Molecules in white dwarfs

Molecular dissociation equilibrium calculations were done for the model atmospheres of DA and non-DA white dwarfs. Our calculations show that He ₂ ⁺ and HeH⁺ appear as most abundant molecules in the atmospheres of non-DA white dwarfs while H₂ and H ₂ ⁺ are most abundant molecules in DA white dwarfs. It is suggested that these molecules should be searched for in the atmospheres of white dwarfs.     

Hydrological modelling of a small watershed using generated rainfall in the soil and water assessment tool model

An adequately tested soil and water assessment tool (SWAT) model was applied to the runoff and sediment yield of a small agricultural watershed in eastern India using generated rainfall. The capability of the model for generating rainfall was evaluated for a period of 18 years (1981–1998). The watershed and subwatershed boundaries, drainage networks, slope, soil series and texture maps were generated using a geographical information system (GIS). A supervised classification method was used for land‐use/cover classification from satellite imageries. Model simulated monthly rainfall for the period of 18 years was compared with observations. Simulated monthly rainfall, runoff and sediment yield values for the monsoon season of 8 years (1991–1998) were also compared with their observed values. In general monthly average rainfall predicted by the model was in close agreement with the observed monthly average values. Also, simulated monthly average values of surface runoff and sediment yield using generated rainfall compared well with observed values during the monsoon season of the years 1991–1998. Results of this study revealed that the SWAT model can generate monthly average rainfall satisfactorily and thereby can produce monthly average values of surface runoff and sediment yield close to the observed values. Therefore, it can be concluded that the SWAT model could be used for developing a multiple year management plan for the critical erosion prone areas of a small watershed. Copyright © 2004 John Wiley & Sons, Ltd.     

尼泊尔及南侧邻区元古宙以来的构造-沉积演化

迄今,尼泊尔及其南侧邻区元古宙以来的构造-沉积演化尚缺乏系统性研究.为了促进区域地质认识,结合前人研究成果及新的研究发现,对尼泊尔低喜马拉雅带及以南的构造-沉积演化首次进行系统性总结与讨论.结果表明:尼泊尔低喜马拉雅带及以南与印度地盾北缘在地质历史中的构造-沉积演化息息相关,且自元古宙以来,发育了被动大陆边缘→陆内裂谷→被动大陆边缘→前陆盆地等不同构造演化阶段的沉积响应;尼泊尔西部的Dailekh群属于~1.8 Ga以前或前哥伦比亚超大陆之前的被动大陆边缘沉积;Vindhyan超群为下断上坳的陆内裂谷沉积,尼泊尔境内的Lakharpata群相当于下Vindhyan群;Gondwana超大陆裂解导致由北往南形成一系列初始发育时间越来越晚的裂谷盆地;Surkhet群至Siwalik群为被动大陆边缘至前陆盆地沉积,其中,Surkhet群Swat/Subathu组是喜马拉雅南侧地质历史上最后一套海相沉积地层,也是被动大陆边缘向前陆盆地转换期的沉积响应;Siwalik群大规模的磨拉石建造标志着喜马拉雅快速和大幅度隆升,该群沉积成岩后,印度-欧亚板块进一步的挤压作用导致了地质历史上迄今为止最后一次强烈的构造运动,形成MFT与Siwalik褶皱带,并奠定了喜马拉雅带现今构造格局.      

Development of limiting soil slope profile under seismic condition using slip line theory

This study embraces the formation of the limiting geometry of finite slopes under the static and seismic conditions within the slip line theory framework coupled with the modified pseudo-dynamic approach. The proposed methodology is expected to achieve a global factor of safety of 1.0 for the obtained slope profile. While analysing the stability of slopes using the limit analysis or the limit equilibrium method, the cognition of the slope geometry and the nature of the slip surface need to be known in advance. Such limitations are ruled out in the present analysis with the aid of the slip line method. Further, by employing the modified pseudo-dynamic approach, the dynamic properties of soil, such as damping ratio and frequency effect, are effectively considered in this stability analysis. The consideration of the slip line theory permits to achieve an adaptive failure mechanism in the analysis. The impact of a set of parameters characterizing the input motion and the dynamic soil properties on the behaviour of a slope explains the relevance of the present modified pseudo-dynamic approach compared to the conventional pseudo-static and the original pseudo-dynamic approaches. The proposed solution serves as a measure of the seismic slope stability in accordance with the geomorphological process generally encountered in nature. Compared with the available literature, the present results propose safe, economical, and efficient design guidelines for finite slopes and intimate the need for preventive measures to enhance the stability of existing slopes.

     

A Case Study: Heavy Rainfall Event Comparison Between Daily Satellite Rainfall Estimation Products with IMD Gridded Rainfall Over Peninsular India During 2015 Winter Monsoon

India Meteorological department (IMD) used INSAT-3D Metrological Satellite Imager data to drive two type rainfall estimation products viz-Hydro Estimate (HE) and INSAT Multi-Spectral Rainfall Algorithm (IMSRA) on half hourly rainfall rate and daily accumulated rainfall in millimeter (mm). Integrated Multi-Satellite Retrieval for GPM (IMERG) product is being derived by NASA and JAXA by using Global Precipitation Mission (GPM) satellites data. IMSRA and GPM (IMERG) are gridded data at 10 km spatial resolution and HE is available at pixel level (4 km at Nadir). IMD provides gridded rainfall data at 0.25° × 0.25° resolution which is based on wide coverage of 6955 actual observation. In present study, validation of INSAT-3D based Hydro Estimator (HE), INSAT Multi-Spectral Rainfall Algorithm (IMSRA) and Integrated Multi-Satellite Retrieval for GPM (IMERG) of Global Precipitation Mission (GPM) satellites are carried out with IMD gridded data set for heavy rainfall event during winter monsoon, over peninsular India (November–December 2015). In validation, Nash–Sutcliffe efficiencies (NSE), RMSE, Correlation, Skilled scores are calculated at grid level for heavy and very heavy rain categories and the values of NSE of HE (? 32.36, ? 3.12), GPM (? 68.67, ? 2.39) and IMSRA (? 0.02, 0.28) on 16th November 2015 and HE (? 13.65, ? 1.69), GPM (? 43.79, ? 2.94) and IMSRA (? 1.08, ? 1.60) on 2nd Dec 2015, for heavy and very heavy rainfall. On both days, HE is showing better rainfall estimate compare to GPM for Heavy rainfall and GPM showing better estimation for very heavy rainfall events. In all the cases IMSRA is underestimating, if daily rain fall exceeded 75 mm.     

Audio-magnetotelluric investigation of sulfide mineralization in Proterozoic–Archean greenstone belts of Eastern Indian Craton

Greenstone belts are well known for gold occurrences at different regions of the world. The Dhanjori basin in the eastern Singhbhum region shows major characteristics of a rifted greenstone belt. Initially, we conducted 14 audio-magnetotelluric (AMT) measurements for a profile of \(\sim \)20 km in the frequency range of 1 kHz to 10 Hz over this rather complex geologic environment covering Dhanjori Volcanics (DhV) and Kolhan Group (KG). Subsequently, gravity and magnetic surveys were also conducted over this AMT profile. The purpose of the survey was to identify and map conductive features and to relate them to metallogeny of the area along with the mapping of the basement of Dhanjori basin. The strike analysis showed \(\hbox {N30}^{\circ }\hbox {W}\) strike for DhV for all the frequencies and for sites over KG domain in the frequency range of 100–10 Hz, but for KG domain, the obtained strike in 1 kHz to 100 Hz is \(\hbox {N45}^{\circ }\hbox {E}\). As the combination of transverse electric (TE), transverse magnetic (TM) and tipper (Tzy) can recover the electrical signature in complex geological environment, we discuss the conductivity model obtained from TE+TM+Tzy only. The inversion was carried for the regional profile with 14 sites and for 7 sites over KG domain. Conductivity model shows two well resolved conductors, one each in KG and Quartz Pebble Conglomerate Dhanjori (QPCD) domains respectively showing common linked concordant features between these regional and KG profiles. The conductors are interpreted as sulfide mineralization linked with QPCD group of rocks which may host gold. These conductors are also horizontally disposed due to the intrusive younger Mayurbhanj Granite. These intrusives correlate well with the gravity modeling as well. The thickness of the Dhanjori basin at the central is about 3.0 km, similar to that from gravity modeling. The conductivity model also indicates the presence of shallow conductors, but could not be resolved due to lack of high frequency data. However, the results from the close-by drill site indicate the presence of shallow sulfide mineralization hosting gold. The deep level conductors delineated from AMT studies are associated with gravity high and low magnetic. ICP-AES results of Dhanjori samples show significant concentration of gold \(\sim \)5.0 g/t, which is of economic consideration. Thus, it can be inferred that the conductors have evidences of sulfide mineralization which host gold.     

Lithologic boundaries from gravity and magnetic anomalies over Proterozoic Dalma volcanics

Dalma volcanics (DVs) has intruded the older Singhbhum Group of Metapelites. Despite DVs being rich in mineralisation, its boundaries are not clearly demarcated. Gravity and magnetic surveys have been attempted for mapping the boundaries in DVs. These surveys were made in the northern fringe of the DVs over an area of \(\sim \)0.70 \(\hbox {km}^{2}\) along 13 parallel lines at 50 m spacing. The data was acquired at \(\sim \)25 \(\hbox {m}\) spacing. The surveys were taken for determination of lithological boundaries, depths and nature of causative source using Euler depth solutions and radially averaged power spectrum (RAPS). Residual anomaly maps of gravity and magnetic intensity show the same trend as that of Bouguer gravity anomaly and total magnetic intensity anomaly map indicating towards shallow sources. The magnetic map in general follows the same pattern as that of gravity anomaly maps. The map shows coincident high gravity and magnetic anomalies. These anomalies together with resistivity signatures confirm that the northern fringe of DVs hosts volcanogenic massive sulphide settings. The Euler depth solution delineated the lateral boundaries and nature of the source. It seems that the source is of spherical nature lying within a depth range of 25–40 m. The obtained lithological (vertical) units from RAPS are between Lower DVs, Upper DVs and Singhbhum Group Metapelites at depths of \(\sim \)15, \(~\sim \)25 and \(\sim \)40 \(\hbox {m}\), respectively. The metallogeny is associated with the Upper DVs and the corresponding delineated lithological (vertical) unit is indicative of the top of the ore body. Good agreement is observed with the geological succession from the drilling data and resistivity data. The findings suggest that the northern fringe of DVs could be a preferred target for drilling.     

Estimating net primary productivity in tropical forest plantations in India using satellite-driven ecosystem model

Net Primary Productivity (NPP) is a significant biophysical vegetation variable to understand the spatio-temporal distribution of carbon and source-sink nature of the ecosystem. This study was carried out in a forest plantation area and aimed to (i) estimate the spatio-temporal patterns of NPP during 2009 and 2010 using Carnegie-Ames-Stanford Approach [CASA] model and (ii) study the effects of climate variables on the NPP using generalized linear modelling (GLM) approach. The total annual NPP varied from 157.21 to 1030.89 gC m^?2 yr^?1 for the year 2009 and from 154.36 to 1124.85 g C m^?2 yr^?1 for the year 2010. The annual NPP was assessed across four major plantation types, where maximum NPP gain (106 and 139 g C m^?2 yr^?1 ) in October was noticed in teak (Tectona grandis) and minimum (77 and 109 g C m^?2 yr^?1 ) in eucalyptus (Eucalyptus hybrid) during 2009 and 2010.The validation, using field-estimated NPP, showed under-estimation of modelled NPP, with maximum MAPE of 34% for eucalyptus and minimum of 13% for teak. The dominant influence of precipitation on the NPP was revealed by GLM explaining more than 20% of variation. CASA model efficiently estimated the annual NPP of plantations. The accuracy could be improved further with inclusion of higher resolution data.     

Geochemical and mineralogical studies of chlorine-rich amphibole and biotite from the 2.5 Ga mid-crustal basement beneath the 1993 Killari earthquake region,Maharashtra: Evidence for mantle metasomatism beneath the Deccan Trap

Fluid driven metasomatism and mass transfer from the earth’s mantle have played an important role in the evolution of the lower continental crust in many geodynamically active areas. The epicentral region of the disastrous 1993 Killari earthquake (M 6.2), concealed below a thick suite of Deccan volcanics in central India, appear to be one such region. In connection with the study of seismotectonics of the earthquake prone Deccan volcanic region, we have carried out systematic and detailed geochemical and mineralogical investigation on core samples from the basement, obtained from the 617m deep KLR-1 borehole, drilled in the epicentral region of Killari. Our investigations indicate that the basement, concealed below 338m thick Deccan volcanics, is made up of CO₂, Cl, FeO and CaO-rich, high density (2.82 g/cm³) — high velocity (avg. Vp: 6.2 km/s) moderately retrogressed upper amphibolite to granulite facies mid crustal rocks, which were subjected to pervasive Ca-metasomatism due to infiltration of mantle fluids. Graniticgneissic layer, typical of the upper crust, seems to be totally absent from this earthquake region. Chondrite normalized trace and rare earth elemental patterns display negative Eu anomalies together with LILE enrichment. Similarly, spider diagrams for incompatible elements show depletion in Zr, Hf, Y, Ta and Nb relative to the primitive mantle, indicating possible alterations of such relatively immobile elements at relatively high temperatures. Selective enrichment is also observed in transitional elements like Cu and Zn, indicating the possible role of chlorine in metal transport. The present study suggests that regional metasomatism beneath the Deccan Traps, which apparently alters the basic fabric of the rock during recrystallisation and makes it weak, may have a link with the nucleation of large earthquakes.     

Leaching behavior of lignite fly ash with shake and column tests

The maximum concentration of the majority of the trace metals in the leachates from shake and column test of lignite fly ash (LFA) was within the prescribed limits; however, total dissolved solids, total hardness, cations and anions (except K⁺), being above the prescribed limits, may lead to the increase in the hardness and salinity in the soil on the disposal of LFA. Present generation of huge amount of fly ash from thermal power plants (TPPs) is a big challenge concerning contamination of soil, crop produce and surface and ground water bodies due to the presence of some of the toxic trace metals in it. The leaching behavior of alkaline LFA (pH, 10.94), from TPP of Neyveli Lignite Corporation (NLC), India, was investigated by shake and column tests using water and sodium acetate buffer. The leaching of trace metals from LFA was governed by their concentrations, association with the ash particles, leaching duration and pH of the leachate (most influencing parameter). The leaching of metals followed the order: buffer column > aqueous column > aqueous shake > buffer shake test.