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.

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This article presents a comparative study of the modal parameter identification of structures based on the continuous wavelet transform (WT) using the modified complex Morlet wavelet function and the improved Hilbert-Huang transform (HHT). Special attention is given to some implementation issues, such as the modal separation and end effect in the WT, the optimal parameter selection of the wavelet function, the new stopping criterion for the empirical mode decomposition (EMD) and the end effect in the HHT. The capabilities of these two techniques are compared and assessed by using three examples, namely a numerical simulation for a damped system with two very close modes, an impact test on an experimental model with three well-separated modes, and an ambient vibration test on the Z24-bridge benchmark problem. The results demonstrate that for the system with well-separated modes both methods are applicable when the time-frequency resolutions are sufficiently taken into account, whereas for the system with very close modes, the WT method seems to be more theoretical and effective than HHT from the viewpoint of parameter design.

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The dielectric properties of a polymer/liquid-crystal (LC) composite film and their influence on the electrooptical response have been investigated. The composite film in which an LC material is embedded as a continuous phase in a three-dimensional spongy polymer matrix shows an electrooptical effect based on a novel concept of light scattering. The electrooptical response speed for the composite film is proportional to ~AeE3, where Ac is the dielectric anisotropy of the LC, and E is the electric field. The dielectric properties of the composite film are approximately explained by the series-connected dielectric composite model consisting of the polymer matrix and the LC phases. Since the magnitude of the ratio of the dielectric constants of both polymer and LC phases, t'p/«'lc. is not always the same as that of the electric conductivities, o-p/o-LC, the magnitude of an ac electric field in the LC phase is modulated and depends on the frequency of the externally applied ac electric field. Further, the frequency dependence of the magnitude of an ac electric field in the LC domain is calculated on the basis of the series-connected dielectric composite model. The calculated result explains qualitatively the frequency dependence of the electrooptical response rise time for the composite film. Also, it is concluded, from the dielectric model calculation, that the electrooptical response rise speed in a wide frequency range of electric field could be improved by using a polymer matrix with greater magnitudes of both electric conductivity and dielectric constant.