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Search Results: 1 - 10 of 1858 matches for " Samarendra Bhattacharya "
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Review: the charnockite problem, a twenty first century perspective  [PDF]
Samarendra Bhattacharya
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.24049
Abstract: Beginning of the twentieth century was marked by coinage of a new rock name, Charnockite, first described as a hypersthene-bearing granite from Southern India. Since then charnockites have been described from most of the conti-nents and mostly restricted to high-grade belts. Later half of the last century saw a lively debate over an igneous versus metamorphic origin. However, two factors acted as deterrents for the resolution of the debate. First, charnockites and associated rocks occur in a variety of different structural setting and display diverse field rela-tions, attesting to possible different mode of origin. Second and possibly more important is the lack of consensus on the nomenclature of charnockites and associated rocks and this is commonly linked with the metamorphic versus magmatic perspective. Scanning the literature of this period makes one believe that both metamorphic and magmatic hypotheses are valid, but applicable to different field setting only. Before critically evaluating individual cases, it is imperative that a uniform approach in nomenclature should be agreed upon. It is proposed that name charnockite be adopted for any quartzofeldspathic rock with orthopyroxene, irrespective of its mode of occurrence, struc-tural setting and mode of origin. The associated more mafic varieties, be better described as mafic granulite, rather than basic charnockite. For the patchy charnockites of east Gondwana (including parts of Peninsular India, Sri Lanka and Antarctica), metamorphic transformation from amphibolite facies gneiss, by two different mechanisms: CO2 ingress from deep level, and drop in fluid pressure, has been proposed. However, all such patchy occurrence is not amenable to explanation by metamorphic trans- formation. In some instances, migmatisation of older charnockitic rocks is evident. Also pro- gressive charnockitisation relating patchy char-nockite to banded variety could be argued against on two counts: grain-size relation and time-relation. Larger bodies or bands have been explained as magmatic, but in many instances, from geochemical consideration alone. The compositional variation, commonly encoun-tered in many high-grade belts, if not described in terms of field relation, may lead to wrong no-tions of magmatic differentiation of mantle-de- rived melts. Crustal melting of dry granulite fa-cies source rocks has been proposed from geochemical and isotopic data of charnockitic intrusions. This model proposes high-tempera-ture melting of previously dehydrated and dry granulite source rocks. However, tectonic per-turbation
New experimental constraints: implications for pe-trogenesis of charnockite of dioritic composition  [PDF]
Rajib Kar, Samarendra Bhattacharya
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.210135
Abstract: Hornblende-dehydration melting experiments at high temperatures (> 950oC) indicate change of melt composition from tonalite/granodiorite to quartz-diorite; clinopyroxene instead of hornbl- ende as the residual phase and change in melting reaction from peritectic hornblende-dehydr- ation to eutectic clinopyroxene-orthopyroxene- plagioclase. In the light of these experimental results, petrogenesis of a charnockite pluton of homogeneous dioritic composition in the Eastern Ghats Belt, India, can be explained as melting at high-temperatures (> 950oC). Negative Sr and Eu anomalies further indicate plagioclase as a major residual phase, consistent with melt- ing at high-temperatures (> 950oC).
Secular evolution of continental crust: recorded from massif-type charnockites of Eastern Ghats belt, India  [PDF]
Samarendra Bhattacharya, Ashwini Kumar Chaudhary
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.210134
Abstract: It is reasonably well established that the Earth has substantially cooled from the Archean to the pre-sent and hence the sites, rates and pro- cesses of crust formation must have changed through geo-logic time. Archean and Proterozoic granitic rocks are the principal record of such changes. Massif-type charnockites in the Eastern Ghats granulite belt, India, of Archean and Proterozoic ages mirror the changing conditions and/or processes of continental crust for- mation. Though both can be explained by dehydration melting of mafic rocks, the conditions differ. Potasium and rubidium rich Proterozoic charnockites have significant negative Eu ano- maly indicating melting at shallow depths in the stability field of plagioclase. In contrast, sodium and strontium rich Archean charnockites with less LREE enrichment and less depletion in Eu indicate melting at greater depths in the stability field of garnet or amphibole.
Kabbaldurga charnockites revisited: Incipient growth or anatectic melt?  [PDF]
Samarendra Bhattacharya, Aswini K. Chaudhary
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.53055
Abstract:

A popular hypothesis of in situ transformation of amphibolite facies gneisses to patchy charnockites by CO2 influx from mantle was proposed primarily from the Kabbaldurga quarries in South Karnataka and subsequently reported from several south Indian localities. However, presence of abundant mafic granulite enclaves in Kabbaldurga and its neighborhood and its implications in relation to patchy charnockite genesis were not discussed. In these quarries patchy charnockites occur in various modes and associations. Some of these patches do occupy structural weak zones, such as shear bands and fold noses in the migmatitic gneisses, but many of the patchy charnockite bodies occur as branching veins transecting the gneissic foliation and hence do not account for fluid pathways. Most importantly, charnockitic leucosomes at margins of mafic granulite enclaves and charnockitic veins within some mafic granulite enclaves indicate a close genetic link between them via dehydration partial melting. This is further corroborated by trace element distribution between them. Dehydration partial melting in mafic rocks in a migmatite terrain such as Kabbaldurga, can explain all the different modes of the patchy charnockites as various stages of segregation and mobility relative to deformation. Abundant mafic granulite enclaves and field features suggesting a relatively late origin of the patchy charnockites, are compelling evidence against the notion of a transition zone. Mantle derivation age of the mafic source rocks (protoliths of mafic granulites) at Kabbaldurga at 3.08 ± 0.08 Ga with small positive ? values is virtually identical to the source of the massive charnockite of Karnataka craton at 3.08 Ga. This could imply a widespread mafic magmatism in South India around 3.0 Ga.

Relative Chronology in High-Grade Crystalline Terrain of the Eastern Ghats, India: New Insights  [PDF]
Samarendra Bhattacharya, Rajib Kar, Amit Kumar Saw, Prasanta Das
International Journal of Geosciences (IJG) , 2011, DOI: 10.4236/ijg.2011.24043
Abstract: The two major lithology or gneiss components in the polycyclic granulite terrain of the Eastern Ghats, India, are the supracrustal rocks, commonly described as khondalites, and the charnockite-gneiss. Northern Eastern Ghats belt, north of the Godavari rift has been defined as the Eastern Ghats Province, while that to the south has been defined as the Ongole domain; and although, these distinct crustal domains also record different ages of granulite metamorphism, both of these domains are dominated by the two lithologies. Many of the workers considered the khondalites as the oldest component with unknown basement and the charnockite- protoliths as intrusive into the khondalites. However, published geochronological data do not corroborate the aforesaid relations. Onset of khondalite sedimentation in the Proterozoic Eastern Ghats Province, constrained by detrital zircon data, as around 1.3 Ga and the charnockite-protolith emplacement between 1.9 and 2.9 Ga, argue against intrusion of felsic magma (tonalite, now enderbite!) in to the khondalites. The field relations of the hornblende-mafic granulite with the two gneiss components together with Sm-Nd isotopic data of the hornblende-mafic granulites (both the xenoliths within charnockites and those interbanded with the khondalites) indicate that khondalite sediments were deposited on older mafic crustal rocks. Mafic basement and supracrustal rocks were subsequently deformed and metamorphosed together during collisional orogeny at high to ultra-high temperatures – partial melting of mafic rocks producing the charnockitic melt; and partial melting of pelitic sediments producing the peraluminous granitoids. This is compatible with all the geochronological data as well as the petrogenetic model of partial melting for the charnockitic rocks in the Eastern Ghats Belt. The Ongole domain, south of the Godavari rift, though, is distinct in terms of the age of first/ earliest UHT metamorphism, but here too the charnockite-protoliths are older mafic rocks evidently not intrusive in to the khondalites.
Role of potassium and nitrogen on sugar concentration of sugar beet
Samarendra Barik
African Crop Science Journal , 2003,
Abstract: Sugar is obtained from root of sugar beet (Beta vulgaris L.) in addition to other sources. Three important economic parameters are often considered and these are root yield, sugar concentration in root juice and total sugar yield. All the three are affected by cropping period and use of fertilisers. Existing literature suggests the use of nitrogen and potash as fertilisers. An experiment over a period of three years with different combinations of N and K fertilisers for different cropping periods was carried out with multiple replicates. The highest root yield was obtained at a combination of N= 150 kg ha –1, K = 155 kg ha –1 and cropping period at160 days. The maximum sugar concentration was obtained at N = 120 kg ha –1, K = 155 kg ha –1 and cropping period at 130 days. The highest sugar yield was from N = 150 kg ha –1, K = 155 kg ha –1 and cropping period at 160 days. All factors and their interactions were statistically significant for all parameters assessed. Key Words: Beta vulgaris L., root yield, sugar yield, regression RéSUMé Le sucre est extrait des racines de la betterave (Beta vulgaris L.) en plus d'autres sources. Trois paramètres économiques importants sont souvent considérés notamment le rendement en racines, la concentration en sucre et le rendement en sucre. Tous les trois sont affectés par la période culturale et l'utilisation des engrais. La littérature existante suggère l'utilisation de l'azote et du potassium comme engrais. Une expérience de trois ans avec différentes combinaisons d'engrais en N et K pour différentes périodes culturales était conduite avec plusieurs répétitions. Le rendement le plus élevé était obtenu avec la combinaison N=150 kg/ha, K=155 kg/ha et une période de culture de 160 jours. La concentration maximale était obtenue pour N=120 kg/ha, K =155 kg/ha et une période de culture de 130 jours. Le rendement en sucre le plus élevé correspondait au traitement N=150 kg/ha, K=155 kg/ha et une période culturale de 160 jours. Tous les facteurs et leurs interactions étaient statistiquement significatifs pour les trois paramètres considérés. Mots Clés: Beta vulgaris L., rendement en racines, rendement, régression African Crop Science Journal Vol.11(4) 2003: 259-268
Doppler Shift Impact On The MIMO OFDM System In Vehicular Channel Condition
Samarendra Nath Sur,Rabindranath Bera
International Journal of Information Technology and Computer Science , 2012,
Abstract: Vehicle-to-vehicle (V2V) communication systems will play an important role in intelligent transportation systems (ITS). But in high mobility road condition, orthogonal frequency division multiplexing (OFDM) is very sensitive to Doppler shift. In this scenario multiple input and multiple output (MIMO) system combined with OFDM, make MIMO -OFDM techniques very attractive and productive for vehicle-to-vehicle communications. This paper deals with the bit error rate (BER) performance analysis of MIMO-OFDM system in high way road condition which is modeled based on the Nakagami fading characteristic. The system performance is analyzed with the change in m value of Nakagami channel and also with the variation in the modulation schemes.
Techniques of Glaucoma Detection From Color Fundus Images: A Review
Malaya Kumar Nath,Samarendra Dandapat
International Journal of Image, Graphics and Signal Processing , 2012,
Abstract: Glaucoma is a generic name for a group of diseases which causes progressive optic neuropathy and vision loss due to degeneration of the optic nerves. Optic nerve cells act as transducer and convert light signal entered into the eye to electrical signal for visual processing in the brain. The main risk factors of glaucoma are elevated intraocular pressure exerted by aqueous humour, family history of glaucoma (hereditary) and diabetes. It causes damages to the eye, whether intraocular pressure is high, normal or below normal. It causes the peripheral vision loss. There are different types of glaucoma. Some glaucoma occurs suddenly. So, detection of glaucoma is essential for minimizing the vision loss. Increased cup area to disc area ratio is the significant change during glaucoma. Diagnosis of glaucoma is based on measurement of intraocular pressure by tonometry, visual field examination by perimetry and measurement of cup area to disc area ratio from the color fundus images. In this paper the different signal processing techniques are discussed for detection and classification of glaucoma.
Paddy field soil conservation: Indian historical practices  [PDF]
Deepak Bhattacharya
Agricultural Sciences (AS) , 2011, DOI: 10.4236/as.2011.23045
Abstract: India is an ancient land having high seasonal rain fall (4 months rain & 8 months dry), has paddy cultivation. Becauses silt-sand separation; buoyant sand gets carried; silt agglutinates. Rill fluid dissolves agglutinated soil; vectors as silt → degradation. Indian farmer has unique agricultural field conservation; soil cum fertility maintenance/regeneration heritage. Also use the stubble and cow dung (cellulose) as binder cum multi purpose in-field uses. economic; ecologically safe; and not discussed earlier. Good tool for altruistic administrations.
Relevance of Economic Field Microscope in Remote Rural Regions for Concurrent Observation of Malaria & Inflammation  [PDF]
Deepak Bhattacharya
Advances in Infectious Diseases (AID) , 2012, DOI: 10.4236/aid.2012.21003
Abstract: Based on mono station use for >12 continuous years (since 1998) in drug resistant core endemic region, India, anti-inflammatory effect on WBC is demonstrated using a simple; economic monocular microscope that can be used out in the open—using day light/lamp. Is infinitely helpful for rural clinicians and the administrations, in developing nations. Although indispensable, a field microscope has become expensive; is in short supply; there is a crying need in the rural and the remote.
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