Elasto-inertial particle focusing under the viscoelastic flow of DNA solution in a square channel

Particle focusing is an essential step in a wide range of applications such as cell counting and sorting. Recently, viscoelastic particle focusing, which exploits the spatially non-uniform viscoelastic properties of a polymer solution under Poiseuille flow, has attracted much attention because the particles are focused along the channel centerline without any external force. Lateral particle migration in polymer solutions in square channels has been studied due to its practical importance in lab-on-a-chip applications. However, there are still many questions about how the rheological properties of the medium alter the equilibrium particle positions and about the flow rate ranges for particle focusing. In this study, we investigated lateral particle migration in a viscoelastic flow of DNA solution in a square microchannel. The elastic property is relevant due to the long relaxation time of a DNA molecule, even when the DNA concentration is extremely low. Further, the shear viscosity of the solution is essentially constant irrespective of shear rate. Our current results demonstrate that the particles migrate toward the channel centerline and the four corners of a square channel in the dilute DNA solution when the inertia is negligible (elasticity-dominant flow). As the flow rate increases, the multiple equilibrium particle positions are reduced to a single file along the channel centerline, due to the elasto-inertial particle focusing mechanism. The current results support that elasto-inertial particle focusing mechanism is a universal phenomenon in a viscoelastic fluid with constant shear viscosity (Boger fluid). Also, the effective flow rate ranges for three-dimensional particle focusing in the DNA solution were significantly higher and wider than those for the previous synthetic polymer solution case, which facilitates high throughput analysis of particulate systems. In addition, we demonstrated that the DNA solution can be applied to focus a wide range of particle sizes in a single channel and also align red blood cells without any significant deformation.     

四川省奶业发展现状及发展战略研究

本文简要论述了加快我国奶业发展背景,入世对我国奶业的影响,以及四川发展奶业的重要性与必要性。重点阐述了四川奶业现状与特点,在此基础上,作者提出了发展四川奶业的思路与对策。     

铃兰族(广义)花粉形态与叶表皮特征的研究

对铃兰族(广义)7个属分别作了花粉(17种)扫描电镜观察和叶表皮(12种)的光学显微镜和 扫描电镜观察。花粉可分为8个类型。在狭义的铃兰族的4个属内，花粉全为远极单槽，舟状。它们 的外壁除夏须草属外，都具细孔。夏须草属的花粉外壁则为细皱。  Hutchinson(1934)的蜘蛛抱蛋族 花粉形态变异很大，其中开口箭属和万年青属的花粉为远极单槽，舟形，外壁具穿孔或网纹，而蜘蛛抱 蛋属的花粉则为球状，无萌发孔。其间的显著差异支持Nakai为前两个属建立万年青族(Rohdeae)。 表1归纳了7个属的花粉形态；图1是我们对铃兰族(广义)花粉形态演化的见解。叶表皮观察表明，气 孔器为无规则型，上表皮角质层主要为条纹加厚，或均匀加厚，而铃兰属的角质层秕糠状加厚。7个属的叶表皮特征归纳于表2。     

我国科技人员自引现象分析

0引言 自引现象是科学著文过程中比较普遍的现象,R.Tagliacozzo和A.Dimitroff分别于1977年和1995年研究了自然科学文献和图书情报学文献的自引现象[1,2].Tagliacozzo的研究表明植物生理学论文自引率为16.6%,神经生理学论文的自引率为17.5%,并且发现自引引文"年龄更青".他认为自引现象与合著者多少、著文作者的文献书目内容多少或论文量是无关的.     

用户参与式设计模式下美国高校图书馆的实践研究及启示

图书馆用户作为多角色共同体,其需求具有相当的复杂性和不确定性,而图书馆的用户参与式设计活动,则有助于真正实现图书馆服务的个性化与多元化,推动图书馆服务的变革创新。基于文献调研,探索了PD理论的内涵以及其与UCD理论的共同点和差异性,将图书馆用户参与式设计的主要内容归纳为空间、服务两大方面,并总结了用户参与式设计的方法。通过对美国高校图书馆在用户参与式设计实践中取得的阶段性成果进行分析,以期为我国图书馆界开展用户参与式设计活动提供思路与借鉴。     

电子商务平台数据质量控制系统及仿真模型分析

本文在系统动力学的基本原理基础上,构建了电子商务平台数据质量控制系统的因果关系图,利用VENSIM PLE仿真软件进行系统仿真,从有效性和灵敏性两方面验证了技术进步率及管理因素对电子商务平台数据质量的影响。结果表明,该模型能够较好的拟合现实中技术进步率及管理因素与电子商务平台数据质量的相互关系,并且为电商平台数据质量建设管理提供了相应的参考依据。     

芍药属的研究(1)——国产几个野生种核型的报道

In the present paper 8 species with 15 populations of the genus Paeonia L. (if P. papaveracea and P. japonica are recognised as species) were collected from Sichuan, Shaanxi and Hebei provinces (see the Appendix for detail of the materials).  The micrographs of their somatic metaphase (also Mii in the case of P.veitchii) are shown in Plates 1-4, the karyo- type formulae, ranges of chromosome length and classification of karyotypes according to Steb- bins (1971) are shown in Table 5: the idiograms in Figs. 1-2, and the parameters of chromo- somes in Table 1-4.  The essential points are mentioned as follows:        (1)   Chromosomes of the various species in the section Modan have so far been examined and they are all diploid, the two species in the section Onaepia are also diploid, and thus tetraploids exist only in the section Paeonia.        (2)  Chromosomes in the genus Paeonia are relatively stable except for the differentiation of ploidy.  The karyotypes (Table 1-4) show no differences among different taxa in Sect. Modan and the same can also be said about the taxa in Sect. Paeonia (Table 1).  Not only are the karyotypes very similar, but also among the members within  either section have the same parameters of chromosomes, and, differences, if occur, are not statistically significant. Between the two sections, however, the situation is different. The arm ratios of the first pairs of chromosomes in Sect. Modan are 1.53, 1.52 and 1.48 (Table 1), but those in Sect. Paeonia are 1.12-1.28 (Table 2-4), 95% confidence limits are 1.46-1.60 for the section Modan and 1.07-1.28 (1.21-1.35 only for PB85078) for the section Paeonia, not overlapping, which indi- cates that the two sections have differentiated in respect of the first pairs of chromosomes.        (3)The population PB85024, which belongs to the P. obovata complex, has a karyotype of 2B (stebbins, 1971), which is a new one in the genus Paeonia. This karyotype is a stable one, for several individuals in the population are uniform in this respect, which shows that Steb- bins’ (1971) generalization that all the species in Paeonia have 2A does not hold true.        (4)  Three populations of P. obovata complex studied in this work from Sichuan and Shaanxi are all tetraploids, and one from Hebei is a diploid.  From the present work and the previcus reports, the materials from Japan and Korea, no matter whether flowers are pink or white, are diploids, those from Heilongjiang Province (with both pink and white flowers) (Liu Ming-yuan, personal communication) and from Heibei Province (with pink flowers) in China are also diploids, the one from Sakhalin (pink flowers) is tetraploid, those from Priamur of the Soviet Union are a tetraploid (with white flowers) and a diploid (with pink flowers), and those from Shaanxi (the Qinling Range) and western Sichuan (with both pink and white flowers) are all tetraploids.  As far as we have now known, ploidy in this parti- cular complex is correlated with the geographical distribution: diploids are found in the cen- tral part, tetraploids occur in the northern limits, and in the south  letraploids are the only cytotype.      (5)  The materials of P. mairei from western Sichuan and Shaanxi (the Qinling Range) are found all to be tetraploids, which shows that two cytotypes, diploid and tetraploid, exist in this  species,  but the geographical distribution pattern of these two cytotypes is to be revealed in the future investigation.     

港台高校人文社会科学研究现状比较——基于文献被SSCI、A＆HCI收录情况的定量分析

通过对港台高校学者发表的文献被SSCI和A＆HCI的收录情况的定量分析，客观揭示港台高校人文社会科学研究的现状，为增进内地与港台高校学者之间的了解，促进相互之间的合作与交流，提供必要的基础。     

采莓与搜索:随性休闲搜索行为特征研究

[目的/意义]随性休闲搜索具有与工作任务情境下以结果为导向的搜索行为不同的规律，探索休闲情境中的搜索行为特征对于信息系统功能的优化，从而为用户日常信息搜索提供更有效的支持具有重要的意义。[方法/过程]论文以采莓模型为基础，采用基于观察实验的日记研究法，招募23位实验参与者进行了为期一周的视频搜索实验，通过文本分析和数据建模，从查询变化、思考、信息/文档、结束4个方面分析了随性休闲搜索行为的特征。[结果/结论]随性休闲搜索中用户需求及其变化带来了查询改变；用户对信息保持着开放选择，从自身情感体验进行搜索评价。随性休闲搜索是一个顺其自然的信息接受和利用过程，也是一项带来快乐体验的休闲活动。     

建设创新型国家:历史性的跨越——学习胡锦涛在全国科技大会上的重要讲话

文章论述了我国国家创新体系建设的历史过程、总体目标和十六字方针;作者认为从建设国家创新体系到建设创新型国家,是历史性的跨越。