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Guillemots Uria spp. account for ca. 70% of the total harvest of prey taken by seabirds breeding in the Barents Sea region. This paper presents guillemot chick diet data collected recently at four localities (Finnmark, Murman, Bjørnøya and Spitsbergen) and collates all the data found by the authors in the literature and in the archives of Tromsø Museum, the Norwegian Polar Institute and Kandalaksha State Nature Reserve. Guillemots consume a wide variety of prey and, in comparison to the harvest by predatory fish and marine mammals, their impact on the Barents Sea ecosystem is considered to be minimal. We point out the need for more systematic collection of data from different regions and at different times of the year before a final impact assessment can be made. 相似文献
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Summary. The Breggia gorge (Ticino, Switzerland) provides a continuous outcrop of Mesozoic limestones covering the time between the Lower Jurassic and Upper Cretaceous. The Jurassic section from the Lower Pliens-bachian to Aalenian is well dated by ammonites. The limestones of these stages are a good quality recorder of the polarity of the geomagnetic field during this time interval. More than 500 cores have been drilled along a 120 m thick section with a median distance between cores of about 20 cm. Detailed thermal and af demagnetization and further rock magnetic studies were used to determine the characteristic NRM direction for each sample. Initial NRM intensities and low field susceptibilities reflect variations in oxidation potential and sedimentation rate during carbonate deposition. The Breggia section covers an estimated 12Myr of Lower to Middle Jurassic time during which more than 60 distinct reversals of the geomagnetic field are recorded. This corresponds to a comparatively high mean reversal frequency of about 5 reversals Myr−1 . The Breggia polarity zonation can be correlated with the nearby section at Alpe Turati (Como, Italy) and comparable polarity patterns are recognized in other biostratigraphically well-dated magnetostratigraphic profiles from Hungary and Umbria (Italy). 相似文献
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Karen Culcasi 《Geographical review》2016,106(2):258-263
The goal of this forum is to garner attention to the issues surrounding the Boycott, Divestment, and Sanctions (BDS) campaign against Israel, to help a broad audience better understand the complexity of BDS, and to engage geographers in the BDS debate. Including the editorial introduction, seven different experts on the issues of Palestine/ Israel have written six essays on BDS for this forum. The six essays represent a wide range of opinions while also echoing some similar themes. 相似文献
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Virginie Mamadouh 《Urban geography》2018,39(9):1435-1439
This contribution to a Debate on “The Nation-State and the city” foregrounds the recently adopted Urban Agenda for the European Union. It discusses the new role of cities in the European policy making process and its relevance for relations between State and City in the light of EU membership. 相似文献
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Francis Leo Collins 《New Zealand geographer》2004,60(1):52-59
This paper discusses some of the ways that international students, particularly those from East Asia, are involved in the transformation of urban space in Auckland City. Using existing economic reports, local media accounts and the author's initial observations, the paper identifies how the embodied and linguistic practices of international students are involved in the changing landscapes of Auckland's inner city. This cursory reading serves to identify a research agenda and to reflect upon some key theoretical textxs. The insights of Arjun Appadurai, Michael Peter Smith and Ulrich Beck are used to suggest that the changes in Auckland, whilst certainly local, are also influenced fry factors that emerge from beyond the borders of international students' origin communities, cities and nations. 相似文献
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在温和的水热条件下分别制备出纯净的磷酸锆钠 [NaZr2 (PO4) 3 ]、磷酸锆钾 [KZr2 (PO4) 3 ]和磷酸锆铷 [RbZr2 (PO4) 3 ]。研究了原料配比、矿化剂 (氟离子 )、反应时间和温度等水热晶化条件对产物生成的影响。发现在较宽的温和水热条件下可以制得这三种磷酸锆盐 ;随着碱金属离子的增大 ,产物的生成条件越来越窄 ;最佳制备条件是 :F- ZrO2 =2、P2 O5 ZrO2 =3 (均为摩尔比 )、[ZrOCl2 ]=0 6mol L、反应温度 1 5 0℃、反应时间 2天。用水热法没有制备出同一系列磷酸锆盐中的磷酸锆锂 [LiZr2 (PO4) 3 ]和磷酸锆铯 [CsZr2 (PO4) 3 ]。采用XRD、SEM、IR、Raman和XPS等现代物化仪器对产物的结构与物相纯度进行了测定与表征 相似文献
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采用静态试验法研究了水溶性富勒烯对U(VI)在氧化多壁碳纳米管上吸附的影响。结果表明,羟基化富勒烯(C60(OH)n)和羧基化富勒烯(C60(C(COOH)2)n)的加入对U(VI)在氧化多壁碳纳米管上的吸附量影响作用类似。在pH<3范围内,羟基化富勒烯和羧基化富勒烯对吸附几乎没有影响,在pH>3以后,二者开始抑制碳纳米管对U(VI)的吸附。较低浓度(10 mg/L)的C60(OH)n对U(VI)的吸附几乎没有影响。而等量的C60(C(COOH)2)n已呈现出明显的抑制作用。但两者的作用机理不同,前者可能是由于羟基化富勒烯和U(VI)竞争氧化多壁碳纳米管上的吸附位点造成的,后者则可能改变了氧化多壁碳纳米管的表面电荷。用双位点模型对不同固液比和U(VI)初始浓度下U(VI)的吸附率随C60(OH)n和C60(C(COOH)2)n初始浓度的变化进行了拟合得到了很好的结果。 相似文献
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L. Migliore G. Brambilla A. Grassitellis G. Dojmi di Delupis 《International Journal of Salt Lake Research》1993,2(2):141-152
To evaluate the effects of sulphonamide pollution in marine and brackish systems, and to assess the utility of a recently
proposed test protocol, sulphadimethoxine toxicity was measured using naupli and cysts of anArtemia species. Nauplii mortality, evaluated between 24 and 96 h, indicated a relatively high toxicity of sulphadimethoxine toArtemia (96 h LC50= 19.5 mg L−1). In addition, test on cysts demonstrated that a nominal concentration of 300 mg L−1 sulphadimethoxine significantly depressed hatching. Toxicity could depend on the high bioaccumulation rate of sulphadimethoxine
measured in the organisms. The role of these tests in assessing the environmental risks of intensive farming and in determining
suitable standards to improve water quality criteria is discussed together with the possible utilization of bioaccumulatingArtemia as ‘medicated feed’. 相似文献
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Mark L. Mallory Kerry Woo Anthony J. Gaston W. Eric Davies Pierre Mineau 《Polar research》2004,23(1):111-114
Although the diet of walrus ( Odobenus rosmarus ) is considered varied, records of walrus consuming marine birds are rare in the published literature. In 2001 and 2002 we observed walrus foraging on adult thick-billed murres ( Uria lomvia ) at Coats Island in Nunavut, Canada. Approximately 46% of the attacks on murres were successful, and as many as 67 murres may have been killed in one day in August 2002. All soft parts of the murres were sucked out, with carcasses of only bones, feathers and skin left floating on the water. The extent to which predation on seabirds by walrus occurs across the eastern Arctic is unknown, but it could represent an important source of mortality for murres at some breeding colonies. 相似文献
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Torkild Bakken Jon Anders Kongsrud Eivind Oug Sabine K.J. Cochrane Toril Loennechen Moen & Beata E.B. Solbakken 《Polar research》2010,29(1):1-21
A thorough literature review has been undertaken to establish the first complete account of polychaetes recorded from the area around the volcanic island of Jan Mayen. The annotated checklist lists 121 species-level taxa, representing an increase from the 75 species previously recorded. The checklist is based on existing records, supplemented with material sampled in 1999, from which 42 species new to the area were reported. Some previously reported species from the area have been excluded because of inadequate documentation. The polychaete fauna of Jan Mayen is comparable with that of the mainland Norwegian coast and the Svalbard area. No taxa unique to the island were found. However, knowledge of the marine invertebrate fauna in general at Jan Mayen is sparse because few surveys have been undertaken there. It is expected that future expeditions will reveal further new taxon records for the area. 相似文献
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Yu V. Naumenko 《International Journal of Salt Lake Research》1999,8(2):171-176
The algal flora of Lake Bai-Khol, located in the endorheic Uvs-Nuur Basin, Russia, has been studied from collections made
in August 1997. 79 taxa belonging to diatoms, blue-green and green algae were present. 相似文献
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Tom Delph-Janiurek 《Area》2002,33(4):414-421
This article addresses the conversational (re)production of research relations, focusing on gender and sexuality in relation to responses, laughter and consensus in interviews. It discusses links to access as an on-going issue, and to wider issues connected to the production of knowledge. 相似文献
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M. J. Abdollahi M. H. Karimpour A. Kheradmand A. R. Zarasvandi 《Natural Resources Research》2009,18(2):137-151
The Muteh gold district with nine gold deposits is located in the Sanandaj-Sirjan metamorphic zone. Gold mineralization occurs
in a pre-Permian complex which mainly consists of green schists, meta-volcanics, and gneiss rocks. Shear zones are the host
of gold mineralization. Gold paragenesis minerals include pyrite, chalcopyrite, pyrrhotite, and secondary minerals. Pyrites
occur as pre-, syn-, and post-metamorphism minerals. To determine the source of the ore-bearing fluids, fifty samples were
selected for petrographical and stable isotope studies. The mean values of 12.4‰, and −42‰ for δ18O and δD isotopes, respectively, and a mean value of 7.75‰ of calculated fractionation factors for δ18O H2O, from quartz veins indicate that metamorphic host rocks are the most important source for the fluids and gold mineralization.
Three generations of pyrite can be distinguished showing a wide range of δ34S. Gold mineralization is closely associated with intense hydrothermal alteration along the ductile shear zones. The characteristics
of the gold mineralization in the study area are similar to those of orogenic gold deposits elsewhere.
An erratum to this article can be found at 相似文献
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本文测定了三元系ＲＥＣｌ３（ＲＥ＝Ｌａ，Ｐｒ，Ｓｍ）－ＨＯＡｃ－Ｈ２Ｏ（３０℃）的平衡态的溶度数据并绘制了相应的溶度图．在三个体系中分别形成ＬａＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ三种物质．ＨＯＡｃ对ＬｓＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ盐析作用程度的不同，表明了轻稀土元素的“一分组效应”，同时依据ＨＯＡｃ对ＬａＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ有盐折作用这一结论，提出了一种制备ＬａＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ的新方法． 相似文献