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Arora R.,University of DelhiDelhi | Kakkar R.,University of DelhiDelhi
Computational and Theoretical Chemistry | Year: 2017

The mechanism of the Wolff rearrangement of some deprotonated diazocarbonyl compounds has been studied using density functional calculations, for both the gas and aqueous phases. The anionic rearrangement of the deprotonated analogues proceeds in a similar manner to the neutral counterparts. In the gas phase, the syn and anti conformers form the deprotonated ketene product concertedly. In certain analogues, the reaction of the anti conformer occurs non-concertedly, involving a deprotonated carbene-like intermediate. The migratory aptitude is similar to that in the neutral rearrangement, except that methoxy and amino substituents exchange positions. © 2017 Elsevier B.V.

Nagarajan R.,University of DelhiDelhi | Ahmad S.,University of DelhiDelhi | Singh P.,University of DelhiDelhi
Inorganic Chemistry | Year: 2015

Oxyfluoride, K2CoOF4 with K2PtCl6 structure, has been stabilized from a perovskite-based KCoF3 complex by a simple oxidative anion insertion topochemical reaction. Similar structural transformations have been observed for Ni- and Mn-containing systems. The generation of such unusual compounds, by soft chemical methods, strengthens the efforts toward materials discovery. © 2015 American Chemical Society.

Vijayarangamuthu K.,University of DelhiDelhi | Rath S.,University of DelhiDelhi
International Journal of Applied Ceramic Technology | Year: 2015

Sensing of low concentrations of two nitroaromatic compounds, 1,2-dinitrotoluene and 2-nitrophenol, is presented. The sensing mechanism is based on surface-enhanced Raman scattering (SERS) using nanostructured tin oxide as the SERS-active substrate. The SnOx nanostructures are synthesized by a simple solgel method and doped with Ag and Au. The Raman signal of a low concentration of the analyte, otherwise extremely weak, becomes significant when the analytes are attached to these substrates. Doping of SnOx nanopowders with Ag and Au leads to a further increase in the Raman intensities. This study demonstrates the scope of ceramic-metal nanocomposites as convenient solid-state SERS sensors for low-level detection. © 2014 The American Ceramic Society.

Yadav A.,University of DelhiDelhi | Mathur P.,University of DelhiDelhi
Inorganica Chimica Acta | Year: 2015

Abstract Copper(II) complexes of a N-octylated bisbenzimidazolyl ligand are synthesized and characterized. These complexes carry out the oxidative dealkylation of 2,4,6-tri-tertbutylphenol (TTBP) using molecular oxygen to 2,6-ditertbutylbenzoquinone and 4,6-di-tertbutylbenzoquinone. The oxidation proceeds via a phenoxyl radical species detected spectrophotometrically, and by EPR. A reactive copper(II)-dioxygen species is involved that carries out the oxidation reaction. A comparison of the rates of formation of the 4,6-di-tert-butylbenzoquinone versus 2,6-di-tert-butylbenzoquinone suggests that alternative pathway may exist for the formation of the para-quinone derivative. Isolation of an intermediate 4,4′-peroxybis(2,4,6-tri-tert-butylcyclohexa-2,5-dienone species and its structural characterization supports the above contention. © 2015 Elsevier B.V.

Bandyopadhyay B.,University of DelhiDelhi | Schleicher D.R.G.,University of Concepción
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The reionization of helium describes the transition from its singly ionized state to a doubly ionized state in the intergalactic medium. This process is important for the thermal evolution of the intergalactic medium and influences the mean free path of photons with energies above 54.4 eV. While it is well known that helium reionization is mostly driven by the contribution of energetic quasars at z<6, we study here how helium reionization proceeds if there is an additional contribution due to the annihilation of dark matter. We explore the effects of different dark matter profiles for the dark matter clumping factor, which can significantly enhance the annihilation rate at late times. We find that the presence of dark matter annihilation enhances the He++ abundance at early stages where it would be zero within the standard model, and it can further increase during structure formation, reflecting the increase of the dark matter clumping factor. The latter is, however, degenerate with the buildup of the quasar contribution, and we therefore expect no significant changes at late times. We expect that future studies of the He+ Lyman α forest may help to assess whether the evolution is consistent with the contribution from quasars alone, or if an additional component may be required. © 2015 American Physical Society.

Rawat S.,University of DelhiDelhi | Rawat S.,LNJN National Institute of Criminology and Forensic ScienceDelhi
Indian Journal of Forensic Medicine and Toxicology | Year: 2016

DNA methylation is an epigenetic mechanism which plays a vital role in the control and regulation of gene expression. In the past few years DNA Methylation was widely investigated in Medical field to understand complex diseases, but of late there has been a surge in studies exploring its potential use in Forensic Science. The present review discusses the application of DNA methylation to decipher regularly encountered query faced by a criminalist which includes DNA authentication, Body fluid identification, paternity dispute, Ancestry, gender and age estimation and Identification of monozygotic twins. The review also gives an insight about DNA methylation limitations. © 2016, Indian Journal of Forensic Medicine and Toxicology. All rights reserved.

Rani P.,University of DelhiDelhi | Biswas P.,University of DelhiDelhi
Journal of Physical Chemistry B | Year: 2015

Hydration water dynamics around globular proteins have attracted considerable attention in the past decades. This work investigates the hydration water dynamics around partially/fully intrinsically disordered proteins and compares it to that of the globular proteins via molecular dynamics simulations. The translational diffusion of the hydration water is examined by evaluating the mean-square displacement and the velocity autocorrelation function, while the rotational diffusion is probed through the dipole-dipole time correlation function. The results reveal that the translational and rotational motions of water molecules at the surface of intrinsically disordered proteins/regions are less restricted as compared to those around globular proteins/ordered regions, which is reflected in their higher diffusion coefficient and lower orientational relaxation time. The restricted mobility of hydration water in the vicinity of the protein leads to a sublinear diffusion in a heterogeneous interface. A positive correlation between the mean number of hydrogen bonds and the diffusion coefficient of hydration water implies higher mobility of water molecules at the surface of disordered proteins, which is due to their higher number of hydrogen bonds. Enhanced hydration water mobility around disordered proteins/regions is also related to their higher hydration capacity, low hydrophobicity, and increased internal protein motions. Thus, we generalize that the intrinsically disordered proteins/regions are associated with higher hydration water mobility as compared to globular protein/ordered regions, which may help to elucidate their varied functional specificity. © 2015 American Chemical Society.

Kotla S.K.R.,University of DelhiDelhi | Choudhary D.,University of DelhiDelhi | Tiwari R.K.,Chapman University | Verma A.K.,University of DelhiDelhi | Verma A.K.,Jawaharlal Nehru UniversityDelhi
Tetrahedron Letters | Year: 2015

Abstract The Rh(III)-catalyzed oxidative coupling of 2-aryl-imidazopyridines with internal alkynes via double C-H activation has been described. This approach provides straightforward access to highly functionalized polycyclic imidazopyridines in good to excellent yields. © 2015 Elsevier Ltd.

Yadav H.,University of DelhiDelhi | Sinha N.,University of DelhiDelhi | Kumar B.,University of DelhiDelhi
Journal of Crystal Growth | Year: 2016

Organic non-linear optical pure and xylenol orange (XO) doped benzophenone (BP) single crystals have been grown by a modified Czochralski technique. A low cost CZ system was designed and fabricated that is suitable for the growth of single crystals of low melting point organic materials. Structural analysis was performed by powder and single crystal XRD. LC-HRMS spectra reveal that the dye molecules are present in the doped crystal. The linear optical characterization was carried out by UV–vis spectroscopy. In the case of the XO doped BP crystal, two absorption peaks were found at 504 nm and 620 nm. The enhancement of photoluminescence intensity of blue emission was observed in the dye doped crystal. Dielectric studies reveal that the XO doped BP has shown improved a dielectric constant with low dielectric loss. A dual band compact circular patch antenna was simulated and fabricated using the XO doped crystal. Resonant frequencies of the dual bands at 4.80 GHz and 9.22 GHz were achieved by introducing a defect ground state in the circular patch antenna. The piezoelectric coefficient (d33) value was increased from 1 to 4 pC/N by XO dye doping, which opens up the possibilities of simultaneous transducer applications. © 2016 Elsevier B.V.

Lumb S.,University of Delhi | Munjal D.,University of DelhiDelhi | Prasad V.,University of DelhiDelhi
Physica Scripta | Year: 2015

Exponential cosine screened Coulomb potential (ECSCP) has been widely used in various branches of physics e.g., solid-state physics, nuclear physics and plasma physics. The atomic photoionization processes under plasma shielding can serve as an efficient tool for study of plasma properties in various environments ranging from nano-scale devices to astrophysical objects. In the present study, ECSCP has been used to characterize a dense quantum plasma and its effect on the spectrum of an atom encaged in a spherical box has been investigated. The work has further been extended to study the response of such a system to a periodic laser field. Photoexcitation and ionization probabilities of the system have been studied as a function of applied laser field parameters using the non-perturbative Floquet technique. As the Floquet method requires exact energy values and oscillator strengths, the spectrum of confined system has been calculated using Bernstein-polynomial method. The variation of energy spectrum and oscillator strengths with screening as well as confinement parameters has also been explored. © 2015 The Royal Swedish Academy of Sciences.

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