total bilirubin and total protein along with the liver weight were also restored to normalcy by EEMTAP and silymarin treatment. After CCl_4 administration, the levels of hepatic antioxidant enzymes such as glutathione(GSH) and catalase(CAT) were decreased whereas the level of hepatic lipid peroxidation(LPO) was elevated. The levels of these hepatic antioxidant enzymes were also brought to normalcy by EEMTAP and silymarin treatment. Histological studies supported the biochemical findings, and treatment with EEMTAP at doses of 300 and 600 mg/kg, p.o. was found to be effective in restoring CCl_4-induced hepatotoxicity in rats. A simple HPTLC analysis was conducted for the detection of polyphenolic compounds in EEMTAP, and the result revealed the presence of caffeic acid as phenolic acid and quercetin as flavonoid. The proposed HPTLC method is simple and concise and provides a good resolution of caffeic acid and quercetin from other constituents present in EEMTAP.

关键词： Macrothelypteris torresiana Hepatoprotective activity HPTLC fingerprint Caffeic acid Quercetin

Water Quality Parameters and Fish Biodiversity Indices as Measures of Ecological Degradation: A Case Study in Two Floodplain Lakes of India

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Journal of Water Resource and Protection 2010年第1期2卷 85-92页

作者： debjit Kumar MONDAL Anilava KAVIRAJ Subrata SAHA 不详

A three year study was conducted in two floodplain lakes to evaluate changes between seasonal variation of water quality parameter and finfish diversity indices. Samples of water and fish specimens were collected every month from three different stations of each lake to determine physico-chemical parameters of water and the finfish diversity indices. Split-plot and MANOVA designs, Multiplicative decomposition method and quadratic regression analysis were used to analyze the effects of the rate of changes between the parameters and sustainability of the lakes. The obtained results suggested that the impact of environmental change (e.g depth, conductivity, salinity of water etc.) on diversity indices was significant and should be taken into consideration when designing policies to increase the long-term sustainability of fishing activities in the lakes.

关键词： Baur Finfish Diversity Indices Multiplicative Decomposition Quadratic Regression

Accretion properties of MAXI J1813-095 during its failed outburst in 2018

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Research in Astronomy and Astrophysics 2021年第5期21卷 235-246页

作者： Arghajit Jana Gaurava K.Jaisawal Sachindra Naik Neeraj Kumari debjit Chatterjee KaushikChatterjee Riya Bhowmick Sandip KChakrabarti Hsiang-Kuang Chang Dipak Debnath Astronomy&Astrophysics Division Physical Research LaboratoryNavrangpuraAhmedabad 380009India National Space Institute Technical University of DenmarkElektrovej327-328DK-2800 LyngbyDenmark High Energy Astrophysics Indian Centre for Space PhysicsGaria St RoadKolkata 700084India Department of Physics Indian Institute of TechnologyGandhinagar 382355GujaratIndia Indian Institute of Astrophysics KoramangalaBangalore 560034India Department of Physics “National Tsing Hua University”Hsinchu 30013China

We present the results obtained from detailed timing and spectral studies of a black hole candidate MAXI J1813-095 using Swift,NICER,and NuSTAR observations during its 2018 *** timing behavior of the source is mainly studied by examining NICER light curves in the 0.5−10 keV *** did not find any signature of quasi-periodic oscillations in the power density spectra of the *** carry out spectral analysis with a combined disk blackbody&power law model,and physical two-component advective flow(TCAF)*** the combined disk blackbody&power-law model,we extracted thermal and non-thermal fluxes,photon index and inner disk *** also find evidence for weak reflection in the *** have tested the physical TCAF model on a broadband spectrum from NuSTAR and Swift/*** parameters like mass accretion rates,the size of Compton clouds and the shock strength are *** result affirms that the source remained in the hard state during the entire outburst which indicates a‘failed’*** estimate the mass of the black hole as 7.4±1.5M⊙from the spectral study with the TCAF *** apply the LAOR model for the Fe K line *** this,the spin parameter of the black hole is ascertained as a^(∗)>*** inclination angle of the system is estimated to be in the range of 28°−45°from the reflection *** find the source distance to be∼6 kpc.

关键词： X-Rays:binaries stars individual:(MAXI J1813-095) stars:black holes accretion,accretion disks–shock waves radiation:dynamics

An Analysis of Spatio-Temporal Trends of Land Surface Temperature in the Dhaka Metropolitan Area by Applying Landsat Images

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Journal of Geographic Information System 2021年第4期13卷 538-560页

作者： Musammat Shahinara Begum Sujit Kumar Bala AKM Saiful Islam GM Tarekul Islam debjit Roy Institute of Water and Flood Management (IWFM) Bangladesh University of Engineering and Technology (BUET) Dhaka Bangladesh Survey and Investigation Division Irrigation Wing Bangladesh Agricultural Development Corporation (BADC) Dhaka Bangladesh Irrigation and Water Management Division Bangladesh Rice Research Institute (BRRI) Gazipur Bangladesh

Land surface temperature (LST) is a basic determinant of the global thermal behavior of the Earth surface. LST is a vital consideration for the appraisal of gradual thermal change for urban areas to examine the strength of the thermal intensity of the surface of urban heat island (SUHI) and to see how hot the surface of the Earth would be in a particular location. In this respect, the most developed urban city like Dhaka Metropolitan Area (DMA), Bangladesh is considered for estimation of LST, and Normalized Difference Vegetation Index (NDVI) changes trend in more developed and growing developing areas. The focus of this study is to find out the critical hotspot zones for further instantaneous analysis between these two types of areas. The trends of long-term spatial and temporal LST and NDVI are estimated applying Landsat images-Landsat 5-TM and Landsat OLI_TIRS-8 for the period of 1988 to 2018 for DMA and for developed and growing developing areas during the summer season like for the month of March. The supervised classification was used to estimate the land cover categories and to generate the LST trends maps of the different percentiles of LSTs over time using the emissivity and effective at sensor brightness temperature. The study found the change in land cover patterns by different LST groups based on 50th, 75th, and 90th percentile where the maximum LST for the whole DMA went up by 2.48°C, 1.01°C, and 3.76°C for the months of March, April, and May, respectively for the period of 1988 to 2018. The highest difference in LST was found for the most recently developed area. The moderate change of LST increased in the built-up areas where LST was found more sensitive to climate change than the growing developed areas. The vegetation coverage area decreased by 6.74% in the growing, developing areas compared to the developed areas

关键词： Land Surface Temperature Surface Urban Heat Island Urban Thermal Environment NDVI Change Vegetation Coverage Change