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機能創成セミナー Seminar on Mechanical Science and Bioengineering
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第224回
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2026年5月28日(木) 16:00-17:20 [May 28th 2026 (Thu.) 16:00-17:20] 基礎工学J棟1階共用セミナー室（J114） |
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| Drop and bubble fragmentation by outer eddies | |
| The fragmentation of drops and bubbles in turbulence determines the rate of many processes in engineering and environmental fluid flows. The nonlinear coupling between interfacial and hydrodynamic stresses poses a fundamental difficulty to model reduction, which we here address by decomposing the flow into outer and inner fields. We show that the outer field is independent of the drop dynamics and drives deformation, whereas the inner field responds to the deformation by dissipating the interfacial energy through the genesis of turbulent eddies. We leverage these results to derive a simple analytical model that reproduces the breakup statistics obtained from large ensembles of direct numerical simulations. Ours results reveal a causal link between the intermittency of turbulent flows and the memoryless breakup of drops. | |
| Marc Avila 教授 （Bremen大学） | |
| 世話人：河原源太 | |
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第223回
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2026年5月21日(木) 12:10-12:55 [May 21st 2026 (Thu.) 12:10-12:55] 基礎工学研究科 機械科学会議室 |
| 機械学習分子動力学計算によるFe–Si–B系アモルファス合金の構造解析 | |
| Fe–Si–B系アモルファス合金は、優れた軟磁性特性を示すため、高効率モーターコア材料として注目される。しかし、アモルファス系では、物性を支配する構造特性の理解は容易ではない。特に、最近接原子による短距離秩序（SRO）および、それらの結合による中距離秩序（MRO）の形成と、それらの材料特性との関係については未解明な点が多い。 本研究では、機械学習ポテンシャルを用いてアモルファス形成シミュレーションを行い、SROおよびMROを解析した。その結果、非金属元素（Si, B）周辺の局所秩序には明確な元素依存性がみられた。すなわち、SiはFeとともにアモルファス相に特徴的な正二十面体クラスタを形成するのに対し、B中心クラスタはFe–B結晶と共通する局所構造を形成しやすい。また、B中心クラスタはネットワーク形性能が高く、より結晶化しやすい可能性が示唆された。 このようなSRO、MROの形成は、力学応答などのマクロな物性を左右する可能性がある。本研究は、アモルファス系の研究における、機械学習を用いた原子シミュレーションの有用性を示すものである。 | |
| 平山 尚美 （未来研究推進センター） | |
| 世話人：出口真次 | |
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第222回
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2026年4月17日(金) 12:30-13:15 [April 17th 2026 (Fri) 12:30-13:15] 基礎工学研究科 国際棟 セミナー室 |
| Bridging Natural Products and Synthetic Chemistry: A Comprehensive Strategy for Drug Discovery and Development | |
| Background: Natural products are a main source for drug discovery due to their structural diversity and biological activity. However, these resources are limited. Therefore, integrating isolation, chemical transformation, and total synthesis is essential for sustainable drug development. For example, compounds from Curcuma heyneana. can be studied for diseases like leishmaniasis or optimized through biotransformation. Similarly, total synthesis enables access to alkaloids such as Pumiliotoxin C, originally from Dendrobates sp. tropical frogs. Objective: This study seeks to investigate the roles of natural product isolation, chemical transformation, and total synthesis of Pumiliotoxin C in supporting the discovery and development of new drug candidates through various in vitro studies, including antileishmanial, anticancer, antioxidant, and other pharmacological activities. Methods: Researchers extracted, fractionated, and isolated natural product compounds, then elucidated their structures using Nuclear Magnetic Resonance (NMR) spectroscopy. To enhance their potential, chemists sometimes chemically convert isolated natural compounds. When natural sources yield insufficient amounts, teams use total synthesis approaches, such as the synthesis of Pumiliotoxin C and its derivatives, to obtain higher yields suitable for pharmaceutical production. Drug discovery and development require teams to maintain strict standardization, conducting in silico studies, in vitro and in vivo experiments, and clinical trials. Results: Original research demonstrates that isolating natural products, such as those from Curcuma species, is vital for developing pharmacological assays. Chemical transformation can modify structures to enhance biological and pharmacokinetic profiles. Total synthesis—applied, for example, to Pumiliotoxin C—provides efficient production and access to novel analogs. Integrating these three approaches accelerates the identification and optimization of drug candidates. Conclusion: The combination of natural product isolation, chemical conversion, and total synthesis represents a thorough strategy in modern drug development. This approach addresses the limitations of natural sources while enabling the exploration of new chemical structures with the potential to become more effective and safer drug candidates. | |
| Melanny Ika Sulistyowaty （Airlangga University） | |
| 世話人：出口真次 | |
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第221回
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2026年4月10日(金) 12:30-13:15 [April 10th 2026 (Fri) 12:30-13:15] 基礎工学研究科 国際棟 セミナー室 |
| Epithelial tube contractions unjam sperm flows into active turbulence in vivo | |
| Sperm mature in the epididymis, a long coiled duct traditionally viewed as a passive conduit that stores sperm and uses smooth muscle contractions to propel them forward. Here we overturn this view by showing that dense sperm suspensions in the epididymal cauda self organize into chaotic collective flows in vivo. Intravital imaging reveals that motile sperm generate mesoscale vortices and jets spanning hundreds of cell lengths, consistent with the phenomenon of active turbulence, a hallmark of dense active matter systems. We further overturn the long standing assumption that contractions merely drive passive transport. When rhythmic contractions are inhibited, collective flows arrest despite preserved single cell motility, and when motility is lost while contractions persist, flows are absent. Only the coexistence of motility and contractions activates large scale flow in an otherwise quiescent suspension. A continuum model with periodically contracting boundaries and shear thinning rheology reproduces this contraction induced flow activation and shows that boundary driven shear lowers the activity threshold for active turbulence. Epithelial contraction induced active turbulence therefore represents a previously unrecognized physical mechanism for sperm transport, arising from the dynamic coupling between tissue mechanics and cellular activity. | |
| Robin Bölsterli （University of Copenhagen） | |
| 世話人：松永大樹 |
