Interaction between organophosphorous hydrolase and paraoxon studied by surface chemistry in situ at air-water interface

Subphase conditions have been optimized to obtain stable organophosphorous hydrolase (OPH-EC 3.1.8.1) as Langmuir films. The Langmuir film was characterized by surface pressure and surface potential-area isotherms and UV-Vis spectroscopy in situ. The interaction of an organophosphorous compound, namely Paraoxon, with the OPH film was investigated for various surface pressures. The stability of the monolayer and the evidence of the enzyme activity at air-water interface support the use of enzyme LB films as biosensor.     

Liquid alumina: detailed atomic coordination determined from neutron diffraction data using empirical potential structure refinement

The neutron scattering structure factor S(N)(Q) for a 40 mg drop of molten alumina (Al2O3) held at 2500 K, using a laser-heated aerodynamic levitation furnace, is measured for the first time. A 1700 atom model of liquid alumina is generated from these data using the technique of empirical potential structural refinement. About 62% of the aluminum sites are 4-fold coordinated, matching the mostly triply coordinated oxygen sites, but some 24% of the aluminum sites are 5-fold coordinated. The octahedral aluminum sites found in crystalline alpha-Al2O3 occur only at the 2% level in liquid alumina.     

N NMR in AlN and BN

A characterisation by ¹⁴N NMR of the binary nitrides AlN and BN is presented. Both the static and magic angle spinning (MAS) lineshapes have been investigated in order to determine, or set upper limits on, the nuclear quadrupole coupling (C_q) at the nitrogen site. Additional data are given for the C_q values at the Al and B sites. A comparison is made with other similar (mainly wurtzite) binary compounds for which C_q is known at each atomic site.     

27Al NMR study of the structure of lanthanum- and yttrium-based aluminosilicate glasses and melts

We have investigated by (27)Al nuclear magnetic resonance spectroscopy some compositions in the Ln(2)O(3)-Al(2)O(3)-SiO2 (Ln = Y or La) ternary phase diagram containing more than 60 mol % of SiO2. One- and two-dimensional high-field (17.6 T) high-speed (30 kHz) magic angle spinning experiments have been performed along with simulations of the spectra to quantify the amount of penta-coordinated aluminum present in those glasses as a function of composition. Very high-temperature experiments have allowed to follow selected samples from 2200 degrees C down to 1700 degrees C and hence to characterize the aluminum coordination state and dynamics in those liquids. The present study re-enforces the current view that "minor" species such as penta-coordinated aluminum are actually present in a considerable amount in aluminosilicate glasses, and high-temperature liquids at and above the charge compensation join. The high-field strength of Y3+ and La3+ reveal, for the first time in glasses, a different mean electric field gradient perceived by the tetra- and penta-coordinated aluminum environments. The movements responsible for the NMR relaxation of aluminum in the high-temperature liquid are shown to be uncorrelated with the movements responsible for the macroscopic shear viscosity. Results obtained both on glasses and in situ at high-temperature suggest a preferential localization of Ln3+ nearby tetra-coordinated aluminum species, with possible formation of tricluster and/or Ln3+ coordination changes.     

Etude par rayons X à haute temperature des transformations polymorphiques des pérovskites LnAlO3 (Ln = élément lanthanidique)

The temperatures of phase transitions of the rare earth aluminates have been determined by high temperature X-ray diffractometry. All of the transitions are reversible and occur respectively for Rh ? C at 500°C (LaAlO₃), 1330°C (PrAlO₃), 1550°C (NdAlO₃), and 1950°C (SmAlO₃) and for O ? Rh at 770°C (SmAlO₃), 1330°C (EuAlO₃), and 1700°C (GdAlO₃). LnAlO₃ perovskites from TbAlO₃ up to LuAlO₃ are orthorhombic without any phase transition.     

An optical and structural investigation of rare-earth hydroxycarbonates

Physical data are given for the two polymorphs, ancylite type (A-type) and bastnaesite type (B-type), of the rare-earth hydroxycarbonates [Ln(OH)CO₃]. They include infrared absorption spectra and, in the case of neodymium electronic absorption spectra for the 4f ³ configuration recorded at 4 K.From the spectra one concludes that the rare-earth ion largely occupies a single site for both compounds. The OH infrared bands are very sharp. The optical data are compared with the results of structural investigations.