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61.
T. Hattori T. Matsuda T. Tsuchiya T. Nagai T. Yamanaka 《Physics and Chemistry of Minerals》1999,26(3):212-216
In order to confirm the possible existence of FeGeO3 perovskite, we have performed in situ X-ray diffraction measurements of FeGeO3 clinopyroxene at pressures up to 40 GPa at room temperature. The transition of FeGeO3 clinopyroxene into orthorhombic perovskite is observed at about 33GPa. The cell parameters of FeGeO3 perovskite are a=4.93(2) Å, b=5.06(6) Å, c=6.66(3) Å and V=166(3) Å3 at 40 GPa. On release of pressure, the perovskite phase transformed into lithium niobate structure. The previously reported decomposition process of clino-pyroxene into Fe2GeO4 (spinel)+GeO2 (rutile) or FeO (wüstite) +GeO2 (rutile) was not observed. This shows that the transition of pyroxene to perovskite is kinetically accessible compared to the decomposition processes under low-temperature pressurization. 相似文献
62.
Concentrations of dissolved and particulate organic carbon (DOC and POC) were documented in 1996–1997 at 4 different trophic
state stations in Donghu Lake, a typical shallow eutrophic lake along the Changjiang River's middle reaches. The mean concentrations
of DOC were 15.11±3.26, 15.19±4.24, 14.27±3.43, and 13.31±3.30 mg/L in Station I, II, III, and IV, respectively. The DOC concentrations
of the studied area were very similar to that in other lakes along the Changjiang River's middle reaches. The POC mean of
the whole lake was 5.01 mg/L due to the large amount of organic detritus of both allochthonous and autochthonous origin. Significant
linear relationship was found between POC and chlorophyll a at all 4 stations, which presumably reflect that phytoplankton,
its exudates and its metabolic products were the main contributors to the POC pool in the water column. The slope of such
linear relationship at Station IV was significantly steeper than that at Station I, II and III. In addition, the DOC/POC ratios
(mean value: 4.40) indicated that the organic detritus was the most important component of the particulate organic matter;
in other works, next to organic detritus, phytoplankton dominated the particulate organic matter in Donghu Lake.
Project 39770146, 39430101 supported by NSFC and the State Key Laboratory of Freshwater Ecology and Biotechnology, affiliated
to the Institute of Hydrobiology, Chinese Academy of Sciences. 相似文献
63.
Mucus films, flocs or foams consisting of fine sand, algae and detritus frequently occur in the surface waters of rocky intertidal reef flats during incoming tide. These masses are referred to as mucus aggregates. We examined the developmental process of mucus aggregates and their abundance, distribution, migration and trophic composition. The trophic composition of mucus aggregates was then compared to those of sediments to evaluate their potential nutritional value for benthic animals. The organic matter content, chlorophyll a concentration, microalgal density and bacteria-derived fatty acid contents of mucus aggregates were higher than those observed in sediment, suggesting that mucus aggregates contain not only high levels of organic matter but also dense concentrations of microalgae and bacteria; therefore, mucus aggregates may serve as a qualitatively more energetic food source for benthic fauna compared to sediments. Benthic diatoms were the most abundant organisms in mucus aggregates. Large numbers of diatoms were trapped in fine mineral particles and mucilage-like strings, suggesting that a portion of the mucus is secreted by these benthic microalgae.Mucus aggregate accounted for only 0.01-3.9% of the daily feeding requirements of the dominant detritivore, Ophiocoma scolopendrina (Echinodermata: Ophiuroidea) over the entire sampling area. In contrast, for the species population on the back reef, where mucus aggregates ultimately accumulate, mucus aggregates provided from 0.4 to 113.3% of food for this species. These results suggest that mucus aggregate availability varies spatiotemporally and that they do not always provide adequate food sources for O. scolopendrina populations. 相似文献
64.
A framework for economic loss estimation due to seismic transportation network disruption: a spatial computable general equilibrium approach 总被引:4,自引:4,他引:0
This paper presents a framework for assessing the economic impact of disruption in transportation that can relate the physical
damage to transportation networks to economic losses. A spatial computable general equilibrium (SCGE) model is formulated
and then integrated with a transportation model that can estimate the traffic volumes of freight and passengers. Economic
equilibrium under a disruption in the transportation network is computed subject to the condition that the adjustment of labor
and capital inputs is restricted; the model reflects slow adjustment of these linked to the state of recovery. As a case study,
the model reviews the large Niigata-Chuetsu earthquake of 2004. Considering the damage to the transportation infrastructure,
the model indicates the extent of the economic losses arising from the earthquake distributed over regions as a consequence
of the intra- and interregional trade in a regional economy. The results show that 20% of the indirect losses occur in the
Niigata region directly affected by the earthquake, whereas 40% of the total losses are experienced in the Kanto region and
non-negligible losses reach rather remote zones of the country such as Okinawa. 相似文献
65.
Youta?SugaiEmail author Kenji?Tsuchiya Victor?S.?Kuwahara Shinji?Shimode Kazuhiro?Komatsu Akio?Imai Tatsuki?Toda 《Journal of Oceanography》2016,72(4):577-587
This study aimed to clarify the vertical differences in bacterial growth and grazing pressure on bacteria by heterotrophic nanoflagellates (HNF) and to identify the controlling factors of bacterial growth in temperate coastal waters of Sagami Bay, Japan. In addition to environmental factors, the annual monthly variations in bacterial growth rate (BGR) and the relative abundance of bacteria to HNF (BA/HNFA) were investigated in the euphotic and disphotic layers between May 2012 and May 2013. Significant vertical differences in BGR and BA/HNFA were evident between the two layers during the thermal stratification times of May to October 2012 and April to May 2013. BGR indicated significantly stronger limitation of bacterial growth in the euphotic layer compared to the disphotic layer. In contrast, significantly lower BA/HNFA was observed in the euphotic layer, suggesting significantly higher grazing pressure on bacteria by HNF. However, significant differences in BGR and BA/HNFA were not observed between the two layers from November 2012 to Match 2013, when the water column was well-mixed vertically due to the cooling and wind-induced mixing of surface water. This study indicates that bacteria in the euphotic layer grow less actively and are more vulnerable to predatory grazing by HNF relative to the disphotic layer during the stratification period. Further, multiple regression analyses indicate that bacterial growth was most controlled by the concentrations of chlorophyll a and dissolved organic carbon in the euphotic and disphotic layers, respectively. 相似文献
66.
67.
Beach erosion has advanced in many countries of the world, especially in Japan, because of a decrease in sediment sources from rivers and a lack of longshore sediment transport from the adjacent coasts due to coastal structures. The former cause concerns the reduction of river deltas due to a decrease in sediment input from the river. Two timescales important in beach erosion, a longer timescale which concerns a change in the location of the river mouth, and a shorter one which is due to a decrease in longshore sediment transport, are discussed in the formation and reduction of the delta of the Kurobe River. Based on these timescales, beach erosion control is considered. 相似文献
68.
Lost primordial continents 总被引:7,自引:2,他引:5
We investigate the bulk density variations of some representative compositions for the lower mantle based on the pressure–volume–temperature equation of state of the constituent mineral phases. The density variations of pyrolite, harzburgite, mid-ocean ridge basalt (MORB), tonalite–trondhjemite–granodiorite (TTG), and anorthosite are studied at a temperature of 300 K and at lower mantle pressures. The density of MORB is greater than that of pyrolite throughout the lower mantle, while the density of harzburgite is slightly lower than that of pyrolite. The density of anorthosite is comparable to that of pyrolite in the lower mantle in general, and greater in the lowermost mantle, while the density of TTG is lower than pyrolite throughout the lower mantle. The above results have important implications for the fate of primordial continents, TTG and anorthosite crust. While subducted TTG might be stagnant in the mantle transition zone, dense subducted anorthositic crust could be expected to sink to the core–mantle boundary (CMB) and thus might be a major component of the D" layer immediately above the CMB. Thus, we propose that significant bodies of continental material could be present in the mantle in the transition zone and immediately above the CMB, in addition to the continents on the Earth's surface. 相似文献
69.
Ichiro Takeuchi Kaoruko Mizukawa Tokutaka Ikemoto Kotaro Tsuchiya 《Marine pollution bulletin》2009,58(5):663-9029
Biomagnification profiles of polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and polychlorinated biphenyls (PCBs) from the innermost part of Tokyo Bay, Japan were analyzed using stable carbon (δ13C) and nitrogen (δ15N) isotope ratios as guides to trophic web structure. δ15N analysis indicated that all species of mollusks tested were primary consumers, while decapods and fish were secondary consumers. Higher concentrations of PCBs occurred in decapods and fish than in mollusks. In contrast, concentrations of PAHs and alkylphenols were lower in decapods and fish than in mollusks. Unlike PCBs, whose concentrations largely increased with increasing δ15N (i.e. increasing trophic level), all PAHs and alkylphenols analyzed followed a reverse trend. Molecular weights of PAHs are lower than those of PCBs, therefore low membrane permeability caused by large molecular size is an unlikely factor in the “biodilution” of PAHs. Organisms at higher trophic levels may rapidly metabolize PAHs or they may assimilate less of them. 相似文献
70.
We simulated quartz-type GeO2 and investigated its high-pressure transformation using the molecular dynamics (MD) simulation method with a model potential. The calculated results under hydrostatic compression indicated that a pressure-induced amorphization of quartz-type GeO2 originated from the mechanical instability of the quartz lattice as, in previous theoretical studies of SiO2. Furthermore, quartz-type GeO2 directly transformed to a rutile-like structure with only subtle displacements of ions under σ
x
y
imposed shear stressed decompression. This is the first reproduction of the quartz-to-rutile transformation. A possible pathway
of this transition is proposed in this study.
Received: 14 April 1999 / Revised, accepted: 11 August 1999 相似文献