This award has two broad goals: to study memory in various condensed matter systems and to study the flow of fluids with negligible surface tension. The first project concentrates on memory and memory loss in far-from-equilibrium disordered systems that have been "trained" to have a specific behavior. There may a generic class of memory, that can be seen in such systems, that has unusual properties in that, without noise, the more one trains the system the less it remembers. The project also includes a study of how submerged air bubbles can remember initial conditions through a breakup singularity and an investigation of rejuvenation and memory in aging glassy systems. The second project, on fluids with negligible surface tension, includes a study of fingering instabilities in driven miscible fluids as well as granular jets, where the granular matter can be considered as a fluid. Postdoctoral associates and graduate students will be trained in the study of complex phenomena. Because much of this research deals with macroscopic phenomena, it provides an excellent starting place for bringing undergraduate and high-school students into the laboratory. This research affords excellent outreach to the public. Some of the work has been a focus of museum exhibits at the Museum of Science and Industry in Chicago and the Exploratorium in San Francisco.
This award has two overarching goals: to study the formation of memories and to study fluids with negligible surface tension. The first project concentrates on memory formation in far-from-equilibrium disordered systems. Previous work from this laboratory had uncovered unusual behavior that may be generic. When a system is repeatedly "trained" over an extended period of time, one normally expects that memory retention will improve with repetition. However, in the cases of interest here, the opposite occurs -the more one trains a system, the less it remembers. The project seeks to understand what causes such behavior and the extent to which such behavior can be seen in a variety of materials including biological ones. The second project, on fluids with negligible surface tension, includes a study of fingering instabilities in driven miscible fluids as well as granular jets, where the granular matter can be considered to be a fluid. Both research topics have significant technological implications. Postdoctoral associates and graduate students will be trained in the study of complex phenomena. Because much of this research deals with macroscopic phenomena, it also provides an excellent starting place for bringing undergraduate and high-school students into a research laboratory. Because the phenomena are so accessible, this research affords excellent outreach to the public. This includes museum exhibits at the Museum of Science and Industry in Chicago and the Exploratorium in San Francisco.
Intellectual Merit This work has focused on several related themes dealing with the properties of fluids. We have conducted a comprehensive program to look at dynamic singularities in fluid flows as a drop of fluid changes its shape or topology: either breaking apart, coalescing with another drop or shattering against a surface. We have been able to understand under what conditions a dynamic singularity can produce universal dynamics and in what ways the complex flows inside the drop give rise to novel, unexpected, scaling. We have investigated how liquids splash onto smooth dry substrates. In all the regimes we have investigated, we have found that lowering the pressure of the surrounding air completely suppresses splashing. We have studied how the air can have such a profound effect. In particular, we have measured the geometry of the spreading liquid using interference techniques. We have also studied how surface roughness changes the nature of the splash for more viscous fluids. In another direction, we have investigated how memories are stored and then forgotten in various condensed matter systems. We have studied memory and the loss of memory in disordered systems that have been "trained" to have a specific behavior. We found a generic class of memory that can be seen in a variety of far-from-equilibrium disordered systems. These have unusual properties in that the more one trains the system the less it can remember. However, if there is noise in the environment then the system can retain all the memories indefinitely. Broader Impacts The research in our laboratory, in addition to probing basic scientific questions, has significant impact on technology. For example the work on splashing is important for the engineering community interested in thermal sprays for coating materials. Postdoctoral research associates, and graduate students have been trained by working on the projects outlined above and have seen at first hand how experiment and theory work together to produce a coherent understanding of complex phenomena. Also, because much of this research has dealt with macroscopic phenomena, it has provided an excellent starting place for bringing undergraduate and even high-school students into the laboratory. Because the phenomena are so accessible and aesthetically appealing, this research has afforded an excellent starting point for outreach to the public. Some of the work has become the focus of a number of museum exhibits, including those at the Museum of Science and Industry in Chicago and the Exploratorium in San Francisco.
