Browsing by Author "Wang, J."
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Item FACT Is a Sensor of DNA Torsional Stress in Eukaryotic Cells(2018-09-24) Safina, A.; Cheney, P.; Pal, M.; Brodsky, L.; Ivanov, A.; Kirsanov, K.; Lesovaya, E.; Naberezhnov, D.; Nesher, E.; Koman, I.; Wang, D.; Wang, J.; Yakubovskaya, M.; Winkler, Duane D.; Gurova, K.; Winkler, Duane D.Transitions of B-DNA to alternative DNA structures (ADS) can be triggered by negative torsional strain, which occurs during replication and transcription, and may lead to genomic instability. However, how ADS are recognized in cells is unclear. We found that the binding of candidate anticancer drug, curaxin, to cellular DNA results in uncoiling of nucleosomal DNA, accumulation of negative supercoiling and conversion of multiple regions of genomic DNA into left-handed Z-form. Histone chaperone FACT binds rapidly to the same regions via the SSRP1 subunit in curaxin-treated cells. In vitro binding of purified SSRP1 or its isolated CID domain to a methylated DNA fragment containing alternating purine/pyrimidines, which is prone to Z-DNA transition, is much stronger than to other types of DNA. We propose that FACT can recognize and bind Z-DNA or DNA in transition from a B to Z form. Binding of FACT to these genomic regions triggers a p53 response. Furthermore, FACT has been shown to bind to other types of ADS through a different structural domain, which also leads to p53 activation. Thus, we propose that FACT acts as a sensor of ADS formation in cells. Recognition of ADS by FACT followed by a p53 response may explain the role of FACT in DNA damage prevention. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.Item Fiscal Effects of Municipal Annexation: Evidence from a Large National Sample of Urban Municipalities(Blackwell Publishing Inc.) Wang, J.; Gorina, Evgenia; 0000-0003-2499-5009 (Gorina, E); Gorina, EvgeniaThis paper examines the relationship between annexation and municipal finance and addresses a gap in the literature by studying the role of revenue structure and fiscal constraints. Using a large national sample of urban municipalities, the analysis shows that territorial expansion by itself does not influence municipal fiscal outcomes with the exception of large single parcels annexations which increase spending. We also observe negative effects of population changes on revenues and spending per capita. Since population changes typically accompany annexation, we conclude that annexing cities tend to use their added tax base to spread the revenue burden more widely rather than to increase the size of government. An important implication of this study is that state-imposed fiscal constraints do not hamper annexation success and that comprehensive urban development policies may be needed to accommodate growth and development after annexation.Item High-Performance Biscrolled MXene/Carbon Nanotube Yarn Supercapacitors(Wiley-VCH Verlag) Wang, Z.; Qin, S.; Seyedin, S.; Zhang, J.; Wang, J.; Levitt, A.; Li, Na; Haines, Carter; Ovalle-Robles, R.; Lei, W.; Gogotsi, Y.; Baughman, Ray H.; Razal, J. M.; 0000 0003 5232 4253 (Baughman, RH); 0000-0001-5845-5137 (Baughman, RH); Li, Na; Haines, Carter; Baughman, Ray H.Yarn-shaped supercapacitors (YSCs) once integrated into fabrics provide promising energy storage solutions to the increasing demand of wearable and portable electronics. In such device format, however, it is a challenge to achieve outstanding electrochemical performance without compromising flexibility. Here, MXene-based YSCs that exhibit both flexibility and superior energy storage performance by employing a biscrolling approach to create flexible yarns from highly delaminated and pseudocapacitive MXene sheets that are trapped within helical yarn corridors are reported. With specific capacitance and energy and power densities values exceeding those reported for any YSCs, this work illustrates that biscrolled MXene yarns can potentially provide the conformal energy solution for powering electronics beyond just the form factor of flexible YSCs.Item Intensity and Wavelength Dependence of Bimolecular Recombination in P3HT:PCBM Solar Cells: A White-Light Biased External Quantum Efficiency StudyCowan, S. R.; Wang, J.; Yi, J.; Lee, Y. -J; Olson, D. C.; Hsu, Julia W. P.; 0000 0003 8600 0978 (Hsu, JWP); 243648305 (Hsu, JWP)Bimolecular recombination is often a major photogenerated charge carrier loss mechanism in organic photovoltaic (OPV) devices, resulting in lower fill factor (FF) compared to inorganic devices. The recombination parameter α can be obtained from the power law fitting of short-circuit current (J sc) on illumination intensity (I), J s c ∝ I , with α values less than unity taken as an indication of reduced photon-to-electron extraction efficiency and the presence of bimolecular recombination in OPV. Here, we show that this intensity-averaged measurement is inadequate. An external quantum efficiency (EQE) apparatus under constant white-light bias can be used to measure the recombination parameter (αEQE*) as a function of wavelength and carrier density (white-light intensity). Examining the dependence of α on background white-light bias intensity and excitation wavelength provides further understanding of photon-to-electron conversion loss mechanisms in P3HT:PCBM bulk heterojunction devices in standard and inverted architectures. In order to compare EQE and current-voltage (JV) measurements, we discuss the special case of devices exhibiting sub-linear intensity response (α <1). Furthermore, we demonstrate several important advantages of the white-light biased EQE method of measuring bimolecular recombination compared to existing methods, including sensitivity in probing intensity-dependent recombination compared to steady-state JV measurements, the correlation of αEQE and FF in devices, elucidation of recombination mechanisms through spectral dependence of carrier loss, and the robustness of αEQE obtained via integration over the entire absorption region. Furthermore, this technique for measuring recombination is immediately accessible to the vast majority of researchers as the EQE apparatus is ubiquitous in PV research laboratories.Item Propagation Characteristics of Plasmaspheric Hiss: Van Allen Probe Observations and Global Empirical Models(Amer Geophysical Union, 2017-03-13) Yu, J.; Li, L. Y.; Cao, J. B.; Chen, Lunjin; Wang, J.; Yang, J.; 0000-0003-2489-3571 (Chen, L); Chen, LunjinBased on the Van Allen Probe A observations from 1 October 2012 to 31 December 2014, we develop two empirical models to respectively describe the hiss wave normal angle (WNA) and amplitude variations in the Earth's plasmasphere for different substorm activities. The long-term observations indicate that the plasmaspheric hiss amplitudes on the dayside increase when substorm activity is enhanced (AE index increases), and the dayside hiss amplitudes are greater than the nightside. However, the propagation angles (WNAs) of hiss waves in most regions do not depend strongly on substorm activity, except for the intense substorm-induced increase in WNAs in the nightside low L-region. The propagation angles of plasmaspheric hiss increase with increasing magnetic latitude or decreasing radial distance (L-value). The global hiss WNAs (the power-weighted averages in each grid) and amplitudes (medians) can be well reproduced by our empirical models.Item Surface Photovoltage Characterization of Organic Photovoltaic DevicesLee, Y. -J; Wang, J.; Hsu, J. W. P.; 0000 0003 8600 0978 (Hsu, JWP); 243648305 (Hsu, JWP)Surface photovoltage response in bulk heterojunction organic solar cells is determined using a Kelvin probe with variable illumination intensity and wavelength. The effect of device architecture, carrier transport layers, donor:acceptor combinations, and device processing conditions are studied. We observe a positive (negative) surface photovoltage response, corresponding to efficient accumulation of electrons (holes) at the top electrode in conventional (inverted) devices. The linear relationship between surface photovoltage and log(intensity) and the agreement with open circuit voltage indicate that surface photovoltage magnitude quantifies the separation of photogenerated carriers in organic solar cells at open circuit condition.Item The Band Structure Change of Hf₀.₅Zr₀.₅O₂/Ge System upon Post Deposition Annealing(Elsevier B.V., 2019-05-25) Feng, Z.; Peng, Y.; Liu, H.; Sun, Y.; Wang, Y.; Meng, M.; Liu, H.; Wang, J.; Wu, R.; Wang, Xinglu; Cho, Kyeongjae; Han, G.; Dong, H.; 0000-0003-2698-7774 (Cho, K); 369148996084659752200 (Cho, K); Wang, Xinglu; Cho, KyeongjaeHafnium zirconium oxide films have been utilized in negative capacitance (NC) field-effect transistors (FETs). The band alignment of semiconductor and HfZrOₓ film is critical to obtain high device performance. The band alignment of Hf₀.₅Zr₀.₅O₂/SiOₓ/Ge system before and after post deposition annealing at 500 °C is studied via angle resolved X-ray photoelectron spectroscopy, synchrotron radiation photoemission spectroscopy and UV–Visible spectroscopy. The band gap of Hf₀.₅Zr₀.₅O₂ is seen narrowed 0.27 ± 0.05 eV, and the valence band offset between Hf₀.₅Zr₀.₅O₂ and Ge decreases 0.25 eV ± 0.05 eV after PDA at 500 °C. Therefore, the conduction band offset is nearly unchanged. This work gives insights into the interface physics about Hf₀.₅Zr₀.₅O₂/SiOₓ and is valuable for Ge-based NC pFETs. ©2019 Elsevier B.V.Item Traveling Wave Solutions of the Time-Delayed Generalized Burgers-Type Equations(2016-12-12) Tang, B.; Fan, Y.; Wang, Xuemin; Wang, J.; Chen, S.; Wang, XueminBackground: Recently, nonlinear time-delayed evolution equations have received considerable interest due to their numerous applications in the areas of physics, biology, chemistry and so on. Methods: In this paper, we obtain traveling wave solutions by using the extended (G′/G)-expansion method. Results: Based on the method, we get many solutions of the time-delayed generalized Burgers-type equations. Conclusions: The results reveal that the extended (G′/G)-expansion method is direct, effective and can be used for many other nonlinear time-delayed evolution equations.