In order to better understand the densification of polar firn, firn cores from the three sites within ~10 km of Dome Fuji, Antarctica, were investigated using surrogates of density: dielectric permittivities εv and εh at microwave frequencies with electrical fields in the vertical and horizontal planes respectively. Dielectric anisotropy Δε (=εv − εh) was then examined as a surrogate of the anisotropic geometry of firn. We find that layered densification is explained as a result of complex effects of two phenomena that commonly occur at the three sites. Basically, layers with initially smaller density and smaller geometrical anisotropy deform preferentially throughout the densification process due to textural effects. Second, layers having a higher concentration of Cl− ions deform preferentially during a limited period from the near surface depths until smoothing out of layered Cl− ions by diffusion. We hypothesize that Cl− ions dissociated from sea salts soften firn due to modulation of dislocation movement. Moreover, firn differs markedly across the three sites in terms of strength of geometrical anisotropy, mean rate of densification and density fluctuation. We hypothesize that these differences are caused by textural effects resulting from differences in depositional conditions within various spatial scales.

We previously suggested that antenatal pestivirus infection might play a role in the pathogenesis of perinatal brain white matter damage (WMD) in preterm infants. We have now examined 22 brains from stillborns and deceased newborns (both preterm and term) for the presence of bovine virus diarrhoea virus (BVDV) antigen. The brains of five females and five males with WMD (median gestational age 36.5wks), and nine female and three male controls (median gestational age 36.5wks) were used in the study. No BVDV antigen was detected in any of the 22 brains. We conclude that brain infection with BVDV is unlikely to play a role in WMD pathogenesis among preterm or term newborns. Further research is needed to test the hypothesis that intrauterine exposure to pestivirus antigen elicits a fetal inflammatory response which then contributes to WMD.

To better understand how ice fabric evolves in polar ice sheets, we use X-ray diffraction to measure ice crystal orientations. X-ray measurement equipment which can measure the orientation of the c axis and a axis of each crystal in a thin section with high measurement accuracy was developed. In this study, we present a-axes orientation distribution of the deep part of the GRIP (Greenland summit) ice core. At some depths, we find an anisotropic distribution of a-axes orientation. Long-term uniaxial compression tests are also carried out on the GRIP ice core to investigate the ice fabric evolution process. The c-axis orientation distribution develops into a stronger single maximum as the strain increases up to about 20% strain. We find that the a axes of each grain also tend to cluster close to nearly a mutual direction. We discuss the development process of ice fabrics, taking into consideration the distribution of the a-axis orientations. It is suggested that these fabrics may be attributed to a local simple shear deformation in the deep part of an ice sheet.

We performed X-ray diffraction measurements on eight ice samples taken between 3200 and 3611 m depth of the Vostok (Antarctica) ice core to observe lattice distortions of ice crystals. Selected samples represent three distinct sections of the core: (i) glacier (meteoric) ice with well-preserved climatic record (down to 3310 m), (ii) ‘shear zone’ at the base of the glacier ice (3450– 3537 m) within which the climatic record is disturbed by ice deformation, and (iii) accretion ice formed by freezing of subglacial Vostok lake waters at the base of the ice sheet (from about 3537 m depth to the bottom of the core). The dislocation density decreases from 1012 to 108m–2 with increasing depth. In the accretion ice, lattice distortion tends to decrease with depth. However, the dislocation density does not reach a level typical for laboratory-grown columnar ice even at 3610 m. This reflects plastic deformation which accretion ice has undergone after its formation.

We deposited MgF2 thin films using the ion-plating method that features RF and DC biasing to the substrate holder. We investigated the effects of RF powers, substrate temperatures (Ts) and DC bias voltages on optical absorption and abrasion resistance of the films. The optical absorption deteriorated by increasing RF power and Ts. In particular, the deterioration was quite serious when the Ts were above 423 K. The abrasion resistance increased by increasing the Ts. We found that the abrasion resistance could be improved also by increasing a DC bias voltage. The same abrasion resistance as the film deposited by a conventional heat resistance deposition at 573 K was obtained by applying the DC bias voltage of -500 V and the Ts of 300 K.