Rapid TLC Method for Estimation of Mevalonic Acid in the Leaves of Medicinal Plants

A simple, rapid, specific and sensitive thin layer chromatographic (TLC) method has been developed for the quantitative estimation of mevalonic acid (MVA) in leaves of medicinal plants; Artemisia annua, Psorelia corylifolia, Vinca rosea, Withania somnifera and Barleria proinites. The assay procedure involved conversion of MVA to its lactone, mevalonolactone (MVAL). Mevalonic acid was extracted from the leaf tissues of plants. Separation of MVAL was carried out on silica gel 60 F₂₅₄ TLC plates using benzene:acetone (3:2) as the mobile phase. The densitometric determination of MVAL was performed at 600 nm after derivatization with anisaldehyde reagent in absorption–reflectance mode. The method was validated over the linearity range of 100–500 ng spot^?1 and correlation coefficient for the calibration curve was >0.99. The average recovery of MVAL, used as internal standard, was higher than 98%. The lower limit of detection was found to be 50 ng spot^?1.     

Microscale Demonstration of Charge Modification upon Complexation by Ion Exchange

A small plastic syringe (or a Pasteur pipet) is used as an ion-exchange microcolumn model to demonstrate the principles of ion exchange and charge modification upon complexation. In the first part of the experiment, the removal of cobalt ions (cations) from aqueous solution is visually demonstrated. Then, Co²⁺ is reacted with the negatively charged EDTA (ethylenediaminetetraacetate) ion to form a complex anion. When passed through a cation exchange column, the Co²⁺ ions are completely retained whereas the complexed cobalt ions are not removed at all. This experiment is appropriate for a first-year chemistry laboratory, and takes approximately one hour to complete.     

Determination of the Mechanical Properties of Powdered Agricultural Products and Sugar

Grain, forage cereals and different types of flour are commonly stored in silos. Their behavior within these structures is mainly governed by their mechanical properties. Since their advent, numerical methods have increasingly been used in silo design. However, the results obtained using these methods strongly depend on the variables employed to define the materials stored. Since the literature provides little information on the variables required for modeling the behavior of agricultural powdered materials, the goals of the present work were to: i) provide values for the different variables that are needed when designing silos using numerical methods (e.g., the Poisson ratio, the dilatancy angle and the modulus of elasticity, etc.), and ii) investigate the suitability of tests used in soil mechanics for powdered materials (e.g., the direct shear and the oedometric and triaxial test). Recommended values for these variables are proposed.     

Two-phase MFD flows in orthogonal curvilinear coordinate system

Steady flow of an inviscid, incompressible two-phase magnetofluid with infinite electrical conductivity is treated. With one ignorable coordinate in a general orthogonal curvilinear system, general solutions of the equations, considering number densityN constant throughout the motion, are obtained.     

A hybrid optical-digital processor for image deblurring

A hybrid optical-digital image processing system is developed for deblurring out-of-focus pictures. The optical part is a dual-channel non-coherent processor which implements the Wiener filter for deblurring through appropriate pupil functions. The methods of implementing the bipolar PSF in a non-coherent processor are described, as are the methods of determining the pupil functions from the given PSFs. The digital part of the processor subtracts or demodulates the outputs from the dual-channel optical processor to give the final deblurred picture. The pupil functions are experimentally realized and the deblurred outputs are presented.     

Dynamical ordering induced by preferential transitions in planar arrays of superheated superconducting granules

We perform simulations of planar arrays of superheated superconducting granules (PASS) under an external magnetic field, analyzing transitions undergone by the system when the external field is slowly increased from zero. We observe, for high concentrations, the existence of an interval of external fields for which no transitions are induced. This effect is analogous to a ‘hot border zone’ identified in the response of superheated superconducting granule detectors. We explain such behaviour as produced by a geometrical ordering dynamically induced in the system by transitions in preferential sites due to diamagnetic interactions.