Changing anthropogenic influence on the Santa Monica Bay watershed     

Dojiri M  Yamaguchi M  Weisberg SB  Lee HJ 《Marine environmental research》2003,56(1-2):1-14

Santa Monica Bay is an open coastal embayment located directly seaward of Los Angeles, California. The Bay provides vital economic value through its water-dependent activities, such as swimming, diving, boating, and fishing. An increase from 100,000 residents in 1900 to 10 million in 2000 has imposed numerous environmental stressors on the Bay, including urbanization of the watershed. Pollutant discharges into the Bay increased throughout the early part of the century, but declined following passage of the Clean Water Act in 1972. Since that time, the predominant source of pollutant inputs has changed from point sources to non-point urban runoff. To assess how present-day and historical pollution interact to affect the environmental quality of Santa Monica Bay, three organizations collaborated on a multi-disciplinary study in 1997, towards which this volume is focused. This paper details the temporal patterns of anthropogenic influence on Santa Monica Bay to provide context for the papers that follow.  相似文献   

Difference characteristics of sea surface temperature observed by GLI and AMSR aboard ADEOS-II     

Kohtaro Hosoda  Hiroshi Murakami  Akira Shibata  Futoki Sakaida  Hiroshi Kawamura 《Journal of Oceanography》2006,62(3):339-350

This study compares infrared and microwave measurements of sea surface temperature (SST) obtained by a single satellite. The simultaneous observation from the Global Imager (GLI: infrared) and the Advanced Microwave Scanning Radiometer (AMSR: microwave) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) provided an opportunity for the intercomparison. The GLI-and AMSR-derived SSTs from April to October 2003 are analyzed with other ancillary data including surface wind speed and water vapor retrieved by AMSR and SeaWinds on ADEOS-II. We found no measurable bias (defined as GLI minus AMSR), while the standard deviation of difference is less than 1°C. In low water vapor conditions, the GLI SST has a positive bias less than 0.2°C, and in high water vapor conditions, it has a negative (positive) bias during the daytime (nighttime). The low spatial resolution of AMSR is another factor underlying the geographical distribution of the differences. The cloud detection problem in the GLI algorithm also affects the difference. The large differences in high-latitude region during the nighttime might be due to the GLI cloud-detection algorithm. AMSR SST has a negative bias during the daytime with low wind speed (less than 7 ms⁻¹), which might be related to the correction for surface wind effects in the AMSR SST algorithm.  相似文献   

The sudden disappearance of a dark filament observed on October 26, 1989     

Jun Kubota  Reizaburo Kitai  Ichiro Tohmura  Akira Uesugi 《Solar physics》1992,139(1):65-79

We present H monochromatic and spectroscopic observations of the sudden disappearance of a dark filament located near the center of the solar disk on October 26, 1989. The event was not associated with the flare activity. The dark filament first disintegrated into two loop-like components, and then each component successively showed ascending motion with a velocity greater than 30 km s^–1. Comparison of the H pictures taken before and after the start of this event suggests that the dark filament was originally composed of two magnetic flux loops.  相似文献   

X-ray observation of the Jovian impacts of comet Shoemaker - Levy 9     

Kentaro Terada  Hitoshi Negoro  Kiyoshi Hayashida  Shunji Kitamoto  Hiroshi Tsunemi  Hiroshi Oya  Takayuki Ono  Akira Morioka  Yuzuru Tawara  Toshifumi Mukai  Masahiro Hoshino  Toshio Terasawa 《Earth, Moon, and Planets》1994,66(1):75-81

An ASCA observation of the Jovian impact of the comet Shoemaker-Levy 9 is reported. Four impacts of H, L, Q1 and R were observed and four impacts of B, C, G, and Q2 were observed within 60 minutes after their impacts. No significant flaring of X-ray emission was observed. Upper limit X-ray fluxes of 90 % confidence level, averaged 5 minutes just after the impacts, were 2.4 × 10^–13 erg sec^–1 cm^–2, 3.5 × 10^–13 erg sec^–1 cm^–2, 1.6 × 10^–13 erg sec^–1 cm^–2 and 2.9 × 10^–13 erg sec^–1 cm^–2 for the impacts of H, L, Q1 and R, respectively, in the 0.5(0.7 for H and Q1)–10 keV energy range. However, a hint of X-ray enhancement around Jupiter from July 17 to July 19 was detected with about 2 6 × 10^–14 erg sec^–1 cm^–2 in the 0.5–10 keV energy range.  相似文献   

Performance of the complete travel-time equation of state at simultaneous high pressure and temperature     

Hartmut A. Spetzler  Akira Yoneda 《Pure and Applied Geophysics》1993,141(2-4):379-392

The complete travel-time equation of state (CT-EOS) is presented by utilizing thermodynamics relations, such as; $$K_T = K_S (1 + \alpha \gamma T)^{ - 1} , \gamma = \frac{{\alpha K_S }}{{\rho C_P }}, \left. {\frac{{\partial C_P }}{{\partial P}}} \right)_T = - \frac{T}{\rho }\left[ {\alpha ^2 + \left. {\frac{{\partial \alpha }}{{\partial T}}} \right)_P } \right], etc.$$ The CT-EOS enables us to analyze ultrasonic experimental data under simultaneous high pressure and high temperature without introducing any assumption, as long as the density, or thermal expansivity, and heat capacity are also available as functions of temperature at zero pressure. The performance of the CT-EOS was examined by using synthesized travel-time data with random noise of 10^?5 and 10^?4 amplitude up to 4 GPa and 1500 K. Those test conditions are to be met with the newly developed GHz interferometry in a gas medium piston cylinder apparatus. The results suggest that the combination of the CT-EOS and accurate experimental data (10^?4 in travel time) can determine thermodynamic and elastic parameters, as well as their derivatives with unprecedented accuracy, yielding second-order pressure derivatives (?² M/?P ²) of the elastic moduli as well as the temperature derivatives of their first-order pressure derivatives ?² M/?P?T). The completeness of the CT-EOS provides an unambiguous criterion to evaluate the compatibility of empirical EOS with experimental data. Furthermore because of this completeness, it offers the possibility of a new and absolute pressure calibration when X-ray (i.e., volume) measurements are made simultaneously with the travel-time measurements.  相似文献   

Experimental study on the velocity of fragments in collisional breakup     

Akira Fujiwara  Akimasa Tsukamoto 《Icarus》1980,44(1):142-153

The motion of fragments following a catastrophic destruction by either a normal or an oblique impact at 2.5–2.9 km sec^?1 into cubic and spherical basalt targets was studied with a high-speed framing camera. Velocities at the antipodes of the targets vary as (E/M)^0.75 (E = impact energy; M = target mass) and are lower than 200 m sec^?1 at E/M ? 10⁹ ergs g^?1. Excluding fine-grained particles from the impact site, 70 to 80% by mass fraction of the fragments have velocities lower than twice the antipodal velocity. Comminution and ejection energies wasted in this mass fraction were a few percent of the impact energy at E/M ? 5 × 10⁷ ergs g^?1. During a catastrophic impact into asteroids some of the fragmented bodies can be reconcentrated by mutual gravitation.  相似文献   

Dendritic cordierite in argillaceous hornfels from the Toki area,Gifu Prefecture,central Japan     

Akira Miyake 《Contributions to Mineralogy and Petrology》1990,104(4):390-396

Dendritic cordierite occurs in argillaceous hornfels from the Toki area, Gifu Prefecture, Japan. The cordierite crystal consists of c-arms elongated parallel to the c-axes and a-arms perpendicular to the c-axis. The latter arms could be divided into six kinds of untwinned a-arms with different growth directions elongated parallel to the respective a-axis and twinned a-arms elongated parallel to the (110) twin plane. A-arms branch out from c-arms or other a-arms with different growth directions and c-arms sometimes branch out from a-arms, leading to a tree-like structure. Each of the c-arms contains three kinds of domains related by a three-fold axis about the c-axis. These domains are irregularly distributed without any relation to the shape of the c-arm and the domain boundaries are of zigzag shape. This domain arrangement suggests that c-arms grew as hexagonal cordierite and were later transformed into orthorhombic cordierite. The fact that each untwinned a-arm has a fixed growth direction to its orientation suggests that the a-arms grew as an orthorhombic cordierite. From the growth directions of c- and a-arms, orthorhombic and hexagonal phases are considered to grow preferentially along the c- and a-axes, respectively. The branching of a new arm is explained by nucleation on an old arm with a different preferred growth direction. The preferential growth is discussed in terms of a significant chemical potential gradient of the cordierite component. This has been preserved in the mineral zoning observed in the matrix around the cordierite porphyroblast.  相似文献   

Controlled experiment in the ionosphere with a rocket-borne plasma gun     

Nobuki Kawashima  Susumu Sasaki  Osamu Kaneko  Akira Yamori  Ryo Okamura  Shoichi Okamura 《Planetary and Space Science》1978,26(4):367-373

A controlled active experiment was performed by a plasma gun on-board a rocket to study the plasma stream across the magnetic field in space. A mother and daughter system was employed. An 8 kV 0.8 μF (25 J) capacitor bank on the daughter rocket was discharged every 12 s and about 10¹⁶ ion and electron pairs were ejected. A plasma signal was detected on the electron temperature probe. The propagation speed of the plasma stream is estimated to be 10⁶ cm/s, considerably lower than that obtained in the prelaunch test. The amplitude of the plasma signal decays as the inverse square of the mutual distance between the mother and daughter rockets and this decay is much slower than the free streaming. The importance of the geomagnetic field on the plasma propagation in space is discussed.  相似文献   

Metallogenesis of Porphyry Cu Deposits of the Western Luzon Arc, Philippines: K-Ar ages, SO₃ Contents of Microphenocrystic Apatite and Significance of Intrusive Rocks     

Akira IMAI 《Resource Geology》2002,52(2):147-161

Abstract: K–Ar ages of the following porphyry Cu deposits in the western Luzon arc are determined: Lobo-Boneng (10.50.4 Ma), Santo Niño (9.50.3 Ma), Black Mountain (2.10.1 Ma), Dizon (2.50.2 Ma) and Taysan (7.30.2 Ma). Microphenocrys-tic apatite in the late Cenozoic intermediate to silicic intrusions associated with porphyry Cu deposits in the western Luzon arc contains sulfur as SO₃ detectable by electron probe microanalyzer. Sulfur is supposed to have been accommodated dominantly as oxidized species in oxidizing hydrous magmas that generated porphyry Cu deposits. Likewise, such high SO₃ contents in microphenocrystic apatite are common characteristics of the intermediate to silicic magmatism of the western Luzon arc, from tonalitic rocks of the Luzon Central Cordillera of about 15 Ma to an active magmatism at Mount Pinatubo. Thus, the western Luzon arc has been generating porphyry Cu mineralization associated with oxidizing hydrous intermediate to silicic magmatism related to eastward subduction, since Miocene to the present day. Intermediate to silicic rocks since 15 Ma to present-day western Luzon arc generally show high whole-rock Sr/Y ratio ranging from 20 to 184. However, porphyry Cu deposit is not necessarily related to the rocks that show higher Sr/Y ratios compared to the other barren rocks in the western Luzon arc. The characteristics of the intermediate to silicic magma associated with porphyry Cu deposit are not attributed to the composition of the source material of the magma, but to the properties defined by the high activity of oxidized species of sulfur in the fluid phase that is encountered during the generation of intermediate to silicic magmas.  相似文献   

Attenuation of coda waves and Q _c value beneath the Chengdu telemetered seismic network     

Jian Zeng  Tian-Chang Chen  Wei-Bin Han  Jun Fan  Si-Hua Zheng  Akira Hasegawa  Shigeki Horiuchij  Satoshi Matsumoto 《地震学报(英文版)》1997,10(3):313-320

Based on the single scattering model of coda power spectrum analysis, digital waveform data of 50 events recorded by the real-time processing system of the Chengdu telemetry network are analyzed to estimate the Q _c values of earth medium beneath the Chengdu telemetry network for several specified frequencies. It is found that the Q _c shows the frequency dependency in the form of Q _c = Q ₀ f ⁿ in the range of 1.0 to 20.0Hz. Estimated Q ₀ ranges from 60.83 to 178.05, and n is found to be 0.713 to 1.159. The average value of Q ₀ and n are 117 and 0.978 respectively. This result indicates the strong frequency dependency of the attenuation of coda waves beneath the Chengdu telemetry network. Comparing with the results obtained in other regions of the world, it is found that Q ₀ ⁻¹ value and its change with frequency are similar to those in regions with strong tectonic activity. This subject is supported by the Ministry of Personnel, China for partly sponsoring.  相似文献