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71.
Noboru Kaneko Kazuhiko Morita Tetsuya Satoh Kiyotaka Toyama Masaki Nishimura Makoto Maekawa 《Astrophysics and Space Science》2000,274(3):601-641
We reanalyze the propagation of one-dimensional small-amplitude disturbances of given real frequency ω in a radiating and
scattering grey medium using the Eddington approximation, which has been studied previously by us (Kaneko et al., 1976). Numerical results reveals three frequency regimes to be distinguished, and two wave modes always appear in each frequency
regime. The governing equations and analytic solutions are derived for all wave modes using Whitham's method modified into
quadratic form and approximate methods based on radiation thermodynamics. In the high-frequency regime appear the radiation-wave
and adiabatic sound modes, which are damped by opacity and radiative cooling, respectively. Wave patterns in the intermediate-frequency
and low-frequency regimes depend critically on the importance of radiation, for which the criterion is given in terms of the
ratio of total specific heats at constant pressure and constant volume. When the radition overwhelms the matter (radiation-dominated
case), the radiative mode in the intermediate-frequency regime is the constant-volume diffusion mode. When the matter overwhelms
the radiation (matter-dominated case), damped radiation-wave and damped radiation-diffusion modes newly appear between the
radiation-wave and constant-volume diffusion modes. The acoustic mode in the intermediate-frequency regime is the isothermal
sound mode,which is damped by radiative cooling at higher frequencies and by radiation-thermal drag force at lower frequencies.
Two modes appearing in the low-frequency regime are the isentropic radiation-acoustic and constant-pressure diffusion modes.
The absorption coefficient derived for the former is shown to be a radiation-thermodynamic extension of that of Landau and
Lifshitz (1987). The transition frequencies between all adjacent two modes are also derived to discuss the implications of
them.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
72.
To determine recent interannual variations in the planktonic ecosystem of the slope water south of Japan, an area between 1000 m isobath on the continental slope and assumable Kuroshio front, in reference to preceding reports on the Kuroshio, we examined interannual variations of physical factors, sea surface chlorophyll concentration (SSChl), size-fractioned copepod biomass and the abundance of Calanus sinicus, one of the dominant copepods in the region, in February from 1990 to 2002. In the slope water, SSChl concentration had generally shown a higher value than in the Kuroshio and increase of the SSChl in both areas started in February but lasted longer in the slope water. The regional distribution of copepod biomass and C. sinicus abundance was similar to that of phytoplankton in that they were distributed more densely in the slope water than in the Kuroshio, reflecting assumed higher nutrient supply. The interannual variation in sea surface temperature in the slope water was explained by the rise of air temperature in 1998, a strong El Niño year, and subsequent change in the Kuroshio path (1999–2001). The interannual variation of the planktonic community, i.e. sea surface chlorophyll concentration and copepod biomass, was attributed to the effects of those physical events through the direct effect of local temperature and/or variation in surface irradiance, except for a prominent increase of copepods in the slope water in 2000. The effect of interannual change in the vertical mixing, suggested in previous studies, was not apparent in February, when the primary production is not limited by nutrient concentration which would be more important in regulating biological production in later months. 相似文献
73.
Masahiro Kayama Hirotsugu Nishido Shin Toyoda Kosei Komuro Adrian A. Finch Martin R. Lee Kiyotaka Ninagawa 《Physics and Chemistry of Minerals》2013,40(7):531-545
Cathodoluminescence (CL) spectra of unirradiated, He+ ion-implanted and electron-irradiated plagioclase minerals contain the following emission bands: (1) below 300 nm due to Pb2+, (2) at ~320 and ~350 nm to Ce3+, (3) at 380–420 nm to Eu2+, Ti4+ and/or Al–O?–Al/Ti defects, (4) at 560–580 nm to Mn2+ and (5) at 720–760 nm to Fe3+. During the implantation of He+ ion, much of their energy may be dissipated by partial destruction and strain of the feldspar framework, resulting in quenching of CL. Deconvolution of CL spectra acquired from albite and oligoclase reveals an emission component at 1.86 eV (666 nm) assigned to a radiation-induced defect center associated with Na+ atoms. As its intensity increases with radiation dose, this emission component has potential for geodosimetry and geochronometry. Electron irradiation causes Na+ migration in plagioclase, and then a considerable reduction in intensity of emissions assigned to impurity centers, which is responsible for an alteration in the energy state or a decrease in luminescence efficiency following the change of activation energy. Emission intensity at 1.86 eV positively correlates with electron irradiation time for unimplanted and He+ ion-implanted albite and oligoclase, but negatively for the implanted albite above 1.07 × 10?4 C/cm2. It implies that radiation halo produced by α-particles should not be measured using CL spectroscopy to estimate β radiation dose on albite in the high radiation level. 相似文献
74.
Suguru Takahashi Eiji Ohtani Hidenori Terasaki Yoshinori Ito Yuki Shibazaki Miho Ishii Ken-ichi Funakoshi Yuji Higo 《Physics and Chemistry of Minerals》2013,40(8):647-657
The phase and melting relations of the C-saturated C–Mg–Fe–Si–O system were investigated at high pressure and temperature to understand the role of carbon in the structure of the Earth, terrestrial planets, and carbon-enriched extraterrestrial planets. The phase relations were studied using two types of experiments at 4 GPa: analyses of recovered samples and in situ X-ray diffractions. Our experiments revealed that the composition of metallic iron melts changes from a C-rich composition with up to about 5 wt.% C under oxidizing conditions (ΔIW = ?1.7 to ?1.2, where ΔIW is the deviation of the oxygen fugacity (fO2) from an iron-wüstite (IW) buffer) to a C-depleted composition with 21 wt.% Si under reducing conditions (ΔIW < ?3.3) at 4 GPa and 1,873 K. SiC grains also coexisted with the Fe–Si melt under the most reducing conditions. The solubility of C in liquid Fe increased with increasing fO2, whereas the solubility of Si decreased with increasing fO2. The carbon-bearing phases were graphite, Fe3C, SiC, and Fe alloy melt (Fe–C or Fe–Si–C melts) under the redox conditions applied at 4 GPa, but carbonate was not observed under our experimental conditions. The phase relations observed in this study can be applicable to the Earth and other planets. In hypothetical reducing carbon planets (ΔIW < ?6.2), graphite/diamond and/or SiC exist in the mantle, whereas the core would be an Fe–Si alloy containing very small amount of C even in the carbon-enriched planets. The mutually exclusive nature of C and Si may be important also for considering the light elements of the Earth’s core. 相似文献
75.
Masaya Masayoshi Saito Kiyotaka Tanikawa 《Celestial Mechanics and Dynamical Astronomy》2010,107(4):397-407
In the present paper, in the rectilinear three-body problem, we qualitatively follow the positions of non-Schubart periodic
orbits as the mass parameter changes. This is done by constructing their characteristic curves. In order to construct characteristic
curves, we assume a set of properties on the shape of areas corresponding to symbol sequences. These properties are assured
by our preceding numerical calculations. The main result is that characteristic curves always start at triple collision and
end at triple collision. This may give us some insight into the nature of periodic orbits in the N-body problem. 相似文献
76.
77.
Sakiko Orui Sakaguchi Kiyotaka Takishita Tomoaki Goto Haruka Shibata Shigeaki Kojima Shinji Tsuchida Hiroshi Kitazato Katsunori Fujikura 《Journal of Oceanography》2014,70(5):457-462
Body size, age, and population genetic structure of the broadbanded thornyhead Sebastolobus macrochir inhabiting areas off the Pacific coast of Tohoku and off Abashiri, the Sea of Okhotsk, Japan, were analyzed. On the basis of significant differences in body size (growth) between certain year classes at Tohoku and Abashiri, it appears that S. macrochir does not migrate extensively after settlement and subsists on food within the settled environment. Meanwhile, no genetic isolation was observed between the populations at these two sites. Thus, it is highly likely that its pelagic egg balloons, larvae, and juveniles widely disperse and migrate before settlement. 相似文献
78.
Shin Ozawa Masaaki Miyahara Eiji Ohtani Makoto Kimura Yoshinori Ito 《Polar Science》2011,4(4):550-557
Yamato 984028 (Y984028) is a newly identified lherzolitic shergottite, recovered from the Yamato Mountains, Antarctica, in 1999. As part of a consortium study, we conducted petrographic observations of Y984028 and its melt vein in order to investigate its shock metamorphism. The rock displays the typical non-poikilitic texture of lherzolitic shergottite, characterized by a framework of olivine, minor pyroxene (pigeonite and augite), and interstitial maskelynite. Shock metamorphic features include irregular fractures in olivine and pyroxene, shock-induced twin-lamellae in pyroxene, and the complete conversion of plagioclase to maskelynite, features consistent with those found in other lherzolitic shergottites. The melt vein is composed of coarse mineral fragments (mainly olivine) entrained in a matrix of fine-grained euhedral olivine (with several modes of compositional zoning) and interstitial glassy material. Some coarse olivine fragments consist of an assemblage of fine-grained euhedral to subhedral olivine crystals, suggesting shock-induced fragmentation, recrystallization, and/or a process of sintering. The implication is that the fine-grained olivine crystals in the matrix of the melt vein represent complicated crystallization environments and histories. 相似文献
79.
A. D. Chanyshev K. D. Litasov A. F. Shatskiy J. Furukawa E. Ohtani 《Geochemistry International》2014,52(9):767-772
The first results of study of stability of diverse polycyclic aromatic hydrocarbons at around 7 GPa and 773–1073 K are reported. Experiments were carried out in hydraulic multi-anvil presses. The run products after quenching were analyzed using a method of matrix-assisted laser desorption-ionization (MALDI). The formation of polymers of starting matters was determined at 7 GPa and 773–883 K. The polymers are characterized by atomic masses up to 5000 Da, that are multiple by masses of starting matters. At higher temperatures (873–1073 K), the selected PAHs and their polymers become unstable. The decomposition temperature of PAHs and their polymers exclude their stability under Earth’s mantle conditions. The studies could be of great significance for the low-temperature near-surface geodynamics of small and large planetary bodies, which supposedly contain hydrocarbon compounds. 相似文献
80.