Fluctuations and Response in Active Materials: From Driven Granular Systems to Swarming Bacteria

1115279 PI: O'Hern, Corey s .智力价值：我们为来自美国，欧洲和印度的29名参与者寻求国际旅费支持，以参加2011年6月20日至24日在莱顿大学洛伦兹中心举行的“活性材料的波动和响应：从驱动颗粒系统到群菌”研讨会。研讨会汇集了研究颗粒和活性生物系统的理论、计算和实验科学家。活性物质研究领域的动力来自于有组织的、集体的、群居的、群居的生物动态。活性系统在生物学中大量存在，包括细菌悬浮液、细胞骨架和活组织。这些系统的一个基本特征是主动或自推进粒子的重要作用。最近人们已经认识到，非生命系统，如剪切和振动颗粒材料，表现出与活性系统相似的动力学行为，但不具有机载能量来源。相反，受驱动的颗粒状材料通过与容器边界和其他粒子的碰撞获得和消散能量。各向异性激活的无生命颗粒系统丰富的集体行为与活性物质的时空行为具有惊人的相似性。了解颗粒状和活性生物物质之间的重要异同，并确定在这两种类型的系统中产生集体和紧急行为的物理原理，可能会增强或抑制自然和人工系统中的这些行为。更广泛的影响：研讨会有两个主要目标。首先，我们寻求确定有希望的富有成效的研究方向，这些方向将解决非生命的物理系统（如颗粒介质）和活跃的生命系统共同存在的基本开放问题。已经出现的一些重要问题包括：1)决定大规模行为的活性物质的“普遍”特性是什么；2)对活性生物物质的更好理解能否导致设计策略，以防止颗粒、胶体和其他物理系统中不必要的干扰和玻璃行为；3)生物系统中的生物活性、集体行为和模式形成在多大程度上可以用物理力、反应和波动来解释。第二，我们寻求鼓励科学家在颗粒和活性物质方面进行国际合作，以开发跨学科研究项目来解决这些悬而未决的问题。目前，这两个研究团体是脱节的，几乎没有讨论和思想的交流。如果我们在颗粒状和活跃的生物物质研究小组之间建立强有力的国际和跨学科合作和联系，研讨会将被认为是成功的。作为这次研讨会的结果，我们设想在美国、欧洲和印度的科学家之间就颗粒和活跃媒体开展国际合作。我们已经确认了29位特邀演讲者（美国16位，欧洲13位）和7位组委会成员的参与。受邀演讲者中有5名女性，1名非洲裔演讲者和7名初级教师参与者，占受邀演讲者的近一半。除了受邀的演讲者和组织者外，我们预计至少还有30名参与者。例如，我们将鼓励受邀演讲者从他们的小组中带研究生或博士后到研讨会上展示他们的工作海报或简短的演讲。此外，我们将在洛伦兹中心网站上发布公告，我们将为来自科学和工程领域代表性不足群体的注册参与者提供旅行支持。这些参与者将得到美国物理学会的旅行资助。

1115279 PI: O'Hern, Corey S.Intellectual Merit:We seek support of international travel costs for 29 participants from the US, Europe, and India to attend the Workshop "Fluctuations and Response in Active Materials: From Driven Granular Systems to Swarming Bacteria" at the Lorentz Center, Leiden University June 20-24, 2011. The workshop brings together theoretical, computational, and experimental scientists studying granular and active biological systems. The research field of active matter was motivated by organized, collective dynamics flocking, schooling, and swarming exhibited by living matter. Active systems abound in biology and include bacterial suspensions, cell cytoskeleton, and living tissues. A basic feature of these systems is the important role of active or selfpropelled particles. It has been recognized recently that nonliving systems, such as sheared and vibrated granular materials, display similar dynamical behaviors to those of active systems, but do not possess an on-board energy source. Instead, driven granular materials gain and dissipate energy from collisions with the boundaries of the container and other particles.The rich collective behaviors of anisotropic `activated nonliving granular systems show striking similarities to the spatio-temporal behavior of active matter. Understanding the important similarities and differences between granular and active living matter and identifying the physical principles that give rise to collective and emergent behavior in both types of systems can potentially lead to either enhancing or inhibiting these behaviors in natural and artificial systems.Broader Impact:The Workshop has two primary objectives. First, we seek to identify promising fruitful research directions that will address the fundamental open questions that are common to both nonliving, physical systems such as granular media and active, living systems. Some of the important questions that have emerged include: 1) what are the "universal" properties of active matter that determine large-scale behavior, 2) can an improved understanding of active living matter lead to design strategies to prevent unwanted jamming and glassy behavior in granular, colloidal, and other physics systems, and 3) to what extent can bio-activity, collective behavior, and pattern formation in biological systems be explained by physical forces, response, and fluctuations. Second, we seek to encourage international collaborations among scientists in granular and active matter to develop interdisciplinary research programs to tackle these open questions. At present, the two research communities are disjointed with minimal discussion and cross-fertilization of ideas. The workshop will be considered a success if we establish strong international and interdisciplinary collaborations and linkages among research groups working in granular and active, living matter. As a result of this workshop, we envision developing an international collaboration among scientists in the US, Europe, and India on granular and active media. We have confirmed the participation of 29 invited speakers (16 from the US and 13 from Europe) and 7 members of the organizing committee. Five female invited participants, 1 speaker of African descent, and 7 junior faculty participants comprise nearly half of the invited speakers. In addition to the invited speakers and organizers, we expect at least 30 additional participants. For example, we will encourage the invited speakers to bring graduate students or postdocs from their groups with them to the workshop to present a poster or short talk on their work. In addition, we will post an announcement on the Lorentz Center website that we will offer travel support to registered participants from underrepresented groups in science and engineering. These participants will be supported by travel grants from the American Physical Society.