Intriguing Advantages Research Articles

Molecular imprinting technology: challenges and prospects for the future

Molecular imprinting is a technique for the fabrication of biomimetic polymeric recognition sites or “plastic antibodies/receptors” which is attracting rapidly increasing interest. By this technology, recognition matrices can be prepared which possess high substrate selectivity and specificity. In the development of this technology, several applications have been foreseen in which imprinted materials may be exchanged for natural recognition elements. Thus, molecularly imprinted polymers have been used as antibody/receptor binding mimics in immunoassay-type analyses, as enzyme mimics in catalytic applications and as recognition matrices in biosensors. The best developed application area for imprinted materials, though, has been as stationary phases for chromatography, in general, and chiral chromatography, in particular. This review seeks to highlight some of the more intriguing advantages of the technique as well as pointing out some of the difficulties encountered. The prospects for future development will also be considered. Chirality 10:195–209, 1998. © 1998 Wiley-Liss, Inc.

Apparent absorptance for diffusely and specularly reflecting spherical cavities

The apparent absorptance of a cavity α cavity, is defined as the fraction of energy flux emitted by a black-body surface stretched across the cavity opening that is absorbed by the cavity walls. Because of multiple reflections among the cavity walls, α cavity will exceed the surface absorptance, α . Such an effect, called the cavity effect, is employed in the design of receiver/reactors for solar furnaces to capture the solar radiation. The cavity effect for partial enclosures has been analyzed for specific configurations, among them: cylindrical, conical, spherical, rectangular-groove and V-groove cavities. These problems have been solved for specularly and diffusely reflecting cavity walls. Little information is presently available which describes the particular case of specularly reflecting spherical cavities with a circular opening. Such cavities offer several intriguing advantages over the conventional heavily insulated enclosures made of ceramic materials when applied for solar furnace receivers at moderate to high (2000 K and above) temperatures. Specular spherical geometries have also significant importance in modelling radiant heat transport through the void spaces across a porous material, and the apparent surface emittance was analytically derived for a differential element of a sphere. In the present study, the apparent absorptance of a spherical cavity with a circular opening is calculated for cavity walls having both specular and diffuse reflectance components.

Growth of Single Crystals of Silver Halides in Silica Gels at Near Ambient Temperatures

THE growth of single crystals by controlled diffusion in gels at near ambient temperatures offers intriguing advantages for substances which are sparingly soluble in the gel medium or which dissociate at the high temperatures so frequently employed for crystal growth1, or both. The gel diffusion growth method has been described as most applicable to materials with solubilities in aqueous solutions in the order of 10−1 to 10−2 weight per cent at ambient temperatures2. We report the successful application of the gel growth method to substances, the solubilities of which range from 10−5 to 10−7 weight per cent, thus enhancing its use for preparing single crystals of quite low solubility substances.