SHAPE OF GRAIN BOUNDARY GROOVE ONPURE ICE SURFACE

In this work we studied the evolution of the groove that forms the grain boundary (BG) when it emerges to a free surface, in the presence of different processes of matter transport. By using a confocal microscope, the shape of the grain edge groove was obtained in an ice sample with orientation< 1010 >/50◦ at −5◦C ; after keeping it 3 h in an environment with dry air. The shapes and depths of the grain boundary groove obtained experimentally, at regular time periods, were satisfactorily fitted considering a process of transport of matter developed by Srinivasan and Trivedi. In this model the transport of matter is mainly ruled by gaseous diffusion and not by surface diffusion.

SHAPE OF GRAIN BOUNDARY GROOVE ONPURE ICE SURFACE

In this work we studied the evolution of the groove that forms the grain boundary (BG) when it emerges to a free surface, in the presence of different processes of matter transport. By using a confocal microscope, the shape of the grain edge groove was obtained in an ice sample with orientation <1010>/50◦at −5◦C ; after keeping it 3 h in an environment with dry air. The shapes and depths of the grain boundary groove obtained experimentally, at regular time periods, were satisfactorily fitted considering a process of transport of matter developed by Srinivasan and Trivedi. In this model the transport of matter is mainly ruled by gaseous diffusion and not by surface diffusion.

Ni-Co single atomic anchored conjugated microporous polymer for high-performance photocatalytic hydrogen evolution

The fabrication of single atomic photocatalysts via a simple pathway is a crucial challenge to enable efficient production of hydrogen. Herein, we demonstrate a gaseous diffusion strategy to construct single...

Fischer-Tropsch reaction mixture permeation through a silicalite-1 membrane reactor and its effect on the produced hydrocarbons distribution

The quantification of the permeation of the Fischer-Tropsch reaction mixture through a silicalite-1 zeolite membrane in which is integrated in to fixed bed reactor was theoretically investigated. The approach is based on the prediction of the permeation parameters by using two different mechanisms including surface diffusion and gaseous diffusion. It was found that under our investigated conditions, the total permeation could be governed by surface diffusion model since the contribution of this mechanism is dominant versus the gaseous diffusion. Noteworthy, our results show that except for the selective gas permeation of carbon dioxide, the measuring factors of different permeates were proportional to the operating pressure. Hydrocarbons with low molecular weight diffuse greater than long-chain hydrocarbons. Furthermore, the high adsorbed molecules are more likely to be affected by the high processing temperature. It can be also highlighted that the permeate amounts has no important effect on the product distribution which is characterized by the olefins to paraffins ratios. So the assumption that considers the separation of CO 2 without assuming other components permeation is well supported.

Where in the leaf is intercellular CO2 (Ci)? Considerations and recommendations for assessing gaseous diffusion in leaves

The assumptions that water vapor exchange occurs exclusively through stomata, that the intercellular airspace is fully saturated with water vapor, and that CO2 gradients are negligible between stomata and the intercellular airspace have enabled significant advancements in photosynthetic gas exchange research for nearly 60 years via calculation of intercellular CO2 (Ci). However, available evidence suggests that these assumptions may be overused. Here we review the literature surrounding evidence for and against the assumptions made by Moss & Rawlins (1963). We reinterpret data from the literature by propagating different rates of cuticular water loss, CO2 gradients, and unsaturation through the data. We find that in general, when cuticle conductance is less than 1% of stomatal conductance, the assumption that water vapor exchange occurs exclusively through stomata has a marginal effect on gas exchange calculations, but this is not true when cuticle conductance exceeds 5% of stomatal conductance. Our analyses further suggest that CO2 and water vapor gradients have stronger impacts at higher stomatal conductance, while cuticle conductance has a greater impact at lower stomatal conductance. Therefore, we recommend directly measuring Ci whenever possible, measuring apoplastic water potentials to estimate humidity inside the leaf, and exercising caution when interpreting data under conditions of high temperature and/or low stomatal conductance, and when a species is known to have high cuticular conductance.HighlightLeaf water vapor and CO2 exchange have been successfully used to model photosynthetic biochemistry. We review critical assumptions in these models and make recommendations about which need to be re-assessed.

ESTUDIO DE LA EVOLUCIÓN SUPERFICIAL DE UN BORDE DE GRANO EN HIELO PURO POR PROCESOS EVAPO-DIFUSIVOS

In this work, we studied the evolution of the groove that forms the grain boundary (BG)when it emerges to a free surface, in the presence of different processes of matter transport. The depth of a groove of the BG was obtained in an ice sample with orientation <1010>/50º at -5 ºC for 3h in dry air, by using a confocal microscope. The experimental results are fitted correctly with a process of transport of matter governed mainly by gaseous diffusion.