NMR study of the complexation of boric acid with catechol (1,2-dihydroxybenzene)

The boric acid–catechol system in aqueous solutions has been studied by means of ¹¹B, ¹H and ¹³C NMR over wide ranges of concentration and pH. ¹¹B spectra show a striking difference between the complexation possibilities of dilute and more concentrated solutions of boric acid. Both the 1:1 and 1:2 complexes can be simultaneously observed by ¹³C NMR.     

Generalized Hermite polynomials

Hermite polynomials of several variables are defined by a generalization of the Rodrigues formula for ordinary Hermite polynomials. Several properties are derived, including the differential equation satisfied by the polynomials and their explicit expression. An application is given.     

Recherches sur le dosage de la cellulose

The proposed method for the estimation of cellulose includes a neutralisation after each attack, This method has the adventage of abolishing washings and centrifugations, thus saving time, and that of ensuring more reproducible results and thereby greater precision.     

On the control of queueing systems with failures and repairs

Several classes of problems can be modelled as queueing systems with failures where preventative maintenance has to be optimized: relevant examples are computer systems, databases and production lines. This paper studies a simple case of such a situation based on the M/M/1 queue where the state of the server can take two values (on, off); the transition on–off happens either when there is a failure or when one decides to maintain. The characterization and an approximation of an optimal policy are given. Extensions to more general models, including general Markov processes, are examined.     

Structure électronique de quelques dérivés nitrés insaturés (méthode L.C.A.O. améliorée)

The electronic structure of Nitro-,p- andm-dinitro-,s-trinitro-benzene, nitro-ethylene, mono-, and dinitro-butadien have been calculated by an improved LCAO method.     

NMR of some benzodiazepine drugs: Structure elucidation with lanthanide-induced shifts of N-1 substituted benzodiazepinones

Two 1,4-benzodiazepinones of psychopharmacological interest, pinazepam (2) and prazepam (3), were studied in solution by ¹³C and ¹H NMR. ¹H variable-temperature experiments showed that the seven-membered ring exists in a simple pseudo-boat form at room temperature, but the energy barrier is higher in 3 (ΔG_405°c = 82.8 kJ mol^?1) than in diazepam (1). Moreover, upon addition of LSR, the boat conformation is retained in the lanthanide ion-substrate complex, as with 1 in the solid state. Using a concentration-dependent shift technique and a computer-assisted LIS method, the conformations of the N-branched side-chain were investigated. Two preferred orientations were found for the propargyl group of 2, while three unequally populated conformations of the cyclopropyl moiety of 3 are distributed preferentially in the sterically unhindered space around the complex.