Two antagonistic effects of flow/mixing on reactive polymer blending

Reactive polymer blending is basically a flow/mixing-driven process of interfacial generation, interfacial reaction for copolymer formation and morphology development. This work shows two antagonistic effects of mixing on this process: while mixing promotes copolymer formation by creating interfaces and enhancing collisions between reactive groups at the interfaces, excessive mixing may pull the in-situ formed copolymer out of the interfaces to one of the two polymer components of the blend, especially when the copolymer becomes highly asymmetrical. As such, the copolymer may loss its compatibilization efficiency. The mixing-driven copolymer pull-out from the interfaces is a catastrophic process (less than a minute), despite the high viscosity of the polymer blend. It depends on the molecular architecture of the reactive compatibilizer, polymer blend composition, mixing intensity and annealing. These findings are obtained using the concept of reactive tracer-compatibilizer and a model reactive polymer blend.

Multiple anthropogenic stressors have inconsistent cumulative effects across a large spatial gradient

Biodiversity is declining, typically because of multiple anthropogenic stressors. Cumulative effects of multiple stressors are classified as additive, when cumulative effects are as expected from the stressor’s singular effects, synergistic when greater than additive or antagonistic when less than additive. Less attention has been given to the consistency of cumulative effects. We analysed stream insects, Ephemeroptera, Plecoptera and Trichoptera (EPT) data from two habitats spanning a 3,600 km latitudinal (S11◦-S43◦) gradient in eastern Australia. We found that the cumulative effect of salinity and suspended sediments on EPT family richness was inconsistent with additive, synergistic or antagonistic effects, and the reduction EPT family richness from increasing both stressors varied (48-70%) depending on habitat (riffle vs. edge), water temperature and terrain slope. Studies of cumulative effects of multiple stressors at one location risk not describing cumulative effects elsewhere and ecologists should consider the spatial consistency of multiple stressors.

Effect of methanol extract of Anacardium occidentale stem bark on agonist-induced contraction in rat uterine muscle

Anacardium occidentale (Ao) is widely used in ethnomedicine and the effect on contractility of the gut and heart muscles of laboratory rodents have been established however, its effect on the contractility of uterine muscle has been rarely researched. The present study investigated the effect of stem bark methanolic extract of Anacardium occidentale (AoME) on Isolated Rat Uterus Strips (IRUS). The Anacardium occidentale methanol extract (AoME) was obtained by solvent extraction. The IRUS were suspended in a bath containing 15 ml of De Jalon's solution through a silk connected to a force transducer. A tension of 1.0 g was applied. The strips were allowed to equilibrate for a period of 60–90 min before the commencement of the experiment. The extract (0.025- 0.3mg/ml) added cumulatively did not modify the normal tonus in most of the IRUS used except in one where it feebly contracted it. However, the contractile responses induced by acetylcholine (10-9 -10-5 M) and oxytocin (10-9 -10-5 M) on the IRUS were almost completely blocked by pre-incubated AoME at a concentration of 0.2 mg/ml. Stem bark methanol extract of Anacardium occidentale shifted the log concentration curve of both agonists to the right. The present results report the antagonistic effects of stem bark methanol extract of Anacardium occidentale on oxytocin and acetylcholine-induced contraction in rat uterus strips. Keywords: Anacardium occidentale, Oxytocin, Acetylcholine, Uterus, Smooth muscle