Interface-mediated oscillatory phenomena

Oscillatory transport processes which occur in the far from equilibrium region have assumed great significance from the viewpoint of science of complexity. Oscillatory phenomena in the chemical reaction systems have been subjected to intense investigations both from theoretical and experimental angles. In the present review an effort has been made to bring transport processes other than conventional chemical reactions into focus: transport processes mediated by solid-liquid and liquid-liquid interfaces have been discussed. Transport through membranes including liquid membranes, liquid-liquid interfaces and the recently reported hydrodynamic oscillator have been covered. Applications of these systems in areas such as fabrication of sensors, phase transfer catalysis and, of course, the obvious biological action, e.g. excitation of biomembranes and tissues, have been reviewed. Theoretical frameworks proposed to rationalize the phenomena have also been critically reviewed.     

Solvent‐free neat synthetic route to tetrahydroacridinones

An environmentally benign approach for the synthesis of acridines using inorganic solid supports and “neat reaction'' technology is described. These methodologies completely eliminate the use of solvent during the course of reaction. Moreover, microwave‐assisted reactions reduce the reaction time from hours to minutes with improved yield. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:138–222, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20080     

Application of complex-lag distributions for estimation of arbitrary order phase derivatives in digital holographic interferometry

This Letter proposes a method to estimate phase derivatives of arbitrary order in digital holographic interferometry. Based on the desired order, the generalized complex-lag distribution is computed from the reconstructed interference field. Subsequently, the phase derivative is estimated by tracing the peak of the distribution. Simulation and experimental results are presented to validate the method's potential.     

An automatic quantitative approach to additive/subtractive moiré

An automatic fringe-analysis procedure is described for additive and subtractive types of moiré. The procedure is based on the simultaneous introduction of differential phase shifts to the two superposed gratings or fringes.     

Experiments on double-diffusion in a composite system comprised of a packed layer of spheres and an underlying fluid layer

In this paper an experimental study is reported on the problem of double-diffusion in a composite system comprised of a liquid-saturated packed layer of spheres and an underlying clear (of solid matrix) fluid layer. The liquid is a mixture of water and ammonium chloride. The initial species concentration of the porous layer is linear and stable and of the clear liquid layer uniform. The system is initially isothermal and it is suddenly cooled from above. The study investigates the evolving temperature and flow fields in the system by utilizing direct temperature measurements as well as holographic interferometry visualization of the density field. The effect of the thermal Rayleigh number, the species Rayleigh number, the thermal conductivity of the beads constituting the porous matrix, and the height of the porous matrix on the evolving temperature and flow fields are determined. Comparisons of the experimental results to the predictions of an existing theoretical model define the limitations of this model and the time domain in which the model performs acceptably well. The findings of this study are relevant to double-diffusion phenomena occuring in the mixed phase and liquid regions of solidifying binary mixtures.     

Magnetoelectric effect in cobalt ferrite-barium titanate composites and their electrical properties

CoFe₂O₄-BaTiO₃ composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric conversion factor has been studied as a function of magnetic field.     

Upward moving ionospheric irregularities over kodaikanal

The occurrence of upward moving kinks first found on ionograms at Thumba (Rastogi, 1970) has been confirmed to occur at another equatorial station, Kodaikanal. These kinks have been found in many records and they occur mostly during local summer months. The occurrence of the kink is shown to be closely associated with horizontal F-region drifts, occurrence of intermediate cusp between F₁ and F₂ layers, bite-out effects of ?₀F₂ and rise of h_PF₂, all being most pronounced around 10 hr. The upward movement of the kink is due to \(\vec E \times \vec B\) drift, while its initiation is probably due to a sudden change in the electrostatic field of the equatorial electrojet. The study of the upward moving kink gives a direct measure of the height variation of the vertical upward drift of ionization over the magnetic equator.