Crystallization in the Al-Si,Al-Ge,and Al-Si-Ge systems at centrifugation

Crystallization in the Al-Si, Al-Ge, and Al-Si-Ge systems at centrifugation is studied. Of them, the Al-Si system is the least prone to sedimentation. In the others, sedimentation considerably changes the structure of the alloys at the bottom of the ingots compared with their top. At certain concentrations of the constituents, the number of crystallites in the lower part of the ingot is larger than in the upper part and the crystallites at the bottom are coarser than at the top. The Si: Ge atomic ratio in the Al-Si-Ge system changes by a factor of 2–12 against the initial ratio (1: 1) when the (Si + Ge) concentration changes as a result of centrifugation. Also, this ratio changes over the crystal surface (in the samples not subjected to centrifugation, this ratio remains unchanged over the surface). Crystallites in the Al-Si-Ge system are covered by Ge.     

Semileptonic (Λ b → Λcev) decay in a field theoretic quark model

The semileptonic decay width of heavy baryons such as (Λ _b → Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution inside the hadron as free parameters.     

Pinic and pinonic acid formation in the reaction of ozone with alpha-pinene

The mechanism of formation of key compounds in atmospheric secondary aerosol (SOA) has been investigated by studying the products of the ozonolysis of an enal derived from alpha-pinene using gas chromatography coupled to mass spectrometry.