软物质与复杂系统系列学术报告会
时间：2016-01-13 9:00-11:30
地点：机电信息大楼B521
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报告安排：
9:00-9:45 李念北（同济大学）
一维非线性晶格的声子输运：非线性能量载流子，有效声子理论&热流的调控
9:45-10:30 姜玮茵（哈佛大学）
Effect of coupling in complex biological systems
10:30-11:15 王峰（香港科技大学）
Ecological understanding of human gut microbiome
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学术报告摘要
一维非线性晶格的声子输运：非线性能量载流子，有效声子理论&热流的调控
李念北（同济大学）
随着一维非线性系统反常热传导现象的发现，一维系统的能量输运引起了统计物理学领域广泛而深入的研究。我们的研究表明，一维非线性系统的能量载流子不是以前认为的孤子，而是重正化声子。我们通过计算非线性系统的声速，发现随温度变化的声速与重正化声子的理论完全一致，从而证明了重正化声子才是非线性系统的能量载流子。在重正化声子的基础上，我们在假设弛豫时间和非线性强度和重正化频率成反比的基础上，提出了有效声子理论，该理论可以有效的预测系统的热导率随温度的变化关系。通过对大量一维典型的非线性晶格系统的计算，我们发现热导率随温度的变化基本都呈幂率变化，而该幂指数可以由有效声子理论完美的解释。最后我们讨论了关于热流的调控问题，通过引入动态的温度场的调控，破坏系统的空间或者时间对称性，我们可以有效的调节热流的大小和方向，达到利用热流的目的。
演讲人简介
李念北，同济大学物理科学与工程学院/高等研究院特聘研究员，博士生导师，教育部新世纪优秀人才，上海市青年科技启明星（A 类）。北京大学物理系本科、硕士毕业，导师为苏肇冰院士，2007年获新加坡国立大学博士学位，导师李保文教授。2008-2011先后在德国奥格斯堡大学和马普所做博士后，2011年底加盟同济大学物理科学与工程学院/高等研究院,任“领航计划”特聘研究员。发表第一或通讯作者论文17 篇，其中包括物理顶级综述期刊Reviews of Modern Physics 1 篇，物理顶级期刊 Physical Review Letters 1 篇。
Effect of coupling in complex biological systems
姜玮茵（哈佛大学）
Coupling, including molecular regulation network and cell-cell interaction, is the most important component in biological systems, and results into rich complex behaviors. While the complex behaviors in biological systems are intriguing, it is desired to understand the fundamental mechanism behind these observations. Utilizing statistical mechanics, physicists provide the insights from the minimal mathematical models which describe the most essential components in the system to understand these interesting phenomena results from coupling. In this talk, I will briefly mention about the topics that I have done in last five years, then focus on the topics of frequency enhancement and the heatshock response.
In the first part of the talk, I will talk about the phenomenon of non-monotonic changes in beating rate in the cardiac myocyte system, and explain how we can understand this behavior through mathematical simulation and Kramer's escape rate. This brings us more understanding about this biological system, indicating that changes in beating rate is mainly contributed by the dynamical coupling between the cells. The second part of the talk is about heatshock response. Heatshock response(HSR) is one of the conserved self-healing functions found in the living cell. Although the molecular pathway is well studied, it is still not clear how HSR is regulated by neurons or intercellular communications on the system level. The preliminary experimental evidences on C. elegans showed the deactivation of neuron can change the responses to global/local heating. To explain this observation, we construct a simple mathematical model that consists of the most essential components to describe the dynamics of HSR for the single cell, together with the regulation from the neuron(global), adjacent cell(local) and the feedbacks from the peripheral cell to the neuron. We found that the sensitivity of the naive cell to the heat stress is improved by the regulation from neuron/adjacent cell.
演讲人简介
Wei-Yin Chiang obtained her Ph.D. degree from Department of Physics at National Central University in Taiwan in 2012, then she works as a postdoc at Harvard till now. Her postgraduate study focused on the nonlinear dynamics in biological complex systems and she had found the fundamental mechanisms of the phenomena such as frequency enhancement and quorum sensing.Her postdoc training focus on novel data analysis on human and animal studies, mathematical modeling and statistical mechanics in nonequilibrium system. Her current research interests are the multi-scale regulation of heatshock response in C. elegans and the dynamic proof reading process.
Ecological understanding of human gut microbiome
王峰（香港科技大学）
100 billion microbes are living in our human body, especially the gut. Those microbes form huge ecological communities. Recently developed next-generation sequencing technique revealed both the members of those huge communities as well as their strong impact on our human health, e.g. obesity, type-1 diabetes, inflammatory bowel disease, and many mental diseases. However, it remains unknown that how the gut microbiome community changes over time, and what factor affects the community. Those questions are crucial for microbiome-approach therapy, such as fecal microbiota transplant.
In the first part of the talk, I will give a brief introduction on the human gut microbiome, and show how the microbial community looks like from an ecological perspective. Then, by using the generalized Lotka–Volterra (gLV) model and statistical model selection, we found that three-body and high-order interactions among microbes play a minor role in shaping the community, while net-incoming migration may play an ignored but important role, which is further confirmed by sparse model inference of the time-series data. Finally, we employ the gLV model with random pairwise interactions and show that migration shapes the community and gives the rank-abundance distribution commonly observed in experimental data.
演讲人简介
Feng Wang obtained his Ph.D. degree from Department of Physics, Hong Kong University of Science and Technology in 2013. Then he worked as a postdoc in Boston University for two years and moved back to HKUST last year. His postgraduate study focused on the phase transitions in colloidal system, and complex networks. His postdoc study in BU focus on data analysis and modeling of human gut microbiome. His research interests are statistical physics, ecology, stochastic process and machine learning.
