Single particle motion of polymeric, colloidal, and biological materials

Small particles and their dynamics are of widespread interest due both to their unique properties and their ubiquity. Here, we investigate several classes of small particles: colloids, polymers, and liposomes. All these particles, due to their size on the order of microns, exhibit significant similarity in that they are large enough to be visualized in microscopes, but small enough to be significantly influenced by thermal (or Brownian) motion. Further, similar optical microscopy and experimental techniques are commonly employed to investigate all these particles. In this work, we develop single particle tracking techniques, which allow thorough characterization of individual particle dynamics, observing many behaviors which would be overlooked by methods which time or ensemble average. The various particle systems are also similar in that frequently, the signal-to-noise ratio represented a significant concern. In many cases, development of image analysis and particle tracking methods optimized to low signal-to-noise was critical to performing experimental observations. The simplest particles studied, in terms of their interaction potentials, were chemically homogeneous (though optically anisotropic) hard-sphere colloids. Using these spheres, we explored the comparatively underdeveloped conjunction of translation and rotation and particle hydrodynamics. Developing off this, the dynamics of clusters of spherical colloids were investigated, exploring how shape anisotropy influences the translation and rotation respectively. Transitioning away from uniform hard-sphere potentials, the interactions of amphiphilic colloidal particles were explored, observing the effects of hydrophilic and hydrophobic interactions upon pattern assembly and inter-particle dynamics. Interaction potentials were altered in a different fashion by working with suspensions of liposomes, which, while homogeneous, introduce the possibility of deformation. Even further degrees of freedom were introduced by observing the interaction of particles and then polymers within polymer suspensions or along lipid tubules. Throughout, while examination of the trajectories revealed that while by some measures, the averaged behaviors accorded with expectation, often closer examination made possible by single particle tracking revealed novel and unexpected phenomena.

Whiteness and news: the interlocking social construction of "realities"

This dissertation examines how mainstream U.S. journalism consistently serves white racial interests and the racial status quo, or what I call white incumbency, despite its push for diversity and its stated aims to improve coverage of nonwhite communities. It is based on an in-depth ethnographic study of two daily newspapers and extensive one-on-one interviews with 61 journalists. I found that although journalists strongly identify with the need for more diverse coverage in newspapers, they emphasize individual and personal stories that avoid recognition of historical racial power imbalances, exhibiting what Ruth Frankenberg calls power-evasive race cognizance. Journalists also demonstrate a number of often contradictory identifications and self-understandings about themselves and their work, such as commitments to diversity and not taking sides, but these conflicts are almost always resolved in favor of white incumbency. Journalistic conventions and practices, such as the watchdog function and its emphasis on public institutions, routinely produce stories that replay and reinforce racial hegemony by portraying nonwhites as problems or people seeking “special privileges.” Also, journalistic repertoires about those conventions and practices avoid interrogations of journalists’ ongoing complicity in the maintenance of white incumbency.