Edge Finishing Effects on the Impact Behavior of Chopped GFRP Composites

The low velocity and low energy impact response of two common sheet mold compound (SMC) material systems—SMC-R27, and SMC-R37—were investigated. In addition to characterizing the low velocity impact response and failure progression of the material systems, the edge effects of diamond saw cutting, waterjet cutting and abrasive waterjet cutting were investigated using optical microscopy and contact surface profilometry. Impact force–time and displacement–time responses were measured and used to characterize energy absorption capabilities and potential correlation to post processing operation and fiber volume fraction. Pre and post-impact edge surface micrographs were examined to relate the failure behavior on the machined surfaces. Experiments and measurements all show that the failure zone size and growth behavior are clearly dependent on the edge finishing process.     

THE VECTORIAL PHOTO-EXCITATION IN SOLAR-TRACKING LEAVES OF Lavatera cretica (MALVACEAE)*,†

Abstract— The diaphototropic responses of the solar-tracking leaves of Lavatera cretica were studied under constant levels of vectorial photo-excitation (negligible variations in angle of incidence and fluence rates). The results showed the following:
(a) The photoreceptors, that are associated with the (major) veins, can equally perceive vectorial excitation (by an oblique light-beam in the plane of symmetry of the vein), directed either towards its tip (tip-oriented: TO), or towards its base (base-oriented: BO).
(b) The mechanism of photo-perception is apparently qualitatively the same for TO and BO excitation.
(c) The response to TO and BO vectorial excitation, which takes place in a circular sheath of motor-cell tissue in the pulvinus (a2–3 mm long segment at the top of the petiole), is also highly directional and results in bending in the vertical plane of the oblique beam. Each sector of the motor tissue can expand longitudinally in response to TO excitation, presumably by influx of solutes, and contract longitudinally in response to BO excitation of the same vein, presumably by efflux of solutes.
(d) The angular velocity of the vectorial response to a constant level of vectorial excitation remains constant over large angular displacements and long periods, and was similar for TO and BO over a wide range of fluence rates (30-400 μmol m⁻²s⁻¹) of white light (400-700 nm).
(e) Reversal of the direction of vectorial excitation (TO to BO, and vice versa) results in reversal of the direction of the vectorial response (laminar reorientation). The change in the direction of laminar reorientation involved a larger overshoot in the original direction when the change was from BO to TO, than in the reverse case.     

Effects of Added Urea and Alkylureas on Gel to Liquid-Crystal Transitions in Doab Vesicles

The gel to liquid-crystal transition for vesicles in aqueous solution formed by dimethyldi-n-octadecylammonium bromide (DOAB) occurs at 44.7°C. Moreover, the shapes of the scans recorded by a sensitive DSC microcalorimeter are very similar when the vesicular solutions are prepared starting with solid DOAB and comparable amounts of either solid urea or solid alkylureas. Therefore, the DOAB vesicles in aqueous solution accommodate this class of solutes without marked changes in the melting temperature and the enthalpy of the transition. The contrast with effects of added surfactants and simple organic solutes such as THF and ethanol is particularly significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

The activity of calcium chloride in aqueous solutions of some amino acids at 25°C

The activity coefficients of calcium chloride in aqueous solutions of the amino acids glycine, β-alanine, γ-amino butyric acid, ε-aminocaproic acid, and glycylglycine have been determined with cells utilizing a calcium ion-exchange electrode. Application of the cross-differential relationship allows a measure of the variation of the salting-in parameter across the series of amino acids. The variation of this parameter is discussed using a semiempirical approach developed earlier.     

A new polarographic response for ethynyloestradiol and its application to electrochemical detection associated with reverse-phase liquid chromatography

Mercury electrodes are oxidized in the presence of ethynyloestradiol, a synthetic steroid. The direct polarographic response obtained is based on the formation of an insoluble mercury compound. In analytical applications of this response, interference from laevonorgestrel, which is found in extracts from combined oral contraceptives, renders the direct determination of ethynyloestradiol impossible. However, reverse-phase liquid chromatography provides separation of the two steroids prior to electrochemical detection of both species at either static or dropping mercury electrodes. Linear response is obtained for 2.5–15.0 μg ml^-1 ethynyloestradiol and 12.5–50 μg ml^-1 laevonorgestrel with 20-μl injections. A microprocessor-based waveform generator is used to optimize the electro-chemical detection. The method is applied to pharmaceutical formulations; the data obtained agree satisfactorily with the nominal contents. Cathodic stripping voltammetry is briefly investigated for very low levels of ethynyloestradiol; the detection limit is around 5 × 10^-9 M on standard solutions.