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Layer Conductance (layer + conductance)
Selected AbstractsEffects of Stern layer conductance on electrokinetic energy conversion in nanofluidic channelsELECTROPHORESIS, Issue 5 2008Christian Davidson Abstract A thermo-electro-hydro-dynamic model is developed to analytically account for the effects of Stern layer conductance on electrokinetic energy conversion in nanofluidic channels. The optimum electrokinetic devices performance is dependent on a figure of merit, in which the Stern layer conductance appears as a nondimensional Dukhin number. Such surface conductance is found to significantly reduce the figure of merit and thus the efficiency and power output. This finding may explain why the recently measured electrokinetic devices performances are far below the theoretical predictions where the effects of Stern layer conductance have been ignored. [source] The effect of gravity on surface temperatures of plant leavesPLANT CELL & ENVIRONMENT, Issue 4 2003Y. KITAYA ABSTRACT A fundamental study was conducted to develop a facility having an adequate air circulation system for growing healthy plants over a long-term under microgravity conditions in space. To clarify the effects of gravity on heat exchange between plant leaves and the ambient air, surface temperatures of sweet potato and barley leaves and replica leaves made of wet paper and copper were evaluated at gravity levels of 0.01, 1.0, 1.5 and 2.0 g for 20 s each during parabolic aeroplane flights. Thermal images were captured using infrared thermography at an air temperature of 26 °C, a relative humidity of 18% and an irradiance of 260 W m,2. Mean leaf temperatures increased by 0.9,1.0 °C with decreasing gravity levels from 1.0 to 0.01 g and decreased by 0.5 °C with increasing gravity levels from 1.0 to 2.0 g. The increase in leaf temperatures was at most 1.9 °C for sweet potato leaves over 20 s as gravity decreased from 1.0 to 0.01 g. The boundary layer conductance to sensible heat exchange decreased by 5% when the gravity decreased from 1.0 to 0.01 g at the air velocity of 0.2 m s,1. The decrease in the boundary layer conductance with decrease in the gravity levels was more significant in a lower air velocity. Heat exchange between leaves and the ambient air was more retarded at lower gravity levels because of less sensible and latent heat transfers with less heat convection. [source] Control of transpiration in an irrigated Eucalyptus globulus Labill. plantationPLANT CELL & ENVIRONMENT, Issue 2 2000D. A. White ABSTRACT Stomatal conductance and transpiration were measured concurrently in an irrigated Eucalyptus globulus Labill. plantation. Canopy stomatal conductance, canopy boundary layer conductance and the dimensionless decoupling coefficient (,) were calculated (a) summing the conductance of three canopy layers (gc) and (b) weighting the contribution of foliage according to the amount of radiation received (gc,). Canopy transpiration was then calculated from gc and gc, for , = 1 (Eeq), , = 0 (Eimp) and by weighting Eeq and Eimp using , (E,). Eeq, Eimp and E, were compared to transpiration estimated from measurements of heat pulse velocity. The mean value of , was 0·63. Transpiration calculated using gc and assuming perfect coupling (12·5 ± 0·9 mmol m,2 s,1) significantly overestimated measured values (8·7 ± 0·8 mmol m,2 s,1). Good estimates of canopy transpiration were obtained either (a) calculating E, separately for the individual canopy layers or (b) treating the canopy as a single layer and using gc, in a calculation of Eimp (, = 0). The latter approach only required measurement of stomatal conductance at a single canopy position but would be unsuitable for use in combined models of canopy transpiration and assimilation. It should however, be suitable for estimating transpiration in forests regardless of the degree of coupling. [source] | ||||||||||