A test rig for scaffold couplers

A multi-purpose test rig is described for making the tests on scaffold couplers which were detailed in an earlier paper “The idealization of scaffold couplers for performance tests and scaffold analysis”[1]. The six basic tests are demonstrated and certain refinements in the rig are described. Some results are given to show repeatability, non-linearity, hysteresis and the effects of coupler tightening and contact conditions. Finally a complete stiffness matrix is given for the initial linear behaviour of a particular coupler.     

Perception of solar UVB radiation by phytophagous insects: behavioral responses and ecosystem implications

Most of our present knowledge about the impacts of solar UVB radiation on terrestrial ecosystems comes from studies with plants. Recently, the effects of UVB on the growth and survival of consumer species have begun to receive attention, but very little is known about UVB impacts on animal behavior. Here we report that manipulations of the flux of solar UVB received by field-grown soybean crops had large and consistent effects on the density of the thrips (Caliothrips phaseoli, Thysanoptera: Thripidae) populations that invaded the canopies, as well as on the amount of leaf damage caused by the insects. Solar UVB strongly reduced thrips herbivory. Thrips not only preferred leaves from plants that were not exposed to solar UVB over leaves from UVB-exposed plants in laboratory and field choice experiments, but they also appeared to directly sense and avoid exposure to solar UVB. Additional choice experiments showed that soybean leaf consumption by the late-season soybean worm Anticarsia gemmatalis (Lepidoptera: Noctuidae) was much less intense in leaves with even slight symptoms of an early thrips attack than in undamaged leaves. These experiments suggest that phytophagous insects can present direct and indirect behavioral responses to solar UVB. The indirect responses are mediated by changes in the plant host that are induced by UVB and, possibly, by other insects whose behavior is affected by UVB.     

The effect of water desorption and organosilane coupling agents on the adhesion of poly(p-xylylene) films to a silicon wafer surface

The adhesion strength of a poly(p-xylylene) (PPX) film to a silicon wafer surface deposited from the vapor was studied using a peel test method. It was found that, within the time and the temperature range studied in this work, the adhesion strength increases with the time and the temperature of the vacuum desiccation of the surface prior to the deposition of the film. This shows that the presence of water adsorbed on the surface strongly decreases the adhesion strength of the film. The effect of organosilane coupling agents on the adhesion of the film to the silicon wafer surface was studied for organosilane derivatives of different chemical compositions. It was found that the adhesion strength can be significantly improved by the presence of 3-(trimethoxysilyl)propyl methacrylate vapor before or during the poly(p-xylylene) deposition. No significant effect on PPX film adhesion was observed for other organosilanes having the propylmethacrylate group replaced by phenyl or alkyl groups. It was found that, in contrast to the other organosilanes, the recrystallization of the PPX from solution did not remove the methacrylate organosilane which remained bonded to the PPX crystals. It is suggested that chemical bonding between the methacrylic group and the PPX chain end radicals is responsible for the improved adhesion of the PPX films.