Stoichiometric dye-binding procedure for the determination of the reactive lysine content of soya bean protein

A new analytical method has been developed for the determination of the reactive lysine content of soya bean protein. The method is based on the reaction of the free basic groups of the protein with 1-phenylazo-2 naphthol-6,8 disulphonic acid. With regard to the stoichiometry of the procedure, it has been proved, contrary to earlier reports, that the basic amino acids, histidine, arginine and lysine, each combine with one mole of the dye. After acylation with propionic anhydride lysine alone loses its dye reactivity. The usefulness of the proposed method has been demonstrated by the determination of the reactive lysine content of several untreated, heat-treated and acid-treated soya bean samples. The results show that heat damage of about 5% in reactive lysine content can be measured in 1·5 h with good reproducibility.     

Morphology of conducting polymeric coatings: quantitative comparison between theory and experiment

The density profile of electrosynthesized polymeric layers on carbon fibers is obtained from gravimetric and scanning electron microscopy (SEM) data. The coating density ρ is found to decrease with increasing radial distance, r, subject to the power law . Based on a modified diffusion-limited aggregation (DLA) model, it is shown that lattice Monte Carlo simulation of the coating process predicts the experimentally observed power law exponent.     

The interaction of alkoxy silane coupling agents with silica surfaces

The interactions of γ-aminopropyltriethoxy silane (A-1100), γ-methacryloxytrimethoxy silane (A-174), γ-glycidoxytrimethoxy silane (A-187), and ethyltriethoxy silane (A-15) with silica surfaces have been studied by means of infrared spectroscopy. The results indicate that the major force holding the silane to the silica surface after application from dilute solutions is primary chemical bonding. These bonds are formed by a condensation reaction between silanols on the hydrolyzed form of the silane and hydroxyl groups on the silica surface. In the case of the amino-silane (A-1100), hydrogen bonding was found to exist but was of minor importance in bonding the silane to the surface. In studying the effects of the addition of water, acetic acid, or n-propylamine to various silane treating solutions, it was found that n-propylamine has a unique catalytic effect on the condensation reaction. This catalytic effect explains the observation that γ-aminopropyltriethoxy silane is more reactive than the other silanes studied. It is felt that silanes not containing an amine group can be made more effective if they are applied in the presence of an amine catalyst.     

Direct patterning of vertically aligned carbon nanotube arrays to 20 μm pitch using focused laser beam micromachining

We present a scalable approach for the fabrication of large-area arrays of carbon nanotube (CNT) structures using focused laser beams in the 0.05–10 W range. We show that CNT films can easily be micromachined into arrays of columns using a wide variety of commercially available pulsed lasers – Excimer, diode-pumped solid-state (DPSS), and CO₂ – operating at wavelengths from 248 nm to 9300 nm. We demonstrate that vertically aligned carbon nanotube (VACNT) arrays with pitches from 20 to 500 μm can be produced with aspect ratios greater than 20:1. Machining speeds up to 425 mm/s were demonstrated and trenches were produced from 10 to 200 μm wide depending on the laser method and beam size. The CO₂ laser had the largest beam diameter of 175 μm and produced the widest columns with the most taper. The remaining lasers, having beam diameters between 10 and 100 μm, produced smaller columns and finer pitch arrays. The VACNT arrays were shown to have high surface quality with no observable residue left behind, demonstrating focused laser micromachining as a readily available soft tooling means for direct manufacturing of VACNT devices. Laser micromachining methods are compared to evaluate the tradeoffs between quality and manufacturing costs.     

A novel technique for the determination of high frequency equibiaxial stress-deformation behavior of viscoelastic elastomers

Synthetic elastomers and elastormeric-like copolymers are now being utilized for a wide spectrum of biomaterial uses including primary structural applications such as pump bladders in artificial hearts and left ventricular assist devices (LVAD), leaflets in prosthetic heart valves, and vascular prostheses. In making fatigue lifetime measurements, as well as for predicting durability, it is essential to know the biaxial stress-deformation behavior at high strain rates (high frequencies) and at extension ratios at least as high as those encountered under performance conditions. This paper describes a technique for determining the high frequency equibiaxial stress-deformation behavior of elastomers. Measurements of material parameters are made at the high strain rates (or frequencies) at which accelerated biaxial flaw growth and fatigue experiments are performed and hence do not require correction for strain-rate dependence of material properties. Furthermore, the plastic deformation (creep) which occurs in the case of viscoelastic membranes is incorporated in the calculations; yielding the “true” values of the extension ratios. Experimental measurements were performed on urethane-based biomaterials using a tuned fluid oscillator which produces cyclic biaxial inflation of the elastomeric membranes clamped around the circumference. Up to moderately large equibiaxial deformations, the form of strain energy function derived from the Gaussian, network theory (or the first approximation to Rivlin's formulation of strain energy function) was found to adequately describe the stress-deformation data. This in turn permits accurate calculation of the tearing energy under biaxial conditions, which is a prime requisite for predicting biaxial fatigue lifetime distributions.     

Prevention of Hydrosilation Cure Inhibition in a Polysiloxane Adhesive by Surface Oxidation

For a variety of reasons epichlorohydrin-ethylene oxide (ECO)-based compounds, in the form of rain erosion boots or sleeves, are bonded to aircraft radomes using a hydrosilation-cured RTV polysiloxane adhesive. Unfortunately, cure of the adhesive can be completely inhibited by unreacted vulcanizing agent and/or ECO cure by-products. We have earlier shown that this inhibition can be prevented by treating the ECO surface with hydrogen peroxide to oxidize the hydrosilation catalyst poisons to a harmless state. In this study we have used spectroscopic techniques to monitor the hydrosilation reaction kinetics and in turn to identify the poison, define the poisoning level and monitor the poison removal by hydrogen peroxide treatment. The degree of poison removal is also correlated with adhesive bond strength using a 180°; peel test. The critical poison in the system was excess ECO vulcanizing agent which can be completely removed from the surface using a 30 vol. % H₂O₂ treatment for 30 minutes as long as the initial vulcanizing agent concentration is 1 p.p.h. or less.     

Nachweis von Fettabakterin (p-Chlorbenzoes?ure) im Schafk?se

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