Pendeoepitaxy, a form of selective lateral growth of GaN thin films has been developed using GaN/AlN/6H-SiC͑0001͒ substrates and produced by organometallic vapor phase epitaxy. Selective lateral growth is forced to initiate from the (112 0) GaN sidewalls of etched GaN seed forms by incorporating a silicon nitride seed mask and employing the SiC substrate as a pseudomask. Coalescence over and between the seed forms was achieved. Transmission electron microscopy revealed that all vertically threading defects stemming from the GaN/AlN and AlN/SiC interfaces are contained within the seed forms and a substantial reduction in the dislocation density of the laterally grown GaN. Atomic force microscopy analysis of the (112 0) face of discrete pendeoepitaxial structures revealed a root mean square roughness of 0.98 Å. The pendeoepitaxial layer photoluminescence band edge emission peak was observed to be 3.454 eV and is blueshifted by 12 meV as compared to the GaN seed layer.

Firestone et al. sampled sedimentary sequences at many sites across North America, Europe, and Asia [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 106:16016–16021]. In sediments dated to the Younger Dryas onset or Boundary (YDB) approximately 12,900 calendar years ago, Firestone et al. reported discovery of markers, including nanodiamonds, aciniform soot, high-temperature melt-glass, and magnetic microspherules attributed to cosmic impacts/airbursts. The microspherules were explained as either cosmic material ablation or terrestrial ejecta from a hypothesized North American impact that initiated the abrupt Younger Dryas cooling, contributed to megafaunal extinctions, and triggered human cultural shifts and population declines. A number of independent groups have confirmed the presence of YDB spherules, but two have not. One of them [Surovell TA, et al. (2009) Proc Natl Acad Sci USA 104:18155–18158] collected and analyzed samples from seven YDB sites, purportedly using the same protocol as Firestone et al., but did not find a single spherule in YDB sediments at two previously reported sites. To examine this discrepancy, we conducted an independent blind investigation of two sites common to both studies, and a third site investigated only by Surovell et al. We found abundant YDB microspherules at all three widely separated sites consistent with the results of Firestone et al. and conclude that the analytical protocol employed by Surovell et al. deviated significantly from that of Firestone et al. Morphological and geochemical analyses of YDB spherules suggest they are not cosmic, volcanic, authigenic, or anthropogenic in origin. Instead, they appear to have formed from abrupt melting and quenching of terrestrial materials.

Grooming, a common behavior in animals, serves the important function of removing foreign materials from body surfaces. When antennal grooming was prevented in the American cockroach, Periplaneta americana, field emission gun scanning electron microscopy images revealed that an unstructured substance accumulated on nongroomed antennae, covering sensillar pores, but not on groomed antennae of the same individuals. Gas chromatography analysis of antennal extracts showed that over a 24-h period nongroomed antennae accumulated three to four times more cuticular hydrocarbons than groomed antennae. Moreover, nongroomed antennae accumulated significantly more environmental contaminants from surfaces (stearic acid) and from air (geranyl acetate) than groomed antennae. We hypothesized that the accumulation of excess native cuticular hydrocarbons on the antennae would impair olfactory reception. Electroantennogram experiments and single-sensillum recordings supported this hypothesis: antennae that were prevented from being groomed were significantly less responsive than groomed antennae to the sex pheromone component periplanone-B, as well as to the general odorants geranyl acetate and hexanol. We therefore conclude that antennal grooming removes excess native cuticular lipids and foreign chemicals that physically and/or chemically interfere with olfaction, and thus maintains the olfactory acuity of the antennae. Similar experimental manipulations of the German cockroach (Blattella germanica), carpenter ant (Camponotus pennsylvanicus), and the housefly (Musca domestica), which use different modes of antennal grooming, support the hypothesis that antennal grooming serves a similar function in a wide range of insect taxa.

The development of DNA detection techniques on large-area plasmonics-active platforms is critical for many medical applications such as high-throughput screening, medical diagnosis and systems biology research. Here, we report for the first time a unique “molecular sentinel-on-chip” (MSC) technology for surface-enhanced Raman scattering (SERS)-based DNA detection. This unique approach allows label-free detection of DNA molecules on chips developed on a wafer scale using large area nanofabrication methodologies. To develop plasmonics-active biosensing platforms in a repeatable and reproducible manner, we employed a combination of deep UV lithography, atomic layer deposition, and metal deposition to fabricate triangular-shaped nanowire (TSNW) arrays having controlled sub-10 nm gaps nanostructures over an entire 6-inch wafer. The detection of a DNA sequence of the Ki-67 gene, a critical breast cancer biomarker, on the TSNW substrate illustrates the usefulness and potential of the MSC technology as a novel SERS-based DNA detection method.