Geometrical effects in microfluidic-based microarrays for rapid, efficient single-cell capture of mammalian stem cells and plant cells

In this paper, a detailed numerical and experimental investigation into the optimisation of hydrodynamic micro-trapping arrays for high-throughput capture of single polystyrene (PS) microparticles and three different types of live cells at trapping times of 30 min or less is described. Four different trap geometries (triangular, square, conical, and elliptical) were investigated within three different device generations, in which device architecture, channel geometry, inter-trap spacing, trap size, and trap density were varied. Numerical simulation confirmed that (1) the calculated device dimensions permitted partitioned flow between the main channel and the trap channel, and further, preferential flow through the trap channel in the absence of any obstruction; (2) different trap shapes, all having the same dimensional parameters in terms of depth, trapping channel lengths and widths, main channel lengths and widths, produce contrasting streamline plots and that the interaction of the fluid with the different geometries can produce areas of stagnated flow or distorted field lines; and (3) that once trapped, any motion of the trapped particle or cell or a shift in its configuration within the trap can result in significant increases in pressures on the cell surface and variations in the shear stress distribution across the cell’s surface. Numerical outcomes were then validated experimentally in terms of the impact of these variations in device design elements on the percent occupancy of the trapping array (with one or more particles or cells) within these targeted short timeframes. Limitations on obtaining high trap occupancies in the devices were shown to be primarily a result of particle aggregation, channel clogging and the trap aperture size. These limitations could be overcome somewhat by optimisation of these device design elements and other operational variables, such as the average carrier fluid velocity. For example, for the 20 μm polystyrene microparticles, the number of filled traps increased from 32% to 42% during 5–10 min experiments in devices with smaller apertures. Similarly, a 40%–60% reduction in trapping channel size resulted in an increase in the amount of filled traps, from 0% to almost 90% in 10 min, for the human bone marrow derived mesenchymal stem cells, and 15%–85% in 15 min for the human embryonic stem cells. Last, a reduction of the average carrier fluid velocity by 50% resulted in an increase from 80% to 92% occupancy of single algae cells in traps. Interestingly, changes in the physical properties of the species being trapped also had a substantial impact, as regardless of the trap shape, higher percent occupancies were observed with cells compared to single PS microparticles in the same device, even though they are of approximately the same size. This investigation showed that in microfluidic single cell capture arrays, the trap shape that maximizes cell viability is not necessarily the most efficient for high-speed single cell capture. However, high-speed trapping configurations for delicate mammalian cells are possible but must be optimised for each cell type and designed principally in accordance with the trap size to cell size ratio.     

Correlates of sexual abuse and smoking among French adults

OBJECTIVE: The goal of this study was to examine the association between sexual abuse (SA) and initiation, cessation, and current cigarette smoking among a large representative adult population in France. METHOD: A random sample size of 12,256 adults (18-75 years of age) was interviewed by telephone concerning demographic variables, health practices and beliefs, and health status--for which SA and tobacco questions were included. Bivariate and multivariate analyses were conducted. RESULTS: Nearly 46% of SA survivors were current smokers compared to 34% of non-abused persons (p<.001). Survivors of SA consumed more cigarettes per day than non-abused individuals (14.5 vs. 12.4, p<.01). Survival analysis showed an increased risk of smoking initiation for respondents abused before 18 (adjusted relative hazard=1.55; p<.0001) with referent to the non-abused group. SA was not found to be a significant predictor of current smoking status among those who began smoking after the first incident of SA. Respondents who were not sexually abused were 1.8 times (95% CI, 1.12-2.99) more likely to quit smoking than people who began smoking after they were sexually abused. CONCLUSIONS: The early identification and treatment of sexually abused persons is critical to decrease smoking among adolescents and adults because of the association of SA with both smoking initiation and decreased cessation rates. It may be more difficult to detect an association between SA and current smoking due to the high rates of smoking and lower rates of quitting among the general French population.     

教育装备综合效益评估模型研究

由于科技与信息技术的快速发展,作为教育教学基础性设施的教育装备,已成为提高教育教学效果与效益的根本保障和技术手段。以模糊数学作为分析工具,对教育装备的综合效益评估进行系统分析,并提出相应的评价模型,以此来为教育装备的进一步投资建设与规划提供理论参考。     

Decrease in Ammonia Excretion by Boleophthalmus Boddaerti(Mudskipper) Exposed to Cyanide

ThetoleranceofthemudskipperBoleophthalmusboddaertitocyanideishigherthanthoseofotherfishes[1].Suchahightolerancetocyanidedoesnotinvoveareductionofmetabolicrateoranenhancedanaerobicmetabolism,oracyanide-insensitiverespiratorypathway.Instead,itisaresultofthepresenceofasurplusofcytochromeoxidaseandinduciblecyanide-detoxifyingmechanisms,tumingcyanideinthiocyanate,inthismudskipper[1].ThoughCN-isdetoxifiedtoSCN-,realizingbiomembranesaremorepermeabletoHCNthanCN-,wedecidedtoinvestigateiftheprotondi…     

认知运动心理学——历史、现状与未来

本文回顾了认知心理学发展的历史,介绍了认知心理学中信息加工观点和生态学观点之间的明显对立.在此基础上,简述了认知运动科学发展的情况,讨论了认知运动心理学的定义.作者认为,认知运动心理学将跨出信息加工理论的狭小天地,从人是活跃的思维有机体、是行为的认知调节器的观点出发,研究并帮助运动员解决所面临的问题;认知技能训练的研究及研究成果的应用将成为认知运动科学的主题.