Pea aphids (Hemiptera: Aphididae) have diurnal rhythms when raised independently of a host plant

Seasonal timing is assumed to involve the circadian clock, an endogenous mechanism to track time and measure day length. Some debate persists, however, and aphids were among the first organisms for which circadian clock involvement was questioned. Inferences about links to phenology are problematic, as the clock itself is little investigated in aphids. For instance, it is unknown whether aphids possess diurnal rhythms at all. Possibly, the close interaction with host plants prevents independent measurements of rhythmicity. We reared the pea aphid Acyrthosiphon pisum (Harris) on an artificial diet, and recorded survival, moulting, and honeydew excretion. Despite their plant-dependent life style, aphids were independently rhythmic under light-dark conditions. This first demonstration of diurnal aphid rhythms shows that aphids do not simply track the host plant's rhythmicity

No Pain, no Gain? Investigating motivational mechanisms of game elements in cognitive tasks

The literature on serious games and gamification suggests that game elements have a positive influence on learning and performance in cognitive tasks. However, the mechanisms by which game elements affect these outcomes are not well understood. Building on theorizing in the self-control literature, the present research investigated whether game elements change the subjective experience of a cognitive task in terms of the positive affect, motivational conflict, and subjective effort experienced. Further, we tested whether people with a low versus high level of self-control benefit more from game elements in terms of their performance. The results of two experimental studies suggest that the gamification of an n-back task did not improve task accuracy (i.e., correct responses) directly but reduced task disengagement (i.e., non-responses). Further, gamification prevented positive affect from dropping over the course of the task and reduced motivational conflict and subjective effort experienced. Only positive affect mediated the effect of game elements on task disengagement. Further, game elements had an indirect effect on task accuracy via subjective effort. There was no indication that individuals with lower delay of gratification or lower trait self-control would profit more from gamification. The implications of these findings for the literature on self-control and gamification are discussed

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Fuel-nitrogen conversion in the combustion of small amines using dimethylamine and ethylamine as biomass-related model fuels

Lucassen A, Zhang K, Warkentin J, et al. Fuel-nitrogen conversion in the combustion of small amines using dimethylamine and ethylamine as biomass-related model fuels. Combustion and Flame. 2012;159(7):2254-2279.Laminar premixed flames of the two smallest isomeric amines, dimethylamine and ethylamine, were investigated under one-dimensional low-pressure (40 mbar) conditions with the aim to elucidate pathways that may contribute to fuel-nitrogen conversion in the combustion of biomass. For this, identical flames of both fuels diluted with 25% Ar were studied for three different stoichiometries (Phi = 0.8, 1.0, and 1.3) using in situ molecular-beam mass spectrometry (MBMS). Quantitative mole fractions of reactants, products and numerous stable and reactive intermediates were determined by electron ionization (EI) MBMS with high mass resolution to separate overlapping features from species with different heavy elements by exact mass. Species assignment was assisted by using single-photon vacuum-ultraviolet (VUV) photoionization (PI) MBMS. The results indicate formation of a number of nitrogenated intermediates, including toxic species such as HCN, in appreciable concentrations. Such intermediate species mole fractions may depend not only on stoichiometry, but also on fuel structure. We attempted to analyze the major pathways in the two flames with a detailed combustion model developed for this purpose. For this, thermochemical values for a number of intermediates had to be determined from quantum chemistry calculations. Also, specific sets of reactions were incorporated for the two fuels. While many trends seen in the experiments can be successfully reproduced by the simulations, additional efforts may be needed to reliably describe the fuel-nitrogen chemistry in the combustion of biomass-related model fuels with amine functions. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved