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。在研究富氢生物和聚合物材料、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有着明确的作用。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拥挤的水环境中出现的分子运输的基本问题。该项目将联合收割机这些研究活动与创建一个教学模块内的质量传输过程中的化学工程师使用中子散射，以证明在简单的液体扩散的分子起源;沿着一个新的本科课程的发展集中在“大规模科学”。在美国，绝大多数的中子科学都是在大型设施中进行的，这巩固了一些科学只需要共享国家设施的概念。中子源是重要的国家投资，“大规模科学”类将侧重于中子散射设施和其他大型科学设施是如何来的，他们完成了什么，他们如何操作，最后，他们如何融入国家和国际科学景观。学生将参观国家设施和代表领导人，以了解更多关于大规模科学的过程和优先事项。分子拥挤的环境是结构复杂和动态的。通过扩散的分子输运经常被观察到在这些环境中变得异常。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。溶质可以被捕获任意长的停留时间，表现出高度相关的弛豫时间，和/或耦合动力学的本地溶剂。中子提供了独特的策略，以探测这些问题时，结合对比度匹配和散射截面操纵策略。选择性氘化是该项目中子散射实验的使能方法。氘将以几种方式部署，以突出溶质分子在拥挤环境中的运动，就好像它是稀溶液中的单个粒子。这将分离出单个分子对异常扩散的贡献。然后可以将其与溶剂或其他介质（例如水凝胶）的局部弛豫进行比较，以将局部流体动力学效应与集体效应相分离。相同系统的结构特征将告知我们对系统遍历性的理论理解，违反遍历性，通过更好地理解现有模型核心假设的结构和动力学分布中的缺陷，可以解释一些异常现象。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准。

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.