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.     

Study on the structure functions of electrons and the energy flow in the soft component of cosmic-ray extensive air showers

Summary Cosmic-ray air shower structure functions for the distance dependence of electron density in cosmic-ray air showers in the size range 10⁴⋎10⁸ have been computed for their intercomparison and comparison with Monte Carlo simulation results and measurements from recent experiments. The analysis has yielded the present status of theoretical structure functionsvis à vis experimental results and Monte Carlo simulation distributions. The effect of core location error on the lateral distribution of electrons is also discussed from the point of view of different theoretical and experimental results. The energy flow in the soft component of air showers of size ∼4·10⁵ has been evaluated within a ring of radius 10m about the axis of the showers.     

Predicting properties of molecules using graph invariants

Topological indices (TIs) have been used to study structure-activity relationships (SAR) with respect to the physical, chemical, and biological properties of congeneric sets of molecules. Since there are many TIs and many are correlated, it is important that we identify redundancies and extract useful information from TIs into a smaller number of parameters. Moreover, it is important to determine if TIs, or parameters derived from TIs, can be used for global SAR models of diverse sets of chemicals. We calculated seventy-one TIs for three groups of molecules of increasing complexity and diversity: (a) 74 alkanes, (b) 29 alkylbenzenes, and (c) 37 polycyclic aromatic hydrocarbons (PAHs). Principal components analysis (PCA) revealed that a few principal components (PCs) could extract most of the information encoded by the seventy-one TIs. The structural basis of the first few PCs could be derived from their pattern of correlation with individual TIs. For the three sets of molecules, viz. alkanes, alkylbenzenes and PAHs, PCs were able to predict the boiling points reasonably well. Also, for the combined set of 140 chemicals consisting of the alkanes, alkylbenzenes and PAHs, the derived PCs were not as effective in predicting properties as in the case of individual classes of compounds.     

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.