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The distribution of seismic anisotropy in the mantle wedge beneath northeast Japan is inferred from deformation mechanisms: a lattice-preferred orientation and seismic anisotropy are generated by deformation via dislocation creep in the upper mantle, but not by diffusion creep or frictional sliding. Based on the thermal structure and stress field of the upper mantle beneath northeast Japan, deformation throughout most of the mantle wedge is inferred to be controlled by diffusion creep, and the region of dislocation creep is limited to a thin layer of 10-20 km thickness within a region of relatively high stress and low temperature located above the subducting slab and beneath the island arc crust. The relatively short delay time recorded in northeast Japan is consistent with the occurrence of a thin anisotropic layer within the mantle wedge. [ABSTRACT FROM AUTHOR]

Objective: To compare frictional resistance of the plastic preadjusted brackets ligated with the low-friction ligatures with those of the conventional elastomeric ligatures. Design: In vitro study. Setting: Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. Materials and methods: The testing model consisted of four 0.022-inch plastic preadjusted brackets for the first premolar, the canine, the lateral incisor, and the central incisor. A superelastic nickel-titanium 0.014-inch wire and a stainless steel 0.019 x 0.025-inch wire were used for this test. The brackets were either aligned or out of line by 0.5, 1.0, 1.5 and 2.0 mm for the 0.0 14- inch wire and aligned for the 0.019 x 0.025-inch wire. The frictional forces in plastic preadjusted brackets with low-friction ligatures and conventional elastomeric ligatures were measured at a pulling speed of 0.1 mm/second. Welch t-tests were used to compare the mean differences of each testing measurement between the low-friction and the conventional elastomeric ligatures. Results: In both use of the superelastic nickel-titanium 0.014-inch wire and the stainless steel 0.0 19 x 0.025-inch wire, the brackets with the low-friction ligatures showed significantly lower frictional forces than those of the conventional elastomeric ligatures in both aligned and all misaligned brackets (P < 0.000 1). Conclusion: The study found the significantly lower frictional forces for the low-friction ligatures than those of the conventional elastomeric ligatures. [ABSTRACT FROM AUTHOR]