Deformation of a droplet in an electric field: nonlinear transient response in perfect and leaky dielectric media

Deformation of a fluid drop, suspended in a second immiscible fluid, under the influence of an imposed electric field is a widely studied phenomenon. In this paper, the system is analyzed numerically to assess its dynamic behavior. The response of the system to a step change in the electric field is simulated for both perfect and leaky dielectric systems, exploring the influence of the fluid, interfacial, and electrical properties on the system dynamics. For the leaky dielectric case, the dynamic build up of the free charge at the interface, including the effects of convection along the interface due to electrohydrodynamic circulation, is investigated. The departure of the system from linear perturbation theory is explained using these dynamic simulations. The present simulations are compared with analytic solutions, as well as available experimental results, indicating that the predictions from the model are reliable even at considerably large deformations.     

Tunable filtration media employing alternating current electrokinetics

Separation of colloidal particles from aqueous media by barrier filtration is typically dictated by sieving mechanisms. Here, we demonstrate that colloid filtration by porous membranes can be considerably augmented by suitably superimposing an alternating current (AC) electric field on the membrane. The combined steric-dielectrophoretic filtration can result in very high rejection of the particles compared to solely steric rejection.     

Helicity induction through hydrogen bonding and spontaneous resolution of a bimetallic nickel complex coordinated to an octahedral metalloligand

A new bimetallic complex of nickel(II) coordinated to a molybdenum-containing metalloligand has been synthesized that forms a helical chain through hydrogen bonding and shows spontaneous resolution upon crystallization.     

In Vitro Renaturation of Alkaline Family G/11 Xylanase via a Folding Intermediate: α-Crystallin Facilitates Refolding in an ATP-Independent Manner

In this study, alkaliphilic family G/11 xylanase from alkali-tolerant filamentous fungi Penicillium citrinum MTCC 6489 was used as a model system to gain insight into the molecular aspects of unfolding/refolding of alkaliphilic glycosyl hydrolase protein family. The intrinsic protein fluorescence suggested a putative intermediate state of protein in presence of 2 M guanidium hydrochloride (GdmCl) with an emission maximum of 353 nm. Here we studied the refolding of GdmCl-denatured alkaline xylanase in the presence and the absence of a multimeric chaperone protein α-crystallin to elucidate the molecular mechanism of intramolecular interactions of the alkaliphilic xylanase protein that dictates its extremophilic character. Our results, based on intrinsic tryptophan fluorescence and hydrophobic fluorophore 8-anilino-1- naphthalene sulfonate-binding studies, suggest that α-crystallin formed a complex with a putative molten globule-like intermediate in the refolding pathway of xylanase in an ATP-independent manner. A 2 M GdmCl is sufficient to denature alkaline xylanase completely. The hydrodynamic radius (R_H) of a native alkaline xylanase is 4.0, which becomes 5.0 in the presence of 2 M GdmCl whereas in presence of the higher concentration of GdmCl R_H value was shifted to 100, indicating the aggregation of denatured xylanase. The α-crystallin·xylanase complex exhibited the recovery of functional activity with the extent of ~43%. Addition of ATP to the complex did not show any significant effect on activity recovery of the denatured protein.     

Rigid extensions of algebraic frames

An extension G ≤ H of lattice-ordered groups is said to be a rigid extension if for each ${h \in H}An extension G ≤ H of lattice-ordered groups is said to be a rigid extension if for each h ? H{h \in H} there exists a g ? G{g \in G} such that h ^⊥⊥ = g ^⊥⊥. In this paper, we will define rigid extensions and some other generalizations in the context of algebraic frames satisfying the FIP. One of the main results is a characterization of rigid extensions using d-elements of the frame. We also show that a rigid extension between two algebraic frames satisfying the FIP will induce a homeomorphism between their corresponding minimal prime spaces with respect to both the hull-kernel topology and the inverse topology. Moreover, basic open sets map to basic open sets.     

Mean magnetic field and noise cross-correlation in magnetohydrodynamic turbulence: results from a one-dimensional model

We show that a recently proposed [J. Fleischer, P.H. Diamond, Phys. Rev. E 58, R2709 (1998)] one-dimensional Burgers-like model for magnetohydrodynamics (MHD) is in effect identical to existing models for drifting lines and sedimenting lattices. We use the model to demonstrate, contrary to claims in the literature, that the energy spectrum of MHD turbulence should be independent of mean magnetic field and that cross-correlations between the noise sources for the velocity and magnetic fields cannot change the structure of the equations under renormalisation. We comment on the scaling and the multiscaling properties of the stochastically forced version of the model. Received 29 October 1998 and Received in final form 8 December 1998     

Recent Advances On Direct Formylation Reactions

Aldehydes serve as the key functional group in organic synthesis and are valuable intermediates. The various advanced methods of direct formylation reactions have been reviewed in this article. Overcoming the drawbacks of the traditional methods of formylation, newer methods involving homo and heterogenous catalysts, one pot reactions, solvent free techniques are elaborated, which can be performed under mild conditions and using inexpensive resources.