'13 セミナー日程表

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Time 11/22(Fri.) 10:30-12:00
Place 理学部5号館401号室 (Kyoto Univ. Science Bldg. V, Rm. 401)
Speaker 厚見悠氏
Affiliation 京都大学理学研究科 物理学第一教室 非線形動力学分科(佐々・篠本 研究室)
Title スケールフリーネットワーク上の結合双安定系における相秩序化
Abstract 細胞集団からなる生体組織や、生物の固体群等、多数の要素が集まって集団を形成し、何らかの集団ダイナミクスを生じるような系が、実世界において数多く存在する。このような系を描写できる結合要素系という数理モデルは、反応拡散系等を代表としてよく研究されてきており、様々なパターン形成現象等が明らかにされてきた。近年では、ネットワーク上の結合要素系に関心が集められてきており、各要素の持つ結合の本数 (次数) が重要な役割を果たすことが分かってきている。本発表では、スケールフリーネットワーク上の結合要素系が示す、緩和過程 (定常状態に至る過程) における次数依存性について紹介する。
Time 8/23(Fri.) 10:30-12:00
Place 理学部5号館401号室 (Kyoto Univ. Science Bldg. V, Rm. 401)
Speaker Dr.Yongjun Chen
Affiliation Department of Physics, Shaoxing University, China
Title Precipitation Pattern Through Evaporation: Bifurcation and Coexitence of Target and Spiral pattern
Abstract In this seminar, I will demonstrate precipitation pattern from evaporation of a confined liquid bridge containing nonvolatile solute. The target and spiral modesof the pattern were found. The pattern morphologies depends on concentration of solution, temperature, and level of vacuum. The probability of emergence of target pattern is relatively low in contrast to that of spiral pattern. We interpret the pattern formation as propagation of rupture of the precursor liquid thin film along pinned contact line. The symmetry breaking due to evaporation induces the spiral formation, which can choose clockwise and counterclockwise directions.
Time 8/9(Fri.) 13:30-15:00
Place 理学部5号館401号室 (Kyoto Univ. Science Bldg. V, Rm. 401)
Speaker Ms. A. Burk
Affiliation iCeMS Kyoto University
Title Quantification of Relative Significance of Adhesion Molecules in Maintenance of Hematopoietic Stem Cell Niche Functions in Bone Marrow
Abstract A major challenge in understanding the mobilization/immobilization mechanisms of hematopoietic stem cells (HSC) is to characterize the complex interplays of HSC-niche interactions in bone marrow, such as homophilic interactions between N-cadherin and heterogeneous interactions mediated by the CXCR4/SDF1α and CD44/hyaluronic acid axes. The main focus of this project is to design well defined niche models to quantify the relative significance of adhesion molecules (N-cadherin, CXCR4 and CD44). As the model of mesenchymal stromal cell surfaces, we fabricated planar lipid membranes on solid substrates (supported membranes) displaying recombinant N-cadherin, human SDF1α, and hyaluronic acid oligomers at defined surface densities. The control of the self assembly enables us to regulate the intermolecular distance within nm accuracy. After confirming the quantitative functionalization of membranes using various surface sensitive techniques like high energy specular X-ray reflectivity, spectroscopic ellipsometry and dual polarization interferometry, the area of tight adhesion between HSC isolated from umbilical cord blood (CD34+) and supported membranes was measured using label-free, live cell imaging with micro-interferometry (reflection interference contrast microscopy, RICM). Despite of heterogeneity of HSCs, we observed a clear tendency that HSC is very sensitive to a small change in the lateral density of N-cadherin and SDF-1α molecules. To evaluate the strength of cell adhesion, we developed a new technique utilizing pressure waves induced by a picosecond laser pulse (Yoshikawa, et al. JACS, 2011). This non-invasive method enables us to determine the critical force/pressure for the detachment of adherent HSC with reliable statistics. These quantitative results can be used to draw a “phase diagram” of HSC (strength of adhesion vs. lateral distance between adhesion molecules), which can also be used to gain the relative significance of different adhesion pairs in the bone marrow niche.
Time 6/7(Fri.) 10:30-12:00
Place 理学部5号館401号室 (Kyoto Univ. Science Bldg. V, Rm. 401)
Speaker Dr. F. Rossetti
Affiliation iCeMS Kyoto University
Title Cell membrane models as a substrate for culturing neuronal cells and living tissue sheets.
Abstract Biological membranes are key components of all living systems, forming the outer boundary of living cells. They consist largely of a lipid bilayer that imparts a fluid character. Planar lipid membranes on solid substrates are widely used cell-surface models can readily be functionalized by incorporating ‘anchor’ molecules for engineered proteins and can be investigated in a quantitative manner, for example using pressure wave assays or time reflection interference microscopy (RICM). In this talk, two examples of this approach will be presented. First, pluripotent tissue sheets (animal caps isolated from Xenopus laevis blastula stage embryos) were immobilized on supported membranes functionalize with the cell adhesion molecule cadherin-11. The adhesion of cells within the cohesive tissue and the viability and sustainability of the culture over several hours were investigated. In the second project, we aim to quantify orchestrated cytoskeletal dynamics during migration and process formation in developing neurons in the mammalian brain using supported membranes exposing functional molecules organized in different patterns.
Time 5/24(Fri.) 10:30-12:00
Place 理学部5号館401号室 (Kyoto Univ. Science Bldg. V, Rm. 401)
Speaker 齋藤拓也氏
Affiliation 福井謙一記念研究センター
Title 微細孔を通り抜ける高分子鎖のダイナミクス
Abstract DNA高分子鎖をはじめとする巨大高分子は、それら分子鎖の直径程度(~nm)の小さな穴を通り抜けることが出来ます。この現象はtranslocationと呼ばれ、核膜により隔てられた細胞膜-細胞質間の物質輸送や、電気穿孔法(electroporation)などを用いた遺伝子導入において本質的に関与した重要な過程であると考えられています。通常、translocationは、穴付近での電位差や、化学ポテンシャル勾配により駆動される能動的な輸送過程です。溶液中の高分子鎖はランダムコイル形状をとっていますが、直観的 にも明らかなように、この状態に、突然の局所的な駆動力が働いても即座に鎖全体は応答しません。鎖に沿った張力の伝播とともに動き出していきます。本セミナーは、張力伝播のメカニズムをもとにして、高分子鎖の通り抜け時間のスケーリングについてや、その伝播経路の確率性などについてお話しします。



京都大学大学院 理学研究科  物理学第一教室 

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