Synthesis of Al–Cr decagonal quasicrystal nanoparticles and their temperature of phase transformation to stable crystal phase

The synthesis of Al–Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700 °C. It was also determined that part of the QC nanoparticle decomposed into hex-Al₈Cr₅ and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured.     

Proton magnetic relaxation and ionic conductivity of ammonium hydronium β″-alumina

The protonic motion in NH⁺₄-H⁺(H₂O)_nβ″ -alumina wasstudied by measurements of proton spin-lattice and spin-spin relaxation times. The results show that two types of NH⁺₄ reorientation, that is, three-fold reorientation about its unique C₃ axis and tumbling motion as a whole, occur below room temperature. Above room temperature a fast proton translational diffusion was apparent, and its activation energy was estimated to be 36 kJ/mol. On the other hand, the conductivity measured on a pressed sample by an ac method is strongly humidity-sensitiveand changes by more than five orders from 0 to 100% relative humidity. The activation energy also may be humidity-sensitive. Its value was 73 kJ/mol for the sample equilibrated at 90°C in a dry nitrogen atmosphere.     

Unusual stereoselectivity in the synthesis of 4-oxa-δ-valerothiolactones: structure proof of β-hydroxythioamide

Stereoselectivity in the formation of 4-oxa-δ-valerothiolactone 2 from β-hydroxythioamide 1 is discussed. The structure of 1 is deduced from the structure of 2.     

The chemistry of O-silylated ketene acetals; diastereoselective Aldol reaction of 2,3-O-isopropylidene-D (and L)-glyceraldehydes leading to 2-deoxy-D (and L)-riboses

Diastereoselective carbon-carbon bond forming reaction of 2,3-O-isopropylidene-D (and L)-glyceraldehydes (D and L-2) with ketene silyl acetals (1a,b) occurred in acetonitrile under mild conditions to give the corresponding $\text{anti}$-β-siloxyesters (D and L-3a) as major products, which could be converted through a few additional steps to 2-deoxy-D(and L)-riboses.     

Laser Flash Photolysis of 2,2'-Dithiobls(pyridine N-oxide): Reactivity of N-Oxypyridyl-2-thio Radical

Abstract— Reaction kinetics of radicals produced by the nanosecond laser flash photolysis of 2,2'-dithiobis(pyridine N -oxide) and related compounds have been studied. The transient absorption band at 360 nm was attributed to the radical in which the unpaired electron mainly localizes on the S atom ( N -oxypyridyl-2-thio radical). The reactivities of the radical for conjugated dienes are lower than those of the pyridyl-2-thio radical, suggesting that a considerable unpaired electron density on the S atom delocalizes onto the N -oxypyridine moiety. The addition reaction rate of the radical to the conjugating diene was accelerated with hydrogen-bonding solvents and with addition of the cation, which may stabilize the N+-O^- canonical structure, increasing the unpaired electron density on the S atom. By the photolysis of N -hydroxypyridine-2-thione, the N-O bond was predominantly dissociated producing a pyr-idyl-2-thio radical. By the photolysis of its anion, photoejection took place followed by the N-O bond fission, yielding pyridine-2-thione.     

Intermediate resonance of inelastic 12C + 12C scattering

The intermediate resonances observed in the inelastic ¹²C + ¹²C cross sections to the single and mutual 2₁⁺(4.43 MeV) excitations and the single 3₁^? (9.64 MeV) excitation are studied by the coupled-channel method with the use of the coupling interaction derived by the folding procedure between ¹²C and ¹²C. It is shown that the model is successful in reproducing the gross structures of the inelastic cross sections and especially the correlated resonance energies of the inelastic channels. The inelastic resonances are shown to be due to the molecular resonances in an adiabatic potential between two ¹²C, which reproduces correctly the coupled channel resonances.