As the fundamental packing units of DNA in eukaryotes, nucleosomes play a central role in governing DNA accessibility in a variety of cellular processes. Our understanding of the mechanisms underlying this complex regulation has been aided by unique structural and dynamic perspectives offered by single molecule techniques. Recent years have witnessed remarkable advances achieved using these techniques, including the generation of a detailed histone-DNA energy landscape, elucidation of nucleosome disassembly processes, and real-time monitoring of molecular motors interacting with nucleosomes. These and other highlights of single molecule nucleosome studies will be discussed in this review.

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Carbon nanotube pillar arrays (CPAs) for cold field emission applications were grown directly on polished 70∕30at.% NiCr alloy surfaces patterned by photolithography. A carbon nanotube (CNT) pillar is a localized, vertically aligned, and well-ordered group of multiwalled CNTs resulting from van der Waals forces within high-density CNT growth. The edge effect, in which the applied electric field is enhanced along the edge of each pillar, is primarily responsible for the excellent emission properties of CPAs. We achieved efficient emission with turn-on fields as low as 0.9V∕μm and stable current densities as high as 10mA∕cm2 at an applied macroscopic field of 5.7V∕μm. We investigated the effects of pillar aspect ratio, density, and spacing on CPA field emission and quantified the edge effect with respect to pillar aspect ratio through modeling. We also investigated the field emission stability and found substantial improvement with CPAs compared to continuous and patterned CNT films.