Stereospecific Synthesis of Intermediates for 11-Aza-11-deoxy and 11-Azaprostaglandin Analogues from L-Arabinose

The syntheses of chiral synthons for 11-aza-11-deoxy and 11-azaprostanoids are described. The key intermediate in both routes was 5-O-benzoyl-3C-carboxymethyl-2,3-γ-lactone)-3-deoxy-α-L-lyxo-furanose which is readily available from L-arabinose.     

Hidden magnetic frustration by quantum relaxation in anisotropic Nd langasite

The static and dynamic magnetic properties of the Nd(3)Ga(5)SiO(14) compound, which appears as the first materialization of a rare-earth kagome-type lattice, were reexamined, owing to contradictory results in the previous studies. Neutron scattering, magnetization, and specific heat measurements were performed and analyzed, in particular, by fully taking account of the crystal electric field effects on the Nd(3+) ions. One of the novel findings is that the peculiar temperature independent spin dynamics observed below 10 K expresses single-ion quantum processes. This would short-circuit the frustration induced cooperative dynamics, which would emerge only at very low temperature.     

Superconducting PrOs4Sb12: a thermal conductivity study

The superconducting state of the heavy fermion PrOs4Sb12 is studied by heat transport measurements on a highly homogeneous single crystal exhibiting only one transition peak in the specific heat. The field and temperature dependence of the thermal conductivity confirm multiband superconductivity and point to fully open gaps on the whole Fermi surface.     

Apparent spin polarization decay in Cu-dusted Co/Al2O3/Co tunnel junctions

Co/Al2O3/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated with in situ growth characterization and ex situ magnetotransport measurements. Cu interlayers grown on Co give an approximately exponential decay of the tunneling magnetoresistance with xi approximately 0.26 nm while those grown on Al2O3 have a decay length of 0.70 nm. The difference in decay lengths can be explained by different growth morphologies, and in this way clarifies a present disagreement in the literature. For monolayer coverage of Cu, we show that the tunneling spin polarization is suppressed by at least a factor of 2 compared to Co and beyond approximately 5 ML it becomes vanishingly small.     

Energy dependence of π+ induced two- and four-nucleon removal

De-excitation γ-rays have been detected from nuclear states following positive pion induced two-nucleon removal from ¹²C and four-nucleon removal from ¹⁶O. Excitation functions for population of discrete states were obtained for positive pions of 75, 125, 150, 200, 225, 250 and 290 MeV. The pion-nucleon (3, 3) resonance is not reflected in the cross sections for either reaction. Implications of the observed energy dependence are discussed.