Templated cocrystallization of cholesterol and phytosterols from microemulsions

A major cause of cardiovascular disease is high cholesterol (CH) levels in the blood, a potential solution to which is the intake of phytosterols (PS) known as CH-reducing agents. One mechanism proposed for PS activity is the mutual cocrystallization of CH and PS from dietary mixed micelles (DMM), a process that removes excess CH from the transporting micelles. In this study, microemulsions (MEs) were used both as a model system for cocrystallization mimicking DMM and as a possible alternative pathway, based on the competitive solubilization of CH and PS, to reduce solubilized CH transport levels from the ME. The effects of different CH/PS ratios, aqueous dilution, and lecithin-based MEs on sterol crystallization were studied. The precipitated crystals from the ME-loaded system with PS alone and from that loaded with 1:1 or 1:3 CH/PS mixtures were significantly influenced by ME microstructure and by dilution with aqueous phase (X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) results). No new polymorphic structures were detected apart from the corresponding sterol hydrates. Mixed crystal morphology and the habit of the precipitated sterols were strongly affected by the CH/PS ratio and the structures of the diluted ME. As the amount of PS in the mixture increased or as the ME aqueous dilution proceeded, precipitated crystal shape became more needle-like. The mixed sterols seemed to be forming eutectic solids.     

Selective 17‐β‐estradiol molecular imprinting

An efficient novel method for the synthesis of a covalent molecularly imprinted polymer (MIP) highly specific to β‐estradiol have been developed. MIP prepared by both covalent and non covalent techniques, demonstrated high selectivity toward β‐estradiol. MIPs were synthesized by radical polymerization of 17‐β‐estradiol 4‐vinyl‐benzene carboxyl or sulfonyl esters used as covalent functional monomers, methacrylic acid as noncovalent functional monomer, ethylene glycol dimethacrylate as crosslinking agent, and acetonitrile as swelling and porogenic component. Almost 35% (w/w) of 17‐β‐estradiol was successfully removed from the polymer network by basic hydrolysis. The binding ability of MIP was 10.73 μg/mg MIP following removal of 17‐β‐estradiol in the 2 mg/mL β‐estradiol solution. Selective rebinding of β‐estradiol toward MIP was tested in the presence of competitive binders including estrone, 19‐nortestosterone, epiandrosterone, and cholesterol. Estrone having closest similar chemical structure to β‐estradiol exhibited only 0.6 μg/mg MIP competitive binding, being exposed to equivalent concentrations. Moreover, other competitive steroids demonstrated negligible affinity toward MIP indicating high selectivity of novel MIP system toward β‐estradiol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5534–5542, 2009     

The Separation of Platinum Group Metals (PGM) in Chloride Media by Isothiouronium Resins

Styrene-divinylbenzene copolymers incorporating isothiourea functional groups show a remarkable affinity for platinum-group-metal (PGM) ions in chloride media, The mode of ion binding to the resin depends on the equilibria between isothiourea (free base) form and isothiouronium (conjugated acid) form, This in return is related to matrix structure, A. resin, Monivex, which shows high binding capacities for PGM ions in high acidities (2–6M HC1) is described. Equilibrium, rate and selectivity data, as well as process application data is presented and discussed, Electron microprobe studies are used to follow chemical changes in resin beads and ion regeneration patterns.     

Reflections on the status and nature of visual reasoning - the case of the matches

This paper gives an interpretation of the transformation formulae (in matrix notation) for rotations in the plane in terms of the exponential function. Then the fact that the addition of two rotations corresponds to the multiplication of the corresponding matrices is given a simple interpretation.     

Ueber einige,bei Schwingungsproblemen auftretende,Differentialgleichungen

Ohne Zusammenfassung     

The application of optical coherence tomography to problems in polymer matrix composites

The Composites Group at the National Institute of Standards and Technology has found optical coherence tomography (OCT) to be a powerful tool for non-destructive characterization of polymer matrix composites. Composites often exhibit superior properties to traditional materials such as wood and metal. However, the barrier to their widespread infiltration into consumer markets is cost. Composites can be made more cost competitive by improved composite design, process optimization, and quality control. OCT provides a means of evaluating the three aforementioned areas. OCT is a very versatile technique that can be applied to a variety of problems in polymer composites such as: microstructure determination for permeability and mechanical property prediction, void, dry spot, and defect detection, and damage evaluation. Briefly, OCT uses a low coherence source such as a superluminescent diode laser with a fiber optic based Michelson interferometer. In this configuration, the composite is the fixed arm of the interferometer. Reflections from heterogeneities within the sample are mapped as a function of thickness for any one position. Volume information is generated by translating the sample on a motorized stage. Information about the location and size of a feature within the composite is obtained. In this work, the power of OCT for imaging composite microstructure and damage is presented. An example of permeability prediction using the composite microstructure imaged from OCT is demonstrated. The effect of image processing on the value of permeability is discussed. Using the same sample, OCT imaging of composite impact damage is compared to more traditional techniques, X-ray computed tomography and confocal microscopy.