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Volume 39 (1991)
- Issue 6 Pages 301-
- Issue 5 Pages 213-
- Issue 4 Pages 183-
- Issue 2 Pages 49-
- Issue 1 Pages 1-
Volume 39, Issue 6
Displaying 1-5 of 5 articles from this issue
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REGULAR PAPER
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Toshio NAKAMURA, Nobuyuki NAKAI, Akira TERASHIMA1991 Volume 39 Issue 6 Pages 301-313
Published: 1991
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSConcentrations of radionuclides such as 14C, 137Cs, 210Pb, and 214Pb, the contents of organic C and N, and 13C/12C ratios were measured for near surface sediments collected from Tilitso, a high altitude lake in Nepal, Himalayas. Living attached algae obtained from the streams feeding Lake Tilitso were also analyzed on their 14C abundances. The 14C concentration, Δ14C, was measured by direct detection of 14C atoms using a Tandetron accelerator mass spectrometer, on the acid-insoluble organic carbon that was extracted from each sediment or each algae sample. Activities of 137Cs, 210Pb, and 214Pb in the sediments were measured with a coaxial-well-type high-purity-germanium detector.
The sedimentation rate was estimated to be 0.56±0.27 cm y-1 by the 210Pb method. The content of carbon as acid-insoluble organic compounds was from 0.5 to 0.7%, and such carbon was depleted in 14C, yielding Δ14C values between -855±5 and -905±4‰ (apparent 14C ages between 15,520±250 and 18,910±360 y BP). Values of Δ14C for attached algae samples were also low, ranging from -463±31 to -701±29‰ (apparent ages from 4,980±460 to 9,700±780 y BP). The unexpectedly low 14C concentrations of these sediment and attached algae samples can be reasonably explained by considering geological and climatic environments around Lake Tilitso.View full abstractDownload PDF (943K)
TECHNICAL REPORT
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Hisao NAGAI, Mineo IMAMURA, Koichi KOBAYASHI, Kunio YOSHIDA, Hideo OHA ...1991 Volume 39 Issue 6 Pages 315-327
Published: 1991
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSThe technical details of accelerator mass spectrometry (AMS) developed at the University of Tokyo tandem facility are described for 10Be and 26Al measurements. Using a unique techique called the “internal beam monitor method”, isotopic ratios of 10Be/9Be and 26Al/27Al are determined without sequentially accelerating each isotope. 10Be and 26Al are injected to the accelerator in forms of negative ions, 10Be16O- and 26Al-, accompanied by the pilot beams of 9Be17O- and 10B16O-, respectively. The accelerated negative ions are converted to positively charged atomic ions by passing through a thin Ar gas in the stripping canal at the high voltage terminal of the accelerator. The triply charged ions, 10Be3+ and 26Al3+, are selected and counted by a heavy ion detector, while the currents of 9Be3+ and 16O2+, decomposed ions from the pilot beams, are simultaneously monitored with Faraday cups at the focal plane of the magnetic analyzer. The monitor beam currents allow the determination of the beam transmission efficiency through the accelerator. The data are presented to show an ability of precise measurement. The reproducibilities for repeated measurements in 24 hours were 1~3% and 2~5% and the sensitivities were 5×10-14 and 1×10-13, for 10Be and 26Al, respectively.View full abstractDownload PDF (960K)
REGULAR PAPERS
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Masuo ISHIGANE, Kimio ISA, Katsuhiko NISHIOKA1991 Volume 39 Issue 6 Pages 329-336
Published: 1991
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSWe have set up an ion trapping mass spectrometer for time resolved analysis from a conventional mass spectrometer (EI/MS), according to the technique established by Harrison et al. and Lifshitz. After comfirming ion trapping ability of this apparatus by use of toluene, the peaks of m/z 105, 106, and 107 (called A1, A2, and A3, respectively) of benzaldehyde have been investigated. Although the signal intensities of three peaks at delay time zero have been similar to those of the spectrum obtained by static method, they have different behaviors after 100 μs. In other words, the intensities of A1 and A3 have increased gradually with time, while, that of A2 has decreased. The aspects of increase and decrease have been noticed to be dependent on pressure of sample. These results can not be explainable by the well known fragmentation process. To explain these results, we are proposing that 1) electron capturing of molecular ions, 2) ion-molecule reactions of ions and molecules of benzaldehyde, and 3) metastable decomposition, take place in the ionic chamber.View full abstractDownload PDF (397K) -
Hisashi MORIKAWA, Yasuo IIDA, Yoshinori UWAMINO, Toshio ISHIZUKA1991 Volume 39 Issue 6 Pages 337-343
Published: 1991
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSThis paper describes the source of variation in the SIMS determination of impurities in an insulating powder sample mixed together with graphite powders for electrical conductivity. The predominant factors were the local charge buildup on the sample surface and the local distribution of impurities originally present in the graphite powders. The local charge buildup due to the inhomogeneity of the tablet sample resulted in obvious changes of the secondary ion energy distributions. The local distribution of impurities in the graphite powders caused the occasionally anomalous high values in the determination.View full abstractDownload PDF (457K)
NOTE
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Mitsuo TAKAYAMA, Taro NOMURA1991 Volume 39 Issue 6 Pages 345-350
Published: 1991
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSPositive ion fast-atom bombardment (FAB) mass spectra of some benzofuran or dihydrobenzopyran derivatives gave intense and predominant molecular ion M+· peaks even when a protic liquid matrix DTT/TG13, i.e., 1 : 3 (v/v) mixture of dithiothreitol (DTT) and thioglycerol (TG), is used. The above spectra were compared with the usual FAB mass spectra, showing a predominant protonated molecule MH+ peak, of the compounds containing such significant proton acceptors as carbonyl and carboxyl group. It was suggested that preferential formtion of M+· to MH+ ions is due to the structure of above derivatives, except for trolox (4), which do not contain the significant proton acceptor.
Furthermore, it was observed that the change of matrix from DTT/TG 13 to m-nitrobenzyl alcohol (m-NBA) increases the ratio of intensties I (M+·)/I(MH+) as a matrix effect.View full abstractDownload PDF (330K)
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