Compressibility effects in laminar free convection from a vertical cone

In this paper an analysis of the laminar compressible natural convection about a vertical cone is presented. The governing boundary layer equations are suitably transformed and studied in terms of a compressibility variable expansion. The numerical solutions for the first three terms have been obtained for the ratio of specific heats=1.4, and a Prandtl number Pr=0.72, as characteristics of a diatomic gas, and for a range of values of the wall-ambient temperature difference ofA=0.2 to 1000. The numerical results obtained allow an evaluation of the skin friction and heat transfer at the surface of the cone. It is found that the effect of the compressibility is to increase the heat transfer rate at the wall for small values of the wall-ambient temperature difference parameter and to decrease it for large values of this parameter. The skin friction, however, is always reduced.     

Similarity solutions in free convection boundary-layer flows adjacent to vertical permeable surfaces in porous media: II prescribed surface heat flux

The equation which governs the similarity solution for free convection boundary-layer flow along a vertical permeable surface with prescribed surface heating and mass transfer rate is discussed. The solution is seen to depend on two non-dimensional parameters;m, the power-law exponent, and γ, the mass transfer parameter. It is shown that solutions exist for allm>?1 for γ>0 (fluid injection) whereas for γ<0 (fluid withdrawal), solution exist form>m ₀(γ), wherem ₀ is determined as a function of γ. Solutions for large mass transfer rates are obtained, for both γ>0 and γ<0. For γ>0 the form of the asymptotic solution for γ large is seen to depend on the value ofm. Solutions form large are derived, these are seen to be different depending on whether γ is positive or negative.     

Improved Oxidation of Naringenin to Carthamidin and Isocarthamidin by Rhodotorula marina

A novel single-step microbial transformation process for the efficient production of carthamidin and isocarthamidin from naringenin by yeast Rhodotorula marina in an aerated bioreactor was described. The biotransformation led to the total product concentration of 233 mg/l. The highest conversion efficiency observed for carthamidin was 0.31 mg/mg of naringenin and for isocarthamidin 0.47 mg/mg of naringenin.     

Hydrogen: a good partner for rhodium‐catalyzed hydrosilylation

The influence of hydrogen pressure on the hydrosilylation of ketones catalyzed by [((S)‐SYNPHOS)Rh(nbd)]OTf has been studied. We have notably demonstrated that hydrogen significantly affected the outcome of the reaction while not being consumed as stoichiometric reducing agent. In THF, diethyl ether or toluene, the hydrogen pressure exceedingly accelerated the hydrosilylation reaction and preserved or even improved the enantioselectivity of the process. In CH₂Cl₂, the rhodium catalyst also showed generally higher catalytic activity under hydrogen pressure. Most serendipitously, several ketones were found to give products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under hydrogen pressure. Copyright © 2014 John Wiley & Sons, Ltd.     

Unsteady flow and heat transfer past an axisymmetric permeable shrinking sheet with radiation effect

In this paper, the problem of unsteady axisymmetric boundary layer flow and heat transfer induced by a permeable shrinking sheet in the presence of radiation effect is studied. The transformed boundary layer equations are solved numerically by an implicit finite‐difference scheme known as the Keller‐box method. The influence of radiation, unsteadiness and mass suction parameters on the reduced skin friction coefficient f′′(0) and the heat transfer coefficient ?θ′(0), as well as the velocity and temperature profiles are presented and discussed in detail. It is found that dual solutions exist and suction parameter delays the separation of boundary layer. Copyright © 2010 John Wiley & Sons, Ltd.     

Dual solutions in mixed convection boundary-layer flow with suction or injection

The effect of suction/injection on the laminar mixed convectionboundary-layer flow about a vertical wall in an incompressibleviscous fluid is considered. The similarity solutions are obtainedfor some values of the suction/injection parameter as well asthe mixed convection parameter for three particular cases: uniformtemperature, uniform heat flux and stagnation flow. The resultingsystem of non-linear ordinary differential equations is solvednumerically for both assisting and opposing flow regimes usinga finite-difference scheme known as the Keller box method. Numericalresults are obtained for the skin friction coefficient and localNusselt number as well as velocity and temperature profiles.The effects of the involved parameters on the skin frictioncoefficient and the local Nusselt number characteristics arediscussed. It is found that dual solutions exist for assistingflow, besides that usually reported in the literature for opposingflow.     

On the homogenization of the Buckley-Leverett equation including trapping effects at the micro scale

We consider a simplified, one dimensional model for two-phase (oil/water) flow in a porous medium. The medium consist of alternating homogeneous blocks separated by interfaces, where trapping effects may occur. Two effective models are derived in [2] and [7]. In this paper we show that the two models are equivalent. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic susceptibilities and knight shifts of the intermetallic compounds NdCu4 and NdCu5

The magnetic susceptibility and Knight shift of the intermetallic compounds NdCu₄ and NdCu₅ were investigated over the temperature range 80–850 K. The most important contributions to the magnetic susceptibility are the Curie-Weiss term, expressing the paramagnetism of the localized 4?-electrons, and a temperature independent term, both of which have been determined. The phenomenological quantity J_s? between the 4?-electron and conduction electron spins was found to be ?2.46.10^?3eV for NdCu₄ and 1.35.10^?3 eV for NdCu₅. A reversal in the sign of the s-? coupling for CeCu₅ was noted.