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Room temperature Ⅲ–Ⅴ nanolasers with distributed Bragg reflectors epitaxially grown on(001) silicon-on-insulators

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Photonics Research 2019年第9期7卷 1081-1086页

作者： YU HAN WAI KIT NG YING XUE 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

Efficient, scalable, bufferless, and compact Ⅲ–V lasers directly grown on(001)-oriented silicon-on-insulators(SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation of Ⅲ–V telecom nanolaser arrays with integrated distributed Bragg reflectors(DBRs) epitaxially grown on industry-standard(001) SOI wafers. We simulated the mirror reflectance of different guided modes under various mirror architectures, and accordingly devised nanoscale DBR gratings to support high reflectivity around1500 nm for the doughnut-shaped TE01 mode. Building from InP/InGaAs nanoridges grown on SOI, we fabricated subwavelength DBR mirrors at both ends of the nanoridge laser cavities and thus demonstrated room-temperature low-threshold InP/InGaAs nanolasers with a 0.28 μm^2 cross-section and a 20 μm effective cavity length. The direct growth of these bufferless nanoscale Ⅲ–V light emitters on Si-photonics standard(001) SOI wafers opens future options of fully integrated Si-based nanophotonic integrated circuits in the telecom wavelength regime.

关键词： InGaAs InP SOI nanolasers with distributed Bragg reflectors epitaxially grown on Room temperature silicon-on-insulators Bragg

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

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.

The Pioneering Works of Professor Duzheng YE on Atmospheric Dispersion,Tibetan Plateau Meteorology,and Air–Sea Interaction

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Advances in Atmospheric Sciences 2017年第10期34卷 1137-1149页

作者： Ngar-Cheung lau Institute of Environment Energy and Sustainabilityand Department of Geography and Resource ManagementThe Chinese University of Hong KongShatinN.T.Hong Kong

This paper provides an overview of the impacts of the original works of Professor Duzheng YE on a selected set of observational and model studies with which the present author has been associated over the past several decades. The main themes of these works include atmospheric energy dispersion, air–land interactions over the Tibetan Plateau, and El Ni n？orelated air–sea coupling over East *** dispersive behavior of observed atmospheric fluctuations accompanying cold surge events in East Asia is demonstrated. Cold air outbreaks over Korea and southern China are coincident with the successive downstream development of troughs and ridges, with the group velocity of such wave packets being notably faster than the phase propagation speed of individual troughs and ridges. In a more general context, dispersive features are also discernible from lagged teleconnection charts and cross-spectra of observed and model-simulated geopotential height variations on 10–30-day time *** the output from a high-resolution general circulation model, the relative contributions of condensational, sensible, and radiative heating to the atmospheric energy budget over the Tibetan Plateau are documented. The rapid changes of the upper tropospheric Tibetan anticyclone and East Asian mei-yu（＂plum rain＂） precipitation band associated with the development of the Asian monsoon system are *** principal anomalies in sea level pressure, surface wind, precipitation and sea surface temperature over southeastern China and the Philippine Sea region during El Nio events are presented. The contributions of remote El Nio-related forcing and local air–sea interaction to the occurrence of these anomalies are assessed.

关键词： atmospheric dispersion Tibetan Plateau meteorology El Nio

New tricyanoiron(Ⅲ) building blocks for the construction of molecule-based magnets

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Science China Chemistry 2010年第10期53卷 2106-2111页

作者： lau Pui-Ha WONG Wing-Tak lau Tai-Chu Department of Biology and Chemistry City University of Hong Kong Department of Chemistry The University of Hong Kong

A series of tricyanoiron(Ⅲ) complexes with the general formula mer-[FeⅢ(5-Xsap)(CN)3]2-(X = H, Me, MeO, Cl or Br, sapH2 = N-salicylidene-o-aminophenol) have been synthesized. These complexes were characterized by IR, ESI-MS, UV/Vis, elemental analysis and magnetic measurements. The structures of (PPh4)2[FeⅢ(sap)(CN)3] and (PPh4)2[FeⅢ(5-Mesap)(CN)3] have been determined by X-ray crystallography. These low-spin d5 tricyanoiron(Ⅲ) complexes are potential building blocks for the construction of molecule-based magnets.

关键词： cyano iron Schiff base building block molecule-based magnet

Flow behavior and deposition study of pollen-shape carrier particles in an idealized inhalation path model

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Particuology 2010年第1期8卷 51-59页

作者： Meer Saiful Hassan Raymond lau School of Chemical and Biomedical Engineering (SCBE) Nanyang Technological University (NTU)

Pollen-shape （spiked sphere） hydroxyapatite （HA） particles for drug carrier application are studied. The particle shape and size effect on flow characteristics and deposition are assessed. The pollen-shape HA particles are synthesized to have comparable size as typical carrier particles with mean diameter of 30-50 μm and effective density less than 0.3 g/cm^3. The flow behaviors of HA and commonly used lactose （LA） carrier particles are characterized by the Carr＇s compressibility index （CI）. The HA particles have lower CI than the LA particles for the same size range. The flow fields of HA and LA carrier particles are measured in an idealized inhalation path model using particle image velocimetry （PLY） technique. The particle streamlines indicate that a large portion of particles may deposit at the bending section due to inertial impaction and gravitational deposition. The flow field result shows that HA particles give smaller separation regions than the LA particles for the same size range. The pollen-shape HA particles are found to be able to follow the gas flow in the model and minimize undesired deposition. Deposition result confirms the bending section to have the most deposition. Deposition is found to be a function of particle properties. An empirical correlation is derived for the deposition efficiency of the pollen-shape particles as a function of particles Stokes number.

关键词： Aerosol Fluid mechanics Multiphase flow Particle Powder technology Pulmonary drug delivery

Associating liver partition and portal vein ligation for staged hepatectomy： the current role and development

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Hepatobiliary & Pancreatic Diseases International 2017年第1期16卷 17-26页

作者： Wan Yee lau Eric CH Lai Stephanie HY lau Faculty of Medicine The Chinese University of Hong Kong Shatin New Territories Department of Surgery Pamela Youde Nethersole Eastern Hospital Department of Surgery Queen Elizabeth Hospital Hong Kong China

BACKGROUND： Associating liver partition and portal vein ligation for staged hepatectomy （ALPPS） has recently been developed to induce rapid liver hypertrophy and reduce posthepatectomy liver failure in patients with insufficient future liver remnant （FLR）. ALPPS is still considered to be in an early developmental phase because surgical indications and techniques have not been standardized. This article aimed to review the current role and future developments of ALPPS. DATA SOURCES： Studies were identified by searching MED- LINE and PubMed for articles from January 2007 to October 2016 using the keywords ＂associating liver partition and portal vein ligation for staged hepatectomy＂ and ＂ALPPS＂ Addi- tional papers were identified by a manual search of references from key articles. RESULTS： ALPPS induces more hypertrophy of the FLR in less time than portal vein embolization or portal vein ligation. The benefits of ALPPS include rapid hypertrophy 47%-110% of the liver over a median of 6-16.4 days, and 95%-100% com- pletion rate of the second stage of ALPPS. The main criticisms of ALPPS are centered on its high morbidity and mortality rates. Morbidity rates after ALPPS have been reported to be 15.3%-100%, with ≥ the Clavien-Dindo grade III morbidity of 13.6%-44%. Mortality rates have been reported to be 0%-29%. The important questions to ask even if oncologic long-term results are acceptable are： whether the gain in quality and quantity of life can be off balance by the substantial risks of morbidity and mortality, and whether stimulation of rapid liver hypertrophy also accelerates rapid tumor progression and spread. Up till now, the documentations of the ALPPS procedure come mainly from case series, and most of these series include heterogeneous groups of malignancies. The numbers are also too small to separately evaluate survival for different tumor etiologies. CONCLUSIONS： Currently, knowledge on ALPPS is limited, and prospective randomized studies are lacking. From th

关键词： associating liver partition and portal vein ligation for staged hepatectomy portal vein embolization laparoscopy colorectal liver metastases hepatocellular carcinoma

Efficient chemoenzymatic synthesis of complex carbohydrates

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Efficient chemoenzymatic synthesis of complex carbohydrates

Current therapy of hilar cholangiocarcinoma

中国化学会第27届学术年会

作者：陈希 kam lau Go Sugiarto Department of Chemistry University of California-Davis One Shields Avenue

＜正＞Sialic acids are a family of nine-carbon monosaccharides mainly found as the terminal residues of glycans on cell surfaces （1）. More than 50 structurally distinct sialic acids have been

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Hepatobiliary & Pancreatic Diseases International 2012年第1期11卷 12-17页

作者： Stephanie Hiu Yan lau Wan Yee lau Faculty of Medicine The Chinese University of Hong Kong

BACKGROUND: Hilar cholangiocarcinoma (HC) is an adeno-carcinoma of the extrahepatic biliary tree arising from the main left or right hepatic ducts or their confluence. This tumor is still considered to be difficult to treat or to cure. DATA SOURCES: We reviewed the medical literature on HC. Relevant and updated information on this tumor was analyzed in a concise and easy-to-read manner. The article is not intended to be a systematic review, but an extensive search was conducted on PubMed and MEDLINE using the keywords 'hilar cholangiocarcinoma' and 'Klatskin tumor' until July 2011. RESULTS: The selection and the timing of management options for patients with HC are determined by the degree of certainty of the diagnosis, the general condition of the patients, the underlying liver function and the stage of the disease. Current treatment of HC can be divided into curative and palliative treatment. For the curative treatment, local excision should only be used on small tumors which are confined to the bile duct wall and Bismuth I papillary carcinoma. Partial hepatectomy should be combined with caudate lobe resection and porta-hepatis lymph node dissection. The results of these major resections can be improved with portal vein embolization, and staging laparoscopy and laparoscopic ultrasound. The role of preoperative biliary drainage is controversial. Autotransplantation for HC gave disappointing results while the Mayo Protocol of chemoradiation for selecting patients with unresectable HC for orthotopic liver transplantation has been widely accepted. Palliative treatment included bypass surgery, endoscopic or percutaneous stenting, photodynamic therapy, intraluminal brachytherapy, and external radiation and systemic therapy. CONCLUSIONS: Adequate surgery with R0 resection should be the main goal of treatment. For patients with unresectable HC, treatment aims to improve the quality and quantity of their survival.

关键词： hilar cholangiocarcinoma Klatskin tumor resection liver transplantation palliative treatment