Publications by Year: 2012

B. W. Donald, Baars, W. J., Tinney, C. E., and Ruf, J. H., “Acoustic characterization of sub-scale rocket nozzles,” 50th AIAA Aerospace Sciences Meeting and Exposition. AIAA Paper 2012-0544, Nashville, TN, 2012.PDF icon c2012aiaa-nashvilledonald-0544.pdf
T. Bui-Thanh, Ghattas, O., and Higdon, D., “Adaptive Hessian-based Non-stationary Gaussian Process Response Surface Method for Probability Density Approximation with Application to Bayesian Solution of Large-scale Inverse Problems,” SIAM Journal on Scientific Computing, vol. 34, no. 6, pp. A2837–A2871, 2012.
T. Bui-Thanh and Ghattas, O., “An Analysis of a Non-conforming hp-Discontinuous Galerkin Spectral Element Method for Wave Propagations,” SIAM Journal on Numerical Analysis, vol. 50, no. 3, pp. 1801–1826, 2012.
T. Bui-Thanh and Ghattas, O., “Analysis of the Hessian for Inverse Scattering Problems, Part I: Inverse Shape Scattering of Acoustic Waves,” 2013 Highlight Collection of Inverse Problems, vol. 28, pp. 055001, 2012.
T. Bui-Thanh and Ghattas, O., “Analysis of the Hessian for Inverse Scattering Problems, Part II: Inverse Medium Scattering of Acoustic Waves,” Inverse Problems, vol. 28, pp. 055002, 2012.
M. A. Miller, Khan, T. A., Kaczorowski, K. J., Wilson, B. K., Dinin, A. K., Borwankar, A. U., Rodrigues, M. A., Truskett, T. M., Johnston, K. P., and Maynard, J. A., “Antibody nanoparticle dispersions formed with mixtures of crowding molecules retain activity and In Vivo bioavailability,” Journal of Pharmaceutical Sciences, vol. 101, pp. 3763-3778, 2012. Publisher's VersionAbstract
Monoclonal antibodies continue to command a large market for treatment of a variety of diseases. In many cases, the doses required for therapeutic efficacy are large, limiting options for antibody delivery and administration. We report a novel formulation strategy based on dispersions of antibody nanoclusters that allows for subcutaneous injection of highly concentrated antibody (similar to 190?mg/mL). A solution of monoclonal antibody 1B7 was rapidly frozen and lyophilized using a novel spiral-wound in-situ freezing technology to generate amorphous particles. Upon gentle stirring, a translucent dispersion of approximately 430?nm protein clusters with low apparent viscosity (similar to 24?cp) formed rapidly in buffer containing the pharmaceutically acceptable crowding agents such as trehalose, polyethylene glycol, and n-methyl-2-pyrrolidone. Upon in vitro dilution of the dispersion, the nanoclusters rapidly reverted to monomeric protein with full activity, as monitored by dynamic light scattering and antigen binding. When administered to mice as an intravenous solution, subcutaneous solution, or subcutaneous dispersion at similar (4.67.3?mg/kg) or ultra-high dosages (51.6?mg/kg), the distribution and elimination kinetics were within error and the protein retained full activity. Overall, this method of generating high-concentration, low-viscosity dispersions of antibody nanoclusters could lead to improved administration and patient compliance, providing new opportunities for the biotechnology industry. (C) 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:37633778, 2012
L. Gao and Zhang, Z., “An Approximation Approach to Large-Scale Pavement Maintenance and Rehabilitation Problem,” Transportation Research Record: Journal of the Transportation Research Board, pp. pp. 112-118, 2012.
L. Gao and Zhang, Z., “Approximation Approach to Large-Scale Pavement Maintenance and Rehabilitation Problem,” CD Proceedings of the 91st Annual Meeting of the Transportation Research Board. Washington, DC, 2012.
D. C. McCalman, Kelley, K. H., Werth, C. J., Shapley, J. R., and Schneider, W. F., “Aqueous N2O reduction with H2 over Pd-based catalyst: mechanistic insights from experiment and simulation,” Topics in Catalysis, vol. 55, no. 5-6, pp. 300–312, 2012. Publisher's VersionAbstract
Nitrous Oxide (N2O), an ozone depleting greenhouse gas, is an observed intermediate in aqueous nitrate/nitrite reduction mediated by both natural microbial and synthetic laboratory catalysts. Because of our interest in catalytic nitrate/nitrite remediation, we have endeavored to develop a detailed concordant experimental/theoretical picture of N2O reduction with H2 over a Pd catalyst in an aqueous environment. We use batch experiments in H2 excess and limiting conditions to examine the reduction kinetics. We use density functional theory (DFT) to model the elementary steps in N2O reduction on model Pd(100), Pd(110), Pd(111) and Pd(211) facets and including the influence of adsorbed O, H, and of H2O. Both experiments and theory agree that hydrogen is necessary for removal of adsorbed oxygen from the catalyst surface. The dissociation of N2O to N2(g) and O(ads) is facile and in the absence of H proceeds until the catalyst is O-covered. Water itself is proposed to facilitate the hydrogenation of surface O by transferring absorbed hydrogen to Pd-absorbed O and OH. We measure an apparent activation energy of 41.4 kJ/mol (0.43 eV) for N2O reduction in the presence of excess H2, a value that is within 0.1 eV of the barriers determined theoretically.
D. A. Slanac, Hardin, W. G., Johnston, K. P., and Stevenson, K. J., “Atomic Ensemble and Electronic Effects in Ag-Rich AgPd Nanoalloy Catalysts for Oxygen Reduction in Alkaline Media,” Journal of the American Chemical Society, vol. 134, pp. 9812-9819, 2012. Publisher's VersionAbstract
The ability to design and characterize uniform, bimetallic alloy nanoparticles, where the less active metal enhances the activity of the more active metal, would be of broad interest in catalysis. Herein, we demonstrate that simultaneous reduction of Ag and Pd precursors provides uniform, Ag-rich AgPd alloy nanoparticles (similar to 5 nm) with high activities for the oxygen reduction reaction (ORR) in alkaline media. The particles are crystalline and uniformly alloyed, as shown by X-ray diffraction and probe corrected scanning transmission electron microscopy. The ORR mass activity per total metal was 60% higher for the AgPd2 alloy relative to pure Pd. The mass activities were 2.7 and 3.2 times higher for Ag9Pd (340 mA/mg(metal)) and Ag4Pd (598 mA/mg(metal)), respectively, than those expected for a linear combination of mass activities of Ag (60 mA/mg(Ag)) and Pd (799 mA/mg(Pd)) particles, based on rotating disk voltammetry. Moreover, these synergy factors reached 5-fold on a Pd mass basis. For silver-rich alloys (Ag <= 4Pd), the particle surface is shown to contain single Pd atoms surrounded by Ag from cyclic voltammetry and CO stripping measurements. This morphology is favorable for the high activity through a combination of modified electronic structure, as shown by XPS, and ensemble effects, which facilitate the steps of oxygen bond breaking and desorption for the ORR. This concept of tuning the heteroatomic interactions on the surface of small nanoparticles with low concentrations of precious metals for high synergy in catalytic activity may be expected to be applicable to a wide variety of nanoalloys.
D. A. Slanac, Li, L., Mayoral, A., Yacaman, M. J., Manthiram, A., Stevenson, K. J., and Johnston, K. P., “Atomic resolution structural insights into PdPt nanoparticle-carbon interactions for the design of highly active and stable electrocatalysts,” Electrochimica Acta, vol. 64, pp. 35-45, 2012. Publisher's VersionAbstract
Interfacial interactions between sub-4 nm metal alloy nanoparticles and carbon supports, although not well understood at the atomic level, may be expected to have a profound influence on catalytic properties. Pd3Pt2 alloy particles comprised of a disordered surface layer over a corrugated crystalline core are shown to exhibit strong interfacial interactions with a similar to 20-50 nm spherical carbon support, as characterized by probe aberration corrected scanning transmission electron microscopy (pcSTEM). The disordered shells were formed from defects introduced by Pd during arrested growth synthesis of the alloy nanoparticles. The chemical and morphological changes in the catalyst, before and after cyclic stability testing (1000 cycles, 0.5-1.2V). were probed with cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and pcSTEM. The strong metal-support interaction, along with the uniform alloy structure raised the mass activity by a factor of 1.8 versus pure Pt. The metal-support interactions also mitigated nanoparticle coalescence, dissolution, and ripening, resulting in only a 20% loss in mass activity (versus 60% for pure Pt on carbon) after the cyclic stability test. The design of alloy structure, guided by insight from atomic scale pcSTEM, for enhanced catalytic activity and stability, resulting from strong wetting with a deformable disordered shell, has the potential to be a general paradigm for improving catalytic performance. (C) 2011 Elsevier Ltd. All rights reserved.
J. C. Wu, Chattree, G., and Ren, P., “Automation of AMOEBA polarizable force field parameterization for small molecules,” Theoretical chemistry accounts, vol. 131, pp. 1138, 2012.
D. A. Slanac, Lie, A., Paulson, J. A., Stevenson, K. J., and Johnston, K. P., “Bifunctional Catalysts for Alkaline Oxygen Reduction Reaction via Promotion of Ligand and Ensemble Effects at Ag/MnOx Nanodomains,” Journal of Physical Chemistry C, vol. 116, pp. 11032-11039, 2012. Publisher's VersionAbstract
Achieving synergy between inexpensive metals and metal oxides is a key challenge for the development of highly active, economical catalysts. We report the synthesis and characterization of a highly active oxygen reduction reaction(ORR) catalyst composed of Ag particles (3 nm) in intimate contact with thin (similar to 1 nm) MnOx domains on Vulcan carbon (VC) as shown via electron microscopy. A new electroless co-deposition scheme, whereby MnO4- ions are reduced by carbon, formed nanosized MnOx reduction centers for Ag nanoparticle deposition. A bifunctional mechanism for ORR is proposed, in which the HO2- intermediate is formed electrochemically and is regenerated via disproportionation into OH- and O-2. A 3x mass activity enhancement is observed for Ag-MnOx/VC (125 mA/mg(Ag+MnOx)) over the linear combination of pure component activities using rotating disk voltammetry. The Ag-MnOx/VC mass activity is comparable to commercial Pd/VC (111 inA/rng(Pd)) and Pt/VC (136 mA/mg(Pt)). Furthermore, the number of electrons transferred for ORR reaches 3.5 for Ag-MnOx, higher than for MnOx (2.8) and close to the full four-electron ORR. The synergy can be rationalized by ensemble effects, where Ag and MnOx domains facilitate the formation and disproportionation of HO2-, respectively, and ligand effects from the unique electronic interaction at the Ag-MnOx interface.
P. Ren, Chun, J., Thomas, D. G., Schnieders, M. J., Marucho, M., Zhang, J., and Baker, N. A., “Biomolecular electrostatics and solvation: a computational perspective,” Quarterly reviews of biophysics, vol. 45, pp. 427–491, 2012.
Y. Yao, Yao, J., Narasimhan, V. K., Ruan, Z., Xie, C., Fan, S., and Cui, Y., “Broadband light management using low-Q whispering gallery modes in spherical nanoshells,” Nature Communications, vol. 3, pp. 664, 2012. Publisher's VersionAbstract
Light trapping across a wide band of frequencies is important for applications such as solar cells and photodetectors. Here, we demonstrate a new approach to light management by forming whispering-gallery resonant modes inside a spherical nanoshell structure. The geometry of the structure gives rise to a low quality-factor, facilitating the coupling of light into the resonant modes and substantial enhancement of the light path in the active material, thus dramatically improving absorption. Using nanocrystalline silicon (nc-Si) as a model system, we observe broadband absorption enhancement across a large range of incident angles. The absorption of a single layer of 50-nm-thick spherical nanoshells is equivalent to a 1-μm-thick planar nc-Si film. This light-trapping structure could enable the manufacturing of high-throughput ultra-thin film absorbers in a variety of material systems that demand shorter deposition time, less material usage and transferability to flexible substrates.
A. I. Dailly, Sigrist, R., Kim, Y., Wolf, P., Erckens, H., Cerny, J., Luft, A., Gassert, R., and Sulzer, J., “Can simple error sonification in combination with music help improve accuracy in upper limb movements?,” Biomedical Robotics and Biomechatronics (BioRob), 2012 4th IEEE RAS & EMBS International Conference on. IEEE, pp. 1423-1427, 2012.
T. McNelley, Oh-ishi, K., Swaminathan, S., Bradley, J., Krajewski, P. E., and Taleff, E. M., “Characteristics of the GBS-SDC Transition during Bi-axial Forming of AA5083,” Materials Science Forum, vol. 735, pp. 43–48, 2012. Publisher's VersionAbstract
Thermomechanical processing to enable superplasticity in AA5083 materials includes cold working followed by heating prior to hot blow forming. Upon heating for forming at 450°C, a B-type ({110}) rolling texture is replaced by a near-random texture with a weak superimposed cube orientation parallel to the sheet normal. The presence of refined grains 7 – 8μm in size reflects the predominance of particle-stimulated nucleation of recrystallization prior to forming. The subsequent evolution of microstructure, texture and cavitation behaviour during biaxial deformation in the solute drag creep (SDC) and grain boundary sliding (GBS) regimes will be presented.
L. Hanson, Lin, Z. C., Xie, C., Cui, Y., and Cui, B., “Characterization of the Cell-Nanopillar Interface by Transmission Electron Microscopy,” Nano Letters, vol. 12, no. 11, pp. 5815-5820, 2012. Publisher's VersionAbstract
Vertically aligned nanopillars can serve as excellent electrical, optical and mechanical platforms for biological studies. However, revealing the nature of the interface between the cell and the nanopillar is very challenging. In particular, a matter of debate is whether the cell membrane remains intact around the nanopillar. Here we present a detailed characterization of the cell-nanopillar interface by transmission electron microscopy. We examined cortical neurons growing on nanopillars with diameter 50–500 nm and heights 0.5–2 μm. We found that on nanopillars less than 300 nm in diameter, the cell membrane wraps around the entirety of the nanopillar without the nanopillar penetrating into the interior of the cell. On the other hand, the cell sits on top of arrays of larger, closely spaced nanopillars. We also observed that the membrane-surface gap of both cell bodies and neurites is smaller for nanopillars than for a flat substrate. These results support a tight interaction between the cell membrane and the nanopillars and previous findings of excellent sealing in electrophysiology recordings using nanopillar electrodes.
D. N. Espinoza and Santamarina, J. C., “Clay interaction with liquid and supercritical CO2: the relevance of electrical and capillary forces,” International Journal of Greenhouse Gas Control, vol. 10, pp. 351–362, 2012.
T. Y. Wang, Mancuso, J. J., Kazmi, S. M. S., Dwelle, J., Sapozhnikova, V., Willsey, B., Ma, L. L., Qiu, J. Z., Li, X. K., Dunn, A. K., Johnston, K. P., Feldman, M. D., and Milner, T. E., “Combined two-photon luminescence microscopy and OCT for macrophage detection in the hypercholesterolemic rabbit aorta using plasmonic gold nanorose,” Lasers in Surgery and Medicine, vol. 44, pp. 49-59, 2012. Publisher's VersionAbstract
Background and Objectives The macrophage is an important early cellular marker related to risk of future rupture of atherosclerotic plaques. Two-channel two-photon luminescence (TPL) microscopy combined with optical coherence tomography (OCT) was used to detect, and further characterize the distribution of aorta-based macrophages using plasmonic gold nanorose as an imaging contrast agent. Study Design/Materials and Methods: Nanorose uptake by macrophages was identified by TPL microscopy in macrophage cell culture. Ex vivo aorta segments (8 x 8 x 2 mm(3)) rich in macrophages from a rabbit model of aorta inflammation were imaged by TPL microscopy in combination with OCT. Aorta histological sections (5 mm in thickness) were also imaged by TPL microscopy. Results: Merged two-channel TPL images showed the lateral and depth distribution of nanorose-loaded macrophages (confirmed by RAM-11 stain) and other aorta components (e.g., elastin fiber and lipid droplet), suggesting that nanorose-loaded macrophages are diffusively distributed and mostly detected superficially within 20 mm from the luminal surface of the aorta. Moreover, OCT images depicted detailed surface structure of the diseased aorta. Conclusions: Results suggest that TPL microscopy combined with OCT can simultaneously reveal macrophage distribution with respect to aorta surface structure, which has the potential to detect vulnerable plaques and monitor plaque-based macrophages overtime during cardiovascular interventions. Lasers Surg. Med. 44:49-59, 2012. (C) 2012 Wiley Periodicals, Inc.