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Shiv Nadar University

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Bakshi A.,Shiv Nadar University
IEEE Transactions on Power Delivery | Year: 2015

During the winding process of a transformer, a residual strain is induced in its windings conductors. In this paper, the effect of the strain on the mechanical strength of transformer windings under the worst case condition of the short circuit has been investigated. The distribution of the residual strain in the conductors during its winding process has been determined analytically. The strain induced in the conductors under the action of radial short-circuit forces has been computed. The two strains are then added to obtain a resulting strain. By using the Ramberg-Osgood stress-strain relation of the conductor (copper) material, resulting stress is determined. A case study has been given where the presence of residual strain in the conductors of a power transformer has been taken into account for determining its mechanical strength under the worst case condition of short circuit. © 2015 IEEE.


Upadhyay R.K.,Shiv Nadar University | Soin N.,University of Bolton | Roy S.S.,Shiv Nadar University
RSC Advances | Year: 2014

With a rapidly growing population, development of new materials, techniques and devices which can provide safe potable water continues to be one of the major research emphases of the scientific community. While the development of new metal oxide catalysts is progressing, albeit at a slower pace, the concurrent and rapid development of high surface area catalyst supports such as graphene and its functionalised derivatives has provided unprecedented promise in the development of multifunctional catalysts. Recent works have shown that metal oxide/graphene composites can perform multiple roles including (but not limited to): photocatalysts, adsorbents and antimicrobial agents making them an effective agent against all major water pollutants including organic molecules, heavy metal ions and water borne pathogens, respectively. This article presents a comprehensive review on the application of metal oxide/graphene composites in water treatment and their role as photocatalyst, adsorbent and disinfectant in water remediation. Through this review, we discuss the current state of the art in metal oxide/graphene composites for water purification and also provide a comprehensive analysis of the nature of interaction of these composites with various types of pollutants which dictates their photocatalytic, adsorptive and antimicrobial activities. The review concludes with a summary on the role of graphene based materials in removal of pollutants from water and some proposed strategies for designing of highly efficient multifunctional metal oxide/graphene composites for water remediation. A brief perspective on the challenges and new directions in the area is also provided for researchers interested in designing advanced water treatment strategies using graphene based advanced materials. © 2013 The Royal Society of Chemistry.


Vyas V.,Shiv Nadar University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The heavy quark potential is calculated in the framework of gauge/gravity duality using the large-D approximation, where D is the number of dimensions transverse to the flux tube connecting a quark and an antiquark in a flat D+2-dimensional spacetime. We find that in the large-D limit the leading correction to the ground-state energy, as given by an effective Nambu-Goto string, arises not from the heavy modes but from the behavior of the massless modes in the vicinity of the quark and the antiquark. We estimate this correction and find that it should be visible in the near-future lattice QCD calculations of the heavy quark potential. © 2013 American Physical Society.


Manna D.,Indian Institute of Science | Roy G.,Shiv Nadar University | Mugesh G.,Indian Institute of Science
Accounts of Chemical Research | Year: 2013

Thyroid hormones are essential for the development and differentiation of all cells of the human body. They regulate protein, fat, and carbohydrate metabolism. In this Account, we discuss the synthesis, structure, and mechanism of action of thyroid hormones and their analogues.The prohormone thyroxine (T4) is synthesized on thyroglobulin by thyroid peroxidase (TPO), a heme enzyme that uses iodide and hydrogen peroxide to perform iodination and phenolic coupling reactions. The monodeiodination of T4 to 3,3′,5-triiodothyronine (T3) by selenium-containing deiodinases (ID-1, ID-2) is a key step in the activation of thyroid hormones. The type 3 deiodinase (ID-3) catalyzes the deactivation of thyroid hormone in a process that removes iodine selectively from the tyrosyl ring of T4 to produce 3,3′,5′-triiodothyronine (rT3). Several physiological and pathological stimuli influence thyroid hormone synthesis. The overproduction of thyroid hormones leads to hyperthyroidism, which is treated by antithyroid drugs that either inhibit the thyroid hormone biosynthesis and/or decrease the conversion of T4 to T3.Antithyroid drugs are thiourea-based compounds, which include propylthiouracil (PTU), methimazole (MMI), and carbimazole (CBZ). The thyroid gland actively concentrates these heterocyclic compounds against a concentration gradient. Recently, the selenium analogues of PTU, MMI, and CBZ attracted significant attention because the selenium moiety in these compounds has a higher nucleophilicity than that of the sulfur moiety. Researchers have developed new methods for the synthesis of the selenium compounds. Several experimental and theoretical investigations revealed that the selone (Cî-Se) in the selenium analogues is more polarized than the thione (Cî-S) in the sulfur compounds, and the selones exist predominantly in their zwitterionic forms.Although the thionamide-based antithyroid drugs have been used for almost 70 years, the mechanism of their action is not completely understood. Most investigations have revealed that MMI and PTU irreversibly inhibit TPO. PTU, MTU, and their selenium analogues also inhibit ID-1, most likely by reacting with the selenenyl iodide intermediate. The good ID-1 inhibitory activity of PTU and its analogues can be ascribed to the presence of the -N(H)-C(î-O)- functionality that can form hydrogen bonds with nearby amino acid residues in the selenenyl sulfide state. In addition to the TPO and ID-1 inhibition, the selenium analogues are very good antioxidants. In the presence of cellular reducing agents such as GSH, these compounds catalytically reduce hydrogen peroxide. They can also efficiently scavenge peroxynitrite, a potent biological oxidant and nitrating agent. © 2013 American Chemical Society.


Lochab B.,Shiv Nadar University | Shukla S.,Shiv Nadar University | Varma I.K.,Indian Institute of Technology Delhi
RSC Advances | Year: 2014

Exploration of sustainable alternatives to chemicals derived from petro-based industries is the current challenge for maintaining the balance between the needs of a changing world while preserving nature. The major source for sustainable chemicals is either the natural existing plant sources or waste generated from agro-based industries. The utility of such resources will supplement new processed materials with different sets of properties and environmental friendliness due to their biodegradability and low toxicity during preparation, usage and disposal. Amongst other polymers used on a day-to-day basis, phenolic resins account for vast usage. Replacement of petro-based monomers such as phenol and its derivatives either partly or completely utilized for the synthesis of such resins is ongoing. Extraction of natural phenolic components from cashew nut shell liquid, lignin, tannin, palm oil, coconut shell tar or from agricultural and industrial waste, and their utilization as synthons for the preparation of bio-based polymers and properties obtained are reviewed in this paper. This review article is designed to acknowledge efforts of researchers towards the "3C" motto-not only trying to create but also adapting the principles to conserve and care for a sustainable environment. This review paper describes how extraction, separation and recovery of desired phenolic compounds have occurred recently; how substituted phenol compounds, unmodified and modified, act as monomers for polymerization; and how the presence of sustainable phenolic material affects the properties of polymers. There are about 600 references cited and still there is a lot to uncover in this research area. This journal is © the Partner Organisations 2014.


Singh R.P.,Chapman University | Kaskaoutis D.G.,Shiv Nadar University
Eos | Year: 2014

For more than 2 decades, crop residues in Punjab, a region spanning northwestern India and eastern Pakistan, have been burned during October and November to ready fields for the next year's planting. This practice poses a serious threat to air quality in South Asia. ©2014. American Geophysical Union. All Rights Reserved.


Foy J.T.,University of Strasbourg | Ray D.,Shiv Nadar University | Aprahamian I.,Dartmouth College
Chemical Science | Year: 2014

Proton relay plays an important role in many biocatalytic pathways. In order to mimic such processes in the context of molecular switches, we developed coordination-coupled deprotonation (CCD) driven signaling and signal enhancement sequences. This was accomplished by using the zinc(ii)-initiated CCD of a hydrazone switch to instigate an acid catalyzed imine bond hydrolysis that separates a quencher from a fluorophore thus leading to emission amplification. Because CCD is a reversible process, we were able to show that the catalysis can be regulated and turned "on" and "off" using a metalation/demetalation cycle. This journal is © The Royal Society of Chemistry.


Kumar S.,Shiv Nadar University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

We consider four nontrivial ensembles involving Gaussian Wigner and Wishart matrices. These are relevant to problems ranging from multiantenna communication to random supergravity. We derive the matrix probability density, as well as the eigenvalue densities for these ensembles. In all cases the joint eigenvalue density exhibits a biorthogonal structure. A determinantal representation, based on a generalization of Andréief's integration formula, is used to compactly express the r-point correlation function of eigenvalues. This representation circumvents the complications encountered in the usual approaches, and the answer is obtained immediately by examining the joint density of eigenvalues. We validate our analytical results using Monte Carlo simulations. © 2015 American Physical Society.


Dumka U.C.,Aryabhatta Research Institute of Observational science | Kaskaoutis D.G.,Shiv Nadar University
Atmospheric Environment | Year: 2014

Regular near-surface measurements of aerosol scattering and absorbing coefficients, along with other aerosol and meteorological parameters, were performed during June 2011 to March 2012 at Nainital, central Himalayas in the frameworks of Ganges Valley Aerosol Experiment (GVAX). The spectral scattering (0.45, 0.55 and 0.70μm) and absorption (0.467, 0.53 and 0.66μm) coefficients exhibit increased values in November, mostly affected by the biomass-burning aerosols in Indo-Gangetic Plains. Both parameters are considered for fine (D<1μm) and sub-10μm particles (D<10μm) revealing the influence of particle size in aerosol properties. Furthermore, estimations of spectral (0.467, 0.55 and 0.66μm) single scattering albedo (SSA) and aerosol radiative forcing efficiency (ARFE) at 0.55μm were performed focussing on determination of the role of particle size in spectral SSA and climate implications. The results show relatively high SSA values ranging from 0.90 (±0.09) to 0.95 (±0.01) for D<10μm, and from 0.87 (±0.10) to 0.93 (±0.02) for D<1μm particles, on monthly basis, suggesting large heterogeneity in the aerosol sources. The SSA for the sub-micron aerosols decreases with wavelength in the majority of the cases, in contrast to the increase for the super-micron particles suggesting different source apportionment for the particle groups. The ARFE at the top of the atmosphere is found to range from -3 to -20Wm-2 with a mean of ~-17Wm-2 for both particle-size groups; however, during the June-October period, the ARFE for the sub-10μm particles is found to be more negative than that for the fine aerosols. © 2014 Elsevier Ltd.


Reddy L.V.R.,CSIR - Central Electrochemical Research Institute | Reddy L.V.R.,Albany Molecular Research | Kumar V.,CSIR - Central Electrochemical Research Institute | Kumar V.,Indian Institute of Science | And 3 more authors.
Chemical Reviews | Year: 2013

The presence of hydroxyl functionalities and well-defined chiral centers in carbohydrates as well as their natural abundance have attracted chemists worldwide to exploit this class of molecules as precursors for synthesis of a large number of natural products and biologically active molecules during recent decades. Apart from that, various types of molecules have also been synthesized from carbohydrates with a view to using them to study biological phenomena taking place in living systems. Use of cycloadditions in organic synthesis is ubiquitous, mostly because in one step multiple stereocenters can be generated in the desired molecule with high selectivities and usually good yields. A close examination revealed that the size of the nitrogen substituent influenced the rotational preference with the larger substituent providing higher diastereomeric ratio.

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