Publications

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We report a simple, rapid approach to synthesize water-soluble and biocompatible fluorescent quantum dot (QD) micelles by encapsulation of monodisperse, hydrophobic QDs within surfactant/lipid micelles. Analyses of UV-vis and photo luminescence spectra, along with transmission electron microscopy, indicate that the water-soluble semiconductor QD micelles are monodisperse and retain the optical properties of the original hydrophobic QDs. The QD micelles were shown to be biocompatible and exhibited little or no aggregation when taken up by cultured rat hippocampal neurons.

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The effects of atomic oxygen (AO) and vacuum UV radiation simulating low Earth orbit conditions on two commercially available piezoelectric polymer films, poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), have been studied. Surface erosion and pattern development are significant for both polymers. Erosion yields were determined as 2.8 x 10{sup -24} cm{sup 3}/atom for PVDF and 2.5 x 10{sup -24} cm{sup 3}/atom for P(VDF-TrFE). The piezoelectric properties of the residual material of both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF-TrFE) was observed. A lightly cross-linked network was formed in the copolymer presumably because of penetrating vacuum ultraviolet (VUV) radiation, while the homopolymer remained uncross-linked. These differences were attributed to varying degrees of crystallinity and potentially greater absorption, and hence damage, of VUV radiation in P(VDF-TrFE) compared with PVDF.

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Pellets of Fe/KClO{sub 4} mixtures are used as a heat source for thermally activated ('thermal') batteries. They provide the energy necessary for melting the electrolyte and bringing the battery stack to operating temperature. The effects of morphology of the Fe and the heat-pellet density and composition on both the physical properties (flowability, pelletization, and pellet strength) and the pyrotechnic performance (burn rate and ignition sensitivity) were examined using several commercial sources of Fe.

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We report the demonstration of a terahertz quantum-cascade laser that operates up to 164 K in pulsed mode and 117 K in continuous-wave mode at approximately 3.0 THz. The active region was based on a resonant-phonon depopulation scheme and a metal-metal waveguide was used for modal confinement. Copper to copper thermocompression wafer bonding was used to fabricate the waveguide, which displayed improved thermal properties compared to a previous indium-gold bonding method.

Nano photonic materials are synthetically manufactured crystals at the nano scale with the target of creating a microstructure with a special electro-magnetic periodicity. Such nano photonic materials have the ability to control light propagation and thus are capable of creating photonic bandgaps in the frequency domain. We propose using nano photonic crystals as sensors to detect microdamage in composite materials. We demonstrate using a simulation model that a nano photonic sensor attached to a composite bar experiences a significant change in its bandgap profile when damage is induced in the composite bar. The model predicts the frequency response of the nano photonic sensor using the transfer matrix method. A damage metric to evaluate the change in the frequency response is developed. Successful developments of nano photonic sensors allow damage identification at scales not attainable using current sensing technologies.

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This slide presentation outlines information on a technology acquisition strategy for the security of water distribution networks. The Department of Homeland Security (DHS) has tasked a multi-laboratory team to evaluate current and future needs to protect the nation's water distribution infrastructure by supporting an objective evaluation of current and new technologies. The primary deliverables from this Operational Technology Demonstration (OTD) are the following: establishment of an advisory board for review and approval of testing protocols, technology acquisition processes and recommendations for technology test and evaluation in laboratory and field settings; development of a technology acquisition process; creation of laboratory and field testing and evaluation capability; and, testing of candidate technologies for insertion into a water early warning system. The initial phase of this study involves the development of two separate but complementary strategies to be reviewed by the advisory board: a technology acquisition strategy; and, a technology evaluation strategy. Lawrence Livermore National Laboratory and Sandia National Laboratories are tasked with the first strategy, while Los Alamos, Pacific Northwest, and Oak Ridge National Laboratories are tasked with the second strategy. The first goal of the acquisition strategy is the development of a technology survey process that includes a review of current test programs and development of a method to solicit and select existing and emerging sensor technologies for evaluation and testing. The second goal is to implement the acquisition strategy to provide a set of recommendations for candidate technologies for laboratory and field testing.

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