A resonance Raman,surface-enhanced resonance Raman,IR, and ab initio vibrational spectroscopic study of nickel(II) tetraazaannulene complexes

The IR and resonance Raman spectra of the nickel(II) complexes of dibenzo[b,i][1,4,8,11]tetraaza[14]annulene (TAA) and 5,7,12,14-tetramethyldibenzo[b,i][1,4,8,11]tetraaza[14]annulene (TMTAA) have been measured and compared with ab initio calculations of the vibrational wavenumbers at the B3-LYP level using the LanL2DZ basis set. An excellent fit is found between the experimental and calculated data, enabling precise vibrational assignments to be made. Surface-enhanced resonance Raman spectra were obtained following adsorption on Ag electrodes, with potentials in the range -0.1 to -1.1 V vs Ag/AgCl. There is evidence for contributions from both the electromagnetic and charge transfer (CT) surface enhancement mechanisms. The data indicate that variations in band intensities with electrode potential can be interpreted in terms of the CT mechanism.     

Metachronal propulsion of non-Newtonian viscoelastic mucus in an axisymmetric tube with ciliated walls

Cilia-induced flow of viscoelastic mucus through an idealized two-dimensional model of the human trachea is presented.The cilia motion is simulated by a metachronal wave pattern which enables the mobilization of highly viscous mucus even at nonzero Reynolds numbers.The viscoelastic mucus is analyzed with the upper convected Maxwell viscoelastic formulation which features a relaxation time and accurately captures normal stress generation in shear flows.The governing equations are transformed from fixed to wave(laboratory)frame with appropriate variables and resulting differential equations are perturbed about wave number.The trachea is treated as an axisymmetric ciliated tube.Radial and axial distributions in axial velocity are calculated via the regular perturbation method and pressure rise is computed with numerical integration using symbolic software MATHEMATICA^‘TM’.The influence of selected parameters which is cilia length,and Maxwell viscoelastic material parameter i.e.relaxation time for prescribed values of wave number are visualized graphically.Pressure rise is observed to increase considerably with elevation in both cilia length and relaxation time whereas the axial velocity is markedly decelerated.The simulations provide some insight into viscous-dominated cilia propulsion of rheological mucus and also serve as a benchmark for more advanced modeling.     

Effect of heat transfer on a third grade fluid in a flat channel

The heat transfer analysis on the laminar flow of an incompressible third grade fluid through a porous flat channel is examined. The lower plate is assumed to be at a higher temperature than the upper plate. Analytical solution for temperature distribution is obtained for various values of the controlling parameters and discussed. The obtained analytical solution is also compared with the numerical solution. The comparison shows the fact that the accuracy is remarkable. Copyright © 2009 John Wiley & Sons, Ltd.     

Homotopy Solution for the Channel Flow of a Third Grade Fluid

The solution for the flow of a third grade fluid bounded by two parallel porous plates is given using homotopy analysis method (HAM). A comparison is made with the exact numerical solution for the various values of the physical parameters. It is found that a proper choice of the auxiliary parameter occurring in HAM solution gives very close results.     

Exact solutions for flows of an Oldroyd 8-constant fluid with nonlinear slip conditions

In the present investigation the exact analytical solutions for three fundamental flows namely the Couette, Poiseuille and generalized Couette are obtained. The resulting problems involve nonlinear equations and nonlinear boundary conditions. Finally the influence of the emerging parameters is discussed by plotting graphs.     

Intra-uterine particle–fluid motion through a compliant asymmetric tapered channel with heat transfer

Journal of Thermal Analysis and Calorimetry - In this article, the intra-uterine flow with small suspended particles under the impact of heat transfer is investigated. Intra-uterine fluid motion...     

Exact solution of a thin film flow of an Oldroyd 6-constant fluid over a moving belt

We obtain exact solutions for thin film flow of an Oldroyd 6-constant fluid on a vertically moving belt. These are compared with the homotopy perturbation results of Siddiqui et al. [Siddiqui AM, Ahmed M, Ghori QK. Thin film flow of non-Newtonian fluids on a moving belt. Chaos, Solitons & Fractals 2007;33(3):1006–1016.].     

Biologically inspired thermal transport on the rheology of Williamson hydromagnetic nanofluid flow with convection: an entropy analysis

Journal of Thermal Analysis and Calorimetry - The present article deals with entropy analysis and mass transfer process on asymmetric peristaltic propulsion of nanofluid under convection and...     

Fundamental flows with nonlinear slip conditions: exact solutions

In this article, we use nonlinear slip conditions to investigate three fundamental flows. Constitutive equations of the third grade fluid give rise to nonlinear equations. Exact analytic solutions of the nonlinear equations with nonlinear boundary conditions are developed. Numerical values between the dimensionless third grade and slip parameters are tabulated. Graphs are plotted and discussed.     

The influence of Hall current in a circular duct

In this paper, we consider the unsteady flow of an incompressible second grade fluid in a circular duct with a given volume flow rate variation. The effects of Hall current are taken into account. The governing equations are solved analytically using Laplace transform method. The velocity profiles are constructed for the four cases: (a) constant accelerated flow (b) sudden started flow (c) the flow rate has a trapezoidal variation with time (d) starting from rest the volume flow rate oscillates sinusoidally. The present analysis is more general than any previous investigation.