Discovery of a Superconducting Cu–Bi Intermetallic Compound by High‐Pressure Synthesis

A new intermetallic compound, the first to be structurally identified in the Cu?Bi binary system, is reported. This compound is accessed by high‐pressure reaction of the elements. Its detailed characterization, physical property measurements, and ab initio calculations are described. The commensurate crystal structure of Cu₁₁Bi₇ is a unique variation of the NiAs structure type. Temperature‐dependent electrical resistivity and heat capacity measurements reveal a bulk superconducting transition at T_c=1.36 K. Density functional theory calculations further demonstrate that Cu₁₁Bi₇ can be stabilized (relative to decomposition into the elements) at high pressure and temperature. These results highlight the ability of high‐pressure syntheses to allow for inroads into heretofore‐undiscovered intermetallic systems for which no thermodynamically stable binaries are known.     

Spatial distribution of cold antihydrogen formation

Antihydrogen is formed when antiprotons are mixed with cold positrons in a nested Penning trap. We present experimental evidence, obtained using our antihydrogen annihilation detector, that the spatial distribution of the emerging antihydrogen atoms is independent of the positron temperature and axially enhanced. This indicates that antihydrogen is formed before the antiprotons are in thermal equilibrium with the positron plasma. This result has important implications for the trapping and spectroscopy of antihydrogen.     

Antiproton-proton annihilation at rest in H2 gas into π+ π− π0

Zeitschrift für Physik C Particles and Fields - Annihilation of antiprotonic hydrogen atoms into π+ π? π0 is studied by stopping antiprotons from LEAR in hydrogen gas. Two...     

Des surfaces à courbure négative constante dans l'espace à trois dimensions et de leurs singularités

Sans résumé     

Quantification of N-acetylaspartylglutamate, an N-terminal blocked dipeptide neurotransmitter candidate, in brain slice superfusates by gas chromatography-mass spectrometry

N-Acetylaspartylglutamate is a highly promising neurotransmitter candidate. A method for its quantification has been developed that allows to investigate its stimulation-induced release from brain slices. The method is based on ion-exchange prepurification, derivatization with HCl in methanol, separation by capillary gas chromatography and quantification by ammonia chemical ionization mass spectrometry with selected-ion monitoring. Deuterium-labelled N-acetylaspartylglutamate is used as internal standard. The method has been validated, also with respect to possible interfering compounds. A limit of quantification in the low pmol to high fmol range has been achieved, which is clearly sufficient for the intended purpose. A detailed analytical procedure is given, and alternatives for some of the different steps are discussed. Derivatization with diazomethane instead of methanolic HCl turned out to be impracticable. The method may well be applicable to certain other N-terminal blocked di- and tripeptides and to acylated amino acids.     

Measurement and phase-shift analysis of the p parameter in π+p scattering at 236 MeV

The P parameter for π⁺p scattering at 236.3 MeV has been measured between 50° and 146° c.m. with very low background using a butanol polarized proton target. The resulting D phases are in fair agreement with dispersion relation values.