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Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

A minimization principle for finite strain plasticity: incremental objectivity and immediate implementation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2002
Eric Lorentz
Abstract A finite strain plasticity formulation is proposed which meets several requirements that often appear contradictory. On a physical ground, it is based on a multiplicative split of the deformation, hyperelasticity for the reversible part of the behaviour and the maximal dissipation principle to define the evolution laws. On a numerical ground, it is incrementally objective and the integration over a time increment can be expressed as a minimization problem, a proper framework to examine the questions of existence and uniqueness of the solutions. Last but not least, the implementation is immediate since it relies on the same equations for finite and infinitesimal transformations. Finally, the formulationis applied to von Mises plasticity with isotropic linear hardening and introduced in the finite element software Code_Aster®. The numerical computation of a cantilever beam shows that it leads to results in good agreement with those obtain with common approaches. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Neurulation in the cranial region , normal and abnormal

JOURNAL OF ANATOMY, Issue 5 2005
Andrew J. Copp
Abstract Cranial neurulation is the embryonic process responsible for formation of the brain primordium. In the mouse embryo, cranial neurulation is a piecemeal process with several initiation sites and two neuropores. Variation in the pattern of cranial neurulation occurs in different mouse strains, and a simpler version of this morphogenetic scheme has been described in human embryos. Exencephaly is more common in females than in males, an unexplained phenomenon seen in both mice and humans. As the cranial neural tube closes, a critical morphogenetic event is the formation of dorsolateral bending points near the neural fold tips, which enables subsequent midline fusion of the neural folds. Many mutant and gene-targeted mouse strains develop cranial neural tube defects, and analysis of the underlying molecular defects identifies several requirements for normal dorsolateral bending. These include a functional actin cytoskeleton, emigration of the cranial neural crest, spatio-temporally regulated apoptosis, and a balance between cell proliferation and the onset of neuronal differentiation. A small number of mouse mutants exhibit craniorachischisis, a combined brain and spine neurulation defect. Recent studies show that disturbance of a single molecular signalling cascade, the planar cell polarity pathway, is implicated in mutants with this defect. [source]

Highly automated and fast determination of raffinose family oligosaccharides in Lupinus seeds using pressurized liquid extraction and high-performance anion-exchange chromatography with pulsed amperometric detection

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2008
David Bansleben
Abstract BACKGROUND: Taking into account several requirements for the determination of raffinose family oligosaccharides (RFOs) from Lupinus seeds,e.g., conducting plant breeding projects or food product development,a reasonable combination of efficient automated sample preparation and reliable analysis need to be developed and validated. RESULTS: In this regard pressurized liquid extraction was applied to extract the RFOs from ground and defatted lupin flour. Compared to many other publications, no further pretreatment, such as protein precipitation, was necessary to obtain satisfactory results applying ion chromatography with pulsed amperometric detection. The oligosaccharide content for the examined Lupinus albus samples were in the range 5.19,9.25 g kg,1 and for Lupinus angustifolius RFOs 3.49,4.75 g kg,1. Stachyose has always been the main component followed by raffinose and verbascose. CONCLUSION: The developed sample preparation and analytical method is suited to quantify raffinose, stachyose, verbascose and the disaccharide sucrose and, owing to a high degree of automation for sample preparation and relatively short analysis times by pretty peak separation, particularly high sample numbers can be accomplished. Copyright © 2008 Society of Chemical Industry [source]

Ruthenium(II) Complexes for Two-Photon Absorption-Based Optical Power Limiting

CHEMPHYSCHEM, Issue 11 2008
Camille Girardot Dr.
Long-lived excitation: Novel bifluorene-substituted 1,10-phenanthroline-based RuII coordination complexes are presented (see picture). They fulfil several requirements for optimized optical power limiting in the visible-NIR, as they are stable, soluble and transparent at low laser fluences. The two-photon absorption of these complexes are strongly related to those of the ligand. [source]