Semiconductor and metallic nanowires have great potential as nano-electronic circuit components. The organization of nanowires into useful devices remains difficult because of problems in directing self-assembly of in...
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Semiconductor and metallic nanowires have great potential as nano-electronic circuit components. The organization of nanowires into useful devices remains difficult because of problems in directing self-assembly of individual components. Biological methods of self-assembling nanowires are being explored because of the high potential for specificity, the diversity of connections, and the ease of manipulation of biological interactions. Previous work demonstrated that phage could be employed as templates for the synthesis of semiconductor and metallic nanowires. The next step is to assemble the phage nanowires into useful devices by self-assembly of individual phage. We have exploited leucine zipper interactions at the ends of the phage as a means to assemble phage into one- and two-dimensional arrays. We demonstrate the in situ organization of two different sizes of semiconductor nanocrystals into alternating linear arrays. Future work includes modifying the phage ends with trimeric leucine zippers and modulating the length of individual phage.
We develop the delta-P1 approximation for frequency-domain radiative transport predictions. Comparison with Monte Carlo simulations establishes superior accuracy of the delta-P1 approximation relative to the standard ...
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A modified Mach Zehnder interferometer system has been developed to measure surface motion with 4 ns temporal resolution and 0.2 nm displacement sensitivity. We discuss its use to measure the optical properties of hom...
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Optical coherence tomography (OCT), confocal, and multiphoton microscopy are used to nondestructively monitor in situ cell distribution and cell-matrix interaction in 3-D engineered tissues composed of chitosan scaffo...
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We proposed an approach to precisely control the density of tethered chains on solid substrates using PEO-b-PS and PLLA-b-PS. As the crystallization temperature Tx increased, the PEO or PLLA lamellar crystal thickness...
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We proposed an approach to precisely control the density of tethered chains on solid substrates using PEO-b-PS and PLLA-b-PS. As the crystallization temperature Tx increased, the PEO or PLLA lamellar crystal thickness dL increased as well as the reduced tethering density σ˜ of the PS chains. The onset of tethered PS chains overcrowding in solution occurs at σ˜*∼3.7–3.8 as evidenced by an abrupt change in the slope between (dL)−1 and Tx. This results from the extra surface free energy created by the tethered chain that starts to affect the growth barrier of the crystalline blocks.
In this study, various thicknesses of Pd catalytic films were deposited on Ti/Si substrates and pretreated with NH/sub 3/. The effects of catalyst deposition parameters and NH/sub 3/ pretreatment time (0, 1, and 10 mi...
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In this study, various thicknesses of Pd catalytic films were deposited on Ti/Si substrates and pretreated with NH/sub 3/. The effects of catalyst deposition parameters and NH/sub 3/ pretreatment time (0, 1, and 10 minutes) on the size distribution of Pd catalytic particles, and subsequently, on the diameter and density of synthesized carbon nanotubes (CNTs) were investigated. The CNTs were synthesized by thermal CVD at 750/spl deg/C using methane (CH/sub 4/) as the carbon source, and a mixture of Ar/H/sub 2/ (80 vol.%/20 vol.%) as the carrier gas.
We demonstrate the use of Monte Carlo simulations to generate photon scattering density functions (PSDFs) that represent the tissue volume sampled by steady-state and frequency-domain photon migration. We use these re...
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We demonstrate the use of Monte Carlo simulations to generate photon scattering density functions (PSDFs) that represent the tissue volume sampled by steady-state and frequency-domain photon migration. We use these results to illustrate how scaling laws can be developed to determine the mean sampling depth of the multiply scattered photons detected by photon migration methods that remain valid outside the bounds of the standard diffusion approximation, i.e., at small source-detector separations and in media where the optical absorption is significant relative to scattering. Using both the PSDF computation and the newly formulated scaling laws, we focus on a comprehensive description of the effects of source modulation frequency, optical absorption, and source-detector separation on the depth of the sampled tissue volume as well as the sensitivity of frequency-domain photon migration measurements to the presence of a localized absorption heterogeneity.
Co-doped ZnO(CoxZn1−xO) is of potential interest for spintronics due to the prediction of room-temperature ferromagnetism. We have grown epitaxial CoxZn1−xO films on Al2O3(012) substrates by metalorganic chemical vapo...
Co-doped ZnO(CoxZn1−xO) is of potential interest for spintronics due to the prediction of room-temperature ferromagnetism. We have grown epitaxial CoxZn1−xO films on Al2O3(012) substrates by metalorganic chemical vapor deposition using a liquid precursor delivery system. High concentrations of Co(x⩽0.35) can be uniformly incorporated into the film without phase segregation. Co is found to be in the +2 oxidation state, independent of x, by both surface-sensitive core-level x-ray photoemission and bulk-sensitive optical absorption spectroscopies. This material can be grown n-type by the deliberate incorporation of oxygen vacancies, but not by inclusion of ∼1 at. % Al. Semiconducting films remain ferromagnetic up to 350K. In contrast films without oxygen vacancies are insulating and nonmagnetic, suggesting that exchange interaction is mediated by itinerant carriers. The saturation and remanent magnetization on a per Co basis was very small (<0.1μB∕Co), even in the best films. The dependence of saturation magnetization, as measured by optical magnetic circular dichroism, on magnetic field and temperature, agrees with the theoretical Brillouin function, demonstrating that the majority of the Co(II) ions behave as magnetically isolated S=3∕2 ions.
In the previous work, cordierite-based glass ceramics were successful prepared by optimising dispersants. In this paper, four different binders were investigated and their effects on the rheological behaviour of the s...
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In the previous work, cordierite-based glass ceramics were successful prepared by optimising dispersants. In this paper, four different binders were investigated and their effects on the rheological behaviour of the suspensions and on the microstructures of the green tapes were compared. Meanwhile, a good compatibility between the dispersant and binder was found to be a predominant factor to obtain an optimised cordierite glass ceramic tape. The microstructure of the green tapes was observed by SEM and the weight loss during binder burn out process was determined by DTA/TG The dielectric constant and dielectric loss of the sintered tapes (at 1150℃for 2h) was also measured.
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