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Mechanical stretching of 3D hydrogels for neural stem cell differentiation

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

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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

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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

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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

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Asymptotic Results for Tail Probabilities of Sums of Dependent and Heavy-Tailed Random Variables

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Chinese Annals of Mathematics,Series B 2012年第4期33卷 557-568页

作者： Kam Chuen yuen Chuancun YIN Department of Statistics and Actuarial Science The University of Hong Kong Pokfulam Road HongKong China. Corresponding author. School of Mathematical Sciences Qufu Normal University Qufu 273165 Shan- dong China

Abstract Let X1, X2,... be a sequence of dependent and heavy-tailed random variables with distributions F1, F2,.. on （-∞,∞）, and let T be a nonnegative integer-valued random variable independent of the sequence {Xk, k 〉 1}. In this framework, the asymptotic behavior of the tail probabilities of the quantities Sn = fi Xk and S（n） =∑ k=1 n 〉 1, and their randomized versions ST and S（τ） are studied. Some risk theory are presented. max Sk for 1〈k〈n applications to the

关键词： Asymptotic tail probability Copula Heavy-tailed distribution Partialsum Risk process

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Preliminary estimation of rock-fall lateral dispersion by laboratory test

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3343-3351页

作者： Louis Ngai yuen Wong Zhicheng Tang Department of Earth Sciences The University of Hong KongHong KongChina Faculty of Engineering China University of GeosciencesWuhan430074China

Lateral dispersion significantly directs the assessment of rockfall hazard and design of countermeasures. In the present study, the dependence of lateral dispersion on different controlling factors has been systematically evaluated by performing laboratory tests using three different rock block types, namely circular block, and two types of elliptical block. The three types of rock block are released onto an inclined surface with the identical initial status. Parallel, anti-parallel, and oblique impact tests set at slope angles of 22.5° and 45°are conducted to study the block-slope interaction of rockfall. Lateral dispersion of rockfall is less influenced by the block shape for the oblique impact, while the post-impact behaviors are greatly affected by the block shape. The key factors influencing the deviation of the post-impact trajectory direction are the slope angle (θ) and direction difference (Δφ). An empirical model is then developed to characterize the deviation distribution of lateral dispersion by 5th and 95th percentile values with the inclusion of the two key factors. Linear function can be used to describe the 5th percentile boundary, while hyperbolic function is good for the 95th percentile boundary, which need to be validated by field tests in the subsequent research.

关键词： Rockfall Block shape Slope angle Oblique impact Lateral dispersion

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Single-atom Catalysts for Polymer Electrolyte Membrane Fuel Cells

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Chemical Research in Chinese Universities 2020年第3期36卷 320-328页

作者： ZHU Mengzhao WANG Jing WU yuen Department of Chemistry iChEM(Collaborative Innovation Center of Chemistryfor Energy Materials)University of Science and Technology of ChinaHefei 230026P.R.China

Searching for high-activity,stabilily and highly casbellective electrocalalysts for acid oxygen reaction rolutioo(ORR)has always been a urgent problem in polymer ectrolyte menbrane fuel ells(PEMFC).Nonetheless,the electrochemical poperties of various systems have their intrinsic limits and tremendous eforts have been paid oul to search for highly eficient electocatalysts by more raional control over the size,morphology,compoition,and *** particular,single-atom catalysts(SACs)have atrascted extensive intenest due to theirs cxcellant activity,stability,slctivity and the highest metal tiliztion In rceat yeurs,the number of papers in the field of SACs has incressed rapidly,indicating that SACs have made great *** review foouses on SACs electo-echemical applications in the acid ORR and introduces immovative syntheses,fiuel cell performance and long-time durabilily.

关键词： Singe-aton catalyst Oxygen reactio reduction Polymer electrolyte membrane fuel cell

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每人支付5欧元！这是威尼斯的入城费还是逐客令？

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环球人文地理 2024年第1期 46-55页

作者：蒋雨宁 Edmond yuen 张鹏 Luca Bravo canmandawe Tao Qi Daniil Markus Nikhg Nataliia Mark Alena scaliger

想去威尼斯旅行吗？进城请先支付5欧元！据路透社消息，意大利威尼斯市长路易吉·布鲁尼亚罗宣布，将在2024年4月25日开始，对进入威尼斯的游客收费。市长表示，这项措施将会让城市变得“可预约”，既能控制客流，又能保障游客的出行体...

想去威尼斯旅行吗？进城请先支付5欧元！据路透社消息，意大利威尼斯市长路易吉·布鲁尼亚罗宣布，将在2024年4月25日开始，对进入威尼斯的游客收费。市长表示，这项措施将会让城市变得“可预约”，既能控制客流，又能保障游客的出行体验。意大利时间2023年11月27日，威尼斯市长宣布，从2024年4月起，游客进入威尼斯将不再免费。

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Identification of novel small-molecule inhibitors of SARS-CoV-2 by chemical genetics

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Acta Pharmaceutica Sinica B 2024年第9期14卷 4028-4044页

作者： Chris Chun-Yiu Chan Qian Guo Jasper Fuk-Woo Chan Kaiming Tang Jian-Piao Cai Kenn Ka-Heng Chik Yixin Huang Mei Dai Bo Qin Chon Phin Ong Allen Wing-Ho Chu Wan-Mui Chan Jonathan Daniel Ip Lei Wen Jessica Oi-Ling Tsang Tong-Yun Wang Yubin Xie Zhenzhi Qin Jianli Cao Zi-Wei Ye Hin Chu Kelvin Kai-Wang To Xing-Yi Ge Tao Ni Dong-Yan Jin Sheng Cui Kwok-Yung yuen Shuofeng Yuan State Key Laboratory of Emerging Infectious Diseases Carol Yu Centre for InfectionDepartment of MicrobiologySchool of Clinical MedicineLi Ka Shing Faculty of Medicinethe University of Hong KongPokfulamHong Kong SAR 999077China Department of Infectious Diseases and Microbiology the University of Hong Kong-Shenzhen HospitalShenzhen 518000China Centre for Virology Vaccinology and TherapeuticsHong Kong Science and Technology ParkHong Kong SAR 999077China Academician Workstation of Hainan Province Hainan Medical University-the University of Hong Kong Joint Laboratory of Tropical Infectious DiseasesHaikou 571100China School of Biomedical Sciences Li Ka Shing Faculty of Medicinethe University of Hong KongPokfulamHong Kong SAR 999077China NHC Key Laboratory of Systems Biology of Pathogens Institute of Pathogen Biology Chinese Academy of Medical Sciences&Peking Union Medical CollegeBeijing 100730China College of Biology Hunan Provincial Key Laboratory of Medical VirologyHunan UniversityChangsha 410082China

There are only eight approved small molecule antiviral drugs for treating *** them,four are nucleotide analogues(remdesivir,JT001,molnupiravir,and azvudine),while the other four are protease inhibitors(nirmatrelvir,ensitrelvir,leritrelvir,and simnotrelvir-ritonavir).Antiviral resistance,unfavourable drug‒drug interaction,and toxicity have been reported in previous *** there is a dearth of new treatment options for *** this work,a three-tier cell-based screening was employed to identify novel compounds with anti-SARS-CoV-2 *** compound,designated 172,demonstrated broad-spectrum antiviral activity against multiple human pathogenic coronaviruses and different SARS-CoV-2 variants of *** studies validated by reverse genetics showed that compound 172 inhibits the 3-chymotrypsin-like protease(3CLpro)by binding to an allosteric site and reduces 3CLpro dimerization.A drug synergistic checkerboard assay demonstrated that compound 172 can achieve drug synergy with nirmatrelvir in *** vivo studies confirmed the antiviral activity of compound 172 in both Golden Syrian Hamsters and K18 humanized ACE2 ***,this study identified an alternative druggable site on the SARS-CoV-23CLpro,proposed a potential combination therapy with nirmatrelvir to reduce the risk of antiviral resistance and shed light on the development of allosteric protease inhibitors for treating a range of coronavirus diseases.

关键词： SARS-CoV-2 High throughput screening Broad-spectrum antiviral treatment 3CLpro inhibitor Allosteric-site inhibitor Animal models Chemical genetics Reverse genetics

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Atomic level engineering of noble metal nanocrystals for energy conversion catalysis

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Journal of Energy Chemistry 2021年第12期30卷 604-624,I0014页

作者： Yancai Yao Shiqi Wang Zhijun Li yuen Wua School of Chemistry and Materials Science iChEM(Collaborative Innovation Center of Chemistry for Energy Materials)Hefei National Laboratory for Physical Sciences at the MicroscaleUniversity of Science and Technology of ChinaHefei 230026AnhuiChina School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Joint International Research Laboratory of Advanced Chemical Catalytic Materials&Surface Science College of Chemistry and Chemical EngineeringNortheast Petroleum UniversityDaqing 163318HeilongjiangChina

It is commonly known that the performance of electrocatalysts is largely influenced by the size,morphology,composition,and crystalline phase of noble metal ***,the limited reserves and high cost of noble metals largely restrict their industrial *** with the development of characterization techniques,theoretical calculations,and advanced material synthesis methods,modulating the electrocatalytic properties of noble metal nanocrystals at the atomic scale(e.g.,monolayer/sub-monolayer,single-atom alloy,ultrafine structure)has been flooding *** noble metal nanocrystals at the atomic level could not only immensely improve the noble metal atom utilization efficiency and lower the cost,but also boost the catalytic *** this review,we summarize the recent advanced progresses of regulating the noble metal nanocrystals at the atomic scale towards energy conversion ***,the challenges and perspectives of designing noble metal nanocrystals at the atomic scale in the future are discussed and *** is expected that this review will inspire scientists to further study precious metal-based materials for energy-oriented catalysis.

关键词： Noble metal Atomic regulation Synthetic strategy Electrocatalysis

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