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1.
In the 1950s and 1960s a group of housing economists at Columbia University developed a framework for the analyses of urban housing markets which was based around the concept of housing submarkets and household migration. There is now widespread agreement amongst housing economists that submarkets should be adopted as a working hypothesis but the concept has been reformulated in terms of intra‐urban relative house price differentials. The accepted test for submarket existence uses a hedonic model of house prices which assumes market equilibrium. This paper returns to an analysis of submarkets which focuses on spatial migration patterns. By examining household intra‐urban mobility patterns in the Glasgow housing market it is possible to demonstrate that submarkets tend to be self‐contained. The analysis also suggests that the current standard statistical tests may be incomplete and in the case of Glasgow underestimate the number of submarkets.  相似文献   
2.
乡村人口是城镇化进程中的主要微观行为主体,务实深入地研究他们行为决策的特征与机制,是制定合理的城镇化政策的基础。家庭是社会最基本的构成单元,家庭整体的综合理性是乡村人口进行迁居决策的主要基础。基于家庭单元的人口城镇化研究价值日益凸显。梳理武汉市域外围乡村地区的实地调研成果,构建基于家庭的分析框架,重点对不同家庭结构的行为选择特征进行机制解释。发现武汉所代表的中部大都市外围乡村家庭的迁居意愿总体较低,多数家庭通过代际间或夫妻间分工、劳动力近距离流动维持城乡二元兼业模式,家庭成员的行为选择相互补偿,共同追求家庭发展的均衡稳定,半城镇化模式是乡村人口长期理性选择下的均衡模式。城镇化政策的制定要打破这一均衡,必须立足家庭整体理性,顺应家庭聚合发展的总体趋势。  相似文献   
3.
The effects of Lignosite#rm lignosulfonate, a refined lignosulfonate product that is obtained from the sulfite pulping process, on growth and survival of plants were investigated. Following applications of 0, 7500, 15,000 and 22,500 cm3#shm2 to 32 plots within a forest plantation, the following were monitored: (1) live aboveground biomass of vascular plants, (2) growth of Douglar fir (Pseudotsuga menziesii) and (3) lignosulfonate migration through the soil profile. Live aboveground biomass of woody vegetation was not affected, and that of herbaceous plants was significantly decreased only at the two greatest application rates. Growth of the Douglas fir trees was not significantly affected. Lignosulfonates disappeared from the soil profile at the same rate regardless of initial concentration. Although it is not practical to use this material as a herbicide in western Washington, land application of lignosulfonates may be environmentally more attractive than traditional disposal methods.  相似文献   
4.
实验通过添加纳米粒子SiO2,研究抑制软质聚氯乙烯(PVC)中增塑剂邻苯二甲酸二辛脂(DOP)迁移规律,评价PVC样品溶剂抽出率,对挥发损失率、拉伸性能和邵氏硬度的测定分析,得出以下结论:纳米粒子SiO2可以抑制软质PVC中DOP的迁移。用正己烷浸泡PVC样品,随浸泡时间的延长,溶剂抽出率增大;随着添加的纳米SiO2含量的增加,样品的溶剂抽出率降低。在浸泡24h后,添加5份纳米SiO2样品PVC的溶剂抽出率为18.9%,比对照(25.6%)降低了26.2%。添加少量的纳米SiO2并没有使样品的挥发损失率明显降低,添加1~5份不同量的纳米SiO2的样品的挥发损失率均比不添加纳米SiO2的对照样品低。随着无机纳米粒子含量的增加,样品的拉伸强度和断裂伸长率反而降低,硬度有所增加。   相似文献   
5.
基于单轴变轨迹筛的动力学模型, 通过激振位置的变换考察了整个筛面上的运移规律及其在xy方向的振幅以及绕质心的摇摆幅变化谱图.分析结果表明:激振位置处于筛面右下侧时, 筛箱的动力学性能最优;当激振力相对于质心中心对称时, 筛箱质心两侧运移规律正好相反, 激振力在上, 两侧振动方向角的交线在上, 反之在下;在靠近激振力一侧的筛面振幅大, 远离侧振幅小;筛面上任意点在x方向的振幅依赖于激振位置 (Lox, Loy) , 相对于筛箱质心对称布置的点, 在x方向振幅的变化图谱上有相反的变化规律, 在y方向的振幅主要受Lox影响;距离质心越远的点, 其振动响应幅值越大且存在极限值.  相似文献   
6.
目的:研究单甘酯对冷冻鱼面冻藏稳定性的影响。方法:比较单甘酯不同添加量的鱼面在冻融循环4次过程中的品质变化;采用质构仪、核磁共振仪、差示扫描量热仪测定鱼面拉断力、水分分布、玻璃化转变温度(Tg’)。结果:单甘酯添加量0.20%时,鱼面的拉断力达134.06 g,空白为107.42 g,冻融4次后,分别为75.12、46.35 g;面汤吸光度比空白低22.54%。空白鱼面自由水和含0.20%单甘酯的鱼面相应自由水含量分别为84.02%、81.69%,冻融处理4次后,自由水分别是增加到87.82%、83.33%。空白鱼面Tg’为-23.03℃,冻融4次后Tg’为-26.08℃;添加0.2%单甘酯的鱼面Tg’和冻融4次后的Tg’分别是-17.76、-18.57℃。结论:添加0.20%单甘酯能有效提高鱼面拉断力,降低蒸煮损失、自由水含量,并对面条冻融过程中结合水转化为自由水有一定抑制作用,还能明显提高鱼面的Tg’,在-20℃下可实现玻璃化贮藏。   相似文献   
7.
The good treatment of skin defects has always been a challenge in the medical field, and the emergence of tissue engineering skin provides a new idea for the treatment of injured skin. However, due to the single seed cells, the tissue engineering skin has the problem of slow vascularization at the premonitory site after implantation into the human body. Cell co-culture technology can better simulate the survival and communication environment of cells in the human body. The study of multicellular co-culture hopes to bring a solution to the problem of tissue engineering. In this paper, human skin fibroblasts (HSFs) and human vascular endothelial cells (HVECs) were co-cultured in Transwell. The Cell Counting Kit 8 (CCK8), Transwell migration chamber, immunofluorescence, Western blot (WB), and real time quantitative PCR (RT-qPCR) were used to study the effects of HVECs on cell activity, migration factor (high mobility group protein 1, HMGB1) and vascularization factor (vascular endothelial growth factor A, VEGFA and fibroblast growth factor 2, FGF2) secretion of HSFs after co-cultured with HVECs in the Transwell. The biological behavior of HSFs co-cultured with HVECs was studied. The experimental results are as follows: (1) The results of cck8 showed that HVECS could promote the activity of HSFs. (2) HVECs could significantly promote the migration of HSFs and promote the secretion of HMGB1. (3) HVECs could promote the secretion of VEGFA and FGF2 of HSFs. (4) The HVECs and HSFs were inoculated on tissue engineering scaffolds at the ratio of 1:4 and were co-cultured and detected for 7 days. The results showed that from the third day, the number of HSFs was significantly higher than that of the control group without HVECs.  相似文献   
8.
Cold Atmospheric Plasma (CAP) is an emerging technology with great potential for biomedical applications such as sterilizing equipment and antitumor strategies. CAP has also been shown to improve skin wound healing in vivo, but the biological mechanisms involved are not well known. Our study assessed a possible effect of a direct helium jet CAP treatment on keratinocytes, in both the immortalized N/TERT-1 human cell line and primary keratinocytes obtained from human skin samples. The cells were covered with 200 µL of phosphate buffered saline and exposed to the helium plasma jet for 10–120 s. In our experimental conditions, micromolar concentrations of hydrogen peroxide, nitrite and nitrate were produced. We showed that long-time CAP treatments (≥60 s) were cytotoxic, reduced keratinocyte migration, upregulated the expression of heat shock protein 27 (HSP27) and induced oxidative cell stress. In contrast, short-term CAP treatments (<60 s) were not cytotoxic, did not affect keratinocyte proliferation and differentiation, and did not induce any changes in mitochondria, but they did accelerate wound closure in vitro by improving keratinocyte migration. In conclusion, these results suggest that helium-based CAP treatments improve wound healing by stimulating keratinocyte migration. The study confirms that CAP could be a novel therapeutic method to treat recalcitrant wounds.  相似文献   
9.
p27kip1 is a multifunctional protein that promotes cell cycle exit by blocking the activity of cyclin/cyclin-dependent kinase complexes as well as migration and motility via signaling pathways that converge on the actin and microtubule cytoskeleton. Despite the broad characterization of p27kip1 function in neural cells, little is known about its relevance in microglia. Here, we studied the role of p27kip1 in microglia using a combination of in vitro and in situ approaches. While the loss of p27kip1 did not affect microglial density in the cerebral cortex, it altered their morphological complexity in situ. However, despite the presence of p27kip1 in microglial processes, as shown by immunofluorescence in cultured cells, loss of p27kip1 did not change microglial process motility and extension after applying laser-induced brain damage in cortical brain slices. Primary microglia lacking p27kip1 showed increased phagocytic uptake of synaptosomes, while a cell cycle dead variant negatively affected phagocytosis. These findings indicate that p27kip1 plays specific roles in microglia.  相似文献   
10.

针对8 m大采高综采工作面人员作业区域粉尘来源不清、治理重点不明,且缺少理论支撑的问题,选取神东补连塔煤矿12513综采工作面为研究对象,采用数值模拟和现场测试相结合的方法,分别研究采煤机割煤和降柱移架2个主要尘源单独作用、共同作用时的粉尘运移规律,分析了采煤机附近区域人员呼吸带的呼吸性粉尘质量浓度分布情况。研究结果表明,8 m大采高综采工作面在顺风、逆风割煤两种工况下采煤机附近人员作业区域呼吸性粉尘质量浓度最高处均在采煤机中部位置,分别为203.8、111.6 mg/m3,此处降柱移架产生的粉尘质量浓度为90.7 mg/m3,源于降柱移架尘源的占比分别为44.50%、76.69%。粉尘溯源研究成果可以为大采高综采工作面粉尘的针对性治理提供理论依据。

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