Genesis of cordierite-gedrite-cummingtonite rocks of the northern portion of the khetri Copper Belt,Rajasthan, India     

Ravindra K. Lal  Ravi S. Shukla 《Lithos》1975,8(3):175-186

The cordierite-gedrite-cummingtonite rocks occur in the zone of sulphide mineralization. Field and petrographic evidences suggest formation of these rocks from the $\text{chlorite}\text{±}\text{garnet}$ schists which are associated with them. Time relations between crystallization and deformation, as evident by textural relations, suggest that this transformation constitutes a progressive sequence in time during prograde metamorphism in the area. Bulk chemical compositions of the cordierite-gedrite-cummingtonite rocks plot in the compositional range of the chlorite schists in the AKF, ACF and AFM diagrams. The AFM diagram shows a discontinuity in the topology as revealed by the intersection of the coexisting garnet-chlorite join with the three-phase field of cordierite-gedrite-garnet, suggesting the reaction: $\text{Al-chlorite}\text{+}\text{quartz}\text{(±}\text{garnet}\text{) ?}\text{gedrite}\text{+}\text{cordierite}\text{+}\text{H}{}_2\text{O}$. The reaction took place under conditions of , brought about by dilution of pore fluid by B, Cl, F, S, etc., which reduce the activity of water.  相似文献   

Exact Kantowski–Sachs cosmological models in general theory of relativity     

Rishi Kumar Tiwari  Uttam Kumar Dwivedi 《Astrophysics and Space Science》2008,318(3-4):249-253

We have studied cosmological model generated by perfect fluid coupled with mass less scalar field for Kantowski–Sachs space–time in general theory of relativity. Two different physically viable models of the universe are obtained by using a special law of variation for Hubble’s parameter that yields a constant value of deceleration parameter. Some physical consequences of the models have been discussed in case of Zel’dovich fluid.  相似文献   

Chemical Composition of Dew Resulting from Radiative Cooling at a Semi-arid Site in Agra, India     

Anita Lakhani  Ravindra Singh Parmar  Satya Prakash 《Pure and Applied Geophysics》2012,169(5-6):859-871

Dew samples were collected between October 2007 and February 2008 from a suburban site in Agra. pH, conductivity, major inorganic ions (F^?, Cl^?, NO ₃ ^? , SO ₄ ^2? , Na⁺, K⁺, Ca²⁺, Mg²⁺, and NH ₄ ⁺ ), and some trace metals (Cr, Sn, Zn, Pb, Cd, Ni, Mn, Fe, Si, Al, V, and Cu) were determined to study the chemistry of dew water. The mean pH was 7.3, and the samples exhibited high ionic concentrations. Dew chemistry suggested both natural and anthropogenic influences, with acidity being neutralized by atmospheric ammonia and soil constituents. Ion deposition flux varied from 0.25 to 3.0?neq?m^?2?s^?1, with maximum values for Ca²⁺ followed by NH ₄ ⁺ , Mg²⁺, SO ₄ ^2? , Cl^?, NO ₃ ^? , Na⁺, K⁺, and F^?. Concentrations of trace metals varied from 0.13 to 48?μg?l^?1 with maximum concentrations of Si and minimum concentration of Cd. Correlation analysis suggested their contributions from both crustal and anthropogenic sources.  相似文献   

Geochemical characteristics and controlling factors of chemical composition of groundwater in a part of Guntur district,Andhra Pradesh,India     

N. Subba Rao  Deepali Marghade  A. Dinakar  I. Chandana  B. Sunitha  B. Ravindra  T. Balaji 《Environmental Earth Sciences》2017,76(21):747

A survey on quality of groundwater was carried out for assessing the geochemical characteristics and controlling factors of chemical composition of groundwater in a part of Guntur district, Andhra Pradesh, India, where the area is underlain by Peninsular Gneissic Complex. The results of the groundwater chemistry show a variation in pH, EC, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃ ^?, Cl^?, SO₄ ^2?, NO₃ ^? and F^?. The chemical composition of groundwater is mainly characterized by Na⁺?HCO₃ ^? facies. Hydrogeochemical type transits from Na⁺–Cl^?–HCO₃ ^? to Na⁺–HCO₃ ^?–Cl^? along the flow path. Graphical and binary diagrams, correlation coefficients and saturation indices clearly explain that the chemical composition of groundwater is mainly controlled by geogenic processes (rock weathering, mineral dissolution, ion exchange and evaporation) and anthropogenic sources (irrigation return flow, wastewater, agrochemicals and constructional activities). The principal component (PC) analysis transforms the chemical variables into four PCs, which account for 87% of the total variance of the groundwater chemistry. The PC I has high positive loadings of pH, HCO₃ ^?, NO₃ ^?, K⁺, Mg²⁺ and F^?, attributing to mineral weathering and dissolution, and agrochemicals (nitrogen, phosphate and potash fertilizers). The PC II loadings are highly positive for Na⁺, TDS, Cl^? and F^?, representing the rock weathering, mineral dissolution, ion exchange, evaporation, irrigation return flow and phosphate fertilizers. The PC III shows high loading of Ca²⁺, which is caused by mineral weathering and dissolution, and constructional activities. The PC IV has high positive loading of Mg²⁺ and SO₄ ^2?, measuring the mineral weathering and dissolution, and soil amendments. The spatial distribution of PC scores explains that the geogenic processes are the primary contributors and man-made activities are the secondary factors responsible for modifications of groundwater chemistry. Further, geochemical modeling of groundwater also clearly confirms the water–rock interactions with respect to the phases of calcite, dolomite, fluorite, halite, gypsum, K-feldspar, albite and CO₂, which are the prime factors controlling the chemistry of groundwater, while the rate of reaction and intensity are influenced by climate and anthropogenic activities. The study helps as baseline information to assess the sources of factors controlling the chemical composition of groundwater and also in enhancing the groundwater quality management.  相似文献   

Near InfraRed Imaging Spectrograph (NIRIS) for ground-based mesospheric OH(6-2) and $$\hbox {O}_{2}$$(0-1) intensity and temperature measurements     

Ravindra P Singh  Duggirala Pallamraju 《Journal of Earth System Science》2017,126(6):88

This paper describes the development of a new Near InfraRed Imaging Spectrograph (NIRIS) which is capable of simultaneous measurements of OH(6-2) Meinel and \(\hbox {O}_{2}\)(0-1) atmospheric band nightglow emission intensities. In this spectrographic technique, rotational line ratios are obtained to derive temperatures corresponding to the emission altitudes of 87 and 94 km. NIRIS has been commissioned for continuous operation from optical aeronomy observatory, Gurushikhar, Mount Abu (\(24.6^{\circ }\hbox {N}\), \(72.8^{\circ }\hbox {E}\)) since January 2013. NIRIS uses a diffraction grating of 1200 lines \(\hbox {mm}^{-1}\) and 1024\(\times \)1024 pixels thermoelectrically cooled CCD camera and has a large field-of-view (FOV) of \(80^{\circ }\) along the slit orientation. The data analysis methodology adopted for the derivation of mesospheric temperatures is also described in detail. The observed NIRIS temperatures show good correspondence with satellite (SABER) derived temperatures and exhibit both tidal and gravity waves (GW) like features. From the time taken for phase propagation in the emission intensities between these two altitudes, vertical phase speed of gravity waves, \(c_{z}\), is calculated and along with the coherent GW time period ‘\(\tau \)’, the vertical wavelength, \(\lambda _{z}\), is obtained. Using large FOV observations from NIRIS, the meridional wavelengths, \(\lambda _{y}\), are also calculated. We have used one year of data to study the possible cause(s) for the occurrences of mesospheric temperature inversions (MTIs). From the statistics obtained for 234 nights, it appears that in situ chemical heating is mainly responsible for the observed MTIs than the vertical propagation of the waves. Thus, this paper describes a novel near infrared imaging spectrograph, its working principle, data analysis method for deriving OH and \(\hbox {O}_{2}\) emission intensities and the corresponding rotational temperatures at these altitudes, derivation of gravity wave parameters (\(\tau \), \(c_{z}\), \(\lambda _{z}\), and \(\lambda _{y})\), and results on the statistical study of MTIs that exist in the earth’s mesospheric altitudes.  相似文献   

Metallic Pb nanospheres in ultra-high temperature metamorphosed zircon from southern India     

Whitehouse  M. J.  Kusiak  M. A.  Wirth  R.  Ravindra Kumar  G. R. 《Mineralogy and Petrology》2017,111(4):467-474

Mineralogy and Petrology - A transmission electron microscope (TEM) study of Paleoproterozoic zircon that has experienced ultra-high temperature (UHT) metamorphism at ca. 570 Ma in the...  相似文献   

Simplified SMA-inspired 1-parameter SCS-CN model for runoff estimation     

Sangeeta Verma  Pushpendra Kumar Singh  Surendra Kumar Mishra  Sanjay Kumar Jain  Ronny Berndtsson  Anju Singh  Ravindra Kumar Verma 《Arabian Journal of Geosciences》2018,11(15):420

This study proposes a simplified 1-parameter SCS-CN model (M5) based on Mishra-Singh (2002) model and soil moisture accounting (SMA) procedure for surface runoff estimation and compares its performance with the existing SCS-CN method (SCS, 1956) (M1), Michel 1-P model (Water Resour Res 41:1-6, 2005) (M2), Sahu 1-P model (Hydrol Process 21:2872-2881, 2007) (M3), and Ajmal et al. model (J Hydrol 530:623-633, 2015) (M4) using large rainfall–runoff dataset of 48,763 events from123 USDA-ARS watersheds. The performance of models was evaluated using three statistical error indices such as Nash-Sutcliffe efficiency (NSE), root mean square error (RMSE), percentage bias (PBIAS), and rank and grading system (RGS). Based on the results obtained, the models can be ranked as follows: M5?>?M4?>?M3?>?M1?>?M2, i.e., model M5 outperformed all the remaining four models M1–M4 and hence is recommended for field applications.  相似文献   

Monsoon-Driven Geomorphological Changes Along the West Coast of Sri Lanka: A Combined Approach Utilizing ‘CoastSat’ and Google Earth Engine     

Gunasinghe  Gunasinghage Prasadh  Ratnayake  Nalin Prasanna  Ratnayake  Amila Sandaruwan  Samaradivakara  G. V. I.  Dushyantha  Nimila Praneeth  Jayaratne  Ravindra  Dinusha  Kodithuwakka Arachchige  Silva  Akalanka 《Ocean Science Journal》2022,57(3):475-492

Ocean Science Journal - Long-term field monitoring of shoreline changes is time-consuming, expensive, and labor-intensive. Instead, satellite images can be used as an alternative method to collect...  相似文献   

An assessment of Yarsagumba (Ophiocordyceps sinensis) collection in Dhorpatan Hunting Reserve,Nepal     

BarnaBahadur THAPA  Saroj PANTHI  Rajesh KumarRAI  UttamBabu SHRESTHA  Achyut ARYAL  Sabina SHRESTHA  Bhushan SHRESTHA 《山地科学学报》2014,11(2):555-562

Yarsagumba （Ophiocordyceps sinensis）, an endemic species to the Himalayas and Tibetan Plateau, is one of the most valuable medicinal mushrooms in the world. In Nepal, it is distributed largely in isolated patches of alpine grasslands of 3,000-5,000 m elevation. Although it is reported from 27 northernmost districts of Nepal, the local distribution pattern of this species is largely unknown. Furthermore, the collection system and local management regime of this species are not well documented. We conducted a field survey at Dhorpatan Hunting Reserve （DHR） among the different stakeholders in January-June 2012 to assess collection sites, patterns and trends and to understand the management regime. We estimated that about 75 kg of Yarsagumba is collected every year from DHR and the amount has been declining since 2008. To manage the resource, locals have initiated regulating the collection by issuing permits, taxing to the collectors, and monitoring the activities of harvesters with the help of park authorities. The revenue generated at local level from the permits has been used for community developmental activities.  相似文献   

Chasing Chinese Caterpillar Fungus (Ophiocordyceps sinensis) Harvesters in the Himalayas: Harvesting Practice and Its Conservation Implications in Western Nepal     

Uttam Babu Shrestha  Sujata Shrestha  Shivaraj Ghimire  Kamal Nepali  Bharat Babu Shrestha 《社会与自然资源》2014,27(12):1242-1256

The Chinese caterpillar fungus is famous for its high market value, unusual life history, and significant medicinal uses. It is harvested by very poor communities and sold for an extraordinarily high price. Most of the studies on this species are focused on therapeutic uses, chemical analyses, ecology, and trade. However, harvesting techniques and intensity of the harvests remain undocumented. We document harvesting techniques, trends of harvest, and perceptions of the Chinese caterpillar fungus harvesters in Dolpa, Nepal, based on surveys, focus-group discussions, and direct observations. Along with increasing market value, intensity of the harvest has been increasing. The Chinese caterpillar fungus harvest has now become the second most important livelihood strategy for the local communities, after agriculture. Reported per-capita harvest based on the first day of collection has declined over the last 4 years, apparently because of the decline in the stock and the increasing number of harvesters.  相似文献