Bhattacharya H.N.,Presidency College |
Bull S.,University of Tasmania
Precambrian Research | Year: 2010
The Paleoproterozoic Aravalli basin of Rajasthan, India hosts a number of Pb-Zn sulphide deposits. Various ore genetic models for these deposits are available in the literature, but none of them are backed by comprehensive basin models reconstructed on the basis of sedimentological analysis. In the present work an attempt has been made to propose an actualistic basin model for the Aravalli basin, which was conducive to Pb-Zn sulphide mineralization. The Zawar Mineralized Belt is one of the producing Pb-Zn sulphide belts in the Aravalli basin. The Aravalli sedimentary succession, which is developed on the basement rocks in the Zawar area, is more than 2500 m thick. The whole basin-fill succession, an unconformity-bounded single mega sequence, has been classified into four facies assemblages. The sedimentary facies attributes and their architecture in each facies assemblage advocate in favour of an ensialic rift basin, which experienced repeated down sagging and exhumation. Each foundering event of the rift basin was related to movements along some basin marginal and/or intrabasinal faults, which are manifestation of crustal stretching. Such faults were directly responsible for sediment dispersal in the basin. In this overall tectono-sedimentary frame the ore bearing sediments were deposited as a slope-base fan deposit in deep marine environment. The granitic basement derived sediments that underlie the mineralized horizons are conceived as a source for metals (Pb & B isotopic signatures in galena and tourmaline), and the intrabasinal faults that were active during sedimentation might have acted as conduits for upward transmission of the ore brine. © 2010 Elsevier B.V. All rights reserved.
News Article | November 30, 2016
The future scientist went to school with children of the "lowest" castes in what is now known as Bangladesh. He went on to play a crucial role in pioneering the breakthrough of radio technology, and he developed theories of plant biology which were only proven nearly a century later. He refused to take patents out on his own work. He even wrote science-fiction in his native language. Jagadish Chandra Bose, an overlooked scientist whose work allowed giant leaps at the beginning of the 20th century, is honored today, on what would be his 158th birthday, by a Google Doodle. Bose (1858-1937) was born into a well-to-do family, as his father was a deputy magistrate and assistant commissioner in the British colonial government. But the family’s ideas were progressive – and Bose started his education in a school with members of the lower castes. At that time, most students would want to be at an English school – but his father wanted him to learn in his native language first. Bose later recalled that he was inspired by starting his learning in such an environment. “In the vernacular school, to which I was sent, the son of the Muslim attendant of my father sat on my right side, and the son of a fisherman sat on my left. They were my playmates,” he said. “I listened spellbound to their stories of birds, animals and aquatic creatures. Perhaps these stories created in my mind a keen interest in investigating the workings of Nature.” Bose then went to Hindu College, and St. Xavier’s College in Calcutta. Although his sights were first set on a job in the Indian Civil Service, his father pushed him to be a scholar. He went to England to study medicine at the University of London – but dropped out because of ill health. Instead, he focused his attention on degrees in natural sciences at the University of Cambridge and the London University. Bose made a stand against discrimination upon his return to India. He secured a job through a colonial appointment of the viceroy at Presidency College. Undertaking research, he was allotted 100 rupees per month – while Europeans were offered 300 rupees. Bose refused the salary – and worked without any remuneration at all – for three full years. He apparently impressed his peers enough that they provided him with the full salary – with a retroactive lump sum for all his work. Bose made it worth their while. In a spectacular demonstration of the newly-discovered existence of electromagnetic waves in Calcutta in 1895, the scientist made a public demonstration of igniting gunpowder and ringing a bell using the invisible forces. Bose had essentially reduced electromagnetic waves to the level of millimeters – a logical progression of the physicists Heinrich Hertz in Germany, and Oliver Lodge in England. Bose essentially invented the “mercury coherer” that Guglielmo Marconi would use for his 2,000-mile transmission across the Atlantic in 1901, which has long been celebrated as the invention of radio. But Bose had a reflexive opposition to acquiring patents. He also invented a series of commonplace microwave components which are still fundamentally in use – but never sought financial or other credit for them. (Some other contemporaries, like Pierre Curie and Wilhelm Roentgen, were also fundamentally opposed to the concept of patents). Bose also was fascinated with plants. His theory of how sap moves up plants was proposed as a pumping action of cells in the endodermis was later proven correct – and he also demonstrated the electrical stimulus at work in plants. The crescograph, a tool of high magnification sued to detect movement and growth of plants, also went unpatented. In both the physics and botanical realms, Bose has been described several times as being 50 to 60 years ahead of his time.
Dey A.,Presidency College
African journal of traditional, complementary, and alternative medicines : AJTCAM / African Networks on Ethnomedicines | Year: 2012
Snakebite has been a major cause of mortality across the tropical countries including Indian subcontinent. The present review deals with the enormous amount of ethnobotanical work performed in the last few years involving use of different plants against snakebite in Indian subcontinent (India, Bangladesh, Pakistan and Nepal). From a variety of literature sources the data has been compiled mentioning the plants, parts used, dosage, mode of administration, name of the ethnic communities, geographical locations etc. depending on the availability of information.
Dasgupta P.,Presidency College |
Manna P.,Presidency College
Earth-Science Reviews | Year: 2011
The grain-flow has so far been defined with reference to the distinctive sediment-support mechanism, the dispersive pressure. The role of sediment-support mechanism, however, is required in a multiphase flow to prevent the gravitational settling of the particles through the driving medium during the flow. In a single-phase flow of non-cohesive grains no such secondary mechanism is required to counteract the gravitational pull, the driving force of the flow. So the definition of grain-flow needs a critical revision. This, in turn, involves proper understanding of the grain-flow mechanism, so that the relation between the process and the product can be properly established. The most distinctive feature often demonstrated by a grain-flow deposit is the particle size segregation, which leads to the development of inverse grading. The available explanations for this phenomenon find theoretical constraints. In the present study an attempt was made to understand the mechanism of single-phase non-cohesive granular flow of different flow regime and the particle segregation pattern in the resultant deposit through laboratory simulation. The experimental observations revealed that no sustained granular flow sets in on a slope deviating much from the limiting value of the angle of repose of the granular material. A persistent simple shear flow develops on slopes of this critical value. Each of the grains rolls in response to simple shearing. If the shear stress attains a critical value, theoretically the larger grains can even climb up the adjacent smaller ones towards the down-slope direction. In reality, however, high angle climb is not very common. The larger grains preferably roll over the smaller grains when the common tangent becomes almost horizontal or makes a very low angle with the direction of flow, and by this process gradually reaches the upper surface of the flow causing the development of inverse grading. The upper surface of the resultant deposit remains parallel to the sloping substratum. These properties readily distinguish this variety of granular flow from the other natural flows, and the flow may thus be assigned the distinct status of grain-flow. © 2010 Elsevier B.V.
Acharyya M.,Presidency College
European Journal of Physics | Year: 2010
Usually, we study the statistical behaviour of noninteracting fermions in finite (mainly two and three) dimensions. For a fixed number of fermions, the average energy per fermion is calculated in two and in three dimensions, and it becomes equal to 50% and 60% of the Fermi energy respectively. However, in higher dimensions this percentage increases as the dimensionality increases, and in infinite dimensions it becomes 100%. This is an interesting result, at least pedagogically, which implies that all fermions are moving with Fermi momentum. This result is not yet discussed in standard text books of quantum statistics. Here this fact is discussed and explained. I hope that this letter will be helpful for graduate students to study the behaviours of free fermions in generalized dimensionality. © 2010 IOP Publishing Ltd.
Datta J.,Bengal Engineering and Science University |
Dutta A.,Bengal Engineering and Science University |
Biswas M.,Presidency College
Electrochemistry Communications | Year: 2012
This work reports improved electrode kinetics of ethanol oxidation on the conducting polymer composite matrix, poly-vinyl carbazole (PNVC) crossed linked with V 2O 5 and embedded with Pt-Pd nano crystallites. The metal incorporated polymer composite produces much higher current for ethanol electro-oxidation in alkaline medium compared to their carbon supported counterpart. The former also exhibits higher tolerance to CO-poisoning leading to a satisfactory level of ethanol conversion to the end products as estimated by chromatographic analysis. The structure and morphology of the catalysts surface were determined by SEM and XRD analysis. Various electrochemical techniques were employed to evaluate the kinetic parameters related to electro-oxidation of ethanol. Activation energy for the oxidation reaction is remarkably reduced, using the PNVC support, consistently throughout an extended potential region. © 2012 Elsevier B.V. All rights reserved.
Dey A.,Presidency College
Journal of Applied Pharmaceutical Science | Year: 2011
Alstonia scholaris is a traditionally important medicinal plant. This evergreen tree is native to the Indian subcontinent and Southeast Asian countries. The plant is used in traditional, Ayurvedic, Unani, Homoeopathy and Sidhha/Tamil types of alternative medicinal systems against different ailments such as asthma, malaria, fever, dysentery, diarrhea, epilepsy, skin diseases, snakebite etc. Among the phytochemicals, alkaloids are mostly reported. This review compiles reports on phytochemical and pharmacological aspects of A. scholaris.
Debnath S.,Presidency College |
Ghosh U.C.,Presidency College
Desalination | Year: 2011
Adsorption reactions of Cd(II) and Cu(II) with nanoparticle agglomerates of titanium(IV) oxide (NHTO) were investigated from single and bi-component systems at optimized pH 5.0. Kinetic data of metal ion removal reactions described the pseudo-second order equation very well. Both Langmuir and Redlich-Peterson models described the equilibrium data well (R 2>0.95). Values of the monolayer adsorption capacities (mg·g -1) of Cd(II) (49.50 to 60.24) and Cu(II) (42.02 to 52.63) were high, and that increased with increasing temperature on the reactions. Thermodynamic analyses of the equilibrium data suggested that the removal reactions were spontaneous [-δG 0, kJ·mol -1=24.31 to 32.73 for Cd(II); and 19.62 to 27.38 for Cu(II)]. Spontaneity of the reactions increased with increasing temperature. Langmuir monolayer adsorption capacity of either Cd(II) or Cu(II) was less in presence of each other than that of single component systems. The mean adsorption energy estimation suggested that the interaction between either of the metal ions with NHTO was columbic type. About 71 to 75% of adsorbed metal ions could be recovered as the metal oxide from their solutions, which were obtained by the desorption reaction with 0.1M HCl. © 2011 Elsevier B.V.
Mukherjee P.K.,Presidency College
Journal of Chemical Physics | Year: 2010
We present a mean-field description of the phase transitions, which are obtained when cooling from the isotropic liquid to the first liquid crystalline phase in compounds composed of achiral banana-shaped molecules. We put special emphasis on the isotropic to antiferroelectric B2 phase transition. The free energy is written in terms of the coupled order parameters including the antiferroelectric polarization. We present a detailed analysis of the different phases that can occur and analyze the question under which conditions a direct isotropic to antiferroelectric B2 phase transition is possible when compared with other phase transitions. The theoretical results are found to be in qualitative agreement with all published experimental results. © 2010 American Institute of Physics.
Mukherjee P.K.,Presidency College
Journal of Physical Chemistry B | Year: 2010
The first theoretical observation of the tricritical point for the rotator-I to rotator-V phase transition of normal alkanes is reported. The influence of pressure on the rotator-II-rotator-I-rotator-V phase sequence in normal alkanes has been studied within the Landau phenomenological theory. Our results show that for a particular value of pressure the first-order rotator-I to rotator-V phase transition becomes second-order at a tricritical point. We outline how the novel phase diagram could be detected experimentally. © 2010 American Chemical Society.