Inward Migration of Glass‐Modifier Cations During Heat Treatment Under an N2 Atmosphere

An Na⁺/Ca²⁺‐deficient layer is observed to form on the glass surface region up to a depth of hundreds of nanometers when a soda‐lime‐silicate glass is heat treated under an N₂ atmosphere near its glass‐transition temperature. The measurements were performed using X‐ray photoelectron spectroscopy with C₆₀‐ion sputtering (C₆₀‐XPS) and dynamic secondary‐ion mass spectrometry (D‐SIMS) with consideration of the mass and charge balances. The increase in the amount of hydrogen is substantially less than the decrease in the total charge due to the loss of modifier cations in the Na⁺/Ca²⁺‐deficient layer; furthermore, the oxygen concentration in this layer is lower than the bulk value, suggesting that the silanol groups in the surface layer of the glass are dehydrated. A high‐concentration layer of Ca²⁺ is also confirmed in the dehydration layer of the glass heat treated under an N₂ atmosphere, suggesting that Na⁺ and Ca²⁺ ions migrate inward into the glass via an ion‐exchange reaction with protons, which migrate toward the surface from the bulk. We also confirmed that a thicker Na⁺/Ca²⁺‐deficient layer is formed on glass surfaces with higher water content. Our results suggest that the dehydration of the silanol groups is the driving force of the inward migration of Na⁺ and Ca²⁺ ions.     

Numerical study for enhancement of laminar flow mixing using multiple confined jets in a micro-can combustor

To meet demands arising as a result of present trends towards miniaturization, an innovative design for promoting mixing enhancement in a miniature can combustor is investigated using an unstructured finite-volume technique. A multi-holed baffle plate is employed to create a ring of oxidizer jets surrounding a single fuel jet in parallel with the axis of the cylindrical chamber. The baffle plate is found to produce a dramatic improvement to the mixing performance when compared with simpler co-axial jet cases. Relatively small changes in geometry are found to have a major influence on mixing for laminar isothermal flow.     

Medium‐chain fatty acids – Nutritional function and application to cooking oil

Medium‐chain fatty acids, which are saturated fatty acids composed of 8–10 carbons, have unique nutritional characteristics different from those of long‐chain fatty acids. Medium‐chain triacylglycerol (MCT) is more readily digested and absorbed than long‐chain triacylglycerol (LCT), and easily utilized as energy. The use of MCT as an edible oil is limited because it has a low smoking point and easily foams during deep‐frying like lauric acid does. Medium‐ and long‐chain triacylglycerol (MLCT) prepared by transesterification between MCT and LCT has a higher smoking point and reduced foaming property. MLCT oil has been shown to result in less body fat accumulation in animal and human studies. It has been approved as a food for specified health use (FOSHU) and widely sold in Japan as a cooking oil less likely to lead to body fat accumulation.