亚洲人类的起源及其演化途径的初步研究     

滨田润一 《地球学报》1999,20(3):325-332

自１９４９ 年新中国建立以后,在中国各地相继发现中新世早期以来的远古人类化石,使之有可能逐渐阐明亚洲人类的演化过程,笔者根据各化石的特征考察它们的系统,根据各时期的古环境及古气候情况推断它们的演化途径,把在欧洲出现的古类人猿 Ａｌｓａｔｉｃｏｐｉｔｈｅｃｕｓ 当成发现种,非洲系人类在非洲及欧洲或亚洲中部完成了演化。同时,把在缅甸出现的古类人猿 Ａｍｐｈｉｐｉｔｈｅｃｕｓ 或 Ｐｏｎｄａｕｎｇｉａ 当成发源种,亚洲系人类在亚洲东南部完成了演化。在此期间,在非洲及欧洲或亚洲中部的巴基斯坦出现的西瓦古猿及腊玛  相似文献   

Automated Identification of Coronal Holes from Synoptic EUV Maps     

Amr Hamada  Timo Asikainen  Ilpo Virtanen  Kalevi Mursula 《Solar physics》2018,293(4):71

Coronal holes (CHs) are regions of open magnetic field lines in the solar corona and the source of the fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195 Å/193 Å, 171 Å and 304 Å) measured by the Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instruments. The two datasets are first homogenized by scaling the SDO/AIA data to the SOHO/EIT level by means of histogram equalization. We then develop a novel automated method to identify CHs from these homogenized maps by determining the intensity threshold of CH regions separately for each synoptic map. This is done by identifying the best location and size of an image segment, which optimally contains portions of coronal holes and the surrounding quiet Sun allowing us to detect the momentary intensity threshold. Our method is thus able to adjust itself to the changing scale size of coronal holes and to temporally varying intensities. To make full use of the information in the three wavelengths we construct a composite CH distribution, which is more robust than distributions based on one wavelength. Using the composite CH dataset we discuss the temporal evolution of CHs during the Solar Cycles 23 and 24.  相似文献   

Tributyltin in blood of marine fish collected from a coastal area of northern Kyushu, Japan     

Miki S  Ikeda K  Oba Y  Satone H  Honda M  Shimasaki Y  Onikura N  Arakawa O  Oshima Y 《Marine pollution bulletin》2011,62(11):2533-2536

We investigated levels of the pollutant tributyltin (TBT) in blood of pufferfishes (six species), Japanese sea perch, red sea bream, Japanese common goby, Japanese flounder, rockfish, conger eel, and sea mullet collected off the coast of northern Kyushu, Japan. We found considerable levels of TBT (1.4-190 ng/mL) accumulated in the blood of these fish. Blood TBT concentrations were 1.3-22.5 times liver concentrations and 4.9-78 times muscle concentrations, except in conger eel and mullet. We detected TBT (16-111 ng/mL-blood) in the plasma of the fine-patterned puffer (Takifugupoecilonotus) year-round, without any apparent seasonal trend. These results suggest that fish inhabiting coastal areas of Kyushu, Japan, continue to be contaminated with TBT.  相似文献   

Contamination status of POPs and BFRs and relationship with parasitic infection in finless porpoises (Neophocaena phocaenoides) from Seto Inland Sea and Omura Bay, Japan     

Isobe T  Oshihoi T  Hamada H  Nakayama K  Yamada TK  Tajima Y  Amano M  Tanabe S 《Marine pollution bulletin》2011,63(5-12):564-571

Contamination status of brominated flame retardants (BFRs) and persistent organic pollutants (POPs) in blubber of finless porpoises (Neophocaena phocaenoides) stranded along the coasts of Seto Inland Sea and Omura Bay in Japan were investigated. Levels of PCBs, DDTs and CHLs were significantly higher than those of HCHs, HCB, PBDEs and HBCDs. Concentrations of PBDEs and HBCDs, as well as organochlorine compounds in males increased with body length (p<0.05). Among 14 PBDE congeners analyzed, BDE-47 was the predominant, which is similar to those generally reported in biota. PBDEs, HBCDs and PCBs showed no obvious temporal trend in concentrations during the study period, suggesting continuous environmental release of these chemicals. On the other hand, levels of DDT, CHLs and HCHs have decreased. Concentrations of PCBs in liver trematode infected individuals were significantly higher than those in not infected individuals, implying there could be a relationship between contaminant levels and parasitic infection.  相似文献   

High-pressure Raman studies and heat capacity measurements on the MgSiO<Subscript>3</Subscript> analogue CaIr<Subscript>0.5</Subscript>Pt<Subscript>0.5</Subscript>O<Subscript>3</Subscript>     

Shigeto Hirai  Yohei Kojima  Hiroaki Ohfuji  Norimasa Nishiyama  Tetsuo Irifune  Stephan Klemme  Geoffrey Bromiley  J. Paul Attfield 《Physics and Chemistry of Minerals》2011,38(8):631-637

Raman spectroscopy and heat capacity measurements have been used to study the post-perovskite phase of CaIr_0.5Pt_0.5O₃, recovered from synthesis at a pressure of 15 GPa. Laser heating CaIr_0.5Pt_0.5O₃ to 1,900 K at 60 GPa produces a new perovskite phase which is not recoverable and reverts to the post-perovskite polymorph between 20 and 9 GPa on decompression. This implies that Pt-rich CaIr_1−xPt_xO₃ perovskites including the end member CaPtO₃ cannot easily be recovered to ambient pressure from high P–T synthesis. We estimate an increase in the thermodynamic Grüneisen parameter across the post-perovskite to perovskite transition of 34%, of similar magnitude to those for (Mg,Fe)SiO₃ and MgGeO₃, suggesting that CaIr_0.5Pt_0.5O₃ is a promising analogue for experimental studies of the competition in energetics between perovskite and post-perovskite phases of magnesium silicates in Earth’s lowermost mantle. Low-temperature heat capacity measurements show that CaIrO₃ has a significant Sommerfeld coefficient of 11.7 mJ/mol K² and an entropy change of only 1.1% of Rln2 at the 108 K Curie transition, consistent with the near-itinerant electron magnetism. Heat capacity results for post-perovskite CaIr_0.5Rh_0.5O₃ are also reported.  相似文献   

Significance of an amorphous SiO2 phase in a pseudomorph after coesite enclosed in garnet from ultrahigh‐pressure eclogite,Su–Lu Belt,eastern China          下载免费PDF全文

Tomoki Taguchi  Akira Miyake  Masaki Enami  Yohei Igami 《Journal of Metamorphic Geology》2018,36(7):843-854

Here, we report the first discovery of an amorphous SiO₂ phase (APSI phase) in a pseudomorph after coesite included in garnet from an ultrahigh‐pressure (UHP) eclogite from the Su–Lu metamorphic belt, eastern China. Using transmission electron microscopy, Raman spectroscopy and selected area electron diffraction, we show that the internal structure of the pseudomorph consists of an APSI phase with nano/submicrocrystalline particles of quartz and a polycrystalline K‐bearing fibrous sheet‐silicate phase (KFSS phase). The APSI phase‐bearing aggregates included in the garnet might have formed by reactions involving a supercritical fluid during exhumation by the following processes: (1) the development of radial cracks within the host garnet by the phase transition of coesite to quartz; (2) the decomposition of a part of the pseudomorph following infiltration of supercritical fluid; (3) the precipitation of the KFSS phase from the fluid phase during subsequent exhumation and cooling, which was likely promoted by a change in the metamorphic fluid from supercritical and/or subcritical to aqueous fluid; and (4) the rapid precipitation of the APSI phase under a metastable (non‐equilibrium) state, such as quenching, during a later stage of the exhumation. Whether the APSI phase generally formed during exhumation and survived widely throughout the Su‐Lu terrane is unknown. However, the presence of the APSI phase in a UHP eclogite provides new insight into the geodynamic phenomena occurring at continental collision zones.  相似文献   

Characterization of the near-Earth Asteroid 2002 NY₄₀     

Lewis C. Roberts Jr.  Doyle T. Hall  John V. Lambert  John L. Africano  Keith T. Knox  Jacob K. Barros  Kris M. Hamada  Dennis Liang  Paul F. Sydney  Paul W. Kervin 《Icarus》2007,192(2):469-474

In August 2002, the near-Earth Asteroid 2002 NY₄₀, made its closest approach to the Earth. This provided an opportunity to study a near-Earth asteroid with a variety of instruments. Several of the telescopes at the Maui Space Surveillance System were trained at the asteroid and collected adaptive optics images, photometry and spectroscopy. Analysis of the imagery reveals the asteroid is triangular shaped with significant self-shadowing. The photometry reveals a 20-h period and the spectroscopy shows that the asteroid is a Q-type.  相似文献   

Air-sea gas transfer in a shallow,flowing and coastal environment estimated by dissolved inorganic carbon and dissolved oxygen analyses     

Osamu Abe  Atsushi Watanabe  V. V. S. S. Sarma  Yohei Matsui  Hiroya Yamano  Naohiro Yoshida  Toshiro Saino 《Journal of Oceanography》2010,66(3):363-372

We estimated gas exchange rates in Kabira Reef at Ishigaki Island, southwest Japan, using a mass balance calculation with dual “biological” tracers: dissolved inorganic carbon (DIC) and dissolved oxygen (DO). The nighttime results allowed us to obtain reasonable gas transfer velocity k _w values, all of which exceeded those obtained in wind-dominant studies. The difference is likely due to the contribution of turbulence generated by the interaction between the current and bottom topography. The k _w obtained during high tides is consistent with that reported by Raymond and Cole (2001), whereas k _w during low tides is significantly higher, which seems to be caused by enhanced friction with the bottom of the reef and/or bubble-induced gas transfer by wave breaking at the reef crest.  相似文献   

A preliminary report on the frequency characteristics of near-surface layers in the vicinity of the high dam lake     

E. Refai  M. Maamoun  M. El-Difrawy  S. Attia  G. Hamada 《Journal of Geodynamics》1991,14(1-4)

The frequency characteristics of near-surface sediments obtained from small scale S-wave refraction measurements conducted at two sites in the Garf Hussein area, contiguous to the High Dam Lake, South of Aswan, have shown drastic changes in the frequency-selective amplification of horizontal ground motion within a relatively short surface distance. This effect is attributed mainly to such factors as the variation in layer thickness and the presence or absence of soft alluvial deposits.These results indicate that movements initiated deep in the earth's crust may not be faithfully reflected on the ground surface. As geodetic work principally involves monitoring relative horizontal and vertical displacements on the earth's surface with time, geodesists are advised to take the spectral response of the ground into consideration.  相似文献   

Simulating bubble number density of rhyolitic pumices from Plinian eruptions: constraints from fast decompression experiments     

Morihisa Hamada  Didier Laporte  Nicolas Cluzel  Kenneth T. Koga  Tatsuhiko Kawamoto 《Bulletin of Volcanology》2010,72(6):735-746

Decompression experiments of a crystal-free rhyolitic liquid with ≈ 6.6 wt. % H₂O were carried out at a pressure range from 250 MPa to 30–75 MPa in order to characterize effects of magma ascent rate and temperature on bubble nucleation kinetics, especially on the bubble number density (BND, the number of bubbles produced per unit volume of liquid). A first series of experiments at 800°C and fast decompression rates (10–90 MPa/s) produced huge BNDs (≈ 2 × 10¹⁴ m⁻³ at 10 MPa/s ; ≈ 2 × 10¹⁵ m⁻³ at 90 MPa/s), comparable to those in natural silicic pumices from Plinian eruptions (10¹⁵–10¹⁶ m⁻³). A second series of experiments at 700°C and 1 MPa/s produced BNDs (≈ 9×10¹² m⁻³) close to those observed at 800°C and 1 MPa/s (≈ 6 × 10¹² m⁻³), showing that temperature has an insignificant effect on BNDs at a given decompression rate. Our study strengthens the theory that the BNDs are good markers of the decompression rate of magmas in volcanic conduits, irrespective of temperature. Huge number densities of small bubbles in natural silicic pumices from Plinian eruptions imply that a major nucleation event occurs just below the fragmentation level, at which the decompression rate of ascending magmas is a maximum (≥ 1 MPa/s).  相似文献