International Research Fellow Awards: Nonlinear Electrokinetic Effects on the Dynamics of Colloidal Particles

国际研究员奖励计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持亚利桑那大学的James C. Baygents博士与澳大利亚悉尼大学的Robert J. Hunter博士进行为期9个月的博士后研究访问。该项目将由国际项目司的美澳项目提供支持。这个项目将致力于描述随着位置和时间变化的外加电场中胶体粒子的动力学。有了适当的粒子动力学理论描述，就可以解释非线性电动力学效应的实验测量结果。电声学是对胶体悬浮液施加交变电场的一种方法。由于大多数胶体粒子是带电的，它们对磁场的反应是前后振荡，频率与外加磁场相同。这就产生了声波，通过测量声波的特性，就有可能获得胶体粒子的详细特征。目前的理论假设，施加的场强很低，粒子的响应是线性的。贝金特博士的研究将扩展这些效应的理论，考虑到如果场强提高到更高的水平会产生的非线性效应。足够高的场应该能够使粒子沿着场的方向定向，这将导致它们对无定向粒子的不同反应。这些附加的信息可以用来获得粒子的电荷和大小，以及它们的宽高比（长度与直径），如果它们是非球形的。* * *

9705810 Baygents The International Research Fellow Awards Program enables U.S. scientists and engineers to conduct three to twenty - four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a nine-month postdoctoral research visit by Dr. James C. Baygents of the University of Arizona to work with Dr. Robert J. Hunter at the University of Sydney in Australia. Support for this project will be provided by the U.S.-Australia Program of the Division of International Programs. This project will work to describe the dynamics of colloidal particles in applied electric fields that vary with position and time. Equipped with a proper theoretical description of the particle dynamics, one can then interpret the results of experimental measurements on nonlinear electrokinetic effects. Electroacoustics is a procedure in which one applies an alternating electric field to a colloidal suspension. Since most colloid particles are electrically charged, they respond to this field by oscillating backwards and forwards at the same frequency as the applied field. This generates a sound wave, and it is by measuring the properties of the sound wave that it is possible to obtain a detailed characterization of the colloid particles. Current theory assumes that the applied field strengths are so low that the particle response is linear. Dr. Baygent's research will extend the theories of these effects to take into account the non-linear effects which would result if the field strength is raised to much higher levels. Sufficiently high fields should be able to orient the particles along the direction of the field and this would cause them to respond differently to an unoriented particle. This added information could be used to obtain the charge and size of the particles as well as their aspect ratio (length to diameter) if they are non-spherical. ***