长三角城市群“空间流”网络结构特征——基于公路运输、火车客运及百度指数的综合分析

信息技术的应用与社会信息技术的传输,使大量的要素(人流、物流、信息流)在城市群空间内集聚与扩散,加密城市群空间内城市联系。在基于公路运输、普通列车、高速列车以及百度指数4个要素的综合分析基础上,对长三角城市群"空间流"网络结构特征进行探析。研究结果表明:(1)长三角城市群区域内城市联系虽具备了网络化规模,但城市间的联系不均衡,以上海、南京、杭州等城市为多中心的协调网络发展格局特征明显;(2)长三角城市群16个核心城市"空间流"特征呈现三角形网络结构,其三角形的顶角分别由上海(沪)、南京(宁)与杭州(杭)3个核心节点城市构成。在空间结构内部,形成若干次级城市网络连线;在空间分布上,北翼网络化程度较高于南翼线性联系程度,区域联系强度以"沪—宁"、"沪—杭"沿线向两侧递减;(3)上海、南京、杭州、苏州、无锡5个核心城市排名处于网络中心的前列,扬州、南通、泰州、舟山等周边城市相对靠后,这与区域经济发展过程的"吸虹效应"有关,随着区域经济一体化程度的加深,中心城市会向周边地区提供服务与经济辐射,完善整个长三角城市群网络体系。     

全球升温1.5℃与2.0℃情景下长江中下游地区极端降水的变化特征

基于长江中下游地区1961~2100年区域气候模式COSMO-CLM(CCLM)模拟与1961~2005年气象站观测的逐日降水数据,通过统计计算年降水量、强降水量、暴雨日数和极端降水贡献率4个极端降水指数,研究全球升温1.5℃与2.0℃情景下,长江中下游地区极端降水的时空变化特征。结果表明:(1)全球升温1.5℃情景下,年降水量相对于1986~2005年减少5%,强降水量、暴雨日数和极端降水贡献率分别增加7%、33%和4%;概率密度曲线表明,年降水量均值下降,强降水量、暴雨日数和极端降水贡献率均值上升,极端降水方差增大;年降水量、强降水量和暴雨日数在空间上表现为南部增加北部减少,极端降水贡献率则相反。(2)全球升温2.0℃情景下,年降水量下降3%,强降水量、暴雨日数和极端降水贡献率分别上升15%、46%和15%;年降水量均值稍有减少且方差稍有上升,强降水量、暴雨日数和极端降水贡献率均值和方差明显增加;年降水量减少区域位于长江主干以北,强降水量、暴雨日数和极端降水贡献率表现为绝大部分地区增加的空间变化特征。(3)全球升温由1.5℃至2.0℃时,年降水量、强降水量、暴雨日数和极端降水贡献率分别增加3%、7%、10%和11%;随升温幅度的增加极端降水均值和方差上升;极端降水呈增加态势的范围扩大。因此,努力将升温控制在1.5℃对降低极端降水的影响具有重要意义。     

Reinventing the bicycle: how calculative practices shape urban environmental governance

The concept of sustainability transitions has become increasingly prominent in academic and policy discourses during recent decades, but the importance of the link between knowledge-producing epistemic practices and urban governance has been underappreciated in this discourse. Based on a case study of cycling in Copenhagen between 1900 and 2015, and drawing upon a governmentality-inspired analytical framework, this research demonstrates that transformative governance may be initiated by epistemic practices that render urban systems visible in other ways. Urban cycling has been reconstructed over time in Copenhagen as a traffic safety ‘problem’, a component of the experiential and liveable city, and a health-producing (and hence economically valuable) regional transport mode. The research findings emphasise that epistemic practices can provide a powerful stimulus for creating changes in urban governance. The results also provide support for initiatives to broaden the terms of academic debate on sustainability transitions.     

Taming the Climate? Corpus analysis of politicians’ speech on climate change

The politics of climate change is much discussed, but there has been little investigation into how politicians themselves understand or articulate the issue. Corpus analysis, a method developed within linguistics, is used to investigate how UK politicians talk about climate change, using the example of the 2008 Climate Change Bill. Corpus techniques, including keyword analysis, collocation and semantic tagging, are used, alongside critical reading of the text. The analysis shows that politicians frame climate change as an economic and technical issue, and neglect discussion of the human and social dimensions. They are selective in their use of scientific evidence, with little mention of abrupt or irreversible change. In doing so, they attempt to ‘tame’ climate change, rather than confronting difficult realities. While this strategy has the benefit of political acceptability, it does not allow for discussion of the full political and social implications of climate change, and precludes more radical responses.     

When is increasing consumption of common property optimal? Sorting,congestion and entry in the commons

First-best pricing or assignment of property rights for rival and non-excludable goods is often infeasible. In a setting where the social planner cannot limit total use, we show that common-property resources can be over or under-consumed. This depends on whether the external benefits of reallocating users to less congested resources outweigh the additional costs imposed by new entrants. Importantly, we show that it may be optimal to encourage consumption of some common property resources. Our results have important implications for settings ranging from fisheries and forestry to recreational demand and transportation.     

Effect of the allelochemicals from the macrophyte Egeria densa on the competitive interactions of pelagic and littoral cladocerans

Macrophytes release allelochemicals, which affect pelagic cladocerans such as Daphnia. Using population growth experiments, we analysed the effects of allelochemicals from the macrophyte Egeria densa on the interaction between Daphnia mendotae and three littoral cladocerans (Diaphanosoma birgei, Macrothrix triserialis and Simocephalus mixtus). We found that allelochemicals from E. densa increased the abundance of all the tested cladocerans in spite of the presence of a competitor. This effect was stronger (nearly three to four times higher than in controls) for D. birgei and M. triserialis in the absence of D. mendotae. Independent of the presence of allelochemicals, S. mixtus, but not D. birgei and M. triserialis, reduced the abundance of D. mendotae as compared to controls. The rate of population increase (r) per day was significantly elevated due to the presence of Egeria’s allelochemicals (from 0.07–0.16?d^?1 without allelochemicals against 0.12–0.24?d^?1 with allelochemicals). In our competition experiments, the rates of population increase of the cladocerans were lower than those in single-species cultures when cultured in the absence of allelochemicals. However, in the presence of allelochemicals this trend was not consistent. Thus, the positive effects of Egeria’s allelochemicals over the cladoceran populations may enhance the grazing pressure on phytoplankton.     

Low uptakes of Cd,Cu, and Zn in Dugesia japonica,a freshwater planarian with higher tolerance to metals

Although a freshwater planarian is proposed as a potential model for studying toxicities of environmental pollutants, they are less sensitive to metal exposures, compared to other freshwater invertebrates. We hypothesised that the metal uptake is low in treated planarians, which may lead to their higher tolerance to metals. The acute toxicities of Cu and Zn to Dugesia japonica were determined. The 24- and 48-h median lethal concentrations were 4.50 and 3.46?mg?L^?1, respectively, for Cu, and 41.97 and 37.79?mg?L^?1, respectively, for Zn. Accordingly, combining with the data on Cd in our previous study, higher tolerance of planarians to metals was revealed. Also, tissue levels of Cd, Cu, and Zn in treated D. japonica were determined, and their dissolved uptake rate constants (k₁) were calculated. Results showed that bioaccumulations of these metals in D. japonica were, indeed, lower than that in other freshwater invertebrates having higher susceptibilities to these metals.     

Evidence of new particle formation during post monsoon season over a high-altitude site of the Western Ghats,India

The formation of ultrafine particles, their growth, and associated characteristic features has been studied during new particle formation events over a high-altitude station of the Western Ghats during the 2014 post-monsoon season. Most of the events were observed during noon time where particle bursts in the nucleation-mode size range from 5 to 25 nm followed by sustained growth in size. This phenomenon persists for ～4–8 h with a growth rate of 1–2 nm h^–1. Peak concentrations of nucleation-mode particles during the event generally vary from 2300 to 5000 cm^–3. The mean growth rate is 1.4 ± 0.42 nm h^–1, particle formation rate is 1.14 ± 0.22 cm^–3 s^–1, coagulation sink is 0.35 ± 0.22 cm^–3 s^–1, and condensational sink is 15.4 ± 2.6?×?10^–3 s^–1. All these values are comparable with earlier results from Indian region. Comparison of size-segregated particle number concentration during days of new particle formation events and those without new particle formation were carried out showing a distinct variation in nucleation and Aitken mode with least variability associated with the accumulation mode.     

Differential blood counting in fish as a non-destructive biomarker of water contamination exposure

Differential white blood cell counting was performed on blood from the fish species Oreochromis niloticus and was used as an in situ indicator of the species’ exposure to contamination. Ten young fish were collected in an area influenced by the discharge of effluents and from a fish farm (control group). The fish were anesthetized and caudal puncture was used to collect the blood. Differential white blood cell counting was performed, as well as the counting of total leukocytes and thrombocytes (in 2000 cells). Physicochemical parameters of the water from both sites were analyzed. The water from the polluted area was found to have high conductivity and low levels of dissolved oxygen, factors that indicate poor environmental quality. Fish collected from the polluted site presented higher percentages of eosinophils and monocytes and fewer thrombocytes because of exposure to pollution and hypoxic conditions. The differential white blood cell count represents a suitable biomarker of environmental health and provides a tool for biomonitoring water quality.     

Growth in urban extent and allometric analysis of West African cities

Urban area expansion is happening at much faster rates in Asian and African cities than elsewhere in the world. This study uses multi-temporal Landsat images to map the urban extent of six small to large cities in West Africa at four different time steps from the early 1970s–2010. The selected cities are Kumasi of Ghana, Daloa of Cote d’Ivoire, Abuja and Kano in Nigeria, Kindia of Guinea, and Ouagadougou of Burkina Faso. All cities revealed significant urban growth in both urban area and population; however, it was apparent that there was a lot of variability in urban area development. Exponential urban growth rates in the cities were measured as ranging between 0.026 and 0.077, with allometric scaling factors matching those of other countries.