A viable mechanism for the production of energy in active galactic nuclei     

R. K. Thakur 《Astrophysics and Space Science》1993,199(1):159-164

It is suggested that a collapsing supermassive object, which acts as an ultra-high energy particle accelerator, is the precursor of an active galactic nucleus and that the gravitational energy released during the collapse of the object is locked in the quark-gluon plasma permeated by leptons into which the entire matter in the core of the object is converted as a result of the collapse. It is also pointed out that the collapse of the object to a space-time singularity is inhibited by Pauli's exclusion principle as well as by Heisenberg's uncertainty principle and that the object explodes, before it could collapse to a singularity, thereby releasing the enormous amount of energy locked in the quark-gluon plasma.  相似文献   

Probable gas hydrate/free gas model over western continental margin of India     

Satyavani  N.  Shankar  Uma  Thakur  N.K.  Reddi  S.I. 《Marine Geophysical Researches》2002,23(5-6):423-430

Multi-channel seismic reflection data from the western continental margin of India (WCMI) have been analyzed to construct a plausible model for gas hydrate formation. A reflector at 2950 ms two way travel time (TWT) on one of the sections is interpreted to represent the base of the layer of the methane hydrate, identified by a bottom simulating reflector (BSR) that lies almost 500 ms beneath the sea floor. BSRs of similar origin are common world wide, where they are usually interpreted to mark the base of gas hydrate bearing clastic sediment, with or without underlying free gas. In this study we present a model with the contrasting physical properties that produce synthetic wavelets that match with the observed BSR amplitude and waveforms for varying source-receiver offsets of multi-channel seismic reflection data. The preliminary results presented here put important constraints on models that predict the distribution and formation of hydrate. Offset-dependent amplitude recovery also gives an appropriate response for hydrate characterization.  相似文献   

Simulation of strong ground motion for 1905 Kangra earthquake and a possible megathrust earthquake (Mw 8.5) in western Himalaya (India) using Empirical Green’s Function technique     

Babita Sharma  Sumer Chopra  Vikas Kumar 《Natural Hazards》2016,80(1):487-503

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Consistent seasonal snow cover depth and duration variability over the Western Himalayas (WH)   总被引：1，自引：0，他引：1  

Dan Singh  Vikas Juyal  Vikas Sharma 《Journal of Earth System Science》2016,125(7):1451-1461

Precipitation in solid form, i.e., snow, during winter season over the Western Himalayas (WH) leads to the build-up of seasonal snow cover. Seasonal snow cover build-up (snow cover depth and duration) largely depends on atmospheric variables such as temperature, precipitation, radiation, wind, etc. Integrated (combined) influence of atmospheric variables on seasonal snow cover gets reflected in terms of spatial and temporal variability in seasonal snow cover build-up pattern. Hence spatial and temporal variability of seasonal snow cover build-up can serve as a good indicator of climate change in high altitude mountainous regions like the WH. Consistent seasonal snow cover depth and duration, delay days and early melt days of consistent seasonal snow cover at 11 stations spread across different mountain ranges over the WH were analyzed. Mean, maximum and percentiles (25th, 50th, 75th, 90th and 95th) of consistent seasonal snow cover depth and duration show decline over the WH in the recent past 2–3 decades. Consistent seasonal snow cover is found to melt early and snow cover build-up pattern is found to show changes over the WH. Decline in consistent seasonal snow cover depth, duration and changing snow cover build-up pattern over the WH in recent decades indicate that WH has undergone considerable climate change and winter weather patterns are changing in the WH.  相似文献   

A study of characteristics of ground motion response spectra from earthquakes recorded in NE Himalayan region: an active plate boundary     

Babita Sharma  Sumer Chopra  P. Chingtham  Vikas Kumar 《Natural Hazards》2016,84(3):2195-2210

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One-dimensional hydrodynamic modeling of GLOF and impact on hydropower projects in Dhauliganga River using remote sensing and GIS applications     

Praveen K. Thakur  Suruchi Aggarwal  S. P. Aggarwal  S. K. Jain 《Natural Hazards》2016,80(2):1057-1081

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Biosafety assessment of municipal wastewater after treatment by <Emphasis Type="Italic">Serratia</Emphasis> sp. ISTVKR1     

A. Gupta  I. S. Thakur 《International Journal of Environmental Science and Technology》2018,15(10):2095-2106

The previously described potent biodegrading bacterial strain Serratia sp. ISTVKR1 isolated from sludge of Vasant Kunj Sewage Treatment Plant (VK STP) was used for the study of detoxification of municipal wastewater contaminants with the help of in vitro bioassays conducted on human liver cancer cell line HepG2. The strain has previously been shown to reduce wastewater contaminant load as revealed by a sevenfold reduction in COD and removal of some organic contaminants in the GC–MS analysis of wastewater post-72-h bacterial treatment. Cytotoxicity, genotoxicity and dioxin-like behavior of real municipal wastewater (collected from inlet of VK STP) was assessed before and after bacterial treatment using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), alkaline comet and 7-ethoxyresorufin-O-deethylase (EROD) assays, respectively. The bacterial strain was inoculated into MSM broth (pH = 7.2) containing 50% v/v filter-sterilized influent of VK STP and incubated up to 240 h at 30 °C and 130 rpm. Physicochemical and toxicological analyses were performed for the culture samples. The results of bioassays revealed an increase in cell viability by 40.16% and a reduction in the % EROD activity by 58.4% in the 240-h bacteria-treated sample as compared to the 0-h sample. Genotoxicity as indicated by tail moment (TM) and olive tail moment (OTM) was found to reduce by five- and threefold, respectively, after 240-h bacterial treatment. The results of the study confirmed the potency of the bacterial strain in detoxification of wastewater contaminants.  相似文献   

Electro-chemical mineralization of recalcitrant indole by platinum-coated titanium electrode: multi-response optimization,mechanistic and sludge disposal study     

A. D. Hiwarkar  S. Singh  V. C. Srivastava  C. Thakur  I. D. Mall  S.-L. Lo 《International Journal of Environmental Science and Technology》2018,15(2):349-360

Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pH_o), current density (j), conductivity (k) and treatment time (t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal (Y ₁) and specific energy consumption (Y ₂) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m², k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole.  相似文献   

Electrical analogy for modelling thermal regime and moisture distribution in sandy soils     

Somenath Mondal  Vikas Sharma  P. Apte 《Geomechanics and Geoengineering》2018,13(1):22-32

The soil mass is subjected to temperature variation due to several human activities (viz. tanks storing heated fluids, buried cables and pipelines, air-conditioning ducts, disposal of nuclear and thermal power plant wastes etc.), which result in heat-induced migration of the moisture in it. Though several studies have been conducted in the past to investigate the mechanism of heat migration through the soil mass, a methodology for ‘real-time measurement of the variations in temperature, flux and moving moisture front, in tandem, with respect to space' has rarely been attempted. In this context, extensive laboratory investigations were conducted to measure real-time flux and temperature variations in the sandy soils, and the validation of results has been done by employing an equivalent electrical circuit programme, LTspice. Subsequently, a mathematical model PHITMDS (i.e. Prediction of Heat-Induced Temperature and Moisture Distribution in Soil) has been developed and its utility and efficacy, for predicting the depth-wise temperature and heat-induced moisture migration, due to evaporation, in terms of position of moving moisture front in the sandy soil has been critically discussed and demonstrated.  相似文献   

Geochemical Characterization and Controlling Factors of Chemical Composition of Spring Water in a Part of Eastern Himalaya     

Chandrashekhar Azad Vishwakarma  Ratan Sen  Neha Singh  Priyadarshini Singh  Vikas Rena  Kumari Rina  Saumitra Mukherjee 《Journal of the Geological Society of India》2018,92(6):753-763

This paper focuses on the suitability of spring water for drinking and irrigation purposes in a part of eastern Himalaya, south Sikkim. There are many anthropogenic and geogenic factors contributing as a source of major cations and anions in the spring water. The spring water chemistry show a variation in EC, pH, TDS, Temperature, Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe²⁺, Pb, Mn, Cu, HCO₃^-, Cl^-, PO₄^3-, NO₃^-, F^- and SO₄^2-. Mainly two types of water quality indexing has been used, one for suitability of spring water for drinking purposes and the other for irrigation purposes. For drinking purposes, Piper diagram used for determination of water type, water quality index (WQI) for quality monitoring and saturation index for mineral dissolution in water. % Na, RSC (Residual Sodium Carbon) and SAR (sodium absorption ratio) have been used for irrigation suitability. Piper diagram shows that CaHCO₃ type of water was dominant in the study area. The WQI depicted excellent category and SAR, percent sodium and RSC (Residual Sodium Carbon) depict excellent, good and permissible category for irrigation purposes. Principle component analysis (PCA) was used to determine the major influencing factor responsible for the variability in the parameters analysed of spring water.  相似文献