Publications by Type: Journal Article

F. He, Wu, W., and Wang, Y., “Direct measurement of coherent thermal phonons in Bi2Te3/Sb2Te3 superlattice,” Applied Physics A, vol. 122, pp. 777, 2016. Publisher's VersionAbstract
Coherent thermal phonons (CTPs) play an important role in thermal transport in superlattice (SL) structures. To have a profound understanding of CTP transport in SL, direct measurement of CTP properties is necessary. In this study, coherent phonon spectroscopy has been utilized to generate and detect CTP in Bi2Te3/Sb2Te3 SL. Phonon lifetimes have been extracted from experimental data, with which mode-wise thermal conductivities have been calculated. Comparing with bulk Bi2Te3, the estimated mode-wise thermal conductivity of longitudinal acoustic phonons shifts to higher frequencies, due to constructive coherent phonon interference. Our results suggest that it is possible to use SL structure to manipulate coherent phonon propagation and to tailor thermal conductivity.
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Z. Sun, Espinoza, N. D., and Balhoff, M. T., “Discrete element modeling of indentation tests to investigate mechanisms of CO2-related chemomechanical rock alteration,” Journal of Geophysical Research: Solid Earth, 2016.
Z. Ren, Jiang, S., Zeng, Q., Ding, X., Bai, S., Wang, J., Luo, Y., Su, Z., Xuan, Y., Yao, B., Cisneros, F., and Zhang, K., “Effect of dietary canthaxanthin and 25-hydroxycholecalciferol supplementation on the performance of duck breeders under two different vitamin regimens,” J Anim Sci BiotechnolJ Anim Sci Biotechnol, vol. 7, pp. 2, 2016.Abstract
BACKGROUND: Dietary canthaxanthin (CX), 25-hydroxycholecalciferol (25-OH-D 3 ) and vitamins have been widely reported to be involved in productive and reproductive performance of broiler breeders. However, limited information is available for duck breeders. In this study, a total of 1,560 Cherry Valley SM3 duck breeder females and 312 males were used to assess if the addition of CX and 25-OH-D3 could increase the performance of duck breeders under two different dietary vitamin regimens. Four diets were used under a 2 x 2 factorial arrangement with 2 kinds of vitamin premixes (REGULAR and HIGH; HIGH premix had higher levels of all vitamins except K3 than REGULAR premix), and with or without the supplementation of the mixture of CX (6 mg/kg) and 25-OH-D3 (0.069 mg/kg). The ducks were fed ad libitum with pelleted diets based on corn-soybean meal from 38 to 77 wk of age. RESULTS: HIGH vitamin premix decreased malondialdehyde (MDA) level (P < 0.001) of egg yolk, increased hatchability of fertile eggs (P = 0.029), increased hatchability of total eggs (P = 0.029), and decreased serum protein carbonyl level (P = 0.037) of breeder males. The mixture of CX and 25-OH-D3 increased serum calcium of breeder females (P = 0.010), decreased the cracked egg rate (P = 0.001), increased the pigmentation of egg yolk (P < 0.001) and male bill (P < 0.001), and decreased MDA level of egg yolk (P < 0.001) and male serum (P = 0.034). Interactive effects were observed in cracked egg rate (P = 0.038), shell thickness (P = 0.011) and serum phosphorus (P = 0.026) of breeder females. HIGH vitamin premix together with the mixture of CX and 25-OH-D3 decreased cracked egg rate and increased shell thickness of duck breeders. Serum phosphorus was decreased in duck breeder females fed REGULAR vitamin premix without the addition of the CX and 25-OH-D3 mixture. CONCLUSIONS: Dietary HIGH vitamin premix increased antioxidant status of eggs and breeder males, and increased hatchability. The mixture of CX and 25-OH-D3 enhanced egg shell quality, and promoted pigmentation and antioxidant status of eggs and breeder males.
R. Rojo, Tinney, C. E., and Ruf, J., “Effect of stagger on the vibroacoustic loads from clustered rockets,” AIAA Journal, vol. 54, no. 11, pp. 3588-3597, 2016.Abstract
The effect of stagger startup on the vibroacoustic loads that form during the end-effects regime of clustered rockets is studied using both full-scale (hot-gas) and laboratory-scale (cold-gas) data with vehicle geometry. Both configurations comprise three nozzles with thrust-optimized parabolic contours that undergo free-shock separated flow and restricted-shock separated flow as well as an end-effects regime before flowing full. Acoustic pressure waveforms recorded at the base of the nozzle cluster are analyzed using various statistical metrics as well as time-frequency analysis. The findings reveal a significant reduction in end-effects regime loads when engine startups are staggered. However, regardless of stagger, both the skewness and kurtosis of the acoustic pressure time derivative elevate to the same levels, thereby demonstrating the intermittence and impulsiveness of the acoustic waveforms during the end effects regime.
A. Qajar, Daigle, H., and Prodanović, M., “The effects of pore geometry on adsorption equilibrium in shale formations and coal-beds: Lattice density functional theory study,” Fuel, vol. 163, pp. 205-213, 2016.
T. Cantu, Rodier, B., Iszard, Z., Kilian, A., Pattani, V., Walsh, K., Weber, K., Tunnell, J., Betancourt, T., and Irvin, J., “Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties,” no. 107, pp. e53631, 2016. Publisher's VersionAbstract
A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).
A. M. Bergquist, Choe, J. K., Strathmann, T. J., and Werth, C. J., “Evaluation of a hybrid ion exchange-catalyst treatment technology for nitrate removal from drinking water,” Water Research, vol. 96, pp. 177-187, 2016. Publisher's VersionAbstract
Ion exchange (IX) is the most common approach to treating nitrate-contaminated drinking water sources, but the cost of salt to make regeneration brine, as well as the cost and environmental burden of waste brine disposal, are major disadvantages. A hybrid ion exchange-catalyst treatment system, in which waste brine is catalytically treated for reuse, shows promise for reducing costs and environmental burdens of the conventional IX system. An IX model with separate treatment and regeneration cycles was developed, and ion selectivity coefficients for each cycle were separately calibrated by fitting experimental data. Of note, selectivity coefficients for the regeneration cycle required fitting the second treatment cycle after incomplete resin regeneration. The calibrated and validated model was used to simulate many cycles of treatment and regeneration using the hybrid system. Simulated waste brines and a real brine obtained from a California utility were also evaluated for catalytic nitrate treatment in a packed-bed, flow-through column with 0.5 wt%Pd–0.05 wt%In/activated carbon support (PdIn/AC). Consistent nitrate removal and no apparent catalyst deactivation were observed over 23 d (synthetic brine) and 45 d (real waste brine) of continuous-flow treatment. Ion exchange and catalyst results were used to evaluate treatment of 1 billion gallons of nitrate-contaminated source water at a 0.5 MGD water treatment plant. Switching from a conventional IX system with a two bed volume regeneration to a hybrid system with the same regeneration length and sequencing batch catalytic reactor treatment would save 76% in salt cost. The results suggest the hybrid system has the potential to address the disadvantages of a conventional IX treatment systems.
C. Soares, Daigle, H., and Gray, K., “Evaluation of PDC bit ROP models and the effect of rock strength on model coefficients,” Journal of Natural Gas Science and Engineering, vol. 34, pp. 1225-1236, 2016.
A. Canchero, Tinney, C. E., Murray, N., and Ruf, J. H., “Flow and acoustics of clustered rockets during startup,” AIAA Journal, vol. 54, no. 5, pp. 1660-1669, 2016.Abstract
The plume produced by a cluster of two large area-ratio thrust-optimized paraboliccontour nozzles is visualized over a range of nozzle pressure ratios by way of retrore-flective shadowgraphy. Both nozzles exhibit free-shock separated flow, restricted-shockseparated flow and an end-effects regime prior to flowing full. Transient (startup) op-erations of the nozzles are studied with the primary focus being the pulsations thatform during the end-effects regime. This occurs at a pressure ratio of 37 for thesenozzles and is associated with elevated sound levels in the immediate vicinity of thenozzles and vehicle. The shadowgraphy images reveal the formation of turbulent largescale structures, on the order of the nozzle diameter, during the end-effects regime.These large scale structures are driven by the intermittent opening of the last trappedannular separation bubble to the ambient and grow rapidly within the first two nozzlediameters.
B. Ghanbarian, Hunt, A. G., and Daigle, H., “Fluid flow in porous media with rough pore‐solid interface,” Water Resources Research, 2016.
M. Lotfollahi, Kim, I., Beygi, M. R., Worthen, A. J., Huh, C., Johnston, K. P., Wheeler, M. F., and DiCarlo, D. A., “Foam Generation Hysteresis in Porous Media: Experiments and New Insights,” Transport in Porous Media, pp. 1-17, 2016. Publisher's VersionAbstract
Foam application in subsurface processes including environmental remediation, geological carbon-sequestration, and gas-injection enhanced oil recovery (EOR) has the potential to enhance contamination remediation, secure CO2">CO2CO2 storage, and improve oil recovery, respectively. Nanoparticles are a promising alternative to surfactants in creating foam in harsh environments. We conducted CO2">CO2CO2-in-brine foam generation experiments in Boise sandstones with surface-treated silica nanoparticle in high-salinity conditions. All the experiments were conducted at the fixed CO2">CO2CO2 volume fraction and fixed flow rate which changed in steps. The steady-state foam apparent viscosity was measured as a function of injection velocity. The foam flowing through the cores showed higher apparent viscosity as the flow rate increased from low to medium and high velocities. At very high velocities, once foam bubbles were finely textured, the foam apparent viscosity was governed by foam rheology rather than foam creation. A noticeable hysteresis occurred when the flow velocity was initially increased and then decreased, implying multiple (coarse and strong) foam states at the same superficial velocity. A normalized generation function was combined with CMG-STARS foam model to cover full spectrum of foam behavior in the experiments. The new model successfully captures foam generation and hysteresis trends in presented experiments in this study and data from the literature. The results indicate once foam is generated in porous media, it is possible to maintain strong foam at low injection rates. This makes foam more feasible in field applications where foam generation is limited by high injection rates that may only exist near the injection well.
R. J. Stover, Moaseri, E., Gourisankar, S. P., Iqbal, M., Rahbar, N. K., Changalvaie, B., Truskett, T. M., and Johnston, K. P., “Formation of Small Gold Nanoparticle Chains with High NIR Extinction through Bridging with Calcium Ions,” Langmuir, vol. 32, no. 4, pp. 1127-1138, 2016. Publisher's VersionAbstract
The self-assembly of citrate-capped Au nanoparticles (5 nm) resulted in branched nanochains by adding CaCl2 versus spherical nanoclusters for NaCl. These assemblies were formed between 1 s to 30 min by tuning the electrostatic repulsion and the interparticle bridging attraction between the cations and citrate ligands as a function of electrolyte concentration. For dilute Ca2+, strong interparticle bridging favored particle attachment at chain ends. This resulted in the formation of small, branched chains with lengths as short as 20 nm, due to the large Debye length for the diffuse counterions. Furthermore, the bridging produced very small interparticle spacings and sintering, as evident in high-resolution TEM despite the low temperature. This morphology produced a large red shift in the surface plasmon resonance, as characterized by a broad extinction peak with NIR absorption out to 1000 nm, which is unusual for such small particles. Whereas these properties were seen for primary particles with partial citrate monolayers, the degrees of sintering and NIR extinction were small in the case of citrate multilayers. The ability to design the size and shape of nanoparticle clusters as well as the interparticle spacing by tuning bridging and electrostatic interactions may be expected to be quite general and of broad applicability in materials synthesis
J. K. Bean and Hildebrandt Ruiz, L., “Gas-particle partitioning and hydrolysis of organic nitrates formed from the oxidation of alpha-pinene in environmental chamber experiments,” Atmos. Chem. Phys., vol. 16, pp. 2175-2184, 2016. Publisher's Version
M. Kayyalha, Maassen, J., Lundstrom, M., Shi, L., and Chen, Y. P., “Gate-tunable and thickness-dependent electronic and thermoelectric transport in few-layer MoS2,” Journal of Applied Physics, vol. 120, pp. 134305, 2016. Publisher's Version
R. Qi, Wang, Q., and Ren, P., “General van der Waals potential for common organic molecules,” Bioorg Med ChemBioorg Med Chem, vol. 24, pp. 4911-4919, 2016.Abstract
This work presents a systematic development of a new van der Waals potential (vdW2016) for common organic molecules based on symmetry-adapted perturbation theory (SAPT) energy decomposition. The Buf-14-7 function, as well as Cubic-mean and Waldman-Hagler mixing rules were chosen given their best performance among other popular potentials. A database containing 39 organic molecules and 108 dimers was utilized to derive a general set of vdW parameters, which were further validated on nucleobase stacking systems and testing organic dimers. The vdW2016 potential is anticipated to significantly improve the accuracy and transferability of new generations of force fields for organic molecules.
Z. Wang, Xu, X., Fan, D., Wang, Y., Subbaraman, H., and Chen, R. T., “Geometrical tuning art for entirely subwavelength grating waveguide based integrated photonics circuits,” Scientific Reports, vol. 6, pp. 24106, 2016. Publisher's VersionAbstract
Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to the extra degree of freedom it offers in tuning a few important waveguide properties, such as dispersion and refractive index. Devices based on SWG waveguides have demonstrated impressive performances compared to conventional waveguides. However, the high loss of SWG waveguide bends jeopardizes their applications in integrated photonic circuits. In this work, we propose a geometrical tuning art, which realizes a pre-distorted refractive index profile in SWG waveguide bends. The pre-distorted refractive index profile can effectively reduce the mode mismatch and radiation loss simultaneously, thus significantly reduce the bend loss. This geometry tuning art has been numerically optimized and experimentally demonstrated in present study. Through such tuning, the average insertion loss of a 5 μm SWG waveguide bend is reduced drastically from 5.43 dB to 1.10 dB per 90° bend for quasi-TE polarization. In the future, the proposed scheme will be utilized to enhance performance of a wide range of SWG waveguide based photonics devices.
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J. J. Hung, Borwankar, A. U., Dear, B. J., Truskett, T. M., and Johnston, K. P., “High concentration tangential flow ultrafiltration of stable monoclonal antibody solutions with low viscosities,” Journal of Membrane Science, vol. 508, pp. 113-126, 2016. Publisher's VersionAbstract
During production of concentrated monoclonal antibody formulations by tangential flow ultrafiltration (TFF), high viscosities and aggregation often cause extensive membrane fouling, flux decay and low product yields. To address these challenges, the co-solutes histidine or imidazole were added at high concentrations from 250 to 320 mM to reduce the viscosity by up to ten-fold relative to conventional low co-solute formulations, to as low as 40 cP at 250 mg/mL. At high mAb concentrations of up to 280 mg/mL, the transmembrane flux was increased threefold by adding high concentrations of co-solutes that also lowered the viscosity. Furthermore, the co-solutes also increased the mAb gel point concentration cg by up to 100 mg/mL mAb and thus enhanced concentration polarization-driven back-diffusion of the mAb at the membrane wall, which led to increased fluxes. The low viscosity and hollow fiber filter modules with straight flow paths enabled more uniform TMP and wall shear stress τw profiles, which mitigated the reversible flux decay that results from an axial decline in the local TMP. The concentrated mAb was stable by SEC before and after extended storage at 4 °C and 37 °C.
Z. Wang, Xu, X., Fan, D., Wang, Y., and Chen, R. T., “High quality factor subwavelength grating waveguide micro-ring resonator based on trapezoidal silicon pillars,” Optics Letters, vol. 41, no. 14, pp. 3375-3378, 2016. Publisher's VersionAbstract
Subwavelength grating waveguide-based micro-ring resonators (SWGMRs) are a promising platform for research in light–matter interaction. However, it is extremely difficult to achieve small radius SWGMR devices (e.g., 5 μm) with satisfying quality factors (e.g., ∼10,000). One major issue is the large bend loss of small radius SWGMRs. In this work, we report the use of trapezoidal silicon pillars instead of conventional rectangular silicon pillars as building blocks of SWGMRs. We found that an asymmetric effective refractive index profile created by trapezoidal silicon pillars can significantly reduce the bend loss and therefore increase the quality factors of SWGMRs. For the first time to the best of our knowledge, we have experimentally demonstrated a 5 μm radius SWGMR made of trapezoidal silicon pillars (T-SWGMR) with an applicable quality factor as high as 11,500, 4.6 times of that (∼2800) offered by a conventional SWGMR made of rectangular silicon pillars, which indicates an 81.4% reduction of the propagation loss. This approach can also be readily employed to enhance SWGMRs with larger radii. We have also experimentally demonstrated a 10 μm radius T-SWGMR with a quality factor as high as 45,000, which indicates a propagation loss as low as 6.07 dB/cm.
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Y. Chen, Elhag, A. S., Worthen, A. J., Reddy, P. P., Ou, A. M., Hirasaki, G. J., Nguyen, Q. P., Biswal, S. L., and Johnston, K. P., “High Temperature CO2-in-Water Foams Stabilized with Cationic Quaternary Ammonium Surfactants,” Journal of Chemical & Engineering Data, vol. 61, no. 8, pp. 2761-2770, 2016. Publisher's VersionAbstract
The design of surfactants for stabilizing CO2-in-water (brine) (C/W) foams at high temperature is challenging given the low density (solvent strength) of CO2, limited surfactant solubility in brine, and a lack of knowledge of the interfacial and rheological properties. Herein, the tail length of trimethylammonium cationic surfactants was optimized to provide the desired phase behavior and interfacial properties for formation and stabilization of the C/W foams. The headgroup was properly balanced with a C12–14 hydrocarbon tail to achieve aqueous solubility in 22% total dissolved solids (TDS) brine up to 393 K (120 °C) along with high surfactant adsorption (area/surfactant molecule of 154 Å2) at the CO2–water (C–W) interface which reduced the interfacial tension from ∼40 mN/m to ∼6 mN/m. For C12–14N(CH3)3Cl, these properties enabled stabilization of a C/W foam with an apparent viscosity of 14 mPa·s at 393 K in both a crushed calcium carbonate packed bed (75 μm2 or 76 Darcy) and a capillary tube downstream of the bed. In addition, the partition coefficient of the surfactant between oil and 22% TDS (255 kg/m3) brine was less than 0.15, which would be beneficial for minimizing the loss of the surfactant to an oil phase in applications including enhanced oil recovery and hydraulic fracturing.
G. Merletti, Gramin, P., Salunke, S., Hamman, J., Spain, D., Shabro, V., Armitage, P., Torres-Verdín, C., Salter, G., and Dacy, J., “How pore-scale attributes may be used to derive robust drainage and imbibition water saturation models in complex tight-gas reservoirs.,” Petrophysics, vol. 57, no. 5, pp. 447-464, 2016.