Proceedings of the Japan Academy, Series B
Online ISSN : 1349-2896
Print ISSN : 0386-2208
ISSN-L : 0386-2208
Volume 71 , Issue 6
Showing 1-9 articles out of 9 articles from the selected issue
  • Yoshiyuki IIZUKA, Eizo NAKAMURA
    1995 Volume 71 Issue 6 Pages 159-164
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    In order to examine the behavior of elements under the control of aqueous fluid through slab-mantle interactions, a series of high-pressure and high-temperature experiments was carried out at subsolidus temperature, 850°C. The starting materials consist of two portions: metabasite from blueschist as a slab material and olivine as a mantle material. The metabasite was directly placed on the olivine and sealed within an Au tube. At 3 and 6GPa corresponding to 100 and 200km in depth, respectively, the slab material was changed from blueschist to rutile-bearing eclogite. Observed phases in the mantle side were primary olivine and enstatite formed by the reaction between olivine and SiO2-rich aqueous fluid from the slab side. At 8GPa, the slab material was further transformed to rutile-free eclogite, and phases occurred in the mantle side were titanoclinohumite in addition to olivine and enstatite. The titanoclinohumite was formed by the reaction between olivine and Ti-bearing aqueous fluid which was supplied from the slab side. The titanoclinohumite is essentially identical in chemical composition to those principally occurring in kimberlite xenoliths. Because the Ti-phase is a host reservoir of HFSE, the formation of titanoclinohumite at 8GPa corresponding to 250km in depth suggests that the aqueous fluid can be a carrier of HFSE from the subducting slab to the upper mantle, and thus the source region of kimberlite magma could be impregnated by the interaction between mantle peridotite and the HFSE-bearing aqueous fluid from the subducting slab.
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  • Akimasa MASUDA
    1995 Volume 71 Issue 6 Pages 165-169
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    Considerations are given to the third ionization potentials of lanthanides with general regularities and certain irregularities. Main attention is paid to those irregularities, which are found to be explicable in terms of stabilization energy due to steric symmetry of configuration of 4f electrons. It is reasoned that stabilization energy for Ho is about twice that for Nd, because Nd is sterically symmetrical with respect to the unpaired f electron system only, while Ho is sterically symmetrical concerning both the unpaired and paired systems of f electrons. The observation about the ionization potential in question can be regarded to be consistent with this inference. Small differences in ionization potential between Nd and Pm and between Ho and Er are also reasonable. Further, the fact that the difference between Ho and Er is smaller than that between Nd and Pm is in line with the assumed configurations of 4f electrons. Briefly, a kind of deceleration of general tendency of increase of ionization potential takes place at Nd-Pm for light lanthanides and at Ho-Er for heavy lanthanides, owing to the stabilization energy ascribable to the three-dimensional symmetry of major directions of f electron clouds.
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  • Ryuichi SUGISAKI, Yoshikuni HORIUCHI, Kenichiro SUGITANI, Mamoru ADACH ...
    1995 Volume 71 Issue 6 Pages 170-174
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    Comparative inspection of Archean ferruginous cherts with Phanerozoic cherts shows that the former precipitated from acid-water hydrothermally supplied during intensive early Precambrian volcanism. The pH of the water is inferred to have been around 4 where Al dissolves, and Ti and Zr do not. The peculiar geochemical environment seems to have been widespread in Archean to early Proterozoic greenstone basins when tremendous volume of banded iron formation (BIF) formed. This suggests that the acid seas were neutralized after the BIF deposition probably during the middle to late Proterozoic; this change of pH in sea water may have promoted the deposition of carbonate rocks.
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  • Masaaki KOJIMA, Kiyohiko NAKAJIMA, Masanobu TSUCHIMOTO, Paul M. TREICH ...
    1995 Volume 71 Issue 6 Pages 175-178
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    {N, N'-Disalicylidene-(R, R)-1, 2-Biphenyl-1, 2-ethanediamine}oxovanadium(IV) crystallized in two different forms, green (from chlorinated solvents) and orange (from acetonitrile). X-ray structure analyses revealed that the green form contains mononuclear square pyramidal molecules of the complex, while the orange form has a polynuclear linear chain structure. The green crystals turn orange when heated at 120°C for a few minutes. The orange crystals turn green when exposed to chloroform vapor, and the green crystals turn orange when exposed to acetonitrile vapor. The orange complex shows piezochromism (mechanochromism); its color changes to green on grinding.
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  • Munehiro KIKUYAMA, Kiyo SHIMADA, Kaoru KATOH, Masashi TAZAWA
    1995 Volume 71 Issue 6 Pages 179-182
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    When cells of Nitella flexilis are subjected to transcellular osmosis or osmotic swelling, cytosolic free Ca2+ ([Ca2+]c) increases. Ca2+ is thought to be released from internal stores due to hydration of the cytoplasm. In the present study we demonstrated that the hydration-induced Ca2+ release (HICR) can occur in isolated cytoplasm whether or not it contains chloroplasts.
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  • Sakae YAMAMURA
    1995 Volume 71 Issue 6 Pages 183-188
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    Although the synchronous machine has been in use for a long time, it seems that their analysis has not reached an adequate and sufficient state, especially in transient state analysis. It has more or less saliency of poles, which makes their inductances time-variant and their analysis complicated. The conventional theories are based on the two-axis method. They involve complicated variable transformations, which are not so successful in analysing the machine. The author proposed the spiral vector method and obtained good results in analysis of electric circuits and machines with it. Now the method will be applied to analysis of the synchronous machine, to improve the confused situation. It is not only the most important building block of the large electric power transmission network, but has begun to play a new important role as the AC control motor, which is sometimes called the brushless DC motor.
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  • Makoto KITO, Reiko URADE
    1995 Volume 71 Issue 6 Pages 189-192
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    Novel microsomal cysteine proteases, ER-60 and ER-72 proteases, were purified. ER-60 and ER-72 proteases are defined as a new type of cysteine protease localized in the endoplasmic reticulum. The open reading frame of ER-60 protease cDNA encodes 505 amino acid residues. The amino acid sequence was similar to that of phosphoinositide-specific phospholipase Cα, but the sequence corresponding to Ile232-Ile240 of ER-60 protease was different from the corresponding region of phosphoinositide-specific phospholipase Cα in the amino acid species and numbers. From the results of analysis with cysteine protease inhibitors and the distribution in organs, ER-60 and ER-72 proteases are assumed to participate in qualitative and quantitative control of ER synthesized proteins.
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  • Yoshinori NITTA, Masashi SUZUKI
    1995 Volume 71 Issue 6 Pages 193-197
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    A considerable number of prokaryotic transcription factors belong to the LysR family. By comparison with the amino acid sequence of the putative DNA-binding domain (DBD) of BirA, for which the crystal structure has been determined, we predict that the LysR DBD has three α -helices and three β-strands, and that the third α-helix binds to DNA. Contacts between DNA bases and amino acid residues in the predicted recognition helix are discussed in comparison with those found in crystal structures of DNA-transcription factor complexes.
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  • Hitoshi SAKASHITA, Takahiko SAKUMA, Yoshiko AKITOMO, Tadayasu OHKUBO, ...
    1995 Volume 71 Issue 6 Pages 198-201
    Published: 1995
    Released: October 13, 2006
    JOURNALS FREE ACCESS
    NMR studies have revealed the mechanism of a functional switch in the Escherichia coli Ada protein, which converts the DNA methyltransferase to a transcriptional regulator. The Ada protein acquires its ability to bind specific DNA sequences after an irreversible methyl transfer to its own cysteine residue (Cys69) from methyl-phosphotriesters within the alkylated DNA. NMR analysis have revealed that the segment from residues 102 to 123 forms a helix-turn-helix structure, and a site-directed mutagenesis study has identified the second helix to play a crucial role in specific recognition of DNA. NMR experiments on the methylated protein-DNA complex showed that although the major contacts are made by residues within the recognition helix, the S-methyl group at Cys69 come into direct contact with the cognate DNA. Therefore, the direct contact of this region after methylation is the “switch” which converts the Ada protein from a nonspecific DNA binding form to a transcription factor.
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