Escape from the unstable equilibrium in a random process with infinitely many interacting particles

We consider a one-dimensional version of the model introduced in Ref. l. At each site of Z there is a particle with spin ± 1. Particles move according to the Stirring Process and spins change according to the Glauber dynamics. In the hydrodynamical limit, with the stirring process suitably speeded up, the local magnetic densitym _t(r) is proven in Ref. 1 to satisfy the reaction-diffusion equation (*) $$\partial _t m_t (r) = \tfrac{1}{2}\partial _r^2 m_t (r) - V'(m_t )$$ \(V(m) = - \tfrac{1}{2}\alpha m^2 + \tfrac{1}{4}\beta m^4 \) ,α andβ being determined by the parameters of the Glauber dynamics. In the present paper we consider an initial state with zero magnetization,m ₀(r)=0. We then prove that at long times, before taking the hydrodynamical limit, the evolution departs from that predicted by (*) and that the microscopic state becomes a nontrivial mixture of states with different magnetizations.     

Homogeneous hydrogenation of ketones to alcohols with ruthenium complex catalysts

A number of ruthenium triphenylphosphine complexes catalyse the reduction of ketones to their corresponding alcohols in the presence of water. The most convenient catalyst precursors are carbonyl containing complexes which do not promote decarbonylation of the substrate. The hydrogenation of acetone with hydridochlorocarbonyltris(triphenylphosphine)ruthenium is first order with respect to the substrate concentration, the catalyst concentration, the hydrogen pressure and the water concentration. Turnover numbers up to 15,000 have been achieved with this catalyst. Other ketones are also reduced by RuHCl(CO)(PPh₃)₃ and the rate of the reaction is dependent on the nature of the substrate.     

k0-measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

Recommended k₀-factors and related nuclear data for use in (n, γ) activation analysis are given for 72 isotopes. In addition the basic nuclear constants and experimental parameters needed in the k₀ standardization method are reviewed. For convenient data reduction, computer programs were developed.     

INTRAMOLECULAR EXCIPLEX FORMATION IN Nα-ACETYL-1-PYRENYLALANYL-1-METHYLTRYPTOPHAN METHYLESTER

Abstract— The synthesis, absorption and emission properties of erythro (e) and threo (t) Na-acetyl-1-pyrenylalanyl-1-methyltryptophan methylester (APTE) are reported. From the dependency of the exciplex emission maximum on the solvent polarity, the exciplex dipole moment of erythro and threo APTE were calculated. The evolution of the ratio of the quantum yield of exciplex emission and the quantum yield of emission from the locally excited state is correlated with solvent polarity and with the tendency of the solvent to interact with the peptide chain through hydrogen bonding. It is shown that solvents, inert towards the peptide function, shift the equilibrium between the two ground state conformations towards C₇, in which an exciplex geometry can be reached. Hydrogen accepting solvents shift the conformational equilibrium towards C₅, which cannot form an exciplex directly within the lifetime of excited pyrene.     

5-vinylisoxazole

Cycloaddition of fulminic acid to 1-butyn-3-ol gave a mixture of 5-α-hydroxyethylisoxazole (I) and 4-α-hydroxyethylisoxazole (II) in the ratio 9:1. By the dehydration of 1, 5-vinylisoxazole (III) was obtained. Compound III has also been prepared by cyclization of 4-penten-2-ynal as well as its diethylacetal with hydroxylamine hydrochloride; in both instances no isomers have been obtained. Compound III spontaneously polymerizes even at room temperature yielding a polymer still containing isoxazole rings.     

Determination of betamethasone and triamcinolone acetonide by GC-NCI-MS in excreta of treated animals and development of a fast oxidation procedure for derivatisation of corticosteroids.

The use of corticosteroids in combination with other hormonal substances has long been known to result in increased mass gain with bovines. Practice has demonstrated, however, that even the single use of a glucocorticoid may result in growth promoting effects. In addition to the popular dexamethasone, more recently other corticosteroids have also been misused for fattening purposes. The first part of this study deals with the detection of two of them, namely betamethasone and triamcinolone acetonide. Betamethasone was administered orally to a cow at a dose of 50 mg d-1 for 5 d, then later the same cow was injected intramuscularly with a dose of 50 mg of betamethasone dipropionate. Excretion in urine and faeces was followed with both HPLC-enzyme immunoassay and a previously described method based on negative chemical ionization mass spectrometry (NCI-MS) after oxidation. For the triamcinolone acetonide study a cow was treated with 50 mg d-1 of the drug during a 7 d period. Excretion in faeces was followed with GC-NCI-MS. As triamcinolone acetonide is resistant to the previously described oxidation procedure, however, a hydrolysis step had to be introduced prior to oxidation. In addition to this specific modification necessary for triamcinolone acetonide, in a subsequent part of this study the original oxidation procedure with pyridinium chlorochromate was re-investigated especially to shorten the procedure. With the introduction of potassium dichromate the reaction time could be decreased from 3 h to 10 min.     

Determination of sulphur in fly ash by instrumental proton activation analysis

A method for the determination of sulphur in fly ash by instrumental proton activation analysis using the³⁴S/p,n/^34mCl reaction was developed. The 2128.5 keV and 3305.0 keV -rays of^34mCl /t=32.0 min/ were measured on a Ge/Li/ -spectrometer, shielded with a lead absorber to attenuate low energy -rays. Irradiation and measuring conditions were optimized. The detection limit for instrumental analysis is 0.3 to 1 mg g^–1 and the standard deviation is cca. 4% for a typical sample.     

Catalytic isomerization of olefins on BeO, I

The catalytic activity of BeO for the double bond shift of 1-pentene has been investigated. The maximum activity was exhibited by samples calcined at 1173 K. The effect of pyridine, CO₂ and CCl₄ on the activity was also studied. Lewis acid-base site pairs appear to be active for the isomerization.

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BeO 1- . , 1173 . , CO₂ CCl₄ . - .

     

Synthesis of coumarins by ring-closing metathesis using Grubbs’ catalyst

A novel generally applicable synthesis of coumarins from phenolic substrates utilizing ring-closing metathesis is described. This sequence involves O-allylation of phenols followed by ortho-Claisen rearrangement, subsequent based-induced isomerization affording 2-(1-propenyl)phenols, acylation with acryloyl chloride, and finally ring-closing metathesis (RCM) with Grubbs’ second generation catalyst.