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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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Microcurvature landscapes induce neural stem cell polarity and enhance neural differentiation

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Bio-Design and Manufacturing 2023年第5期6卷 522-535页

作者： ho-yin yuen Wai-Sze Yip Suet To Xin Zhao Department of Biomedical Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARChina State Key Laboratory of Ultra-Precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARChina

Tissue curvature has long been recognized as an important anatomical parameter that affects intracellular behaviors,and there is emerging interest in applying cell-scale curvature as a designer property to drive cell fates for tissue engineering *** neural cells are known to undergo dramatic and terminal morphological changes during development and curvature-limiting behaviors have been demonstrated in neurite outgrowth studies,there are still crucial gaps in understanding neural cell behaviors,particularly in the context of a three-dimensional(3D)curvature landscape similar to an actual tissue engineering *** this study,we fabricated two substrates of microcurvature(curvature-substrates)that present a smooth and repeating landscape with focuses of either a concave or a convex *** these curvature-substrates,we studied the properties of morphological differentiation in N2a neuroblastoma *** contrast to other studies where two-dimensional(2D)curvature was demonstrated to limit neurite outgrowth,we found that both the concave and convex substrates acted as continuous and uniform mechanical protrusions that significantly enhanced neural polarity and differentiation with few morphological changes in the main cell *** enhanced differentiation was manifested in various properties,including increased neurite length,increased nuclear displacement,and upregulation of various neural *** demonstrating how the micron-scale curvature landscape induces neuronal polarity,we provide further insights into the design of biomaterials utilizing the influence of surface curvature in neural tissue engineering.

关键词： Curvature Neural differentiation Neurite outgrowth Mechanotransduction

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Going below and beyond the surface: Microneedle structure, materials, drugs, fabrication, and applications for wound healing and tissue regeneration

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Bioactive Materials 2023年第9期27卷 303-326页

作者： Shang Lyu Zhifei Dong Xiaoxiao Xu ho-Pan Bei ho-yin yuen Chung-Wai James Cheung Man-Sang Wong Yong He Xin Zhao Department of Biomedical Engineering The Hong Kong Polytechnic UniversityHung HomHong Kong SARPR China Faculty of Science University of WaterlooWaterlooOntarioCanada State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhouPR China

Microneedle, as a novel drug delivery system, has attracted widespread attention due to its non-invasiveness, painless and simple administration, controllable drug delivery, and diverse cargo loading capacity. Although microneedles are initially designed to penetrate stratum corneum of skin for transdermal drug delivery, they, recently, have been used to promote wound healing and regeneration of diverse tissues and organs and the results are promising. Despite there are reviews about microneedles, few of them focus on wound healing and tissue regeneration. Here, we review the recent advances of microneedles in this field. We first give an overview of microneedle system in terms of its potential cargos (e.g., small molecules, macromolecules, nucleic acids, nanoparticles, extracellular vesicle, cells), structural designs (e.g., multidrug structures, adhesive structures), material selection, and drug release mechanisms. Then we briefly summarize different microneedle fabrication methods, including their advantages and limitations. We finally summarize the recent progress of microneedle-assisted wound healing and tissue regeneration (e.g., skin, cardiac, bone, tendon, ocular, vascular, oral, hair, spinal cord, and uterine tissues). We expect that our article would serve as a guideline for readers to design their microneedle systems according to different applications, including material selection, drug selection, and structure design, for achieving better healing and regeneration efficacy.

关键词： Microneedles Microfabrication Wound healing Tissue regeneration Drug delivery

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Lamotrigine-induced hemophagocytic lymphohistiocytosis associated with takotsubo cardiomyopathy, renal failure, encephalitis, and hemorrhagic shock

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World Journal of Emergency Medicine 2025年第1期16卷 88-90页

作者： Ariella Gartenberg Juan Esteban Munoz Eusse Alexander Petrie Tsui yuen Department of Emergency Medicine Jacobi Medical Center and Montefi ore Medical CenterBronx 10461USA Department of Emergency Medicine Jacobi Medical Center and North Central Bronx HospitalBronx 10461USA

Hemophagocytic lymphohistiocytosis (HLH) is an aggressive and often fatal overactivation of the immune system. It is characterized by inappropriate and dysregulated activation of natural killer (NK) cells, CD8^(+)cytotoxic T cells, and macrophages. Ineffective interactions between NK cells, CD8^(+)T cells, and their pathogenic targets lead to massive cytokine accumulation and widespread macrophage activation. Resultant hemophagocytosis and excessive organdamaging infl ammation subsequently *** may be triggered by genetic or sporadic disorders,as well as specific events that alter immune *** events include inflammatory or infectious disease processes and malignancy.

关键词： histiocytosis phagocytic homeostasis

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Psychometric properties of the Chinese-version Behavioral Inhibition System/Behavioral Activation System Scales among stroke survivors with depressive symptoms

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International Journal of Nursing Sciences 2025年第1期12卷 74-80页

作者： Dan Shi yuen Yu Chong Lijuan Zhou ho Yu Cheng The Nethersole School of Nursing Faculty of MedicineThe Chinese University of Hong KongHong KongChina Nursing Department The Affiliated Taizhou People’s Hospital of Nanjing Medical UniversityTaizhouJiangsu ProvinceChina

Objective:This study aimed to examine the reliability and validity of the Chinese version of the Behavioral Inhibition System/Behavioral Activation System(BIS/BAS)scales among stroke ***:The cross-sectional study was conducted at four comprehensive hospitals in Taizhou,Jiangsu,China.A sample of 232 first-ever stroke survivors were recruited from June to August *** was examined using face validity and construct validity,which used confirmatory factor analysis(CFA)and known-group *** was evaluated by internal consistency and test-retest ***:The BIS/BAS scales demonstrated satisfactory face *** findings of CFAs supported the original four-factor structure of BAS-reward,BAS-drive,BAS-fun seeking,and BIS with acceptable model fit *** validity,assessed via known-group analysis,indicated that stroke survivors with probable depression had significantly lower mean BAS-reward,BAS-drive,and BAS-fun seeking scores(Phose without probable *** internal consistency,measured by Cronbach’s a coefficients for the subscales,ranged from 0.669 to ***-retest reliability,assessed using intra-class correlation coefficients,ranged from 0.61 to ***:The Chinese version of the BIS/BAS scales could be a reliable and valid instrument for measuring behavioral activation among stroke survivors.

关键词： Behavior Depression Reliability Stroke Validity

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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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Exact joint laws associated with spectrally negative Levy processes and applications to insurance risk theory

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Frontiers of Mathematics in China 2014年第6期9卷 1453-1471页

作者： Chuancun yin Kam C. yuen School of Mathematical Sciences Qufu Normal University Qufu 273165 China Department of Statistics and Actuarial Science The University of Hong Kong Hong KongChina

We consider the spectrally negative L@vy processes and determine the joint laws for the quantities such as the first and last passage times over a fixed level, the overshoots and undershoots at first passage, the minimum, the maximum, and the duration of negative values. We apply our results to insurance risk theory to find an explicit expression for the generalized expected discounted penalty function in terms of scale functions. Furthermore, a new expression for the generalized Dickson＇s formula is provided.

关键词： Fluctuation identity spectrally negative L6vy processes supremaand infima generalized Dickson's formula scale function occupation time

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Alternative Approach to the Optimality of the Threshold Strategy for Spectrally Negative Lvy Processes

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Acta Mathematicae Applicatae Sinica 2013年第4期29卷 705-716页

作者： ying SHEN Chuan-cun yin Kam Chuen yuen School of Mathematical Sciences Qufu Normal UniversityChina Department of Statistics and Actuarial Science The University of Hong Kong

Consider the optimal dividend problem for an insurance company whose uncontrolled surplus precess evolves as a spectrally negative Levy process. We assume that dividends are paid to the shareholders according to admissible strategies whose dividend rate is bounded by a constant. The objective is to find a dividend policy so as to maximize the expected discounted value of dividends which are paid to the shareholders until the company is ruined. In this paper, we show that a threshold strategy （also called refraction strategy） forms an optimal strategy under the condition that the Levy measure has a completely monotone density.

关键词： Spectrally negative Levy process optimal dividend problem scale function complete monotonic-ity threshold strategy

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Optimal Investment and Premium Control in a Nonlinear Diffusion Model

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Acta Mathematicae Applicatae Sinica 2017年第4期33卷 945-958页

作者： Ming ZhoU Kam Chuen yuen Chuan-cun yin China Institute for Actuarial Science Central University of Finance and Economics Department of Statistics and Actuarial Science the University of Hong Kong School of Statistics Qufu Normal University

This paper considers the optimal investment and premium control problem in a diffusion approxi- mation to a non-homogeneous compound Poisson process. In the nonlinear diffusion model, it is assumed that there is an unspecified monotone function describing the relationship between the safety loading of premium and the time-varying claim arrival rate. Hence, in addition to the investment control, the premium rate can be served as a control variable in the optimization problem. Specifically, the problem is investigated in two cases：（i） maximizing the expected utility of terminal wealth, and （ii） minimizing the probability of ruin respectively. In both cases, some properties of the value functions are derived, and closed-form expressions for the optimal policies and the value functions are obtained. The results show that the optimal investment policy and the optimal premium control policy are dependent on each other. Most interestingly, as an example, we show that the nonlinear diffusion model reduces to a diffusion model with a quadratic drift coefficient when the function associated with the premium rate and the claim arrival rate takes a special form. This example shows that the model of study represents a class of nonlinear stochastic control risk model.

关键词： CARA utility dependent control policies Hamilton-Jacobi-Bellman (HJB) equation investment premium control

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Flat-end tool orientation based on rotation-minimizing frame

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Advances in Manufacturing 2019年第3期7卷 257-269页

作者： Xiang Zou hon-yuen Tam Hai-yin Xu Ke Shi School of Computer Science and Technology Huazhong University of Science and TechnologyWuhan 430074People's Republic of China College of Science and Engineering Department of Mechanical EngineeringCity University of Hong KongHong KongPeople's Republic of China

Well-designed tool orientation is crucial for the quality execution of five-axis machining with flat-end *** orientation can be specified in terms of tool inclination and tool tilt *** a given surface path,these aspects need to be specified for each cutter contact point along the path,because poor tool orientation choice can cause large axial acceleration of the machine tool,leading to inferior quality of the machined *** rotation-minimizing frame aims to reduce unnecessary frame rotation during *** concept has been adopted to develop tool orientation methods that allow variation in the inclination angle,the tilt angle,and both the inclination and tilt *** intention is to reduce unnecessary rotation of the tool frame as the tool follows a specified *** was conducted in the context of five-axis flat-end tool *** on these methods,tool orientation was planned along surface paths of a torus,sphere,and *** in tool orientation were always *** the perspective of reducing tool orientation changes and axial acceleration,it was demonstrated that simultaneous variation of the inclination and tilt angles based on rotation minimization provided the best results.

关键词： Five-axis machining Tool orientation Rotation-minimizing frame Numerical control

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