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Measurements of Heat Treatment Effects on Bovine Cortical Bones by Nanoindentation and Compression Testing

Journal of Biomaterials and Nanobiotechnology 2012年第1期3卷 105-113页

作者： mei-ling lau Kin-tak lau Harry Ku Debes Bahattacharyya Yan-dong Yao Centre for Advanced Composite Materials Department of Mechanical Engineering The University of Auckland Auckland New Zealand Centre of Excellence in Engineered Fibre Composites Faculty of Engineering and Surveying University of Southern Queensland Toowoomba Australia Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic University Hong Kong China

Heat treatment of bone is one of the reliable and simple sterilization methods to overcome the risk of rejection and disease transfer from allograft and xenograft, in particular for the prevention of human immunodeficiency virus (HIV) infection. However, the mechanical property of the micro-structural level after heat treatment is not well characterized. To address this issue, this study was carried out to compare the localized mechanical properties of micro-structural tissue with those at the global structural level. Nanoindentation technique has been well accepted as an accurate technique to measure mechanical property of small and heterogeneous specimen nondestructively, as well as the complex bio-material of micro-structural level, often with a resolution of better than 1 μm. In this study, nanoindentation was conducted to measure the localised elastic modulus and hardness values of bones at temperature of 23°C (room temperature – non-heated sample), 90°C and 150°C, respectively. All experiments were conducted at room temperature (~23°C). The elastic modulus (E) and nanoindentation hardenss (H) values in the longitudinal direction of bones heated at 150°C were recorded as 23.43 GPa and 0.73 GPa, respectively;as in transverse direction, the E and H values were 12.77 GPa and 0.54 GPa, respectively. It showed significant increases of 44% and 43% in the longitudinal direction as compared to those of the non heat-treated bones. In addition, E and H values in transverse direction also showed increases of 23% and 38%, respectively as compared to those of the non heat-treated bones. Furthermore, heat-treated bones at 90°C in longitudinal direction also appeared to have significant increases of 18% and 31% in E and H values, respectively. However, the E and H values in transverse direction increase only by 0.4% and 12.8%, respectively. In addition, compressive test is employed to measure the global stiffness (E) of the bone samples. When heated at 150°C, the bone specime

关键词： Bone Heat Treatment Nanoindentation Mechanical Properties BSE and EDX

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Root exclusion methods for partitioning of soil respiration:Review and methodological considerations

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Pedosphere 2023年第5期33卷 683-699页

作者： mei-Yee CHIN Sharon Yu ling lau Frazer MIDOT Mui Sie JEE mei Lieng LO Faustina E.SANGOK Lulie MELling Sarawak Tropical Peat Research Institute Lot 6035Kuching-Kota Samarahan ExpresswayKota SamarahanSarawak 94300Malaysia

Soil respiration is a vital process in all terrestrial ecosystems,through which the soil releases carbon dioxide(CO_(2))into the atmosphere at an estimated annual rate of 68–101 Pg carbon,making it the second highest terrestrial contributor to carbon *** soil respiration consists of autotrophic and heterotrophic constituents,methods for accurately determining the contribution of each constituent to the total soil respiration are critical for understanding their differential responses to environmental factors and aiding the reduction of CO_(2)*** to its low cost and simplicity,the root exclusion(RE)technique,combined with manual chamber measurements,is frequently used in field studies of soil respiration ***,RE treatments alter the soil environment,leading to potential bias in respiration *** review aims to elucidate the current understanding of RE,i.e.,trenching(Tr)and deep collar(DC)insertion techniques,by examining soil respiration partitioning studies performed in several ***,we discuss methodological considerations when using RE and the combinations of RE with stable isotopic and modeling ***,future research directions for improving the Tr and DC insertion methods in RE are suggested.

关键词： autotrophic respiration deep collar insertion heterotrophic respiration microbial respiration root trenching soil microbial community soil respirationcomponent

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Recent Advances in Directed Assembly of Nanowires or Nanotubes

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Nano-Micro Letters 2012年第3期4卷 142-153页

作者： mei Liu Zhizheng Wu Woon Ming lau Jun Yang School of Mechatronics Engineering and Automation Shanghai University State Key Laboratory of Transducer Technology Shanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences Green Energy and Green Manufacturing Technology R&D Center Department of Mechanical and Materials Engineering the University of West ern Ontario

Nanowires and nanotubes of diverse material compositions,properties and/or functions have been produced or fabricated through various bottom-up or top-down *** nanowires or nanotubes have also been utilized as potential building blocks for functional *** key for the integration of those nanowire or nanotube based devices is to assemble these one dimensional nanomaterials to specific locations using techniques that are highly controllable and *** such techniques should enable assembly of highly uniform nanowire/nanotube arrays with precise control of density,location,dimension or even material types of nanowires/*** assembly techniques are being developed that can quickly align and assemble large quantities of one type or multiple types of nanowires through parallel processes,including flow-assisted alignment,Langmuir-Blodgett assembly,bubble-blown technique,electric/magnetic-field directed assembly,contact/roll printing,knocking-down,etc..With these assembling techniques,applications of nanowire/nanotube based devices such as flexible electronics and sensors have been *** paper delivers an overall review of directed nanowire/nanotube assembling approaches and analyzes advantages and limitations of each *** future research directions have also been discussed.

关键词： Nanowire Nanotube Assembly Shear force Contact printing Dielectrophoresis Microfluidics Nanosystems Nanodevices

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Pheromone Static Routing Strategy for Complex Networks

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Chinese Physics Letters 2012年第12期29卷 254-257页

作者： HU Mao-Bin Henry Y.K.lau ling Xiang JIANG Rui Department of Industrial and Manufacturing Systems Engineering The University of Hong KongPokfulam RoadHong Kong School of Engineering Science University of Science and Technology of ChinaHefei 230026 School of Transportation Engineering Hefei University of TechnologyHefei 230009

We adopt the concept of using pheromones to generate a set of static paths that can reach the performance of global dynamic routing strategy[***.E 81(2010)016113].The path generation method consists of two *** the first stage,a pheromone is dropped to the nodes by packets forwarded according to the global dynamic routing *** the second stage,pheromone static paths are generated according to the pheromone *** output paths can greatly improve traffic systems'overall capacity on different network structures,including scale-free networks,small-world networks and random *** the paths are static,the system needs much less computational resources than the global dynamic routing strategy.

关键词： network networks Complex

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Exogenous neural stem cell transplantation for cerebral ischemia

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Neural Regeneration Research 2019年第7期14卷 1129-1137页

作者： ling-Yi Liao Benson Wui-Man lau Dalinda Isabel Sánchez-Vidana Qiang Gao Department of Rehabilitation Medicine West China HospitalSichuan University Department of Rehabilitation Sciences The Hong Kong Polytechnic University

Cerebral ischemic injury is the main manifestation of stroke,and its incidence in stroke patients is 70–80%.Although ischemic stroke can be treated with tissue-type plasminogen activator,its time window of effectiveness is ***,the incidence of paralysis,hypoesthesia,aphasia,dysphagia,and cognitive impairment caused by cerebral ischemia is *** tissue regeneration can promote the recovery of the aforementioned *** stem cells can participate in the reconstruction of the damaged nervous system and promote the recovery of nervous function during self-repair of damaged brain *** stem cell transplantation for ischemic stroke has been a hot topic for more than 10 *** review discusses the treatment of ischemic stroke with neural stem cells,as well as the mechanisms of their involvement in stroke treatment.

关键词： nerve regeneration stem cell therapy neural stem cells cell transplantation ischemic stroke cerebral ischemia neuroplasticity functional recovery neural regeneration

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Biocomposites:Their multifunctionality

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International Journal of Smart and Nano Materials 2010年第1期1卷 13-27页

作者： Kin-tak lau mei-po Ho Chi-ting Au-Yeung Hoi-yan Cheung Centre of Excellence in Engineered Fibre Composites Faculty of Engineering and SurveyingUniversity of Southern QueenslandQueenslandAustralia Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina

During the last decade,tissue engineering has shown a considerable promise in providing more viable alternatives to surgical procedures for harvested tissues,implants and *** to the fast development on nano-and biomaterial technologies,it is now possible for doctors to use patients’cells to repair orthopaedic defects such as focal articular cartilage *** order to support the three-dimensional tissue formation,scaffolds made by biocompatible and bioresorbable polymers and composite materials,for providing temporary support of damaged body and cell structures,have been developed *** ceramic and metallic materials have been widely accepted for the development of implants,their non-resorbability and necessity of second surgical operation(like for bone repair),which induce extra pain for the patients,limit their wide *** development of different types of biocomposites for biomedical engineering applications is *** biocomposites include(i)basic biomaterials;(ii)natural fiber-reinforced biocomposites and(iii)nanoparticle-reinforced *** multifunctionality is discussed in terms of the control of mechanical properties,biodegradability and bioresorbability.

关键词： multifunctional materials biocomposite

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Efficient photocatalytic reduction of CO2 to formate by a molecular noble metal-free system

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Science China Chemistry 2025年第1期 152-156页

作者： Lihua Zhang lingjing Chen Huatian Shi Yue Wei Gui Chen Tai-Chu lau School of Environment and Civil Engineering Research Center for Eco-environmental Engineering Dongguan University of Technology Department of Chemistry and Institute of Molecular Functional Materials City University of Hong Kong

Reducing CO2to carbon-neutral solar fuels can not only alleviate the energy demand but also mitigate the greenhouse *** present,developing an efficient non-noble metal photo/electrocatalytic system for converting CO2to a specific product beyond CO is still a big ***,we report a new cobalt complex bearing 2,2′-bi-1,10-phenanthroline ligand that can photocatalytically reduce CO2to formate （HCOO-）.Turnover number （TON） for HCOO-up to 677 with 99%selectivity can be achieved using organic dyes purpurin as photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole （BIH） as sacrificial reductant in a CO2-saturated NMP/TEA （v/v,3:1） solution under visible light *** potential electrolysis at-1.41 V （***/Ag Cl） in the presence of 12 m M Et3NHBF4also produced HCOO-with Faradaic efficiency of 39%.Spectroscopic and electrochemical studies suggest that a[CoI-H]species is the key intermediate for CO2reduction.

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Comparison of methods for determining orthotropic axes in 3D femur remodeling

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Progress in Natural Science:Materials International 2007年第12期17卷 1405-1411页

作者： lau Jaclyn Beijing 100084 China Department of Biomedical Engineering Tsinghua University

The density distribution and internal structure of trabecular bone are modulated by local mechanical environment. In this study, an orthotropic adaptation algorithm was applied to the 3D femur model to simulate the variations of stiffness and orientation of trabecular bone under multi-loading conditions. This algorithm includes the determination of orthotropic axes and the stiffness modification of trabecular bone. Three methods were used to determine the orthotropic axes, i.e. the maximal cycle method, the stress maximum method, and the composite method. We found that the composite method was better than the other two. Firstly, the characteristics of density distribution obtained by using the composite method agreed better with those in real proximal femur. Secondly, the material orientation aligned with the known trabeculaer pattern. Finally, the ratios of the longitudinal modulus to the transverse modulus were also shown to be realistic in three local regions of the proximal femur.

关键词： orthotropic axes trabecular bone adaptation algorithm stiffness variation.

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Improved breakdown voltage of AlGaN/GaN HEMTs grown on Si substrates using partially Mg-doped GaN buffer layer by MOCVD

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Science China(Physics,Mechanics & Astronomy) 2010年第9期53卷 1578-1581页

作者： lau KeiMay Photonics Technology Center Department of Electronic and Computer EngineeringHong Kong University of Science and Technology

AlGaN/GaN high electron mobility transistors(HEMTs) were grown on Si substrates by *** the HEMT structure,a 1 μm GaN buffer layer was partially doped with Mg in an attempt to increase the resistivity and minimize the buffer *** AlGaN/GaN HEMTs grown on undoped and partially Mg-doped GaN buffer layers were processed and the DC characteristics of the devices were characterized for comparing the effect of Mg *** the device with the partially Mg-doped GaN buffer layer,a lower drain leakage current density of 55.8 nA/mm,a lower gate leakage current density of 2.73 μA/mm,and a higher off-state breakdown voltage of 104 V were achieved with device dimensions Lg/Wg/Lgs/Lgd=1/10/1/1 μm,better than the device with the undoped GaN buffer layer,which has a higher drain leakage current density of 9.2 μA/mm,a higher gate leakage current density of 91.8 μA/mm,and a lower off-state breakdown voltage of 87 V with the same device dimensions.

关键词： AlGaN/GaN HEMT Si substrate MOCVD breakdown voltage Mg-doped

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RADIATION BOUNDARY CONDITIONS FOR MAXWELL'S EQUATIONS:A REVIEW OF ACCURATE TIME-DOMAIN FORMULATIONS

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Journal of Computational Mathematics 2007年第3期25卷 305-336页

作者： Thomas Hagstrom Stephen lau Department of Mathematics and Statistics University of New MexicoAlbuquerqueNM 87131USA Division of Applied Mathematics Brown University182 George StreetProvidenceRI 02912USA

We review time-domain formulations of radiation boundary conditions for Maxwell＇s equations, focusing on methods which can deliver arbitrary accuracy at acceptable compu-tational cost. Examples include fast evaluations of nonlocal conditions on symmetric and general boundaries, methods based on identifying and evaluating equivalent sources, and local approximations such as the perfectly matched layer and sequences of local boundary conditions. Complexity estimates are derived to assess work and storage requirements as a function of wavelength and simulation time.

关键词： Maxwell's equations Radiation boundary conditions Fast algorithms Kirchoffformulas Perfectly matched layers.

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