Dynamic multiscaling in two-dimensional fluid turbulence

We obtain, by extensive direct numerical simulations, time-dependent and equal-time structure functions for the vorticity, in both quasi-Lagrangian and Eulerian frames, for the direct-cascade regime in two-dimensional fluid turbulence with air-drag-induced friction. We show that different ways of extracting time scales from these time-dependent structure functions lead to different dynamic-multiscaling exponents, which are related to equal-time multiscaling exponents by different classes of bridge relations; for a representative value of the friction we verify that, given our error bars, these bridge relations hold.     

Persistence problem in two-dimensional fluid turbulence

We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter Λ to distinguish between vortical and extensional regions. We then use a direct numerical simulation of the two-dimensional, incompressible Navier-Stokes equation with Ekman friction to study probability distribution functions (PDFs) of the persistence times of vortical and extensional regions by employing both Eulerian and Lagrangian measurements. We find that, in the Eulerian case, the persistence-time PDFs have exponential tails; by contrast, this PDF for Lagrangian particles, in vortical regions, has a power-law tail with an exponent θ=2.9±0.2.     

Gold nanoparticle induced conformational changes in heme protein

Change of α-helical structure of heme protein (Hb) to a β-sheet and random coil conformation because of the interaction of glycine capped gold nanoparticles (20–60 nm) as observed from attenuation total reflectance, absorption, Fourier transform infra red, and Circular Dichroism spectroscopy has been reported in this article. Upon interaction, protein takes a cylindrical shape of length 12 μm and diameter 0.35 μm as revealed from scanning electron microscopy and transmission electron microscopy. The Selected-Area Electron beam Diffraction pattern shows change of crystalline structure in GNP to amorphous nature with the interaction of Hb.     

Instabilities in free-surface electroosmotic flows

Instability of a thin electrolyte film undergoing a direct current electroosmotic flow has been investigated. The film with a compliant electrolyte–air interface is flowing over a rigid charged substrate. Unlike previous studies, inclusion of the Maxwell stresses in the formulation shows the presence of a new finite wavenumber shear-flow mode of instability, alongside the more frequently observed long-wave interfacial mode. The shear mode is found to be the dominant mode of instability when the electrolyte–solid and electrolyte–air interfaces are of opposite charge or of same charge but have very large zeta-potential at the electrolyte–air interface. The conditions for mode-switch (interfacial to shear) and the direction of the travelling waves are discussed through stability diagrams. Interestingly, the analysis shows that when the interfaces are of nearly same zeta potential, the ‘free’ electrolyte–air interface behaves more like a ‘stationary’ wall because of the ion transport in the reverse direction of the flow.     

Phonon dispersion in aluminium arsenide and antimonide

The phonon dispersion curves for aluminium arsenide and antimonide have been investigated by using a deformation bond approximation model. The results obtained from this model are compared with the experimental values wherever it is available. Since there is no complete experimental phonon dispersion curves for AlAs, we could not compare our calculated results, but the results of AlSb have been compared with the inelastic neutron scattering measurements at 15 K. However, we compare the phonon frequencies of AlAs and AlSb at critical points of the Brillouin zone obtained by our calculations and Raman spectroscopy measurements. This model predicts the phonon modes satisfactorily in all the symmetry directions of the Brillouin zone (BZ). The spectrum has similar features as observed in other III–V compound semiconductors.     

Lattice vibrational properties of uranium pnictides

Lattice vibrational properties of uranium pnictides have been studied using breathing shell model (BSM) which includes breathing motion of electrons of the U-atoms due tof−d hybridization. The phonon dispersion curves of U-pnicitides calculated from the present model agree reasonably well with the measured data. A comparison has been made between BSM and our results reported earlier obtained from three-body force rigid ion model to reveal the importance of the short-range electron-phonon interactions in these compounds. We also report, for the first time, the two phonon density of states and specific heat for these compounds.     

Kinetics and mechanisms of substitution of aqua-ligands in cis-diaqua-bis(bipyridyl)ruthenium(ll) ion by L-cysteine in aqueous medium

Transition Metal Chemistry - The title reaction has been studied spectrophotometrically and a rate-law established within the pH range 5.0 to 6.5, $$ {?...     

Calibration transfer between electronic nose systems for rapid In situ measurement of pulp and paper industry emissions

Electronic nose systems when deployed in network mesh can effectively provide a low budget and onsite solution for the industrial obnoxious gaseous measurement. For accurate and identical prediction capability by all the electronic nose systems, a reliable calibration transfer model needs to be implemented in order to overcome the inherent sensor array variability. In this work, robust regression (RR) is used for calibration transfer between two electronic nose systems using a Box–Behnken (BB) design. Out of the two electronic nose systems, one was trained using industrial gas samples by four artificial neural network models, for the measurement of obnoxious odours emitted from pulp and paper industries. The emissions constitute mainly of hydrogen sulphide (H₂S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in different proportions. A Box–Behnken design consisting of 27 experiment sets based on synthetic gas combinations of H₂S, MM, DMS and DMDS, were conducted for calibration transfer between two identical electronic nose systems. Identical sensors on both the systems were mapped and the prediction models developed using ANN were then transferred to the second system using BB–RR methodology. The results showed successful transmission of prediction models developed for one system to other system, with the mean absolute error between the actual and predicted concentration of analytes in mg L⁻¹ after calibration transfer (on second system) being 0.076, 0.1801, 0.0329, 0.427 for DMS, DMDS, MM, H₂S respectively.     

Derivatization of Coumarins at the Benzenoid Ring in Aqueous Medium

Some 6‐disubstituted, 8‐disubstituted, and/6,8‐disubstituted compounds have been prepared from coumarin, 7‐methylcoumarin, and 3,4‐benzocoumarin. The Reimer–Tiemann reaction, Lederer–Manasse reaction, bromination using molecular bromine as well as 2,4,4,6‐tetrabromocyclohex‐2,5‐dien‐1‐one, Elbs reaction, and diazocoupling have been carried under controlled conditions to obtain various derivatives. Further, several reactions of aldehyde derivatives of these coumarins have been carried on to prepare important functional compounds including some heterocycles. It is noteworthy that these aldehydes behave as phenolic aldehydes under alkaline conditions to undergo the Dakin reaction. The reactions are mostly carried in aqueous media involving a dianionic intermediate and hence fulfill one important criterion of green chemistry.