Multiscale modelling and structural characterization of Fe enriched Al alloy

Scale dependent modelling of inelastic behaviour of rapidly solidified Al Fe enriched powders subjected to cold compaction and subsequent hot extrusion is provided. The alloy is considered as a ductile “in situ” composite. The average elastic end plastic properties of bulk material depend on density evolution, temperature and matrix hardening. The model assumptions are based on microstructural observations. The microstructure characterization was carried out using Scanning Electro Microscopy (SEM) and Energy Dispersive X–ray (EDX) analysis. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling of a combined process of thermomechanical treatment of 304 stainless steel

Grain refinement due to phase transformation is an effective method for improving the mechanical properties of steel. An approach is proposed in the present work based on the FEM, for numerical simulation of the microstructure evolution. Grain refinement in 304 stainless steel is considered. Coupling of the thermoplastic deformation with microstructure evolution is realized. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A CD-Spectroscopic Alternative to Methylation Analysis of Oligosaccharides: Reference Spectra for Identification of Chromophoric Glycopyranoside Derivatives

A microscale method for identifying the monosaccharide units and their linkages in oligosaccharides is presented. Sugar components are identified by UV and CD spectroscopy of chromophoric degradation products. CD spectral data for approximately 150 different glycopyranoside components are provided for use as reference spectra in the identification of unknown derivatives. Procedures for the conversion of oligosaccharides to monosaccharide subunits bearing 4-bromobenzoate and 4-methoxycinnamate chromophores have been developed based on acetolysis/bromination reactions for glycosidic cleavage of per (bromobenzoylated) oligosaccharides. The method offers an alternative means to conventional methylation analysis of oligosaccharides.     

Identification and quantification of lignans in wheat bran by gas chromatography-electron capture detection

Whole grain cereals are an important source of bioavailable lignans, the group of compounds with potential anti-cancerogenic, antioxidant, anti-proliferative, pro-apoptotic, and antiangiogenic properties. The aim of this work was to develop a sensitive method for determination of wheat bran lignans. The analysis of lignans secoisolariciresinol, hydroxymatairesinol, lariciresinol, matairesinol, pinoresinol, syringaresinol is based on derivatization with pentafluoropropionic anhydride (PFPA) and gas chromatography-electron capture detection (GC-ECD), using styrene glycol as internal standard. To our knowledge, this is the first time that EC detection has been used for lignan analysis. The results show that the technique is reproducible and sensitive enough for detecting lignans in wheat at parts-per-billion (ppb) levels, except for hydroxymatairesinol. The method developed showed good recovery (85-105%) and precision (4-20%) for five types of lignans and thus represents a simpler and more affordable alternative to state-of-the-art wheat lignan liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis.     

Fragmentation and erosion of two-dimensional aggregates in shear flow

We consider single two-dimensional aggregates containing glass particles trapped at a water/oil or water/air interface. Two modes for aggregate break-up are observed: break-up by fragmentation into a few parts and break-up by erosion of single particles. We have studied the critical shear rate for these modes as a function of the aggregate size. Two different particle sizes were used. The smaller particles, with a radius of 65 microm, form aggregates that break up predominantly by erosion at a shear rate between 0.5 and 0.7 s(-1). This value hardly depends on the size of the aggregates. The larger particles, with a radius of 115 microm, form aggregates that break by erosion or by fragmentation. In both modes, the critical shear rate again depends only weakly on the size of the aggregates and ranges between 1.6 and 2.2 s(-1). Also the structural changes inside the aggregate before break-up were studied. The aggregate behavior at the water/air and water/oil interfaces is quite similar. The critical shear rate for break up was also modeled. The model shows in both modes a weak dependence of the critical shear rate on the aggregate size, which is consistent with the experimental observations. The kinetics of the erosion process was also modeled and compared with the experimentally obtained time dependence of the aggregate size. The differences in the large and small particle systems can be attributed to the occurrence of friction forces between the particles, which one expects to be much larger for the large particle system, due to the stronger two-particle interaction.