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The study investigates the use of CO2 laser to induce glass strip peeling off to form microchannels on soda lime gass substrate. The strip peeling exhibits a strong dependence on the energy deposition rate on the glass surface. In spite of the vast difference in the combination of laser power and scanning speed, when the ratio of the two makes the energy deposition rate in the range 3.0-6.0 J/(cm2 s), the temperature rising inside glass will be above the strain point and reach the softening region of the glass. As a result, glass strip peeling is able to occur and form microchannels with dimensions of 20-40 μm in depth and 200-280 μm in width on the glass surface. Beyond this range, higher energy depsotion rate would lead to surface melting associated with solidification cracks and lower energy deposition rate causes the generation of fragment cracks. 相似文献
995.
Embryoid body (EB) formation forms an important step in embryonic stem cell differentiation invivo. In murine embryonic stem cell (mESC) cultures EB formation is inhibited by the inclusion of leukaemic inhibitory factor (LIF) in the medium. Assembly of mESCs into aggregates by positive dielectrophoresis (DEP) in high field regions between interdigitated oppositely castellated electrodes was found to initiate EB formation. Embryoid body formation in aggregates formed with DEP occurred at a more rapid rate-in fact faster compared to conventional methods-in medium without LIF. However, EB formation also occurred in medium in which LIF was present when the cells were aggregated with DEP. The optimum characteristic size for the electrodes for EB formation with DEP was found to be 75-100 microns; aggregates smaller than this tended to merge, whilst aggregates larger than this tended to split to form multiple EBs. Experiments with ESCs in which green fluorescent protein (GFP) production was targeted to the mesodermal gene brachyury indicated that differentiation within embryoid bodies of this size may preferentially occur along the mesoderm lineage. As hematopoietic lineages during normal development derive from mesoderm, the finding points to a possible application of DEP formed EBs in the production of blood-based products from ESCs. 相似文献
996.
Zheng-Guang Wu Ju H. Park Hongye Su Jian Chu 《Journal of The Franklin Institute》2012,349(6):2136-2150
In this paper, the problem of stochastic stability analysis is considered for piecewise homogeneous Markovian jump neural networks with both discrete and distributed delays by use of linear matrix inequality (LMI) method. Based on a Lyapunov functional that accounts for the mixed time-delays, a delay-dependent stability condition is given, which is formulated by LMIs and thus can be easily checked. Some special cases are also investigated. Finally, a numerical example is given to show the validness of the proposed result. 相似文献
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Burgess KB Wojslawowicz JC Rubin KH Rose-Krasnor L Booth-LaForce C 《Child development》2006,77(2):371-383
The primary objectives of this investigation were to examine the attributions, emotional reactions, and coping strategies of shy/withdrawn and aggressive girls and boys and to examine whether such social cognitions differ within the relationship context of friendship. Drawn from a sample of fifth and sixth graders (M age = 10.79 years; SD = .77), 78 shy/withdrawn, 76 aggressive, and 85 control children were presented with hypothetical social situations that first involved unfamiliar peers, and then a mutual good friend. Results revealed group and gender differences and similarities, depending on the relationship context. From our findings emerges a central message: friends' involvement during interpersonal challenges or stressors mitigates children's attributions, emotions, and coping responses. 相似文献
999.
Previous studies have reported, but not explained, the reason for a robust association between reading achievement and antisocial behavior. This association was investigated using the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative 1994-1995 birth cohort of 5- and 7-year-olds. Results showed that the association resulted primarily from environmental factors common to both reading and antisocial behavior and was stronger in boys. Environmental factors also explained the relation between reading disability and conduct disorder. Leading candidate environmental risk factors weakly mediated the association. For boys the best explanation was a reciprocal causation model: poor reading led to antisocial behavior, and vice versa. In contrast, the relation between reading achievement and attention deficit hyperactivity disorder was best explained by common genetic influences. 相似文献
1000.
How golden is silence? Teaching undergraduates the power and limits of RNA interference 总被引:1,自引:1,他引:0
Kuldell NH 《CBE life sciences education》2006,5(3):247-254
It is hard and getting harder to strike a satisfying balance in teaching. Time dedicated to student-generated models or ideas is often sacrificed in an effort to “get through the syllabus.” I describe a series of RNA interference (RNAi) experiments for undergraduate students that simultaneously explores fundamental concepts in gene regulation, develops cutting-edge laboratory skills, and embraces student-directed learning. Students design a small interfering RNA (siRNA) against luciferase, add it to cells expressing this gene, and then quantitatively assess the siRNA's effect on both intended and unintended targets, using a luciferase assay and a DNA microarray. Because both RNAi and microarray technologies are relatively new, with no clear consensus on their analysis or limitations, students are encouraged to explore different approaches to the design of their reagents and interpretations of their data. The ability to creatively formulate a hypothesis-driven experimental approach to a scientific question and to critically evaluate collected data is stressed. Equally important, this experiment emphasizes how modern scientific ideas emerge, are debated, tested, and decided. 相似文献