Reproductive biology and seasonality of the Indo-Australasian mysid Mesopodopsis orientalis (Crustacea: Mysida) in a tropical mangrove estuary,Malaysia     

Yukio Hanamura  Ryon Siow  Phaik-Ean Chee 《Estuarine, Coastal and Shelf Science》2008

A year-round survey of the tropical shallow-water mysid Mesopodopsis orientalis (Tattersall, 1908) (Crustacea, Mysidacea) was conducted in the Merbok mangrove estuary, northwestern Peninsular Malaysia. The mysid formed dense aggregations at the river's edge close to the mangrove forest during the daytime, but very few were captured elsewhere in the estuary system. The sampled population was found in a wide range of salinities from 16 to 32, demonstrating broad euryhalinity, and the number of the catch at the littoral zone ranged from 11.8 to 2273 ind m⁻². The overall annual mean was 709.2 ind m⁻². Females predominated over males in the entire population, and brooding females were present at every monthly sample, indicating that reproduction is continuous year round. The clutch size positively correlated with female body length. The diameter of eggs (Stage I embryos) was unaffected by the seasonality and independent of the maternal size within an observed size range. The life history pattern of the estuarine population of M. orientalis showed close similarity to that of the coastal counterpart. However, the former was found to produce fewer but larger eggs, and the specimens in this population were larger than those in the coastal population at the embryo, juvenile, and adult stages. This evidence indicates that the life history features of the estuarine population would differ to some degree from those of the coastal counterpart.  相似文献   

Magmatic inclusions and felsic clasts in the Dar al Gani 319 polymict ureilite     

Yukio IKEDA  Martin PRINZ 《Meteoritics & planetary science》2001,36(4):481-499

Abstract— Magmatic inclusions occur in type II ureilite clasts (olivine‐orthopyroxene‐augite assemblages with essentially no carbon) and in a large isolated plagioclase clast in the Dar al Gani (DaG) 319 polymict ureilite. Type I ureilite clasts (olivine‐pigeonite assemblages with carbon), as well as other lithic and mineral clasts in this meteorite, are described in Ikeda et al.(2000). The magmatic inclusions in the type II ureilite clasts consist mainly of magnesian augite and glass. They metastably crystallized euhedral pyroxenes, resulting in feldspar component‐enriched glass. On the other hand, the magmatic inclusions in the large plagioclase clast consist mainly of pyroxene and plagioclase, with a mesostasis. They crystallized with a composition along the cotectic line between the pyroxene and plagioclase liquidus fields. DaG 319 also contains felsic lithic clasts that represent various types of igneous lithologies. These are the rare components not found in the common monomict ureilites. Porphyritic felsic clasts, the main type, contain phenocrysts of plagioclase and pyroxene, and their groundmass consists mainly of plagioclase, pyroxene, and minor phosphate, ilmenite, chromite, and/or glass. Crystallization of these porphyritic clasts took place along the cotectic line between the pyroxene and plagioclase fields. Pilotaxitic felsic clasts crystallized plagioclase laths and minor interstitial pyroxene under metastable conditions, and the mesostasis is extremely enriched in plagioclase component in spite of the ubiquitous crystallization of plagioclase laths in the clasts. We suggest that there are two crystallization trends, pyroxene‐metal and pyroxene‐plagioclase trends, for the magmatic inclusions and felsic lithic clasts in DaG 319. The pyroxene‐metal crystallization trend corresponds to the magmatic inclusions in the type II ureilite clasts and the pilotaxitic felsic clasts, where crystallization took place under reducing and metastable conditions, suppressing precipitation of plagioclase. The pyroxene‐plagioclase crystallization trend corresponds to the magmatic inclusions in the isolated plagioclase clast and the porphyritic felsic clasts. This trend developed under oxidizing conditions in magma chambers within the ureilite parent body. The felsic clasts may have formed mainly from albite component‐rich silicate melts produced by fractional partial melting of chondritic precursors. The common monomict ureilites, type I ureilites, may have formed by the fractional partial melting of alkali‐bearing chondritic precursors. However, type II ureilites may have formed as cumulates from a basaltic melt.  相似文献   

A method for analyzing the segregation between point distributions: statistical tests and consideration of attributes     

Yukio Sadahiro 《Journal of Geographical Systems》2015,17(1):29-60

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Effects of experimental aqueous alteration on the abundances of argon‐rich noble gases in the Ningqiang carbonaceous chondrite     

Yukio Yamamoto  Ryuji Okazaki  Tomoki Nakamura 《Meteoritics & planetary science》2006,41(4):541-551

Abstract— Ar‐rich noble gases, the so‐called “subsolar” noble gases, are a major component of heavy primordial noble gases in unequilibrated ordinary chondrites and some classes of anhydrous carbonaceous chondrites, whereas they are almost absent in hydrous carbonaceous chondrites that suffered extensive aqueous alteration. To understand the effects of aqueous alteration on the abundance of Ar‐rich noble gases, we performed an aqueous alteration experiments on the Ningqiang type 3 carbonaceous chondrite that consists entirely of anhydrous minerals and contains Ar‐rich noble gases. Powdered samples and deionized neutral water were kept at 200 °C for 10 and 20 days, respectively. Mineralogical analyses show that, during the 10‐day alteration, serpentine and hematite formed at the expense of olivine, low‐Ca pyroxene, and sulfide. Noble gas analyses show that the 10‐day alteration of natural Ningqiang removed 79% of the primordial ³⁶Ar, 68% of the ⁸⁴Kr, and 60% of the ¹³²Xe, but only 45% of the ⁴He and 53% of the primordial ²⁰Ne. Calculated elemental ratios of the noble gases removed during the 10‐day alteration are in the range of those of Ar‐rich noble gases. These results indicate that Ar‐rich noble gases are located in materials that are very susceptible to aqueous alteration. In contrast, heavy primordial noble gases remaining in the altered samples are close to Q gas in elemental and isotope compositions. This indicates that phase Q is much more resistant to aqueous alteration than the host phases of Ar‐rich noble gases. In the 20‐day sample, the mineralogical and noble gas signatures are basically similar to those of the 10‐day sample, indicating that the loss of Ar‐rich noble gases was completed within the 10‐day alteration. Our results suggest that almost all of the Ar‐rich noble gases were lost from primitive asteroids during early, low‐temperature aqueous alteration.  相似文献   

    

Yukio Niimi 《Celestial Mechanics and Dynamical Astronomy》1982,26(2):179

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Multiple sulfur isotope chemostratigraphy across the Permian–Triassic boundary at Chaotian,China: Implications for a shoaling model of toxic deep-waters     

Masafumi Saitoh  Yuichiro Ueno  Yukio Isozaki  Naohiro Yoshida 《Island Arc》2021,30(1):e12398

Previous studies on multiple sulfur isotopes (³²S, ³³S, and ³⁴S) in sedimentary pyrite at the end-Permian suggested a shoaling of anoxic/sulfidic deep-water contributing to the extinction. This scenario is based on an assumption that the sedimentary sulfur cycle was largely controlled by benthos activity, though a stratigraphic correlation between the sulfur records and ichnofabrics of the sediments at the end-Permian has not yet been examined. We report the multiple sulfur isotopic composition of pyrite in the Permian–Triassic boundary interval at Chaotian, South China. Our data can be generally explained by a mixing of sulfur in sulfide from two different sources: one produced via sulfate reduction in an open system with respect to sulfate and the other produced in a closed system. In particular, the former with the substantially low δ³⁴S (<−40 ‰) and high ∆³³S (up to +0.100 ‰) values was likely produced via water-mass sulfate reduction or via sulfate reduction in oxic sediments with common burrows. The frequent occurrence of small pyrite framboids (mostly <5 μm in diameter) in the Lopingian (Late Permian) Dalong Formation of deep-water facies supports the enhanced water-mass sulfate reduction in an anoxic deep-water mass. The negative ∆³³S values are observed only in the oxic limestones, and no substantial ∆³³S change is observed across the extinction horizon despite of the disappearance of bioturbation. Our results are apparently inconsistent with the previous shoaling model. We expand the model and infer that, when the deep-water was sulfidic and its shoaling rate was high, a substantial amount of hydrogen sulfide (H₂S) was supplied onto the shelf via the shoaling; that resulted in the positive ∆³³S value of the bulk sediments. The observed ∆³³S variation on a global scale suggests a substantial variation in H₂S concentration and/or in upwelling rate of shoaling deep-waters during the Permian–Triassic transition.  相似文献   

Petrology of the Asuka 881931 ureilite with special reference to crystallization of interstitial silicate melt     

Yukio IKEDA 《Meteoritics & planetary science》1999,34(4):625-636

Abstract— The Asuka 881931 meteorite is an unbrecciated ferroan ureilite and consists mainly of equi—granular olivine and pigeonite grains, a metal—sulfide network, interstitial silicates, and glass. Peripheral portions of equigranular olivine grains are often replaced by fine-grained forsterite—metal aggregates and sometimes by fine-grained enstatite—metal aggregates. These aggregates may have been produced from the equigranular olivine by reduction. Peripheral portions of equigranular pigeonite grains also are sometimes replaced by fine-grained orthopyroxene aggregates with tiny patches of Si-rich glass and may have been produced from the pigeonite by reduction reaction with silicate melt. Interstitial silicates are mainly orthopyroxene, magnesian pigeonite, high-Ca pyroxene (diopside/fassaite), and CaO-poor enstatite; and they crystallized from interstitial silicate melt. Interstitial glass is classified into two types—-Si-poor and Si-rich. The Si-poor glass is always in contact with equigranular olivine, but the Si-rich glass never contacts equigranular olivine and is in contact with pyroxene and the metal—sulfide network. Both types of glass were produced from an original interstitial silicate melt, but the Si-poor glass formed mainly by fractional crystallization of pyroxenes, and the Si-rich glass may have formed by addition of Si mainly from nearby metal—sulfide melt, as well as crystallization of pyroxenes. The Si-poor and Si-rich melts were finally quenched as interstitial glasses under rapid cooling conditions.  相似文献   

Accuracy of areal interpolation: A comparison of alternative methods   总被引：3，自引：0，他引：3  

Yukio Sadahiro 《Journal of Geographical Systems》1999,1(4):323-346

This paper discusses the accuracy of spatial data estimated by areal interpolation, a process of transferring data from one zonal system to another. A stochastic model is proposed which represents areal interpolations in diverse geographic situations. The model is used to examine the relationship between estimation accuracy and the spatial distribution of estimation error from a theoretical viewpoint. The analysis shows that the uniformity in error distribution improves the accuracy of areal interpolation. Four areal interpolation methods are then assessed through numerical examinations. From this it is found that the accuracy of simple interpolation methods heavily depends on the appropriateness of their hypothetical distributions, whereas the accuracy of intelligent methods depends on the fitness of the range of supplementary data for that of true distribution. Received: 19 February 1999/Accepted 17 September 1999  相似文献   

An operational modal analysis method in frequency and spatial domain   总被引：3，自引：0，他引：3  

王彤张令弥  田村幸雄 《地震工程与工程振动(英文版)》2005,4(2):295-300

A frequency and spatial domain decomposition method （FSDD） for operational modal analysis （OMA） is presented in this paper, which is an extension of the complex mode indicator function （CMIF） method for experimental modal analysis （EMA）. The theoretical background of the FSDD method is clarified, Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density （PSD） is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.  相似文献   

Illawarra Reversal: The fingerprint of a superplume that triggered Pangean breakup and the end-Guadalupian (Permian) mass extinction   总被引：1，自引：1，他引：0  

Yukio Isozaki   《Gondwana Research》2009,15(3-4):421-432

The Permian magnetostratigraphic record demonstrates that a remarkable change in geomagnetism occurred in the Late Guadalupian (Middle Permian; ca. 265 Ma) from the long-term stable Kiaman Reverse Superchron (throughout the Late Carboniferous and Early-Middle Permian) to the Permian–Triassic Mixed Superchron with frequent polarity changes (in the Late Permian and Triassic). This unique episode called the Illawarra Reversal probably reflects a significant change in the geodynamo in the outer core of the planet after a 50 million years of stable geomagnetism. The Illawarra Reversal was likely led by the appearance of a thermal instability at the 2900 km-deep core–mantle boundary in connection with mantle superplume activity. The Illawarra Reversal and the Guadalupian–Lopingian boundary event record the significant transition processes from the Paleozoic to Mesozoic–Modern world. One of the major global environmental changes in the Phanerozoic occurred almost simultaneously in the latest Guadalupian, as recorded in 1) mass extinction, 2) ocean redox change, 3) sharp isotopic excursions (C and Sr), 4) sea-level drop, and 5) plume-related volcanism. In addition to the claimed possible links between the above-listed environmental changes and mantle superplume activity, I propose here an extra explanation that a change in the core's geodynamo may have played an important role in determining the course of the Earth's surface climate and biotic extinction/evolution. When a superplume is launched from the core–mantle boundary, the resultant thermal instability makes the geodynamo's dipole of the outer core unstable, and lowers the geomagnetic intensity. Being modulated by the geo- and heliomagnetism, the galactic cosmic ray flux into the Earth's atmosphere changes with time. The more cosmic rays penetrate through the atmosphere, the more clouds develop to increase the albedo, thus enhancing cooling of the Earth's surface. The Illawarra Reversal, the Kamura cooling event, and other unique geologic phenomena in the Late Guadalupian are all concordantly explained as consequences of the superplume activity that initially triggered the breakup of Pangea. The secular change in cosmic radiation may explain not only the extinction-related global climatic changes in the end-Guadalupian but also the long-term global warming/cooling trend in Earth's history in terms of cloud coverage over the planet.  相似文献