Anomalous diffraction by arbitrarily oriented ellipsoids: applications in ektacytometry

Anomalous diffraction by an arbitrarily oriented ellipsoid with three different axes is derived. From the resulting expression the relationship between the shape of the ellipsoid and the intensity pattern is immediately evident: The axial ratio of the elliptical isointensity curve equals the axial ratio of the elliptical projected area of the ellipsoid. A comparison of anomalous diffraction with calculations performed with the T-matrix method reveals that the anomalous diffraction approximation is highly accurate for single ellipsoidal red blood cells. Application of the expression for anomalous diffraction by ellipsoids to a population of red blood cells shows that, even in a red-cell suspension as examined in an ektacytometer, the axial ratio of the isointensity curves is equal to the mean axial ratio of the red blood cells in the population. In ektacytometry this relationship between cell shape and intensity pattern is commonly assumed to hold true without reference to the light-scattering properties of the cells. The results presented here show that this assumption is valid, and we offer a profound theoretical basis for it by considering in detail the light scattering by the red blood cells.     

Surface spin polarization in Fe(1 1 0) and Ni(1 1 0)

The magnetism of Ni(1 1 0) and Fe(1 1 0) surfaces was investigated by electron capture spectroscopy. He⁺ and He²⁺ ions impinged on the Fe(1 1 0) and Ni(1 1 0) surfaces under grazing incidence, and the degree of polarization of the light emitted by the neutralized projectiles was analyzed. Our measurements show that in Ni(1 1 0) minority electrons have a higher density of states at the Fermi energy than majority electrons, opposed to the Fe(1 1 0) case. From a comparison of our measurements we estimate the ratio between captured minority and majority electrons in Ni(1 1 0) to be similar as the ratio between captured majority and minority electrons in Fe(1 1 0).     

Endothelial repair process and its relevance to longitudinal neointimal tissue patterns: comparing histology with in silico modelling

Re-establishing a functional endothelium following endovascular treatment is an important factor in arresting neointimal proliferation. In this study, both histology (in vivo) and computational simulations (in silico) are used to evaluate neointimal growth patterns within coronary arteries along the axial direction of the stent. Comparison of the growth configurations in vivo and in silico was undertaken to identify candidate mechanisms for endothelial repair. Stent, lumen and neointimal areas were measured from histological sections obtained from eight right coronary stented porcine arteries. Two re-endothelialization scenarios (endothelial cell (EC) random seeding and EC growth from proximal and distal ends) were implemented in silico to evaluate their influence on the morphology of the simulated lesions. Subject to the assumptions made in the current simulations, comparison between in vivo and in silico results suggests that endothelial growth does not occur from the proximal and distal ends alone, but is more consistent with the assumption of a random seeding process. This may occur either from the patches of endothelium which survive following stent implantation or from attachment of circulating endothelial progenitor cells.     

Native and generic parallel programming environments on a transputer and a PowerPC platform

Genericity of parallel programming environments, enabling development of portable parallel programs, is expected to result in performance penalties. Furthermore, programmability and tool support of programming environments are important issues if a choice between programming environments has to be made. In this paper we propose a methodology to compare native and generic parallel programming environments, taking into account such competing issues as portability and performance. As a case study, this paper compares the Iserver-Occam, Parix, Express and PVM parallel programming environments on a 512-node Parasytec GCel. Furthermore, we apply our methodology to compare Parix and PVM on a new architecture, a 32-node Parsytec PowerXplorer, which is based on the PowerPC chip. In our approach we start with a representative application and isolate the basic (environment)-dependent building blocks. These basic building blocks, which depend on floating-point performance and communication capabilities of the environments, are analysed independently. We have measured point-to-point communication times, global communication times and floating-point performance. All information is combined into a time complexity analysis, allowing comparison of the environments on different degrees of functionality. Together with demands for portability of the code and development time (i.e. programmability), an overall judgement of the environments is given.     

Collaborative study on the use of motility enrichment on modified semisolid Rappaport-Vassiliadis medium for the detection of Salmonella from foods.

A collaborative study was performed in 15 laboratories to evaluate the use of motility enrichment on modified semisolid Rappaport-Vassiliadis (MSRV) medium for rapid Salmonella detection in a variety of food products. The results of this procedure were compared with those obtained by the cultural procedure using Rappaport-Vassiliadis (RV) broth as selective enrichment and modified brilliant green agar for selective plating. The tests were performed with Salmonella reference samples (SRS) as well as with naturally contaminated food products. When SRS were used without added food the productivity of both MSRV and RV was 96%. When SRS were combined with reference samples containing competitive bacteria the productivity was 98% for MSRV and 95% for RV. In the tests with food samples the productivity of MSRV was 92% with SRS added to food and 96% with naturally contaminated samples, while the productivity of RV was 88% and 90%, respectively. Statistical analysis showed that there was no significant difference between the procedures.     

Release of Bisphenol A from Polycarbonate—A Review

The release of Bisphenol A (BPA) from polycarbonate baby bottles into food and food simulants is reviewed in the perspective of the current intensive discussions on the risks of this substance. Potential factors that have been reported to influence the release of BPA are reviewed. Unlike most polymers polycarbonate is hydrolyzed under alkaline conditions by scale formation, residual alkaline detergents and boiled water. Data suggest that brushing of the bottle did not raise the release of BPA. Claims that used bottles release more BPA than new bottles and that mineral composition of the aqueous food simulant affect release could not be substantiated. There are indications that aminolysis of polycarbonate by milk and ethanolysis of polycarbonate by 50% ethanol might take place under relevant test conditions.

The relatively few migration data following the test conditions of European food contact material legislation, comply with the specific migration limit. Two test conditions were identified that reflect real use and exposure, and might cause higher release of BPA compared to the test conditions of European food contact material legislation. Further detailed studies are necessary to verify whether these two exposure scenarios are more severe.     

Carbon coating with combined super-hydrophobic and self-lubricating properties on titanium silicon carbide

Carbon coating on Ti₃SiC₂ with combined super-hydrophobic and self-lubricating properties was synthesized by chlorination at 1000 °C followed by modification of the CF₃(CF₂)₅CH₂CH₂SiCl₃ film. Raman spectroscopy confirmed the conversion from Ti₃SiC₂ to highly graphitized carbon coating. Scanning electron microscopy observation showed a highly porous microstructure of graphite flakes on the coating surface. The porous structure as well as organic film on carbon coating endowed the surface with super-hydrophobic property. Because of chemical inertia of the carbon coating and the modifier, the super-hydrophobic surface was very stable under various environments. Carbon coating was a good solid lubricant and greatly reduced friction coefficient of Ti₃SiC₂ sliding against Si₃N₄, which was important for Ti₃SiC₂ used as engineering material.     

Verification of RANS solvers with manufactured solutions

This paper discusses code verification of Reynolds-Averaged Navier Stokes (RANS) solvers with the method of manufactured solutions (MMS). Examples of manufactured solutions (MSs) for a two-dimensional, steady, wall-bounded, incompressible, turbulent flow are presented including the specification of the turbulence quantities incorporated in several popular eddy-viscosity turbulence models. A wall-function approach for the MMS is also described. The flexiblity and usefulness of the MS is illustrated with calculations performed in three different exercises: the calculation of the flow field using the manufactured eddy-viscosity; the calculation of the eddy-viscosity using the manufactured velocity field; the calculation of the complete flow field coupling flow and turbulence variables. The results show that the numerical performance of the flow solvers is model dependent and that the solution of the complete problem may exhibit different orders of accuracy than in the exercises with no coupling between the flow and turbulence variables.