Gamma-gamma angular correlation study of oxygen motion in yttria-stabilized zirconia

The nuclear quadrupole relaxation of ¹⁸¹Ta in ZrO₂9 mole% Y₂O₃ has been measured by time differential angular correlations between 350 and 1150°C. The results are consistent with a distribution of the activation energy controlling the local motion of oxygen vacancies.     

Pentamethoxynitrosobenzene: (MeO)5phNO. A useful new spin-trapping agent

Pentamethoxynitrosobenzene (PMeONB) has been prepared and its use as a spin-trapping (ST) agent has been investigated. Its solubility is adequate for ST in most organic solvents; compared with the routinely used aryl nitroso compounds, PMeONB is more dissociated into the active monomeric form in solution; the potential windows are of the same order of magnitude. Its spin adduct ESR spectra give move information on the trapped radical than those of any other ST agent.     

N-tert-butyl-N-phosphonyloxyaminyls a new class of persistent radicals

The title radicals have been generated by hydrogen abstraction from the corresponding hydroxylamines in benzene solution. In the absence of oxygen these radicals are extremely persistent and their esr data (a_N14, a_N15 and a_C13, determined without isotopic enrichment) are characteristic of a electronic configuration.     

Hydrosilylation d'alcools en milieu sel fondu

Hydrosilylation of alcohols has been carried out in molten dodecylammonium propionate at low temperature (70°C). The salt is used as solvent and as catalyst.     

Neutron-proton radius differences and isovector deformations from π+ and π− inelastic scattering from 18O

π⁺ and π^? elastic and inelastic scattering from ¹⁸O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio $\text{σ(π}{}^{\mathrm{?}}\text{)}\text{σ(π}{}^{\mathrm{+}}\text{)}$ for the 2₁⁺ state is 1.86(16), while for the 3₁^? state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 2₁⁺ transition and partial neutron blocking for the 3₁^? transition. Optical model analysis of elastic scattering leads to the conclusion that $\text{〈r}{}_{\mathrm{<mtext>n</mtext>}}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{?〈r}{}_{\mathrm{<mtext>p</mtext>}}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{=0.03(3)}\text{fm}$.     

A new reversed-phase liquid chromatographic/tandem mass spectrometric method for analysis of underivatised amino acids: evaluation for the diagnosis and the management of inherited disorders of amino acid metabolism

Seventy-six compounds of biological interest for the diagnosis of inherited disorders of amino acids (AA) metabolism have previously been demonstrated to be detectable in positive mode electrospray ionisation tandem mass spectrometry (ESI-MS/MS), after separation by ion-pairing reversed-phase liquid chromatography (RPLC). The separation method used tridecafluoroheptanoic acid as ion-pairing agent, and a gradient of acetonitrile for the elution of the most retained compounds. This method had previously been demonstrated to be suitable for the qualitative diagnosis of many AA disorders, and for the quantitative measurement of 16 AA in biological fluids, using their stable isotope labelled (SIL) AA as internal standard. For quantification of the other AA, an internal standard was chosen among the available SIL-AA, as close as possible to the analyte to be measured, in terms of structural analogy, and of retention time in the chromatographic system. The performances of the quantitative analysis of the other AA to be measured are reported here. They show validated results for several AA, allowing their accurate quantification, with another SIL-AA as internal standard. For some other AA, quantitative results were not accurate, allowing only semi-quantitative or qualitative determination for these parameters.     

On the relationship between the phonon anomalies and the AB initio calculated Fermi surfaces of TaC and NbC

First principles augmented plane wave calculations show that the Fermi surfaces of TaC and NbC contain flat parallel sheets, while that of HfC is relatively “normal”. The phonon anomalies in the former two materials are shown to stem from specific transitions across the Fermi surface.