Estimation of the <Emphasis Type="Italic">in situ</Emphasis> Ultraviolet-A absorption of seawater by a simple irradiance inversion model     

Takafumi Hirata 《Journal of Oceanography》2008,64(4):561-566

An irradiance inversion model to estimate the in situ absorption coefficient of seawater has been developed for the Ultraviolet-A (UVA) wavelength domain. Input parameters are sun angle and the up-and downward planar irradiances measured for at least two depths. The present method does not require seawater to be sampled, and is a discrete wavelength method which returns the absorption coefficient at a given wavelength from the irradiances measured at that wavelength without assuming a spectral shape of any optical properties a priori. Comparison between the model results and spectrophotometric measurements shows that the model is practically useful when cloud cover in the atmosphere is ≤ 50%. According to the present method, measurements of the irradiances enable simultaneous observation of the in situ underwater UVA radiation level and the absorption capacity of bulk seawater using a radiometer.  相似文献   

Application of laser ablation ICPMS to trace the environmental history of chum salmon Oncorhynchus keta     

Arai T  Hirata T  Takagi Y 《Marine environmental research》2007,63(1):55-66

Trace element levels in otoliths of chum salmon Oncorhynchus keta were examined by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). A close linear relationship in the Sr:Ca ratios between EPMA (X-ray analysis with an electron microprobe) and LA-ICPMS analyses was found (p<0.0001), suggesting that the latter technique could be used to separate the marine and freshwater life phases. Mg:Ca, Cr:Ca, Zn:Ca and Ba:Ca ratios in either the core region or the oceanic growth zone of the otoliths varied among sites. These differences suggest that elemental compositions may reflect environmental variability among spawning (breeding) or habitat sites. Thus, those element ratios demonstrate the potential to be used to distinguish between fish spawning (breeding) sites and habitats for this species of salmon.  相似文献   

Density profiles of galaxy groups and clusters from SDSS galaxy–galaxy weak lensing     

Rachel Mandelbaum  Uro&#; Seljak  Richard J. Cool  Michael Blanton  Christopher M. Hirata  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,372(2):758-776

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Galaxy–galaxy weak lensing in the Sloan Digital Sky Survey: intrinsic alignments and shear calibration errors     

Christopher M. Hirata  Rachel Mandelbaum  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Jonathan Brinkmann  Tamas Budávari  rew Connolly  Istvan Csabai  Ryan Scranton  Alexander S. Szalay 《Monthly notices of the Royal Astronomical Society》2004,353(2):529-549

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Earthquake distribution in the subduction zone off eastern Hokkaido, Japan, deduced from ocean-bottom seismographic and land observations     

Takaya Iwasaki  Naoshi Hirata  Toshihiko Kanazawa  Taku Urabe  Yoshinobu Motoya  Hideki Shimamura 《Geophysical Journal International》1991,105(3):693-711

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The epoch of reionization     

Andrew J. Benson  Naoshi Sugiyama  Adi Nusser  Cedric G. Lacey 《Monthly notices of the Royal Astronomical Society》2006,369(3):1055-1080

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Non-uniform reionization by galaxies and its effect on the cosmic microwave background     

A. J. Benson  Adi Nusser  Naoshi Sugiyama  C. G. Lacey 《Monthly notices of the Royal Astronomical Society》2001,320(1):153-176

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Intrinsic galaxy alignments from the 2SLAQ and SDSS surveys: luminosity and redshift scalings and implications for weak lensing surveys     

Christopher M. Hirata  Rachel Mandelbaum †  Mustapha Ishak  Uro&#; Seljak  Robert Nichol  Kevin A. Pimbblet  Nicholas P. Ross  David Wake 《Monthly notices of the Royal Astronomical Society》2007,381(3):1197-1218

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Observations of microseismicity in the southern Kuril Trench area by arrays of ocean bottom seismometers     

Naoshi Hirata  Toshihiko Kanazawa  Kiyoshi Suyehiro  Takaya Iwasaki  Hideki Shimamura 《Geophysical Journal International》1989,98(1):55-68

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Polar magnetic substorms     

Naoshi Fukushima 《Planetary and Space Science》1972

From the world distribution of geomagnetic disturbance, the connection between the electric current in the ionosphere, the field-aligned current and asymmetric equatorial ringcurrent in the magnetosphere is discussed. The partial ring-current in the afternoon-evening region, whose intensity is closely correlated with the AE-index, usually develops and decays earlier than the symmetric ring-current in the course of magnetic storms. The partial ringcurrent seems to have a direct connection with the positive geomagnetic bay in high latitudes in the evening hours through the ionizing effect of the particles leaking from the partial ringcurrent. The dawn-to-dusk electric field in the magnetospheric tail is transferred to the polar ionosphere, producing there the twin vortex Hall current responsible for polar cap geomagnetic variation. The magnetic effect of the associated Pedersen current in the ionosphere is shown to be small but still worth considering. The electrojet near midnight along the auroral oval is thought to appear when the electric conductivity of the ionosphere is locally increased under the presence of large scale dawn-to-dusk electric field. The occasional appearance of a localized abnormal geomagnetic disturbance with reversed direction near the geomagnetic pole seems to suggest the occasional reversal of electric field near the outer surface of the magnetospheric tail, especially when the interplanetary magnetic field is northward.  相似文献