Bar dissolution in non-spherical halos     

Makoto Ideta 《Astrophysics and Space Science》2003,284(2):531-534

Dynamical evolution of N-body bars embedded in spherical and prolate dark matter halos is investigated. In particular, the configuration such that galactic disks are placed in the plane perpendicular to the equatorial plane of the prolate halos is considered. Such a configuration is frequently found in cosmological simulations. N-body disks embedded in a fixed external halo potential were simulated, so that the barred structure was formed via dynamical instability in initially cool disks. In the subsequent evolution, bars in prolate halos dissolved gradually with time, while the bar pattern in spherical halos remained almost unchanged until the end of simulations. The e-folding time of bars suggest that they could be destroyed in a time smaller than a Hubble time. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Photometric study of new southern SU UMa-type dwarf novae and candidates: V877 Ara, KK Tel and PU CMa     

Taichi Kato  Roland Santallo  Greg Bolt  Tom Richards  Peter Nelson  Berto Monard  Makoto Uemura  Seiichiro Kiyota  Rod Stubbings  rew Pearce  Tsutomu Watanabe  Patrick Schmeer  Hitoshi Yamaoka 《Monthly notices of the Royal Astronomical Society》2003,339(3):861-871

  相似文献   

New compositional and optical data for antimonian and bismuthian varieties of hemusite from Japan     

Dr. M. Shimizu  Dr. C. J. Stanley  Dr. A. J. Criddle  Dr. A. Kato  Dr. S. Matsubara 《Mineralogy and Petrology》1991,45(1):11-17

Summary New compositional and optical data are reported for antimonian and antimonianbismuthian varieties of hemusite from epithermal Au-Ag-Cu deposits in Japan. The empirical formula for the antimonian variety, from the Iriki mine is: (Cu_5.83Fe_0.14Ag_0.01)_5.98Mo_1.03(Sn_0.54Sb_0.41Te_0.03Bi_0.02)_1.00(S_7.85Se_0.15)_8.00, and that of the Sb-Bi variety from the Kawazu mine is: (Cu_5.84Fe_0.14Ag_0.01)_5.99Mo_1.03(Sn_0.82Sb_0.11Bi_0.l0Te_0.04)_1.07(S_7.80Se_0.12)_7.92. The theoretical formula of hemusite is Cu⁺ ₄Cu²⁺ ₂MO⁴⁺Sn⁴⁺S₈, whilst the most probable formula of the Iriki hemusite is Cu⁺ _4.5CU²⁺ _1.5Mo⁴⁺Sn⁴⁺ _0.5Sb⁵⁺ _0.5S₈, with Sb⁵⁺ substituting for Sn⁴⁺ and forming (SbS₄)^3– tetrahedra as might be expected, given that the metal to sulphur ratio is 1, and given the sphalerite-like structure of the mineral. However Bi³⁺ cannot be so accommodated, resulting in a deficiency in (S + Se) for Kawazu hemusite. Reflectance spectra for both are compared with those of the tungsten analogue (compositional) of hemusite, kiddcreekite. The relationship between hemusitesensu stricto and these newly reported varieties is discussed in terms of simple and coupled chemical substitutions, and inferences are drawn on the valency of Sb, Bi, Mo and Cu in the hemusite structure.

---

Neue chemische und optische Daten für antimon- und bismuthführende Varietäten von Hemusit aus Japan

Zusammenfassung Neue chemische und optische Daten für antimon- und bismuthführende Hemusite auf epithermalen Au-Ag-Cu Lagerstätten in Japan werden vorgelegt. Die empirische Formel für die antimon-führende Varietät aus der Iriki-Mine ist: (Cu_5.83Fe_0.14Ag_0.01)_5.98Mo_1.03(Sn_0.54Sb_0.41Te_0.03Bi_0.02)_1.00 (S_7.85Se_0.15)_8.00, und die der Sb-Bi Varietät aus der Kawazu Mine ist: (Cu_5.84Fe_0.14Ag_0.01)_5.99M0_1.03(Sn_0.82Sb_0.11Bi_0.l0Te_0.04)_1.07 (S_7.80Se_0.12)_7.92. Die theoretische Formel von Hemusit ist Cu⁺ ₄Cu²⁺ ₂Mo⁴⁺Sn⁴⁺S₈, während die wahrscheinlichere Formel für den Hemusit von Iriki Cu⁺ ₄Cu²⁺ _1.5Mo⁴⁺Sn⁴⁺ _0.5Sb⁵⁺ _0.5S₈, mit Sb⁵⁺ an der Stelle von Sn⁴⁺, das(SbS₄)^3– Tetraeder bildet, wie zu erwarten ist, unter der Voraussetzung, da das Metall zu Schwefelverhältnis 1 und die Struktur sphaleritähnlich ist. Bi³⁺ kann jedoch nicht in dieser Weise untergebracht werden, und das führt zu einem Mangel an (S + Se) für den Hemusit von Kawazu. Die Reflektions-Spektren beider Minerale werden mit denen des Wolfram-Equivalents von Hemusit (Kiddcreekit) verglichen. Die Beziehung zwischen Hemusitsensu stricto und diesen jetzt beschriebenen Varietäten wird auf der Basis einfacher und gekoppelter chemischer Substitution diskutiert. Auf dieser Basis werden Schlüsse auf die Valenz von Sb, Bi Mo und Cu in der Hemusit-Struktur gezogen.

  相似文献   

CS,C34S,and CH3OH observations of the molecular cloud associated with NGC 7538     

Osamu Kameya  Tatsuhiko Hasegawa  Naomi Hirano  Munezo Seki  Makoto Tosa  Yoshiaki Taniguchi  Keiya Takakubo 《Astrophysics and Space Science》1986,118(1-2):449-451

CS(J=1–0), C³⁴S(J=1–0), and CH₃OH(1₀–0₀A and E) emission lines in the core region of molecular cloud associated with NGC 7538 have been surveyed at angular resolution of 33. Distribution of CS column density shows two prominent peaks. Both blue and red wings in CS line are most prominent at 30 northwest of IRS 11.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.This work was carried out under the common use observation program at the Nobeyama Radio Observatory (NRO). NRO, a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open to outside users.  相似文献   

An experimental study of the grain-scale processes of peridotite melting: implications for major and trace element distribution during equilibrium and disequilibrium melting   总被引：1，自引：0，他引：1  

Mauro Lo Cascio  Yan Liang  Nobumichi Shimizu  Paul C. Hess 《Contributions to Mineralogy and Petrology》2008,156(1):87-102

The grain-scale processes of peridotite melting were examined at 1,340°C and 1.5 GPa using reaction couples formed by juxtaposing pre-synthesized clinopyroxenite against pre-synthesized orthopyroxenite or harzburgite in graphite and platinum-lined molybdenum capsules. Reaction between the clinopyroxene and orthopyroxene-rich aggregates produces a melt-enriched, orthopyroxene-free, olivine + clinopyroxene reactive boundary layer. Major and trace element abundance in clinopyroxene vary systematically across the reactive boundary layer with compositional trends similar to the published clinopyroxene core-to-rim compositional variations in the bulk lherzolite partial melting studies conducted at similar P–T conditions. The growth of the reactive boundary layer takes place at the expense of the orthopyroxenite or harzburgite and is consistent with grain-scale processes that involve dissolution, precipitation, reprecipitation, and diffusive exchange between the interstitial melt and surrounding crystals. An important consequence of dissolution–reprecipitation during crystal-melt interaction is the dramatic decrease in diffusive reequilibration time between coexisting minerals and melt. This effect is especially important for high charged, slow diffusing cations during peridotite melting and melt-rock reaction. Apparent clinopyroxene-melt partition coefficients for REE, Sr, Y, Ti, and Zr, measured from reprecipitated clinopyroxene and coexisting melt in the reactive boundary layer, approach their equilibrium values reported in the literature. Disequilibrium melting models based on volume diffusion in solid limited mechanism are likely to significantly underestimate the rates at which major and trace elements in residual minerals reequilibrate with their surrounding melt. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

High-sensitive measurement of uranium L_III-edge X-ray absorption near-edge structure (XANES) for the determination of the oxidation states of uranium in crustal materials     

Yuhei Yamamoto  Yoshio Takahashi  Yutaka Kanai  Yoshio Watanabe  Tomoya Uruga  Hajime Tanida  Yasuko Terada  Hiroshi Shimizu   《Applied Geochemistry》2008,23(8):2452-2461

The uranium L_III-edge XANES spectra for natural rocks at the concentration range of 0.96–124 mg kg⁻¹ were measured using a log spiral bent crystal Laue analyzer (BCLA) combined with a multi-element Ge detector. It was found that the quality of the XANES spectra using the BCLA was greatly improved due to a reduction of interfering fluorescence from major components such as Rb and Sr. The ratio of signal to background intensities in the U L_III-edge XANES spectra increased by a factor of 2.9–17 with the use of the BCLA, which greatly enhanced the detection limit for the speciation of the oxidation states of U or the U(IV)/U(VI) ratio of natural samples. In addition, it was demonstrated that the fluorescence XANES method coupled with the BCLA enable determination of the speciation of U for various natural samples such as acidic igneous rocks, ferromanganese nodules, sediments, and some sedimentary rocks such as shale and limestone.  相似文献   

Crystal chemical significance of chemical zoning in dissakisite-(Ce)     

Mihoko Hoshino  Mitsuyoshi Kimata  Norimasa Nishida  Masahiro Shimizu 《Physics and Chemistry of Minerals》2008,35(2):59-70

Dissakisites from Trimouns dolomite mine, France, have two kinds of single crystals: chemical-zoned and homogeneous types. Back-scattered electron microprobe (BSE) images of these dissakisites reveal both Ca–Al rich dark zones and Fe-ΣREE rich bright zones. Crystal structures of three dark and two bright zones in a chemical-zoned dissakisite and of a homogeneous zone in unzoned dissakisite were refined to individual R indices (about 3.0–5.0%) based on 1,400 observed [|F ₀| > 4σF ₀] reflections measured with MoKα X-radiation using the single crystal diffractometer. The differences in brightness between their BSE images arise from those in coupled substitutions of the elements occupying A2 and M3 sites. The main reason for these differences is that ten-coordinated A2 polyhedra and M3 octahedra are directly linked through their shared edge, which creates a great potential for making this coupled substitution. This zoning indicates that formation of the whole zoned crystal, where each zone could be grown steadily with its crystallographic axes mutually parallel to each other, may be identified as autoepitaxy.  相似文献   

Seasonal and Spatial Variations of Total Mass Flux around Coral Reefs in the Southern Ryukyus,Japan     

Mohamed?IsmailEmail author  Tadashi?Kimura  Yumiko?Suzuki  Makoto?Tsuchiya 《Journal of Oceanography》2005,61(3):631-644

Total mass flux, size distribution of sediment particles and some chemical components such as total carbon (TC), total nitrogen (TN) and calcium carbonate (CaCO₃) were monitored monthly using a multi-cup sediment traps at seven coral reef sites (6 reef flat and 1 reef slope) of the Marine Protected Areas around Ishigaki, Kohama, Kuroshima and Iriomote Islands in the southern Ryukyus, Japan from September 2000 to September 2001. The size distribution of trapped sediments revealed mostly uni-modal fine sand to mud in the reef flat and gravelly to coarse sand in the reef slope. The total mass flux ranged between 0.54 to 872 gm⁻²d⁻¹, and showed a pronounced seasonality (high in summer-autumn and low in spring) at each site, which was consistent with the rainfall and typhoon regime. Exceptionally high values were observed on the reef slope (Iriomote) in February–March 2001 (1533 gm⁻²d⁻¹) owing to a large amount of bottom sediment re-suspension. On the reef flat (Todoroki South and North; Ishigaki), values obtained in July–August 2001 (872 gm⁻²d⁻¹) and August–September 2001 (800 gm^{− 2}d⁻¹) indicate the high terrestrial discharge from Todoroki River. Trapped sediment particles consist of CaCO₃ (1.2–27.1%) and a non-carbonate fraction (98.8–72.9%), which contains total carbon (4.9–26%), carbonate carbon (CO₂-C) (0.2–3.1%) and non-carbonate carbon (NC-C) (7.9–25.6%). Total nitrogen content was in the range 0.02–0.48%. TN is contained mainly in the carbonate fraction and NC-C may be contained in the non-carbonate fraction. The low TN/OC ratio of the trapped sediments suggests that they were mostly of terrestrial origin and that both fractions migrated. The high total mass flux derived from Todoroki River exceeded the threshold at which a lethal effect on coral community is caused. The results stress the importance of conducting seasonal studies of sedimentation over more than one year and at more than one location in south Japan coral reef ecosystems to gain an understanding of the processes controlling the total mass fluxes and their nutrients content, also to develop an awareness of how to prevent the damage of coral reef ecosystems and, if it does occur, to allow mitigation measures to be undertaken.  相似文献   

Total Lipid and Fatty Acid Classes in Decomposing Mangrove Leaves of <Emphasis Type="Italic">Bruguiera gymnorrhiza</Emphasis> and <Emphasis Type="Italic">Kandelia candel</Emphasis>: Significance with respect to Lipid Input     

Prosper?L.?Mfilinge  Tarik?Meziane  Zainudin?Bachok  Makoto?TsuchiyaEmail author 《Journal of Oceanography》2005,61(3):613-622

Changes in the concentration of total lipid and fatty acids (FAs) during the decomposition of mangrove leaves were investigated by field experiments using yellow leaves of Bruguiera gymnorrhiza (L.) Lamk. and Kandelia candel (L.) Druce, in order to quantify mangrove contribution to lipid and fatty acid inputs to marine sediments. Total lipid and total FA in the fresh (green and yellow) and decomposing leaves of both species were significantly higher during winter than summer. During decomposition, total lipid content and FA concentration, in particular branched chain fatty acids (BrFAs) and bacterial fatty acids (BFAs), increased to a maximum concentration in 45 days during winter and in 17 days during summer. Lipids were lost faster in K. candel leaf detritus than in B. gymnorrhiza leaf detritus in which >90% of the total lipid original weight was lost during the summer experiment and <60% during the winter experiment. The changes in the concentrations of total lipids and FAs in the decomposing leaves also indicate that mangrove leaves are significant sources of fatty acids and probably other lipid compounds to estuarine ecosystems and that tidal waters transport the lipids and FAs adsorbed to particulate matter from mangroves to adjacent estuarine sediments and the ocean.  相似文献   

Contamination of organotin compounds and imposex in molluscs from Vancouver,Canada     

Horiguchi T  Li Z  Uno S  Shimizu M  Shiraishi H  Morita M  Thompson JA  Levings CD 《Marine environmental research》2004,57(1-2):75-88

Gastropods and bivalves were collected at 15 sites at Vancouver and Victoria, Canada between 24 May and 7 June, 1999, to establish tissue concentrations of butyltin and phenyltin compounds, to record imposex symptoms in gastropods, and to assess the present status of organotin contamination around Vancouver. No neogastropods (such as Nucella lima) were found around Vancouver. Neogastropod populations could have been extirpated by severe TBT contamination in Vancouver, as relatively high concentrations of TBT were detected in tissues of Mytilus trossulus from Vancouver, and the neogastropods distributed in Vancouver might be sensitive to TBT. Recovery from imposex, however, was observed in neogastropod populations from three sites at Victoria and Mission Point. TBT contamination has continued around Vancouver, arising from continuous use of TBT in antifouling paints for vessels larger than 25 m in length; however, TBT has decreased around Victoria and Mission Point. Different patterns of TBT accumulation in tissue were observed among the bivalve species from Vancouver. The highest TBT concentration detected in Tresus capax suggested some possible adverse effects. TBT was the most predominant butyltin component in almost all bivalve specimens surveyed, suggesting a low rate of TBT metabolism. Phenyltin compounds were not detected in any molluscan specimens in this study.  相似文献