A new simple model for high-frequency quasi-periodic oscillations in black hole candidates   总被引：2，自引：0，他引：2  

L. Rezzolla  S'i. Yoshida  T. J. Maccarone  O. Zanotti 《Monthly notices of the Royal Astronomical Society》2003,344(3):L37-L41

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Simulations of a giant hybrid air shower detector     

B. R. Dawson  Y. Dai H.  P. Sommers  S. Yoshida 《Astroparticle Physics》1996,5(3-4):239-247

We have used Monte Carlo simulations to investigate the capabilities of a giant air shower observatory designed to detect showers initiated by cosmic rays with energies exceeding 10¹⁹ eV. The observatory is to consist of an array of detectors that will characterise the air shower at ground level, and optical detectors to measure the fluorescence light emitted by the shower in the atmosphere. Using these detectors together in a ‘hybrid’ configuration, we find that precise geometrical reconstruction of the shower axis is possible, leading to excellent resolution in energy. The technique is also shown to provide very good reconstruction below 10¹⁹ eV, at energies where the ground array is not fully efficient.  相似文献   

Simulations of deep pencil-beam redshift surveys     

N. Yoshida  J. Colberg  S.D.M. White  A.E. Evrard  T.J. MacFarland †  H.M.P. Couchman  A. Jenkins  C.S. Frenk  F.R. Pearce  G. Efstathiou  J.A. Peacock  P.A. Thomas 《Monthly notices of the Royal Astronomical Society》2001,325(2):803-816

We create mock pencil-beam redshift surveys from very large cosmological N -body simulations of two cold dark matter (CDM) cosmogonies, an Einstein–de Sitter model ( τ CDM) and a flat model with Ω₀=0.3 and a cosmological constant (ΛCDM). We use these to assess the significance of the apparent periodicity discovered by Broadhurst et al. Simulation particles are tagged as 'galaxies' so as to reproduce observed present-day correlations. They are then identified along the past light-cones of hypothetical observers to create mock catalogues with the geometry and the distance distribution of the Broadhurst et al. data. We produce 1936 (2625) quasi-independent catalogues from our τ CDM (ΛCDM) simulation. A couple of large clumps in a catalogue can produce a high peak at low wavenumbers in the corresponding one-dimensional power spectrum, without any apparent large-scale periodicity in the original redshift histogram. Although the simulated redshift histograms frequently display regularly spaced clumps, the spacing of these clumps varies between catalogues and there is no 'preferred' period over our many realizations. We find only a 0.72 (0.49) per cent chance that the highest peak in the power spectrum of a τ CDM (ΛCDM) catalogue has a peak-to-noise ratio higher than that in the Broadhurst et al. data. None of the simulated catalogues with such high peaks shows coherently spaced clumps with a significance as high as that of the real data. We conclude that in CDM universes, the regularity on a scale of ∼130  h ⁻¹ Mpc observed by Broadhurst et al. has a priori probability well below 10⁻³.  相似文献   

Geochemistry of Gneiss-Granulite transformation in the “incipient charnockite” zones of southern India     

M. Yoshida  M. Santosh  H. Shirahata 《Mineralogy and Petrology》1991,45(1):69-83

Summary Upper amphibolite facies gneisses in the southern Indian Shield show local transformation into veins, clots and patches of orthopyroxene-bearing dry granulites (incipient charnockites). Depending upon the protolith composition, these desiccated zones are classified into ortho- and para-charnockites and have developed within rocks of distinct mineralogy and chemistry at different time intervals through the structurally-controlled influx of carbon dioxide-rich fluids. Our geochemical investigations at five critical quarry sections indicate that the incipient charnockites have undepleted chemistry and very low K/Rb values. In the paracharnockite localities, where granulite formation is characterized by consumption of garnet, biotite and quartz to produce orthopyroxene, loss of Rb and Ba and enrichment of Ti are observed. In contrast, the orthocharnockite localities show marked LILE enrichment with gain of K, Rb and Ba and loss of CaO, suggesting extensive replacement of plagioclase in the gneisses by K-feldspar in the charnockite through K-Na-Ca exchange reactions with influxing carbonic fluids. The marked depletion in Fe, Mg, Ti and P in these rocks correlates with progressive dissolution of hornblende, biotite, magnetite and accessory apatite. Our study indicates that gneiss to granulite transformation, even if on a local scale, is not an isochemical phenomenon, but attended by distinct element mobilities, although they are contrastingly different from the geochemical trends in some regional high grade terrains.

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Geochemie von Gneiss-Granulit-Übergängen in den Incipient Charnockite Zonen von Süd-Indien

Zusammenfassung Gneise der oberen Amphibolit-Fazies im Südteil des Indischen Schildes zeigen lokal Umwandlungen in Adern, and unregelmäßigen Bereichen von orthopyroxen-führenden trockenen Granuliten (Incipient Charnockites). In Abhängigkeit von der Zusammensetzung des Ausgangsgesteins werden diese Zonen in Ortho- und Paracharnockite eingeteilt. Sie entwickelten sich in Gesteinen von charakteristischer mineralogischer und chemischer Zusammensetzung zu verschiedenen Zeit-Intervallen durch die tektonisch kontrollierte Zufuhr von kohlendioxid-reichen Fluiden. Unsere geochemischen Untersuchungen an fünf strategisch ausgewählten Steinbruchen zeigen, daß die Incipient Charnockite eine nicht verarmte chemische Zusammensetzung und sehr niedrige K/Rb Werte haben. In den Paracharnockit-Lokalitäten, wo Granulitbildung charakterisiert wird durch das Verschwinden von Granat, Biotit und Quartz, aus denen Orthopyroxene gebildet werden, ist Verlust von Rb und Ba und Anreicherung an Ti zu beobachten. Im Gegensatz dazu zeigen die Orthocharnockite eindeutige LILE Anreicherung mit Zunahme von K, Rb, und Ba und Verlust von Ca0. Dies weist auf extensiven Ersatz von Plagioklas in den Gneisen durch K-Feldspat in den Charnockiten durch K-Na-Ca Austausch-Reaktionen mit zugeführten C0₂-Fluiden hin. Die deutliche Verarmung an Fe, Mg, Ti und P in diesen Gesteinen wird mit zunehmender Auflösung von Hornblende, Biotit, Magnetit und akzessorischem Apatit erKlärt. Unsere Untersuchungen zeigen, daß die Gneis-Granulit Transformation auch im lokalen Maßstab nicht ein isochemisches Phänomen ist, sondern durch charakteristische Elementtransporte charakterisiert wird. Diese unterscheiden sich jedoch deutlich von den geochemischen Trends, die in einigen regional-metamorphen high grade terrains zu beobachten sind.[/p]

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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   

Transfer of60Co from midwater squid to sperm whales     

Takeshi Umezu  Hiroshi Ebihara  Yōko Minamisako  Hiroshi Watanabe 《Journal of Oceanography》1984,40(5):382-390

Sperm whales are notable squid-eaters. They feed mainly on medium to large-sized cephalopods at midwater levels and defecate near the surface. This suggests the existence of an upward transport of⁶⁰Co by sperm whales from the mesopelagic zone (150–1,200 m). To elucidate this squid-whale route for this artificial radionuclide,⁶⁰Co content was determined in squid and in predator whales captured by commercial whaling. In the Cephalopoda livers⁶⁰Co levels of 30–500 mBq kg^–1 wet were found and in the viscera of Odontoceti (toothed whales) 15–40 mBq kg^–1 wet. About 0.3% of⁸⁰Co ingested was estimated to be retained in a 23-year-old male sperm whale. In the livers of Bryde's whales,⁶⁰Co levels of 40–80 mBq kg^–1 wet were detected, but not in euphausiids and sardines, their possible prey. The level of Co in sperm whales was nearly the same as in Bryde's whales. Specific radioactivity⁶⁰Co/⁵⁹Co in mBq µg^–1 was several times higher in sperm whale (1.1–1.6) than in cephalopods (0.19–0.77). Eating prey with a high content of⁶⁰Co in the 1960's may have contributed to the present body burden in sperm whales with a long-life span. However, the origin of⁶⁰Co in Bryde's whales is unknown.  相似文献   

Near inertial motion excited by wind change in a margin of the Typhoon 9019   总被引：1，自引：0，他引：1  

Akio Maeda  Kazuki Uejima  Toru Yamashiro  Masahito Sakurai  Hiroshi Ichikawa  Masaki Chaen  Keisuke Taira  Shinjirou Mizuno 《Journal of Oceanography》1996,52(3):375-388

An excitation of inertial oscillation in the upper layer east of course of Typhoon 9019 was fortuitously observed at three surface buoys deployed during the Ocean Mixed Layer Experiment (OMLET). The observed inertial oscillation was compared with wind fluctuation measured at Ocean Weather Station T (29°N, 135°E) which was placed at the center of a triangle with three vertexes occupied by the respective surface buoys. Inertial oscillation is effectively excited in the mixed layer at the eastern margin of the typhoon by a rapid decrease of wind rather than by prevailing strong wind. It is shown by means of a least square deviation that the inertial oscillation observed in the mixed layer has a period of 23.9 hours shorter than the local inertial period of 24.7 hours. This shorter period suggests that the inertial oscillation has the finite velocities of phase and group as an inertial internal wave. A theoretically obtained ratio of vertical component of group velocity to that of phase velocity, approximately agrees with observed value. The inertial internal wave is excited by fluctuation of divergence with near inertial period in the mixed layer.  相似文献   

The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands   总被引：3，自引：0，他引：3  

Yuan Yaochu  Endoh Masahiro  Ishizaki Hiroshi 《海洋学报(英文版)》1991,10(3):373-391

In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i  相似文献   

Possible Density Change of the Origin of North Pacific Intermediate Water Due to Double Diffusion in the Mixed Water Region     

Ryuichiro?InoueEmail author  Jiro?Yoshida 《Journal of Oceanography》2005,61(5):871-883

In this study we test Talley's hypothesis that Oyashio winter mixed-layer water (26.5–26.6σ _θ) increases its density to produce the North Pacific Intermediate Water (NPIW) salinity minimum (26.7– 26.8σ_θ) in the Mixed Water Region, assuming a combination of cabbeling and double diffusion. The possible density change of Oyashio winter mixed-layer water is discussed using an instantaneous ratio of the change of temperature and salinity along any particular intrusion (R _l ). We estimate the range of R _l ^DD required to convert Oyashio winter mixed-layer water to the NPIW salinity minimum due to double diffusion, and then assume double-diffusive intrusions as this conversion mechanism. A double-diffusive intrusion model is used to estimate R _l ^DD in a situation where salt fingering dominates vertical mixing, as well as to determine whether Oyashio winter mixed-layer water can become the NPIW salinity minimum. Possible density changes are estimated from the model R _l ^DD by assuming the amount of density change due to cabbeling. From these results, we conclude that Oyashio winter mixed-layer water contributes to a freshening of the lighter layer of the NPIW salinity minimum (around 26.70σ_θ) in the MWR.  相似文献   

Decadal Variability of Subsurface Temperature in the Central North Pacific     

Satoshi Sugimoto  Takashi Yoshida  Tadashi Ando 《Journal of Oceanography》2003,59(6):945-955

Decadal variability of subsurface temperature in the North Pacific has been investigated. Two dominant regions were found; the central subarctic region (CSa) and the north-eastern subtropical region (NESt). In CSa, cooling (warming) of wintertime subsurface temperature corresponds to the large (small) temperature gradient and southward (northward) shift of subsurface temperature front, associated with the increase (decrease) of positive wind stress curl and the southward (northward) shift of curl τ zero line with 2 years delay. It is suggested that the relocation of subtropical-subarctic boundary plays an important role. In NESt, importance of heat flux through the sea surface and heat divergence in the Ekman layer is also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献