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Volume 73, Issue 3
Displaying 1-4 of 4 articles from this issue
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Yukio FUJINAWA, Kozo TAKAHASHI, Takumi MATSUMOTO, Noriaki KAWAKAMI1997 Volume 73 Issue 3 Pages 33-38
Published: 1997
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSVery low frequency (VLF) band electromagnetic signals1)-11) seem to be one of the most plausible precursory phenomena in the various kinds of anomalous electric, magnetic and electromagnetic field changes preceding earthquakes. In particular the number of VLF pulse-like signals has been known to increase clearly just before earthquakes2), 4), 9), 10) possibly providing data on the occurrence time of impending earthquake. However, there is a lack of knowledge as to how to predict where the earthquake will strike. Also, it is difficult to establish the mechanisms of emissions induced by natural geophysical activity: earthquakes and volcanic eruptions. There are two main hypotheses regarding the generation mechanism of the VLF waves: the first proposes that electromagnetic waves are directly emitted from the hypocentral region, 4), 10), 12)-15) while the second proposes that the emission is a result of electric charge redistribution in the Earth's atmosphere. 16)-18) Here, we present source region data for VLF pulse-like signals showing that the VLF emission does not originate around the epicenter but from regions of atmosphere above the epicenter spreading horizontally in several hundreds kilometers. Our data suggest that the VLF emission is produced by the electromagnetic processes in the Earth's atmosphere up to the ionosphere.View full abstractDownload PDF (5214K) -
A Peculiarity of the Fourth Lanthanide Tetrad under a Certain ConditionAkimasa MASUDA, Junji SHIMODA1997 Volume 73 Issue 3 Pages 39-43
Published: 1997
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSVertical profiles of three separate lanthanide tetrad effects, ABEXEL, ABEX-3 and ABEX-4 in two seawater columns representing the subtropical and subpolar areas of the North West Pacific have been studied in connection with the hydrographical data. The depth profiles of ABEX-4 show remarkable difference between the subtropical and subpolar columns. The change of ABEX-4 between 640 and 1000m at the subtropical site appears to be related to the discontinuous change in salinity between the corresponding depths. Besides, in general the gross features of the depth profile of ABEX-4 appears different from those of ABEXEL and ABEX-3.View full abstractDownload PDF (566K) -
Eizo NAKAMURA, Ikuo KUSHIRO1997 Volume 73 Issue 3 Pages 44-47
Published: 1997
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSDiffusivities of 11 rare earth elements (REE) and Ba in jadeite (NaAlSi2O6) and diopside (CaMgSi2O6) melts have been measured at pressures between 10 and 20kbar. In jadeite melt, diffusivities of REE increase regularly with increasing their ionic radii, light REE (e.g., La and Ce) diffuse faster than heavy REE (e.g., Yb and Lu) by about 30%, Eu diffuses faster by factor of 8 to 12 than other REE under reducing conditions, and diffusivities of REE increase with increasing pressure at constant temperature. In diopside melt, diffusivities of REE are nearly the same as that of Ca and decrease with increasing pressure. The present study demonstrates that diffusion process in magma should change the relative abundances of REE and also generate Eu anomalies without involvement of plagioclase feldspar. This diffusion-induced process is a newly recognized mechanism of changing the relative REE abundances in magmas and generating Eu anomalies, and it must be taken into account in interpreting the REE abundance patterns of igneous rocks.View full abstractDownload PDF (637K) -
Kazuhiro IMAI, Takeshi FUKUSHIMA, Tomofumi SANTA, Hiroshi HOMMA, Juko ...1997 Volume 73 Issue 3 Pages 48-52
Published: 1997
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSAfter the intravenous administration of 14C-D-aspartic acid (Asp) into Sprague-Dawley rats (male, 7-week-old), the distribution and elimination of radioactivity was investigated by the whole body autoradiography. High radioactivities were detected in pineal gland, pituitary gland and salivary gland at 30min after administration. The other tissues detected were liver, lung, adrenal gland, pancreas and spleen where D- Asp was reported to occur naturally. After 24hr, the radioactivities were still detected at high levels in the pineal, pituitary and salivary glands. The data suggested the natural occurrence of D-Asp in salivary gland. After careful examination utilizing fluorescent derivatization and chiral separation by high-performance liquid chromatography, the presence of D-Asp was, for the first time, demonstrated in salivary gland in situ, the concentration of which was 7.85±1.0nmol/g. The administration of 14C-L-Asp was also carried out. The data suggested that D-Asp in the circulating blood is one of the sources of the tissue D-Asp.View full abstractDownload PDF (1831K)
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