Edge perturbation on electronic properties of boron nitride nanoribbons

K.L. Wong,K.W. Lai,M.W. Chuan,Y. Wong,A. Hamzah,S. Rusli,N.E. Alias,S. Mohamed Sultan,C.S. Lim,M.L.P. Tan Techno-Press 2023 Advances in nano research Vol.15 No.5

Hexagonal boron nitride (h-BN), commonly referred to as Boron Nitride Nanoribbons (BNNRs), is an electrical insulator characterized by high thermal stability and a wide bandgap semiconductor property. This study delves into the electronic properties of two BNNR configurations: Armchair BNNRs (ABNNRs) and Zigzag BNNRs (ZBNNRs). Utilizing the nearest-neighbour tight-binding approach and numerical methods, the electronic properties of BNNRs were simulated. A simplifying assumption, the Hamiltonian matrix is used to compute the electronic properties by considering the self-interaction energy of a unit cell and the interaction energy between the unit cells. The edge perturbation is applied to the selected atoms of ABNNRs and ZBNNRs to simulate the electronic properties changes. This simulation work is done by generating a custom script using numerical computational methods in MATLAB software. When benchmarked against a reference study, our results aligned closely in terms of band structure and bandgap energy for ABNNRs. However, variations were observed in the peak values of the continuous curves for the local density of states. This discrepancy can be attributed to the use of numerical methods in our study, in contrast to the semi-analytical approach adopted in the reference work.

Irradiation time-dependent study of eggshell-derived hydroxyapatite powder synthesized by microwave-assisted wet chemical precipitation method

K.W. Goh,Y.H. Wong,R.S.K. Singh,Hari Chandran,S.K. Wong,K.Y. Sara Lee 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

The extraction of calcium from natural biowaste material such as chicken eggshells have been shown to be viable to synthesiscalcium phosphate bioceramic. In this work, eggshell-derived hydroxyapatite powder was synthesised by using the wetchemical precipitation technique coupled with microwave irradiation at low power (700 W) at varying exposure time from 5to 30 min. The derived nano-powders were examined to determine the phases present, chemical bonding and microstructuralevolution. It was revealed that the irradiation time has an effect on the degree of crystallinity and both the crystallite andparticle size of the derived powders although the hydroxyapatite phase stability was not disrupted. An exposure time of 15 min. was determined to be sufficient when subjected to low power microwave irradiation to formed a well-defined needle-likehydroxyapatite particles having an average crystallite size of about 22 nm. On the contrary to many literatures, this study hasdemonstrated the viability of synthesizing a useful bioceramic from using biowaste eggshells coupled with microwaveirradiation at low power of 700 W for very short period of time to produce nano-range needle-like hydroxyapatite particlessuitable for biomedical application.

Enhancement of Excretory Production of an Exoglucanase from Escherichia coli with Phage Shock Protein A (PspA) Overexpression

( Y. Y. Wang ),( Z. B. Fu ),( K. L. Ng ),( C. C. Lam ),( A. K. N. Chan ),( K. F. Sze ),( W. K. R. Wong ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.6

Production of recombinant proteins by excretory expression has many advantages over intracellular expression in Escherichia coli. Hyperexpression of a secretory exoglucanase, Exg, of Cellulomonas fimi was previously shown to saturate the SecYEG pathway and result in dramatic cell death of E. coli. In this study, we demonstrated that overexpression of the PspA in the JM101(pM1VegGcexL-pspA) strain enhanced excretion of Exg to 1.65 U/ml using shake-flask cultivation, which was 80% higher than the highest yield previously obtained from the optimized JM101(pM1VegGcexL) strain. A much higher excreted Exg activity of 4.5 U/ml was further achieved with high cell density cultivation using rich media. Furthermore, we showed that the PspA overexpression strain enjoyed an elevated critical value (CV), which was defined as the largest quotient between the intracellular unprocessed precursor and its secreted mature counterpart that was still tolerable by the host cells prior to the onset of cell death, improving from the previously determined CV of 20/80 to the currently achieved CV of 45/55 for Exg. The results suggested that the PspA overexpression strain might tolerate a higher level of precursor Exg making use of the SecYEG pathway for secretion. The reduced lethal effect might be attributable to the overexpressed PspA, which was postulated to be able to reduce membrane depolarization and damage. Our findings introduce a novel strategy of the combined application of metabolic engineering and construct optimization to the attainment of the best possible E. coli producers for secretory/excretory production of recombinant proteins, using Exg as the model protein.

Structural health rating (SHR)-oriented 3D multi-scale finite element modeling and analysis of Stonecutters Bridge

Y.Q. Ni,X.F. Li,K.Y. Wong,K.W.Y. Chan 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.1

The Stonecutters Bridge (SCB) in Hong Kong is the third-longest cable-stayed bridge in the world with a main span stretching 1,018 m between two 298 m high single-leg tapering composite towers. A Wind and Structural Health Monitoring System (WASHMS) is being implemented on SCB by the Highways Department of The Hong Kong SAR Government, and the SCB-WASHMS is composed of more than 1,300 sensors in 15 types. In order to establish a linkage between structural health monitoring and maintenance management, a Structural Health Rating System (SHRS) with relevant rating tools and indices is devised. On the basis of a 3D space frame finite element model (FEM) of SCB and model updating, this paper presents the development of an SHR-oriented 3D multi-scale FEM for the purpose of load-resistance analysis and damage evaluation in structural element level, including modeling, refinement and validation of the multi-scale FEM. The refined 3D structural segments at deck and towers are established in critical segment positions corresponding to maximum cable forces. The components in the critical segment region are modeled as a full 3D FEM and fitted into the 3D space frame FEM. The boundary conditions between beam and shell elements are performed conforming to equivalent stiffness, effective mass and compatibility of deformation. The 3D multi-scale FEM is verified by the in-situ measured dynamic characteristics and static response. A good agreement between the FEM and measurement results indicates that the 3D multi-scale FEM is precise and efficient for WASHMS and SHRS of SCB. In addition, stress distribution and concentration of the critical segments in the 3D multi-scale FEM under temperature loads, static wind loads and equivalent seismic loads are investigated. Stress concentration elements under equivalent seismic loads exist in the anchor zone in steel/concrete beam and the anchor plate edge in steel anchor box of the towers.

Species identification of Dyers woad leaf by DNA sequence of 5S-rRNA spacer domain and random amplified polymorphic DNA (RAPD) analysis

Zhao, K.J.,Dong, T.T.X.,Wong, Y.C.,Tu, P.F.,Tsim, K.W.K. Kyung Hee Oriental Medicine Research Center 2005 Oriental pharmacy and experimental medicine Vol.5 No.2

Dyers woad leaf (Daqingye) is a traditional Chinese medicine commonly used as anti-pyretic, anti-bacterial and anti-viral agent against infectious diseases. The Chinese Pharmacopoeia (2005) records that Dyers woad leaf should be derived from the leaves of Isatis indigotica Fort., but the leaves of Polygonum tinctorium Ait., Baphicacanthus cusia (Nees) Bremek. and Clerodendron cyrtophyllum Turcz. have also been used as substitutes of Dyers woad leaf in different regions of China. The leaf morphologies of these four species show a close resemblance, and based on their morphological appearance, it is difficult to identify them. Here, molecular genetic methods were developed as a target to identify different members of Dyers woad leaf. The 5S-rRNA spacer domain was amplified by polymerase chain reaction from genomic DNAs isolated from I. indigotica, P. tinctorium, B. cusia and C. cyrtophyllum, and the nucleotide sequences showed a great diversity. In addition, random amplification of polymorphic DNA analysis was also used to distinguish the members of Dyers woad leaf. These molecular methods could be used as a tool in authentic identification of Dyers woad leaf.

Indium oxide, tin oxide and indium tin oxide nanostructure growth by vapor deposition

M.K. Fung,K.K. Wong,X.Y. Chen,Y.F. Chan,A.M.C. Ng,A.B. Djurišić,W.K. Chan 한국물리학회 2012 Current Applied Physics Vol.12 No.3

Indium oxide, tin oxide and indium tin oxide nanowires have been grown by vapor deposition on Si and quartz substrates. Under the growth conditions used, pure SiOx nanowires, a mixture of SiOx and indium oxide, tin oxide or indium tin oxide nanostructures, or pure indium oxide, tin oxide or indium tin oxide nanostructures could be obtained at different substrate temperatures. The growth mechanism of the obtained nanostructures at different substrate temperatures is discussed. Optical and electrical properties of the deposited pure indium oxide, tin oxide or indium tin oxide nanostructures have been measured, and low sheet resistances on quartz substrates have been obtained for indium oxide and indium tin oxide nanostructures.

Field measurement results of Tsing Ma suspension Bridge during Typhoon Victor

Xu, Y.L.,Zhu, L.D.,Wong, K.Y.,Chan, K.W.Y. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.10 No.6

A Wind and Structural Health Monitoring System (WASHMS) has been installed in the Tsing Ma suspension Bridge in Hong Kong with one of the objectives being the verification of analytical processes used in wind-resistant design. On 2 August 1997, Typhoon Victor just crossed over the Bridge and the WASHMS timely recorded both wind and structural response. The measurement data are analysed in this paper to obtain the mean wind speed, mean wind direction, mean wind inclination, turbulence intensity, integral scale, gust factor, wind spectrum, and the acceleration response and natural frequency of the Bridge. It is found that some features of wind structure and bridge response are difficult to be considered in the currently used analytical process for predicting buffeting response of long suspension bridges, for the Bridge is surrounded by a complex topography and the wind direction of Typhoon Victor changes during its crossing. It seems to be necessary to improve the prediction model so that a reasonable comparison can be performed between the measurement and prediction for long suspension bridges in typhoon prone regions.

Predicting the next turn at road junction from big traffic data

Zhuang, Y.,Fong, S.,Yuan, M.,Sung, Y.,Cho, K.,Wong, R. K. Kluwer Academic Publishers 2017 The Journal of supercomputing Vol.73 No.7

<P>Smart city is an emerging research field nowadays, with emphasis of using big data to enhance citizens' quality of life. One of the prevalent smart city projects is to use big traffic data collected from road users over time, for road planning, traffic light scheduling, traffic jam relief, and public security. In particular, being able to know a road user's current location and predict his/her next move is important in today's intelligent transportation systems. Trajectory prediction has become a prudential research study direction, by which many algorithms have been published before. In this paper, we present a simple probabilistic model which predicts road users' next locations based on the 'concept of segments' abstracted from historical trails which the users have taken and accumulated over time in some data archive. Given a trajectory and a current location, the road user's next move in terms of road direction can be predicted at the junction. It is found that each road user would have his/her unique travel pattern hidden in the aggregate big traffic data. These patterns could be modeled from connected segments for simplicity. With the longer the trail and more frequently this trail was travelled, the more accurate that the next turn can be predicted. Simulation experiment was conducted based on summing up the segments from empirical trajectory data that was used in trajectory data mining by Microsoft. The results of our alternative model in contrast to the state of the arts demonstrated good efficacy.</P>

Triple Negative Status is a Poor Prognostic Indicator in Chinese Women with Breast Cancer: a Ten Year Review

Ma, K.K.,Chau, Wai Wang,Wong, Connie H.N.,Wong, Kerry,Fung, Nicholas,Lee, J.T. Andrea,Choi, L.Y. Catherine,Suen, Dacita T.K.,Kwong, Ava Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.5

Background: Ethnic variation in tumor characteristics and clinical presentation of breast cancer is increasingly being emphasized. We studied the tumor characteristics and factors which may influence the presentation and prognosis of triple negative breast cancers (TNC) in a cohort of Chinese women. Methods: A prospective cohort of 1800 Chinese women with breast cancer was recruited in a tertiary referral unit in Hong Kong between 1995 and 2006 and was followed up with a median duration of 7.2 years. Of the total, 216 (12.0%) had TNC and 1584 (88.0%) had non-TNC. Their clinicopathological variables, epidemiological variables and clinical outcomes were evaluated. Results: Patients with TNC had similar age of presentation as those with non-TNC, while presenting at earlier stages (82.4% were stage 1-2, compared to 78.4% in non-TNC, p=0.035). They were likely to be associated with grade 3 cancer (Hazard Ratio(HR)=5.8, p<0.001). TNC showed higher chance of visceral relapse (HR=2.69, p<0.001), liver metastasis (HR=1.7, p=0.003) and brain metastasis (HR=1.8, p=0.003). Compared with non-TNC group, TNC had similar 10-year disease-free survival (82% vs 84%, p=0.148), overall survival (78% vs 79%, p=0.238) and breast cancer-specific mortality (18% vs 16%, p=0.095). However, TNC showed poorer 10-year stage 3 and 4 specific survival (stage 3: 53% vs. 67%, p=0.010; stage 4: 0% vs. 40%, p=0.035). Conclusions: Chinese women with triple negative breast cancer do not have less aggressive biological behavior compared to the West and presentation at a later stage results in worse prognosis compared with those with non triple negative breast cancer.

The Efficacy of Herbal Supplement Danggui Buxue Tang for Relieving Menopausal Symptoms

( Eliza L. Y. Wong ),( Annie W. L. Cheung ),( C. J. Haines ),( C. C. Wang ),( Chun-kwok Wong ),( Karl W. K. Tsim ),( William K. F. Cheng ),( Ping-chung Leung ) 대한폐경학회 2022 대한폐경학회지 Vol.28 No.1

Objectives: This study aimed to further explore the efficacy and safety of Danggui Buxue Tang (DBT), a simple herbal formula, for improving the quality of life of women suffering from menopausal symptoms. Methods: A third clinical trial to determine the clinical efficacy of high-dose DBT for a period of 12 weeks was carried out. The standard Menopause-Specific Quality of Life (MENQOL) assessment chart was used for the evaluation. Safety was defined as an absence of direct estrogenic effects, serum inflammatory cytokines. Notably, interleukin IL-6, IL-8 and tumor necrosis factor TNF-α, known to be directly related to estrogenic reactions in menopause studies, were monitored. Results: The third clinical trial indicated an overall improvement in the four domains of MENQOL, offering further proof of the efficacy of DBT demonstrated in the two previous trials. The serial checks of the three cytokines related to estrogen activities did not show either upward or downward trends. The haphazard behavior reactions of the three cytokines offered indirect indications that DBT improved the MENQOL independently from estrogen activities. Conclusions: The three clinical trials using DBT to relieve menopausal syndrome have offered solid evidence for its efficacy. The uncertainty regarding whether the “phytoestrogen” contained in DBT had bioactivities similar to estrogen was alleviated through the confirmation that no strict estrogenic bioactivities were observed. The issue of safety was further clarified via laboratory platform studies on DBT, which not only showed the lack of similarity with estrogen actions but also confirmed the value of combining the two herbs in the classic formula.