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Polarized Debye Sheath in Degenerate Plasmas

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Communications in Theoretical Physics 2019年第11期71卷 1341-1345页

作者： M.Shahmansouri A.P.misra Department of Physics Faculty of ScienceArak UniversityArakP.O.Box 38156-8-8349Iran Department of Mathematics Siksha BhavanaVisva-Bharati(A Central University)Santiniketan-731235India

The force on a charged dust grain in a plasma due to polarization of thermal ions and degenerate electrons around the grain is derived in the limits of weakly relativistic and ultra-relativistic degeneracy of electrons. It is found that in both these cases, the magnitude of the polarization force is enhanced compared to that in classical plasmas. The influence of this force on dust-acoustic(DA) modes is examined and discussed. It is shown that the DA wave frequency in degenerate plasmas is significantly reduced compared to the classical DA mode.

关键词： degenerate plasma polarization force dust acoustic waves

Peristaltic transport of rheological fluid:model for movement of food bolus through esophagus

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Applied Mathematics and Mechanics(English Edition) 2012年第3期33卷 315-332页

作者： J.C.misra S.MAITI Department of Mathematics Institute of Technical Education and ResearchSiksha 'O' Anusandhan UniversityBhubaneswar 751030India School of Medical Science and Technology & Center for Theoretical Studies Indian Institute of TechnologyKharagpur 721302India

Fluid mechanical peristaltic transport through esophagus is studied in the paper. A mathematical model has been developed to study the peristaltic transport of a rheological fluid for arbitrary wave shapes and tube lengths. The Ostwald-de Waele power law of a viscous fluid is considered here to depict the non-Newtonian behaviour of the fluid. The model is formulated and analyzed specifically to explore some important information concerning the movement of food bolus through esophagus. The analysis is carried out by using the lubrication theory. The study is particularly suitable for the cases where the Reynolds number is small. The esophagus is treated as a circular tube through which the transport of food bolus takes place by periodic contraction of the esophageal wall. Variation of different variables concerned with the transport phenomena such as pressure, flow velocities, particle trajectory, and reflux is investigated for a single wave as well as a train of periodic peristaltic waves. The locally variable pressure is seen to be highly sensitive to the flow index ＂n＂. The study clearly shows that continuous fluid transport for Newtonian/rheological fluids by wave train propagation is more effective than widely spaced single wave propagation in the case of peristaltic movement of food bolus in the esophagus.

关键词： non-Newtonian fluid food bolus esophagus peristaltic transport flow reversal single wave wave train particle trajectory

AstroSat observation of GX 5–1: spectral and timing evolution

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Research in Astronomy and Astrophysics 2019年第8期19卷 81-92页

作者： Yashpal Bhulla Ranjeev misra JSYadav SNA Jaaffrey Pacific Academy of Higher Education and Research University Udaipur-313003India Inter-University Center for Astronomy and Astrophysics Pune-411007India Tata Institute of Fundamental Research Mumbai-400005India

We report on the first analysis of an AstroSat observation of the Z-source GX 5–1 on 2017 February 26-27. The hardness-intensity plot reveals that the source traced out the horizontal and normal branches. The 0.8-20 keV spectra from simultaneous SXT and LAXPC data at different locations of the hardness-intensity plot can be described well by disk emission and a thermal Comptonized component. The ratio of the disk flux to the total flux, i.e., the disk flux ratio, increases monotonically along the horizontal branch to the normal one. Thus, the difference between the normal and horizontal branches is that in the normal branch, the disk dominates the flux while in the horizontal one it is the Comptonized component which dominates. The disk flux scales with the inner disk temperature as Tin5.5 and not as Tin4 , suggesting that either the inner radius changes dramatically or that the disk is irradiated by the thermal component changing its hardness factor. The power spectra reveal a quasi-periodic oscillation(QPO) whose frequency changes from 30 Hz to 50 Hz. The frequency is found to correlate well with the disk flux ratio. In the 3-20 keV LAXPC band, the r.m.s. of the QPO increases with energy(r.m.s. ∝ E0.8), while the harder X-rays seem to lag the soft ones with a time-delay of milliseconds. The results suggest that the spectral properties of the source are characterized by the disk flux ratio and that the QPO has its origin in the corona producing the thermal Comptonized component.

关键词： accretion accretion disc stars:neutron star X-rays:binaries X-rays:individual:GX 5–1

Evaluating location specific strain rates, temperatures,and accumulated strains in friction welds through microstructure modeling

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Defence Technology（防务技术） 2018年第2期14卷 83-92页

作者： Javed Akram Prasad Rao Kalvala Vikas Jindal Mano misra Dept. of Metallurgical Engineering University of Utah Dept. of Metallurgical Engineering Indian Institute of Technology(BHU)

A microstructural simulation method is adopted to predict the location specific strain rates, temperatures, grain evolution, and accumulated strains in the Inconel 718 friction welds. Cellular automata based 2D microstructure model was developed for Inconel 718 alloy using theoretical aspects of dynamic recrystallization. Flow curves were simulated and compared with experimental results using hot deformation parameter obtained from literature work. Using validated model, simulations were performed for friction welds of Inconel 718 alloy generated at three rotational speed i.e., 1200, 1500, and1500 RPM. Results showed the increase in strain rates with increasing rotational speed. These simulated strain rates were found to match with the analytical results. Temperature difference of 150 K was noticed from center to edge of the weld. At all the rotational speeds, the temperature was identical implying steady state temperature(0.89 T_m) attainment.

关键词： Microstructure modeling Dynamic recrystallization Friction welding Inconel 718 EBSD Hot deformation Strain map

Soil nitrogen balance assessment and its application for sustainable agriculture and environment

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Science China(Life Sciences) 2005年第Z2期48卷 843-855页

作者： Rabindra Nath Roy Ram Vimal misra Land and Water Development Division FAO Rome 00100Italy

Soil nitrogen balance assessment (SNBA) serves as an effective tool for estimating the magnitude of nitrogen loss/gain of the agro-eco systems and to appraise their sustainability. SNBA brings forth awareness of soil fertility problems, besides providing information relating to the resultant release of nitrogen into the environment consequent to agricultural practices. Quantitative information relating to nitrogen escape into the environment through such exercises can be gainfully utilized for identification of causative factors, enhancing fertilizer use efficiency and formulating programmes aimed at plugging N leakages. An overview of nitrogen balance approaches and methodologies is presented. A deeper understanding and insight into the agro-eco systems provided by the SNBA exercises can lay the basis for the formulation of effective agronomic interventions and policies aimed at promoting sustainable agriculture and a benign environment.

关键词： nitrogen balance soil fertility sustainable agriculture nutrient flows and macro meso and micro levels

Parenteral nanosuspensions:a brief review from solubility enhancement to more novel and specific applications

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Acta Pharmaceutica Sinica B 2018年第5期8卷 733-755页

作者： Eknath Ahire Shreya Thakkar Mahesh Darshanwad Manju misra Department of Pharmaceutics National Institute of Pharmaceutical Education and Research (NIPER)

Advancements in in silico techniques of lead molecule selection have resulted in the failure of around 70% of new chemical entities(NCEs). Some of these molecules are getting rejected at final developmental stage resulting in wastage of money and resources. Unfavourable physicochemical properties affect ADME profile of any efficacious and potent molecule, which may ultimately lead to killing of NCE at final stage. Numerous techniques are being explored including nanocrystals for solubility enhancement purposes. Nanocrystals are the most successful and the ones which had a shorter gap between invention and subsequent commercialization of the first marketed product. Several nanocrystal-based products are commercially available and there is a paradigm shift in using approach from simply being solubility enhancement technique to more novel and specific applications. Some other aspects in relation to parenteral nanosuspensions are concentrations of surfactant to be used, scalability and in vivo fate. At present, there exists a wide gap due to poor understanding of these critical factors,which we have tried to address in this review. This review will focus on parenteral nanosuspensions,covering varied aspects especially stabilizers used, GRAS(Generally Recognized as Safe) status of stabilizers, scalability challenges, issues of physical and chemical stability, solidification techniques to combat stability problems and in vivo fate.

关键词： Parenteral Nanosuspension Stabilizer In vivo fate Solidification Scalability

Flow of a micropolar fluid in a micro-channel under the action of an alternating electric field: Estimates of flow in bio-fluidic devices

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Journal of Hydrodynamics 2015年第3期27卷 350-358页

作者： misra J.C. CHANDRA S. HERWIG H. Centre for Healthcare Science and Technology Indian Institute of Engineering Science and Technology Department of Physics Sabang S. K. Mahavidyalaya Vidyasagar University Institute of Thermo-Fluid Dynamics Technische Universitat Hamburg-Harburg

The paper is devoted to a study of the electro-osmotic flow of a micropolar bio-fluid, when the flow takes place between two plates that are in a state of periodic vibrations. Considering blood as a micropolar fluid, it is found that the amplitude of oscillation of the microparticles of blood increases when the micropolar effect is pronounced more and more and that a rise in DebyeHtickel parameter enhances both the velocity and microrotation gradient. The results provide guidelines for the improvement of design of bio-sensing and micro-fluidic devices. The study leads to the conclusion that electrical double layers formed in the vicinity of the wall can significantly alter the flow dynamics of physiological fluids in micro-bio-fluidic devices.

关键词： microrotation Electro-osmotic flow Debye-Hiickel parameter micropolar fluid

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

Comprehensive spectral analysis of Cyg X-1 using RXTE data

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Research in Astronomy and Astrophysics 2012年第10期12卷 1427-1438页

作者： Rizwan Shahid Ranjeev misra S.N.A.Jaaffrey Department of Physics M.L.Sukhadia UniversityUdaipur-313001India Inter University Centre for Astronomy and Astrophysics Pune-411007India

We analyze a large number （〉 500） of pointed Rossi X-Ray Timing Explorer （RXTE） observations of Cyg X- 1 and model the spectrum of each one. A subset of the observations for which there is a simultaneous reliable measure of the hardness ratio by the All Sky Monitor shows that the sample covers nearly all the spectral shapes of Cyg X-1. Each observation is fitted with a generic empirical model consisting of a disk black body spectrum, a Comptonized component whose input photon shape is the same as the disk emission, a Gaussian to represent the iron line and a reflection feature. The relative strength, width of the iron line and the reflection parameter are in general correlated with the high energy photon spectral index F. This is broadly consistent with a geometry where for the hard state （low F ~ 1.7） there is a hot in- ner Comptonizing region surrounded by a truncated cold disk. The inner edge of the disk moves inwards as the source becomes softer till finally in the soft state （high F 〉 2.2） the disk fills the inner region and active regions above the disk produce the Comptonized component. However, the reflection parameter shows non-monotonic behavior near the transition region （F ~ 2）, which suggests a more complex geometry or physical state of the reflector. In addition, the inner disk temperature, during the hard state, is on average higher than in the soft one, albeit with large scatter. These inconsistencies could be due to limitations in the data and the empirical model used to fit them. The flux of each spectral component is well correlated with F, which shows that unlike some other black hole systems, Cyg X- 1 does not show any hysteresis be- havior. In the soft state, the flux of the Comptonized component is always similar to the disk one, which confirms that the ultra-soft state （seen in other brighter black hole systems） is not exhibited by Cyg X-1. The rapid variation of the Compton amplifica- tion factor with F naturally explains the absence of spec

关键词： accretion accretion disks -- X-rays: binaries