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171.
We inferred late Holocene Adélie penguin occupation history and population dynamics on Zolotov Island, Vestfold Hills, Antarctica, using geochemical data from a dated ornithogenic sediment core (ZOL4). Radiocarbon dates on fossil penguin bones in the core indicate that Adélie penguins occupied the island as early as 1,800 years before present (yr BP), following the retreat of the Sørsdal glacier. This occupation began ~1,200 years later than that observed at Ardley Island and King George Island, in the South Shetland Islands. Phosphorus was identified as the most indicative bio-element for penguin guano in core ZOL4, and was used to infer past penguin population dynamics. Around 1,800 years ago, the Adélie penguin populations at both Zolotov Island and Ardley Island increased rapidly and reached their highest levels ~1,000 yr BP. For the past ~900 years, the penguin populations at Zolotov Island have shown a general rising trend, with fluctuations, while those at Ardley Island have shown a moderate decreasing trend. The Adélie penguin populations at both Ardley Island and Zolotov Island showed a clear decline ~300 years ago, which we interpret as a response to the Little Ice Age, or a neoglacial cooling event.  相似文献   
172.
We present a case study of two successive filament eruptions at the southeast limb of the Sun observed by Solar Dynamics Observatory (SDO) on 2012 April 19. At the initial stage of the first filament (F1) eruption, one leg of the F1 moved toward the second filament (F2) and swept the F2. The interaction between two filaments occurred. After the leg of the F1 swept the F2, it returned from northeast to southwest following the F1 expansion. During the F1 eruption, the middle of the F1 exhibited an obvious twisted structure. The rising speed of the F1 was 85.6 km/s. The partial material of the F1 fell back to the surface along the other leg of the F1 after the F1 eruption and the falling speed was 311.6 km/s. A CME was observed by SOHO/LASCO after the F1 eruption. One of the bright flare ribbons and the dimming regions formed after the F1 eruption were found to move toward the F2. The propagation speeds of the flare ribbons were 4.7 km/s and 4.1 km/s and the propagation speeds of the dimmings were 3 km/s and 6.3 km/s. The small active region was emerging in the northern flank of the F2. The ejection and the falling plasma in the small active region produced the disturbance to the right part of the F2. When the F1 erupted, the large-scale overlying coronal loops of the F1 were pushed out toward the southeast of the Sun by its expanding. During the F1 eruption, the large-scale overlying coronal loops of the F2 began to open toward the southeast. Following the opening of the large-scale overlying coronal loops, the F2 became instable and began to erupt. The rising speed of the F2 was 300.1 km/s. A two-ribbon flare and a weak CME were formed after the F2 eruption. These observations evidenced that the interaction of two filaments and the opening of the large-scale overlying coronal loops caused by the F1 eruption are the most important reason that led to the F2 eruption. Our observations also support the standard solar flare model.  相似文献   
173.
The regional climate correlation within the Northern Hemisphere in the cold/dry mid-Younger Dryas event (YD) remains elusive. A key to unraveling this issue is sufficient knowledge of the detailed climate variability at the low latitudes. Here we present a high-resolution (3-yr) δ18O record of an annually laminated stalagmite from central China that reveals a detailed Asian monsoon (AM) history from 13.36 to 10.99 ka. The YD in this record is expressed as three phases, characterized by gradual onsets but rapid ends. During the mid-YD, the AM variability exhibited an increasing trend superimposed by three centennial oscillations, well-correlated to changes in Greenland temperatures. These warming/wetting fluctuations show a periodicity of ~ 200 yr, generally in agreement with centennial changes in cosmogenic nuclides indicated by the 10Be flux from the Greenland ice. This relationship implies that centennial-scale climate changes during the mid-YD are probably caused by solar output and rapidly transported over broad regions through atmosphere reorganization.  相似文献   
174.
陕西安康—石泉北部金矿成矿地质背景浅析   总被引:4,自引:0,他引:4  
安康—石泉北部金成矿带位于南秦岭早古生代裂谷盆地次级单元牛山—赤岩地垒,南北两侧分别以安康断裂和麻坪河断裂为界,典型金矿床有羊坪湾、黄龙、鹿鸣等.早古生代裂谷盆地以发育黑色岩系为特征,普遍沉积碎屑岩—碳酸盐岩夹火山岩,特别是浅变质志留系砂泥质岩和印支—燕山期脆韧性剪切带控制着金矿床的形成,前者提供金矿源层,后者促使含金热液运移富集成矿.该地区是金矿成矿带有利区段.  相似文献   
175.
地震预报中最难的是临震预报,而且最需要的也是临震预报。因此,寻找一种临震指标是非常重要的。大地微电流异常可能是一种能在地震前出现异常的观测方法,它具有地震前突变异常,而且是异常幅度明显的指标。通过大地微电流在云南,新疆,黑龙江和中国地震局地质研究所7个台站的实际观测结果可见,一般在地震前几天到20天左右出现异常,异常持续时间约2天。我们根据其异常规律,预测过5个地震的发生,特别是2007年6月3日云南省普洱6.4级和2008年7月7日黑龙江龙江县4.6级地震。  相似文献   
176.
The Taiping-Huangshan composite intrusion is a unique complex with characteristics changing from calc-alkaline (Taiping intrusion) to alkaline (Huangshan intrusion). Huangshan intrusion samples show a spectacular tetrad effect in their REE distribution patterns as well as non-CHARAC (charge-and-radius-controlled) trace element behavior, indicating a highly evolved late-stage magma component. This composite intrusion provides a rare opportunity to investigate the variance of tectonic setting and lithospheric thinning of the southeastern Yangtze Craton in late Mesozoic era. Zircon SHRIMP U-Pb analyses yield an emplacement age of 140.6±1.2 Ma for the Taiping intrusion, and ages of 127.7±1.3, 125.7±1.4, 125.1±1.5, and 125.2±5.5 Ma for four samples from the Huangshan intrusion respectively. The ages for four different phases of the Huangshan intrusion agree within their small analytical errors, indicating that the emplacement was in a short time. The Taiping and Huangshan intrusions are intimately associated, but there is about 15 Ma interval between their intrusion, and the magma characters change from calc-alkaline to alkaline without transition. This probably corresponds to lithospheric thinning of the southeastern Yangtze Craton. This event possibly happened from about 141 Ma (the emplacement age of the Taiping intrusion), to 128 Ma (start of emplacement of the Huangshan intrusion). The thinning mechanism is dominantly delamination.  相似文献   
177.
In this paper, I examine the role of cultural policy in a newly industrialised economy, which is at the same time a state with a short history and only nascent beginnings in nation-building and efforts to construct a distinctive cultural identity. Using Singapore as the site of analyses, develop an understanding of the intersection between the economic and socio-cultural agendas behind cultural development policies. I illustrate the hegemony of the economic, supported by the ideology and language of pragmatism and globalisation. At the same time, I explore the reception of and attempts to negotiate (and at times, contest) state policies by “cultural practitioners” – artists, dancers, playwrights, actors, directors and so forth, illustrating the disjuncture between state policies and practitioners' ideals. This may be cast as a conflict between social and cultural development priorities as envisaged by the practitioners as opposed to economic development priorities as embodied in the state’s cultural economic policies.  相似文献   
178.
通过对1998年4月19日发生在北海市银海区侨港、咸田、西塘等镇的一次飑线天气过境过程的大气环流特征风的垂直切变及物理量场、能量场的诊断分析,探讨这次强对流天气形成的原因。  相似文献   
179.
We report BeppoSAX and optical observations of the black hole candidate GX 339–4 during its X-ray 'off' state in 1999. The broad-band (0.8–50 keV) X-ray emission can be fitted by a single power law with spectral index, α ∼1.6. The observed luminosity is 6.6×1033 erg s−1 in the 0.5–10 keV band, which is at the higher end of the flux distribution of black hole soft X-ray transients in quiescence, comparable to that seen in GS 2023+338 and 4U 1630–47. An optical observation just before the BeppoSAX observation shows the source to be very faint at these wavelengths as well ( B =20.1, V =19.2). By comparing with previously reported 'off' and low states (LS), we conclude that the 'off' state is actually an extension of the LS, i.e. an LS at lower intensities. We propose that accretion models such as the advection-dominated accretion flows are able to explain the observed properties in such a state.  相似文献   
180.
钝段螺旋藻(Spirulina platensisGeitler)培养在低浓度NaHCO3(2~5g/dm^3)和适量生长素QS(0.5~5mg/dm^3)中,研究了生长素QS对钝顶螺旋藻生长、生物量和生化组成的影响,结果表明,在生长素QS为1mg/dm^3,NaHCO3浓度为5g/dm^3时,钝顶螺旋藻的生长最好,生物量、蛋白质及总碳水化合物的含量也与主浓度NaHCO3(8g/dm^3)培养条件下的基本相同,说明生物素QS的加入在一定程度上可降低NaHCO3的使用量,而不影响钝顶螺旋藻生长、生物量和生化组成。因而生长素QS在钝顶螺旋灌的养殖中可作为NaHCO3部分替代剂,从而达到降低养殖成本的目的。  相似文献   
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