Can holographic dark energy increase the mass of the wormhole?     

Surajit Chattopadhyay  Davood Momeni  Aziza Altaibayeva  Ratbay Myrzakulov 《Astrophysics and Space Science》2015,356(1):195-204

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Modified QCD ghost f ( T,T G ) gravity     

Abdul Jawad  Shamaila Rani  Surajit Chattopadhyay 《Astrophysics and Space Science》2015,357(2):1-7

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Torsional wave propagation in non‐homogeneous layer between non‐homogeneous half‐spaces     

A. Chattopadhyay  S. Gupta  Pato Kumari  V. K. Sharma 《国际地质力学数值与分析法杂志》2013,37(10):1280-1291

The study of surface wave in a layered medium has their possible application in geophysical prospecting. In the present work, dispersion equation for torsional wave in an inhomogeneous isotropic layer between inhomogeneous isotropic half‐spaces has been derived. Two cases are discussed separately for torsional wave propagation in inhomogeneous layer between homogeneous and non‐homogeneous half‐spaces, respectively. Further, two possible modes for torsional wave propagation are obtained in case of inhomogeneous layer sandwiched between non‐homogeneous half‐spaces. Closed form solutions for displacement in the layer and half‐spaces are obtained in each case. The study reveals that the layer width, layer inhomogeneity, frequency of inhomogeneity, as well as inhomogeneity in the half‐space has significant effect on the propagation of torsional surface waves. Displacement and implicit dispersion equation for torsional wave velocities are expressed in terms of Heun functions and their derivatives. Effects of inhomogeneity on torsional wave velocity are also discussed graphically by plotting the dimensionless phase velocity against dimensionless and scaled wave number for different values of inhomogeneity parameter. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Distribution and generic composition of culturable marine actinomycetes from the sediments of Indian continental slope of Bay of Bengal   总被引：3，自引：0，他引：3  

Surajit Das  P. S. Lyla  S. Ajmal Khan 《中国海洋湖沼学报》2008,26(2):166-177

Actinomycetes population from continental slope sediment of the Bay of Bengal was studied. Samples were collected during two voyages of FORV Sagar Sampada in 2004 （May-June） and 2005 （July） respectively from 11 transects （each transect had ca. 200 m, 500 m, and 1 000 m depth stations）. The physicochemical parameters of overlying water, and sediment samples were also recorded. The actinomycete population ranged from 5.17 to 51.94 CFU/g dry sediment weight and 9.38 to 45.22 CFU/g dry sediment weight during the two cruises respectively. No actinomycete colony was isolated from stations in 1 000 m depth. Two-way analysis of variance showed significant variation among stations （ANOVA two-way, P〈0.05）, but no significance was found between the two cruises （ANOVA two-way, P〈0.05）. Populations in stations in 500 m depth in both cruises were higher than that of 200 m depth stations with statistically insignificant difference （ANOVA two-way, P〉0.05）. Three actinomycetes genera were identified. Streptomyces was found to be the dominating one in both the cruises, followed by Micromonospora, and Actinomyces. The spore of Streptomyces isolates showed the abundance in spiral spore chain. Spore surface was smooth. Multiple regression analysis revealed that the influencing physico-chemical factors were sediment pH, sediment temperature, TOC, porosity, salinity, and pressure. The media used in the present study was prepared with seawater. Thus, they may represent an autochthonous marine flora and deny the theory of land runoff carriage into the sea for adaptation to the salinity of the seawater and sediments.  相似文献   

Acceleration of the Universe in presence of tachyonic field     

Surajit Chattopadhyay  Ujjal Debnath  Goutami Chattopadhyay 《Astrophysics and Space Science》2008,314(1-3):41-44

In this letter, we have assumed that the Universe is filled in tachyonic field with potential, which gives the acceleration of the Universe. For certain choice of potential, we have found the exact solutions of the field equations. We have shown the decaying nature of potential. From recently developed statefinder parameters, we have investigated the role of tachyonic field in different stages of the evolution of the Universe.  相似文献   

Geologic framework and isotope tracing of the arsenious Quaternary Aquifer of the southwestern North Bengal Plain,West Bengal,India   总被引：2，自引：2，他引：0  

Surajit Chakraborty  Pradip Kumar Sikdar 《Environmental Earth Sciences》2009,59(4):723-736

The aim of the paper is to understand the geological control of groundwater, the recharge sources, the relative age of groundwater and the interaction between surface water and groundwater of the southwestern part of North Bengal Plain in the alluvium filled gap between the Rajmahal hills on the west and the Garo hills on the east. The area is covered by Quaternary alluvia of two different ages, viz. the Older Alluvium and the Newer Alluvium. The Older Alluvium of Pleistocene age is made up of argillaceous bed reddish brown in color and interspread with ‘kankar’ and laterite debris and the Newer Alluvium is dark, loosely compacted and has a high moisture content. A hydrostarigraphic model of the top 120 m geological column has been built by direct field observation, constructing Fence diagram, lithofacies and isotope analyses. The model indicates an oscillating environment of deposition of sediments from bottom to top with oxidizing at the bottom followed by reducing and then oxidizing environment at the top. The hydrogeochemistry of groundwater also suggests a predominantly reducing condition of the aquifer with high HCO₃ ⁻, low SO₄ ²⁻ and NO₃ ⁻ concentrations. The shallow groundwater at places contains heavy metals such as copper, cadmium, manganese, iron, chromium and arsenic. The δ¹⁸O and tritium values of groundwater are within the range of monsoon precipitation composition which indicates that groundwater is probably recharged primarily from precipitation. The plots of δ¹⁸O and δD show slight deviation from the Local Mean Water Lines suggesting that some evaporation of rainfall occurs prior to or during infiltration. Therefore groundwater occurs under unconfined condition. Lithofacies analysis indicates that the sediments below the depth of 40 m are the potential water bearing formation. Depletion or enrichment of δ¹⁸O and δD with depth was not observed and tritium content is also similar at various depths indicating possibility of mixing of groundwater from various depths due to pumping which may lead to contamination of the deeper aquifer by heavy metals and arsenic.  相似文献   

Rayleigh waves in liquid layer resting over an initially stressed orthotropic half-space under self-weight     

Sanjeev Anand Sahu  Soniya Chaudhary  Pradeep Kumar Saroj  Amares Chattopadhyay 《Arabian Journal of Geosciences》2017,10(5):120

The study of surface waves (Rayleigh wave) finds their virtuous applications in a numerous geological and geophysical fields including water, oil, gas, and other subsurface geological probing and exploration. The present paper efforts to investigate the influence of initial stress, Earth magnetism, and gravity on propagation of Rayleigh waves. Considered model is consist of a liquid layer lying over a magnetoelastic orthotropic half-space under self-weight and initial stress. Method of separation of variable is used to solve the equation of motion. Solutions of governing equations are obtained in terms of displacement. Frequency relation for Rayleigh wave has been obtained and matched with classical Rayleigh wave equation. In addition to classical case, some existing results have been deduced as particular case of the present study. Obtained results have been shown through numerical illustrations. It is found that the considered parameters (initial stress, Earth magnetism, and gravity) have prominent effect on phase velocity of Rayleigh wave. Graphical representations have been made to exhibit the velocity profile of Rayleigh waves for different cases with the help of MATHEMATICA. The present study may be useful for seismologists and engineers who are concern with applications of wave propagation in magnetoelastic orthotropic medium.  相似文献   

Potential predictability of wet/dry spells transitions during extreme monsoon years: optimism for dynamical extended range prediction     

A. K. Sahai  S. Sharmila  R. Chattopadhyay  S. Abhilash  S. Joseph  N. Borah  B. N. Goswami  D. S. Pai  A. K. Srivastava 《Natural Hazards》2017,88(2):853-865

The duration and extreme fluctuations of prolonged wet or dry spells associated with intraseasonal variability during extreme monsoon have devastating impacts on agrarian-based economy over Indian subcontinent. This study examines the potential predictability limit of intraseasonal transitions between rainy to non-rainy phases (i.e., active to break phases) or vice versa over central Indian region during extreme monsoon using very high-resolution (0.25° × 0.25°) daily rainfall datasets. The present study reveals that the transitions from both active to break and break to active conditions are more predictable by ~8 days during the weak monsoon (WM) years compared to the strong monsoon (SM) years. Such asymmetric behavior in the limit of predictability could be linked to the distinct differences in the large-scale seasonal mean background instability during SM and WM years. The achievability of such predictability is further evaluated in a state-of-the-art climate model, the climate forecast system (CFSv2). It is demonstrated that the observed asymmetry in predictability limit could be reproducible in the CFSv2 model, irrespective of its spatial resolution. This study provides impetus for useful dynamical prediction of wet/dry spells at extended range during the extreme monsoon years.  相似文献   

Multivariate forecast of winter monsoon rainfall in India using SST anomaly as a predictor: Neurocomputing and statistical approaches     

Goutami Chattopadhyay  Surajit Chattopadhyay  Rajni Jain 《Comptes Rendus Geoscience》2010,342(10):755-765

In this article, the complexities in the relationship between rainfall and sea surface temperature (SST) anomalies during the winter monsoon over India were evaluated statistically using scatter plot matrices and autocorrelation functions. Linear, as well as polynomial trend equations were obtained, and it was observed that the coefficient of determination for the linear trend was very low and it remained low even when polynomial trend of degree six was used. An exponential regression equation and an artificial neural network with extensive variable selection were generated to forecast the average winter monsoon rainfall of a given year using the rainfall amounts and the SST anomalies in the winter monsoon months of the previous year as predictors. The regression coefficients for the multiple exponential regression equation were generated using Levenberg-Marquardt algorithm. The artificial neural network was generated in the form of a multilayer perceptron with sigmoid non-linearity and genetic-algorithm based variable selection. Both of the predictive models were judged statistically using the Willmott's index, percentage error of prediction, and prediction yields. The statistical assessment revealed the potential of artificial neural network over exponential regression.  相似文献   

Reflection and refraction of waves at the interface of an isotropic medium over a highly anisotropic medium     

A. Chattopadhyay  Rajneesh 《Acta Geophysica》2006,54(3):239-249

In this paper, we have considered the reflection and refraction of a plane wave at an interface between two half-spaces. The lower half-spaces is composed of highly anisotropic triclinic crystalline material and the upper half-space is homogeneous and isotropic. It has been assumed that due to incidence of a plane quasi-P (qP) wave, three types of waves, namely, quasi-P (qP), quasi-SV (qSV) and quasi-SH (qSH), will be generated in the lower half space whereas P and S waves will be generated in the upper half space. The phase velocities of all the quasi waves have been calculated. It has been assumed that the direction of particle motion is neither parallel nor perpendicular to the direction of propagation. Some specific relations have been established between directions of motion and propagation, respectively. The expressions for reflection coefficients of qP, qSV, qSH and refracted coefficients of P and SV waves are obtained. Results of reflection and refraction coefficients are presented.  相似文献