Analytical energy surfaces for the collinear H+H2 and Li+H2 exchange reactions

A simple four-parameter function is shown to possess adequate flexibility to fit the H + H₂ →H₂ + H and Li + H₂ → LiH + H exchange reaction energy surfaces to good accuracy along the reaction paths.     

Synthesis of 5-Oxo and 7-Oxopyrido[2,3-d]pyrimidines

The synthesis of 4-amino-2-methylthio-5-oxopyrido[2,3-d]pyrimidine 4 and its isomer, 4-amino-2-methyl-thio-7-oxopyrido[2,3-d]pyrimidine 6 is described. The regiochemistry of the reaction of 4,6-diamino-2-methyl-thiopyrimidine 9 and diethyl ethoxymethylene malonate 12 is discussed.     

Luminescence quenching of a phosphorescent conjugated polyelectrolyte

The photophysical and luminescence quenching properties of a platinum(II) acetylide-based conjugated polyelectrolyte, Pt-p, which features carboxylic acid solubilizing groups are reported. The Pt-acetylide polymer is water soluble, and it exhibits phosphorescence from a triplet pi,pi exciton based on the conjugated backbone. The phosphorescence from Pt-p is quenched by viologens with different charges (MV(+), MV(2+), and MV(4+)), and in each case the quenching is dominated by a dynamic (diffusional) mechanism. Comparison of the Stern-Volmer quenching properties of Pt-p with those of a structurally analogous fluorescent organic polyelectrolyte leads to the conclusion that the amplified quenching effect, which is commonly observed for fluorescent conjugated polyelectrolytes, is not important for the platinum acetylide phosphorescent conjugated polyelectrolyte.     

Applications of capillary gas chromatography in routine toxicological analyses

Capillary columns offer the toxicologist several advantages over packed columns. We have presented a highly reproducible screening procedure based on the retention index system and have shown the use of capillary columns for routine quantitation. We are currently expanding the use of these columns in our laboratory and predict that they will be in routine use by most toxicologists in the near future.     

Two-dimensional high resolution GLC environmental analysis,preliminary results

Summary The current status of gas chromatographic procedures and instrumentation for the analysis of volatile environmental contaminants is discussed. Design features of gas chromatographic systems, capable of transferring portions of eluting compounds from one gas chromatographic column into another are also discussed. A prototype two-dimensional gas chromatograph has been built and tested. The system is composed of two separate gas chroamtographs, which are joined by a common heated interface. A combination of off-line valves and restrictors (Deans' switches) serves to change carrier gas flow directions. Compounds selected for cutting are transferred to the second gas chromatograph and held in an intermediate trap. The effluents from the second column are detected by FID/ECD, operated in parallel. Important parameters which effect sample transfer between the systems have been studied to serve as basis for a semiautomated instrument to be built. Some applications with synthetic mixtures are demonstrated.     

An automated system for preconcentration/matrix-removal followed by ICP-MS determination of organic phosphorus in oil production water

Scale inhibitors based on phosphinepolycarboxylic acid (PPCA) have been successfully used in offshore oil production for preventing deposition of barium and strontium sulfates. A system was developed for the automated pretreatment of PPCA-containing water samples, followed on-line or off-line by phosphorus determination using ICP mass spectrometry. During pretreatment, the previously acidified inhibitor solution is adsorbed on a C18-reversed phase column and then eluted with 0.025 mol l⁻¹ borate solution. Using a 3.5-ml sample volume, analytical frequency in the on-line mode is about 9 samples per hour and 17 in off-line operation. Detection limit of phosphorus in the borate solution was 0.20 μg l⁻¹, using a crossflow nebulizer and a Ryton® spray chamber. Recoveries were, typically, in the range of 90% to 100% and repeatability about 5%. The method has been applied for monitoring inhibitor concentrations during laboratory and field squeeze tests.     

Comments on the symmetry structure of bi-Hamiltonian systems

The algebraic structure of exactly solvable equations is reviewed and results are reported which 1) establish that isospectral eigenvalue problems yield hereditary symmetries for bi-Hamiltonian equations and 2) show that if both an equation and its modified equation have known Hamiltonian formulations then their hereditary symmetries and bi-Hamiltonian formulations are readily obtained via their Miura transformation.Invited talk presented at the International Symposium Selected Topics in Quantum Field Theory and Mathematical Physics, Bechyn, Czechoslovakia, June 14–19, 1981.     

Systems of ordinary differential equations with nonlinear superposition principles

This work is concerned with the derivation of superposition rules which express the general solution of ordinary differential equations.

$\text{x}\text{?}\text{= η(x,t).}\text{(x, η ?}\text{R}{}^{\mathrm{n}}\text{, t ?}\text{R}\text{)}$

. in terms of a finite number of particular solutions. The point of departure is Lie's criterion according to which such a rule exists if and only if the vector fields η(x,t). ? generate a finite dimensional Lie algebra. We provide three different constructive methods for deriving superposition rules and apply them to systems of coupled Riccati equations of the projective and conformal types based, respectively, on the Lie algebra sl(n + 1, R) and o(p + 1, n ? p + 1).     

Identification of the phenothiazines by gas chromatography of their pyrolysis products

Summary Nineteen phenothiazines were pyrolyzed and their products analyzed gas chromatographically. The pyrolysis products were compared with those obtained from a similar study of the barbiturates. Tentative identifications have been made of three pyrolysis products. The pyrolyzates of the various phenothiazine derivatives yield gas chromatographie patterns which differentiate among them.

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Zusammenfassung Die Pyrolyseprodukte von 19 Phenothiazinen wurden gaschromato-graphisch analysiert und mit jenen verglichen, die bei einer analogen Untersuchung von Barbituraten erhalten worden waren. Die Identifizierung von drei Pyrolyseprodukten wurde versucht. Die Pyrolysate der verschiedenen Phenothiazinderivate lassen sich gaschromatographisch unterscheiden.

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Résumé On a effectué la pyrolyse de dix-neuf phénothiazines et analysé les produits résultants par chromatographie en phase gazeuse. On a comparé les résultats — ceux obtenus au cours d'une étude semblable sur les barbiturates. On a tenté d'identifier trois produits de pyrolyse. Les produits de pyrolyse de plusieurs dérivé de la phénothiazine donnent en chromatographie en phase gazeuse des enregistrements qui permettent de les différencier.

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Dedicated to Prof.A. A. Benedetti- Pichler on the occasion of his 70th birthday.