Urban locations and Black Metropolis resilience in the Great Depression     

《Geoforum》2017

Motivated by theoretical arguments about ethnicity and economics and by historical research on urban black communities in the United States, this paper investigates the resilience of the early twentieth-century Black Metropolis. The study tests hypotheses about changes during the Great Depression (1930–1940) in the advantages of various cities as locations of black communities’ ethnic economies, analyzing Census data on blacks’ representation in occupations reflecting the Black Metropolis’s professional, entrepreneurial, and cultural media pursuits. There is mixed support for the hypothesis that the nationally dominant urban centers of New York, Chicago, and Philadelphia had the most resilient Black Metropolises, a finding that casts doubt on claims that black communities in such key places enjoyed exceptionally favorable locational advantages. Yet, the results support the hypothesis that northern cities were, overall, more resilient locations than southern cities, particularly for black professionals and entrepreneurs, affirming the argument that the urban North’s Black Metropolises were vital economic opportunity centers for these black communities’ upper- and middle-classes.  相似文献   

汕尾电厂临时倾倒区对所在海域及其周边环境的影响     

李壮伟 《广东海洋大学学报》2010,30(6)

分析汕尾电厂临时倾倒区2006年倾倒的疏浚泥对所在海域水质、沉积物、生物群落及生物质量等的影响。结果表明,在倾倒过程中,海水中悬浮物、石油类的含量增加,属第三类海水水质;倾倒活动改变了生物群落的水环境,使群落种数减少,多样性、均匀度和丰度降低。倾倒活动结束1个月后,除海水中悬浮物的含量仍属第三类海水水质外,其他污染物含量均符合第二类海水水质标准,底栖生物恢复较缓慢。疏浚泥倾倒对海区沉积物质量和海洋生物质量的影响较小。  相似文献   

Electoral behaviour behind the gates: partisanship and political participation among Canadian gated community residents     

R. Alan Walks 《Area》2010,42(1):7-24

Gated communities have been characterised as representing processes of 'forting up' and 'civic secession', in which their residents use gating as a strategy for withdrawing from political life and from taking collective responsibility for others. The assumption is that the residents of private gated communities should be less likely to participate in political life, and/or be more likely to support political parties on the right who advocate privatisation, reduced government expenditures and lower taxes. If the act of living in a gated community is associated with either greater support for parties and policies on the right of the political spectrum, or limited political participation, then the growth of such forms of privatised communities has potential implications for the future of urban politics and even for national political systems. However, despite surveys that have dealt with social attitudes 'behind the gates', insufficient attention has been paid to the politics of gated community residents. This paper fills this gap through a comparative analysis of electoral behaviour during the 2006 federal election at the level of the polling station. Electoral participation and partisanship in 27 gated communities in three Canadian metropolitan areas is compared against that of non-gated residents. Regression analysis is conducted in order to determine whether gated community residents differ from their non-gated counterparts in the way they vote and their levels of electoral turnout, after controlling for social composition. The potential implications of this research are then discussed.  相似文献   

Unemployment and economic activities in the EC     

Bue Nielsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):62-69

Nielsen, Bue: Employment and economic activities in the EC. Geografisk Tidsskrift 84: 62–69. Copenhagen January 1984.

Regional disparities in unemployment and economic activities in the EC in the late 1970'es. Various concepts of unemployment are discussed. The performance of regions and countries using different concepts are illustrated.  相似文献   

The Influence of the “Mixed Pixel” Problem on the Detection of Analogous Forest Communities Between Presettlement and Present in Western New York∗     

Barry J. Kronenfeld  Yi-Chen Wang  Chris P. S. Larsen 《The Professional geographer》2013,65(2):182-196

We conducted a land change analysis to determine if the forest communities of presettlement and present contain areas that are analogous in composition, using surveys of the Holland Land Company (1797–1799) and U.S. Forest Service (1991–1993) from western New York. Gridded forest-type maps are produced from each survey using two models: a uniform model that assumes each data grid cell is occupied by a single forest type, and a mixture model in which grid cells are assumed to be occupied by multiple forest types in different proportions. The mixture model consistently detects a larger area of analogous communities in the two time periods at both global and local scales.  相似文献   

Characterizing the international carbon capture and storage community     

Jennie C. Stephens  Anders Hansson  Yue Liu 《Global Environmental Change》2011,21(2):379-390

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Proximate environmental drivers of coral communities at Palmyra Atoll: establishing baselines prior to removing a WWII military causeway     

Williams GJ  Knapp IS  Maragos JE  Davy SK 《Marine pollution bulletin》2011,62(8):1842-1851

A management proposal aims to partly remove a WWII military causeway at Palmyra Atoll to improve lagoon water circulation and alleviate sedimentation stress on the southeast backreef, an area of high coral cover and diversity. This action could result in a shift in sedimentation across reef sites. To provide management advice, we quantified the proximate environmental factors driving scleractinian coral cover and community patterns at Palmyra. The proportion of fine sedimentation was the optimal predictor of coral cover and changes in community structure, explaining 23.7% and 24.7% of the variation between sites, respectively. Scleractinian coral cover was negatively correlated with increases in fine sedimentation. Removing the causeway could negatively affect the Montipora corals that dominate the western reef terrace, as this genus was negatively correlated with levels of fine sedimentation. The tolerance limits of corals, and sediment re-distribution patterns, should be determined prior to complete removal of the causeway.  相似文献   

The effects of season and wrack subsidy on the community functioning of exposed sandy beaches     

Sílvia C. Gonçalves  João C. Marques 《Estuarine, Coastal and Shelf Science》2011

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珠江三角洲晚第四纪红树林的演化及其环境意义     

翁毅  张伟强 《台湾海峡》2011,30(2):264-268

广州番禺东涌剖面样品的AMS（磁谱仪）年龄及红树林孢粉分析结果表明,珠江三角洲存在晚更新世和全新世的红树林,红树林是海侵的标志之一.按照检出红树属花粉的9个剖面的分布以及5处埋藏红树林腐木的分布,可以描绘出全新世海侵的边界.根据东涌剖面的沉积旋回、样品年龄、红树林花粉含量曲线、半咸水-淡水硅藻及热性-温性硅藻含量曲线的综合分析,可将沉积环境的变迁分为4个阶段.第一阶段和第三阶段的海侵有利于红树林的发展,第二阶段不利于红树林的发展,第四阶段的晚全新世,红树林的生长频繁,显示人为因素的影响.  相似文献   

Photosynthetic efficiency, cell volume, and elemental stoichiometric ratios in Thalassirosira weissflogii under phosphorus limitation     

��ʤ  ��־��  ����  ����  ��ɭ�� 《中国海洋湖沼学报》2011,29(5):1048-1056

Nutrient limitation is known to inhibit growth and metabolism and to alter elemental stoichiometric ratios in phytoplankton. In this study, physiological changes in Thalassirosira weissflogii were measured under different dissolved inorganic phosphate (DIP) regimes in semi-continuous cultures to revisit the utility of the Redfield ratio for assessing nutrient limitation. The results showed that cell size increased with decreasing DIP availability. In the P-depleted treatment (f/2-P) the cell size was 1.48 times larger than that in the P-limited (f/100) treatment and 2.67 times larger than that in the P-saturated treatment (f/2 and f/10). The fucoxanthin to chlorophyll a ratio (Fuco/chl a) was relatively stable (about 0.3) in P-saturated cultures and was 10 times higher than that in P-limited and P-depleted cultures. During the experimental period, the photosynthetic efficiency index, ?F/Fm′, was relatively stable at ~0.50 in the P-saturated cultures, but quickly declined with decreasing DIP availability. Although cellular P content showed a significant difference between the P-saturated culture (1.6 pg/cell) and the P-limited culture (0.7 pg/cell), the N/P ratio in T. weissflogii did not show a trend with DIP availability and fluctuated slightly around 25. Our results suggest that cell division in T. weissflogii is not strictly size-gated but is probably regulated by a biochemical, and hence, an elemental stoichiometric ratio threshold, and that deviation of the cellular N/P ratio from the Redfield ratio is not a reliable indicator of algal nutrient stress.  相似文献