Porous medium modeling and parameter sensitivity analysis of 1-MCP distribution in boxes with apple fruit

1-methylcyclopropene (1-MCP) is a gas used commercially in cold storage rooms to delay ripening of fruit. It is currently not known how the gas distributes in the bins and is taken up by the fruit. Here a porous-medium model is developed based on volume averaging of the transport equations of momentum and 1-MCP in the air and product. The proposed model was compared with experimental data and validated direct-CFD model. The velocity field in and around the stack were well reproduced by the porous medium model. Concentration predictions were in average 4% and maximally 7% over the average measured values. The porous medium model also agrees well with the direct-CFD model. Influential model parameters were identified through parameter sensitivity study. Porosity, skin mass transfer coefficient and specific surface area strongly affect the simulation. Accordingly model simplifications were suggested and recommended for commercial cold storage rooms.     

Ferroelectric BaTiO3/SrTiO3 multilayered thin films for room-temperature tunable microwave elements

Ferroelectric BaTiO₃/SrTiO₃ with optimized c-axis-oriented multilayered thin films were epitaxially fabricated on (001) MgO substrates. The microstructural studies indicate that the in-plane interface relationships between the films as well as the substrate are determined to be (001)_SrTiO3//(001)_BaTiO3//(001)_MgO and [100]_SrTiO3//[100]_BaTiO3//[100]_MgO. The microwave (5 to 18 GHz) dielectric measurements reveal that the multilayered thin films have excellent dielectric properties with large dielectric constant, low dielectric loss, and high dielectric tunability, which suggests that the as-grown ferroelectric multilayered thin films can be developed for room-temperature tunable microwave elements and related device applications.     

Bioassay of an endothelium-derived hyperpolarizing factor from bovine coronary arteries: role of a cytochrome P450 metabolite

An endothelium-derived hyperpolarizing factor (EDHF) mediates a part of the vasodilatory action of bradykinin. A bioassay method was developed to investigate the properties of EDHF on bovine coronary arterial smooth muscle cells. Cannulated bovine coronary arteries with an intact endothelium that were treated with indomethacin and NG-nitro-L-arginine methyl ester served as the EDHF donor. The effect of the donor vessel perfusate was examined on a 240 pS single-channel calcium (Ca2+)-activated potassium (K+) current (KCa) and resting membrane potential in recipient coronary arterial smooth muscle cells. The open state probability (NPo) of the channel averaged 0.011 +/- 0.003 during basal perfusate flow. After stimulation of the donor vessels with bradykinin (10(-10)-10(-6) M), the perfusate induced a 1.2- to 5-fold increase in the NPo (n = 7, p < 0.001). This increase in channel activity was attenuated by either removing the endothelium of the donor arterial segment or upon inhibition of cytochrome P450 in the donor arterial segment with the combination of 17-octadecynoic acid and miconazole. The resting cell membrane averaged -60 +/- 2 mV, and hyperpolarized to -69 +/- 1.5 mV (n = 6, p < 0.05) in response to the perfusate following stimulation of the donor vessel with bradykinin. Addition of 14, 15-epoxyeicosatrienoic acid mimicked the effects of the perfusate and increased the NPo of the KCa channel from 0.01 +/- 0.001 to 0.05 +/- 0.001. These findings suggest that bradykinin stimulates the release of a transferable endothelial factor that activates KCa channels and hyperpolarizes coronary arterial smooth muscle cell membranes. These findings support the hypothesis that coronary arteries release an EDHF which is a cytochrome P450 metabolite of arachidonic acid.     

Forced-convective cooling of citrus fruit: Package design

Optimisation of package design for citrus fruit is required to increase the throughput, by reducing the precooling time, and to enhance fruit quality by providing fast and uniform cooling without inducing chilling injury. The cooling performance of an existing container and of two new containers (Supervent and Ecopack), as stacked on a pallet, was evaluated experimentally and numerically with computational fluid dynamics (CFD). The accuracy of the CFD simulations was confirmed by a good agreement with experiments. The best cooling performance was found for Ecopack, but removing airflow short circuits in this container may enhance the cooling performance even more. Also with respect to uniformity of cooling of the fruit and the magnitude of the convective heat transfer coefficients, in a specific container and between different containers on the pallet, the Ecopack container performed best, followed by the Supervent and the standard container. The new container designs thus clearly showed significant improvements in cooling performance.     

Geological challenges in constructing the proposed Geba dam site, northern Ethiopia

It is proposed to construct a dam across the Geba River, Ethiopia. The paper reports the engineering geological investigations undertaken, including mapping, discontinuity surveys, core drilling, water absorption testing and sampling for laboratory tests. The complexity of the site, with limestones and interbedded limestone-shale horizons, is indicated by the variability of the RQD and Lugeon values. Of the 63 tests undertaken, some two-thirds had Lugeon values implying grouting was necessary. Following removal and replacement of the alluvial deposits in the central area, a grout curtain including two to three rows of grouting holes was recommended to a depth of 100 m for the left abutment, 35 m for the central foundation and 60 m for the right abutment.