First sources in infrared light: stars, supernovae and miniquasars     

Asantha Cooray  Naoki Yoshida 《Monthly notices of the Royal Astronomical Society》2004,351(3):L71-L77

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Giant cluster arcs as a constraint on the scattering cross-section of dark matter     

Massimo Meneghetti  Naoki Yoshida  Matthias Bartelmann  Lauro Moscardini  Volker Springel  Giuseppe Tormen  Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2001,325(1):435-442

We carry out ray tracing through five high-resolution simulations of a galaxy cluster, to study how its ability to produce giant gravitationally lensed arcs is influenced by the collision cross-section of its dark matter. In three cases typical dark matter particles in the cluster core undergo between 1 and 100 collisions per Hubble time; two more explore the long ('collisionless') and short ('fluid') mean free path limits. We study the size and shape distributions of arcs and compute the cross-section for producing 'extreme' arcs of various sizes. Even a few collisions per particle modifies the core structure enough to destroy the ability of the cluster to produce long, thin arcs. For larger collision frequencies the cluster must be scaled up to unrealistically large masses before it regains the ability to produce giant arcs. None of our models with self-interacting dark matter (except the 'fluid' limit) is able to produce radial arcs; even the case with the smallest scattering cross-section must be scaled to the upper limit of observed cluster masses before it produces radial arcs. Apparently the elastic collision cross-section of dark matter in clusters must be very small, below 0.1 cm² g⁻¹, to be compatible with the observed ability of clusters to produce both radial arcs and giant arcs.  相似文献   

Field measurement and modeling of near-bed sediment transport processes with fluid mud layer in Tokyo Bay     

Nakagawa  Yasuyuki  Nadaoka  Kazuo  Yagi  Hiroshi  Ariji  Ryuichi  Yoneyama  Haruo  Shirai  Kazuhiro 《Ocean Dynamics》2012,62(10):1535-1544

Tokyo Bay is one of the estuaries in Japan with a high population of almost 26 million people in the basin area. One of the major concerns for the environment in this water area is the decreasing ecosystem functions including the deterioration of water and sediment qualities caused by various anthropogenic activities. Since the bottom sediments around almost the entire area of the inner bay consist of fine materials with a high organic content, which cause the deterioration of water quality through processes such as hypoxia, an understanding of the fine sediment dynamics in the Bay is crucial for an environmental assessment of the water area. This paper proposes a model for the key processes of fine sediment dynamics, which reflects field data about muddy bed structures and their dynamics obtained during the monitoring campaign in 2007. One of the specific features of the sediment in the Bay at present is the persistent existence of fluid mud layers (water content over 300 %) with a thickness of around a few decimeters, which might be caused by deposition of abundant organic particles due to eutrophication. The present study shows that diffusion flux model delivers quite reliable results for estimating erosion flux from the top of fluid mud layers after calibrating the model parameter against the time series data of vertical flux measured by an acoustic Doppler velocimeter system. This study also derives analytical solutions, based on the Bingham fluid concept, of advection flux in the fluid mud layer on which external shear stress force is applied.

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The 21-cm signature of early relic H ii regions     

Midori Tokutani  Naoki Yoshida  S. Peng Oh  Naoshi Sugiyama 《Monthly notices of the Royal Astronomical Society》2009,395(2):777-780

We calculate the spin temperature and 21-cm brightness of early H  ii regions around the first stars. We use outputs from cosmological radiation-hydrodynamics simulations of the formation and evolution of early H  ii regions. In the pre-re-ionization era, H  ii regions around massive primordial stars have diameters of a few kpc. The gas within the H  ii regions is almost fully ionized, but begins recombining after the central stars die off. The relic H  ii regions are then seen as bright emission sources in hydrogen 21 cm. We make brightness temperature maps of the H  ii regions, accounting for radiative coupling with Lyman α photons in a simplified manner. The spin temperature in the relic H  ii region is close to the gas kinetic temperature, generally several hundred to several thousand degrees. We show that the relic H  ii region can be as bright as  δ T _b∼ 100 mK  in differential temperature against the cosmic microwave background for an angular resolution of subarcseconds. While individual early H  ii patches will not be identified by currently planned radio telescopes, the collective fluctuations from early H  ii regions might imprint signatures in the 21-cm background.  相似文献   

Proton migration in portlandite inferred from activation energy of self-diffusion and potential energy curve of OH bond     

Naoki Noguchi  Keiji Shinoda 《Physics and Chemistry of Minerals》2010,37(6):361-370

A fundamental mechanism on the atomic level for self-diffusion in the proton layer of portlandite, Ca(OH)₂, was investigated by conducting hydrogen–deuterium (H–D) exchange diffusion experiments and by deriving potential energy curves of OH vibrations from optical absorption measurements. Synthetic single crystals of portlandite were used in H–D experiments between 250 and 450°C at 150 MPa. Arrhenius parameters for proton diffusion perpendicular to the c-axis gave a frequency factor of 1.0 × 10⁻¹⁰ m²/s and activation energy of 0.61 eV (58.5 kJ/mol). The activation energy corresponds to the height of the potential barrier between two oxygen atoms across an interlayer. The potential barrier height was also theoretically estimated using the OH potential energy curve (OH-PEC) determined by optical absorption measurements. Experimental and theoretical results suggest that the potential barrier height cannot be simply determined by overlapping two OH-PECs. The potential barrier derived theoretically was 3.11 eV. This is too high for the activation energy of the proton diffusion. It implies that the interaction between a diffusing proton and the vacancy of a proton site, and the shortening of interlayer oxygen distance by thermal vibration reduce the potential barrier.  相似文献   

Integrated description of deformation modes in a sedimentary basin: A case study around a shallow drilling site in the Mizunami area, eastern part of southwest Japan     

Yasuto  Itoh  Kenji  Amano Naoki  Kumazaki 《Island Arc》2006,15(1):165-177

Abstract   Tectonic episodes in a sedimentary basin are described on the basis of an integrated study combining reflection seismic interpretation, drilling survey and paleomagnetism. A shallow inclined borehole penetrated a fault shown by reflection seismic and geological surveys in the Mizunami area, in the eastern part of southwest Japan. Paleomagnetic measurements were carried out on core samples successfully oriented using side-wall image logging of structural attitude. At six horizons, stable characteristic remanent magnetization (ChRM) was confirmed through thermal and alternating field demagnetization tests, which were carried by magnetite with minor amounts of high coercivity minerals, as revealed by experiments of stepwise acquisition of isothermal remanent magnetization. After correction of multiphase deformation inferred from borehole structural analysis, ChRM directions were combined with previous data and confirmed an easterly deflection reflecting the coherent clockwise rotation of the arc before the Middle Miocene. Compilation of reliable paleomagnetic data described differential rotation of the eastern part of southwest Japan raised by collision of the Izu–Bonin Arc since the Middle Miocene. The present study suggests that (i) the Mizunami area is adjacent to a highly deformed zone bounded by the Akaishi Tectonic Line (ATL), and (ii) forearc deformation of southwest Japan is localized around the ATL, which is quite different from gradual bending on the back-arc side without remarkable crustal break related to the collision event.  相似文献   

Research Note the Matrix Element For A Transversely Isotropic Earth Model     

Naoki Shibata  Naoki Suda  Yoshio Fukao 《Geophysical Journal International》1990,100(2):315-318

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1992 compilation of analytical data for rare-earth elements, scandium, yttrium, zirconium and hafnium in twenty-six GSJ reference samples     

Shiro ITOH  Shigeru TERASHIMA  Noboru IMAI  Hikari KAMIOKA  Naoki MITA  Atsushi ANDO 《Geostandards and Geoanalytical Research》1993,17(1):5-79

Abstract: Analytical data for fourteen rare-earth elements, scandium, yttrium, zirconium and hafnium, received by May 1992, have been compiled on twenty-six GSJ (Geological Survey of Japan) reference samples. Seventeen of them are 'Igneous rock series' and nine are "Sedimentary rock series". The reported data including personal communication were evaluated under the consideration on analytical methods and geochemical evidences. No significant difference has been observed between the values obtained by the different analytical methods. Based on the selected available data, 1992 compilation values were tabulated.  相似文献   

Miocene fossil pinnipeds of the genera Prototaria and Neotherium (Carnivora; Otariidae; Imagotariinae) in the North Pacific Ocean: Evolution, relationships and distribution     

Naoki  Kohno Lawrence G.  Barnes Kiyoharu  Hirota 《Island Arc》1994,3(4):285-308

Abstract Fossil otariid pinnipeds of the extinct genera Prototaria Takeyama and Ozawa, 1984, and Neotherium Kellogg, 1931, known from Middle Miocene deposits bordering the North Pacific Ocean, are small, primitive pinnipeds in the subfamily Imagotariinae. They have a small supraorbital process of the frontal or have lost it entirely, a three-rooted first molar, small paroccipital process, and ear morphology indicating that they belong in the subfamily Imagotariinae. Their unique derived characters include extreme intertemporal constriction and highly modified cheek teeth, the premolars having become molarized by the addition of protocones and lingual cingula. Prototaria Takeyama and Ozawa, 1984, the most primitive known imagotariine genus, contains two species, P. primigena Takeyama and Ozawa, 1984, and P. planicephala Kohno, 1994, both of early Middle Miocene age from Japan. Prototaria has a few derived characters, including a large antorbital process, narrow intertemporal region, and large orbit, but its primitive characters apparently were inherited from enaliarctine ancestors. The long enigmatic Neotherium mirum Kellogg, 1931, of Middle Miocene age from California, USA, is related to Prototaria, but differs by having an elongate skull, very slender zygomatic arch, ventrally exposed median lacerate foramen, and smaller but more molarized premolars. A more primitive new genus and species, Proneotherium repenningi Barnes, related to N. mirum, is from the early Middle Miocene Astoria Formation, coastal Oregon, USA. It shares some derived characters with Prototaria, and shares many other important derived characters with N. mirum. Imagotariines probably arose from some species of Early Miocene enaliarctines, became diverse in Middle and Late Miocene time, and are only known from the North Pacific realm. Although they might include the ancestors of true walruses of the subfamily Odobeninae, no known imagotariines appear to have been adapted for mollusk feeding as are the highly evolved modern walruses. Instead, imagotariines appear to have retained a primitive piscivorous diet, as did the fur seals and sea lions of the subfamily Otariinae.  相似文献   

Oxygen isotopic composition of minerals in the Kenna ureilite     

Robert N. Clayton  Toshiko K. Mayeda  Naoki Onuma  John Shearer   《Geochimica et cosmochimica acta》1976,40(12):1475-1476

The δ¹⁸O and δ¹⁷O values of olivine from Kenna are 7.6 and 3.0%, respectively, relative to SMOW. These values are typical of ureilites which form a unique group on a δ¹⁷O -δ¹⁸O graph. The ureilites are related to, but not directly derived from, the anhydrous phases of C2 and C3 meteorites. The ¹⁸O/¹⁶O fractionation between pyroxene and olivine is 0.60, indicating a temperature of last equilibration of 1000 ± 100°C.  相似文献