Volatile Foraging Kairomones in the Littoral Zone: Attraction of an Herbivorous Freshwater Gastropod to Algal Odors

Volatile organic compounds (VOCs) produced by algae and cyanobacteria are primarily responsible for odors in fresh waters. Among other functions, VOCs may serve as important infochemicals in biofilms of benthic primary producers. VOCs liberated by benthic, mat-forming cyanobacteria can be used as habitat-finding cues by insects, nematodes, and possibly other organisms. We developed a new gastropod behavioral assay that allows detection of food preference without offering food, thus allowing the distinction between taste, which requires direct contact with the food source, and the detection of odorous infochemicals, which work over distance. We demonstrated that VOCs released from disintegrated cells of a benthic, mat-forming, green alga (Ulothrix fimbriata) are food-finding cues (“foraging kairomones”) that attract the herbivorous freshwater snail Radix ovata. A mixture of three C₅ lipoxygenase compounds and 2(E),4(E)-heptadienal that mimic the major VOCs released by U. fimbriata attracted the snails, whereas neither the mixture of C₅ compounds nor 2(E),4(E)-heptadienal were effective when given alone. This study suggests that VOCs can play a steering role as infochemicals in freshwater benthic habitats, as has been established for many organismic interactions in terrestrial ecosystems.     

Nanoscale properties of polymer fuel cell materials—A selected review

The properties of the components of a membrane electrode assembly in a polymer electrolyte fuel cell (PEFC) determine its efficiency and performance. This paper aims at demonstrating the importance of nanoscale properties of PEFC membranes and electrodes and discussing the information obtained by various experimental techniques. The nanostructure and conductivity of freshly prepared as well as artificially degraded Nafion membranes and Pt/C electrodes are investigated by contact atomic force microscopy (AFM), conductive AFM, pulsed force mode (PFM)‐AFM, in situ scanning tunnelling microscopy (STM), and scanning electron microscopy. The different techniques can provide complementary information on structure and conductivity. With in situ STM on Pt catalyst covered graphite, a layer of very small Pt particles between the catalyst particles is imaged, which is probably not visible with TEM and can explain a systematic discrepancy between TEM and XRD in particle size distribution. Conductive AFM is used to investigate the conductivity of Nafion. The images show a quite inhomogeneous distribution of current at the surface. The percentage of conductive surface increases with humidity, but regions without any current still present up to 80% of relative humidity (RH). Comparison with PFM‐AFM images, where differences in adhesion forces are measured, indicates that hydrophobic regions are present at the surface with comparable dimensions, which are attributed to non‐conductive PTFE‐like polymer backbone. The changes in hydrophilic and hydrophobic parts after artificial degradation by plasma etching in air plasma can be imaged by PFM. High‐resolution current images of the membrane were used to directly compare the measured nanostructure of the single conductive channels with model predictions from the literature. Recent models in the literature propose the formation of water‐filled inverted micelles, with a mean diameter of 2.4 nm, and their agglomeration into clusters agrees well with the current images. Copyright © 2009 John Wiley & Sons, Ltd.     

Designing of Copper Nanoparticle Size Formed via Aerosol Pyrolysis

In this article, the synthesis and structural design of spherical, nonagglomerated particles of copper powder, synthesized by ultrasonic atomization of copper sulfate solutions in hydrogen atmosphere at 1173?K (900?°C), was investigated. Well-controlled particle sizes of Cu powders were obtained from precursor solutions of various concentrations. The mean particle diameters and the ranges of particle size distribution were investigated by scanning electron microscopy (SEM). The diameter values of Cu particles obtained experimentally and estimated theoretically, using the most frequently applied atomization models, were compared. Special attention was paid to our break up capillary waves model, described elsewhere and significantly advanced by Jokanovi???s theoretical approach, which was applied for the first time to a copper metal system as described in this article. The best agreement between the calculated and the experimentally obtained values was found using this model.     

My years with Rutishauser

Vor über 40 Jahren starb am 10. November 1970 viel zu früh der Schweizer Informatik-Pionier Heinz Rutishauser, der an der ETH Zürich forschte und lehrte. F.L. Bauer erinnert sich an seinen Kollegen.     

Influences on signal/noise ratio during ultrasonic inspection of composites

This paper investigates the correlation between transducer properties, defect size and depths, and the signal/noise ratio during ultrasonic inspection of polymeric composites. Samples of different fibre/matrix systems were produced, including artificial defects of various size and shape. These specimens were inspected ultrasonically with transducers in the frequency range from 1 to 150 MHz. It could be seen that the 5 MHz transducer possessed the highest signal/noise ratio in most cases. A transducer selection catalogue incorporating special usage terms for carbon fibre/epoxy resin composites is introduced.     

German developments in guidance systems: an overview daylight

An overview is provided of recent developments in different daylighting systems. The systems range from a simple adaptation of venetian blinds for a better use of daylighting, to specially developed daylight-guiding venetian blinds, mirror louvers, optical mirror elements, ADO-Toplight, holographic optical elements, prismatic systems, Micro-Grates, Plexiglas Daylight, transparent insulation material, moveable glass louvers, a three-layer pipe-grid system and the ‘light sculptor’ in the cupola of the German Parliament. Most of these technologies are available in the market. Others, e.g. the ‘light sculptor’, were designed for a unique application.

Cet article présente les grandes lignes des développements récents en matière de systèmes d'éclairage naturel. Ces systèmes vont de la simple adaptation de stores vénitiens pour un meilleur usage de la lumière naturelle jusqu'à des stores vénitiens de conception spéciale à commande par la lumière du jour, en passant par des rideaux à lattes miroirs, des éléments de miroirs optiques, le système ADO-Toplight, des éléments optiques holographiques, des systèmes prismatiques, des microgrilles, des systèmes d'éclairage naturel en plexiglas, des matériaux isolants transparents, des systèmes à lattes de verre amovibles, un système à grille tubulaire à trois couches et le “sculpteur de lumière” qui équipe la coupole du Parlement allemand. La plupart de ces technologies sont disponibles sur le marché. D'autres, comme le “sculpteur de lumière” ont été conçus pour une application unique.     

On the modeling of flexure hinge mechanisms with finite beam elements of variable cross section

In this paper, a modeling technique for flexure hinge mechanisms is studied. Beam elements of variable cross sections are deployed within a finite element procedure to model a circular flexure hinge. The resulting finite element model has very few degrees of freedom and is accurate in both static and dynamic analysis. Furthermore the modeling approach is applied to an amplifier mechanism. Comparing the results of the proposed model with a 3D finite element reference model, high accuracy for a broad spectrum of hinge parameters is reported while reducing the number of degrees of freedom immensely.     

Galvanic corrosion of polyacrylnitrile (PAN) and pitch based short carbon fibres in polyetheretherketone (PEEK) composites

When an electric current is conducted through a short fibre reinforced polyetheretherketone composite, being in contact with a stainless steel electrode, carbon fibre corrosion occurs. Surface analysis shows that structural defects range from debonding events and fibre cracking in the early stage of the corrosion process to the final disintegration of the fibre. The extent of fibre corrosion is quantified by atomic force microscopy, and the influence of fibre type, fibre volume content and the aqueous medium on the fibre corrosion is reported. Overall, polyacrylnitrile based fibres have a higher corrosion resistance than pitch based ones.