Online ISSN : 1884-4111
Print ISSN : 0033-8303
ISSN-L : 0033-8303
Volume 63 , Issue 4
Showing 1-5 articles out of 5 articles from the selected issue
  • Akira TANAHARA, Fumiya NAKAEMA, Yoshitaka ZAMAMI, Takemitsu ARAKAKI
    2014 Volume 63 Issue 4 Pages 175-181
    Published: April 15, 2014
    Released: April 25, 2014
    Atmospheric measurements of naturally occurring radionuclides 210Pb and 7Be were conducted at ground level in the Okinawa Islands. Weekly data collected from Okinawa-jima over a seven-year period from 2004 to 2011 and Kume-jima and Minamidaito-jima over a two-year period from 2008 to 2010 are presented and discussed. The monthly averaged activity concentrations of 210Pb at three sites showed a one-peakseasonal variation the maximum peak appeared from autumn to springand 7Be showed a pattern similar to that of 210Pb. Activity concentrations of 210Pb and 7Be at Okinawa Islands ranged from 0.06 to 1.98 mBq/m3 with a mean of 0.80 mBq/m3 and from 1.45 to 15.1 mBq/m3 with a mean of 8.47 mBq/m3, respectively. Activity concentrations of both radionuclides at Kume-jima and Minamidaito-jima were almost the same as at Okinawa-jima. It is suggested that the relatively higher activity concentrations of both radionuclides in winter observed at the present three sites are affected by the air mass from the inland area of the Asian Continent.
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  • Susumu MINATO, Michikuni SHIMO
    2014 Volume 63 Issue 4 Pages 191-200
    Published: April 15, 2014
    Released: April 25, 2014
    In order to understand the mechanism of beach-to-beach variations in dose rates, measurements at 35 sand beaches were carried out along the Enshu-nada coast(a total of 140km). The sand samples were collected at 10 beaches to obtain the concentrations of potassium, uranium and thorium by means of Ge(Li) spectroscopy. Factors affecting the variation in dose rates were discussed, incorporating these data with data of coastal sea-bottom sediments taken by the Geological Survey of Japan.Two-dimensional measurements were performed at 50 locations each in two beaches near the Tenryu river mouth to know within-beach variations in detail. Contour maps of the data revealed a considerable regularity.It was found from simple analyses of the data collected in this work that the dose rate levels at beaches are affected by the distance from the river mouth, erosion or sedimentation of beach, and depth distribution of seawater.
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Review Article
  • Takahiko MATSUBARA
    2014 Volume 63 Issue 4 Pages 201-213
    Published: April 15, 2014
    Released: April 25, 2014
    At the end of the 20th century, the accelerating expansion of the universe was discovered. The cosmological term, which was introduced by Einstein and abandoned later by himself, attracts much attention recently for that reason. The cosmological term is unnatural in a theoretical viewpoint, and the idea of dark energy, which is a generalization of the cosmological term, was introduced and investigated. At the moment, theoretical understanding of the dark energy is fairly poor, and much observational data are required. In this article, recent research for the dark energy is reviewed.
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Serial Lecture
Basics and Applications of Mössbauer Spectrometry