α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 1: Synthesis and stereochemistry. Extension to s-triazine series

The general and efficient synthesis of the title compounds, consisting of the (selective) replacement of chlorine in commercial α-chlorodiazines and cyanuryl chloride by the 3,7-dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy group (Williamson method) is described. The stereochemistry of this new series of derivatives is analysed in terms of different conformational chirality exhibited in solution (¹H NMR) versus solid state (X-ray diffractometry), meso against chiral forms, respectively. In solid state, the inclusion capacity of some chiral networks as well as their supramolecular aggregation is pointed out. A good correlation between rotameric behaviour of the c-5-di(s-tri)diazinyloxymethyl group in the two states is found.     

Lower and upper solutions for elliptic problems in nonsmooth domains

In this paper we prove some existence results of semilinear Dirichlet problems in nonsmooth domains in presence of lower and upper solutions well-ordered or not. We first prove existence results in an abstract setting using degree theory. We secondly apply them for domains with conical points.     

Influence of water on localized and delocalized molecular mobility of cellulose

The influence of hydration on cellulose molecular mobility is investigated by two dielectric methods at different molecular scale. The mobility of side groups, assigned to γ mode, for dried cellulose increases. The water molecules have an anti-plasticizer effect on γ mode due to the water–polymer hydrogen bonding. For the β relaxation mode, only observed by the Thermo Stimulated Current technique, the hydration plays a role of plasticizer. The α relaxation mode assigned to the delocalized cooperative mobility of long chain segments of cellulose is plasticized by water. The study of activated parameters deduced from fractional polarization procedure, shows an increase of the activation enthalpy range with dehydration. It permits to conclude that reduction of hydrogen bonds density leading to a more extended cooperative mobility.     

Perceptual differences between low and high rates of stimulation on single electrodes for cochlear implantees

Previous research has shown that increases in the rate of stimulation on a single electrode yield changes in pitch perception until the rate is increased beyond a given critical rate, after which changes in rate are only perceived as changes in loudness. The critical rate beyond which a rate increase no longer elicits a pitch change in most subjects is approximately 300 Hz, although a small number of subjects have been observed to have critical rates up to approximately 1000 Hz. In this article, we sought to determine if increasing the rate of stimulation beyond the critical rate (up to 12.8 kHz) would eventually result in new changes of perception (other than loudness.) Our data replicate the previously observed results that rates between approximately 300 and 1500 Hz are indistinguishable from each other. However, we observed the finding that a rate of stimulation well above the critical rate (starting between 1500 Hz and 12.8 kHz, depending on electrode and subject) can elicit changes in perception. The perceptual differences between these high rates were sometimes but not always labeled as pitch changes. This phenomenon needs further research to assess its potential relevance to speech perception using high rates of stimulation.     

Variational inequalities with varying obstacles: The general form of the limit problem

When minimizing a functional of the calculus of variations with varying constraints of obstacle type, it may happen that, in the limit problem (when it exists), the constraint is no longer of obstacle type; it may take a “relaxed” form. This situation is analysed in this paper. Following De Giorgi's Γ-convergence approach, a class of functionals is constructed which is compact and which contains the obstacle constraint functionals. In this sense, this class of problems has been closed.     

Analyse par spectrométrie d'absorption infrarouge jusqu'à - 180 °C,de la structure cristalline des mélanges chloroforme-acétonitrile et chloroforme-propionitrile

A study, by infrared spectroscopy between 5000 and 200 cm^?1, in the liquid and solid states down to ? 180 °C, confirms the results obtained by thermal analysis: there is a complex in the case of ethyl cyanide-chloroform mixtures, whereas in the case of methyl cyanide-chloroform mixtures a eutectic is obtained. Furthermore we show, by the analysis of vibrations of the molecular lattice obtained, that, in this eutectic, the chloroform influences the crystalline structure of methyl cyanide.     

Dispositif de prelevement microanalytique de produits alterables

A small glass device is described for microanalytical or submicroanalytical sampling of unstable solid or liquid substances, in an argon atmosphere.

Zusammenfassung

Ein kleines Glasgerät wird beschrieben, das die Probenahme für die Mikrooder Submikroanalyse instabiler fester oder flüssiger Substanzen in Argonatmosphäre erlaubt.     

Etude de l'action de l'oxyde d'azote (III) sur l'indène et ses homologues

Addition of nitrogen trioxide to indene and alkylindenes N₂O₃ adds to indene and homologous yelding pseudonitrosites which are converted to aminoindanes. Treatment of the pseudonitrosites with alcoholic potassium hydroxide gives the correspondent nitroindenes.