Covalently immobilized biomolecule gradient on hydrogel surface using a gradient generating microfluidic device for a quantitative mesenchymal stem cell study

Precisely controlling the spatial distribution of biomolecules on biomaterial surface is important for directing cellular activities in the controlled cell microenvironment. This paper describes a polydimethylsiloxane (PDMS) gradient-generating microfluidic device to immobilize the gradient of cellular adhesive Arg-Gly-Asp (RGD) peptide on poly (ethylene glycol) (PEG) hydrogel. Hydrogels are formed by exposing the mixture of PEG diacrylate (PEGDA), acryloyl-PEG-RGD, and photo-initiator with ultraviolet light. The microfluidic chip was simulated by a fluid dynamic model for the biomolecule diffusion process and gradient generation. PEG hydrogel covalently immobilized with RGD peptide gradient was fabricated in this microfluidic device by photo-polymerization. Bone marrow derived rat mesenchymal stem cells (MSCs) were then cultured on the surface of RGD gradient PEG hydrogel. Cell adhesion of rat MSCs on PEG hydrogel with various RGD gradients were then qualitatively and quantitatively analyzed by immunostaining method. MSCs cultured on PEG hydrogel surface with RGD gradient showed a grated fashion for cell adhesion and spreading that was proportional to RGD concentration. It was also found that 0.107–0.143 mM was the critical RGD concentration range for MSCs maximum adhesion on PEG hydrogel.     

情感领域的教学设计理论

该介绍了马丁和瑞戈鲁斯对进行情感领域教学必要性的论述,及他们关于情感领域教学设计的基本理论,包括情感领域的概念模型、各个维度的划分依据等。另外还介绍了与此模型相对应的情感发展课程的应用模式。     

The simple view of second language reading throughout the primary grades

In the Simple View of Reading proposed by Hoover and Gough (1990), reading comprehension is conceived as the product of word decoding and listening comprehension. It is claimed that listening comprehension or the linguistic processes involved in the comprehension of oral language strongly constrain the process of reading comprehension. In several studies, evidence for this theoretical framework has been provided for first language learners. In the present study, an attempt was made to find empirical evidence for the same view underlying second language reading. Therefore, the word decoding and listening comprehension skills of samples of 1,293 first language (L1) learners and 394 second language (L2) learners of Dutch were related to their reading comprehension abilities throughout the primary grades. It was found that the levels of word decoding were more or less equal in the two groups of learners, whereas the L2 learners stayed behind their first L1 peers in both listening, and reading comprehension. The relationships between word decoding, listening comprehension and reading comprehension turned out to be highly comparable. A longitudinal analysis of data showed the Simple View of Reading to be equally valid for L1 and L2 learners. With progression of grade, the impact of word decoding on reading comprehension decreased, whereas the impact of listening comprehension showed an increase to the same extent in the two groups of learners. However, the reciprocity of the relationship between listening comprehension and reading comprehension tended to be less prominent in the group of L2 learners.     

MRSQ Informatics Education columns: past, present and future

This is the last Informatics Education column under the current editors. The outgoing editors identify six key themes that reflect the changes in informatics education over their seven-year tenure. The themes are picked from the 29 previous columns published under their editorship. The first and key theme is technology, and this one theme is the basis for the other five. The incoming editors project what they expect to see as key themes for future columns. Together, this column looks at the past, present, and future state of informatics education in the United States.     

功率—力量训练的关键因素

功率是运动员获胜的最基本的要素。打棒球,踢足球,踢英式足球,推铅球,一百码冲刺跑——都需要功率。协调和控制是重要的,但是对于最理想的成绩功率也是必不可少的。甚至长跑也需要功率。虽然在一哩比赛中每个人做功数量相等,但胜者用的时间最短,这就是功率的内在含义。功率由三个因素构成:肌肉力量、力的作用距离和作用时间。功率可以通过以下方面来提高:(1) 增加肌肉的力量;(2)