TiO2 nanotubes as recyclable catalyst for efficient photocatalytic degradation of indigo carmine dye

TiO₂ nanotubes have been synthesized in a hydrothermal system. The nanotubes were characterized by scanning electronic microscopy (SEM), FT-Raman spectroscopy and surface charge density by surface area analyzer. These nanocatalysts were applied to photocatalyse indigo carmine dye degradation. Photodegradation ability of TiO₂ nanotubes was compared to TiO₂ anatase photoactivity. Indigo carmine dye was completely degraded at 60 and 110 min of reaction catalysed by TiO₂ nanotubes and TiO₂ anatase, respectively. TiO₂ nanotubes presented high photodegradation activity at pH 2 and TiO₂ anatase at pH 4. TiO₂ nanotubes were easily recycled whereas the reuse of TiO₂ anatase was not effective. Nanotubes maintained 90% of activity after 10 catalytic cycles and TiO₂ anatase presented only 10% of its activity after 10 cycles.     

An alternative and fast method for determination of glyphosate and aminomethylphosphonic acid (AMPA) residues in soybean using liquid chromatography coupled with tandem mass spectrometry

A simple and specific method using reversed‐phase liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) was investigated, which allowed the determination of residues of glyphosate and its metabolite, aminomethylphosphonic acid (AMPA), in soybean samples. An aqueous extraction with liquid‐liquid partition followed by protein precipitation was performed before the LC/MS/MS determination. The quantitation of glyphosate and AMPA was performed in positive and negative ESI mode, respectively, using the multiple reaction monitoring (MRM) mode with three transitions for each analyte to enhance the specificity of the method and avoid false positives. The methodology reported in this work is capable of detecting residues of glyphosate and AMPA in soybean samples with limits of quantification of 0.30 and 0.34 mg kg^?1, respectively. This alternative method has throughput advantages such as simpler sample preparation and faster chromatographic analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

Chiral bromine–lithium exchange catalyzed by diamines

Different classes of prochiral polyhalide compounds have been tested in a chiral bromine–lithium exchange in the presence of different diamines with enantiomeric excesses of up to 63%.     

Hexagonal ammonium zinc ­phosphate, (NH4)ZnPO4, at 10 K

The title compound, (NH₄)ZnPO₄–HEX, is built up from a three‐dimensional network of ZnO₄ and PO₄ tetrahedra [d_av(Zn—O) = 1.9400 (7) Å and d_av(P—O) = 1.5396 (7) Å], fused together via Zn—O—P links [θ_av = 133.47 (4)°]. An undisordered linear Zn—O—P bond occurs (all three atoms lie on a threefold axis). Extra‐framework NH₄⁺ cations, which interact with the [ZnPO₄]^? framework by hydrogen bonds, complete the crystal structure.     

A Change of Coordinates on the Large Phase Space¶of Quantum Cohomology

The Gromov–Witten invariants of a smooth, projective variety V, when twisted by the tautological classes on the moduli space of stable maps, give rise to a family of cohomological field theories and endow the base of the family with coordinates. We prove that the potential functions associated to the tautological ψ classes (the large phase space) and the κ classes are related by a change of coordinates which generalizes a change of basis on the ring of symmetric functions. Our result is a generalization of the work of Manin–Zograf who studied the case where V is a point. We utilize this change of variables to derive the topological recursion relations associated to the κ classes from those associated to the ψ classes. Received: 2 August 1999 / Accepted: 30 September 2000     

Characterisation of cw Nd : YAG laser keyhole dynamics

The paper concerns laser–matter interaction characterisation. In this work, we use a rapid CCD camera located coaxially to the laser beam and we compare recorded images with those obtained by numerical modelling. Because images are difficult to understand, we compute thermal radiation emitted by a keyhole of fixed geometry and we adjust it trying to approach the camera record. The modelling treats radiative heat transfer within the keyhole and determines the sensor illumination map. By adjusting the geometrical characteristics of the hole, we seek to obtain the image that corresponds as well as possible to the realised experiment. Results are compared with other experimental methods simultaneously performed plume characterisation with an electric probe and spectrometric analysis. They show the existence of two distinct behaviours of the keyhole: a pseudo-steady state associated with regular and pseudo-constant keyhole shapes, low frequencies of electric current in the plume, and generally good welding results, and a highly dynamic mode associated with irregular and rapidly varying keyhole shapes, high frequencies in the plume current and generally poor welding results.