A Prototype laser forming system

A non-contact laser forming (LF) demonstrator system was developed to demonstrate the process on a large primitive shape. The research that led to this development is described in this article. A fundamental study was carried out which examined the effects of laser-forming parameters on tokens of an aluminium and a titanium alloy. Energy, geometrical and metallurgical influences were investigated and are summarised here. Results of the study showed that LF of these aerospace materials is possible using a large operating envelope of laser-processing parameters. A range of metallurgical effects resulted on the titanium alloy and these are traced here. Depending on how the energy input was supplied to the plate surface, various geometrical effects resulted. These effects are discussed. Using the knowledge gathered from the fundamental study, a prototype LF system was built. The components of the system and the forming of a primitive shape on it are discussed. Conclusions from the study indicate that the future work lies in the development of the demonstrator for primitive 3-D shapes and the integration of a knowledge-based system.     

Ruthenium-catalyzed ionic hydrogenation of iminium cations. Scope and mechanism

Catalysis by CpRu(P-P)H (where P-P is a chelating diphosphine) of the ionic hydrogenation of an iminium cation inolves (1) the transfer of H(-) to form an amine, (2) the coordination of H(2) to the resulting Ru cation, and (3) the transfer of H(+) from the coordinated dihydrogen to the amine formed in (1). With CpRu(dppe)H the principal Ru species during catalysis remains the hydride complex, and H(2) pressure has no effect on either the ee or the turnover frequency. Step (1), H(-) transfer, can be carried out stoichiometrically if the H(2) is replaced by a coordinating solvent. A methyl substituent on the Cp ring decreases the H(-) transfer rate and the turnover frequency slightly. Electron-donating substituents on the phosphine increase the H(-) transfer rate and increase the turnover frequency up to a point: eventually the hydride ligand (i.e., the one in CpRu(dmpe)H) becomes sufficiently basic to deprotonate the iminium cation to the corresponding enamine, and this pre-equilibrium competes with H(-) transfer. Ionic hydrogenation of enamines is possible when a Ru(H(2)) cation (i.e., [CpRu(dppm)(eta(2)-H(2))](+)) is used as the catalyst and the enamine is more basic than the product amine. Ionic hydrogenation of an alpha,beta-unsaturated iminium cation saturates both the C=C and the C=N bonds. A C=N bond is more reactive toward ionic hydrogenation than a C=C one, but in some cases (i.e., CH=CH(2)) the latter may compete with H(2) for a coordination site and decrease the turnover frequency.     

Bioorthogonal chemical tagging of protein cholesterylation in living cells

We report the first chemical probe for bioorthogonal chemical tagging of post-translationally cholesterylated proteins with an azide in living cells. This enables rapid multiplexed fluorescence detection and affinity labelling of protein cholesterylation, as exemplified by Sonic hedgehog protein, opening up new approaches for the de novo identification of cholesterylated proteins.     

The electrochemical behaviour of tris(N,N-disubstituted dithiocarbamato) complexes of ruthenium(III) in dimethylsulphoxide

The reduction at the mercury electrode of a series of ruthenium(III) dithiocarbamates in dimethylsulphoxide (DMSO) has been investigated using D.C. A.C. polarography, chronoamperometry, coulometry (controlled potential electrolysis) and cyclic voltammetry. Tris(N,N-disubstituted dithiocarbamato) complexes of ruthenium exhibit two one-electron polarographic waves in the potential range 0.00 to 2.20 volt relative to Ag/AgClO₄ (DMSO) reference electrode. The first reduction, at approximately — 0.950 volt, is quasi-reversible. The [Ru(II) (dAdtc)₃]⁻ complexes resulting from this reduction are susceptible to dissociation, releasing the free dialkyldithiocarbamate anion.     

FK-multiplier spaces

In 1992 Grosse-Erdmann posed the problem of characterizing
those FK-spaces containing the finitely nonzero sequences whose -duals are themselves FK. Here we consider the more general problem of characterizing FK-spaces containing the finitely nonzero sequences with the property that the multipliers into a BK-sum space admit an FK-topology.

     

The determination of palladium by atomic absorption spectroscopy

A commercial atomic absorption apectrophotometer was used without modification to establish the most suitable operating, conditions for the determination of palladium. A study of the effect of organic solvents miscible with water, and of acids was then carried out. In general, organic solvents led to increased sensitivity. With a complex of palladium, Pd(py)₂Cl₂, in 50% ethanol, the sensitivity was also enhanced and, with a hexone solution of the complex, Pd(py)₂(SCN)₂, amounts of palladium below 2 p.p.m. could be determined.     

The Microchemistry of the platinum metals

Summary A method is outlined for the separation and determination of small amounts of osmium, iridium and platinum. Osmium and platinum are determined colorimetrically, and iridium is determined by titration. The procedure gives reproducible results, and provides a convenient method for the determination of each of the elements.

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Zusammenfassung Eine Methode zur Trennung und Bestimmung kleiner Mengen Osmium, Iridium und Platin wurde beschrieben. Osmium und Platin werden kolorimetrisch bestimmt, Iridium maßanalytisch. Das Verfahren gibt reproduzierbare Ergebnisse und eignet sich zur Bestimmung jedes der genannten Elemente.

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Résumé On recommande une méthode pour la séparation et le dosage de petites quantités d'osmium, d'iridium et de platine. On dose par colorimétrie l'osmium et le platine et par titrage l'iridium. Le procédé donne des résultats reproductibles et fournit une méthode appropriée pour le dosage de chacun des éléments.

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In honour of the 70th birthday ofFritz Feigl.