Nonlinear Electrical Properties of Grain Boundaries in an Oxygen-Ion Conductor (CeO2· Y2O3)

The ceria-yttria solid solution is a good anionic conductor. In polycrystalline ceramics, the complex impedance spectroscopy shows clearly the existence of a significant additional resistance associated with the grain boundaries. In this paper a theoretical analysis of the ac response in the nonlinear regime is developed. In particular the current-voltage and capacitance-voltage characteristics of the grain boundaries are derived. For the material investigated the former is well fitted by the Poole-Frenkel law while the capacitance is voltage independent. These results are in agreement with microscopic STEM observations of a silica-rich second phase.     

Influence of Freezing and Thawing on the Egg Vitelline Membrane

The original method finalized for this study was a direct comparison of the isotheimic dehydration rate between two membrane samples, one subjected to a freezing-thawing cycle, the other being untreated control. Freezing entailed irreversible modifications in the properties of the vitelline membrane of the hen's egg as indicated by a significant increase in the water absorption capacity; an accelerated drying rate; and a marked decrease in the water retention capacity. Through this method, the cryoprotective action of glycerol at the membrane level was also demonstrated.     

Elastic Properties of Some Glasses After Neutron Irradiation

The changes in Young's modulus brought about in various glasses by exposure to irradiation in a nuclear reactor are reported. These changes are a function of glass composition and particularly of the alkali content. The proposed interpretation of the changes observed at low doses is based on comparisons with the temperature ratio of Young's modulus and consideration is given to both a "hot" structural configuration and a rearrangement in cation sites. The changes observed at higher doses are explained by an increase in the specific gravity due to compaction and those at very high doses by tempering.     

Gas exchange in modified atmosphere packaging. 2: Experimental results with strawberries

Strawberries were used to test a new model describing gas transport through micro-perforated polypropylene films and fruit respiration involved in modified atmosphere packaging. Some experiments were conducted with empty packs initially filled with either 100% N₂ or 100% O₂. Simulations agreed very well with experiments only if we replaced the cross-sectional area of the micro-perforations by areas of approximately half the actual areas in order to account for the resistance of air around the perforations. It is also possible to fit the model to gas concentration changes in packs filled with strawberries, although deviations have been due to the contamination of strawberries by fungi. the model was used to quantify the consequences of the variability of pack properties (number of micro-perforations per pack and cross-sectional area of these perforations) on equilibrium gas concentrations and to define minimum homogeneity requirements for modified atmosphere packaging.     

Gas exchange in modified atmosphere packaging. 1: A new theoretical approach for micro-perforated packs

Gas transport and exchange through the perforations in micro-perforated packs used in modified atmosphere packaging were numerically modelled by using Stephan-Maxwell laws, and, outside these perforations, by Fick's law. the model accounts simultaneously for oxygen, carbon dioxide, nitrogen, argon and water vapour. Fruit and vegetable respiration was approximated by Michaelis-Menten kinetics depending on oxygen concentration with an uncompetitive inhibition due to carbon dioxide. Concentration equilibrium was reached after 2 to 3 days, depending on the void volume and on the diffusion properties of the packs. the equilibrium concentrations were dependent on the number of perforations, their diameter, the thickness of the film and the temperature. However, a pack which makes 10% oxygen possible within the pack at 10°C might induce anaerobiosis at 20°C.     

Percutaneous absorption of p-phenylene diamine during an actual hair dyeing procedure

An analytical method has been developed that allows the determination of p-phenylene diamine derivatives in urinary samples collected from women after hair dyeing with commercial formulations. During an on-line flash hydrolysis of the urine, a number of metabolites of p-phenylene diamine were hydrolyzed to free p-phenylene diamine, which was then determined using gas chromatography-mass spectrometry. The excretion of metabolites of p-phenylene diamine could be followed during 24 or 48 hours after the dye had been applied. Most of the p-phenylene diamine cleaved by the flash hydrolysis procedure was, in fact, involved in the N,N'-diacetyl combination. The dose excretion for p-phenylene diamine as measured by this method was comparable to that found by other authors who made use of radioactively labelled material. The present analytical method can be used to evaluate procedures intended to decrease the percutaneous absorption of p-phenylene diamine. Thus, a five- to ten-fold decrease in its penetration was observed by protecting the scalp with clay before applying the dyeing composition.     

Firmness, seed wholeness and water uptake during the cooking of lentils (Lens culinaris cv. anicia) for 'sous vide' and catering preparations

The study aimed to optimize cooking conditions of lentils ( Lens culinaris cv. anicia ) for 'sous vide' processing and catering. the softening rate of lentil seeds during cooking in deionized water was consistent with two simultaneous first order mechanisms. the apparent activation energies of firmness breakdown and loss of integrity were 86.5 kJ mol⁻¹ and 271.3 kJ mol⁻¹, respectively. Wholeness of the lentils was better preserved when the cooking temperature did not exceed 90°C. the loss of firmness was a consequence of hydration of the seed since the regression coefficient between the logarithm of residual firmness and water uptake reached −0.93 regardless of cooking temperature and heating medium (steam or water). Thus, lentil seeds maintained their firmness and wholeness as required for 'sous vide' and catering if they were cooked below 90°C for up to 2 h. Higher temperature or longer cooking time resulted in loss of firmness and wholeness.     

铝合金AA6082(T5)挤压型材基本力学性能试验和成形极限图的建立

对铝合金6082(T5)矩形中空截面挤压型材的基本力学性能进行了实验研究，获得了真实应力应变关系曲线和厚向异性指数rc、r45和r90。采用带缺口的单拉试样，建立了铝合金挤压型材拉弯成形极限图，为拉弯成形破裂现象的研究提供了有效判据。     

On some models for developmental systems. Part XI. Communication between elements of a developmental system

The communication phenomena between cells in multi-cellular organisms can be accounted for by a model of a developmental system that includes an operating system which controls the performance of the operations on certain elements, according to messages from other elements.