Assay of vecuronium in plasma using solid-phase extraction, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection

An assay has been developed and validated for the routine monitoring of vecuronium in plasma. It consists of solid-phase extraction using C18 disposables as sample pre-treatment, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection. The fluorescent anion 9,10-dimethoxyanthracene-2-sulphonate (DAS) is used as the counter ion. The detection limit is ca. 5 ng/ml in plasma with a signal-to-noise ratio of 10. The assay is also applicable for monitoring vecuronium and its potential metabolites in other biological media, e.g., urine, bile and tissue (liver, kidney) homogenates.     

Bistability in a hyperchaotic system with a line equilibrium

A hyperchaotic system with an infinite line of equilibrium points is described. A criterion is proposed for quantifying the hyperchaos, and the position in the three-dimensional parameter space where the hyperchaos is largest is determined. In the vicinity of this point, different dynamics are observed including periodicity, quasi-periodicity, chaos, and hyperchaos. Under some conditions, the system has a unique bistable behavior, characterized by a symmetric pair of coexisting limit cycles that undergo period doubling, forming a symmetric pair of strange attractors that merge into a single symmetric chaotic attractor that then becomes hyperchaotic. The system was implemented as an electronic circuit whose behavior confirms the numerical predictions.     

Multiaxial deformation of polyethylene and polyethylene/clay nanocomposites: in situ synchrotron small angle and wide angle X‐ray scattering study

A unique in situ multiaxial deformation device has been designed and built specifically for simultaneous synchrotron small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering (WAXS) measurements. SAXS and WAXS patterns of high‐density polyethylene (HDPE) and HDPE/clay nanocomposites were measured in real time during in situ multiaxial deformation at room temperature and at 55 °C. It was observed that the morphological evolution of polyethylene is affected by the existence of clay platelets as well as the deformation temperature and strain rate. Martensitic transformation of orthorhombic into monoclinic crystal phases was observed under strain in HDPE, which is delayed and hindered in the presence of clay nanoplatelets. From the SAXS measurements, it was observed that the thickness of the interlamellar amorphous region increased with increasing strain, which is due to elongation of the amorphous chains. The increase in amorphous layer thickness is slightly higher for the nanocomposites compared to the neat polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Some Isoperimetric Inequalities in Electrochemistry and Hele Shaw Flows

Isoperimetric inequalities are applied to a moving-boundaryproblem for doubly-connected domains. This problem occurs forexample in electrochemistry, in which case the domains in questionare the electrolyte of an electrolytic cell. The two electrodessurrounding the electrolyte are assumed to grow or dissolve,at different rates in general, by electrochemical reaction.We obtain optimal estimates showing, for example, that the leastchange in volume of each electrode always occurs in sphericalsymmetry.