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42.
澳大利亚东南部悉尼盆地沉积层序中，放射性年龄测定和同位素地层学的新成果得出了没位置的Ｐ／Ｔ界线。在澳大利亚东南部，２５１Ｍａ前的时间界线是植物群分异度和地方性种类突然减少，Ｇｌｏｓｓｏｐｔｅｒｉｓ植物群绝灭的时代。早三叠世植物分异度低，以石松类和伏腊杉针叶树为主。 相似文献
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Biomarkers are generally applied to detect pollution in environmental monitoring. Such biological responses should accurately reflect the stress over time in a quantitative manner. As such, the initial and maximum responses induced by stress, as well as adaptation and recovery of these biomarkers, need to be fully understood or else erroneous false-negative or false-positive may be arrived. However, most of the biomarker studies only provided information on initially induced responses under different concentrations of toxicants, while biological adaptation and recovery were poorly known. In this study, the time required for induction, adaptation and recovery of lysosomal integrity in green-lipped mussel Perna viridis upon exposure to benzo[a]pyrene was investigated over a period of 62 days. Maximum induction occurred on day 6 when lysosomal integrity was significantly reduced by 51%, and no further change or adaptation was detected thereafter. When mussels were depurated in clean seawater after 18 days of exposure to benzo[a]pyrene, a gradual recovery was observed, with lysosomal integrity returning to its background level and showing a complete recovery after 20 days of depuration. Lysosomal integrity was significantly correlated with the body burden concentrations of benzo[a]pyrene and condition index of the mussels. The relatively fast induction (6 days) and recovery (20 days) without apparent adaptation suggested that lysosomal integrity in P. viridis can serve as a good biomarker in biomonitoring, as its response is not likely to generate both false-negative and false-positive results. 相似文献
45.
寻找南极洲与澳大利亚二叠系（P）——三叠系（T）边界碰撞的证据 总被引：1，自引：0，他引：1
１ 南极洲与澳洲的Ｐ－Ｔ边界Ｐ－Ｔ边界最可能的海洋层型层位在首次出现牙形石Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ的中国梅山剖面中,那里的边界和世界范围内其他海洋层序在碳酸盐和有机物δ１３Ｃ减少值上有明显的偏差。有机碳δ１３Ｃ的减少已在澳大利亚、南极洲和南非的非海相层序中用于确定Ｐ－Ｔ边界。位于边界的同位素特征也与以下因素有关：①煤层的突然性全球间断（Ｒｅｔａｌｌａｃｋ等,１９９６）;②形成煤的Ｇｌｏｓｓｏｐｔｅｒｉｓ大植物群及其独特的Ｖｅｒｔｅｂｒａｒｉａ根系的灭绝（Ｒｅｔａｌｌａｃｋ等,１９９７,１… 相似文献
46.
Trace organic contamination in biota collected from the Pearl River Estuary, China: a preliminary risk assessment 总被引：5，自引：0，他引：5
Wei S Lau RK Fung CN Zheng GJ Lam JC Connell DW Fang Z Richardson BJ Lam PK 《Marine pollution bulletin》2006,52(12):1682-1694
The marine ecosystem of the Pearl River Delta, located on the southern coast of China, has been heavily exploited following the rapid economic growth that has occurred since the 1980s. This investigation aimed to elucidate trace organic contamination in marine biota inhabiting the Pearl River Delta area. Biota samples, including green-lipped mussels (Perna viridis), oysters (Crassostrea rivularis) and shrimp (Penaeus orientalis) were sampled from 16 stations fringing the Estuary. Elevated concentrations (on a dry weight basis) of polycyclic aromatic hydrocarbons (27.8–1041.0 ng/g), petroleum hydrocarbons (1.7–2345.4 μg/g), polychlorinated biphenyls (2.1–108.8 ng/g), DDTs (1.9–79.0 ng/g), and hexachlorocyclohexanes (n.d.–38.4 ng/g) were recorded. A human health risk assessment was conducted to estimate the risk to local residents associated with the consumption of biota collected from the Pearl River Estuary. The results indicated that PCBs were at levels that may cause deleterious health effects in populations that consume large amounts of seafood. However, it would be instructive to establish health criteria for trace organic contaminants that are specific to the local populations, in order to derive a more accurate and relevant health risk assessment. 相似文献
47.
We compare the structure and substructure of dark matter halos in model universes dominated by collisional, strongly self-interacting dark matter (SIDM) and collisionless, weakly interacting dark matter (CDM). While SIDM virialized halos are more nearly spherical than CDM halos, they can be rotationally flattened by as much as 20% in their inner regions. Substructure halos suffer ram-pressure truncation and drag, which are more rapid and severe than their gravitational counterparts tidal stripping and dynamical friction. Lensing constraints on the size of galactic halos in clusters are a factor of 2 smaller than predicted by gravitational stripping, and the recent detection of tidal streams of stars escaping from the satellite galaxy Carina suggests that its tidal radius is close to its optical radius of a few hundred parsecs-an order of magnitude smaller than predicted by CDM models but consistent with SIDM models. The orbits of SIDM satellites suffer significant velocity bias, sigmaSIDM&solm0;sigmaCDM=0.85, and are more circular than CDM satellites, betaSIDM approximately 0.5, in agreement with the inferred orbits of the Galaxy's satellites. In the limit of a short mean free path, SIDM halos have singular isothermal density profiles; thus, in its simplest incarnation SIDM, is inconsistent with galactic rotation curves. 相似文献
48.
The grounding of the oil tanker Jessica off San Cristóbal Island, Galápagos, resulted in generally elevated rather than depressed densities of fishes adjacent to the wreck site 15 weeks post spill. Species richness of fishes declined along transects out from the wreck; however, patterns were inconsistent for different depth strata, with the most clearly defined decline evident for the intermediate 5-7 m depth stratum. Fish species attracted to the immediate wreck site, most notably the surgeonfish Prionurus laticlavius, the damselfish Microspathodon dorsalis and the angelfish Holacanthus passer, were considered to be responding either to the heterogeneity provided by the wreck structure or elevated densities of macroalgae. The fish community at the wreck site lay outside the range of variation for other sites investigated in the region; however, contrary to predictions of grounding impacts, the fish assemblage immediately adjacent to the wreckage showed greater faunal similarity to reference sites than did fish assemblage at 60-90 m distance from the grounding. 相似文献
49.