ABSTRACT. Subgrain boundaries revealed as shallow sublimation grooves on ice sample surfaces are a direct and easily observable feature of intracrystalline deformation and recrystallization. Statistical data obtained from the EPICA Dronning Maud Land (EDML) deep ice core drilled in East Antarctica cannot detect a depth region of increased subgrain-boundary formation. Grain-boundary morphologies show a strong influence of internal strain energy on the microstructure at all depths. The data do not support the classical view of a change of dominating recrystallization regimes with depth. Three major types of subgrain boundaries, reflecting high mechanical anisotropy, are specified in combination with crystal-orientation analysis.

Global cooling in intermediate glacial climate with northern ice sheets preconditions climatic instability with bipolar seesaw.

Kyanite bearing eclogitic assemblages occur in the highest grade zone of the Sanbagawa metamorphic belt, central Shikoku, Japan. The eclogites consist mainly of garnet, omphacite, phengite, kyanite, epidote, quartz and rutile. Compositionally variable amphibole (glaucophane/barroisite/pargasite), phengite and paragonite occur as inclusions in garnet and other eclogite facies phases. Careful examination of garnet zoning in kyanite eclogites suggests that (i) most garnet grains show complex zoning consisting of relatively Ca rich/Mg poor inner and Ca poor/Mg rich outer segments, (ii) the inner segment of the zoned garnet formed at the eclogite facies stage, and (iii) the Mg rich outermost rim of garnet does not always represents a composition at peak eclogite stage but could form at lower pressure conditions of subsequent epidote amphibolite facies. The assemblage of inner segment of garnet, omphacite, phengite, kyanite and quartz points to equilibrium conditions of 2.3 2.4 GPa/675 740 °C. The metamorphic P T conditions of the eclogite facies stage reported in literature have been estimated assuming that the outermost rim of garnet with Mg rich composition was in equilibrium with other eclogite facies phases. Therefore, P T estimations of the eclogite facies stage in the Sanbagawa metamorphic belt should be re examined carefully on the basis of textural and compositional heterogeneities of constituent minerals.

We theoretically show that a single free electron in circular motion radiates an electromagnetic wave possessing helical phase structure, which is closely related to orbital angular momentum carried by it. We experimentally demonstrate it by interference and double-slit diffraction experiments on radiation from relativistic electrons in spiral motion. Our results indicate that photons carrying orbital angular momentum should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in cosmic space. We propose promising laboratory vortex photon sources in various wavelengths ranging from radio wave to gamma-rays.