Radio imaging of the Subaru/XMM–Newton Deep Field – I. The 100-μJy catalogue, optical identifications, and the nature of the faint radio source population     

Chris Simpson  Alejo Martínez-Sansigre  Steve Rawlings  Rob Ivison  Masayuki Akiyama  Kazuhiro Sekiguchi  Tadafumi Takata  Yoshihiro Ueda  Mike Watson 《Monthly notices of the Royal Astronomical Society》2006,372(2):741-757

We describe deep radio imaging at 1.4 GHz of the 1.3-deg² Subaru/ XMM–Newton Deep Field (SXDF), made with the Very Large Array in B and C configurations. We present a radio map of the entire field, and a catalogue of 505 sources covering 0.8 deg² to a peak flux density limit of 100 μJy. Robust optical identifications are provided for 90 per cent of the sources, and suggested identifications are presented for all but 14 (of which seven are optically blank, and seven are close to bright contaminating objects). We show that the optical properties of the radio sources do not change with flux density, suggesting that active galactic nuclei (AGN) continue to contribute significantly at faint flux densities. We test this assertion by cross-correlating our radio catalogue with the X-ray source catalogue and conclude that radio-quiet AGN become a significant population at flux densities below 300 μJy, and may dominate the population responsible for the flattening of the radio source counts if a significant fraction of them are Compton-thick.  相似文献   

Occurrence of two distinct types of tissue inhibitors of metallo-proteinases-2 in Fugu rubripes     

Yoshihiro Yokoyama  Hiroshi Tsukamoto  Tohru Suzuki  Shohshi Mizuta  Reiji Yoshinaka 《中国海洋大学学报(英文版)》2005,4(3):214-218

In this study, genes of two distinct tissue inhibitors of metalloproteinases-2 (TIMP-2) from Japanese puffer fish Fugu rubripes, Fugu TIMP-2a and TIMP-2b, were cloned. The open reading frames of Fugu TIMP-2a and TIMP-2b cDNAs are composed of 660 and 657 nucleotides and 220 and 219 amino acids, respectively. Both Fugu TIMP-2s contain 12 cysteine residues, which might form six disulfide bonds as in other animals’ TIMP-2s. Reverse-transcribed polymerase chain reaction analysis showed the mRNAs of Fugu TIMP-2a and TIMP-2b to be expressed in some tissues examined with different expression patterns. These findings suggest that the two distinct Fugu TIMP-2s might perform different functions in Fugu tissues.  相似文献   

Factors controlling diurnal variation in the isotopic composition of atmospheric water vapour observed in the taiga,eastern Siberia     

Akihiro Ueta  Atsuko Sugimoto  Yoshihiro Iijima  Hironori Yabuki  Trofim C. Maximov  Tatiana A. Velivetskaya  Alexander V. Ignatiev 《水文研究》2013,27(16):2295-2305

Deciduous forest covers vast areas of permafrost under severe dry climate in eastern Siberia. Understanding the water cycle in this forest ecosystem is quite important for climate projection. In this study, diurnal variations in isotopic compositions of atmospheric water vapour were observed in eastern Siberia with isotope analyses of precipitation, sap water of larch trees, soil water, and water in surface organic layer during the late summer periods of 2006, 2007, and 2008. In these years, the soil moisture content was considerably high due to unusually large amounts of summer rainfall and winter snowfall. The observed sap water δ¹⁸O ranged from ?17.9‰ to ?13.3‰, which was close to that of summer precipitation and soil water in the shallow layer, and represents that of transpired water vapour. On sunny days, as the air temperature and mixing ratio rose from predawn to morning, the atmospheric water vapour δ¹⁸O increased by 1‰ to 5‰ and then decreased by about 2‰ from morning to afternoon with the mixing ratio. On cloudy days, by contrast, the afternoon decrease in δ¹⁸O and the mixing ratio was not observed. These results show that water vapour that transpired from plants, with higher δ¹⁸O than the atmospheric water vapour, contributes to the increase in δ¹⁸O in the morning, whereas water vapour in the free atmosphere, with lower δ¹⁸O, contributes to the decrease in the afternoon on sunny days. The observed results reveal the significance of transpired water vapour, with relatively high δ¹⁸O, in the water cycle on a short diurnal time scale and confirm the importance of the recycling of precipitation through transpiration in continental forest environments such as the eastern Siberian taiga. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Refinement of the age of the Middle Miocene Fort Ternan Beds,Western Kenya,and its implications for Old World biochronology     

Martin Pickford  Yoshihiro Sawada  Ryoichi Tayama  Yu-ko Matsuda  Tetsumaru Itaya  Hironobu Hyodo  Brigitte Senut 《Comptes Rendus Geoscience》2006,338(8):545-555

It has become increasingly obvious over the past two decades that the fossiliferous strata at Fort Ternan, Kenya, are probably somewhat younger than 14 Ma, an age which has long been attached to the deposits. This realisation flows from geological and biochronological observations. In order to test the hypothesis, resampling of all the lava flows in the region of Fort Ternan was undertaken in 2003, especially those underlying the Fort Ternan Beds in the Kipchorion Gorge where the sequence is the most complete. Samples obtained from lava flows underlying and overlying the fossil beds were analysed for anorthoclase K/Ar and ⁴⁰Ar/³⁹Ar and biotite ⁴⁰Ar/³⁹Ar age determinations. The results reveal that the age of the fossiliferous sediments is ca $13.7\pm 0.3\text{Ma}$. Since Fort Ternan yielded the ‘core fauna’ that defines Faunal Set IV of the East African biochronological sequence this refinement of its age will impact on age estimates of neighbouring Faunal Sets, as well as on other faunas correlated to Fort Ternan, including those in Europe belonging to MN Zones MN 5, MN 6 and MN 7/8. To cite this article: M. Pickford et al., C. R. Geoscience 338 (2006).  相似文献   

Zircon U–Pb ages and Sr–Nd isotope ratios for the Sirstan granitoid body,NE Iraq: Evidence of magmatic activity in the Middle Cretaceous Period     

Imad Kadhim Abdulzahra  Ayten Hadi  Hossein Azizi  Yoshihiro Asahara  Koshi Yamamoto 《Comptes Rendus Geoscience》2017,349(2):53-62

The Sirstan granitoid (SG), comprising diorite and granodiorite, is located in the Shalair Valley area, in the northeastern part of Iraq within the Sanandaj–Sirjan Zone (SSZ) of the Zagros Orogenic Belt. The U–Pb zircon dating of the SG rocks has revealed a concordia age of 110 Ma, which is interpreted as the age of crystallization of this granitoid body during the Middle Cretaceous. The whole-rock Rb–Sr isochron data shows an age of 52.4 ± 9.4 Ma (MSWD = 1.7), which implies the reactivation of the granitoid body in the Early Eocene due to the collision between the Arabian and Iranian plates. These rocks show metaluminous affinity with low values of Nb, Ta and Ti compared to chondrite, suggesting the generation of these rocks over the subduction zone in an active continental margin regime. The SG rocks are hornblende-bearing I-type granitoids with microgranular mafic enclaves. The positive values of ?_Nd (t = 110 Ma) (+0.1 to +2.7) and the low (⁸⁷Sr/⁸⁶Sr)_i ratios (0.7044 to 0.7057) indicate that the magma source of the SG granitoids is a depleted subcontinental mantle. The chemical and isotope compositions show that the SG body originated from the metasomatic mantle without a major role for continental contamination. Our findings show that the granitoid bodies distributed in the SSZ were derived from the continuous Neo-Tethys subduction beneath the SSZ in Mesozoic times and that the SSZ was an active margin in the Middle Cretaceous.  相似文献   

Petrological variation of large-volume felsic magmas from Hakkoda-Towada caldera cluster: Implications for the origin of high-K felsic magmas in the Northeast Japan Arc     

Takashi  Kudo  Minoru  Sasaki  Yoshihiro  Uchiyama  Akifumi  Nozawa  Hisashi  Sasaki  Takeshi  Tokizawa  Shinji  Takarada 《Island Arc》2007,16(1):133-155

Abstract The Hakkoda‐Towada caldera cluster (HTCC) is a typical Late Cenozoic caldera cluster located in the northern part of the Northeast Japan Arc. The HTCC consists of five caldera volcanoes, active between 3.5 Ma and present time. The felsic magmas can be classified into high‐K (HK‐) type and medium‐ to low‐K (MLK‐) type based on their whole‐rock chemistry. The HK‐type magmas are characterized by higher K₂O and Rb contents and higher ⁸⁷Sr/⁸⁶Sr ratios than MLK‐type magmas. Both magmas cannot be derived from fractional crystallization of any basaltic magma in the HTCC. Assimilation‐fractional crystallization model calculations show that crustal assimilation is necessary for producing the felsic magmas, and HK‐type magmas are produced by higher degree of crustal assimilation with fractional crystallization than MLK‐type magmas. Although MLK‐type magmas were erupted throughout HTCC activity, HK‐type magmas were erupted only during the initial stage. The temporal variations of magma types suggest the large contribution of crustal components in the initial stage. A major volcanic hiatus of 3 my before the HTCC activity suggests a relatively cold crust in the initial stage. The cold crust probably promoted crustal assimilation and fractional crystallization, and caused the initial generation of HK‐type magmas. Subsequently, the repeated supply of mantle‐derived magmas raised temperature in the crust and formed relatively stable magma pathways. Such a later system produced MLK‐type magmas with lesser crustal components. The MLK‐type magmas are common and HK‐type magmas are exceptional during the Pliocene–Quaternary volcanism in the Northeast Japan Arc. This fact suggests that exceptional conditions are necessary for the production of HK‐type magmas. A relatively cold crust caused by a long volcanic hiatus (several million years) is considered as one of the probable conditions. Intensive crustal assimilation and fractional crystallization promoted by the cold crust may be necessary for the generation of highly evolved HK‐type felsic magmas.  相似文献   

Concentration of Gold(I) Thiosulfate Complex Ions on the Surface of Alumina Gel and their Change in Chemical State: Preliminary Experiment in the Elucidation of the Formation Mechanism of Epithermal Gold Deposits     

Kotaro Yonezu    Takushi Yokoyama    Yoshihiro Okaue    Akira Imai  Koichiro Watanabe 《Resource Geology》2007,57(4):400-408

In order to elucidate the formation mechanism of low‐sulfidation epithermal gold deposit, the adsorption of [Au(S₂O₃)₂]^3? (a model compound for gold(I) complex ion) on alumina gel (a model compound for the aluminum‐bearing minerals) and change in chemical state of [Au(S₂O₃)₂]^3? after adsorption on the surface of alumina gel were investigated as a basic model experiment. In the pH range from 4 to 6, the amount of [Au(S₂O₃)₂]^3? adsorbed on alumina gel decreased with increasing pH and decreased drastically between pH 6 and 7, and then approached zero above pH 8 at 30°C. At 60°C, the amount of gold adsorbed above pH 7 was enhanced compared with that at 30°C. This adsorption tendency indicates that [Au(S₂O₃)₂]^3? is mainly adsorbed by electrostatic interaction between negative charges of [Au(S₂O₃)₂]^3? and positive charges of alumina gel because of its isoelectric point around pH 9. The chemical state of gold after adsorption of [Au(S₂O₃)₂]^3? on alumina gel was examined using X‐ray absorption near edge structure (XANES). The result showed that [Au(S₂O₃)₂]^3? was spontaneously reduced to elemental gold even in the absence of specific reducing agents after adsorption on alumina gel. This reduction reaction might occur by two steps: (i) disproportionation of the adsorbed [Au(S₂O₃)₂]^3? at the surface of alumina gel, and (ii) spontaneous reduction of the resulting gold(III) complex ions on the surface of alumina gel. The experimental results suggest that aluminum plays an important role in the concentration of gold(I) complex ions and subsequent reduction of gold during the formation of low‐sulfidation epithermal gold deposits.  相似文献   

Molecular cloning and mRNA expression of cytochrome P4501A1 and 1A2 in the liver of common minke whales (Balaenoptera acutorostrata)     

Niimi S  Watanabe MX  Kim EY  Iwata H  Yasunaga G  Fujise Y  Tanabe S 《Marine pollution bulletin》2005,51(8-12):784-793

This study presents full-length cDNA sequences of CYP1A1 and 1A2, in common minke whale (Balaenoptera acutorostrata) from the North Pacific. Both CYP1A1 and CYP1A2 cDNAs had an open reading frame of 516 amino acid residues, and predicted molecular masses were 58.3 kDa and 58.1 kDa, respectively. The deduced full-length amino acid sequence of CYP1A1 revealed higher identities with those of sheep (86%) and pig (87%), and that of CYP1A2 was most closely related to human (82%) and monkey CYP1A2 (82%) among species from which CYP1A2 has been isolated so far. Differences in certain conserved and functional amino acid residues of CYP1A1 and 1A2 between common minke whale and other mammalian species indicate the possibility of their specific metabolic function. Concentrations of organochlorine compounds (OCs) including PCBs and DDTs analyzed in common minke whale liver showed no significant correlation with hepatic mRNA expression levels of CYP1A1 and CYP1A2, indicating no induction of these enzymes by such OCs.  相似文献   

Seasonal variation in the energy and water exchanges above and below a larch forest in eastern Siberia     

Takeshi Ohta  Tetsuya Hiyama  Hiroki Tanaka  Takashi Kuwada  Trofim C. Maximov  Tetsuo Ohata  Yoshihiro Fukushima 《水文研究》2001,15(8):1459-1476

The water and energy exchanges in forests form one of the most important hydro‐meteorological systems. There have been far fewer investigations of the water and heat exchange in high latitude forests than of those in warm, humid regions. There have been few observations of this system in Siberia for an entire growing season, including the snowmelt and leaf‐fall seasons. In this study, the characteristics of the energy and water budgets in an eastern Siberian larch forest were investigated from the snowmelt season to the leaf‐fall season. The latent heat flux was strongly affected by the transpiration activity of the larch trees and increased quickly as the larch stand began to foliate. The sensible heat dropped at that time, although the net all‐wave radiation increased. Consequently, the seasonal variation in the Bowen ratio was clearly ‘U’‐shaped, and the minimum value (1·0) occurred in June and July. The Bowen ratio was very high (10–25) in early spring, just before leaf opening. The canopy resistance for a big leaf model far exceeded the aerodynamic resistance and fluctuated over a much wider range. The canopy resistance was strongly restricted by the saturation deficit, and its minimum value was 100 s m^?1 (10 mm s^?1 in conductance). This minimum canopy resistance is higher than values obtained for forests in warm, humid regions, but is similar to those measured in other boreal conifer forests. It has been suggested that the senescence of leaves also affects the canopy resistance, which was higher in the leaf‐fall season than in the foliated season. The mean evapotranspiration rate from 21 April 1998 to 7 September 1998 was 1·16 mm day^?1, and the maximum rate, 2·9 mm day^?1, occurred at the beginning of July. For the growing season from 1 June to 31 August, this rate was 1·5 mm day^?1. The total evapotranspiration from the forest (151 mm) exceeded the amount of precipitation (106 mm) and was equal to 73% of the total water input (211 mm), including the snow water equivalent. The understory evapotranspiration reached 35% of the total evapotranspiration, and the interception evaporation was 15% of the gross precipitation. The understory evapotranspiration was high and the interception evaporation was low because the canopy was sparse and the leaf area index was low. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Estimating the permeability of the Nojima Fault Zone by a hydrophone vertical seismic profiling experiment     

Tsutomu Kiguchi  Hisaso Ito  Yasuto Kuwahara  Teruki Miyazaki 《Island Arc》2001,10(3-4):348-356

Abstract A multi-offset hydrophone vertical seismic profiling (VSP) experiment was done in a 747 m deep borehole at Nojima Hirabayashi, Hyogo prefecture, Japan. The borehole was drilled to penetrate the Nojima Fault, which was active in the 1995 Hyogo-ken Nanbu earthquake. The purpose of the hydrophone VSP is to detect subsurface permeable fractures and permeable zones and, in the present case, to estimate the permeability of the Nojima Fault. The analysis was based on a model by which tube waves are generated when incident P-waves compress the permeable fractures (or permeable zones) intersecting the borehole and a fluid in the fracture is injected into the borehole. Permeable fractures (or permeable zones) are detected at the depths of tube wave generation, and fracture permeability is calculated from the amplitude ratio of tube wave to incident P-wave. Several generations of tube waves were detected from the VSP sections. Distinct tube waves were generated at depths of the fault zone that are characterized by altered and deformed granodiorite with a fault gouge, suggesting that permeable fractures and permeable zones exist in the fault zone. Tube wave analysis shows that the permeability of the fault gouge from 624 m to 625 m is estimated to be approximately 2 × 10⁻¹² m².  相似文献