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Formic acid oxidation by iridium single-atom catalysts on nitrogendoped carbon

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Science China Chemistry 2020年第9期63卷 1171-1172页

作者： Huang Zhou yuen Wu Hefei National Laboratory for Physical Sciences at the Microscale Collaborative Innovation Center of Chemistry for Energy Materials(iChEM)School of Chemistry and Materials Scienceand National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230026China

The challenge of the depletion of traditional fossil fuels forces researchers to develop sustainable and highly effective energy storage and conversion *** formic acid fuel cells(DFAFCs)exhibit great potential applications in small,lightweight and long-lasting portable power sources,due to the inherent advantages of formic acid,e.g.,safer and easier to store and handle than hydrogen,faster electro-oxidation kinetics than ethanol and lower fuel crossover through the Nafion membrane than methanol[1].

关键词： kinetics methanol faster

Melt Evolution above a Spontaneously Retreating Subducting Slab in a Three-Dimensional Model

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Journal of Earth Science 2011年第2期22卷 137-142页

作者： Taras Gerya David A yuen Department of Earth Sciences Swiss Federal Institute of Technology(ETH Zurich)CH-8092 ZurichSwitzerland Adjunct Professor of Geology Department Moscow State University Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA

Dehydration of the subducting slab favors the melting of the surrounding mantle. Water content and melt evolution atop a spontaneously retreating subducting slab are reported in a three- dimensional （3-D） model. We find that fluids, including water and melts in the rocks, vary substantially along the trench, which cannot be found in two-dimensional （2-D） models. Their maxima along the subducting slab are mainly located at about 50 to 70 and 120 to 140 kin. Volumetric melt production rate changes spatially and episodically atop the slab, which may reflect the intensity and variations of volcanoes.

关键词： subduction water and melt three-dimensional model.

Mechanical stretching of 3D hydrogels for neural stem cell differentiation

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Bio-Design and Manufacturing 2022年第4期5卷 714-728页

作者： Quanjing Mei Ho-Yin yuen Xin Zhao Department of Biomedical Engineering The Hong Kong Polytechnic UniversityHung HomHong KongChina

While it is known that mechanical dynamics are influential in neural differentiation for critical processes like neurogenesis or neurodegeneration, studies on neural stem cell therapies usually focus on biochemical interactions rather than mechanical aspects, frequently resulting in low efficacy and unfulfilled potential. Therefore, current studies are attempting to elucidate the effect of mechanical stimulus on neural performance using conventional two-dimensional(2D) planar substrates. Yet, these2D substrates fail to capture the defining three-dimensional(3D) characteristics of the in vivo neural stem cell *** complete this research gap, we synthesized a series of soft and elastic 3D hydrogels to mimic the neural tissue mechanical environment for 3D cell culture, using long-chain polyethylene glycol diacrylate(PEGDA) and gelatin-methacryloyl(Gel MA).By varying the concentration of the polymer, we obtained biomimicking hydrogels with a tensile modulus as low as 10 k Pa and a compressive modulus as low as 0.8 k Pa. The in vitro results demonstrated that Gel MA-PEGDA hydrogels have the high biocompatibility required to support neural cell growth, proliferation, and differentiation, as well as neurite outgrowth. We then studied the effect of mechanical stretching on the behaviors of neural cells and observed that mechanical stretching could significantly enhance neurite extension and axon elongation. In addition, the neurites were more directionally oriented to the stretching direction. Immunocytochemistry and relative gene expression data also suggested that mechanical tension could upregulate the expression of neural differentiation protein and genes, including GFAP and βIII-Tubulin. Overall, this study shows that in addition to the specific mechanical properties of Gel MA-PEGDA that improve neural differentiation towards specific lineages, hydrogel stretching is also a potentially attractive strategy to improve the therapeutic outcomes of neural stem cel

关键词： Mechanical property Tensile stretching Hydrogels Neural differentiation 3D cell culture

Modeling of environmental influence in structural health assessment for reinforced concrete buildings

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Earthquake Engineering and Engineering Vibration 2010年第2期9卷 295-306页

作者： Ka-Veng yuen Sin-Chi Kuok Department of Civil and Environmental Engineering Univeristy of Macao

One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.

关键词： Bayesian inference model selection reinforced concrete building structural health monitoring temperature and humidity effects Timoshenko beam

Frequency dependence in the emission from subpulse drifting pulsars

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Research in Astronomy and Astrophysics 2021年第9期21卷 153-162页

作者： Xiao-Hong Han Rai yuen Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China SIfA School of PhysicsUniversity of SydneySydneyNSW 2006Australia

We investigate relations in the emission properties as revealed by drifting subpulses detected at different observing frequencies based on the method that incorporates the rotating carousels in pulsar magnetospheres of multiple emission *** emission state is associated with particular emission properties as determined by the drifting subpulses at a particular frequency,and different emission states obtained at different frequencies reveal the variation of emission properties across the emission *** method allows the determination of the essential radio emission properties such as the relative emission height,subpulse number,charge density and the plasma flow relative to corotation in an emission region for a particular *** apply the method to seven pulsars that exhibit subpulse drifting along single drift-band at 326 MHz and 1429 *** results show that drifting subpulses observed at different frequencies correspond to particular emission states suggesting that the pulsar emission properties are frequency *** show that emission follows the frequency-to-radius mapping for pulsars with obliquity angle?30°regardless of the sign and magnitude of the *** pulsars with long rotation periods in our sample,the circulation time for the plasma to revolve once around the magnetosphere relative to corotation increases as the rotation period increases at both frequencies,but exhibits irregularity for pulsars with short rotation *** results suggest that evolution of the obliquity angles in subpulse drifting pulsars is from large to small,and the emission region tends to be’thicker’in younger pulsars.

关键词： radiation mechanisms:non-thermal pulsar:general

Additive Schwarz Preconditioners with Minimal Overlap for Triangular Spectral Elements

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Communications in Computational Physics 2013年第2期13卷 411-427页

作者： yuen-Yick Kwan Center for Computational Science Tulane UniversityNewOrleansLA 70118USA

The additive Schwarz preconditioner with minimal overlap is extended to triangular spectral elements(TSEM).Themethod is a generalization of the corresponding method in tensorial quadrilateral spectral elements(QSEM).The proposed preconditioners are based on partitioning the domain into overlapping subdomains,solving local problems on these subdomains and solving an additional coarse problem associated with the subdomain *** results of numerical experiments show that the proposed preconditioner are robust with respect to the number of elements and are more efficient than the preconditioners with generous overlaps.

关键词： Spectral elements additive Schwarz

Modulation of Neuroimmune Responses on Glia in the Central Nervous System： Implication in Therapeutic Intervention against Neuroinflammation

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Cellular & Molecular Immunology 2009年第5期6卷 317-326页

作者： Raymond Chuen-Chung Chang Kin Chiu yuen-Shan Ho kwok-Fai So Laboratory of Neurodegenerative Diseases Depamnent of Anatomy LKSFaculty of Medicine University of Hong Kong Pokfulam Hong KongSAR China Research Centre of Heart Brain Hormone and Healthy Aging LKSFaculty of Medicine University of Hong Kong Pokfulam Hong KongSAR China State Key Laboratory for Brain and Cognitive Sciences University of HongKong. Pokfulam Hong Kong SAR China Department of Anatomy LKS Faculty of Miedicine The University of Hong Kong Rm.

It has long been known that the brain is an immunologically privileged site in normal conditions. Although the cascade of immune responses can occur as long as there is a neuronal injury or a potent immune stimulation, how the brain keeps glial cells in a quiescent state is still unclear. Increasing efforts have been made by several laboratories to elucidate how repression oi~ immune responses is achieved in the neuronal environment. The suppression factors include neurotransmitters, neurohormones, neurotrophic factors, anti-inflammatory factors, and cell-cell contact via adhesion molecules or CD200 receptor. This review discusses how these factors affect the cascade of cerebral immune responses because no single factor listed above can fully account for the immune suppression. While several factors contribute to the suppression of immune responses, activation of glial cells and their production of pro-inflammatory factors do occur as long as there is a neuronal injury, suggesting that some neuronal components facilitate immune responses. This review also discusses which signals initiate or augment cerebral immune responses so that stimulatory signals override the suppressive signals. Increasing lines of evidence have demonstrated that immune responses in the brain are not always detrimental to neurons. Attempt to simply clear off inflammatory factors in the CNS may not be appropriate for neurons in neurological disorders. Appropriate control of immune cells in the CNS may be beneficial to neurons or even neuroregeneration. Therefore, understanding the mechanisms underlying immune suppression may help us to reshape pharmacological interventions against inflammation in many neurological disorders.

关键词： neural cell adhesion molecule neurotrophins potassium ions microglia neuroinflammation

Updatable timed automata with one updatable clock

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Science China(Information Sciences) 2018年第1期61卷 99-112页

作者： Guoqiang LI Yunqing WEN Shoji yuen BASICS School of Software Shanghai Jiao Tong University Graduate School of Information Science Nagoya University

Updatable timed automata(UTAs) proposed by Bouyer ***., is an extension of timed automata(TAs) having the extra ability to update clocks in a more elaborate way than simply reset them to *** reachability of UTAs is generally undecidable, which can be easily gained by regarding a pair of clocks as updatable counters. This paper investigates a subclass of UTAs by restricting the number of updatable clocks to be one. We will show that(1) the reachability of general UTAs with one updatable clock(UTA1 s)is still undecidable, and(2) that of UTA1 s under diagonal-free constraints is decidable, and the complexity is Pspace-complete. The former is achieved by encoding Minsky machines to the general UTA1 s, where two counters are simulated by the updatable clock. The latter is gained by regarding a region of a UTA1 to be an unbounded digiword, and encoding sets of digiwords that are accepted by a one counter automaton where regions are generated as the value of the counter.

关键词： updatable timed automata one counter automata digiword reachability problem

The diffusion of Hong Kong cultural values to China's Mainland: a case study in Shenzhen

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Journal of Geographical Sciences 1998年第4期8卷 66-75页

作者： CHOW Chun Shing MUI yuen yung ZHAO Xiaobin Department of Geography Hong Kong Baptist University

s—Since Shenzhen became a special economic zone in 1980, it has achieved spectacular growth in its economy. At the same time, it has opened its door to the importation of foreign goods and cultures,particularly from its neighboring city,Hong ***,Hong Kong cultural traits, including materialism, individualism, and the idolization of movie stars and pop singers have become well accepted and commonly followed by the people in Shenzhen. This paper looks into the role of mass communication, particularly television programs, in this process of cultural diffusion, and to assess the cause and effect of such changes on Shenzhen.

关键词： mass media TV program cultural diffusion Hong Kong Shenzhen.