Three-dimensional cellular focusing utilizing a combination of insulator-based and metallic dielectrophoresis

Particle focusing in microfluidic devices is a necessary step in medical applications, such as detection, sorting, counting, and flow cytometry. This study proposes a microdevice that combines insulator-based and metal-electrode dielectrophoresis for the three-dimensional focusing of biological cells. Four insulating structures, which form an X pattern, are employed to confine the electric field in a conducting solution, thereby creating localized field minima in the microchannel. These electrodes, 56-μm-wide at the top and bottom surfaces, are connected to one electric pole of the power source. The electrodes connected to the opposite pole, which are at the sides of the microchannel, have one of three patterns: planar, dual-planar, or three-dimensional. Therefore, low-electric-field regions at the center of the microchannel are generated to restrain the viable HeLa cells with negative dielectrophoretic response. The array of insulating structures aforementioned is used to enhance the performance of confinement. According to numerical simulations, three-dimensional electrodes exhibit the best focusing performance, followed by dual-planar and planar electrodes. Experimental results reveal that increasing the strength of the applied electric field or decreasing the inlet flow rate significantly enhances focusing performance. The smallest width of focusing is 17 μm for an applied voltage and an inlet flow rate of 35 V and 0.5 μl/min, respectively. The effect of the inlet flow rate on focusing is insignificant for an applied voltage of 35 V. The proposed design retains the advantages of insulator-based dielectrophoresis with a relatively low required voltage. Additionally, complicated flow controls are unnecessary for the three-dimensional focusing of cells.     

Effects of curricular activity on students' situational motivation and physical activity levels

The purpose of this study was to examine (a) the effects of three curricular activities on students'situational motivation (intrinsic motivation [IM], identified regulation [IR], external regulation, and amotivation [AM]) and physical activity (PA) levels, and (b) the predictive strength of situational motivation to PA levels. Four hundred twelve students in grades 7-9 participated in three activities (cardiovascular fitness, ultimate football, and Dance Dance Revolution [DDR]) in physical education. ActiGraph GT1M accelerometers were used to measure students' PA levels for three classes for each activity. Students also completed a Situational Motivation Scale (Guay, Vallerand, & Blanchard, 2000) at the end of each class. Multivariate analysis of variance revealed that students spent significantly higher percentages of time in moderate-to-vigorous PA (MVPA) in fitness and football classes than they did in DDR class. Students reported higher lM and IR toward fitness than DDR They also scored higher in IR toward fitness than football. In contrast, students displayed significantly lower AM toward fitness than football and DDR Hierarchical Linear Modeling revealed that IM was the only positive predictor for time in MVPA (p = .02), whereas AM was the negative predictor (p < .01). The findings are discussed in regard to the implications for educational practice.     

人工智能伦理准则与治理体系:发展现状和战略建议

首先,界定人工智能伦理准则的基本概念,分析人工智能发展现状。然后,探讨导致人工智能伦理问题的主要原因,总结人工智能典型应用场景下的伦理问题,包括自动驾驶、智能媒体、智慧医疗、服务机器人等;此外,围绕应对人工智能伦理问题的基本原则探索治理框架体系,包括技术应对、道德规范、政策引导、法律规则等方面。最后,结合我国人工智能发展规划战略部署,指出在社会治理的落地过程中宜采取分层次、多维度的治理体系,并提出在人工智能伦理准则和治理方面的具体措施建议(2020-2035年),包括社会宣传、标准体系、法律法规等方面。     

组织忘却学习如何影响绩效：基于元分析的证据

利用元分析方法对国内外43篇组织忘却学习与绩效关系的实证研究进行分析,并探讨测量维度、地区文化和中介变量等因素是否会影响二者关系.研究结果表明,组织忘却学习与绩效显著正相关,测量维度、地区文化和中介变量对二者关系有显著的影响,在单维度测量、东方文化背景下或有中介变量存在时,组织忘却学习与其绩效的相关程度更高.     

国外基于工作任务的信息搜索行为研究进展*

系统地梳理国外相关文献,旨在把握国外信息搜索行为研究进展,揭示国外信息搜索行为研究视角、研究方法、研究内容和研究趋势,以期为我国信息搜索行为研究提供借鉴和参考.对94篇文献采用综合、归纳、比较等方法进行综合分析,在知识脉络研究部分分研究对象、研究方法、研究内容进行梳理,信息搜索行为研究内容按科研人员、大学生、专业技术人员、其他人群分别进行述评.国外基于工作任务的信息搜索行为研究进展对我国搜索行为研究的启示,一是研究对象上要扩宽;二是在研究方法上寻求突破和创新;三是跨学科合作研究.     

舟山某海域海上自升式平台桩基稳定性研究

地基承载力和地基沉降分析对自升式海洋平台安全作业极为重要.以舟山某海域自升式海洋平台为研究对象,分别采用理论分析和数值模拟的方法对不同入泥深度的桩靴地基承载力和沉降进行计算分析,并开展桩靴几何尺寸对地基承载力影响的敏感度分析.研究结果表明:(1)采用《海洋井场调查规范》理论分析和FLAC3D数值模拟所得到的桩靴安全插桩深度分别为15 m和14 m,结果接近.(2)采用《建筑地基基础设计规范》和FLAC3D数值模拟得到的地基沉降量分别为335.61 mm和260.55mm,相差约28.8％.(3)方形桩靴的长度对地基承载力的影响最大,桩靴长度增加11％,相应的地基承载力增加27％,桩靴高度和桩腿直径对地基承载力影响可以忽略不计.     

Inertial microfluidics in contraction–expansion microchannels: A review

Inertial microfluidics has brought enormous changes in the conventional cell/particle detection process and now become the main trend of sample pretreatment with outstanding throughput, low cost, and simple control method. However, inertial microfluidics in a straight microchannel is not enough to provide high efficiency and satisfying performance for cell/particle separation. A contraction–expansion microchannel is a widely used and multifunctional channel pattern involving inertial microfluidics, secondary flow, and the vortex in the chamber. The strengthened inertial microfluidics can help us to focus particles with a shorter channel length and less processing time. Both the vortex in the chamber and the secondary flow in the main channel can trap the target particles or separate particles based on their sizes more precisely. The contraction–expansion microchannels are also capable of combining with a curved, spiral, or serpentine channel to further improve the separation performance. Some recent studies have focused on the viscoelastic fluid that utilizes both elastic forces and inertial forces to separate different size particles precisely with a relatively low flow rate for the vulnerable cells. This article comprehensively reviews various contraction–expansion microchannels with Newtonian and viscoelastic fluids for particle focusing, separation, and microfluid mixing and provides particle manipulation performance data analysis for the contraction–expansion microchannel design.     

我国文化创意产业知识产权政策文本量化分析

梳理文化创意产业知识产权政策发展历程,探析演变规律,总结发展趋势,运用文本量化方法,对我国2004-2019年393项与文化创意产业知识产权相关的政策进行词频分析、社会语义网络分析、聚类分析和政策空间分布分析.研究发现:文化创意产业知识产权政策的演化历程兼具稳定性和波动性;国家层面政策和地方层面政策之间既有联系也有差异;文化创意产业知识产权治理逐步从一元化走向多元化;政策主题逐渐丰富但聚合度较低,政策体系逐步完善;政策发展速度快,区域差异较大.     

智慧城市PPP运作模式构建研究

探讨智慧城市PPP模式应用中存在的问题;提出项目识别与准备、项目采购、项目执行与移交过程中的关键决策点、社会资本选择.PPP模式在智慧城市建设中的有效性取决于决策的科学性.以四川德阳为例提出引入专家辅助决策、合理把控政府在智慧城市PPP项目中的介入权等对策.     

新农保对农村居民幸福感的提升效应——基于CGSS的微观数据库

基于2013年和2015年的CGSS数据,分析新农保对农村居民幸福感的影响,并利用中介效应模型从心理状态、社交状态、自评经济、自评健康四个维度探究其影响机制.结果表明:新农保可以有效提升农村居民幸福感,在新农保对农村居民幸福感的影响中,心理状态、社交状态、自评经济都起到了部分中介作用,而自评健康的中介作用并不显著.据此,提出进一步推进新农保保障工作、加大缴费档次宣传力度、提升农村重大风险疾病防控能力等建议.