Studies of Nucleon Spin Structure at HERMES

The HERMES experiment studies the spin structure of the nucleon using polarized semi-inclusive deep-inelastic positron scattering and polarized quasi-real photoproduction. Previous analyses of nucleon spin structure combine inclusive deep-inelastic scattering data and measured hyperon decay constants assuming SU(3)_(flavor) symmetry; asymmetries in the processes studied at HERMES may constrain nucleon spin structure more directly. Results are discussed for quark polarizations extracted from semi-inclusive deep-inelastic scattering asymmetries, for gluon polarization extracted from the asymmetry of high-p_T hadron pairs, and for the first observation of single-spin azimuthal asymmetries in pion production

Corrosion fatigue of high strength fastener materials in seawater

Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure