Arsenate sorption by reduced and reoxidised rice soils under the influence of organic matter amendments     

A.?K.?Ghosh  P.?BhattacharyyaEmail author 《Environmental Geology》2004,45(7):1010-1016

Arsenic (As) sorptivity and acetate (pH 4.8) and oxalate (pH 3.0) extractable iron levels were monitored for 180 d, during and after flooding of two As contaminated soils. The effects of three different organic matter supplements/amendments, for example farm yard manure (FYM), municipal solid waste compost (MSWC) and sewage-sludge (SS) on the above parameter were also examined. In nonflooded soils, As sorptivity was mainly influenced by clay content. On flooding, there were large increases in acetate, oxalate extractable iron and As sorptivity. Organic matter addition increased the same parameters. Among the organic matters, SS showed greater effect on As sorption followed by MSWC and FYM. During flooding, As sorption is mainly dependent upon poorly crystalline iron oxide. During oxidation of previously flooded soils, levels of As sorptivity, acetate and oxalate extractable iron decreased rapidly, but did not return to the levels occurring before reduction. SS and MSWC served as binding agents for native and irrigation water As, thereby moderating the rapid As mobilization to the crop rizosphere.  相似文献   

Velocity dependent inertial induction: A possible mechanism for cosmological red shift in a quasi static infinite universe     

Amitabha Ghosh 《Journal of Astrophysics and Astronomy》1997,18(4):449-454

The paper shows that a phenomenological model of inertial induction based on a proposed extension of Mach’s Principle can produce the observed cosmological red shift in a quasi-static infinite universe. Unlike all other theories (except the Doppler effect) to explain the observed red shift this model can be verified from other local effects predicted by this mechanism. A number of such phenomena have been investigated and these expected effects are not only found to be present but they also explain a number of unexplained or ill explained observational results. It is suggested that attempts should be made to verify the model through further tests and observations.  相似文献   

Geochemistry and Origin of Neoproterozoic Granitoids of Meghalaya, Northeast India: Implications for Linkage with Amalgamation of Gondwana Supercontinent   总被引：2，自引：1，他引：2  

Subhasish Ghosh  A.E. Fallick  D.K. Paul  P.J. Potts 《Gondwana Research》2005,8(3):421-432

Many granitic bodies intrude the basement gneisses in Meghalaya Plateau, Northeast India. Rb-Sr whole-rock isotopic ages of the granitoids range from 881 to 479 Ma while the ages of the basement orthogneisses vary from 1714 to 1150 Ma. All the plutons are dominantly metaluminous and show geochemical variation. Oxygen isotopic compositions in the granitoids and gneisses are concordant (d¹⁸O: + 5.78% to + 8.70%). However, the gneisses from high-grade terrain have low d¹⁸O value of +2.52% to +5.31%. Initial ⁸⁷Sr/⁸⁶Sr (I_Sr) ratios of the plutons vary from 0.70459 to 0.71487 and tend to increase with progressive younging in age. The geochemical characters suggest derivation of the granites from lower crustal source. The fractionated rare earth patterns observed in the granitoids can be obtained by partial melting of gneisses or diorites. Some gneiss samples have experienced interaction with hydrothermal fluids resulting in lowering d¹⁸O. The isotopic ages of granite plutonism in Meghalaya are similar to the plutonic and tectonothermal events in other parts of India, southwestern Australia and document final amalgamation events of the Gondwana Supercontinent.  相似文献   

Crop polarisation behavior derived from Multi-Temporal adeos-polder data     

V. N. Sridhar  R. P. Singh  Anjum Mahtab  Ranendu Ghosh 《Journal of the Indian Society of Remote Sensing》2005,33(2):339-344

This paper reports a study on multi-temporal polarized response of wheat crop from spaceborne ADEOS-POLDER sensor over a homogeneous wheat region of Punjab, India. Both the polarized as well as total reflectance of wheat were observed at different scattering angles for two spectral bands i.e. 670 nm and 865 nm during crop growth from November to April in rabi 1996-97 season. Results show that sun-target-viewing geometry plays an important role in polarization property. The top of atmosphere (TOA) polarized reflectance is found to decrease exponentially with increasing scattering angle. Polarized reflectance of crop was found to be an order of magnitude smaller in comparison to the total reflectance. An attempt was also made to model the observed polarized behavior over an agricultural area using a theoretical simplified crop reflectance model and accounting for atmospheric molecular (Rayleigh) contribution in the single scattering approximation. It was found that there was a decrease in the polarized reflectance at the grain filling (heading) stage of wheat crop. This is in accordance with ground- based observations and can be due to the reduction in the specular component of the reflected light during post-heading stage of the crop.  相似文献   

The effect of q-distributed ions during the head-on collision of dust acoustic solitary waves     

Uday Narayan Ghosh  Prasanta Chatterjee  Sanjib Kumar Kundu 《Astrophysics and Space Science》2012,339(2):255-260

The head-on collision of dust acoustic solitary waves are studied in a dusty plasma composed of dust and nonextensive distributed ions by using the extended version of Poincaré-Lighthill-Kuo (PLK) method. The effect of the nonextensivity on the phase shift is studied. It is found that the presence of nonextensive distributed ions plays a significant role on the collision of dust acoustic solitary waves.  相似文献   

An investigation on the relationship between solar irradiance signal from ERBS and 8B solar neutrino flux signals from SNO     

Mofazzal H. Khondekar  Dipendra N. Ghosh  Koushik Ghosh  Anup Kumar Bhattacharya 《Astrophysics and Space Science》2012,342(2):287-301

In the present work an attempt has been made to investigate statistical association between solar neutrino flux data (both D₂O and Salt data) collected from Sudbury Neutrino Observatory and solar irradiance data detected by Earth Radiation Budget Satellite. To serve the present purpose we have used the Multifractal Detrended Cross Correlation Analysis (MF-DCCA) based on Detrended Fluctuation Analysis (MF-X-DFA) method and the Detrending Moving Average Analysis (MF-X-DMA) which explores the long term power-law cross correlations between above two pairs of data sets. Investigation also has been made to find the frequency and time dependent local phase relationship in each pair of data sets using continuous wavelet transform (CWT) based Semblance Analysis. The Semblance Analysis reveals that there exists positive phase correlation as well as negative phase correlation between solar irradiance and D₂O data at different time sub-intervals. This type of mixed phase correlation is also experienced between solar irradiance and Salt data at different time sub-intervals. The causal relationship between the D₂O and the solar irradiance time series and that between Salt and solar irradiance time series have been revealed using Singular Spectral Analysis (SSA). Calculations indicate that possibly the present solar neutrino flux data (both D₂O and Salt data) is supportive to predict the solar irradiance data but may not the vice versa which in turn suggests that the variability of nuclear energy generation process inside the Sun may influence the solar activity.  相似文献   

A study of generalized second law of thermodynamics in modified f(R) Horava–Lifshitz gravity     

Surajit Chattopadhyay  Rahul Ghosh 《Astrophysics and Space Science》2012,341(2):669-674

This work investigates the validity of the generalized second law of thermodynamics in modified f(R) Horava–Lifshitz gravity proposed by Chaichian et al. (Class. Quantum Grav. 27: 185021, 2010), which is invariant under foliation-preserving diffeomorphisms. It has been observed that the equation of state parameter behaves like quintessence (w>−1). We study the thermodynamics of the apparent, event and particle horizons in this modified gravity. We observe that under this gravity, the time derivative of total entropy stays at positive level and hence the generalized second law is validated.  相似文献   

Development of a modified bare soil and urban index for Landsat 8 satellite data     

Atul Kant Piyoosh  Sanjay Kumar Ghosh 《国际地球制图》2018,33(4):423-442

Mapping of urban area has always been a challenging task due to its similar spectral characteristics with bare soil. The spectral characteristics of urban and bare soil being similar, causes confusion and misclassification among themselves. A new modified normalized difference soil index (MNDSI) has been proposed using PAN and Band 7 of Landsat 8. PAN band of Landsat 8 provides increased contrast between vegetation and land areas without vegetation. Subsequently, MNDSI was used to develop a new normalized ratio urban index (NRUI) by enhancing the capability of biophysical composition index (BCI) in two stages. First, a ratio urban index (RUI) was developed which discriminates urban and soil better than BCI. Second, RUI was further enhanced, subsequently known as NRUI, which is able to discriminate urban area from soil even better than RUI. MNDSI and NRUI show a good discrimination between soil and urban and may be useful for such purposes.  相似文献   

Effect of Biochar Produced from Mesquite on the Compaction Characteristics and Shear Strength of a Clayey Sand     

Hussain  Rojimul  Ghosh  Kishor Kumar  Garg  Ankit  Ravi  K. 《Geotechnical and Geological Engineering》2021,39(2):1117-1131

Biochar is a carbon-rich and low microbial degrading material obtained after pyrolysis of biomass in the absence or limited content of oxygen. The impact of biochar on hydraulic properties of soil is extensively studied in agricultural and geotechnical or geoenvironmental engineering for potential application in bioengineered structures. While a little study is conducted to assess its effect on soil mechanical properties, especially shear strength. However, the effect of biochar on the combined shear strength and compaction characteristics of soil is not studied. The shear strength of biochar amended soil is thought to be related to the compaction characteristics. In addition, the effect of biochar on the shear strength of the soil is soil and biochar specific. In this study, an attempt was made to investigate and better understand the effect of biochar on the shear strength and compaction characteristics of a clayey sand for potential application in bioengineered structures. Standard proctor, direct shear and unconfined compression tests were conducted on bare soil and soil amended with 5, 10 and 15% (w/w) biochar. The experimental results revealed that the amendment of biochar from 5 to 15% (w/w) decreased the dry density and increased the shear strength parameters such as cohesion (c) and angle of internal friction (ϕ) of the soil. While it decreased the undrained shear strength (c_u) at higher compaction density (> 0.95MDD) and increased at lower compaction density (< 0.9MDD). Thus, in undrained condition, the initial compaction density has a strong influence on the shear strength of biochar amended soil. In addition, the increased c and ϕ and decreased dry density in biochar amended soil is observed to increase the stability of slopes (hypothetical). The increase of c and ϕ is believed to be due to the roughness and active chemicals (functional groups) present on the surface of the biochar. The decreased c_u at higher density is believed to be due to the lubricating effect by the higher water content.

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Correction to: Application of analytical hierarchy process (AHP) for flood risk assessment: a case study in Malda district of West Bengal,India     

Abhishek Ghosh  Shyamal Kumar Kar 《Natural Hazards》2018,92(1):369-379

Flow pulsations in two-phase and single-phase near-critical fluids are considered as a possible source of ultra-low-frequency seismo-electromagnetic variations. The conditions for generation and suppression of density wave instability in the crust are analyzed and the surface electromagnetic effect due to streaming potential generation is estimated. The upper limit of amplitude of magnetic field variations due to density wave instability is about 0.1 nT for single-phase supercritical and 1 nT for two-phase flow oscillations in the frequency range \(10^{-4}{-}10^{-2}~\) Hz for the temperature gradients and spatial scales possible during strike slip events. The signal is characterized by a decaying amplitude with typical relaxation time of about several quasi-periods. The possibility of generation of very low-frequency flow pulsations in two-phase fluids via individual bubble evolution and interaction with external acoustic waves is discussed.  相似文献