Publications by Year: 2013

2013
R. Hennessy, Lim, S. L., Markey, M. K., and Tunnell, J. W., “Monte Carlo lookup table-based inverse model for extracting optical properties from tissue-simulating phantoms using diffuse reflectance spectroscopy.,” J Biomed Opt, vol. 18, no. 3, pp. 037003, 2013.Abstract
We present a Monte Carlo lookup table (MCLUT)-based inverse model for extracting optical properties from tissue-simulating phantoms. This model is valid for close source-detector separation and highly absorbing tissues. The MCLUT is based entirely on Monte Carlo simulation, which was implemented using a graphics processing unit. We used tissue-simulating phantoms to determine the accuracy of the MCLUT inverse model. Our results show strong agreement between extracted and expected optical properties, with errors rate of 1.74% for extracted reduced scattering values, 0.74% for extracted absorption values, and 2.42% for extracted hemoglobin concentration values.
E. Ortega, Torres-Verdín, C., Preeg, W. E., and Miles, J., “Multidetector LWD Sigma logging principles, petrophysical applications, and environmental effects (Expanded Abstract),” Society of Petrophysicists and Well Log Analysts 54th Annual Logging Symposium. Society of Petrophysicists and Well Log Analysts, New Orleans, LA, 2013.PDF icon PDF
E. Ortega, Torres-Verdín, C., Preeg, W. E., and Miles, J., “Multidetector LWD Sigma logging principles, petrophysical applications, and environmental effects (Expanded Abstract),” Society of Petrophysicists and Well Log Analysts (SPWLA) 54th Ann. Logging Symposium. New Orleans, Louisiana, 2013.PDF icon PDF
J. Liu, Xie, C., Dai, X., Jin, L., Zhou, W., and Lieber, C. M., “Multifunctional three-dimensional macroporous nanoelectronic networks for smart materials,” Proceedings of the National Academy of Sciences, vol. 110, pp. 6694–6699, 2013. Publisher's VersionAbstract
Seamless and minimally invasive integration of 3D electronic circuitry within host materials could enable the development of materials systems that are self-monitoring and allow for communication with external environments. Here, we report a general strategy for preparing ordered 3D interconnected and addressable macroporous nanoelectronic networks from ordered 2D nanowire nanoelectronic precursors, which are fabricated by conventional lithography. The 3D networks have porosities larger than 99%, contain approximately hundreds of addressable nanowire devices, and have feature sizes from the 10-μm scale (for electrical and structural interconnections) to the 10-nm scale (for device elements). The macroporous nanoelectronic networks were merged with organic gels and polymers to form hybrid materials in which the basic physical and chemical properties of the host were not substantially altered, and electrical measurements further showed a >90% yield of active devices in the hybrid materials. The positions of the nanowire devices were located within 3D hybrid materials with ∼14-nm resolution through simultaneous nanowire device photocurrent/confocal microscopy imaging measurements. In addition, we explored functional properties of these hybrid materials, including (i) mapping time-dependent pH changes throughout a nanowire network/agarose gel sample during external solution pH changes, and (ii) characterizing the strain field in a hybrid nanoelectronic elastomer structures subject to uniaxial and bending forces. The seamless incorporation of active nanoelectronic networks within 3D materials reveals a powerful approach to smart materials in which the capabilities of multifunctional nanoelectronics allow for active monitoring and control of host systems.
D. R. Bell, Xia, Z., and Ren, P., “Multiscale modeling of RNA 3D structures,” Biomedical Sciences and Engineering Conference (BSEC), 2013. IEEE, pp. 1-4, 2013.
D. R. Bell, Xia, Z., and Ren, P., “Multiscale modeling of RNA 3D structures,” in Biomedical Sciences and Engineering Conference (BSEC), 2013, 2013, pp. 1–4.
C. Xu and Torres-Verdín, C., “Multi-scale orthogonal rock class decomposition: top-down reservoir characterization integrating logs and core in tight gas sands (Expanded Abstract),” Society of Petrophysicists and Well Log Analysts 54th Annual Logging Symposium. Society of Petrophysicists and Well Log Analysts, New Orleans, LA, 2013.PDF icon PDF
C. Xu and Torres-Verdín, C., “Multi-scale orthogonal rock class decomposition: top-down reservoir characterization integrating logs and core in tight gas sands (Expanded Abstract),” Society of Petrophysicists and Well Log Analysts (SPWLA) 54th Ann. Logging Symposium. New Orleans, Louisiana, 2013.PDF icon PDF
A. J. Worthen, Bagaria, H. G., Chen, Y. S., Bryant, S. L., Huh, C., and Johnston, K. P., “Nanoparticle-stabilized carbon dioxide-in-water foams with fine texture,” Journal of Colloid and Interface Science, vol. 391, pp. 142-151, 2013. Publisher's VersionAbstract
The concept of hydrophilic/CO2-philic balance (HCB) was extended to describe stabilization of carbon dioxide-in-water (C/W) foams (also called emulsions) with silica nanoparticles adsorbed at the CO2-water interface. Opaque, white C/W foams (bubble diameter <100 mu m) were generated with either PEG-coated silica or methylsilyl modified silica nanoparticles in a beadpack with CO2 densities between 0.2 and 0.9 g mL(-1). For methylsilyl modified silica nanoparticles, 50% SiOH modification provided an optimal HCB for generation and stabilization of viscous C/W foams with high stability. The apparent viscosity measured with a capillary tube viscometer reached 120-fold that of a CO2-water mixture without nanoparticles, a consequence of the small bubble size and the energy required to deform a high density of aqueous lamellae between CO2 bubbles. Air-in-water (A/W) foams stabilized with nanoparticles were used to gain insight into the relationship between nanoparticle surface properties and adsorption of the nanoparticles at various types of interfaces. With suitable nanoparticles, A/W foams were stable for at least 7 days and C/W foams were stable for at least 23 h. The ability to achieve long term stability for nanoparticle stabilized C/W foams could offer an alternative to conventional surfactants, which are known to have much lower adsorption energies. (C) 2012 Elsevier Inc. All rights reserved.
R. Rojo, Tinney, C. E., and Baars, W. J., “Near-field/far-field study of the end-effects regime produced by large area ratio nozzles,” in 166th Meeting of the Acoustical Society of America, San Fransisco, CA, 2013, vol. 134:5, Pt 2.
J. F. Bard, Shu, Z., and Leykum, L., A Network Approach for Monthly Scheduling of Residents in Primary Care Clinics. Working paper, Graduate Program in Operations Research & Industrial Engineering, The University of Texas, Austin, TX, 2013.
J. Sulzer, Sitaram, R., Blefari, M. L., Kollias, S., Birbaumer, N., Stephan, K. E., Luft, A., and Gassert, R., “Neurofeedback-mediated self-regulation of the dopaminergic midbrain,” Neuroimage, vol. 83, pp. 817–825, 2013. LinkAbstract
The dopaminergic system is involved in reward encoding and reinforcement learning. Dopaminergic neurons from this system in the substantia nigra/ventral tegmental area complex (SN/VTA) fire in response to unexpected reinforcing cues. The goal of this study was to investigate whether individuals can gain voluntary control of SN/VTA activity, thereby potentially enhancing dopamine release to target brain regions. Neurofeedback and mental imagery were used to self-regulate the SN/VTA. Real-time functional magnetic resonance imaging (rtfMRI) provided abstract visual feedback of the SN/VTA activity while the subject imagined rewarding scenes. Skin conductance response (SCR) was recorded as a measure of emotional arousal. To examine the effect of neurofeedback, subjects were assigned to either receiving feedback directly proportional (n = 15, veridical feedback) or inversely proportional (n = 17, inverted feedback) to SN/VTA activity. Both groups of subjects were able to up-regulate SN/VTA activity initially without feedback. Veridical feedback improved the ability to up-regulate SN/VTA compared to baseline while inverted feedback did not. Additional dopaminergic regions were activated in both groups. The ability to self-regulate SN/VTA was differentially correlated with SCR depending on the group, suggesting an association between emotional arousal and neurofeedback performance. These findings indicate that SN/VTA can be voluntarily activated by imagery and voluntary activation is further enhanced by neurofeedback. The findings may lead the way towards a non-invasive strategy for endogenous control of dopamine.
J. Sulzer, Sitaram, R., Blefari, M. L., Kollias, S., Birbaumer, N., Stephan, K. E., Luft, A., and Gassert, R., “Neurofeedback-mediated self-regulation of the dopaminergic midbrain,” Neuroimage, vol. 83, pp. 817-825, 2013.
R. Anderson, Bakolas, E., Milutinovic, D., and Tsiotras, P., “Optimal Feedback Guidance of a Small Aerial Vehicle in a Stochastic Wind,” Journal of Guidance, Control, and Dynamics, vol. 36, no. 4, pp. 975-985, 2013.PDF icon jgcd_364_2013.pdf
E. Bakolas, “Optimal Partitioning for Multi-Vehicle Systems Using Quadratic Performance Criteria,” Automatica, vol. 49, no. 11, pp. 3377-3383, 2013.PDF icon automatica_inpress_2013.pdf
E. Bakolas and Tsiotras, P., “Optimal Partitioning for Spatiotemporal Coverage in a Drift Field,” Automatica, vol. 49, no. 7, pp. 2064-2073, 2013.PDF icon automatica_497_2013.pdf
E. Bakolas, “Optimal partitioning for task assignment of spatially distributed vehicles based on quadratic performance criteria,” American Control Conference. Washington, DC, pp. 3206-3211, 2013.
Z. Liang and Hasenbein, J. J., “Optimal Paths in Large Deviations of Symmetric Reflected Brownian Motion in the Octant”. 2013.Abstract
We study the variational problem that arises from consideration of large deviations for semimartingale reflected Brownian motion (SRBM) in the positive octant. Due to the difficulty of the general problem, we consider the case in which the SRBM has rotationally symmetric parameters. In this case, we are able to obtain conditions under which the optimal solutions to the variational problem are paths that are gradual (moving through faces of strictly increasing dimension) or that spiral around the boundary of the octant. Furthermore, these results allow us to provide an example for which it can be verified that a spiral path is optimal. For rotationally symmetric SRBM’s, our results facilitate the simplification of computational methods for determining optimal solutions to variational problems and give insight into large deviations behavior of these processes.
E. Bakolas and Tsiotras, P., “Optimal Synthesis of the Zermelo-Markov-Dubins Problem in a Constant Drift Field,” Journal of Optimization Theory and Applications, vol. 156, pp. 469-492, 2013.PDF icon jota_1562_2013.pdf
Y. Wang, Guo, L., Xu, X., Pierce, J., and Venkatasubramanian, R. a, “The Origin of Coherent Phonons in Bi2Te3 Excited by Ultrafast Laser Pulses,” Phys. Rev. B, vol. 88, pp. 064307 , 2013.PDF icon PDF

Pages