CAREER: Standing Out in a Crowd, Neutron Based Methods to Study Molecular

中子散射是一种强大而优雅的实验技术。在研究富含氢的生物和聚合物材料、磁性、成像和探索物质的奇异状态方面至关重要；中子在国家科学剧目中具有明显的作用。该项目将开发新的中子散射实验-利用中子的独特优势来解决从拥挤的水环境中出现的分子传输中的基本问题。该项目将结合这些研究活动，在化学工程师使用中子散射的质量传输课程中创建一个教学模块，以演示简单液体中扩散的分子起源；同时开发一门新的本科课程，重点放在“大范围科学”上。美国绝大多数的中子科学都是在大型设施中进行的，这巩固了这样一个概念，即一些科学只是需要共享国家设施。中子源是重要的国家投资，“大规模科学”课程将重点介绍中子散射设施和其他大型科学设施是如何形成的，它们实现了什么，它们是如何运作的，最后是它们如何适应国家和国际科学格局。学生们将参观国家设施和有代表性的领导人，以了解更多关于大科学的过程和优先事项。分子拥挤的环境在结构上是复杂的和动态的。在这些环境中，通过扩散的分子传输经常被观察到变得异常。这意味着均方位移(MSD)表现出比典型的布朗扩散机制更弱的时间依赖性。溶质可能会被捕获任意长的停留时间，表现出高度相关的松弛时间，和/或与局部溶剂的耦合动力学。当与对比度匹配和散射截面操纵策略相结合时，中子提供了探索此类问题的独特策略。在这个项目中，选择性氚是进行中子散射实验的有效方法。为了突出在拥挤的环境中的溶质分子的运动，我们将采用多种方式来展开，就好像它是稀溶液中的单个粒子一样。这将隔离单分子对反常扩散的贡献。然后可以将这与溶剂或其他介质(如水凝胶)的局部松弛进行比较，以分离局部流体动力效应与集体效应。相同系统的结构特征将有助于我们从理论上理解系统的遍历性，系统的违规行为可以通过更好地理解现有模型核心假设的结构和动态分布中的缺陷来解释一些异常现象。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Neutron scattering is a powerful and elegant experimental technique. Vital in studying hydrogen-rich biological and polymeric materials, magnetism, imaging, and exploring exotic states of matter; neutrons have clear role in the national scientific repertoire. This project will develop novel neutron scattering experiments – leveraging the unique advantages of neutrons to address fundamental questions in molecular transport emerging from crowded aqueous environments. This project will combine these research activities with the creation of a teaching module within the mass transport course for chemical engineers using neutron scattering to demonstrate the molecular origins of diffusion in simple liquids; along with the development of a new undergraduate course focused on "Large Scale Science". The overwhelming majority of neutron science in the US is conducted at large facilities, cementing the notion that some science simply requires shared national facilities. Neutron sources are significant national investments, the "Large Scale Science" class will focus on how neutron scattering facilities and other large scale scientific facilities come to be, what they accomplish, how they operate, and finally, how they fit into the national and international scientific landscape. Students will visit national facilities and representative leaders to learn more about the process and priorities of large-scale science. Molecularly crowded environments are structurally complex and dynamic. Molecular transport via diffusion is often observed to become anomalous within these environments. This means that the mean square displacement (MSD) exhibits a weaker time dependence than the typical Brownian diffusion mechanism. Solutes may become trapped for arbitrarily long residence times, demonstrate highly correlated relaxation times, and/or coupled dynamics to the local solvent. Neutrons offer unique strategies to probe such questions when combined with contrast matching and scattering cross-section manipulation strategies. Selective deuteration is the enabling methodology for neutron scattering experiments in this project. Deuteration will be deployed in several ways to highlight the solute molecule motions in crowded environment as if it were a single particle in dilute solution. This will isolate the single molecule contribution to anomalous diffusion. This can be compared then to the local relaxations of the solvent or other medium, such as a hydrogel, to isolate localized hydrodynamic effects versus collective effects. Structural characterizations of the same systems will inform our theoretical understanding of the ergodicity of the system, the violations of which, can explain some of the anomalous phenomena through better understanding of the flaws in the assumed structural and dynamical distributions at the heart of existing models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.