Effect of Prandtl Number on Linear Stability of Mixed Convective Flow in a Vertical Porous Annulus: A LTNE Approach

A comprehensive numerical study on linear stability of fully developed mixed convective flow in a vertical annulus filled with saturated porous medium is investigated. A local thermal non-equilibrium (LTNE) approach is considered. The flow is induced by external pressure gradient and buoyancy force. The non-Darcy Brinkman-Forchheimer extended model is considered. The governing equations are solved by spectral collocation method. Special attention is given to understand the effect of thermal non-equilibrium parameters: inter phase heat transfer coefficient (H) and porosity scaled thermal conductivity ratio (?) on instability boundary of basic flow in (Pr, Ra) -plane. Stability results indicate that for high permeable porous media depending on Prandtl number, the flow is least stable under either first azimuthal mode or zero azimuthal modes. The stability criteria of basic flow decreases on increasing the Prandtl number. Increasing of H stabilizes the basic flow, whereas, increasing of ? destabilizes it. Keywords: Porous media, mixed convection, linear stability, thermal non-equilibrium, non-Darcy model

Optimal Solution of a Fully Fuzzy Linear Fractional Programming Problem by Using Graded Mean Integration Representation Method

In the present paper, the study of fully fuzzy linear fractional programming problem (FFLFPP) using graded mean integration representation method is discussed where all the parameters and variables are characterized by trapezoidal fuzzy numbers. A computational algorithm has been presented to obtain an optimal solution by applying simplex method. To demonstrate the applicability of the proposed approach, one numerical example is solved. Also to check the efficiency and feasibility of the proposed approach, we compare the results of examples by applying crisp numbers, triangular fuzzy numbers and trapezoidal fuzzy numbers

Spatiotemporal rheochaos in nematic hydrodynamics

Motivated by the observation of rheochaos in sheared wormlike micelles [Bandyopadhyay et al., Phys. Rev. Lett, 84 2022, (2000); Europhys. Lett. 56, 447 (2001); Pramana 53, 223 (1999)] we study the coupled nonlinear partial differential equations for the hydrodynamic velocity and order parameter fields in a sheared nematogenic fluid. In a suitable parameter range, we find irregular, dynamic shear-banding and establish by decisive numerical tests that the chaos we observe in the model is spatiotemporal in nature.Comment: Slight changes in text, references and Fig. 5 inset; 6 eps figures (figs 2,3,4 at lower resolution to reduce file size; full files available on request); accepted for publication in Phys Rev Let

Magnetic field generation in Higgs inflation model

We study the generation of magnetic field in Higgs-inflation models where the Standard Model Higgs boson has a large coupling to the Ricci scalar. We couple the Higgs field to the Electromagnetic fields via a non- renormalizable dimension six operator suppressed by the Planck scale in the Jordan frame. We show that during Higgs inflation magnetic fields with present value $10^{-6}$ Gauss and comoving coherence length of $100 kpc$ can be generated in the Einstein frame. The problem of large back-reaction which is generic in the usual inflation models of magneto-genesis is avoided as the back-reaction is suppressed by the large Higgs-curvature coupling.Comment: 10 pages, RevTeX

Media optimization for biosurfactant production by Rhodococcus erythropolis MTCC 2794: artificial intelligence versus a statistical approach

This paper entails a comprehensive study on production of a biosurfactant from Rhodococcus erythropolis MTCC 2794. Two optimization techniques-(1) artificial neural network (ANN) coupled with genetic algorithm (GA) and (2) response surface methodology (RSM)-were used for media optimization in order to enhance the biosurfactant yield by Rhodococcus erythropolis MTCC 2794. ANN and RSM models were developed, incorporating the quantity of four medium components (sucrose, yeast extract, meat peptone, and toluene) as independent input variables and biosurfactant yield [calculated in terms of percent emulsification index (% EI24)] as output variable. ANN-GA and RSM were compared for their predictive and generalization ability using a separate data set of 16 experiments, for which the average quadratic errors were ~3 and ~6%, respectively. ANN-GA was found to be more accurate and consistent in predicting optimized conditions and maximum yield than RSM. For the ANN-GA model, the values of correlation coefficient and average quadratic error were ~0.99 and ~3%, respectively. It was also shown that ANN-based models could be used accurately for sensitivity analysis. ANN-GA-optimized media gave about a 3.5-fold enhancement in biosurfactant yield

Development of SSR markers and construction of a linkage map in jute

Jute is an important natural fibre crop, which is only second to cotton in its importance at the global level. It is mostly grown in Indian subcontinent and has been recently used for the development of genomics resources. We recently initiated a programme to develop simple sequence repeat markers and reported a set of 2469 SSR that were developed using four SSR-enriched libraries (Mir et al. 2009). In this communication, we report an additional set of 607 novel SSR in 393 SSR containing sequences. However, primers could be designed for only 417 potentially useful SSR. Polymorphism survey was carried out for 374 primer pairs using two parental genotypes (JRO 524 and PPO4) of a mapping population developed for fibre fineness; only 66 SSR were polymorphic. Owing to a low level of polymorphism between the parental genotypes and a high degree of segregation distortion in recombinant inbred lines, genotypic data of only 53 polymorphic SSR on the mapping population consisting of 120 RIL could be used for the construction of a linkage map; 36 SSR loci were mapped on six linkage groups that covered a total genetic distance of 784.3 cM. Hopefully, this map will be enriched with more SSR loci in future and will prove useful for identification of quantitative trait loci/genes for molecular breeding involving improvement of fibre fineness and other related traits in jute

Buckling and force propagation along intracellular microtubules

Motivated by recent experiments showing the compressive buckling of microtubules in cells, we study theoretically the mechanical response of and force propagation along elastic filaments embedded in a non-linear elastic medium. We find that embedded microtubules buckle when their compressive load exceeds a critical value

Nanocrystals of metals, semiconductors and oxides: novel synthesis and applications

Films of nanocrystals such as Au, Ag and Pd, semiconducting sulphides such as CdS, ZnS and CoS, and oxides such as Fe2O3 and CuO have been prepared by employing reactions at liquid-liquid (organic-aqueous) interfaces. In this method, a suitable organic derivative of the metal taken in the organic layer reacts at the interface with the appropriate reagent present in the organic layer. Two typical applications of nanocrystals pertaining to magnetic devices and dip-pen lithography are briefly presented