PSP-toxicification of the carnivorous gastropod Rapana venosa inhabiting the estuary of Nikoh River, Hiroshima Bay, Hiroshima Prefecture, Japan

During surveillance on the toxicity of invertebrates such as bivalves inhabiting the coasts of Hiroshima Bay in 2001 and 2002, the carnivorous gastropod rapa whelk Rapana venosa collected in the estuary of Nikoh River, was found to contain toxins which showed paralytic actions in mice; the maximum toxicities (as paralytic shellfish poison, PSP) were 4.2 MU/g (May 2001) and 11.4 MU/g (April 2002). Their total toxicities were 224 and 206 MU/viscera of one specimen throughout the monitoring period. Attempts were made to identify the toxic principle in the gastropod. The viscera were extracted with 80% ethanol acidified with acetic acid, followed by defatting with dichloromethane. The aqueous layer obtained was treated with activated charcoal and then applied to a Sep-Pak C18 cartridge. The unbound toxic fraction was analyzed by high-performance liquid chromatography techniques. The gastropod toxin was rather unexpectedly identified as PSP. It was comprised of high toxic component (gonyautoxin-3; GTX3, GTX2, saxitoxin; STX) as the major components, which accounted for approximately 91 mol% of all components along with C1 and C2, which are N-sulfocarbamoyl derivatives. Judging from their toxin patterns, it is suggested that the PSP toxification mechanism of the gastropod that PSP toxins produced by phytoplankton such as Alexandrium tamarense, are transferred to and accumulated in plankton feeders such as the short-necked clam, and then transferred to this carnivorous rapa whelk R. venosa through predation.     

Numerical experiments on low-frequency fluctuations on a submerged coastal reef

Low-frequency fluctuations on a reef coast are studied through a numerical model based on nonlinear conservation equations of mass and momentum. The model is used to investigate the long wave generation and propagation phenomena under both breaking and non-breaking incident short wave groups. The effects of incident wave characteristics and reef topography on the long wave phenomena are discussed. The results show that the long wave elevations on reef coasts are substantial, which explains the large water level fluctuations observed at certain occasions.     

The Intra-Seasonal Oscillation and its control of tropical cyclones simulated by high-resolution global atmospheric models

Project Athena is an international collaboration testing the efficacy of high-resolution global climate models. We compare results from 7-km mesh experiments of the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and 10-km mesh experiments of the Integrated Forecast System (IFS), focusing on the Intra-Seasonal Oscillation (ISO) and its relationship with tropical cyclones (TC) among the boreal summer period (21 May–31 Aug) of 8?years (2001–2002, 2004–2009). In the first month of simulation, both models capture the intra-seasonal oscillatory behavior of the Indian monsoon similar to the observed boreal summer ISO in approximately half of the 8-year samples. The IFS simulates the NW–SE-oriented rainband and the westerly location better, while NICAM marginally reproduces mesoscale organized convective systems and better simulates the northward migration of the westerly peak and precipitation, particularly in 2006. The reproducibility of the evolution of MJO depends on the given year; IFS simulates the MJO signal well for 2002, while NICAM simulates it well for 2006. An empirical orthogonal function analysis shows that both models statistically reproduce MJO signals similar to observations, with slightly better phase speed reproduced by NICAM. Stronger TCs are simulated in NICAM than in IFS, and NICAM shows a wind-pressure relation for TCs closer to observations. TC cyclogenesis is active during MJO phases 3 and 4 in NICAM as in observations. The results show the potential of high-resolution global atmospheric models in reproducing some aspects of the relationship between MJO and TCs and the statistical behavior of TCs.     

Distribution of fault rocks in the fracture zone of the Nojima Fault at a depth of 1140 m: Observations from the Hirabayashi NIED drill core

Abstract Characteristics of deformation and alteration of the 1140 m deep fracture zone of the Nojima Fault are described based on mesoscopic (to the naked eye) and microscopic (by both optical and scanning electron microscopes) observations of the Hirabayashi National Research Institute for Earth Science and Disaster Prevention (NIED) drill core. Three types of fault rocks; that is, fault breccia, fault gouge and cataclasite, appear in the central part of the fault zone and two types of weakly deformed and/or altered rocks; that is, weakly deformed and altered granodiorite and altered granodiorite, are located in the outside of the central part of the fault zone (damaged zone). Cataclasite appears occasionally in the damaged zone. Six distinct, thin foliated fault gouge zones, which dip to the south-east, appear clearly in the very central part of the fracture zone. Slickenlines plunging to the north-east are observed on the surface of the newest gouge. Based on the observations of XZ thin sections, these slickenlines and the newest gouge have the same kinematics as the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake), which was dextral-reverse slip. Scanning electron microscopy observations of the freeze-dried fault gouge show that a large amount of void space is maintained locally, which might play an important role as a path for fluid migration and the existence of either heterogeneity of pore fluid pressure or strain localization.     

An interpretation of the 1883 cataclysmic eruption of Krakatau from geochemical studies on the partial melting of granite

Pumice flow from the 1883 Krakatau eruption significantly differs in both mineral and chemical compositions from any other volcanic rocks or ejecta of the Krakatau group, which belong to the tholeiitic series. Lithic fragments of granitic Rock, discovered in the pumice flow, are similar to West Malayan granitic rocks. No other granitic rock occurs throughout the Krakatau group, therefore, we consider that the granitic fragments came from the underlying complex at depths, where they were captured as foreign materials by the magma.It is possible that sialic crustal materials plunged into depths along a peculiar tectonic structure located at the Sunda Strait, which appears to be a sheared portion caused by deformation of the Sunda arc due to differential movement between the Indo-Australian oceanic plate and the Eurasian continental crust. The crustal materials were partially melted and produced a magma of granitic composition. The magma was mixed with or assimilated by an ascending basaltic magma originating probably from the upper mantle. This resulted in a dacitic magma distinctly dominant in silica, alkalis and volatile components, and the 1883 Krakatau eruption, characterized by the pumice flow of dacitic composition, took place.     

Estimation of Response Spectra in the Severely Damaged Area During the 1995 Hyogo-Ken Nambu Earthquake

We calculated theoretical acceleration response spectra at the ground surface in the region near the 1995 Hyogo-ken Nambu earthquake source based on the spectral moment method. To estimate earthquake motion on the ground surface, a formula of earthquake motion at base rock level was derived. The amplification effect of the ground was introduced by using multiple reflection theory. Theoretically estimated response spectrum were modified by the response spectra calculated using observed earthquake motions.     

Temperature correlations in a compact hyperbolic universe

The effect of a non-trivial topology on the temperature correlations of the cosmic microwave background (CMB) in a small compact hyperbolic universe with volume comparable to the cube of the curvature radius is investigated. Because the bulk of large-angle CMB fluctuations are produced at the late epoch in low-Ω₀ models, the effect of a long-wavelength cut-off owing to the periodic structure does not lead to significant suppression of large-angle power as in compact flat models. The angular power spectra are consistent with COBE data for Ω₀0.1.     

基于图像相关分析的土体剪切带识别方法

提出了一种基于数字照相量测和图像相关性分析技术的土体剪切带识别方法。首先,在模型试验中,用数码相机采集土体全程变形图像序列;接着,在图像全局观测范围内粗略搜索到剪切带发生的大致区域;然后,布置跨越剪切区域的多对测点线,进行局部范围精密搜索,识别出剪切带的准确位置与形状, 并确定剪切带的边界点。与在模型上描画网格线等传统方法相比,该法操作简单,量测准确,适用于模型试验中岩土材料的剪切带识别及其厚度、倾角、带内变形和演变过程等特性的试验研究;最后,给出了一个大型砂土剪切试验中的应用实例。结果表明,基于图像相关分析的识别土体剪切带的方法是可行而有效的。