Reduction of folic acid during baking and implications for mandatory fortification of bread

A pilot scale study designed to quantify the reduction of folic acid during bread baking in Ireland was undertaken. Flour was fortified with different concentrations of folic acid and used to make four different types of commercial bread. The dispersal of folic acid in flour on a pilot scale was variable but better homogeneity would have been achieved in the final bread due to batch size and thorough mixing of the dough. Generally, the heat degradation of folic acid during baking was between 21.9% and 32.1%. Whilst the percentage degradation of folic acid in white pan loaves, white baguettes and brown soda bread were similar the result in wholemeal bread was found to be significantly higher than in other bread types tested. Taking into account all variables affecting folic acid concentration during baking, a concentration of c. 225 μg 100 g^?1 folic acid would be needed in flour to deliver commercial bread in Ireland with an average folic acid content of 120 μg 100 g^?1 in line with Government requirements.     

The indentation of a half-space of hexagonal elastic material by a circular punch of arbitrary end-profile

Summary The problem is considered of the indentation by a smooth rigid punch of a half-space composed of linear elastic material of hexagonal symmetry whose plane boundary is parallel to the basal planes. The case is considered in which the area of contact between the punch and the half-space is circular, the end of the punch with is in contact with the half-space having an arbitrary profile. An integral equation is formulated and solved for the boundary value of the normal displacement in the half-space, and an expression is derived for the distribution of pressure under the punch.     

An algorithm for three-dimensional convection and diffusion with very different horizontal and vertical length scales

An algorithm is developed and tested for the numerical solution of the three-dimensional convection—diffusion equation appropriate for the marine environment, in which the horizontal and vertical scales differ by one or two orders of magnitude. The algorithm splits the horizontal and vertical parts of the process, treating the horizontal convection and diffusion explicitly and the vertical convection and diffusion by an implicit finite element method that is unconditionally stable. The overall stability conditions on the algorithm are discussed and its accuracy is verified through a number of test problems whose exact solutions are known.     

Behavior of indentation cracks near free surfaces and interfaces

The purpose of this research was to examine problems associated with the propagation of cracks near a free surface and near the interface of a glass/epoxy bonded system. Crack propagation was induced by placing Knoop indentations in the glass at various sites adjacent to and remote from the surface or interface. These experimental studies were supplemented by finite element stress analysis. Experiments show that for an indent parallel to the surface or interface, the initial direction of crack propagation from the indent is always toward the surface or interface and then as the crack approaches the surface or interface, the crack path deviates away from the surface. Results of finite element analysis show that the initial direction of crack propagation is in the direction normal to the maximum principal stress at the crack tip.

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Résumé Le but de cette recherche a été d'examiner les problèmes associés à la propagation des fissures près d'une surface libre et au voisinage de l'interface d'un assemblage verre-époxy collé. La propagation d'une fissure était blovoquée par des empreites Knoop en divers endroits adjacents ou éloignés de la surface ou de l'interface. Ces tudes expérimentales ont été complétées par une analyse des contraintes par éléments finis. Les essais ont montré The pour une empreinte parallèle à la surface ou à l'interface, la direction initiale de la propagation d'une fissure depuis cette empreinte est toujours orientée vers la surface libre ou vers l'interface. Ensuite, au fur et à mesure que fissure se rapproche de la surface libre ou de l'interface, son chemin s'en détourne. Les résultats de l'analyse par Sléments finis montrent que la direction initiale de propagation de la fissure est normale à la tension principale maximum à l'extrémité de la fissure.

     

Observations on Finger-like Crack Growth at a Urethane Acrylate/Glass Interface

Interfacial crack growth behavior along a urethane acrylate/glass interface is characterized by the development of finger-like perturbations along the advancing crack front. The finger-like perturbations grow from a slightly irregular crack front until they reach a steady-state where the velocity of the finger tips equals the velocity of the finger valleys. Once the fingers reached steady-state, the crack velocity was dependent on the applied strain energy release rate via a power law relationship where the exponent was independent of test humidity; however, the multiplicative constant A decreased by an order of magnitude from 80 to 15% RH. The spacing of the fingers was found to be independent of the crack′s velocity and the relative humidity of the environment.     

Stability of the numerical solution of a parabolic system with integral subsidiary conditions

A coupled parabolic system is considered in which two of the usual boundary conditions are replaced by integral subsidiary conditions. A numerical scheme based on a generalization of the Crank-Nicholson method is described. Necessary and sufficient conditions on the two implicitness parameters in the scheme are derived in order that the algorithm be stable.     

Vibration of beams with exponentially varying properties

Summary The equation governing the transverse vibration of beams with exponentially varying properties is solved. The solution is expressed in terms ofBessel functions for a sequence of special cases of property variations.

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Zusammenfassung Die Gleichung für die Biegeschwingung von Stäben mit exponentiel veränderlichen Querschnittseigenschaften wird gelöst. Für verschiedene Spezialfälle der Eigenschaftsvariation wird die Lösung durchBesselsche Funktionen ausgedrückt.

     

Further analysis of the DCDC specimen with an offset hole

The results of He et al. (1995) for the Double Cleavage Drilled Compression (DCDC) specimen are extended to cover the case where both the hole and crack are offset from the centerline of the specimen. The effect of the thickness of an adhesive layer on the value of the energy release is also investigated. The applicability of the results to experimental studies is presented.     

Fatigue Crack Propagation at Polymer Adhesive Interfaces

Fatigue (slow) crack growth in epoxy/glass, epoxy acrylate/glass and epoxy/PMMA interfaces was studied under constant and cyclic loading at both high and low humidities using the interfacial, four-point flexure test. Finite element analysis was used to determine the energy release rate and phase angle appropriate for the different crack geometries observed. The experimental results show that for the polymer/glass interfaces, the primary driving force for fatigue crack growth is the applied energy release rate at the crack tip and that increasing test humidity enhances crack growth under constant loading but has an insignificant effect under cyclic loading. At low humidity the crack growth rates under cyclic loading are significantly greater than under constant loading. For epoxy/PMMA interfaces the crack growth results were independent of the applied energy release rate, relative humidity, and cyclic vs. constant loading, within experimental scatter. In addition, for polymer/glass interfaces the effect of phase angle (13 to 54°) on crack growth rates is not significant. However, for epoxy/PMMA interfaces the applied energy release rate for the initiation of crack growth is considerably greater for a phase angle of 66° than for 5°, indicating that increasing shear at the crack tip makes the initiation of crack growth more difficult. These results are discussed in terms of possible mechanisms of fatigue crack growth at polymer adhesive interfaces.     

The use of ferro-silicate slag from ISF zinc production as a sand replacement in concrete

Technical studies have shown that ferro-silicate slag from the Imperial Smelting Furnace (ISF slag) production of zinc can be used as a replacement for sand in cementitious mixes. The ISF slag contains trace quantities of zinc and lead, which are known to cause retardation of concrete set. Testing of experimental concrete mixes proves this retardation affect, although the delay in set does not appear deleterious to the eventual concrete hydration. If a gelatinous layer containing lead and zinc ions is formed around the cement grains in the concrete mix, set begins when this layer is disrupted and then continues as it would as if no zinc or lead had been present. Leaching studies demonstrate that pulverized-fuel ash and ground granulated blastfurnace slag have the potential to reduce the leaching of lead and zinc ions from the ISF slag, even in highly alkaline solutions.