Proceedings of the Japan Academy, Series B

Reviews

Modeling fast and slow earthquakes at various scales

Satoshi IDE

2014 Volume 90 Issue 8 Pages 259-277
Published: October 10, 2014
Released on J-STAGE: October 11, 2014

DOIhttps://doi.org/10.2183/pjab.90.259

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Earthquake sources represent dynamic rupture within rocky materials at depth and often can be modeled as propagating shear slip controlled by friction laws. These laws provide boundary conditions on fault planes embedded in elastic media. Recent developments in observation networks, laboratory experiments, and methods of data analysis have expanded our knowledge of the physics of earthquakes. Newly discovered slow earthquakes are qualitatively different phenomena from ordinary fast earthquakes and provide independent information on slow deformation at depth. Many numerical simulations have been carried out to model both fast and slow earthquakes, but problems remain, especially with scaling laws. Some mechanisms are required to explain the power-law nature of earthquake rupture and the lack of characteristic length. Conceptual models that include a hierarchical structure over a wide range of scales would be helpful for characterizing diverse behavior in different seismic regions and for improving probabilistic forecasts of earthquakes.

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Nonlinear ship waves and computational fluid dynamics

Hideaki MIYATA, Hideo ORIHARA, Yohei SATO

2014 Volume 90 Issue 8 Pages 278-300
Published: October 10, 2014
Released on J-STAGE: October 11, 2014

DOIhttps://doi.org/10.2183/pjab.90.278

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Research works undertaken in the first author’s laboratory at the University of Tokyo over the past 30 years are highlighted. Finding of the occurrence of nonlinear waves (named Free-Surface Shock Waves) in the vicinity of a ship advancing at constant speed provided the start-line for the progress of innovative technologies in the ship hull-form design. Based on these findings, a multitude of the Computational Fluid Dynamic (CFD) techniques have been developed over this period, and are highlighted in this paper. The TUMMAC code has been developed for wave problems, based on a rectangular grid system, while the WISDAM code treats both wave and viscous flow problems in the framework of a boundary-fitted grid system. These two techniques are able to cope with almost all fluid dynamical problems relating to ships, including the resistance, ship’s motion and ride-comfort issues. Consequently, the two codes have contributed significantly to the progress in the technology of ship design, and now form an integral part of the ship-designing process.

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Lewy body disease and dementia with Lewy bodies

Kenji KOSAKA

2014 Volume 90 Issue 8 Pages 301-306
Published: October 10, 2014
Released on J-STAGE: October 11, 2014

DOIhttps://doi.org/10.2183/pjab.90.301

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In 1976 we reported our first autopsied case with diffuse Lewy body disease (DLBD), the term of which we proposed in 1984. We also proposed the term “Lewy body disease” (LBD) in1980. Subsequently, we classified LBD into three types according to the distribution pattern of Lewy bodies: a brain stem type, a transitional type and a diffuse type. Later, we added the cerebral type. As we have proposed since 1980, LBD has recently been used as a generic term to include Parkinson’s disease (PD), Parkinson’s disease with dementia (PDD) and dementia with Lewy bodies (DLB), which was proposed in 1996 on the basis of our reports of DLBD.
DLB is now known to be the second most frequent dementia following Alzheimer’s disease (AD).
In this paper we introduce our studies of DLBD and LBD.

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Original Article

Twin Xenopus laevis embryos appearing from flattened eggs

Eiji SATO

2014 Volume 90 Issue 8 Pages 307-312
Published: October 10, 2014
Released on J-STAGE: October 11, 2014

DOIhttps://doi.org/10.2183/pjab.90.307

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Remarkable progress has recently been made in molecular biology of double axis formation in Xenopus laevis. Leaving aside, for the time being, the problem of the gene expressions regulating Xenopus laevis development, here I show that pulse treatment could induce formation of a secondary axis in a fertilized Xenopus laevis egg. At 3 min after insemination, metal oxides were added to Xenopus fertilized eggs, and then twin embryos appeared. Zirconium oxide (ZrO₂) was the most effective metal oxide for producing twin embryos. ZrO₂ was added to the fertilized eggs, and 30 sec later, the eggs were dejellied with cysteine solution and washed within 7 min after insemination. The fertilized eggs began flattening at around 15 min after insemination. When the degree of flattening (the vertical length of the egg divided by the horizontal length) of the eggs at the 16- and 32-cell stages became less than 0.4 degrees, production of twin embryos occurred. Many flattened eggs at less than 0.4 degrees formed twin embryos. The third cleavage of eggs treated with metal oxides was meridional, while the normal third cleavage was horizontal.

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