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排序方式: 共有377条查询结果,搜索用时 15 毫秒
1.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
2.
Syms R.R.A. Yeatman E.M. Bright V.M. Whitesides G.M. 《Journal of microelectromechanical systems》2003,12(4):387-417
Because of the low dimensional power of its force scaling law, surface tension is appropriate for carrying out reshaping and assembly in the microstructure size domain. This paper reviews work on surface tension powered self-assembly of microstructures. The existing theoretical approaches for rotational assembly are unified. The demonstrated fabrication processes are compared. Mechanisms for accurately determining the assembled shape are discussed, and the limits on accuracy and structural distortion are considered. Applications in optics, electronics and mechanics are described. More complex operations (including the combination of self-assembly and self-organization) are also reviewed. 相似文献
3.
Spontaneous regression of AK-5, a histiocytic tumor, is mediated by CD3-, CD8+ NK cells through ADCC. The onset of AK-5 regression is associated with the induction of humoral immune response and the augmentation of effector function. The mechanism of tumor cell death involves both necrosis and apoptosis. Interleukin-12, a 75-kDa heterodimeric cytokine, has multiple effects on T and NK cells. We have investigated the role of IL-12 in the NK cell-mediated AK-5 tumor regression process. Subcutaneous transplantation of AK-5 tumor induced the expression of IL-12 (p35 and p40) message by Day 6-8 in the splenocytes of syngenic rats. Similarly, analysis of serum samples from tumor-bearing animals showed the presence of circulating IL-12 around the same time. Interaction of immune cells with antibody-tagged AK-5 cells in vitro also triggered the expression of IL-12 message and protein by 3 hr. The circulating IL-12 in the sera of tumor-rejecting animals, as well as rIL-12, stimulated NK cell proliferation, expression of CD16 and CD25, and the activation of NK cells function. These observations suggest that the ability of the AK-5 tumor to induce the endogenous production of IL-12 may be responsible for keeping the NK cells constantly in an activated state, thus demonstrating an efficient mechanism for the complete regression of the tumor. 相似文献
4.
Summary Poly(N-vinyl-2-pyrrolidone) is miscible with poly(3-chloropropyl methacrylate), poly(2-bromoethyl methacrylate) and poly(2-iodoethyl methacrylate) as shown by the optical clarity and the glass transition behaviour of the blends. The miscible blends degrade before phase separation could be induced by heating. The three Tg-composition curves can be fitted by the Gordon-Taylor equation. The implication of the Gordon-Taylor k parameters of the blends is discussed. 相似文献
5.
Driving a Wedge Between Evidence and Beliefs: How Online Ideological News Exposure Promotes Political Misperceptions
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R. Kelly Garrett Brian E. Weeks Rachel L. Neo 《Journal of Computer-Mediated Communication》2016,21(5):331-348
This article has 2 goals: to provide additional evidence that exposure to ideological online news media contributes to political misperceptions, and to test 3 forms this media‐effect might take. Analyses are based on representative survey data collected during the 2012 U.S. presidential election (N = 1,004). Panel data offer persuasive evidence that biased news site use promotes inaccurate beliefs, while cross‐sectional data provide insight into the nature of these effects. There is no evidence that exposure to ideological media reduces awareness of politically unfavorable evidence, though in some circumstances biased media do promote misunderstandings of it. The strongest and most consistent influence of ideological media exposure is to encourage inaccurate beliefs regardless of what consumers know of the evidence. 相似文献
6.
This study is an empirical investigation of problematic instant messaging (IM) use among university students in Singapore. It adapts Caplan's (2005) theoretical framework of problematic Internet use (PIU) to the context of problematic IM use by linking pre-existing human dispositions to cognitive-behavioral symptoms and negative outcomes of improper IM use. Four new factors—oral communication apprehension, polychronicity, perceived inconvenience of using offline communication means, and trait procrastination—were tested as predictors of problematic IM use. The results provided strong support for Caplan's theoretical framework of PIU and indicated that oral communication apprehension and perceived inconvenience of using offline means were significant predictors of problematic IM use, whereas polychronicity and trait procrastination were not. The implications of these findings are discussed. 相似文献
7.
不久前笔者购买了一台电脑,采用Intel Pentium E2180双核处理器,在现场验机时,看到开机自检信息和系统属性中均显示出正确的处理器型号,于是就打包拿回了家。不料再开机使用时才发现,任务管理器中只有一颗核心的占用率信息(正常应该是两颗),而且在CPU-Z和Everest检测软件中均显示处理器型号为Intel Pentium E2180,但核心却只有一个(图1、图2)。难道双核处理器也有假货吗? 相似文献
8.
DI Blyth MS Pedrick TJ Savage H Bright JE Beesley S Sanjar 《Canadian Metallurgical Quarterly》1998,19(1):38-54
9.
J. Sun Y. S. Wong M. Rahman Z. G. Wang K. S. Neo C. H. Tan 《Machining Science and Technology》2013,17(3):355-370
Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect. 相似文献
10.
The use of hydrogel in cartilage tissue engineering is especially popular due to its high hydrophilic property which is similar to native cartilage matrix. Alginate hydrogel was used as a transient scaffold material to facilitate chondrocyte proliferation into a three‐dimensional scaffold‐free living hyaline cartilaginous graft (LhCG). As LhCG is purely cell‐based and has a marked resemblance to native hyaline cartilage, it served as an excellent in vitro platform for studying the endochondral ossification pathway. Due to the complexity of events involved throughout endochondral ossification, this study only focuses on early stages of the process where it involves chondrocyte hypertrophy and blood vessel invasion. Human umbilical vein endothelial cells (HUVECs) were selected as the target cells for possible endothelialization in the LhCG template. They were seeded onto the LhCG construct and subjected to vascular endothelial growth factor (VEGF) treatment. Results suggested that VEGF is indeed a potent driving force for initiation of the endochondral pathway. It alone is sufficient to induce hypertrophy in chondrocytes and the corresponding expression of osteogenic genes with or without the presence of HUVECs in the LhCG template. On the other hand, the effect of HUVECs in the LhCG system was less evident. It is hypothesized that this is attributed to the preservation of anti‐angiogenic properties in primary chondrocytes from the LhCG construct, inhibiting HUVECs from endothelialization in the LhCG+HUVEC construct. Based on the outcome from this study, it is recommended that hypertrophy in chondrocytes should be induced prior to endothelial cell introduction so that the microenvironment will be altered to favor angiogenesis within the cartilaginous template. © 2013 Society of Chemical Industry 相似文献