In Press
H. Daigle and Dugan, B., “Data report: permeability, consolidation, stress state, and pore system characteristics of sediments from Sites C0011, C0012, and C0018 of the Nankai accretionary complex,” Proceedings of the Integrated Ocean Drilling Program, Scientific Reports, In Press.
In Press, 2018
J. Jeong, Chen, K., Walker, E. S., Roy, N., He, F., Liu, P., Willson, G. C., Cullinan, M., Bank, S. R., and Wang, Y., “In-plane thermal conductivity measurement with nanosecond grating imaging tehchnique,” Nanoscale and Microscale Thermophyical Engineering, In Press, 2018. Publisher's VersionAbstract
We develop a nanosecond grating imaging (NGI) technique to measure in-plane thermal transport properties in bulk and thin-film samples. Based on nanosecond time-domain thermoreflectance (ns-TDTR), NGI incorporates a photomask with periodic metal strips patterned on a transparent dielectric substrate to generate grating images of pump and probe lasers on the sample surface, which induces heat conduction along both cross- and in-plane directions. Analytical and numerical models have been developed to extract thermal conductivities in both bulk and thin-film samples from NGI measurements. This newly developed technique is used to determine thickness-dependent in-plane thermal conductivities (κx) in Cu nano-films, which agree well with the electron thermal conductivity values converted from four-point electrical conductivity measurements using the Wiedemamn–Franz law, as well as previously reported experimental values. The κx measured with NGI in an 8 nm x 8 nm GaAs/AlAs superlattice (SL) is about 10.2 W/m⋅K, larger than the cross-plane thermal conductivity (8.8 W/m⋅K), indicating the anisotropic thermal transport in the SL structure. The uncertainty of the measured κx is about 25% in the Cu film and less than 5% in SL. Sensitivity analysis suggests that, with the careful selection of proper substrate and interface resistance, the uncertainty of κx in Cu nano-films can be as low as 5%, showing the potential of the NGI technique to determine κx in thin films with improved accuracy. By simply installing a photomask into ns-TDTR, NGI provides a convenient, fast, and cost-effective method to measure the in-plane thermal conductivities in a wide range of structures and materials.
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E. Bakolas, “Finite-Horizon Covariance Control for Discrete-Time Stochastic Linear Systems Subject to Input Constraints,” Automatica, vol. 91, pp. 61-68, In Press, 2018.
C. Lu, Jing, Z., Wu, C., Piquemal, J. - P., Ponder, J. W., Ren, P., and others,AMOEBA Polarizable Atomic Multipole Force Field for Nucleic Acids,” J Chem Theory Comp, vol. in press, 2018. Publisher's Version
K. Chen, Roy, A., Rai, A., Valsaraj, A., Meng, X., He, F., Xu, X., Register, L. F., Banerjee, S., and Wang, Y., “Carrier Trapping by Oxygen Impurities in Molybdenum Diselenide,” ACS Applied Materials & Interfaces, vol. 10, no. 1, pp. 1125–1131, 2018. Publisher's VersionAbstract
Understanding defect effect on carrier dynamics is essential for both fundamental physics and potential applications of transition metal dichalcogenides (TMDs). Here, the phenomenon of oxygen impurities trapping photoexcited carriers has been studied with ultrafast pump-probe spectroscopy. Oxygen impurities are intentionally created in exfoliated multilayer MoSe2 with Ar+plasma irradiation and air exposure. After plasma treatment, the signal of transient absorption first increases and then decreases, which is a signature of defect-capturing carriers. With larger density of oxygen defects, the trapping effect becomes more prominent. The trapping defect densities are estimated from the transient absorption signal, and its increasing trend in the longer-irradiated sample agrees with the results from X-ray photoelectron spectroscopy. First-principle calculations with density functional theory reveal that oxygen atoms occupying Mo vacancies create mid-gap defect states, which are responsible for carrier trapping. Our findings shed light on the important role of oxygen defects as carrier trappers in TMDs, and facilitate defect engineering in relevant materials and device applications.
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J. Kim, Fleming, E., Zhou, Y., and Shi, L., “Comparison of four-probe thermal and thermoelectric transport measurements of thin films and nanostructures with microfabricated electro-thermal transducers,” Journal of Physics D: Applied Physics, vol. 51, pp. 103002, 2018. Publisher's Version
N. K. Roy, Dibua, O. G., Jou, W., He, F., Jeong, J., Wang, Y., and Cullinan, M., “A comprehensive study of the sintering of copper nanoparticles using femtosecond, nanosecond and continuous wave lasers,” Journal of Micro and Nano-Manufacturing, vol. 6, no. 1, pp. 010903, 2018. Publisher's VersionAbstract
A high electrical and thermal conductivity coupled with low costs make copper (Cu) an enticing alternative to aluminum for fabrication of interconnects in packaging applications. To tap into the benefits of the ever-reducing size of transistors, it is required to increase the input/output (I/O) pin count on electronic chips and thus minimize the size of chip to board interconnects. Laser sintering of Cu nanoparticle (NP) inks can serve as a promising process for developing these micron sized, 3D interconnect structures. However, the exact processing windows for Cu NP sintering are not well known. Therefore, this paper presents an extensive experimental investigation of the sintering processing window with different lasers including femtosecond (fs), nanosecond (ns) and continuous-wave (CW) lasers. The dependence of the processing window on Cu layer thicknesses and laser exposure durations has also been investigated. A simplified model to estimate optimum laser sintering windows for Cu NPs using pulsed lasers is presented and the predicted estimates are compared against the experimental results. Given the simplicity of the model, it is shown to provide good estimates for fluence required for the onset of sintering and the processing window for good sintering of Cu NPs.
J. Zhao, Wang, G., del Mundo, I. M., McKinney, J. A., Lu, X., Bacolla, A., Boulware, S. B., Zhang, C., Zhang, H., Ren, P., and others,Distinct Mechanisms of Nuclease-Directed DNA-Structure-Induced Genetic Instability in Cancer Genomes,” Cell reports, vol. 22, pp. 1200–1210, 2018.
D. S. Choi, Poudel, N., Park, S., Akinwande, D., Cronin, S. B., Watanabe, K., Taniguchi, T., Yao, Z., and Shi, L., “Large Reduction of Hot Spot Temperature in Graphene Electronic Devices with Heat-Spreading Hexagonal Boron Nitride,” ACS Applied Materials & Interfaces, 2018. Publisher's Version
S. Qu, Hu, M. - B., Wang, Y., and Song, T., “Modeling the influences of Ag or Au nanoparticles on the solar energy absorption and photocatalytic properties of N-TiO2,” Optics Communications, vol. 407, pp. 375-380, 2018. Publisher's VersionAbstract
Metallic nanoparticles have unique optical properties such as localized surface plasmon resonance (LSPR) effect, which can be used to improve the energy absorption and photocatalytic properties of semiconductor bases. In this paper, we construct a model to study the influence of Ag or Au nanoparticles (cubes or spheres) on the solar energy absorption and photocatalytic properties of nitrogen doped TiO2 (or N-TiO2). Effects of specific nanoparticle coupling parameters, such as particle shape, size, doping period (metal–metal distance) and separation distance (metal–semiconductor distance), on the properties of N-TiO2 are studied in detail. We show that the photocurrent improvement can be optimized by setting suitable geometric parameters. In particular, the separation distance between metallic nanoparticles and N-TiO2D should be around 6–7 nm, and the period of doping P should be around 360 nm. The silver cubes with edge length  show the best performance. The results can help the design of solar energy materials, in which metallic nanoparticles may play an important role.
L. Luan, Sullender, C. T., Li, X., Zhao, Z., Zhu, H., Wei, X., Xie, C., and Dunn, A. K., “Nanoelectronics enabled chronic multimodal neural platform in a mouse ischemic model,” Journal of neuroscience methods, vol. 295, pp. 68 - 76, 2018. Publisher's VersionAbstract
Background Despite significant advancements of optical imaging techniques for mapping hemodynamics in small animal models, it remains challenging to combine imaging with spatially resolved electrical recording of individual neurons especially for longitudinal studies. This is largely due to the strong invasiveness to the living brain from the penetrating electrodes and their limited compatibility with longitudinal imaging.
X. Wei, Luan, L., Zhao, Z., Li, X., Zhu, H., Potnis, O., and Xie, C., “Nanofabricated Ultraflexible Electrode Arrays for High-Density Intracortical Recording,” Advanced Science, pp. 1700625–n/a, 2018. Publisher's VersionAbstract
Understanding brain functions at the circuit level requires time-resolved simultaneous measurement of a large number of densely distributed neurons, which remains a great challenge for current neural technologies. In particular, penetrating neural electrodes allow for recording from individual neurons at high temporal resolution, but often have larger dimensions than the biological matrix, which induces significant damage to brain tissues and therefore precludes the high implant density that is necessary for mapping large neuronal populations with full coverage. Here, it is demonstrated that nanofabricated ultraflexible electrode arrays with cross-sectional areas as small as sub-10 µm2 can overcome this physical limitation. In a mouse model, it is shown that these electrodes record action potentials with high signal-to-noise ratio; their dense arrays allow spatial oversampling; and their multiprobe implantation allows for interprobe spacing at 60 µm without eliciting chronic neuronal degeneration. These results present the possibility of minimizing tissue displacement by implanted ultraflexible electrodes for scalable, high-density electrophysiological recording that is capable of complete neuronal circuitry mapping over chronic time scales.
E. Bakolas, “Distributed Partitioning Algorithms for Locational Optimization of Multi-Agent Networks in SE(2),” IEEE Transactions on Automatic Control, vol. 63, no. 1, pp. 101-116, 2018. Publisher's VersionPDF icon ieee_tac17_eb.pdf
E. Bakolas, “A Solution to the Minimum L1-Norm Controllability
Problem for Discrete-Time Linear Systems via Iteratively
Reweighted Least Squares
,” American Control Conference. 2018.
E. Bakolas, “Constrained Minimum Variance Control for Discrete-Time Stochastic Linear Systems,” Systems & Control Letters, vol. 113, no. 3, pp. 109-116, 2018. Publisher's VersionPDF icon mvc_scl_fvrev_8.pdf
D. Pylorof and Bakolas, E., “Robust Distributed and Decentralized Control of
Large-Scale Nonlinear Systems with Input Constraints based
on SOS Optimization
,” American Control Conference. 2018.
L. Lagardère, Jolly, L. - H., Lipparini, F., Aviat, F., Stamm, B., Jing, Z. F., Harger, M., Torabifard, H., Cisneros, A. G., Schnieders, M. J., and others,Tinker-HP: a massively parallel molecular dynamics package for multiscale simulations of large complex systems with advanced point dipole polarizable force fields,” Chemical Science, 2018.
C. E. Schaefer, Ho, P., Gurr, C., Berns, E., and Werth, C. J., “Abiotic dechlorination of chlorinated ethenes in natural clayey soils: Impacts of mineralogy and temperature,” Journal of Contaminant Hydrology, 2017. Publisher's VersionAbstract
Laboratory batch experiments were performed to assess the impacts of temperature and mineralogy on the abiotic dechlorination of tetrachloroethene (PCE) or trichloroethene (TCE) due to the presence of ferrous minerals in natural aquifer clayey soils under anaerobic conditions. A combination of x-ray diffraction (XRD), magnetic susceptibility, and ferrous mineral content were used to characterize each of the 3 natural soils tested in this study, and dechlorination at temperatures ranging from 20 to 55 °C were examined. Results showed that abiotic dechlorination occurred in all 3 soils examined, yielding reduced gas abiotic dechlorination products acetylene, butane, ethene, and/or propane. Bulk first-order dechlorination rate constants (kbulk), scaled to the soil:water ratio expected for in situ conditions, ranged from 2.0 × 10−5 day−1 at 20 °C, to 32 × 10−5 day−1 at 55 °C in the soil with the greatest ferrous mineral content. For the generation of acetylene and ethene from PCE, the reaction was well described by Arrhenius kinetics, with an activation energy of 91 kJ/mol. For the generation of coupling products butane and propane, the Arrhenius equation did not provide a satisfactory description of the data, likely owing to the complex reaction mechanisms associated with these products and/or diffusional mass transfer processes associated with the ferrous minerals likely responsible for these coupling reactions. Although the data set was too limited to determine a definitive correlation, the two soils with elevated ferrous mineral contents had elevated abiotic dechlorination rate constants, while the one soil with a low ferrous mineral content had a relatively low abiotic dechlorination rate constant. Overall, results suggest intrinsic abiotic dechlorination rates may be an important long-term natural attenuation component in site conceptual models for clays that have the appropriate iron mineralogy.
B. S. Wendel, He, C. F., Qu, M. J., Wu, D., Hernandez, S. M., Ma, K. Y., Liu, E. W., Xiao, J., Crompton, P. D., Pierce, S. K., Ren, P. Y., Chen, K. K., and Jiang, N., “Accurate immune repertoire sequencing reveals malaria infection driven antibody lineage diversification in young children,” Nature Communications, vol. 8, 2017.Abstract
Accurately measuring antibody repertoire sequence composition in a small amount of blood is challenging yet important for understanding repertoire responses to infection and vaccination. We develop molecular identifier clustering-based immune repertoire sequencing (MIDCIRS) and use it to study age-related antibody repertoire development and diversification before and during acute malaria in infants (<12 months old) and toddlers (12-47 months old) with 4-8ml of blood. Here, we show this accurate and high-coverage repertoire-sequencing method can use as few as 1000 naive B cells. Unexpectedly, we discover high levels of somatic hypermutation in infants as young as 3 months old. Antibody clonal lineage analysis reveals that somatic hypermutation levels are increased in both infants and toddlers upon infection, and memory B cells isolated from individuals who previously experienced malaria continue to induce somatic hypermutations upon malaria rechallenge. These results highlight the potential of antibody repertoire diversification in infants and toddlers.