Proton-proton correlations at small relative momentum in neon-nucleus collisions at E/A=400 and 800 MeV

Proton-proton small angle correlations have been measured in neon-nucleus collisions, using the 4 pi detector Diogene, at 400 and 800 MeV per nucleon incident energies. Values of the size of the emitting region are obtained by comparison with the Koonin formula, taking into account the biases of the apparatus. The dependence of the density on target mass and incident energy is also analysed.     

Thermal investigations on the crystallization of sorbitol

The melting and crystallization of sorbitol were investigated with the DSC method and thermal microscopy. Sorbitol was found to have two crystalline modifications (confirmed by X-ray diffraction) with different melting points, while rapid cooling of molten sorbitol resulted in an amorphous form. The effect of inoculation on the crystallization of the melt was studied too. Powders of both crystalline modifications were used for this purpose. A new technological process for rapid crystallization of molten sorbitol has been worked out on the basis of the thermal analysis results.     

Thienopyrrolizines: New condensed triheterocyclic systems

Cyclization of 3-(1-pyrrolyl)thiophene-2-carboxamide derivatives of methyl 3-(1-pyrrolyl)-2-thiophenecarboxylate afforded imminium salts and resulted in the formation of thieno[2,3-b]pyrrolizine derivatives.     

Efficient and simple synthesis of 3-aryl-1H-pyrazoles

Efficient preparation of 3-aryl-1H-pyrazoles by reaction of 1-protected-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazoles with (het)aryl halides is described. The choice of THP protecting group is discussed.     

Pyrrolothiénopyrazines: Etude chimique de la pyrrolo[1,2-a]thiéno[2,3-e]pyrazine

The reactivity of pyrrolo[1,2-a]thieno[2,3-e]pyrazine towards quaternisation, bromination, nitration, Friedel-Crafts, Vilsmeier-Haack and Reissert reactions was studied. Assignment of structures to the product is based upon ir, nmr and mass spectral studies.     

Synthesis of new thienocyclopenta[3,2-d]-oxazole and thiazole derivatives

Synthesis of thieno[2′,3′:5,4]cyclopenta[3,2-d]oxazole and thiazole derivatives are achieved by insertion of carbon dioxide and disulfide into 4-amino-5-chloro-5,6-dihydro-4H-cyclopenta[b]thiophen-6-one.     

Investigation of the species-specific degradation behaviour of methylmercury and ethylmercury under microwave irradiation

The degradation behaviour of methylmercury (MeHg) under microwave irradiation is investigated, as is the (different) degradation behaviour of ethylmercury (EtHg) under similar irradiation. A simple and highly sensitive SPME-GC-pyrolysis-AFS system was used to analyse the aqueous MeHg and EtHg standard solutions after derivatization with sodium tetraphenylborate (NaBPh₄). Samples were irradiated in a microwave digester at microwave powers ranging from 20 to 160 W for durations of 2 to 10 min. The different tolerances towards microwave treatment of the two organomercury species were evident. Practically no degradation was experienced for MeHg for up to 8 minutes of irradiation at 120 W or for up to 4 minutes at 160 W. Significant analyte loss was observed for EtHg after 2 minutes at 40 W of microwave power. Awarded a Poster Prize on the occasion of the European Winter Conference on Plasma Spectrochemistry, February 2005, Budapest, Hungary     

A convenient synthesis of new aminomethylenedioxypyrroloindoles via an iminium salt

Cyclization of 2-(1-pyrrolyl)piperonylcarboxamide derivatives gave iminium perchlorates which afforded 9-(N-substituted-imino) and 9-(N-substituted amino)-6,7-methylenedioxypyrrolo[1,2-a]indoles.     

Cycloaddition reactions of 1.3-benzothiazines v synthesis of new tetracyclic ring systems

New tetracyclic derivatives (3a,$\text{b}$, 5, 8) similar to protoberberines, but containing a lactam structural element and other hetero atoms besides the bridge-head nitrogen in rings B and C, were prepared by cycloaddition of 6,7-dimethoxy-2H-1,3-benzothiazine (1a) with $\text{o}$-substituted aromatic carboxylic acid derivatives (2a,$\text{b}$, 4) and from 4- methyl-6,7-dimethoxy-2$\text{H}$-1,3-benzothiazine (1b) with 3.5-dinitrobenzoyl chloride.     

The maximum common substructure as a molecular depiction in a supervised classification context: experiments in quantitative structure/biodegradability relationships

The maximum common structure between two molecules (MCS) induces a similarity that enables one to group compounds sharing the same pattern. This text relates a study based on such a structural depiction in a context of quantitative structure/biodegradability relationships (QSBR). The similarity indices are based exclusively on the MCS. First, the results of statistical tests prove that these indices significantly group compounds of similar activity together. These first conclusions enable the elaboration of classification models using those structural similarities. In a second part, a population of classifiers relying on the maximum common structure and the k-nearest-neighbor algorithm is explored. Finally, a thorough examination of the best models is conducted.