Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: a new luminescent uranyl benzoate specie.
Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3](-) which is highly luminescent. In particular, three sharp bands at 431, 443, 461nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68μs which is much more compared to the lifetime of uncomplexed uranyl (20μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3](-) specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed.
Direct and fast uranium determination in zirconium by time-resolved laser-induced fluorescence spectrometry
Abstract Fast and direct determination of uranium in zirconium is required for nuclear process control. Time-resolved laser-induced fluorescence spectrometry is a very selective and sensitive method that has been largely used for uranium(VI) analysis in the nuclear fuel cycle. Due to the very low quenching constant of zirconium, the uranyl fluorescence signal is weakly affected by this element. By using direct fluorescence signal measurement, the uranium concentration is obtained in less than a minute and the limit of detection is close to 10 ng 1 −1 which corresponds to 1 ng g −1 relative to the zirconium matrix. Moreover, the zirconium dissolution medium (nitric/hydrofluoric acid) is complexing enough to allow direct measurement with no use of other complexing reagent. Such procedure can also be used for uranium determination in hafnium.
Computational fluid dynamics as a development tool for rotary blood pumps.
Computational fluid dynamics (CFD) is beginning to significantly impact the development of biomedical devices, in particular rotary cardiac assist devices. The University of Pittsburgh's McGowan Center for Artificial Organ Development has extensively used CFD as the primary tool to analyze and design a novel axial flow blood pump having a magnetically suspended rotor. The blood-contacting surfaces of the pump were developed using a design strategy based on CFD that involved closely coupling a Navier-Stokes solver to a parameterized geometry modeler and advanced mesh movement techniques. CFD-based blood damage models for shear-induced hemolysis as well as surrogate functions describing thrombosis potential were employed to help guide design improvements. This CFD-based design approach resulted in the timely development of a pump subjected to multiple geometric refinements without building expensive physical prototypes for each design iteration. A physical prototype of the final improved pump was fabricated and experimentally analyzed using particle imaging flow visualization. The CFD predicted results correlated well with the experimental data including pressure-flow (H-Q) performance and specific flow field features. It is estimated that the present CFD-based design approach shortened the overall design time frame from an order of years to months.