Formation of globular clusters induced by external ultraviolet radiation     

Kenji Hasegawa  Masayuki Umemura  Tetsu Kitayama 《Monthly notices of the Royal Astronomical Society》2009,397(3):1338-1347

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A redetermination of the isotopic abundances of atmospheric Ar   总被引：5，自引：0，他引：5  

Jee-Yon Lee  Kurt Marti  Kenji Kawamura  Hee-Soo Yoo  Jin Seog Kim 《Geochimica et cosmochimica acta》2006,70(17):4507-4512

Atmospheric argon measured on a dynamically operated mass spectrometer with an ion source magnet, indicated systematically larger ⁴⁰Ar/³⁶Ar ratios compared to the generally accepted value of Nier [Nier A.O., 1950. A redetermination of the relative abundances of the isotopes of carbon, nitrogen, oxygen, argon, and potassium. Phys. Rev. 77, 789-793], 295.5 ± 0.5, which has served as the standard for all isotopic measurements in geochemistry and cosmochemistry. Gravimetrically prepared mixtures of highly enriched ³⁶Ar and ⁴⁰Ar were utilized to redetermine the isotopic abundances of atmospheric Ar, using a dynamically operated isotope ratio mass spectrometer with minor modifications and special gas handling techniques to avoid fractionation. A new ratio ⁴⁰Ar/³⁶Ar = 298.56 ± 0.31 was obtained with a precision of 0.1%, approximately 1% higher than the previously accepted value. Combined with the ³⁸Ar/³⁶Ar (0.1885 ± 0.0003) measured with a VG5400 noble gas mass spectrometer in static operation, the percent abundances of ³⁶Ar, ³⁸Ar, and ⁴⁰Ar were determined to be 0.3336 ± 0.0004, 0.0629 ± 0.0001, and 99.6035 ± 0.0004, respectively. We calculate an atomic mass of Ar of 39.9478 ± 0.0002. Accurate Ar isotopic abundances are relevant in numerous applications, as the calibration of the mass spectrometer discrimination.  相似文献   

Discriminating residual and colluvial soils using topographic analysis in a small,forested catchment in Japan     

Kenji Maeda  Takafumi Tanaka  Ohta Takeshi  Shigeaki Hattori 《水文研究》2007,21(16):2144-2156

Soil moisture plays an important role in hydrology. Understanding factors (such as topography, vegetation, and meteorological conditions) that influence spatio‐temporal variability in soil moisture, and how this influence is manifested, is important for understanding hydrological processes. A number of distributed (quasi‐)physical hydrological models have been developed to investigate this subject. Previous studies have shown that the spatial differences in the distribution of soil types (residual and colluvial soils) dominantly reflect spatio‐temporal fluctuations in soil moisture and runoff. We present a methodology for assessing the spatial distribution of residual and colluvial soils, which differ with respect to their physical characteristics, in a 0·88 km² forested catchment with complex topography and a complex land‐use history. Our method is based on penetration resistance profile data; in this data set, each data point represents soil physical characteristics within an area of about 25 m². If the spatial distribution of soils under similar meteorological, geological, historical land use, and other conditions could be characterized on the basis of similarity in topographic features, then the spatial distribution of soil could be predicted based on relationships between various topographic indices (e.g. topographic index and local slope). We tested whether our model correctly assessed the reference data. The model's results were 90·5% correct for residual soils and 87·3% correct for colluvial soils. Further studies will quantify the relationships between topographic features of land covered by residual and colluvial soils and changes in spatio‐temporal variations in the catchment (e.g. vegetation and land use) as a function of geology or meteorology. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Construction of Wide Field Cryogenic Telescope     

Minoru Ando  Tetsuya Nagata  Shuji Sato  Makoto Watanabe  Kunio Itoh  Toshihide Kawai  Hidehiko Nakaya  Yoshiharu Namba  Takeshi Takezawa 《Experimental Astronomy》2002,13(3):119-134

We constructed a wide field cryogenic telescope (WFCT) containing a whole Ritchey-Chrétien system and a focal plane array in a cryostat for near infrared observations to cover the field of view of 0.4°. The telescope has a primary mirror of 220 mm and an engineering grade 256 × 256 InSb array. The optical components such as two mirrors, filters, spiders, and radiation shield tube are cooled down to 180 K as well as the InSb array to 35 K by a mechanical refrigerator. We show the results of the background surface brightnesses and the limiting magnitudes at 3.3 and 3.67 μm measured at Sutherland, South Africa. We describe the on-going upgrade of this instrument, equipped with a 1024 × 1024 ALADDIN InSb science grade array. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Free oscillation of the Japan Sea excited by earthquakes—I. Observation and wave-theoretical approach     

Kenji Satake  Kunihiko Shimazaki 《Geophysical Journal International》1988,93(3):451-456

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Introduction to ��Tsunamis in the World Ocean: Past, Present, and Future. Volume I��     

Kenji Satake  Alexander Rabinovich  Utku Kano?lu  Stefano Tinti 《Pure and Applied Geophysics》2011,168(6-7):963-968

Eighteen papers are included in Volume 1 of a PAGEOPH topical issue Tsunamis in the World Ocean: Past, Present, and Future. These papers are briefly introduced. They are grouped into three categories: case studies of earthquake-generated tsunamis; tsunami forecast and hazard assessments; and theoretical and computational modeling of tsunami generation, propagation, and coastal behavior. Most of the papers were presented at the 24th International Tsunami Symposium held 14?C16 July 2009 in Novosibirsk, Russia, and reflect the current state of tsunami science.  相似文献   

Observation and Modeling of the January 2009 West Papua, Indonesia Tsunami     

Yushiro Fujii  Kenji Satake  Yuji Nishimae 《Pure and Applied Geophysics》2011,168(6-7):1089-1100

We modeled a tsunami from the West Papua, Indonesia earthquakes on January 3, 2009 (M _w?=?7.7). After the first earthquake, tsunami alerts were issued in Indonesia and Japan. The tsunami was recorded at many stations located in and around the Pacific Ocean. In particular, at Kushimoto on Kii Peninsula, the maximum amplitude was 43?cm, larger than that at Manokwari on New Guinea Island, near the epicenter. The tsunami was recorded on near-shore wave gauges, offshore GPS sensors and deep-sea bottom pressure sensors. We have collected more than 150 records and used 72 stations?? data with clear tsunami signals for the tsunami source modeling. We assumed two fault models (single fault and five subfaults) which are located to cover the aftershock area. The estimated average slip on the single fault model (80?×?40?km) is 0.64?m, which yields a seismic moment of 1.02?×?10²⁰?Nm (M _w?=?7.3). The observed tsunami waveforms at most stations are well explained by this model.  相似文献   

Introduction to “Tsunamis in the World Ocean: Past,Present, and Future. Volume II”     

Kenji?SatakeEmail author  Alexander?Rabinovich  Utku?Kano?lu  Stefano?Tinti 《Pure and Applied Geophysics》2011,168(11):1913-1917

Fifteen papers are included in Volume 2 of a PAGEOPH topical issue Tsunamis in the World Ocean: Past, Present, and Future. These papers are briefly introduced. They are grouped into three categories: reports and studies of recent tsunamis, studies on tsunami statistics and application to tsunami warning, and modeling studies of tsunami runup and inundation. Most of the papers were presented at the 24th International Tsunami Symposium held 14–16 July 2009 in Novosibirsk, Russia, and reflect the current state of tsunami science.  相似文献   

Thermochronology and the three-dimensional cooling pattern of a granitic pluton: an example from the Toki granite,Central Japan     

Takashi Yuguchi  Kenji Amano  Tadahiko Tsuruta  Tohru Danhara  Tadao Nishiyama 《Contributions to Mineralogy and Petrology》2011,162(5):1063-1077

The three-dimensional spatial variations in the cooling pattern of the Toki granitic body, a zoned pluton in Central Japan, have been evaluated quantitatively by thermochronology using cooling age determination based on the different closure temperatures for target mineral species. The Toki granite has hornblende K–Ar ages of about 74.3 ± 3.7 Ma (N = 2; closure temperature of 510 ± 25°C), biotite K–Ar ages of 78.5 ± 3.9 to 59.7 ± 1.5 Ma (N = 33; 300 ± 50°C), and zircon fission-track ages of 75.6 ± 3.3 to 52.8 ± 2.6 Ma (N = 44; 240 ± 50°C). The spatial variation in the biotite K–Ar age is similar to that in the zircon fission-track age in samples collected from 11 boreholes and seven outcrop sites in the Toki granite, indicating that cooling was effectively from the roof and also from the northwest margin. This cooling pattern shows a strong correlation with the Alumina Saturation Index (ASI) distribution of the body. Larger ASI values correspond to earlier and more rapid cooling after emplacement and smaller value to slower cooling. Toki granite was effectively cooled from the peraluminous regions where assimilation of country sedimentary rock was most extensive.  相似文献   

Regional groundwater flow in an area mapped as continuous permafrost, NE Alaska (USA)     

Douglas L. Kane  Kenji Yoshikawa  James P. McNamara 《Hydrogeology Journal》2013,21(1):41-52

Fundamental knowledge of groundwater systems in areas of permafrost is often lacking. The likelihood of finding good quality groundwater resources of acceptable quantities generally decreases as the areal coverage of permafrost increases. In areas of continuous permafrost, the probability of finding areas of groundwater recharge and discharge are minimal. Still, in northeastern Alaska (USA), the presence of numerous springs and associated downstream aufeis formations clearly indicates that there has to be a groundwater system with the required complementary areas of groundwater recharge and transmission. Recharge zones and transmission pathways in this area of extensive permafrost, however, are essentially unknown. This study shows that the recharge occurs on the south side of the Brooks Range in northeastern Alaska, where extensive limestone outcrops are found. The transmission zone is beneath the permafrost, with discharge occurring through the springs via taliks through the permafrost (where faults are present) and also likely at the northern edge of the permafrost along the Beaufort Sea coast.  相似文献