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(111) Surface States of SnTe
(2014-12--08) Shi, Yin; Wu, Meng; Zhang, Fan; Feng, Ji; Zhang, Fan
The characterization and applications of topological insulators depend critically on their protected surface states, which, however, can be obscured by the presence of trivial dangling bond states. Our first-principle calculations show that this is the case for the pristine (111) surface of SnTe. Yet, the predicted surface states unfold when the dangling bond states are passivated in proper chemisorption. We further extract the anisotropic Fermi velocities, penetration lengths, and anisotropic spin textures of the unfolded (Gamma) over bar -and (M) over bar -surface states, which are consistent with the theory in Zhang et al. [Phys. Rev. B 86, 081303 (2012)]. More importantly, this chemisorption scheme provides an external control of the relative energies of different Dirac nodes, which is particularly desirable in multivalley transport.
14th Annual Texas Guitar Competition and Festival
(The University of Texas at Dallas, 2016-01-26) School of Arts and Humanities; Confucius Institute; RENN Capital Group; D'Addario Strings; Savarez Strings
15.6 A 10MHz i-Collapse Failure Self-Prognostic GaN Power Converter with TJ -Independent In-Situ Condition Monitoring and Proactive Temperature Frequency Scaling
(Institute of Electrical and Electronics Engineers Inc.) Chen, Yingping; Ma, Dongsheng (Brian); Chen, Yingping; Ma, Dongsheng (Brian)
With superior figure of merits, GaN switchs are highly anticipated to replace MOSFETs in high-performance power circuits [1], [2]. However, GaN technology today still faces formidable reliability challenges [3]. While GaN device aging and failure mechanisms are not as well-studied as silicon counterparts, its unique structure and operation also induce new aging and failure problems. Use a GaN switch M_H in a buck converter of Fig. 15.6.1 as an example. As a high-side switch, it faces large-switching-current and high-input-voltage stress in each charge phase. After repetitive switching actions, a number of electron carriers can be injected into the AlGaN barrier and buffer layers, known as hot-electron injection. In discharge phase, M_H is off, but M_L becomes conductive, which shorts the source of M_H to ground, creating high VDS stress on M_H. This induces charge traps in the insulator and buffer layers, known as charge trapping. As a joint effect of both mechanisms, trapped or injected electrons in the insulator, AlGaN barrier and buffer layers repel free electrons in the channel when M_H is on, weakening the 2-dimensional electron-gas (2DEG) layer and further elevating hot-electron injection. This effect, known as current collapse or i- collapse for short, degrades channel conductivity, increases the on-resistance RDS_ON, and is a major cause of GaN-switch aging and failure [3]. On the other hand, another aging cause is thermal effect. To reduce manufacture costs and improve technology compatibility, it is common to fabricate GaN transistors on a silicon substrate. Accordingly, to reduce lattice mismatch, an AlGaN buffer layer is often inserted (Fig. 15.6.1). However, this increases the junction-to-ambient thermal resistance R θJA, which, together with the increased R_{DS_ON} due to the i- collapse, causes higher power and heat generation, elevating the junction temperature, T J. According to Arrhenius' Law, as T J increases, the mean-time-to-failure (MTTF) drops exponentially [4]. Even worse, the elevated T_J deteriorates the i- collapse effect with even higher R_{DS_ON}, significantly reducing device lifetime. ©2019 IEEE.
15.7 An 8.3MHz GaN Power Converter Using Markov Continuous RSSM for 35dBμV Conducted EMI Attenuation and One-Cycle TON Rebalancing for 27.6dB VO Jittering Suppression
(Institute of Electrical and Electronics Engineers Inc.) Chen, Yingping; Ma, Dongsheng (Brian); Chen, Yingping; Ma, Dongsheng (Brian)
GaN power switches have gained fast-growing popularity in power electronics. With a similar R DS_ON resistance, they boast 2-to-3-order lower gate capacitance than silicon counterparts, making them highly desirable in high-frequency (fsw ), high-performance power converters. However, at high f sw , switching transitions have to be completed in much shorter times, creating much larger di/dt and dv/dt changes in power stage, which directly link to electromagnetic-interference (EMI) emissions [1]. To suppress EMI, spread-spectrum-modulation (SSM) techniques [2-5] have been proposed. As depicted in Fig. 15.7.1, a periodic SSM (PSSM) is straightforward and easy to implement. However, its EMI suppression is not effective [2]. A randomized SSM (RSSM) can outperform the PSSM, with lower peak EMI and near-uniform noise spreading, but its performance highly relies on the random clock design. In [3], an N-bit digital random clock was reported to achieve a discrete RSSM (D-RSSM). However, the bit number N has to be large in order to achieve satisfying EMI attenuation, significantly increasing circuit complexity, chip area, and power consumption. To overcome this, a thermal-noise-based random clock was proposed [4]. Unfortunately, thermal noise is very sensitive to temperature and is hard to predict. To apply this approach to a practical implementation requires additional signal processing with periodic signals to confine its range of randomization, which, in turn, reduces the benefits of the RSSM. To achieve a near ideal RSSM, a continuous RSSM (C-RSSM) with a cost-effective implementation is highly preferable. Meanwhile, another challenge of applying SSM schemes lies in the fact that the schemes deteriorate V O voltage regulation. As shown in Fig. 15.7.1, as an SSM scheme continuously or periodically modulates f sw , a converter switching period fluctuates cycle by cycle, causing random errors on the duty ratio and thus jittering effect on V O. This is difficult to correct by a feedback control loop, as the duty-ratio error changes randomly between switching cycles. Due to a limited loop-gain bandwidth, the loop response usually lags far behind. Although a ramp compensation scheme was reported to resolve this [5], the improvement is very limited, and the scheme only works for voltage-mode converters. © 2019 IEEE.
17-β-Estradiol Induces Spreading Depression and Pain Behavior in Alert Female Rats
(Impact Journals LLC) Sandweiss, Alexander J.; Cottier, Karissa E.; McIntosh, Mary I.; Dussor, Gregory; Davis, Thomas P.; Vanderah, Todd W.; Largent-Milnes, Tally M.; Dussor, Gregory
Aims: Test the putative contribution of 17-β-estradiol in the development of spreading depression (SD) events and head pain in awake, non-restrained rats. Main Methods: Female, Sprague-Dawley rats were intact or underwent ovariectomy followed one week later by surgery to place electrodes onto the dura to detect epidural electroencephalographic activity (dEEG). dEEG activity was recorded two days later for 12 hours after systemic administration of 17-β-estradiol (180 μg/kg, i.p.). A separate set of rats were observed for changes in exploratory, ambulatory, fine, and rearing behaviors; periorbital allodynia was also assessed. Key Findings: A bolus of 17-β-estradiol significantly elevated serum estrogen levels, increased SD episodes over a 12-hour recording period and decreased rearing behaviors in ovariectomized rats. Pre-administration of ICI 182,780, an estrogen receptor antagonist, blocked 17-β-estradiol-evoked SD events and pain behaviors; similar results were observed when the antimigraine therapeutic sumatriptan was used. Significance: These data indicate that an estrogen receptor-mediated mechanism contributes to SD events in ovariectomized rats and pain behaviors in both ovariectomized -and intact-rats. This suggests that estrogen plays a different role in each phenomenon of migraine where intense fluctuations in concentration may influence SD susceptibility. This is the first study to relate estrogen peaks to SD development and pain behaviors in awake, freely moving female rats, establishing a framework for future preclinical migraine studies.
2014 ATEC Crowdfunding Month: Nov 6 - Dec 5
(The University of Texas at Dallas, 2015-12-09) School of Arts and Humanities
2015 Annual Juried Student Art Exhibition
(The University of Texas at Dallas, 2016-02-11) School of Arts and Humanities; Asel Art Supply; Paper Arts Dallas; Red River Paper; Dean's Awards, School of Arts & Humanities
2016 ASC Championship T-shirt Logo
(2016-09-29) Zeng, Fayna Lu
2019 Charles E. Williams II Advanced Leadership Institute Oratorical Contest Winning Speech
(2019-01-17) Nnoromele, Patrick
Patrick Nnoromele is a Eugene McDermott and National Merit Scholar. He is also a recipient of the Barry Goldwater Scholarship. He is majoring in Neuroscience and plans to attend medical school after graduation. This is the text of the winning speech he gave at the Charles E. Williams II Advanced Leadership Institute Oratorical Contest, held during the 2019 Southwestern Black Students Leadership Conference.
2d Frequency-Domain Elastic Full-Waveform Inversion Using Time-Domain Modeling and a Multistep-Length Gradient Approach
(Soc Exploration Geophysicists, 2014-02-17) Xu, Kun; McMechan, George A.; McMechan, George A.
To decouple the parameters in elastic full-waveform inversion (FWI), we evaluated a new multistep-length gradient approach to assign individual weights separately for each parameter gradient and search for an optimal step length along the composite gradient direction. To perform wavefield extrapolations for the inversion, we used parallelized high-precision finite-element (FE) modeling in the time domain. The inversion was implemented in the frequency domain; the data were obtained at every subsurface grid point using the discrete Fourier transform at each time-domain extrapolation step. We also used frequency selection to reduce cycle skipping, time windowing to remove the artifacts associated with different source spatial patterns between the test and predicted data, and source wavelet estimation at the receivers over the full frequency spectrum by using a fast Fourier transform. In the inversion, the velocity and density re-constructions behaved differently; as a low-wavenumber tomography (for velocities) and as a high-wavenumber migration (for density). Because velocities and density were coupled to some extent, variations were usually underestimated (smoothed) for V_P and V_S and correspondingly overestimated (sharpened) for ρ. The impedances I_P and I_S from the products of the velocity and density results compensated for the under-or overestimations of their variations, so the recovered impedances were closer to the correct ones than V_P, V_S, and ρ were separately. Simultaneous reconstruction of V_P, V_S, and ρ was robust on the FE and finite-difference synthetic data (without surface waves) from the elastic Marmousi-2 model; satisfactory results are obtained for V_P, V_S, ρ, and the recovered I_P and I_S from their products. Convergence is fast, needing only a few tens of iterations, rather than a few hundreds of iterations that are typical in most other elastic FWI algorithms.
3CPET: Finding Co-Factor Complexes from ChIA-Pet Data Using a Hierarchical Dirichlet Process
(BioMed Central Ltd, 2015-12-22) Djekidel, Mohamed Nadhir; Liang, Zhengyu; Wang, Qi; Hu, Zhirui; Li, Guipeng; Chen, Yang; Zhang, Michael Q.; 0000 0001 1707 1372 (Zhang, MQ); Zhang, Michael Q.
Various efforts have been made to elucidate the cooperating proteins involved in maintaining chromatin interactions; however, many are still unknown. Here, we present 3CPET, a tool based on a non-parametric Bayesian approach, to infer the set of the most probable protein complexes involved in maintaining chromatin interactions and the regions that they may control, making it a valuable downstream analysis tool in chromatin conformation studies. 3CPET does so by combining data from ChIA-PET, transcription factor binding sites, and protein interactions. 3CPET results show biologically significant and accurate predictions when validated against experimental and simulation data.
3D, 9C Seismic Modeling and Inversion of Weyburn Field Data
(2012-06-18) Rusmanugroho, H.; McMechan, George A.; McMechan, George A.
Inversion of 3D, 9C wide azimuth vertical seismic profiling (VSP) data from the Weyburn Field for 21 independent elastic tensor elements was performed based on the Christoffel equation, using slowness and polarization vectors measured from field data. To check the ability of the resulting elastic tensor to account for the observed data, simulation of the 3C particle velocity seismograms was done using eighth-order, staggered-grid, finite-differencing with the elastic tensor as input. The inversion and forward modeling results were consistent with the anisotropic symmetry of the Weyburn Field being orthorhombic. It was dominated by a very strong, tranverse isotropy with a vertical symmetry axis, superimposed with minor near-vertical fractures with azimuth ∼55° from the inline direction. The predicted synthetic seismograms were very similar to the field VSP data. The examples defined and provided a validation of a complete workflow to recover an elastic tensor from 9C data. The number and values of the nonzero tensor elements identified the anisotropic symmetry present in the neighborhood of a 3C borehole geophone. Computation of parameter correlation matrices allowed evaluation of solution quality through relative parameter independence. © 2012 Society of Exploration Geophysicists.
The 4-D Microgravity Method for Waterflood Surveillance: A Model Study for the Prudhoe Bay Reservoir, Alaska
(Society of Exploration Geophysicists, 1999-01) Hare, J. L.; Ferguson, John F.; Aiken, Carlos L. V.; Brady, J. L.; 67724342 (Aiken, CLV); Ferguson, J. F.; Aiken, Carlos L. V.
Forward and inverse gravity modeling is carried out on a suite of reservoir simulations of a proposed water injection on the Prudhoe Bay reservoir, Alaska. A novel surveillance technique is developed in which surface gravity observations are used to monitor the progress of a gas cap waterflood in the reservoir at 8200-ft depth. The results of the modeling showed that the inversion of time-lapse gravity data is a viable technique for monitoring reservoir gas cap waterfloods. Forward and inverse gravity modeling is carried out on a suite of reservoir simulations of a proposed water injection in the Prudhoe Bay reservoir, Alaska. A novel surveillance technique is developed in which surface gravity observations are used to monitor the progress of a gas cap waterflood in the reservoir at 8200-ft (2500-m) depth. This cost-effective method requires that high-precision gravity surveys be repeated over periods of years. Differences in the gravity field with time reflect changes in the reservoir fluid densities. Preliminary field tests at Prudhoe Bay indicates survey accuracy of 5-10 μGal can be achieved for gravity data using a modified Lacoste and Romberg 'G' type meter or Scintrex CG-3M combined with the NAVSTAR Global Positioning System (GPS). Forward gravity modeling predicts variations in surface measurements of 100 μGal after 5 years of water injection, and 180-250 μGal after 15 years. We use a constrained least-squares method to invert synthetic gravity data for subsurface density distributions. The modeling procedure has been formulated and coded to allow testing of the models for sensitivity to gravity sampling patterns, noise types, and various constraints on model parameters such as density, total mass, and moment of inertia. Horizontal-feature resolution of the waterflood is about 5000 ft (1520 m) for constrained inverse models from synthetic gravity with 5 μGal standard deviation (SD) noise. The inversion method can account for total mass of injected water to within a few percent. Worst-case scenarios result from inversion of gravity data which are contaminated by high levels (greater than 10-15 μGal SD) of spatially correlated noise, in which case the total mass estimate from inverse models may over or underestimate the mass by 10-20%. The results of the modeling indicate that inversion of time-lapse gravity data is a viable technique for the monitoring of reservoir gas cap waterfloods.
5-Methoxy-α-Methyltryptamine (5-MeO-AMT), A Tryptamine Derivative, Induces Head-Twitch Responses in Mice through the Activation of Serotonin Receptor 2a in the Prefrontal Cortex
(Elsevier Science Bv, 2018-07-24) Abiero, Arvie; Botanas, Chrislean Jun; Sayson, Leandro Val; Custodio, Raly James; de la Peña, June Bryan; Kim, Mikyung; Lee, Hyun Jun; Seo, Joung-Wook; Ryu, In Soo; Chang, Cho Min; Yang, Ji Seul; Lee, Yong Sup; Jang, Choon-Gon; Kim, Hee Jin; Cheong, Jae Hoon; de la Peña, June Bryan
5-Methoxy-α-methyltryptamine (5-MeO-AMT) is a tryptamine derivative that is used recreationally because of its reported hallucinogenic and mood elevating effects. Studies suggest that the psychopharmacological effects of tryptamines involve serotonin receptor 2a (5-HTR2a) activation in the brain. The head-twitch response (HTR) is widely used as a behavioral correlate for assessing 5-HTR2a agonist activity of a drug. Thus, we investigated whether 5-MeO-AMT induces HTR in mice and explored its mechanism of action. 5-MeO-AMT (0.3, 1, 3, 10 mg/kg) was administered once a day for 7 days, and the HTR was measured after 1 day (acute) and 7 days (repeated) of administration. Another cohort of mice was treated with 5-HTR2a antagonist ketanserin (KS) before 5-MeO-AMT administration. We measured 5-HTR2a and 5-HTR2c mRNA levels in the prefrontal cortex of the mice treated acutely or repeatedly with 5-MeO-AMT. We performed western blotting to determine the effects of the drug on the expression of G protein (G_{q/11}), protein kinase C gamma (PKC-γ), and extracellular signal-regulated kinases 1/2 (ERK1/2), in addition to PKC-γ and ERK1/2 phosphorylation. Additionally, we evaluated potential rewarding and reinforcing effects of 5-MeO-AMT using locomotor sensitization, conditioned place preference (CPP), and self-administration (SA) paradigms. Acute 5-MeO-AMT administration elicited the HTR, while repeated administration resulted in tolerance. KS blocked the 5-MeO-AMT-induced HTR. 5-MeO-AMT increased 5-HTR2a mRNA levels and induced PKC-γ phosphorylation in the prefrontal cortex. 5-MeO-AMT did not induce locomotor sensitization, CPP, or SA. This study shows that 5-MeO-AMT induces HTR through 5-HTR2a activation in the prefrontal cortex, and may have low potential for abuse.
A 25-MHz Four-Phase SAW Hysteretic Control DC-DC Converter with 1-Cycle Active Phase Count
(Institute of Electrical and Electronics Engineers Inc., 2019-02-22) Lee, Bumkil; Song, Min Kyu; Maity, Ahsis; Ma, Dongsheng (Brian); 0000-0002-4457-7157 (Ma, DB); Lee, Bumkil; Song, Min Kyu; Maity, Ahsis; Ma, Dongsheng (Brian)
In order to meet stringent power requirements in modern application processors, a 25-MHz four-phase dc-dc power converter is presented. It employs an adaptive window hysteretic control to facilitate ultra-fast transient response and minimize output voltage (VO) undershoot and overshoot during load transient periods. Inherent clock synchronization ability ensures current balancing between phase sub-converters. The control also enables a wide range of programmable VO for dynamic voltage/frequency scaling. To maintain high efficiency over a wide power range without degrading transient speed, a 1-cycle active phase count scheme is introduced. A design prototype was fabricated in a 0.35-μm CMOS process with an active die of 1.88 mm2. Simple circuit structure benefits a power density of 3.98 W/mm2. At a switching frequency of 25 MHz and a nominal input of 3.3 V, it regulates a programmable VO ranging from 0.3 to 2.5 V. It achieves more than 80% efficiency over 96.7% of power range with a peak value of 88.1%. In response to 4-A load step-up/down, it achieves 103 mV/123 mV VO undershoot/overshoot with 1% settling time of 190 ns/237 ns, respectively. ©2019 IEEE.
A Bayesian Latent Variable Approach to Aggregation of Partial and Top-Ranked Lists in Genomic Studies
(Wiley) Li, X.; Choudhary, Pankaj K.; Biswas, Swati; Wang, X.; 0000 0001 2704 188X (Biswas, S); 0000-0002-0398-7459 (Choudary, PK); Choudhary, Pankaj K.; Biswas, Swati
In genomic research, it is becoming increasingly popular to perform meta-analysis, the practice of combining results from multiple studies that target a common essential biological problem. Rank aggregation, a robust meta-analytic approach, consolidates such studies at the rank level. There exists extensive research on this topic, and various methods have been developed in the past. However, these methods have two major limitations when they are applied in the genomic context. First, they are mainly designed to work with full lists, whereas partial and/or top-ranked lists prevail in genomic studies. Second, the component studies are often clustered, and the existing methods fail to utilize such information. To address the above concerns, a Bayesian latent variable approach, called BiG, is proposed to formally deal with partial and top-ranked lists and incorporate the effect of clustering. Various reasonable prior specifications for variance parameters in hierarchical models are carefully studied and compared. Simulation results demonstrate the superior performance of BiG compared with other popular rank aggregation methods under various practical settings. A non–small-cell lung cancer data example is analyzed for illustration.
A Bibliometric Assessment of Software Engineering Scholars and Institutions (2010-2017)
(Elsevier Science Inc, 2018-10-22) Karanatsiou, Dimitra; Li, Yihao; Arvanitou, Elvira-Maria; Misirlis, Nikolaos; Wong, W. Eric; Li, Yihao; Wong, W. Eric
This paper presents the findings of a bibliometric study, targeting an eight-year period (2010-2017), with the aim of identifying: (a) emerging research directions, (b) the top-20 institutions, and (c) top-20 early stage, consolidated, and experienced scholars in the field of software engineering. To perform this goal, we performed a bibliometric study, by applying the mapping study technique on top-quality software engineering venues, and developed a dataset of 14,456 primary studies. As the ranking metric for institutions, we used the count of papers in which authors affiliated with this institute have been identified in the obtained dataset, whereas regarding scholars we computed the corresponding rankings based on the number of published papers and the average number of citations. Finally, we identified the top-20 rising scholars in the SE research community, based on their recent publication record (between 2015 and 2017) and their research age.
A Business That Can't Lose: Investing in Attacks against the Colombian Power Grid
(Elsevier B.V., 2019-05-31) Barreto, C.; Cardenas, A. A.; Holmes, Jennifer; Palao, Augustin; Restrepo, J. C.; Holmes, Jennifer; Palao, Augustin
In 2005 a company in charge of repairing electric transmission towers made a deal with guerrilla militants to demolish the towers. This company thrived, because the attacks were attributed to guerrilla groups, who commit these attacks often. However, the number of attacks increased significantly, raising alarms and leading to the discovery of the plot. We model this situation as a game between contractors and the power transmission company, and show how misaligned incentives enabled contractors to profit by colluding with guerrilla groups. We also analyze how to modify the contractual policies reducing the incentives to collude with guerrillas. In particular, the transmission company can prevent attacks by creating competition and exploiting market inefficiencies. ©2019 Elsevier B.V.
A Clinical Experiment on Infant Applied Pressures During Breastfeeding
(Amer Soc Mechanical Engineers, 2019) Jiang, Lin; Alatalo, Diana L.; Geddes, Donna T.; Hassanipour, Fatemeh; 0000-0003-0337-1192 (Hassanipour, F); Jiang, Lin; Alatalo, Diana L.; Hassanipour, Fatemeh
Breastfeeding provides both nutrients and immunities necessary for infant growth. Understanding the biomechanics of breastfeeding requires capturing both positive and negative pressures exerted by infants on the breast. This clinical experimental work utilizes thin, flexible pressure sensors to capture the positive oral pressures of 7 mother-infant dyads during breastfeeding while simultaneously measuring vacuum pressures and imaging of the infants oral cavity movement via ultrasound. Methods for denoising signals and evaluating ultrasound images are discussed. Changes and deformations on the nipple are evaluated. The results reveal that pressure from the infant's maxilla and mandible are evenly distributed in an oscillatory pattern corresponding to the vacuum pressure patterns. Variations in nipple dimensions are considerably smaller than variations in either pressure but the ultrasound shows positive pressure dominates structural changes during breastfeeding. Clinical implications for infant-led milk expression and data processing are discussed.
A Coil Detection System for Dynamic Wireless Charging of Electric Vehicle
(Institute of Electrical and Electronics Engineers Inc.) Patil, Devendra; Miller, J.; Fahimi, Babak; Balsara, Poras T.; Galigerkere, V.; Patil, Devendra; Fahimi, Babak; Balsara, Poras T.
Application of wireless power transfer while EV is in motion can significantly reduce the battery storage capacity. A major challenge in implementation of dynamic wireless power transfer (DWPT) is automatic detection of EV to avoid loss in efficiency and alleviate any safety concerns. This paper proposes a novel coil detection method for segmented DWPT. Detection of the EV ahead of its arrival will initiate energizing of the transmitter buried inside the road to enable just-in-time transfer of power. At low speeds, communication can be a reliable method to power up the transmitter coil. However, at high speeds on highways, communication latency time for the detection of an EV is long and hence impractical. This paper proposes a low cost and low power EV detection system based on a novel orthogonal coil arrangement to detect EVs traveling at high speeds. The proposed detection system was tested on a laboratory scale prototype for verification purpose. For high speed verification, simulation in PLECS was conducted to test the functionality of the proposed system. ©2019 IEEE

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