A tale of many cities: universal patterns in human urban mobility

The advent of geographic online social networks such as Foursquare, where users voluntarily signal their current location, opens the door to powerful studies on human movement. In particular the fine granularity of the location data, with GPS accuracy down to 10 meters, and the worldwide scale of Foursquare adoption are unprecedented. In this paper we study urban mobility patterns of people in several metropolitan cities around the globe by analyzing a large set of Foursquare users. Surprisingly, while there are variations in human movement in different cities, our analysis shows that those are predominantly due to different distributions of places across different urban environments. Moreover, a universal law for human mobility is identified, which isolates as a key component the rank-distance, factoring in the number of places between origin and destination, rather than pure physical distance, as considered in some previous works. Building on our findings, we also show how a rank-based movement model accurately captures real human movements in different cities.     

我国城市人与自然耦合系统的协调度

城市作为人类生存与发展的主要空间载体,是人与自然耦合系统的典型代表。城市人与自然协调度是认识人与自然耦合机制重要内容,对揭示城市人类活动对生态环境的影响,指导城市建设具有重要意义。从水资源开发强度、土地开发强度、水资源供给能力、环境污染物排放强度与碳排放强度五个方面分析城市人与自然协调度特征,评估城市建设与发展对自然环境的影响程度,并评估了我国146个城市的协调度特征,进一步分析了城市人口规模、城市经济规模、城市社会发展水平、不同生态地理区人与自然耦合协调度的关系。结果表明：2016年城市平均协调度指数为87.90,不同城市的协调度差距很大且协调度与城市人口规模、经济规模、发展水平呈显著负相关,而六大生态地理区中,西南地区协调度最高,协调度指数为92.81,西北地区协调度最低,协调度指数为82.25。研究发现我国城市建设与发展对自然环境影响仍然较大,并表现为（1）我国城市发展总体仍处于高需求高排放的发展阶段;（2）生态环境承载力是影响城市人与自然耦合协调度的重要因素;（3）提高能源利用效率,降低碳排放强度在改善城市人与自然协调度中发挥作用。最后,从优化城市布局、提高水、能源利用效率、控制环境污染等方面提出政策建议,为评估城市生态文明建设与可持续发展提供参考与依据。     

“交通廊道蔓延”视角下山地城市典型样带空间格局梯度分析

空间可达性的强弱在一定程度上决定着土地利用变化的方向和强度,因此交通的廊道作用对城市化进程发挥着重要作用。以重庆市轨道交通三号线沿线双侧各3000 m缓冲样带为研究区,采用面向对象分类方法将四期Landsat TM/ETM遥感影像进行土地利用制图,选择核密度估算、指数分析和梯度分析的空间分析方法,研究交通廊道的变化及其对区域空间格局变化的影响。研究表明,研究期内,样带空间的组分和格局发生了较为明显的变化。道路的空间变化和区域空间格局的变化表现出较为明显的梯度性:道路密度、土地利用的变化强度随距离交通主干道距离的远近依次减弱,道路密度等级范围内的土地利用变化强度随等级的降低出现由弱到强再转弱的特征。     

深圳市景观生态安全格局源地综合识别

城市生态安全格局是景观生态学研究的热点和重点之一,识别源地是构建生态安全格局的首要环节.在总结已有研究中重要斑块识别方法的基础上,提出了结合景观连通性分析、生物多样性服务评估和生境质量评估来提取重要斑块的方法.以深圳市为研究区,采用基于图论的景观连通性指数、生物多样性服务当量、InVEST模型生境质量评估模块和GIS技术相结合的方法识别生态用地重要斑块.结果表明:深圳市生态斑块依照连通性、生物多样性和生境质量的综合评估分为五级,其中最重要斑块主要分布在龙岗区、盐田区和罗湖区;现行基本生态控制线政策可以保护大部分重要斑块.     

西安市典型区域城市生态单元空间格局研究

综合利用遥感(RS)与地理信息系统(GIS)技术手段,选取西安市南郊城乡结合部为研究区,采用室内遥感影像判读、野外考察验证与室内机助制图相结合的方式,根据城市生态单元分类体系,在GIS的支持下建立了研究区城市生态单元数据库,并在此基础上,通过计算研究区城市生态单元的平均面积、形状指数、分形分维数、稳定性指数、MoranI指数这五项指数,对城市生态单元空间格局进行定量化研究.结果表明,城市生态单元主类斑块数量和斑块总面积基本保持正比例关系,形状指数和分形分维数之间、稳定性指数和MoranI指数之间均存在着正相关关系.     

基于土地利用分析的兰州市城市区域生态安全格局研究

中尺度区域生态安全的研究针对区域的实际生态安全问题展开,处于各尺度生态安全概念的核心地位.作为特殊的区域,以生态基础设施建设为核心的城市区域生态安全格局的构建成为城市可持续发展的基础内容.基于土地利用分析的定性、定量相结合的景观格局研究,生态价值评估以及社会经济驱动分析为城市区域生态安全格局的构建提供了一种可能.兰州市区域生态安全格局由生态保障体系、生态缓冲体系以及生态过滤体系所构成,经过分析,认为生态缓冲体系的建设成为兰州市区域生态安全格局构建的关键.城市未来扩展格局的定量分析成为兰州市区域生态安全格局安全级别的判别函数,根据不同的响应,把区域生态安全格局化分为低级、中级和高级3个级别.     

基于生态安全格局与多尺度景观连通性的城市生态源地识别

高度城市化区域面临着严峻的生态环境问题,生态安全格局构建是保障城市生态安全的重要途径。生态源地的科学识别一直是生态安全格局构建的技术难点。以高度城市化的深圳市为例,从社会-经济-自然三方面要素构建DPSIR模型评估区域生态安全,并基于景观连通性的多尺度分析识别生态源地。研究表明:(1)深圳市生态安全格局呈现东南部、东北部优良,中部、西部区域警告的空间特征,其中安全区、较安全区、基本安全区、预警、中警分别占比30.34%、13.49%、9.85%、9.15%和37.17%;(2)通过连接度、聚合度、内聚力和分离度4个景观连通性测度指标的主成分分析,可知400 m是深圳市生态源地景观连通性最优的识别尺度,斑块最小识别阈值面积为0.8 km~2;(3)深圳市生态源地面积为753.78 km~2,占全市总面积的37.74%,主要为深圳市东南部与西部区域的林地和水域用地,其中包含了86.87%的法定保护区,且91.92%的区域落入生态控制线范围内;(4)基于生态安全格局与多尺度景观连通性的生态源地识别方法可为城市生态源地的识别提供新思路,从而有效指导城市规划。     

Serum boron concentration from inhabitants of an urban area in Japan

Boron (B) levels were determined in the serum of 980 healthy inhabitants living in an urban area of Japan by means of inductively coupled plasma emission spectrometry (ICPES). The results showed a log-normal distribution of serum B for both sexes, although there are age-related differences. In male subjects, serum B increases rapidly up to 49 yr of age, reaching a plateau between ages 50 and 69 yr old, followed by a gradual increase up to 70 yr or older. Female subjects exhibit a gradual increase up to the age of 70 yr old. The reference value for male and female subjects was 79.8 μg/L and 67.9 μg/L, and the reference interval was 33.3–191.2 μg/L and 29.5–154.9 μg/L, respectively. The obtained reference value and interval of the nonexposed group may be useful for health screening for B exposure, either for people living in regions with high levels of B in the environment, or for workers who are exposed to this element.     

南昌市中心城区绿地景观对PM2.5的影响

随着我国城市化工业化的快速发展,大气环境质量问题越来越受到重视,PM_2.5作为重要的大气污染物,已经引起了公众的普遍关注.城市绿地作为一种半自然的地表景观能在一定程度上影响PM_2.5的浓度与分布,目前的研究主要集中在微观尺度上,在景观尺度上的研究还不多见.本研究采用土地利用回归模型进行监测点加密,基于普通克里格插值法实现PM_2.5浓度的空间分布高精度模拟.然后与通过遥感解译的城市绿地进行耦合,定量分析了城市绿地景观特征、质量等对PM_2.5浓度的影响.结果表明:研究区PM_2.5浓度由市中心向周边不断递减;绿地类型对PM_2.5浓度影响显著;绿地斑块形状对PM_2.5浓度没有显著影响;绿地斑块的面积、质量与PM_2.5浓度呈显著负相关.研究区绿地景观对PM_2.5消减作用距离小于100 m.在消减作用距离内,距离绿地斑块越近,PM_2.5浓度越低.其中,附属绿地和公园绿地对PM_2.5浓度的消减作用距离大于其他绿地类型.     

Breast-feeding pattern in an urban Nigerian community

This paper examines the pattern of breastfeeding among women still in their prime childbearing ages (15-35 years) in Ilorin, the capital city of Kwara state in Nigeria. While breastfeeding is still a common practice among urban women, there is wide variation in the duration of breastfeeding depending on the socioeconomic characteristics of the mothers. Mother's education and father's education have very strong negative associations with duration of breastfeeding. Use of contraception also has a significant independent but negative effect on breastfeeding duration. Christians continue breastfeeding for shorter periods than Muslims. The introduction of supplementary feedings to the infant occurs in this population much earlier than is recommended by various authorities. Decline in breastfeeding practice may have deleterious effects on the health and survival of children in developing countries and may also lead to higher fertility and more rapid population growth. The high morbidity and mortality among artificially fed infants in many developing countries can be attributed to improper preparation as well as contamination of infant formula and other foods.     

城市森林景观格局与过程研究进展

大规模的城市化进程,改变了城市以及周边区域的景观格局,显著影响着城市森林生态系统的结构、过程与功能.景观尺度上的城市森林景观格局与生态过程研究已经成为当前城市森林学的研究热点.在阐明城市森林及其景观格局与过程概念的基础上,综述了国内外城市森林景观格局与过程的研究内容、研究方法的进展情况,指出了以下几个方面有望成为今后城市森林景观研究的发展方向:景观尺度上的城市森林系统能流、物质循环等生态学过程研究;城市森林景观格局演变的社会驱动力研究;基于生态服务功能的城市森林规划研究;半都市化地区的森林景观格局与过程研究;基于空间显式景观模型的城市森林景观格局与过程模块开发.     

Isolation of Bartonella henselae from domestic cats in an Italian urban area

Bartonella henselae is the causative agent of Cat Scratch Disease (CSD) in humans. Cat is considered the reservoir of the bacterium. Identification of bacteriemic cats is the basic tool in the prophylaxis of CSD. Blood samples were collected between January 1999-December 2000 from 248 domestic cats living in an urban area (Reggio Emilia) in Northern Italy and tested for Bartonella henselae bacteriemia. Cultural and PCR methods were used. PCR was used directly on cat blood as well as to identify the Bartonella strain growth in culture. 24 (9.7 %) cats were found bacteriemic, most of which aged <1 year. A higher sensitivity was demonstrated by cultural method compared with PCR.     

Collective motion of cells mediates segregation and pattern formation in co-cultures

Pattern formation by segregation of cell types is an important process during embryonic development. We show that an experimentally yet unexplored mechanism based on collective motility of segregating cells enhances the effects of known pattern formation mechanisms such as differential adhesion, mechanochemical interactions or cell migration directed by morphogens. To study in vitro cell segregation we use time-lapse videomicroscopy and quantitative analysis of the main features of the motion of individual cells or groups. Our observations have been extensive, typically involving the investigation of the development of patterns containing up to 200,000 cells. By either comparing keratocyte types with different collective motility characteristics or increasing cells' directional persistence by the inhibition of Rac1 GTP-ase we demonstrate that enhanced collective cell motility results in faster cell segregation leading to the formation of more extensive patterns. The growth of the characteristic scale of patterns generally follows an algebraic scaling law with exponent values up to 0.74 in the presence of collective motion, compared to significantly smaller exponents in case of diffusive motion.     

Collective exploration and area marking in the ant Lasius niger

Summary: The aphid tending ant species, Lasius niger collectively explore new areas. Scouts are mobilised within the first five minutes of exploration with activity thereafter decreasing and stabilising after 40 minutes. Collective path choices of colonies underline the existence of chemical recruitment and area marking during exploration. To identify the territorial or home-range role of exploratory marking, we examined its influence on agonistic behaviour during intraspecific encounters. Ten nestmates and ten alien conspecifics were confronted: (i) on a paper marked by their own colony, (ii) on a paper marked by the alien colony or (iii) on a paper not chemically marked by ants. Residents and intruders showed a weak level of aggression and behaved similarly whatever the type of area marking. As no colony-specificity was observed in the odds of eliciting aggression, exploratory area marking in Lasius niger seems to be rather a home-range than a true territorial marking. We discuss the role of collective exploration, home-range marking and intraspecific interactions in the structuring and use of foraging space by neighbour Lasius niger colonies.     

合肥市区城市森林景观格局分析

运用3S技术在分析合肥景观特点的基础上,研究了合肥市区17．6km^2范围内的城市森林景观特点及与其它景观单元间关系。结果表明,主要景观要素分为建筑与硬质铺装表面、城市森林斑块、一般绿地、道路、水面五大类景观背景为建筑及铺装表面,占总面积的73．13％;道路为典型的廊道景观,约占6．89％;研究区城市森林斑块共408块,计161．16hm^2,占总面积的9．8％,平均面积0．396hm^2、最大面积12hm^2,斑块形状复杂、近圆度小,其中48％的班块属于面积<500m^2的小班块,>1hm^2的城市森林班块只占8．6％;水面斑块147块,计149．93hm^2,占总面积的8．54％,平均面积1．02hm^2,最大面积16hm^2;一般绿地斑块255块,计39．74hm^2,占2．26％,最大面积3．86hm^2,平均面积0．1558hm^2．Shanlnon-Weiner景观多样性指数和均匀度均偏低,分别为0．9284和0．5768。另外,城市森林与一般绿地两类景观要素的总优势度达0．39,由于这两类景观斑块的尺度变化范围大,比较破碎,小尺度的斑块所占比例高,又主要集中在西区,分布不均匀,故对环境的影响作用受到限制,文中引用自然森林的内部生境概念,确定合肥城市森林斑块出现内部环境的l临界面积为9800m^2,研究区拥有城市森林的内部生境总面积为31．69hm^2,仅为城市森林面积的19．7％,不利于对物种提供更多的生境,提出应用内部生境的大小来划分城市森林斑块,建立城市森林小班块-中斑块-大斑块-特大斑块的尺度等级体系,据此提出,研究区各尺度的城市森林斑块面积比为2：2：2：3。同时提出合肥东北部应增加城市森林面积,尽可能建设1．5～3．0hm^2的片状城市森林。     

Prevalence and pattern of cognitive impairment in rural and urban populations from Northern Portugal

Background  

Despite worldwide recognition of the burden of dementia, no epidemiological data is yet available in Portugal. The objective of this study is to estimate the prevalence and describe the pattern of cognitive impairment with dementia or no dementia (CIND) in rural and urban populations from Northern Portugal.     

1996—2005年北京城市生态质量动态

从生态要素、生态过程、生态功能和生态问题4个主题出发,构建了包含16个指标的北京城市生态质量评价指标体系,并分别采用熵权法、最差状态法和最佳状态法对指标进行赋权,通过加权平均法构建了北京城市生态要素指数（EEI）、生态过程指数（EPI）、生态功能指数（EFI）、生态问题指数（EDI）和综合生态质量指数（CEI）,用以评价1996—2005年北京城市生态质量动态变化.结果表明：研究期间,北京城市EEI无明显改善,持续维持在远离理想点的水平;EPI和EFI改善显著,由1996年的远离理想点到2005年接近于理想点的水平;EDI的年度波动较大,普遍远离理想点;CEI得到持续改善,但离理想点依然有一定距离.当人均国内生产总值（GDP）小于3 000美元时,EPI、EFI和CEI随GDP的增长而快速增大,改善显著,当人均GDP超过3 000美元后,EPI、EFI和CEI随GDP增长而增大的速度减慢;EEI和EDI受人均GDP的影响较小,主要受限于自然条件及全球和区域环境的变化.     

Deriving fine-scale models of human mobility from aggregated origin-destination flow data

The spatial dynamics of epidemics are fundamentally affected by patterns of human mobility. Mobile phone call detail records (CDRs) are a rich source of mobility data, and allow semi-mechanistic models of movement to be parameterised even for resource-poor settings. While the gravity model typically reproduces human movement reasonably well at the administrative level spatial scale, past studies suggest that parameter estimates vary with the level of spatial discretisation at which models are fitted. Given that privacy concerns usually preclude public release of very fine-scale movement data, such variation would be problematic for individual-based simulations of epidemic spread parametrised at a fine spatial scale. We therefore present new methods to fit fine-scale mathematical mobility models (here we implement variants of the gravity and radiation models) to spatially aggregated movement data and investigate how model parameter estimates vary with spatial resolution. We use gridded population data at 1km resolution to derive population counts at different spatial scales (down to ∼ 5km grids) and implement mobility models at each scale. Parameters are estimated from administrative-level flow data between overnight locations in Kenya and Namibia derived from CDRs: where the model spatial resolution exceeds that of the mobility data, we compare the flow data between a particular origin and destination with the sum of all model flows between cells that lie within those particular origin and destination administrative units. Clear evidence of over-dispersion supports the use of negative binomial instead of Poisson likelihood for count data with high values. Radiation models use fewer parameters than the gravity model and better predict trips between overnight locations for both considered countries. Results show that estimates for some parameters change between countries and with spatial resolution and highlight how imperfect flow data and spatial population distribution can influence model fit.