Orthogonal-gradings on $$H^*$$-algebras

We study set-gradings on proper \(H^*\)-algebras A, which are compatible with the involution and the inner product of A, that will be called orthogonal-gradings. If A is an arbitrary \(H^*\)-algebra with a fine grading, we obtain a (fine) orthogonal-graded version of the main structure theorem for proper arbitrary \(H^*\)-algebras. If A is associative, we show that any fine orthogonal-grading is either a group-grading or a (non-group grading) Peirce decomposition of A respect to a family of orthogonal projections. If A is alternative, we prove that any fine orthogonal-grading is either a fine orthogonal-grading of a (proper) associative \(H^*\)-algebra, or a \({\mathbb Z}_2^3\)-grading of the complex octonions \({\mathbb O}\) or a non-group grading which is a refinement of the Peirce decomposition of \({\mathbb O}\) respect to its family of orthogonal projections. Finally, we also show that any orthogonal-grading on the real octonion division algebra is necessarily a group-grading.     

Photoproduction of ϱ0 and ω on hydrogen at photon energies of 20 to 70 GeV

We present results on photoproduction of ?⁰ and ω in the reactions γp→π⁺π^?p and γp→π⁺π^?π⁰p by tagged photons in the energy ranges 20 to 70 GeV and 20 to 45 GeV, respectively. The production of the ?⁰ shows dominantly the characteristics of a diffractive process with respect to the E_γ and t dependence of the cross section and the spin density matrix. The ?⁰ photoproduction yields on average over the photon energy range a total cross section of σ(γp→?⁰p) = 9.4±0.1 μb with an additional systematic error of ±1 μb, and average slope parameters of the t distribution dσ/dt≈exp(?b|t| + ct²), of b=9.1±0.1 GeV^?2 and c = 3.1 ±±0.2 GeV^?4. The shape of the ?⁰ peak in the π⁺π^? invariant spectra shows a skewing similar to that observed at lower energies. The photoproduction of ω is also consistent with a diffractive process and has a cross section of σ(γp→ωp) = 1.2± 0.1 μb with an additional systematic error of ±0.2 μb. The average slope parameters of the t distribution are b=8.3 ± 1.3 GeV^?2 and c = 3.4±2.6 GeV^?4.     

Trace-level determination of 1,4-dioxane in water by isotopic dilution GC and GC-MS

The volatile and polar solvent 1,4-dioxane has recently been reported as a contaminant of ground and surface waters, establishing the need to determine this substance in drinking water. This investigation established that 1,4-dioxane can be determined in water by various techniques including direct aqueous injection (DAI) gas chromatography (GC) and purge and trap GC-mass spectrometry (MS). Purge and trap GC-MS is limited by 1,4-dioxane's poor purge efficiency, resulting in detection limits up to 100 times greater than the efficiently purged volatile organic compounds. To attain the sensitivity required for drinking water monitoring, a method based on continuous liquid-liquid extraction with dichloromethane was developed. Isotope dilution was more accurate and reproducible than quantification with external standards, and the improvement in precision led to a lower method detection limit, 0.2 microgram L-1, using a quadrupole ion trap instrument in the electron ionization mode. Isotope dilution accuracy approached 100% in ppb determinations. Isotopic dilution quantification was also possible using a non-selective GC detector owing to the high efficiency of capillary GC columns that resolve the deuterium-labeled solvent from the natural isotopes.     

The synthesis of 3,5-dimethylpyrazol-1-yl-vl-v-triazolo[4,5-d]pyridazines and substituted 3,5-dimethylpyrazol-1 -ylimidazo[4,5-d]pyridazines

The synthesis of 4-(3,5-dimethylpyrazol-1-yl)-v-triazolo[4,5-d]pyridazine, 4-(3,5-dimethylpyrazol-1-yl)imid-azo[4,5-d]pyridazine and several S-substituted derivatives of 4-(3,5-dimethylpyrazol-1-yl)imidazo[4,5-d]pyrid-azine-2-thiol is reported. These syntheses were carried out to provide a variety of interesting compounds for biological screening.     

Enantioselective Friedel-Crafts alkylation reactions catalyzed by a chiral nonracemic C2-symmetric 2,2'-bipyridyl copper(II) complex

Enantioselective Friedel-Crafts alkylation reactions of a series of substituted indoles with methyl trifluoropyruvate, catalyzed by a chiral nonracemic C(2)-symmetric 2,2'-bipyridyl copper(II) triflate complex, are described. The corresponding 3,3,3-trifluoro-2-hydroxy-2-indole-3-yl-propionic acid methyl esters were formed in good yield and in high enantiomeric excess (up to 90%). This is the first report of the use of a chiral nonracemic 2,2'-bipyridyl ligand in catalytic and enantioselective Friedel-Crafts alkylation reactions. The structural characterization of a copper(II) chloride complex of the chiral 2,2'-bipyridyl ligand by X-ray crystallography is also presented. [reaction: see text]     

Orthopalladated and -platinated bulky triarylphosphite complexes: synthesis,reactivity and application as high-activity catalysts for Suzuki and Stille coupling reactions

Bulky triarylphosphite ligands undergo facile orthometallation reactions with palladium and platinum precursors. The crystal structure of an example of the resultant palladacycles has been determined. The reactivity of some of the metallacycles with HCl, monodentate and bidentate phosphines and sodium diethyldithiocarbamate has been investigated, and the crystal structure of a diethyldithiocarbamate adduct of a palladacycle is presented. The palladacyclic complexes prove to be extremely active catalysts for the Suzuki coupling of aryl bromides with aryl boronic acids. They can also be used as catalysts for the coupling of alkylboronic acids. Meanwhile di- and trialkyl phosphine adducts of one of the palladacycles shows very high activity in the Suzuki coupling of aryl chlorides and can also be used to good effect for the Stille coupling of these substrates. The role of the phosphite ligand in the Suzuki coupling of aryl chlorides seems to be one of increasing catalyst longevity by stabilisation of the Pd(0) resting state.