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51.
吴蓉  黄旭  刘晔  李志刚  刘于琪 《地理科学》2019,39(5):734-741
基于2015年广州市1 273份居民问卷调查和半结构性访谈数据,结合逐步LPM回归和中介效应模型,探讨地方依恋和社区参与两者关系中存在的中介效应及其传导机制,并系统对比本地居民与外来移民之间的差异。研究发现:社区居民的地方依恋能够直接提升其社区参与期望;社区参与行为作为一个中介变量,在地方依恋对社区参与期望的影响中发挥中介效应;对比本地居民,外来移民的社区参与行为和期望程度相对较低;外来移民的社区参与行为对其社区参与期望影响的中介效应相对较弱。揭示了中国城市居民社区参与中存在户籍制度壁垒,需要进一步通过社区公共服务均等化措施,提升居民尤其是外来移民的获得感、幸福感和安全感。  相似文献   
52.
Sediment cores were collected from the subaqueous delta of the Changjiang Estuary. Sediment grain-size profiles and their fractal dimensions were analyzed, to elucidate responses to long-term sedimentary processes. In addition, the environmental sensitive populations of grain size have been extracted. The sediment cores can be divided into two parts, according to the sedimentary structures present. The upper part (0-12 cm) is interpreted as being the active layer, which is influenced frequently by changes i...  相似文献   
53.
异育银鲫气单胞菌病原菌鉴定和药敏试验   总被引:1,自引:0,他引:1  
从患病异育银鲫体内分离到5株可疑菌株,经API 20NE细菌生化鉴定,YCS07-03和YZ07-11株鉴定率为99.2%和99.3%。注射感染中5×108 CFU.mL-1剂量组表现出较强的致病性,12 d死亡率100%。菌株在营养肉汤培养液中呈均匀混浊状;在营养琼脂平皿中呈灰白色半透明菌落;在血琼脂培养基中呈光滑灰白色菌落,YZ07-11株出现透明的β溶血环;在TCBS培养基呈黄色菌落;在SS和麦康凯培养基中形成无色透明的扁平菌落。经负染电镜观察,菌株两端圆,呈直杆状,无芽孢,极生单鞭毛,菌株大小(短径×长径)分别为1.53μm×2.71μm和0.80μm×2.12μm。菌株经生化实验鉴定为温和气单胞菌(Aeromonas sobria)和嗜水气单胞菌(Aeromonas hydrophila)。试验结果表明:菌株对丁胺卡那霉素、头孢噻肟、庆大霉素、左氟沙星、复合磺胺、氟嗪酸、洛美沙星、复方新诺明、链霉素和新霉素均产生高度敏感;对万古霉素为中度敏感;氨苄青霉素、羧苄青霉素、强力霉素和青霉素产生耐药。  相似文献   
54.
DNA甲基化在调节动物生长发育和组织分化中发挥了重要作用。本研究主要从酶切、预扩和选扩等方面优化了中国对虾DNA甲基化分析的MSAP技术,给出了适合中国对虾MSAP分析的最近反应程序和体系,并采用该技术分别对中国对虾选育群体"黄海1号"和野生群体的肌肉、鳃和血细胞三种组织基因组DNA的CCGG甲基化水平进行分析。研究结果表明,中国对虾野生群体肌肉、鳃和血细胞的DNA甲基化比例分别为23.1%、22.3%和19.7%,选育群体"黄海1号"肌肉、鳃和血液的甲基化比例分别为21.4%、19.6%和18.9%。鳃组织的DNA甲基化水平在两群体中差异极显著(P <0.01),肌肉间的甲基化水平差异显著(P <0.05),而血细胞中甲基化水平差异不显著(P >0.05)。中国对虾野生群体和"黄海1号"同一组织间的甲基化水平不同(P ≤ 0.05),而不同组织间的甲基化水平也各不相同(P ≤ 0.05)。DNA甲基化多态性分析表明,野生群体和选育群体"黄海1号"的鳃和血细胞组织的甲基化多态性比例变化明显,而肌肉组织甲基化水平较稳定,这些变化趋势与CCGG位点的甲基化和去甲基化有关。  相似文献   
55.
应用WRF V3.5中尺度模式,对陕西省2013年7月12~13日的一次暴雨过程进行数值模拟,并设计了降低地形和减少水汽含量2个敏感性试验,探讨了地形和水汽对本次暴雨过程的影响。结果表明:(1)模式能较好地模拟出本次暴雨天气过程,反映出了主要雨带的形状,但模拟的降水量存在偏差,其可能原因是初始场不能合理反映大气实况;(2)嵌套区域d02的地形高度降低至原始高度的1/3后,107°E~109°E范围的散度垂直剖面呈辐合—辐散的双重结构,暴雨区上空中低层假相当位温梯度变大,垂直上升运动增强,进而改变了降水的强度和范围;(3)将初始场中暴雨区南面的水汽含量减少20%后,水汽通量散度极值中心值减少1/3,进而导致模拟区域的雨量减少了58%,表明偏南水汽的输送对本次暴雨雨量有显著增幅作用,暴雨过程中水汽聚集程度是判断暴雨过程雨量大小的关键因素之一。  相似文献   
56.
Optimum fill pressures for direction-sensitive dark matter detectors based on tracking in gases are considered. Given the minimum resolvable track length and the gas fill, the Lindhard–Scharf stopping model leads to the existence of an optimum pressure which maximizes the specific event rate R (event rate per unit detector volume). In addition, maximizing the detectibility of the recoil nucleus diurnal asymmetry is considered. Optimum fill pressures are calculated for Ar, CF4, CS2 and Xe gas fills, as a function of the WIMP mass and the minimum resolvable track length. The associated minimum target volumes required to achieve currently competitive WIMP-nucleon cross-section sensitivity are also calculated. The standard isothermal sphere model of the galactic WIMP halo is used throughout, but the method could be extended to use any desired WIMP distribution function.  相似文献   
57.
Interest in integrating human connections and natural areas into resource management decision making has steadily increased. While efforts to validate place meaning dimensions have identified meanings beyond established place dependence and identity concepts, further research to identify tangible and intangible meanings of nature-based recreation areas is needed. This study sought to examine place meanings as a second-order construct consisting of ecological integrity, economic dependency, place dependence, family identity, community identity, and place identity and to determine the influence of place meanings on participatory planning intentions (PPI). Data were collected from Florida Fish and Wildlife Conservation area visitors. Confirmatory factor analysis revealed that six factors were reliable and valid, representing place meanings as an overarching concept. Structural equation modeling showed a significant association between place meanings and PPI. These findings demonstrated the importance of understanding place meanings that influence behavioral intentions, which is relevant to understanding participation in planning processes.  相似文献   
58.
The Goutte d'Or neighborhood of Paris has long been seen as an impoverished yet colorful quarter of the city. In recent years, it has also developed a reputation as a center for immigrants. Three populations now share the neighborhood: the European French, the Maghrebi immigrant population and their children, and the newest population of migrants from former Francophone colonies. This paper examines how the Goutte d'Or's social and ethnic identity is revealed in the built environment and in its social and economic activity. This neighborhood demonstrates how different communities and place identities coexist. It also shows how global networks of migration, exchange, and visits infuse local places. The Goutte d'Or distills many aspects of French immigrant identities, providing an example for increasing numbers of immigrant neighborhoods in France and across the world.  相似文献   
59.
Geo-folksonomies link social web users to geographic places through the tags users choose to label the places with. These tags can be a valuable source of information about the user’s perception of place and can reflect their experiences and activities in the places they label. By analysing the associations between users, places and tags, an understanding of a place and its relationships with other places can be drawn. This place characterisation is unique, dynamic and reflects the perception of a particular user community that generated the geo-folksonomy. In this work, an approach is proposed to analysing geo-folksonomies that builds on and extends existing statistical methods by considering specific concepts of relevance to geographic place resources, namely, place types and place-related activities, and by building a place ontology to encode those concepts and relationships. The folksonomy analysis and evaluation are demonstrated using a realistic geo-folksonomy data set. The resulting ontology is used to build user profiles from the folksonomy. The derived profiles reflect the association between users and the specific places they tag as well as other places with relevant associated place type and activities. The methods proposed here provide the potential for many interesting and useful applications, including the harvesting of useful insight on geographic space and employing the derived user profiles to enhance the search experience and to identify similarities between users based on their association to geographic places.  相似文献   
60.
Using the radius of gyration from fractal theory, this paper describes the calculation of fractal dimensions for the four tiers of central places in the Jilin Central Urban Agglomeration(JCUA), Jilin Province, China and the structural characteristics of each tier: 1) the 1st tier central place, Changchun Proper(not including Shuangyang District), provides the most service functions and has the most stable primate position; 2) the 2nd tier central places, Jilin Proper, Siping Proper, Liaoyuan Proper and Songyuan Proper have unclear statuses and do not provide certain functions; 3) the 3rd tier central places comprise 23 county-level cities, counties and urban districts(including Shuangyang District of Changchun), exhibiting a dense spatial structure that agrees with theory; 4) the 4th tier contains the largest number of central places(248 designated towns), but they are loosely distributed. In this study, a spatial image of the JCUA was created, based on vectorized data of the urban settlement distribution, which was then modified and abstracted to create a hexagonal network covering the JCUA. Compared to the traditional central place model, the modified spatial image conforms to the K = 3 principle. In reality, however, the growth of some 3rd tier central places should be increased with the cities being upgraded to the 2nd tier so as to overcome that tier′s functional deficiency. The loose distribution in the 4th tier should also be changed. This apparent anomaly can be explained by the fact that the classic hexagon model used to describe the way market areas layout does not exist in the real world. However, this should not be viewed as an obstacle to using central place theory. If its assumptions are properly applied, it can still assist research into the spatial structure of regions.  相似文献   
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