Spontaneous honeybee behaviour is altered by persistent organic pollutants

The effect of environmental pollutants on honeybee behaviour has focused mainly on currently used pesticides. However, honeybees are also exposed to persistent organic pollutants (POPs). The aim of this laboratory based study was to determine if exposure to sublethal field-relevant concentrations of POPs altered the spontaneous behaviour of foraging-age worker honeybees. Honeybees (Apis mellifera) were orally exposed to either a sublethal concentration of the polychlorinated biphenyl (PCB) mixture Aroclor 1254 (100 ng/ml), the organochlorine insecticide lindane (2.91 ng/ml) or vehicle (0.01% DMSO, 0.00015% ethanol in 1M sucrose) for 1–4 days. The frequency of single event behaviours and the time engaged in one of four behavioural states (walking, flying, upside down and stationary) were monitored for 15 min after 1, 2, 3 and 4 days exposure. Exposure to Aroclor 1254 but not lindane increased the frequency and time engaged in honeybee motor activity behaviours in comparison to vehicle. The Aroclor 1254—induced hyperactivity was evident after 1 day of exposure and persisted with repeated daily exposure. In contrast, 1 day of exposure to lindane elicited abdominal spasms and increased the frequency of grooming behaviours in comparison to vehicle exposure. After 4 days of exposure, abdominal spasms and increased grooming behaviours were also evident in honeybees exposed to Aroclor 1254. These data demonstrate that POPs can induce distinct behavioural patterns, indicating different toxicokinetic and toxicodynamic properties. The changes in spontaneous behaviour, particularly the PCB-induced chronic hyperactivity and the associated energy demands, may have implications for colony health

Incorporation Of Water-Soluble Porphyrins In Sol-Gel Matrices And Application To pH Sensing

The incorporation of H₂TPPS⁴- into sol-gel materials has been used to determine the pH inside a sol-gel matrix

Two-phase damping for internal flow: Physical mechanism and effect of excitation parameters

International audienceTwo-phase flow induced-vibration is a major concern for the nuclear industry. This paper provides experimental data on two-phase damping that is crucial to predict vibration effects in steam generators. An original test section consisting of a tube subjected to internal two-phase flow was built. The tube is supported by linear bearings and compression springs allowing it to slide in the direction transverse to the flow. An excitation system provides external sinusoidal force. The frequency and magnitude of the force are controlled through extension springs. Damping is extracted from the frequency response function of the system. It is found that two-phase damping depends on flow pattern and is fairly proportional to volumetric fraction for bubbly flow. Measurements are completed by the processing of high-speed videos which allow to characterize the transverse relative motion of the gas phase with respect to the tube for bubbly flow. It is shown that the bubble drag forces play a significant role in the dissipation mechanism of two-phase damping.Les vibrations induites par les écoulements diphasiques sont une préoccupation majeure pour l'industrie nucléaire. Cet article présente des expériences de mesure de l’amortissement diphasique. La connaissance de l’amortissement diphasique est cruciale pour prédire les vibrations dans les générateurs de vapeur. Une section d’essai composée d'un tube de section carré soumis à écoulement interne diphasique a été construite. Le tube est soutenu par des roulements linéaires et des ressorts de compression lui permettant de se déplacer dans la direction transversale à l'écoulement. Un système d'excitation fournit une force sinusoïdale externe. La fréquence et l'amplitude de la force excitatrice forces sont contrôlées par des ressorts d'extension. L'amortissement est extrait de la fonction de transfert du système. Il est constaté que l'amortissement diphasique dépend du régime d'écoulement. Pour un écoulement à bulles, l'amortissement diphasique est quasiment proportionnel à la qualité volumétrique. De plus un traitement des vidéos à haute vitesse ont permis de caractériser le mouvement relatif transversale de la phase gazeuse par rapport au tube pour un écoulement à bulles. Il est montré que la trainée de la bulle joue un rôle essentiel dans le mécanisme de d'amortissement diphasique

Two-phase damping in vertical pipe flows: Effect of void fraction, flow rate and external excitation

Predicting vibration effects in steam generators requires good knowledge of two-phase damping ζ2φ. The purpose of this work is to correlate two-phase damping in axial flow with tube transversal excitation frequency and magnitude. The test section consists of a stiff square tube subjected to internal axial flow of air-water mixture. The hydraulic diameter is 3 inches. The tube is supported with linear bearings and fitted with flexible tubing on both ends to allow motion in the transverse direction. Compression springs allow setting the natural frequency of the tube oscillation. A motor provides transverse sinusoidal excitation to the tube assembly. ζ2φ is determined from the frequency response function. As a result of this study, ζ2φ is represented as a function of excitation frequency and amplitude, void fraction and flow rate. Specific information is gained through high frame rate videos of the oscillating tube, including bubble transverse velocity and size for low void fraction, and flow pattern transitions. Indeed, it is suspected that two-phase damping is partly caused by the work rate of virtual mass forces of the gas phase. Better knowledge of the physical process involved in two-phase damping will allow better modeling and prediction of tube behavior.</jats:p

Electrochemical preparation of anthraquinone and zinc porphyrin coated electrodes: redox activity and film stability

This study concerns some aspects of the electrochemical design and characterization of zinc porphyries and anthraquinone-based polymers. The electro-formation of the films on the electrode surface has been achieved by cyclic voltammetry in organic solvents such as dichloromethane and acetonitrile. It is based on the electrochemical oxidative polymerization of the pyrrole or hydroxy-substituted phenyl groups attached to the porphyrin or anthraquinone molecules. The redox characteristics of the polymer films as well as their stability were studied by cyclic voltammetry and spectrophotometry and are compared to those of the starting monomers. The conditions of the electropolymerization of stable and reproducible multicomponent films are also discussed