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Experiments of Dissipative Systems with Many Degrees of Freedom (from the view point of nonlinear dynamics and fluctuations)

多自由度耗散系统实验（从非线性动力学和涨落的角度）

基本信息

批准号：
11440119
负责人：
SANO Masaki
金额：
$ 9.66万
依托单位：
University of Tokyo (2000)Tohoku University (1999)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We selected two prototype experimental systems from dissipative systems with many degrees of freedom. One is the experiment of fully developed thermal turbulence. The other is an experiment on networks of cultured neural cells.In the first study, thermal turbulence, we developed Rayleigh-Benard convection cell that enables us to explore one of the highest Reynolds numbers in turbulent free convection by using mercury, a low Prandtl number (Pr) fluid. We attained 10^<11> in Rayleigh number (Ra) and 5x10^5 in Reynolds number for the low Prandtl number fluid (Pr=0.024), and found that two boundary layers are inverted unlike with other fluids (Pr>=1). The scaling exponent of Nusselt number with Ra was 0.29+-0.01, which is close to that of hard turbulence. Two boundary layers match and shrink with the scaling exponent close to -0.29. Therefore theoretically predicted ultimate scaling, 1/2, did not observed even the two boundary layers have crossed. This leads a conjecture that the ultimate scaling regime may not exist.In the second study, we made dissociated culture of brain cells, which are dissected from cortex of rat embryo (E17). Neuron and glia cells grow on the glass plate and develop highly connected network structures. By using Ca^<2+> sensitive fluorescent dye, Ca^<2+> activities of a few hundreds of cells were optically measured simultaneously. We found synchronous bursting Ca^<2+> oscillation in the networks, and classified collective dynamical behavior. Connectivity and structure of the network were evaluated by using monochronal antibody staining. Evolution of distribution function of correlation coefficients between neuron-neuron, neuron-glia, and glia-glia, was firstly quantified to characterize the developmental process of the networks.

我们从多自由度耗散系统中选取了两个原型实验系统。一个是充分发展的热湍流实验。另一个是关于培养神经细胞网络的实验。在第一个研究中，我们开发了Rayleigh-Benard对流室，使我们能够使用低普朗特数(Pr)的水银来探索湍流自由对流中最高的雷诺数之一。对于低Prandtl数流体(Pr=0.024)，瑞利数(Ra)为10^&lt；11&gt；，雷诺数为5×10~(-5)，发现两个边界层与其它流体不同(Pr&gt；=1)。Nusselt数与Ra的标度指数为0.29±-0.01，接近于硬湍流的标度指数。两个边界层匹配并收缩，标度指数接近-0.29。因此，理论上预测的极限尺度1/2甚至没有观察到两个边界层已经交叉。这导致了一个猜测，即最终的伸缩机制可能不存在。在第二项研究中，我们进行了脑细胞的分离培养，这些细胞是从大鼠胚胎(E17)的皮质中分离出来的。神经元和神经胶质细胞生长在玻璃板上，形成高度相连的网络结构。用敏感的荧光染料同时光学测定了数百个细胞的Ca~(2+)&gt；我们在网络中发现了同步爆发的Ca^&lt；2+&gt；振荡，并对集体动力学行为进行了分类。用单核细胞抗体染色评价网络的连通性和结构。首次量化了神经元-神经元、神经元-胶质细胞和神经胶质细胞之间相关系数的分布函数的演化，以表征网络的发展过程。