Microfocus X-ray scattering investigations of eggshell nanotexture

The avian eggshell is a highly ordered calcitic bioceramic composite, with both inorganic and organic constituents. The interactions between the inorganic and organic components within the structure are poorly understood but are likely to occur at the nanometre level. Thus structural variation at this level may impinge on the overall structural integrity and mechanical performance of the eggshell, and therefore analysis at this level is fundamental in fully understanding this ordered structure. In this study, structural changes in the mineral crystallites were investigated by microfocus small-angle X-ray scattering (µSAXS) using synchrotron radiation. Small-angle X-ray scattering (SAXS) can be used to investigate structures on the nanometre scale such as size, shape, arrangement and internal porosity. A microfocused X-ray beam, 1.5 µm vertically by 7 µm, was used to produce vertical linear scans of the eggshell section. SAXS patterns were taken from the eggshell membrane (inner surface of the eggshell) to the cuticle (outer surface of the eggshell). This allowed textural variations within the eggshell to be mapped. The scattering intensity profile was then used to derive the dimension of scattering objects that define the nanotexture. The nanotexture observed may result from the presence of the organic matrix, which is embedded as intracrystalline particles producing voids within the calcified framework of large (>1 µm) calcite crystals. Porod analysis revealed the average size of a scattering interface to be approximately 4.5 nm with small changes that had a depth-dependent variation. These were largest at the mammillary layer/membrane boundary. The palisade layer displayed a small upward trend in size of scattering object. Parallel scans showed that the textural variations observed within the palisade layer are significant and indicate local subtextures. In addition, many of the patterns exhibit diffuse scattering streaks that could result from reflectivity from the larger crystallite interfaces. Changes in the orientation of diffuse streaks were observed within the different layers, the membranes, mammillary layer, palisade layer, vertical crystal layer and cuticle, indicating certain preferred orientations of the crystallites within the layers. The nanotextural variations that are apparent could have implications at the macroscopic level of the resulting eggshell

CFD Mixing Analysis of Jets Injected from Straight and Slanted Slots into Confined Crossflow in Rectangular Ducts

A CFD study was performed to analyze the mixing potential of opposed rows of staggered jets injected into confined crossflow in a rectangular duct. Three jet configurations were numerically tested: (1) straight (0 deg) slots; (2) perpendicular slanted (45 deg) slots angled in opposite directions on top and bottom walls; and (3) parallel slanted (45 deg) slots angled in the same direction on top and bottom walls. All three configurations were tested at slot spacing-to-duct height ratios (S/H) of 0.5, 0.75, and 1.0; a jet-to-mainstream momentum flux ratio (J) of 100; and a jet-to-mainstream mass flow ratio of 0.383. Each configuration had its best mixing performance at S/H of 0.75. Asymmetric flow patterns were expected and predicted for all slanted slot configurations. The parallel slanted slot configuration was the best overall configuration at x/H of 1.0 for S/H of 0.75

CFD mixing analysis of axially opposed rows of jets injected into confined crossflow

A computational fluid dynamics (CFD) parametric study was performed to analyze axially opposed rows of jets mixing with crossflow in a rectangular duct. Isothermal analysis was conducted to determine the influence of lateral geometric arrangement on mixing. Two lateral arrangements were analyzed: (1) inline (jets' centerlines aligned with each other on top and bottom walls), and (2) staggered (jets' centerlines offset with each other on top and bottom walls). For a jet-to-mainstream mass flow ratio (MR) of 2.0, design parameters were systematically varied for jet-to-mainstream momentum-flux ratios (J) between 16 and 64 and orifice spacing-to-duct height ratios (S/H) between 0.125 and 1.5. Comparisons were made between geometries optimized for S/H at a specified J. Inline configurations had a unique spacing for best mixing at a specified J. In contrast, staggered configurations had two 'good mixing' spacings for each J, one corresponding to optimum inline spacing and the other corresponding to optimum non-impinging jet spacing. The inline configurations, due to their smaller orifice size at optimum S/H, produced better initial mixing characteristics. At downstream locations (e.g. x/H of 1.5), the optimum non-impinging staggered configuration produced better mixing than the optimum inline configuration for J of 64; the opposite results were observed for J of 16. Increasing J resulted in better mixing characteristics if each configuration was optimized with respect to orifice spacing. Mixing performance was shown to be similar to results from previous dilution jet mixing investigations (MR less than 0.5)

Handbook for Learning-centred evaluation of Computer-facilitated learning projects in higher education

This handbook supports a project funded by the Australian Government Committee for University Teaching and Staff Development (CUTSD). The amended project title is “Staff Development in Evaluation of Technology-based Teaching Development Projects: An Action Inquiry Approach”. The project is hosted by Murdoch University on behalf of the Australasian Society for Computers in Learning in Tertiary Education (ASCILITE), as a consortium of 11 universities. The rationale of the project is to guide a group of university staff through the evaluation of a Computer-facilitated Learning (CFL1) project by a process of action inquiry and mentoring, supported by the practical and theoretical material contained in this handbook

Is public sector borrowing too high?

In recent years the high level of government borrowing has been at the centre of economic and political debate. On the one hand the public sector borrowing requirement (PSBR) is blamed for record mortgage rates and the threat that industry may be starved of the funds it needs. On the other, proposals which are likely to cut the PSBR are denounced as deflationary and damaging to living standards. Some claim that a high PSBR is a cause of inflation, whilst others argue that if proper account is taken of inflation the PSBR is much less formidable than it seems. This article attempts to set out some facts about the sources and extent of public sector borrowing and to consider briefly some of the issues involved