The modular analytical procedure and validation approach and the units of measurement for genetically modified materials in foods and feeds

Food and feed analysts are confronted with a number of common problems, irrespective of the analytical target. The analytical procedure can be described as a series of successive steps: sampling, sample processing, analyte extraction, and ending, finally, in interpretation of an analytical result produced with, e.g., real-time polymerase chain reaction. The final analytical result is dependent on proper method selection and execution and is only valid if valid methods (modules) are used throughout the analytical procedure. The final step is easy to validate-the measurement uncertainty added from this step is relatively limited and can be estimated with a high degree of precision. In contrast, the front-end sampling and processing steps have not evolved much, and the corresponding methods are rarely or never experimentally validated according to internationally harmonized protocols. In this paper, we outlined a strategy for modular validation of the entire analytical procedure, using an upstream validation approach, illustrated with methods for genetically modified materials that may partially apply also to other areas of food and feed analyses. We have also discussed some implications and consequences of this approach in relation to reference materials, measurement units, and thresholds for labelling and enforcement, and for application of the validated methods (modules) in routine food and feed analysis.     

Giant fluctuations of superconducting order parameter in ferromagnet-superconductor single-electron transistors

Spin dependent transport in a ferromagnet-superconductor single-electron transistor is studied theoretically taking into account spin accumulation, spin relaxation, gap suppression, and charging effects. A strong dependence of the gap on the magnetic state of the electrodes is found, which gives rise to a magnetoresistance of up to 100%. We predict that fluctuations of the spin accumulation can play such an important role as to cause the island to fluctuate between the superconducting and normal states. Furthermore, the device exhibits a nearly complete gate-controlled spin-valve effect.     

Magnetization noise in magnetoelectronic nanostructures

By scattering theory we show that spin current noise in normal electric conductors in contact with nanoscale ferromagnets increases the magnetization noise by means of a fluctuating spin-transfer torque. Johnson-Nyquist noise in the spin current is related to the increased Gilbert damping due to spin pumping, in accordance with the fluctuation-dissipation theorem. Spin current shot noise in the presence of an applied bias is the dominant contribution to the magnetization noise at low temperatures.     

Continuum theory of the volume effect caused by point defects in hexagonal media

The volume change caused by a point defect in the center of a spherical reference volume which is embedded into the infinite medium is calculated analytically for hexagonal crystal symmetry. Two new dimensionless coefficients which we call generalized Eshelby coefficients are introduced to describe the correction of volume change which appears if that reference volume has a free, unforced surface. These coefficients play a similar role for hexagonal crystals as the Eshelby factor in the isotropic medium does. It is shown that the influence of elastic anisotropy on the Eshelby coefficients is essentially determined by the closest elastic instabilities. In the limit of an isotropic medium these coefficients reduce to the well-known Eshelby factor.     

High energy resolvent estimates for Schrödinger operators in Besov spaces

Dedicated to Professor Shmuel Agmon     

Peptomers: A Versatile Approach for the Preparation of Diverse Combinatorial Peptidomimetic Bead Libraries

This report describes a versatile approach in thegeneration of peptidomimetic bead libraries. Themethod is based on the preparation of peptide–peptoidhybrids using the portioning–mixing procedure, whichgives diverse peptidomimetic bead libraries composedof peptides, peptoids and peptide–peptoid hybrids. Weterm these peptomers, from peptide–peptoidhybrid polymers. The synthesis of the peptomersis easily accomplished by adapting the peptoidsynthesis strategy, in which a primary amine reactswith bromoacetic acid, and we combine this methodologywith conventional peptide synthesis. The sequence ofthe active compound is deduced by conventionalmicrosequencing using Edman degradation chemistry,thus avoiding the synthesis of a coding structure orthe addition of molecular tags. We demonstrate theutility of the peptomer approach by the synthesis ofa bead library together with the identification ofnovel peptidomimetic ligands binding to themacromolecular targets streptavidin and the insulin receptor.     

Fluid Flow Across Capillary Heterogeneities,Experiments and Simulations

A comparative study of numerical modelling and laboratory experiments of two-phase immiscible displacements in a 33 cm × 10 × 3 cm thick cross-bedded reservoir model is reported. Dynamic two-dimensional fluid saturation development was obtained from experiments by use of a nuclear tracer imaging technique and compared to numerical predictions using a full-field black oil simulator.The laboratory cross-bedded reservoir model was a sandpack consisting of two strongly waterwet sands of different grain sizes, packed in sequential layers. The inlet and outlet sand consisted of low permeable, high capillary, sand while the central crosslayer with a dip angle of 30° was a high permeable, low capillary, sand. Results on moderate contrasts in permeability and capillary heterogeneities in the cross-bedded reservoir model at different mobility ratios and capillary number floods temporarily showed a bypass of oil, resulting in a prolonged two-phase production. The final remaining oil saturations, however, were as for isolated samples. Hence, permanently trapped oil was not observed.Simulations of waterfloods, using a commercial software package, displayed correct water breakthrough at low flow rate and unity viscosity ratio, but failed in predicting local saturation development in detail, probably due to numerical diffusion.The simulator was used to test several cases of heterogeneity contrasts, and influence from different relative permeability curves. Further, by altering the capillary pressure at the outlet, the end effects were proven important.