Separation and characterisation of caprolactam-formaldehyde reaction products

Methylolation and condensation products formed in caprolactam-formaldehyde reaction mixtures have been identified using nuclear magnetic resonance (NMR) and mass spectrometry (MS). Previously unreported side-products were also detected. All of the reaction products were separated by micellar electrokinetic chromatography (MEKC) and high performance liquid chromatography (HPLC), and the separation parameters, such as efficiency and distribution constants, obtained in the two techniques were compared. For quantification, the response factors for the monomers were determined using standard calibration and hydrolysis, whilst those for the condensation products were deduced from the values of the monomers. The accurate determination of the response factors was confirmed by checking the mass balance of a known mixture.     

Retrosynthetic analysis of fullerene C(60): structure, stereochemistry, and calculated stability of C(30) fragments.

The total number of possible retrosynthetic bisections of C(60) leads to nine different isometric C(30) fragments. These molecules include five chiral units, four of which derive from partitions corresponding to four distinct "Coupes du Roi". The energies, curvatures, and homodesmotic stabilization energies of the C(30) fragments are evaluated at the ab initio 6-31G level.     

A novel piezo-optical styrene sensor incorporating polymer-supported tribromide ion

Encapsulation of Amberlyst A-26 supported tribromide in a 10,000 MW polyethylene glycol matrix gives a robust colour-sensitive reagent matrix which can be deposited on indium-tin oxide coated polyvinylidene fluoride (PVDF) piezoelectric film for the detection of styrene (and other alkene) vapours.     

Two classes of conformally flat contact metric 3-manifolds

We give a classification of 3—dimensional conformally flat contact metric manifolds satisfying: =0(=L g) orR(Y, Z)=k[(Z)Y–(Y)Z]+[(Z)hY]–(Y)hZ] wherek and are functions. It is proved that they are flat (the non-Sasakian case) or of constant curvature 1 (the Sasakian case).     

Synthesis of 8-dipropylamino-7,8,9,10-tetrahydrophenanthridines as potential serotoninergic agonists

A number of 8-dipropylamino-7,8,9,10-tetrahydrophenanthridines have been prepared as analogs of the known serotoninergic agonist 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT) and their affinity for the 5-HT_1A receptor subtype evaluated by radioligand binding assay.     

Pressure effect on the magnetic properties of CeSb

Changes in the magnetic field-temperature phase diagram of CeSb with pressure have been determined up to 6kbar by magnetization measurements on a single crystal. High magnetic fields up to 70 kOe have been applied along a four fold axis of the rock-salt type structure. The features of the phase diagram are not changed by pressure except for a shift towards high temperature. The saturated magnetic moment and the hysteresis of the transition fields are independent of pressure. Variation of exchange energy with volume is deduced from the experimental results. It is shown that the effect of pressure and the magnetic volume anomaly at 0 K are essentially due to the variation of the exchange energy in the ferromagnetic (001) planes.     

2-Groupe des classes positives d'un corps de nombres et noyau sauvage de la K-théorie

We compute the 2-rank of the wild kernel WK₂(F) of a number field by constructing a 2-class group ad hoc. The main result generalizes in the more intricate case the canonical isomorphism established for odd primes under the assumption in a previous article (cf. (Acta. Arith. 67 (1994) 335; Math. Z. 238 (2001) 335)). It involves a criterium of triviality for the 2-part of the wild kernel of Galois number fields and, in the particular case of quadratic fields, it leads to a logarithmic interpretation of the diophantine conditions obtained by other authors.     

On conformally flat contact metric manifolds

In the present paper we classify the conformally flat contact metric manifolds of dimension satisfying . We prove that these manifolds are Sasakian of constant curvature 1.     

Nonlinear synthesis of input signals in ultrasonic experimental setups

A method is proposed to find the digital input signals to enter in nonlinear acoustical systems (power amplifiers, transducers, etc.) in order to obtain desired arbitrary response signals. The searched input signals are found by performing a Monte Carlo search guided by a simulated annealing process applied to a hidden model with a small number of parameters. The physical system is actually used in the optimization procedure, in a real-time manner, so that no theoretical model of the system response is required. The main aspects of the algorithm are described and illustrated with several examples.