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The kilosecond variability of X-ray sources in nearby galaxies

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Research in Astronomy and Astrophysics 2013年第12期13卷 1445-1454页

作者： Soma mandal Ranjeev Misra Gulab C.Dewangan Department of Physics Taki Government College Inter-University Centre for Astronomy and Astrophysics

Chandra observations of 17 nearby galaxies were analyzed and 166 bright sources with X-ray counts 〉 100 were chosen for temporal analysis. Fractional root mean square （rms） variability amplitudes were estimated for light curves, binned at 4 kilosecond （ks）, with length 〈 40 ks. While there are nine ultra-luminous X- ray sources （ULXs） with unabsorbed luminosity （in the 0.3-8.0 keV band） L 〉 1039 erg s-1 in the sample for which the fractional rms variability is constrained to be 〈 10%, only two of them show variability. One of the variable ULXs exhibits a secular transition and has an ultra-soft spectrum with temperature - 0.3 keV while the other is a rapidly varying source in NGC 0628, which has previously been com- pared to the Galactic microquasar GRS 1915＋105. These results seem to indicate that ULXs are typically not highly variable on ks timescales, except for some ultra-soft ones. Among the relatively low luminosity sources （L - 10^38 erg s-1）, we find five of them to be variable. Apart from an earlier known source in NGC 1569, we identify a source in NGC 2403 that exhibits persistent high amplitude fluctuations. In general, the variability of the sources does not seem to be correlated with hardness, which indicates that they may not be due to variations in any absorbing material, but instead could reflect instabilities in the inner accretion disk.

关键词： galaxies: general --X-rays: binaries

Water Wave Scattering by a Nearly Circular Cylinder Submerged Beneath an Ice-cover

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Journal of Marine Science and Application 2015年第1期14卷 69-75页

作者： Rumpa Chakraborty Birendra Nath mandal Physics and Applied Mathematics Unit Indian Statistical Institute Kolkata 700108 India

Assuming linear theory, the two-dimensional problem of water wave scattering by a horizontal nearly circular cylinder submerged in infinitely deep water with an ice cover modeled as a thin-elastic plate floating on water, is investigated here. The cross-section of the nearly circular cylinder is taken as r=a（1＋δC（θ））, where a is the radius of the corresponding circular cross-section of the cylinder, δ is a measure of small departure of the cross-section of the cylinder from its circularity and C（θ） is the shape function. Using a simplified perturbation technique the problem is reduced to two independent boundary value problems up to first order in δ. The first one corresponds to water wave scattering by a circular cylinder submerged in water with an ice-cover, while the second problem describes wave radiation by a submerged circular cylinder and involves first order correction to the reflection and transmission coefficients. The corrections are obtained in terms of integrals involving the shape function. Assuming a general Fourier expansion of the shape function, these corrections are evaluated approximately. It is well known that normally incident wave trains experience no reflection by a circular cylinder submerged in infinitely deep water with an ice cover. It is shown here that the reflection coefficient also vanishes up to first order for some particular choice of the shape function representing a nearly circular cylinder. For these cases, full transmission occurs, only change is in its phase which is depicted graphically against the wave number in a number of figures and appropriate conclusions are drawn.

关键词： water wave scattering ice-cover nearly circular cylinder shape function reflection coefficient transmission coefficient

Serologic evidence of human leptospirosis in and around Kolkata,India:A clinico-epidemiological study

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Asian Pacific Journal of Tropical Medicine 2011年第12期4卷 1001-1006页

作者： Manisha Debmandal Shyamapada mandal Nishith Kumar Pal Department of Bacteriology and Serology Calcutta School of Tropical MedicineC.R.AvenueKolkata-700073India Department of Physiology and Biophysics KPC Medical College and HospitalKolkata-700032India Department of Zoology Gurudas CollegeNarkeldangaKolkata-700054India Department of Microbiology Institute of Postgraduate Medical Education and ResearchKolkata-700020India

Objective:To investigate the prevalence of leptospirosis among patients from within and outside ***,attending the Calcutta School of Tropical Medicine,for treatment during August 2002 to August ***:The leptospirosis cases were determined on the basis of clinical, epidemiological,and biochemical factors,and were tested for leptospiral antibodies using IgM *** samples with absorbance ratio≥1.21 were interpreted as ***:The commonest presentation involved fever,headache and *** male-female ratio was 61:46.A total of 65(64.20%) cases had abnormal liver and renal functions respectively,and 57.1% had both the *** highest incidence(75.35.04%) was recorded in SeptemberOctober followed by July-August(53.24.77%).The reactive cases had absorbance ratios between 1.21 and *** 53 showed equivocal result,while IgM non reactivity were seen in 90 patients (absorbance ratios 0.10-0.90).The patients responded to treatment with parenteral antibiotics, penicillin,ceftriaxone and cefotaxime;follow up did not reveal case ***:The cardinal signs of leptospirosis help in making clinical diagnosis,but in any hyper-endemic situation any patient reporting with acute lever and signs of pulmonary,hepatic or renal involvement should be suspected to have leptospirosis and investigated *** awareness,and early diagnosis and treatment,can reduce mortality due to leptospirosis.

关键词： Human leptospirosis IgM ELISA Clinico-epidemiological study Kolkata

Numerical simulation of physiologically relevant pulsatile flow of blood with shear-rate-dependent viscosity in a stenosed blood vessel

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International Journal of Biomathematics 2018年第6期11卷 129-150页

作者： Subrata Mukhopadhyay Mani Shankar mandal Swati Mukhopadhyay Department of MathematicsAcharya P. C. Roy Govt. College Siliguri W.B. India Department of MathematicsG.G.D. C at Kalna-I Purba Bardhaman-713405 W.B. India Department of MathematicsThe University of Burdwan Burdwan-713104 W.B. India

Pulsatile flow of blood in a blood vessel having time-dependent shape （diameter） is inves-tigated numerically in order to understand some important physiological phenomena in arteries. A smooth axi-symmetric cosine shaped constriction is considered. To mimic the realistic situation as far as possible, viscosity of blood is taken to be non-uniform, a shear-thinning viscosity model is considered and a physiologically relevant pulsatile flow is introduced. Taking advantage of axi-symmetry in the proposed problem, the stream function-vorticity formulation is used to solve the governing equations for blood flow. Effect of different parameters associated with the problem on the flow pattern has been investigated and disparities from the Newtonian case are discussed in detail.

关键词： Pulsatile flow stenosis stream function-vorticity method finite differencete chnique non-Newtonian fluid fluid-structure interaction wall shear stress flow separation.

Advancement of noble metallic nanoparticles in agriculture: A promising future

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Pedosphere 2023年第1期33卷 116-128页

作者： Paulami DAM Matthews LPARET Rittick MONDAL Amit Kumar mandal Chemical Biology Laboratory Department of SericultureRaiganj UniversityNorth DinajpurWest Bengal 733134India University of Florida Department of Plant PathologyQuincy 32351USA Centre for Nanotechnology Sciences Raiganj UniversityNorth DinajpurWest Bengal 733134India

Since the last decades,nanotechnology has gained the attention of researchers in the field of plant *** characteristics of nanoparticles are reliant on their shape and *** involving noble metallic nanoparticles(NMNPs)offer novel technologies to boost agricultural productivity and minimize conventional pesticide *** application of nanoparticles as nanofertilizer improves plant growth and enhances nutrient uptake *** metallic nanoparticles act as antimicrobial agents against multidrug-resistant pathogens and provide protection to *** and nanodevices are utilized in diverse agro-based areas such as plant disease diagnosis and nanoparticle-based material *** studies have focused on negative impacts such as toxicity and environmental threats posed by *** the effects of NMNPs on agriculture is critical for the assessment of their safety and the impending environmental risks to biodiversity and human ***,we summarize the advances of NMNPs towards revolutionizing modern agricultural applications and the recent trends in sustainable precision agriculture.

关键词： antimicrobial agents multidrug-resistant pathogens nanobiosensors nanofertilizers plant protection

Effect of size on momentum distribution of electrons around vacancies in NiO nanoparticles

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Chinese Physics B 2015年第4期24卷 296-299页

作者： Anjan Das Atis Chandra mandal P.M.G.Nambissan Department of Physics A.P.C.Roy Government College Department of Physics University of Burdwan Applied Nuclear Physics Division Saha Institute of Nuclear Physics

Very small nickel oxide nanoparticles were prepared by a sol-gel procedure using nickel nitrate hexahydrate and ammonium hydroxide as precursors. The particles are in the range of 5 nm-11 rim. The x-ray diffraction （XRD） crystallography and high resolution transmission electron microscopy （HRTEM） were employed to characterize the samples. They were found to be polycrystalline in nature and fcc （NaCl-type） in structure, with the lattice parameter varying with annealing temperature. HRTEM pictures show that the as-prepared samples are hexagonal in shape. Positron annihilation spectroscopy was used to investigate the Doppler-broadened spectra of the samples. The S and W parameters revealed that the chemical surroundings and momentum distribution of the vacancy clusters vary with crystallite size.

关键词： nanoparticles semiconductor defect cluster positron annihilation sol-gel

Double diffusive magnetohydrodynamic heat and mass transfer of nanofluids over a nonlinear stretching/shrinking sheet with viscous-Ohmic dissipation and thermal radiation

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Propulsion and Power Research 2017年第1期6卷 58-69页

作者： Dulal Pal Gopinath mandal Department of Mathematics Institute of ScienceVisva-Bharati UniversitySantiniketanWest Bengal 731235India Siksha Satra Visva-BharatiSriniketanWest Bengal 731236India

The study of magnetohydrodynamic(MUD)convective heat and mass transfer near a stagnation-point flow over stretching/shrinking sheet of nanofluids is presented in this paper by considering thermal radiation,Ohmic heating,viscous dissipation and heat source/sink parameter ***-similarity method is adopted for the governing basic equations before they are solved numerically using Runge-Kutta-Fehlberg method using shooting *** numerical results are validated by comparing the present results with previously published *** focus of this paper is to study the effects of some selected governing parameters such as Richardson number,radiation parameter,Schimdt number,Eckert number and magnetic parameter on velocity,temperature and concentration profiles as well as on skin-friction coefficient,local Nusselt number and Sherwood number.

关键词： Nanofluids Magnetohydrodynamics Heat and mass transfer Thermal radiation Convection Ohmic dissipation

Extraction of locked-up coal by strengthening of rib pillars with FRP--A comparative study through numerical modelling

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International Journal of Mining Science and Technology 2017年第2期27卷 261-267页

作者： Das Arka Jyoti mandal Prabhat Kumar Ghosh Chandra Nath Sinha Amalendu CSIR-Central Institute of Mining and Fuel Research Dhanbad 826001India

In some of the coalfields in India, coal seams are only developed but no extraction of pillars is possible due to the presence of surface or sub-surface structures and also non-availability of stowing materials which leads to huge amounts of coal being locked-up underground. Spontaneous heating and fire, accumulation of poisonous gases, severe stability issues leading to unsafe workings and environmental hazards are the major problems associated with the developed coal pillars. So, there is a pressing need for a technology for the mining industry to extract the huge amount of coal locked-up under different constraints. In this study, the locked-up coal is proposed to be extracted by artificially strengthening the rib pillars. The detailed comparative study is carried out to know the increase of extraction percentage of locked-up coal by strengthening the rib pillars with FRP. Extraction methodology is designed and studied through numerical modelling for its stability analysis to evaluate its suitability of application in underground.

关键词： Locked-up coal Confined core Yield criterion Strengthened rib pillar Strain softening

Forest landscape and its ecological quality:A stepwise spatiotemporal evaluation through patch-matrix model in Jhargram District,West Bengal State,India

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Regional Sustainability 2021年第2期2卷 164-176页

作者： Mrinmay mandal Nilanjana Das Chatterjee Department of Geography Vidyasagar UniversityMidnaporeWest Bengal721102India

Landscape conversion becomes a continuous process in a natural landscape for any strategic *** a forest landscape mosaic,the conversion from non-forest land to forest land implies a constructive *** bio-geographic processes are enriched and developed when the land was converted to forest land in a given landscape *** present study evaluated how the increased forest cover improves the ecological quality of forest in Jhargram District of West Bengal State,India,from 1985 to *** quality of forests includes dominance,fragmentation and connectivity,which are the basis ecological indicators of habitat *** address this issue,we extracted forest cover maps of 1985 and 2015 from land use/land cover classification.A grid framework was overlaid on these forest cover maps for patch-matrix model *** landscape ecological indices were used for the measurements of forest landscape quality in 1985 and *** a simple linear regression model was used to compare the ***,forest cover increased in Jhargram District from 1985 to *** comparison of measurement indices depicts that although only a small amount of land was changed into forest land in the study area,this small change has greatly improved the structural compositional quality of the forest *** with 1985,the forest land area increased by about 6930.56 hm^(2) in *** increased forest cover improved the basic landscape ecological characters,such as inter patch connectivity,forest core area,forest habitat dependence,forest habitat dominance and forest edge *** a result,the ecosystem function in Jhargram District has been improved,which again attracts wildlife and enriches biodiversity.

关键词： Forest cover Landscape quality Patch-matrix model Ecological index Forest fragmentation Biodiversity