Towards a Better Prediction of Cell Settling on Nanostructure Arrays—Simple Means to Complicated Ends

Vertical arrays of nanostructures (NSs) are emerging as promising platforms for probing and manipulating live mammalian cells. The broad range of applications requires different types of interfaces, but cell settling on NS arrays is not yet fully controlled and understood. Cells are both seen to deform completely into NS arrays and to stay suspended like tiny fakirs, which have hitherto been explained with differences in NS spacing or density. Here, a better understanding of this phenomenon is provided by using a model that takes into account the extreme membrane deformation needed for a cell to settle into a NS array. It is shown that, in addition to the NS density, cell settling depends strongly on the dimensions of the single NS, and that the settling can be predicted for a given NS array geometry. The predictive power of the model is confirmed by experiments and good agreement with cases from the literature. Furthermore, the influence of cell‐related parameters is evaluated theoretically and a generic method of tuning cell settling through surface coating is demonstrated experimentally. These findings allow a more rational design of NS arrays for the numerous exciting biological applications where the mode of cell settling is crucial.     

一种新的SDH开销处理方法

文章提出了一种较为实用的SDH系统方案，并在系统中采用了一种新型的、便于系统升级的开销处理方法，该系统已通过了电路实现和硬件的测试，     

Patterning of the chick forebrain anlage by the prechordal plate

We analysed the role of the prechordal plate in forebrain development of chick embryos in vivo. After transplantation to uncommitted ectoderm a prechordal plate induces an ectopic, dorsoventrally patterned, forebrain-like vesicle. Grafting laterally under the anterior neural plate causes ventralization of the lateral side of the forebrain, as indicated by a second expression domain of the homeobox gene NKX2.1. Such a lateral ventralization cannot be induced by the secreted factor Sonic Hedgehog alone, as this is only able to distort the ventral forebrain medially. Removal of the prechordal plate does not reduce the rostrocaudal extent of the anterior neural tube, but leads to significant narrowing and cyclopia. Excision of the head process results in the caudal expansion of the NKX2.1 expression in the ventral part of the anterior neural tube, while PAX6 expression in the dorsal part remains unchanged. We suggest that there are three essential steps in early forebrain patterning, which culminate in the ventralization of the forebrain. First, anterior neuralization occurs at the primitive streak stage, when BMP-4-antagonizing factors emanate from the node and spread in a planar fashion to induce anterior neural ectoderm. Second, the anterior translocation of organizer-derived cells shifts the source of neuralizing factors anteriorly, where the relative concentration of BMP-4-antagonists is thus elevated, and the medial part of the prospective forebrain becomes competent to respond to ventralizing factors. Third, the forebrain anlage is ventralized by signals including Sonic Hedgehog, thereby creating a new identity, the prospective hypothalamus, which splits the eye anlage into two lateral domains.     

Kinetic analysis of the coding properties of O6-methylguanine in DNA: the crucial role of the conformation of the phosphodiester bond

Production by N-nitroso compounds of O6-alkylguanine (O6-alkylG) in DNA directs the misincorporation of thymine during DNA replication, leading to G:C to A:T transition mutations, despite the fact that DNA containing O6-alkylG:T base pairs is less stable than that containing O6-alkylG:C pairs. We have examined the kinetics of incorporation by Klenow fragment (KF) of Escherichia coli DNA polymerase I of thymine (T) and of cytosine (C) opposite O6-MeG in the template DNA strand. Both T and C were incorporated opposite O6-MeG much slower than nucleotides forming regular A:T or G:C base pairs. Using various concentrations of dTTP, dCTP, or their phosphorothioate (Sp)-dNTP alpha S analogues, or a mixture of dTTP and dCTP, the progress of incorporation of a single nucleotide in a single catalytic cycle of a preformed KF-DNA complex was measured (pre-steady-state kinetics). The results were consistent with the kinetic scheme (Kuchta, R. D., Benkovic, P., & Benkovic, S. J. (1988) Biochemistry 27, 6716-6725): (1) binding of dNTP to polymerase-DNA; (2) conformational change in polymerase; (3) formation of phosphodiester between the dNTP and the 3'-OH of the primer; (4) conformational change of polymerase; (5) release of pyrophosphate. The results were analyzed mathematically to identify the steps at which the rate constants differ significantly between the incorporation of T and C. The only significant difference was the 5-fold difference in the rates of formation of the phosphodiester bond (for dTTP, kforward = 3.9 s-1 and kback = 1.9 s-1; for dCTP, kforward = 0.7 s-1 and kback = 0.9 s-1). These pre-steady-state progress curves were biphasic with a rapid initial burst followed by an apparently steady-state rise. Deconvolution of these curves gave direct evidence for the importance of the conformational change after polymerization by showing that the curves represented the sum of the rapid accumulation of the product of step 3 followed by the slow conversion of that to the product of step 5 (because of the rapidity of the release of pyrophosphate there was no significant accumulation of the product of step 4). The equilibrium constants for each step suggest that the greatest change in the Gibbs free energy occurs at the conformational change after polymerization and that while the formation of the phosphodiester bond to T is slightly exothermic, that to C is slightly endothermic.(ABSTRACT TRUNCATED AT 400 WORDS)     

PIMS在企业生产经营中的应用

介绍PIMS在企业生产经营中的应用 ,运用PIMS可对炼油化工企业进行原油采购决策、加工保本点预算、效益预测、物流分配、整体流程优化、投资分析、瓶颈制约因素探讨、原料和产品库存管理、经济活动分析等 ,并结合生产装置特点和市场环境影响因素 ,获取最大生产经营效益。根据影子价格 ,找出提高效益的潜力 ,确定产品、中间产品或半成品合理价格 ,规范关联交易 ,增强企业市场应变能力 ,提高经济效益与管理水平。     

RSView32软件平台的应用及扩展

概述了RSView32工控软件的特点和使用方法 ,并通过贵溪冶炼厂的一个液位自动控制系统的人机界面设计说明了如何在控制系统中使用RSView32软件。文章特别介绍了如何用VBA程序设计来扩展其功能     

钻井液用BDY-1便携式堵漏仪

在堵漏过程中，对堵漏材料和堵漏浆配方的优选是决定堵漏成功的关键。为了能在现场对堵漏进行评价，研制出BDY－1便携式堵漏仪，该堵漏仪主要由不锈钢钢柱圈钢，压力表等加工而成，该堵漏仪体积小，重量轻，价格低，仅为国产堵漏仪的1／20。试验结果表明BDY－1便携式堵漏仪操作简便，可快速对堵漏材料进行评价并筛选出堵漏配方；数据重复性好，准确可靠，能达到进口或国产堵漏仪的水平；在模拟漏层选定后，可采用多套压力梯度，对堵漏浆封堵效果进行评价，在压力梯度选定后，可评价堵漏浆对不同类型漏层的封堵效果；如果扩大压力范围，可对封堵后的漏层进行破裂试验，从而确定合理的钻井施工参数；适用现场操作和应用。     

2.0 Mt/a渣油加氢脱硫装置新氢压缩机性能标定

介绍了中国石化茂名分公司 2 .0Mt/a渣油加氢脱硫装置中的 4M80 30 /2 2 2 0 0 BX型新氢压缩机的特点、技术特征及标定情况。采用国际通用标准对压缩机气体组成、容积流量、轴功率、进排气压力和进排气温度等指标进行了测定。标定表明 ,该机组设计方案合理 ,运转平稳 ,性能指标达到设计要求 ,较好的满足了工艺操作的需要     

台北凹陷小草湖次凹油气成藏特点及有利区带

吐哈盆地小草湖次凹发育多套烃源岩，油源条件好，油气资源丰富，油气勘探潜力巨大，中侏罗统发育三套储盖组合，凹陷内油气藏类型主要为侏罗系三间房组，七克台组的构造－岩性复合型和侏罗系西山窑组的深盆气藏，燕山运动末期是小草湖次凹一次重要的成藏期，古构造，古构造背景和构造－岩性复合型圈闭发育是小草湖次凹成藏主控因素，根据小草湖次凹成藏主控因素评价和优选有利区带，勘探工作取得了良好效果。     

峡口水库沥青混凝土面板的施工与试验

以灌溉、防洪为主的峡口水库大坝，为沥青混凝土面板堆石坝，为研究低温抗裂性能，对沥青混凝土面板破损取样，进行了配比和多种力学性能试验，并与原面板设计指标进行了对比。由于面板经受住了－20℃以下的低温考验，其所用沥青指标、破损取样试验结果，特别是冻断低温指标，对确定水工沥青混凝土低温抗裂检验标准有重要参考价值。