Asymmetry of red blood cell motions in a microchannel with a diverging and converging bifurcation

In microcirculation, red blood cells (RBCs) flowing through bifurcations may deform considerably due to combination of different phenomena that happen at the micro-scale level, such as: attraction effect, high shear, and extensional stress, all of which may influence the rheological properties and flow behavior of blood. Thus, it is important to investigate in detail the behavior of blood flow occurring at both bifurcations and confluences. In the present paper, by using a micro-PTV system, we investigated the variations of velocity profiles of two working fluids flowing through diverging and converging bifurcations, human red blood cells suspended in dextran 40 with about 14% of hematocrit level (14 Hct) and pure water seeded with fluorescent trace particles. All the measurements were performed in the center plane of rectangular microchannels using a constant flow rate of about 3.0 × 10⁻¹² m³/s. Moreover, the experimental data was compared with numerical results obtained for Newtonian incompressible fluid. The behavior of RBCs was asymmetric at the divergent and convergent side of the geometry, whereas the velocities of tracer particles suspended in pure water were symmetric and well described by numerical simulation. The formation of a red cell-depleted zone immediately downstream of the apex of the converging bifurcation was observed and its effect on velocity profiles of RBCs flow has been investigated. Conversely, a cell-depleted region was not formed around the apex of the diverging bifurcation and as a result the adhesion of RBCs to the wall surface was enhanced in this region.     

Lack of statistical significance

Criticism has been leveled against the use of statistical significance testing (SST) in many disciplines. However, the field of school psychology has been largely devoid of critiques of SST. Inspection of the primary journals in school psychology indicated numerous examples of SST with nonrandom samples and/or samples of convenience. In this article we present an argument against SST and its consequent p values in favor of the use of confidence intervals and effect sizes. Further, we present instances of common errors that impede cumulative knowledge in the literature related to school psychology. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 417–422, 2007.     

中日美三国高中生规范意识调查

2004年9月至12月,日本青少年研究所对中国、日本和美国三个国家的公立高中进行了高中学生规范意识的调查。在中国调查的对象是北京、哈尔滨、重庆等8个城市12所高中的1300名学生;美国调查的是华盛顿等11个州12所高中的1200名学生;日本调查的是北海道、长野、东京、大阪和福冈等11个都道府县11所高中的1320名学生。调查项目包括上课时的态度、补习班的利用、对于包括学习在内的各种活动的参与欲望、与朋友亲属的关系、将来的职业意识和对国旗国歌的意识等。一、关于“学习”对于“是否喜欢上学”的问题,回答“非常喜欢”和“比较喜欢”两项的…     

Solving composite scheduling problems using the hybrid genetic algorithm

This paper dealt with composite scheduling problems which combine manufacturing scheduling problems and/or transportation routing problems.Two scheduling models were formulated as the elements of the composite scheduling model,and the composite model was formulated composing these models with indispensable additional constraints.A hybrid genetic algorithm was developed to solve the composite scheduling problems.An improved representation based on random keys was developed to search permutation space.A genetic algorithm based dynamic programming approach was applied to select resource.The proposed technique and a previous technique are compared by three types of problems.All results indicate that the proposed technique is superior to the previous one.     

科学与竞争:以日本物理学为例,1886-1949

明治中期,日本科学家的研究倾向开始转向理论科学。他们当中的许多人都视纯科学研究为一种智力游戏,任何国家的科学家都可以在其中获得机会,以展示他们自己以及他们所属国家的文化优越性。在日俄战争以前,尽管日本的经济和政治地位都还比较低,但是日本的科学家还是梦想着能够在这场智力游戏中打败欧洲人,以显示他们的智力水平。长冈半太郎的土星原子模型(1903)是举世瞩目的科学成就之一,但是包括布拉格和卢瑟福在内的英国物理学家却因为这个模型出自一个“小日本”之手而对其漠然置之,没有给予适当的评价。量子力学的出现预示着物理研究的新方法即将登场,也预示着日本科学家从此可以与欧洲科学家同台竞争,尤其是在国家工业技术发达程度无甚影响的纯科学研究领域。年轻的物理学家像菊池正士和仁科芳雄才可以在1928年做出一流的成绩来。长期的科学努力最终使得20世纪30年代登上物理舞台的一位日本物理学家获得了诺贝尔奖:1934年,汤川秀树发表了他的介子理论,他对一种新粒子的预言在1937年被Carl AndersonSeth Neddermeyer所证实存在于宇宙射线中,这个发现震惊了西方物理学界。甚至在日本迫切地需要科学家与之合作的二战期间和二战之后,日本的物理学家还是没有放弃自己的追求,奋战在纯科学的战线上。尽管他们当中有些人为诸如原子弹和雷达的研发这样的战时工程出过力,但是他们的主要兴趣还是放在诸如回旋加速器的建造,以及存在缺陷并且与新粒子特征不太相符的介子理论等这样的一些问题上。1947年出访日本的美国国家科学院科学顾问团发现日本科学家这种对理论科学的倾向对日本工业和经济的恢复与重建“毫无裨益”,但是这种倾向即使在战后最困难的时期也没有停止过,1949年汤川秀树获得诺贝尔奖之后则更是不可遏制。