Prabu V.,Indian Institute of Technology Guwahati
Applied Energy | Year: 2015
Underground coal gasification (UCG) is a clean coal technology to utilize deep coal resources effectively. In-situ CO2-oxy coal gasification may eliminate the operational difficulty of the steam gasification process and utilize CO2 (greenhouse gas) effectively. Furthermore, it is necessary to convert the clean gasified energy from the UCG into clean combustion energy for an end-use. In order to achieve efficient clean power production, the present work investigates the thermodynamic feasibility of integration of CO2 based UCG with power generating systems operating in a chemical looping combustion (CLC) of product gas. The use of CO enriched syngas from O2/CO2 based UCG reduces the difficulty of the heat balance between a fuel reactor and an air reactor in a nickel oxygen-carrier based CLC system. Thermodynamic analyses have been made for various routes of power generation systems such as subcritical, supercritical and ultra-supercritical boiler based steam turbines and gas turbines for the UCG integrated system. It is shown, based on mass and energy balance analysis, that the integration of CO2 based UCG with the CLC system reduces the energy penalty of carbon capture and storage (CCS) significantly. A net thermal efficiency of 29.42% is estimated for the CCS incorporated system, which operates in a subcritical condition based steam turbine power plant. Furthermore, it is found that the efficiency of the proposed steam turbine system increases to 35.40% for an ultra-supercritical operating condition. The effect of operating temperature of the air reactor and the fuel reactor of the CLC system on the net thermal efficiency of combined cycle power plant is investigated. It is found that a net thermal efficiency of 42.53% can be obtained for the CCS incorporated combined cycle power system operating at an air reactor temperature of 1200°C. © 2014 Elsevier Ltd.
Sengoden M.,Indian Institute of Technology Guwahati |
Punniyamurthy T.,Indian Institute of Technology Guwahati
Angewandte Chemie - International Edition | Year: 2013
In suspension: The reaction of aziridines with heterocumulenes in the presence of Fe(NO3)3×9 H2O in aqueous suspension provides access to functionalized five-membered heterocycles in good to high yields. This protocol has a wide substrate scope, is simple, and uses a nontoxic and cheap catalyst. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Pan S.C.,Indian Institute of Technology Guwahati
Beilstein Journal of Organic Chemistry | Year: 2012
Organocatalytic C-H activation reactions have recently been developed besides the traditional metal-catalysed C-H activation reactions. The recent non-asymmetric and asymmetric C-H activation reactions mediated by organocatalysts are discussed in this review. © 2012 Pan.
Sarma A.K.,Indian Institute of Technology Guwahati
Journal of the Optical Society of America B: Optical Physics | Year: 2014
We carry out a modulation instability (MI) analysis in nonlinear complex parity-time (PT) symmetric periodic structures. All three regimes defined by the PT-symmetry breaking point or threshold, namely, below threshold, at threshold, and above threshold, are discussed. It is found that MI exists even beyond the PT-symmetry threshold, indicating the possible existence of solitons or solitary waves, in conformity with some recent reports. We find that MI does not exist at the PT-symmetry breaking point in the case of normal dispersion below a certain nonlinear threshold. However, in the case of the anomalous dispersion regime, MI does exist even at the PT-symmetry breaking point. © 2014 Optical Society of America.
Jena H.S.,Indian Institute of Technology Guwahati
New Journal of Chemistry | Year: 2014
The diastereoselective self-assembly of five Cu(ii) heterochiral complexes containing a racemic Schiff base ligand LH (where LH = (R,S) 2-((1-(2-pyridyl)ethylimino)methyl)phenol in a chiral self-discriminating process is reported. Complexes 1-5 are synthesized using ligand LH, Cu(NO 3)2·3H2O, Cu(ClO4) 2·6H2O, and co-ligands such as N3 -, NCS-, NCO-, and are conclusively structurally characterized. Determination of the molecular structures of 1-5 confirmed the presence of a di-copper core with an inversion centre located directly between the two copper ions. In 1-5, each ligand in the di-copper core discriminates its own chirality and results in heterochiral dimerization in a chiral self-discriminating manner. The crystal packing pattern of compounds 1-5 are analyzed in terms of non-covalent C-H⋯O, C-H⋯N, C-H⋯π, and parallel displaced π⋯π interactions. In the crystal structure of compounds 1-4, there is a parallel displaced π⋯π interaction between the pyridine and benzene rings in the two adjacent heterochiral dimers, which act cooperatively with other different non-covalent interactions. In 2, the coordinated water molecule acts as a bifurcated H-bond donor to phenoxo-O and perchlorate-O in a diastereoselective and enantioselective manner, respectively. The results described here address new examples of the rarely occurring chiral self-discriminating process. This journal is © the Partner Organisations 2014.
Kasoju N.,Indian Institute of Technology Guwahati |
Bora U.,Indian Institute of Technology Guwahati
Advanced Healthcare Materials | Year: 2012
Tissue engineering (TE) is a multidisciplinary field that aims at the in vitro engineering of tissues and organs by integrating science and technology of cells, materials and biochemical factors. Mimicking the natural extracellular matrix is one of the critical and challenging technological barriers, for which scaffold engineering has become a prime focus of research within the field of TE. Amongst the variety of materials tested, silk fibroin (SF) is increasingly being recognized as a promising material for scaffold fabrication. Ease of processing, excellent biocompatibility, remarkable mechanical properties and tailorable degradability of SF has been explored for fabrication of various articles such as films, porous matrices, hydrogels, nonwoven mats, etc., and has been investigated for use in various TE applications, including bone, tendon, ligament, cartilage, skin, liver, trachea, nerve, cornea, eardrum, dental, bladder, etc. The current review extensively covers the progress made in the SF-based in vitro engineering and regeneration of various human tissues and identifies opportunities for further development of this field. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Malani R.S.,Indian Institute of Technology Guwahati
Journal of hazardous materials | Year: 2013
For degradation of biorefractory pollutants, enzymatic treatments and sonochemical treatments have shown high potential. A combined technique of sono-enzymatic treatment is of special interest as it has shown enhancement effect than the individual techniques. This work has attempted to give a mechanistic insight into the interaction of sonochemical and enzymatic treatments using immobilized horseradish peroxidase (HRP) enzyme on the decolourization of acid red dye (an azo dye). In order to segregate the effect of ultrasound and cavitation, experiments were conducted at elevated static pressure. The kinetic parameters of HRP, viz. Vmax and Km were marginally affected by immobilization. There was a minor change in pH optima and temperature optima for immobilized HRP (6.5, 25°C) from free HRP (7.0, 20-25°C). Though the specific activity of free enzyme (0.272U/mg) was found to be higher than the immobilized enzyme (0.104U/mg), immobilized enzyme exhibited higher stability (up to 3 cycles) and degradation potential than free enzyme in all experiments. The results revealed that the coupling of sonication and enzymatic treatment at high pressure in presence of polyethylene glycol (PEG) yielded the highest decolourization of acid red (61.2%). However, the total decolourization achieved with combined technique was lesser than the sum of individual techniques, indicating negative synergy between the sonochemical and enzymatic techniques. Copyright © 2013 Elsevier B.V. All rights reserved.
Paul S.,Indian Institute of Technology Guwahati
Journal of Physical Chemistry B | Year: 2014
We have carried out molecular dynamics simulation to investigate the role of trehalose molecules on the change in the structural and dynamical properties of aqueous N-methylacetamide (NMA) solution. In this study, we considered six different trehalose concentrations ranging from 0 to 66%. Results are discussed in the framework of hydrophobic interactions between different methyl groups of NMA, structure of the solutions, and hydrogen bonding interactions between different solution species. We observe that the propensity of hydrophobic association through the methyl groups of NMA is essentially insensitive to trehalose concentration except for higher trehalose concentration where the hydrophobic interactions between the hydrophobic methyl groups are getting reduced. Also observed are (i) trehalose induced slight collapse of the second hydration shell of water, (ii) presence of excess water molecules near NMA, and (iii) exclusion of trehalose from NMA. Our NMA-water radial distribution function analyses followed by average number of hydrogen bonds per NMA calculations reveal that, in the hydration of NMA molecules, its carbonyl group oxygen (over amide hydrogen) is predominantly involved. As trehalose is added, we observe, in accordance with the water replacement hypothesis, the replacement of water-NMA hydrogen bonds by NMA-trehalose hydrogen bonds, keeping the average number of hydrogen bonds formed by a single NMA with different solution species essentially unchanged. Our hydrogen bond calculations further reveal that addition of trehalose replaces water-NMA hydrogen bonds by water-trehalose hydrogen bonds. And as a result, we find that the average number of hydrogen bonds formed by a water molecule remain unchanged. We also find that addition of trehalose decreases the translational motion of all the solution species sharply. © 2014 American Chemical Society.
Maheshwari S.,Indian Institute of Technology Guwahati
Journal of the Royal Society, Interface / the Royal Society | Year: 2013
Fragmented QRS (f-QRS) has been proven to be an efficient biomarker for several diseases, including remote and acute myocardial infarction, cardiac sarcoidosis, non-ischaemic cardiomyopathy, etc. It has also been shown to have higher sensitivity and/or specificity values than the conventional markers (e.g. Q-wave, ST-elevation, etc.) which may even regress or disappear with time. Patients with such diseases have to undergo expensive and sometimes invasive tests for diagnosis. Automated detection of f-QRS followed by identification of its various morphologies in addition to the conventional ECG feature (e.g. P, QRS, T amplitude and duration, etc.) extraction will lead to a more reliable diagnosis, therapy and disease prognosis than the state-of-the-art approaches and thereby will be of significant clinical importance for both hospital-based and emerging remote health monitoring environments as well as for implanted ICD devices. An automated algorithm for detection of f-QRS from the ECG and identification of its various morphologies is proposed in this work which, to the best of our knowledge, is the first work of its kind. Using our recently proposed time-domain morphology and gradient-based ECG feature extraction algorithm, the QRS complex is extracted and discrete wavelet transform (DWT) with one level of decomposition, using the 'Haar' wavelet, is applied on it to detect the presence of fragmentation. Detailed DWT coefficients were observed to hypothesize the postulates of detection of all types of morphologies as reported in the literature. To model and verify the algorithm, PhysioNet's PTB database was used. Forty patients were randomly selected from the database and their ECG were examined by two experienced cardiologists and the results were compared with those obtained from the algorithm. Out of 40 patients, 31 were considered appropriate for comparison by two cardiologists, and it is shown that 334 out of 372 (89.8%) leads from the chosen 31 patients complied favourably with our proposed algorithm. The sensitivity and specificity values obtained for the detection of f-QRS were 0.897 and 0.899, respectively. Automation will speed up the detection of fragmentation, reducing the human error involved and will allow it to be implemented for hospital-based remote monitoring and ICD devices.
Ministry Of Science & Technology and Indian Institute of Technology Guwahati | Date: 2015-08-31
The present invention mainly relates to knee joint and more particularly to the polymeric composite or nanocomposites based polycentric knee joint. In one embodiment the knee joint comprising: a top part having a top face and a bottom face, wherein the top face having an adapter coupled firmly with the top part to transfer the load from the stump of amputee via socket, a bottom part having a top face and a bottom face, at least one middle linkage pivotably coupling a middle posterior region of the top part with a middle posterior region of the bottom part, at least two side identical linkage pivotably coupling a sides of the top part with a sides of the bottom part, a compression spring along with cylindrical rod positioned in the interior of the bottom part which provides the engaging and disengaging of the top and bottom part, at least two extension spring couples the top and bottom part through two tiny holes and through simple supported beam in the top and bottom part for the flexion and extension of the knee joint and a bumper positioned in the base of the bottom part which contacts with the pylon to absorb the vibration and the terminal impact during the hip hike.