The onset of double diffusive convection in a viscoelastic fluid layer

The onset of double diffusive convection in a viscoelastic fluid layer is studied using a linear and a weak nonlinear stability analyses. The onset criterion for stationary, oscillatory and finite amplitude convection is derived analytically. There is a competition between the processes of thermal diffusion, solute diffusion and viscoelasticity that causes the convection to set in through oscillatory mode rather than stationary. The effect of Deborah number, retardation parameter, solutal Rayleigh number, Prandtl number, Lewis number on the stability of the system is investigated. It is shown that the critical frequency increases with Deborah number and solutal Rayleigh number while it decreases with retardation parameter and Lewis number. The nonlinear theory based on the truncated representation of Fourier series method is used to find the heat and mass transfers. The transient behaviour of the Nusselt number and Sherwood number is investigated by solving the finite amplitude equations using Runge-Kutta method. The effect of viscoelastic parameters on heat and mass transfer is brought out.     

Simultaneous determination of fluoxetine and its major active metabolite norfluoxetine in human plasma by LC‐MS/MS using supported liquid extraction

A rapid, sensitive and selective bioanalytical method was developed for the simultaneous determination of fluoxetine and its primary metabolite norfluoxetine in human plasma. Sample preparation was based on supported liquid extraction (SLE) using methyl tert‐butyl ether to extract the analytes from human plasma. Chromatography was performed on a Synergi 4 μ polar‐RP column using a fast gradient. The ionization was optimized using ESI (+) and selectivity was achieved by tandem mass spectrometric analysis using MRM functions, m/z 310 → 44 for fluoxetine, m/z 296 → 134 for norfluoxetine and m/z 315 → 44 for fluoxetine‐d₅ (internal standard). The method is linear over the range of 0.05–20 ng/mL (using a human plasma sample volume of 0.1 mL) with a coefficient determination of greater than 0.999. The method is accurate and precise with intra‐batch and inter‐batch accuracy (%bias) of <±15% and precision (%CV) of <15% for both analytes. A run time of 4 min means a high throughput of samples can be achieved. To our knowledge, this method appears to be the most sensitive one reported so far for the quantitation of fluoxetine and norfluoxetine and can be used for routine therapeutic drug monitoring or pharmacokinetic studies. Copyright © 2011 John Wiley & Sons, Ltd.     

A characterization of finite symplectic polar spaces of odd prime order

A sufficient condition for the representation group for a nonabelian representation (Definition 1.1) of a finite partial linear space to be a finite p-group is given (Theorem 2.9). We characterize finite symplectic polar spaces of rank r at least two and of odd prime order p as the only finite polar spaces of rank at least two and of prime order admitting nonabelian representations. The representation group of such a polar space is an extraspecial p-group of order p1+2r and of exponent p (Theorems 1.5 and 1.6).     

To stay as allene or go further? Synthesis of novel phosphono-heterocycles and polycyclics via propargyl alcohols

The reaction of aryl-substituted propargyl alcohols possessing o-nitro and o-alkylidene groups with (RO)(2)PCl afford novel phosphono(tetrahydro)dibenzazepines, N-hydroxyindolinones or polycyclics (including one with three fused four-membered rings).     

Convective Instability of Oldroyd-B Fluid Saturated Porous Layer Heated from Below using a Thermal Non-equilibrium Model

The linear stability of a viscoelastic fluid saturated densely packed horizontal porous layer heated from below and cooled from above is investigated by considering the Oldroyd-B type fluid. A generalized Darcy model, which takes into account the viscoelastic properties, is employed as momentum equation and a two-field model is used for energy equation each representing solid and fluid phases separately. Linear stability analysis suggests that, there is a competition between the processes of viscous relaxation and thermal diffusion that causes the first convective instability to be oscillatory rather than stationary. Analytical expression for the occurrence of oscillatory onset is obtained, and it is found that the necessary condition for the existence of the same is Λ < 1. Besides, the effect of viscoelastic parameters and the thermal non-equilibrium on the stability of the system is analyzed.     

Some applications of Briot—Bouquet differential subordination

Some applications of Briot—Bouquet differential subordination are obtained which improve or extend a number of classical results in the univalent function theory.