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1,166 results on '"Yu, William"'

156. Formation of PbSe/CdSe Core/Shell Nanocrystals for Stable Near-Infrared High Photoluminescence Emission

Author

Li Xinbi, Zou Bo, Cui Qingzhou, Gu Zhiyong, Zhang Yu, Dai Quanqin, Wang Yiding, and Yu William

Subjects
PbSe, CdSe, Core–shell, Near infrared, Emission, Nanocrystals, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

Abstract PbSe/CdSe core/shell nanocrystals with quantum yield of 70% were obtained by the “successive ion layer adsorption and reaction” technology in solution. The thickness of the CdSe shell was exactly controlled. A series of spectral red shifts with the CdSe shell growth were observed, which was attributed to the combined effect of the surface polarization and the expansion of carriers’ wavefunctions. The stability of PbSe nanocrystals was tremendously improved with CdSe shells.

Published
2010
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167. The Neo-Gouldian Argument for Evolutionary Contingency: Mass Extinctions

Author

Wong, Tin Yu William, Wong, Tin Yu William [0000-0002-2750-7990], and Apollo - University of Cambridge Repository

Abstract

The Gouldian argument for evolutionary contingency found in Wonderful Life (1989) can be dissected into three premises: a palaeontological, a macroevolutionary, and a developmental. Discussions of evolutionary contingency have revolved primarily around the developmental. However, a shift in methodological practice and new palaeontological evidence subsequent to the book’s publication appears to threaten the palaeontological premise that asserts high Cambrian disparity or, roughly, that morphological differences between the Cambrian species were high. This presents a prima facie problem: did the Cambrian consist of enough anatomical variety to fuel a different outcome upon a replay of the tape of life? I investigate the role that disparity plays in the Gouldian argument for evolutionary contingency and conclude that the reduced disparity view does not undermine the argument, per se. As for the macroevolutionary premise, Gould never offered any explicit justification for the idea that species sorting was indiscriminate or `lottery-like' (though he certainly gestured at it). Putting aside the exegetical, I consider certain empirical avenues for underwriting the macroevolutionary premise and argue that the most plausible route is to appeal to the special status of mass extinctions, a move that is not entirely unfamiliar to macro-evolutionists. That is -- mass extinctions can be good sources of contingency due to their being 'chancy' in, at least, three respects. In sum, I update the palaeontological and macroevolutionary premises as to reconstrue the Gouldian argument for evolutionary contingency in its strongest form.

Published
2020
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178. Significant boost of the stability and PLQYof CsPbBr3 NCs by Cu-BTC MOF.

Author

Shankar, Hari, Yu, William W., Kang, Youngjong, and Kar, Prasenjit

Subjects
*METAL-organic frameworks, *OPTICAL properties, *PEROVSKITE, *PHOTOLUMINESCENCE, *PASSIVATION, *NANOCRYSTALS
Abstract

Developing stable perovskite nanocrystals (NCs) with enhancing luminescent properties holds great importance for future potential applications in optoelectronics. Here, we engaged perovskite NCs in Cu2+ ion-based metal–organic framework (MOF) Cu-BTC (BTC = 1,3,5-benzene tricarboxylate) by physical mixing of MOF with CsPbBr3 NCs in toluene solution. MOF-protected perovskite NCs achieved high photoluminescence quantum yield 96.51% than pristine state CsPbBr3 NCs (51.66%). Along with the improvement in optical properties, the long-term stability of CsPbBr3 NCs in the solution phase also increases considerably upon loading in Cu-BTC MOF. Moreover, the changes in the luminescent intensity of the samples have been observed for 3 months in the solution. After 1 month, pristine CsPbBr3 NCs lose their emission intensity 68% from the initial, while the MOF-protected CsPbBr3 NCs show only a 10% reduction from the initial. These results indicate that the effective passivation of Cu-BTC MOF inhibits the aggregation of NCs, protecting them from the defective atmosphere. The excellent photoluminescence findings provide a new pathway for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

Published
2022
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181. CubeSat with Nanostructured Sensing Instrumentation for Planetary Exploration

Author

Wang, Joseph, Mohanty, Swomitra, Jevremovic, Tatjana, Misra, Manoranjan, Franz, Brain, Yu, William, Burnham, Steven, and Kink, Travis

Subjects
Lunar And Planetary Science And Exploration
Abstract

This report provides a summary of the work performed under NIAC Phase I award NNX15AL86G entitled "CubeSat with Nanostructured Sensing Instrumentation for Planetary Exploration". The objective of this research is to investigate the feasibility of an innovative, low cost, CubeSat based planetary mission concept for in situ "ground truth"analysis of small asteroids and comets. The project includes an instrument study and a mission/spacecraft design study. The instrument study concerns with the development of anew TiO2 nanotube sensor with integrated compound semiconductor nanowires to determine surface composition element via neutron activated analysis (NAA). The mission/spacecraft design study concerns with the development of CubeSat based lander to small asteroids and comets. The Phase I study suggests that our concept is feasible and could provide significant benefit to NASA's future planetary missions. This research was carried out at the University of Southern California and the University of Utah.

Published
2015

189. COVID Border Accountability Project, a hand-coded global database of border closures introduced during 2020

Author

Shiraef, Mary A., Hirst, Cora, Weiss, Mark A., Naseer, Sarah, Lazar, Nikolas, Beling, Elizabeth, Straight, Erin, Feddern, Lukas, Taylor, Noah Rusk, Jackson, Cayleigh, Yu, William, Bhaskaran, Aadya, Mattar, Layth, Amme, Matthew, Shum, Maggie, Mitsdarffer, Mary Louise, Sweere, Johanna, Brantley, Susanna E., Schenoni, Luis L., Lewis-Beck, Colin, Falcone, Jonathan, Hasaj, Sonila, Gradie, Amalia, Musetti, Rachel E., Nguyen, Thuy, Selvaraj, Yashwini, and Walker, Bryn

Subjects
Statistics and Probability, medicine.medical_specialty, Data Descriptor, Internationality, media_common.quotation_subject, Science, Immigration, Audit, Library and Information Sciences, computer.software_genre, Education, Politics, Political science, medicine, ddc:330, Humans, Socioeconomic status, Pandemics, media_common, Structure (mathematical logic), Social Responsibility, Travel, Database, Public health, Health Policy, COVID-19, Timeline, Computer Science Applications, Viral infection, Accountability, Communicable Disease Control, Statistics, Probability and Uncertainty, computer, Information Systems
Abstract

Quantifying the timing and content of policy changes affecting international travel and immigration is key to ongoing research on the spread of SARS-CoV-2 and the socioeconomic impacts of border closures. The COVID Border Accountability Project (COBAP) provides a hand-coded dataset of >1000 policies systematized to reflect a complete timeline of country-level restrictions on movement across international borders during 2020. Trained research assistants used pre-set definitions to source, categorize and verify for each new border policy: start and end dates, whether the closure is “complete” or “partial”, which exceptions are made, which countries are banned, and which air/land/sea borders were closed. COBAP verified the database through internal and external audits from public health experts. For purposes of further verification and future data mining efforts of pandemic research, the full text of each policy was archived. The structure of the COBAP dataset is designed for use by social and biomedical scientists. For broad accessibility to policymakers and the public, our website depicts the data in an interactive, user-friendly, time-based map., Measurement(s)border policyTechnology Type(s)digital curationFactor Type(s)country • temporal intervalSample Characteristic - EnvironmentCoronavirus pandemicSample Characteristic - Locationglobal Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.16438932

Published
2020

193. Near-Infrared LEDs Based on Quantum Cutting-Activated Electroluminescence of Ytterbium Ions

Author

Shen, Xinyu, Wang, Zhenyu, Tang, Chengyuan, Zhang, Xiangtong, Lee, Bo Ram, Li, Xin, Li, Daguang, Zhang, Yu, Hu, Junhua, Zhao, Dan, Zhang, Fujun, Yu, William W., Dong, Bin, and Bai, Xue

Abstract

Cesium lead halide perovskite nanocrystals (PNCs) exhibit promising prospects for application in optoelectronic devices. However, electroactivated near-infrared (NIR) PNC light-emitting diodes (LEDs) with emission peaks over 800 nm have not been achieved. Herein, we demonstrate the electroactivated NIR PNC LEDs based on Yb3+-doped CsPb(Cl1–xBrx)3PNCs with extraordinary high NIR photoluminescence quantum yields over 170%. The fabricated NIR LEDs possess an irradiance of 584.7 μW cm–2, an EQE of 1.2%, and a turn-on voltage of 3.1 V. The ultrafast quantum cutting process from the PNC host to Yb3+has been revealed as the main mechanism of electroluminescence (EL)-activated Yb3+for the first time via exploring how the trend between the EL intensity of PNC and Yb3+varies with different voltages along with the tendency of temperature- and doping-concentration-dependent PL and EL spectra. This work will extend the application of PNCs to optical communication, night-vision devices, and biomedical imaging.

Published
2023
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196. Cd-Rich Alloyed CsPb

Author

Guo, Jie, Fu, Yuhao, Lu, Min, Zhang, Xiaoyu, Kershaw, Stephen V., Zhang, Jia, Luo, Shulin, Li, Yanxiu, Yu, William W., Rogach, Andrey L., Zhang, Lijun, and Bai, Xue

Subjects
crystal phase engineering, Communication, Fermi levels, alloyed perovskites, lcsh:Q, nanorods, lcsh:Science, Communications, blue emission
Abstract

One‐dimensional semiconductor nanostructures have already been used for a variety of optoelectronic applications. Metal halide perovskites have emerged in recent years as promising high‐performance optoelectronic materials, but reports on 1D nanorods (NRs) of all‐inorganic halide perovskites are still scarce. This work demonstrates a synthetic strategy toward cesium‐based inorganic perovskite NRs by exploiting composition‐controlled crystal phase engineering. It is accomplished for Cd‐rich mixed‐cation CsPb1‐ xCdxBr3 nanocrystals, where the initial 1D hexagonal perovskite phase drives the growth of the 1D NRs, as supported by first‐principles calculations. The band gaps of the resulting NRs are tunable by varying the Cd‐content, and the highly uniform CsPb0.08Cd0.92Br3 NRs (with an average length of 84 nm and width of 16 nm) exhibit a true blue‐color emission centered at 460 nm, with a high quantum yield of 48%. Moreover, this work also demonstrates the tunability of the Fermi levels in the films made of CsPb1‐ xCdxBr3 alloyed nanocrystals, where samples with highest Cd content show an increase of the electron concentration and a related increase in the conductivity., It is shown that upon incorporation of sufficient levels of Cd2+ cations, the isotropic 3D cubic lattice of CsPbBr3 nanocrystals gives way to a transformation to the 1D anisotropic hexagonal lattice, which allows 1D growth of alloyed CsPb1‐ xCdxBr3 nanorods to be realized whose bandgaps can be tailored all across the blue spectral range from 2.40 eV for x = 0.10 to 2.74 eV for x = 0.96.

Published
2020

197. Complete Heart Block Complicating Takotsubo Syndrome: Case Report and Literature Review

Author

McGee, Michael J., Yu, William, McCarthy, Joshua, Barlow, Malcolm, and Hackworthy, Rosemary

Subjects
Article Subject, cardiovascular system, cardiovascular diseases
Abstract

An 81-year-old woman presents with shortness of breath resulting in a diagnosis of picornavirus and complete heart block. Troponin was elevated and there was concern about acute coronary syndrome. The final diagnosis after echocardiogram and coronary angiogram was Takotsubo syndrome in addition to the heart block which required pacemaker insertion.

Published
2020
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