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We investigated the effects of carboxylic acids on the oviposition behavior of the spruce budworm, a major defoliator of coniferous forests in North America. Carboxylic acids have been implicated as semiochemicals involved in lepidopteran host finding and oviposition, and they occur as free acids in the epicuticular wax of host (Picea and Abies spp.) foliage where spruce budworm lay eggs. In a dual-choice laboratory bioassay, several straight chain and cyclic monocarboxylic acids, and two dicarboxylic acids, significantly enhanced oviposition. Peak activity was associated with saturated acids having 8-12 carbons.Unsaturated oleic and linoleic acids were also preferred. The lowesteffective dosage occurred at 7.8 nmol/ cm2 (1 mM solution). At higher dosages (=/>780 nmol /cm2), C9-C10 acids became strongly deterrent and some shorter-chain and longer-chain acids became stimulating. Electroantennogram responsesto C6-C16 acids indicated that behaviorally active acids are detected by olfaction. The most active acids (C8-C12 and oleic) have not been reported in the free fatty acid fraction of host cuticular waxes. However, long-chain C14-C28 acids are present as free acids, but they elicited significant oviposition responses only at doses that exceeded their levels in foliage waxes. Spruce budworm preference for carboxylic acids may represent a nonspecific response common to Lepidoptera, which may have evolved because of the ubiquitous occurrence of carboxylic acids in plants. [ABSTRACT FROM AUTHOR]

Although alkaloids are known feeding deterrents for lepidopteran larvae, including the spruce budworm, Choristoneura fumiferana (Clemens), few studies have investigated their effects on lepidopteran oviposition. Quinolizidine-containing alkaloid extracts and isolated quinolizidine alkaloids were obtained from 2 Chinese plants, Sophora alopecuroides L. and 16rmopsis lanceolata Robert Brown, to evaluate their effects on spruce budworm oviposition. Application of extracts from either plant on Parafilm substrate significantly deterred oviposition atdosages as low as 4.7 and 7.9 mug/cm2, respectively, in dual-choice bioassays. Of 9 quinolizidine alkaloids produced by these plants, 6 deterred oviposition on Parafilm substrate treated at 7.9 mug/cm or less. The most effective compounds were aloperine (0.3 mug/cm2 = 1.3 nmol/cm2), sparteine (1.6 mug/cm2 = 6.8 nmol/cm2), and cytisine (1.6 mug/cm2 = 8.4 nmol/cm2). Oviposition was deterred also on freshhost foliage, 8-cm twigs of balsam fir, Abies balsamea (L.) Miller, which had been sprayed with either a 1-ml aliquot of alkaloid extract(10 mg/ml) of S. alopecuroides or 1 ml of an aloperine solution (1 mg/ml). There was no effect on longevity of males or females continuously exposed to artificial substrate treated with aloperine or alkaloid extract from S. alopecuroides in no-choice bioassays, nor was the ability of males to inseminate females affected. However, female production of egg masses was inhibited, although clutch size (eggs per eggmass) was not affected. These results are the 1 st demonstration of the behaviorally deterring and physiologically inhibiting effects of quinolizidine alkaloids on lepidopteran oviposition. [ABSTRACT FROM AUTHOR]

Abstract: Addition of surfactants to aqueous solutions of polyelectrolytes carrying an opposite charge causes the spontaneous formation of complexes in the bulk phase in certain concentration ranges. Under some conditions, compact monodisperse multichain complexes are obtained in the bulk. The size of these complexes depends on the mixing procedure and it can be varied in a controlled way from nanometers up to micrometers. The complexes exhibit microstructures analoguous to those of the precipitates formed at higher concentrations. In other cases, however, the bulk complexes are large, soft and polydisperse. In most cases, the dispersions are only kinetically stable and exhibit pronounced non-equilibrium features. Association at air-water interfaces readily occurs, even at very small concentrations. When the surfactant concentration is small, the surface complexes are usually made of a surfactant monolayer to which the polymer binds and adsorbs in a flat-like configuration. However, under some conditions, thicker layers can be found, with bulk complexes sticking to the surface. The association at solid-water interfaces is more complex and depends on the specific interactions between surfactants, polymers and the surface. However, the behaviour can be understood if distinctions between hydrophilic surfaces and hydrophobic surfaces are made. Note that the behaviour at air-water interfaces is closer to that of hydrophobic than that of hydrophilic solid surfaces. The relation between bulk and surface complexation will be discussed in this review. The emphasis will be given to the results obtained by the teams of the EC-funded Marie Curie RTN “SOCON”. [Copyright &y& Elsevier]

Abstract: We have studied bubble motion within a column of foam allowed to undergo free drainage. We have measured bubble motion upward with time and as a function of their initial positions. Depending on the gas used, which sets the coarsening and drainage rates, different bubble upward motion types have been identified (constant speed, acceleration or deceleration) and explained in relation with liquid downward flows. The proofs of the consistency between bubble upward motion and liquid downward flow are obtained both by comparing the bubble motion curves to the liquid drainage ones, and by comparing the time variations of the liquid fraction extracted from bubble motion to direct liquid fraction measurements by electrical conductimetry. The agreement between bubble position tracking and electrical conductivity shows in particular that it is possible to determine the drainage regime from such simple bubble motion measurements. This work also allowed us to demonstrate a special case of foam coarsening and expansion, occurring when the foam gas is less soluble than the outside one, caused by diffusion of this external gas into the foam. All these results allow us to build a picture of drainage and coarsening seen from the bubble point of view. [Copyright &y& Elsevier]

Abstract: We report results on the dependence of foam rheology on the nature of its components (gas, liquid and surfactant). We have varied the liquid bulk properties, the gas–liquid interfacial properties, which implies also different thin liquid films properties, and the gas. Microscopic characterizations are also performed to find correlations between the different length scales, and to interpret the macroscopic rheological behavior (oscillations and creep). We have found that the elastic modulus G′, once normalized by the Laplace pressure, does not depend on the foam components, whereas the loss modulus G″ shows some dependence with the interfacial properties. We show that the gas is an important factor for these moduli because of its role in the foam aging, via coarsening. We have also evidenced a dilatancy effect taking place under continuous shear, by using a special foam sample shape, in which only a foam band is subjected to shear. We have observed and measured an increase of the liquid volume fraction ɛ in that band. [Copyright &y& Elsevier]

When asphaltenes adsorb at liquid interfaces, after the rapid initial diffusion step toward the interface, a long reorganization and a progressive building of multilayers occur. The reorganization is faster at oil–water interfaces than at air–oil interfaces, but the multilayer formation takes similar times. In the case of oil–water interfaces, the time scales are similar for different oils, but the variation with asphaltene concentration is qualitatively different: adsorption becomes faster with increasing concentrations for oils that are good asphaltene solvents and slower in the case of poor solvents. The presence of surfactant changes significantly the adsorption process. [Copyright &y& Elsevier]

We describe an experiment container with light scattering and imaging diagnostics for experiments on soft matter aboard the International Space Station (ISS). The suite of measurement capabilities can be used to study different materials in exchangeable sample cell units. The currently available sample cell units and future possibilities for foams, granular media, and emulsions are presented in addition to an overview of the design and the diagnostics of the experiment container. First results from measurements performed on ground and during the commissioning aboard the ISS highlight the capabilities of the experiment container to study the different materials. [ABSTRACT FROM AUTHOR]

The gas permeability of the thin liquid films which separate neighbouring bubbles in a liquid foam plays a key role in foam coarsening. Different approaches have been developed in the past to measure the film permeability, relying on measurements either on individual films/bubbles or on bulk foams. While the first approach may not be sufficiently representative of a real foam film, the latter is hardly feasible due to a lack of quantitative description of the coarsening of bulk foams with non-negligible liquid content. Here we show that a good compromise between these approaches can be achieved by investigating the coarsening of quasi-two-dimensional foams. More precisely, we propose a particularly simple approach in which we follow the evolution of the number of bubbles of an initially monodisperse foam. In this case, a large number of bubbles disappear simultaneously, leading to a “catastrophic” event, which can be identified easily and accurately related to the film permeability. We demonstrate the potential of this technique by using aqueous foams stabilised by sodium dodecyl sulfate having different liquid fractions and containing different gases. The experiments are compared to Surface Evolver simulations. [ABSTRACT FROM AUTHOR]