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MULTIFRACTAL STRUCTURE AND PRODUCT OF MATRICES

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Analysis in Theory and Applications 2003年第4期19卷 289-311页

作者： lau ka-sing Department of Mathematics Chinese University of Hong Kong

There is a well established multifractal theory for self-similar measures generated by non-overlapping contractive similutudes. Our report here concerns those with overlaps. In particular we restrict our attention to the important classes of self-similar measures that have matrix representations. The dimension spectra and the L q -spectra are analyzed through the product of matrices. There are abnormal behaviors on the multifractal structure and they will be discussed in detail.

关键词： multifractal self-similar measure iterated function system dimension spectra

Geodesic metrics on fractals and applications to heat kernel estimates

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Science China Mathematics 2023年第5期66卷 907-934页

作者： Qingsong Gu ka-sing lau Hua Qiu Huo-Jun Ruan Department of Mathematics Nanjing UniversityNanjing 210093China Department of Mathematics The Chinese University of Hong KongHong KongChina Department of Mathematics University of PittsburghPittsburghPA 15217USA School of Mathematical Sciences Zhejiang UniversityHangzhou 310027China

It is well known that for a Brownian motion, if we change the medium to be inhomogeneous by a measure μ, then the new motion(the time-changed process) will diffuse according to a different metric D(·, ·).In 2009, Kigami initiated a general scheme to construct such metrics through some self-similar weight functions g on the symbolic space. In order to provide concrete models to Kigami’s theoretical construction, in this paper,we give a thorough study of his metric on two classes of fractals of primary importance: the nested fractals and the generalized Sierpinski carpets;we further assume that the weight functions g := ga are generated by“symmetric” weights a. Let M be the domain of a such that Dgadefines a metric, and let S be the boundary of M. One of our main results is that the metrics from ga satisfy the metric chain condition if and only if a ∈ *** determine M and S, we provide a recursive weight transfer construction on the nested fractals, and a basic symmetric argument on the Sierpinski carpet. As an application, we use the metric chain condition to obtain the lower estimate of the sub-Gaussian heat kernel. This together with the upper estimate obtained by Kigami allows us to have a concrete class of metrics for the time change, and the two-sided sub-Gaussian heat kernel estimate on the fundamental fractals.

关键词： Brownian motion heat kernel metric chain condition nested fractal quasisymmetry resistance metric Sierpinski carpet weight function

Gut microbiota in cancer initiation,development and therapy

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Science China Life Sciences 2025年

作者： Ruyi Zhang Xiang Zhang Harry Cheuk Hay lau Jun Yu Institute of Digestive Disease and Department of Medicine and Therapeutics State Key Laboratory of Digestive DiseaseLi Ka Shing Institute of Health SciencesCUHK Shenzhen Research InstituteThe Chinese University of Hong Kong

Cancer has long been associated with genetic and environmental factors,but recent studies reveal the important role of gut microbiota in its initiation and *** 13%of cancers are linked to infectious agents,highlighting the need to identify the specific microorganisms *** microbiota can either promote or inhibit cancer growth by influencing oncogenic signaling pathways and altering immune *** can lead to cancer,while certain probiotics and their metabolites may help reestablish microecological balance and improve anti-tumor immune *** into targeted approaches that enhance therapy with probiotics is ***,the effects of probiotics in humans are complex and not yet fully ***,methods to counteract harmful bacteria are still in *** clinical trials also indicate that modifying gut microbiota may help manage side effects of cancer *** research is crucial to understand better how gut microbiota can be used to improve cancer prevention and treatment outcomes.

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Monolithic full-color active-matrix micro-LED microdisplay using InGaN/AlGaInP heterogeneous integration

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Light(Science & Applications) 2023年第11期12卷 2459-2467页

作者： Longheng Qi Peian Li Xu Zhang ka Ming Wong Kei May lau Department of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

A prototype of full-color active-matrix micro-light-emitting diode(micro-LED)micro-display with a pixel density of 391 pixel per inch(ppi)using InGaN/AlGaInP heterogeneous integration is *** blue/green dual-color micro-LED arrays realized on a single metal organic chemical vapor deposition(MOCVD)-grown GaN-on-Si epiwafer and AlGaInP red micro-LED arrays are both monolithically fabricated,followed by the integration with a common complementary metal oxide semiconductor(CMOS)backplane via flip-chip bonding technology to form a doublelayer thin-film display ***-color images with decent color gamut and brightness are successfully displayed through the fine adjustment of driving current densities of RGB *** full-color display combines the advantages of high quantum efficiency of InGaN material on blue/green light and AlGaInP material on red light through heterogeneous integration and high pixel density through monolithic fabrication approach,demonstrating the feasibility and prospects of high brightness,good color performance,and high-resolution micro-LED microdisplays in future metaverse applications.

关键词： AlGaInP integration matrix

Lack of evidence of active lytic replication of Epstein-Barr and cytomegaloviruses in patients with systemic lupus erythematosus

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Chinese Medical Journal 1998年第7期000卷 84-89页

作者： lau Chak sing, Yuen Yung, Chan Hung and Wong Raymond Woon sing Division of Rheumatology The University of Hong Kong Queen Mary Hospital Hong Kong China Department of Medicine and Department of Microbiology The University of Hong Kong Queen Mary Hospital Hong Kong China

Objectives Systemic lupus erythematosus (SLE) is a multifactorial disease. Environmental factors such as viral infection(s) have been proposed as pathaetiological factors. There are particular interests in studying lymphotropic viruses such as the Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Although previous case reports and in vitro studies suggested that they may have a role, there is no direct evidence that onset of SLE or disease exacerbation is associated with active infection by these viruses. Using the very sensitive polymerase chain reaction (PCR) technique, we tried to find out evidence of active replication of these viruses in patients with SLE. Methods Thirty-four patients with SLE were compared with matched normal controls. Eleven patients were newly diagnosed to have SLE and 18 of the 34 patients had active disease as determined by a SLE Disease Activity Index (SLEDAI) score of ≥10 at the time of study. Results Our results showed no evidence of active replication or reactivation of EBV in the leucocytes amongst the newly diagnosed SLE patients, established SLE patients, patients with SLEDAI ≥10, patients with SLEDAI <10, and control subjects. There was no evidence of CMV infection in any of the subjects studied. The IgG and IgA responses against EBV early antigen (EA) and viral capsid antigen (VCA) were also studied. The IgG and IgA responses against VCA of EBV were increased in patients with SLE when compared with controls. However, there were no differences in these responses among different subgroups of patients. The mechanism of these responses was not apparent but may represent non-specific hyperimmune responses in these patients. There were no differences in the titre of IgG and IgA against EBV EA between the patient groups and *** There is no direct evidence that either EBV or CMV plays a direct role in the onset and/or exacerbation of SLE.

关键词： Lack of evidence of active lytic replication of Epstein-Barr and cytomegaloviruses in patients with systemic lupus erythematosus

A monolithic InP/SOI platform for integrated photonics

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Light(Science & Applications) 2021年第11期10卷 2143-2152页

作者： Zhao Yan Yu Han Liying Lin Ying Xue Chao Ma Wai Kit Ng kam sing Wong Kei May lau Department of Electronic and Computer Engineering Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Department of Physics and William Mong Institute of Nano Science and Technology Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

The deployment of photonic integrated circuits(PICs)necessitates an integration platform that is scalable,high-throughput,cost-effective,and *** we present a monolithic InP on SOI platform to synergize the advantages of two mainstream photonic integration platforms:Si photonics and InP *** monolithic InP/SOI platform is realized through the selective growth of both InP sub-micron wires and large dimension InP membranes on industry-standard(001)-oriented silicon-on-insulator(SOI)*** epitaxial InP is in-plane,dislocation-free,site-controlled,intimately positioned with the Si device layer,and placed right on top of the buried oxide layer to form“InP-on-insulator”.These attributes allow for the realization of various photonic functionalities using the epitaxial InP,with efficient light interfacing between the III-V devices and the Si-based *** exemplify the potential of this InP/SOI platform for integrated photonics through the demonstration of lasers with different cavity designs including subwavelength wires,square cavities,and *** results here mark a critical step forward towards fully-integrated Si-based PICs.

关键词： SOI monolithic integration

Residential building performance analysis at near extreme weather conditions in Hong Kong through a thermal-comfort-based strategy

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Building Simulation 2023年第1期16卷 13-25页

作者： K.F.Fong C.K.Lee Kevin ka-Lun lau Edward Yan Yung Ng Division of Building Science and Technology College of EngineeringCity University of Hong KongHong KongChina Department of Civil Engineering and Natural Resources Lulea University of TechnologySweden School of Architecture The Chinese University of Hong KongHong KongChina

The precise building performance assessment of residential housings in subtropical regions is usually more difficult than that for the commercial premises due to the much more complicated behavior of the occupants with regard to the change in indoor *** conventional use of a fixed schedule for window opening,clothing insulation and cooling equipment operation cannot reflect the real situation when the occupants respond to the change in thermal comfort,thus affecting the appropriateness of the assessment *** rectify the situation,a new modeling strategy in which the modification of the various operation schedules was based on the calculated thermal comfort(TC),was developed in this *** this new TC-based strategy,the realistic building performances under different cooling provision scenarios applied to a high-rise residential building under the near extreme weather conditions were investigated and *** was found that sole provision of ventilation fans could not meet the zone thermal comfort by over 68%of the time,and air-conditioning was *** optimal use of ventilation fans for cooling could only help reduce the total cooling energy demand by less than 12%at best which could only be realistically evaluated by adopting the present *** studies were conducted which revealed that some design factors could offer opportunities for reducing the total cooling energy under the near extreme weather conditions.

关键词： predicted mean vote thermal comfort ventilation potential building performance simulation residential housings

Substitute of Expensive Pt with Improved Electrocatalytic Performance and Higher Resistance to CO Poisoning for Methanol Oxidation: the Case of Synergistic Pt-Co_3O_4 Nanocomposite

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Nano-Micro Letters 2013年第4期5卷 296-302页

作者： Hongxiao Zhao Zhi Zheng Jing Li Huimin Jia ka-wai Wong Yidong Zhang Woon Ming lau Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province Institute of Surface Micro and Nano Materials Xuchang University Chengdu Green Energy and Green Manufacturing R&D Center

In this paper, Pt-Co_3O_4 nanocomposite was synthesized by a sol gel process combined with electrodeposition method. Its electrocatalytic activity towards methanol oxidation was investigated at room temperature using cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and current density time curve. It is found that the resultant Pt-Co_3O_4 catalysts with minute amount of Pt exhibite attractive electrocatalytic activity for methanol oxidation reaction(MOR) but with a high resistance CO poisoning due to the synergistic effects from Pt and Co_3O_4. Together with the low manufacturing cost of Co_3O_4, the reported nanostructured Pt-Co_3O_4 catalyst is expected to be a promising electrode material for direct methanol fuel cells(DMFC).

关键词： Pt-Co3O4 nanocomposite MOR Electrocatalytic activity

Role of external counterpulsation in the treatment of ischemic stroke

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Journal of Geriatric Cardiology 2010年第2期7卷 88-92页

作者： Jing-Hao Han Wai-Hong Leung ka-sing Wong Departments of Medicine ＆ Therapeutics The Chinese University of Hong Kong Shatin Hong Kong SAR

Reduced blood flow is the principle pathophysiologic event in acute ischernic ***,flow augmentation is the most important goal in stroke *** of cerebral blood flow can be accomplished by proximal arterial recanalization or by other systemic *** counterpulsation is a non-invasive method to improve the perfusion of heart,kidneys and *** review summarizes the history,possible mechanism and the role of external counterpulsation in ischemic stroke.

关键词： ischemic stroke external counterpulsation cerebral blood flow cerebral perfusion