Book review

NEUTRON RADIOGRAPHY HANDBOOK. Compiled by the Neutron Radiography Working Group under the auspices of the Commission of the European Communities, Joint Research Centre. Edited by P. Van der Hardt and H. Roltger. Price DFL 60.00 (D. Reidel Publishing Co., Dordrecht, Boston, London 1981).     

A method for treating the passage of a charged hard sphere ion as it passes through a sharp dielectric boundary

In the implicit solvent models of electrolytes (such as the primitive model (PM)), the ions are modeled as point charges in the centers of spheres (hard spheres in the case of the PM). The surfaces of the spheres are not polarizable which makes these models appropriate to use in computer simulations of electrolyte systems where these ions do not leave their host dielectrics. The same assumption makes them inappropriate in simulations where these ions cross dielectric boundaries because the interaction energy of the point charge with the polarization charge induced on the dielectric boundary diverges. In this paper, we propose a procedure to treat the passage of such ions through dielectric interfaces with an interpolation method. Inspired by the "bubble ion" model (in which the ion's surface is polarizable), we define a space-dependent effective dielectric coefficient, ε(eff)(r), for the ion that overlaps with the dielectric boundary. Then, we replace the "bubble ion" with a point charge that has an effective charge q/ε(eff)(r) and remove the portion of the dielectric boundary where the ion overlaps with it. We implement the interpolation procedure using the induced charge computation method [D. Boda, D. Gillespie, W. Nonner, D. Henderson, and B. Eisenberg, Phys. Rev. E 69, 046702 (2004)]. We analyze the various energy terms using a spherical ion passing through an infinite flat dielectric boundary as an example.     

The attenuation of Lamb waves in the presence of a fluid

When a plate bearing a Lamb wave is in contact with a fluid the wave is attenuated. This report presents a relatively simple model for calculating attention. The validity of the approach is established by comparison of calculated results and measurements.     

Development of a contactless conductivity detector cell for 1.6 mm O.D. (1/16th inch) HPLC tubing and micro-bore columns with on-column detection

A capacitively coupled contactless conductivity detector cell was designed and constructed suitable for standard HPLC 1.6 mm o.d. (1/16') tubing and columns. Bode plots were acquired in order to determine the optimum input frequency for the new detector cell, with three feedback resistors of increasing resistance (1 MOmega, 3.3 MOmega and 4.7 MOmega) alternately fitted to maximize sensitivity. To evaluate the new detector geometry, a 190 mm x 0.381 mm i.d. (1.59 mm o.d.) column packed with Dionex OmniPac 8.5 microm PAX-100 anion exchange resin was used, with an eluent of 0.5 mM sodium benzoate containing 2% methanol, pumped at 20 microL min(-1), with detection taking place 'on-column'. Standard analytical performance criteria were used to compare the test detector with a commercially available TraceDec C(4)D capillary (360 microm o.d.) detector, with the new detector cell matching the performance of the commercial instrument in terms of linearity, sensitivity and reproducibility. In 'on-column' detection mode, the detector cell could be moved during (or between) chromatographic runs along the length of the packed column bed, to shorten the effective length of the column and thus reduce the retention time of strongly retained sample components, whilst maintaining the resolution of weakly retained components. In addition, the detector could also be applied to the evaluation of the stationary phase packing homogeneity by physically scanning the entire length of the micro-bore column with the moveable detector cell.     

Understanding the role of clay silicate nanoparticles with organic modifiers in thermal curing of cyanate ester resin

The catalytic effect of montmorillonite clay nanoparticles containing organic modifiers such as quaternary phosphonium salts on cure mechanism of cyanate ester resin (RS-9D) was studied by differential scanning calorimetry (DSC) measurements, FT-IR and NMR spectroscopy as well as mass-spectrometry. The results show that the net catalytic effect arises from the presence of moisture associated with nanoclay particles where organic modifiers act as moisture transport agents. Possible mechanisms for cure pathways are discussed.