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Wong, K.L.,Chuan, M.W.,Chong, W.K.,Alias, N.E.,Hamzah, A.,Lim, C.S.,Tan, M.L.P. Techno-Press 2019 Advances in nano research Vol.7 No.3
Graphene, with impressive electronic properties, have high potential in the microelectronic field. However, graphene itself is a zero bandgap material which is not suitable for digital logic gates and its application. Thus, much focus is on graphene nanoribbons (GNRs) that are narrow strips of graphene. During GNRs fabrication process, the occurrence of defects that ultimately change electronic properties of graphene is difficult to avoid. The modelling of GNRs with defects is crucial to study the non-idealities effects. In this work, nearest-neighbor tight-binding (TB) model for GNRs is presented with three main simplifying assumptions. They are utilization of basis function, Hamiltonian operator discretization and plane wave approximation. Two major edges of GNRs, armchair-edged GNRs (AGNRs) and zigzag-edged GNRs (ZGNRs) are explored. With single vacancy (SV) defects, the components within the Hamiltonian operator are transformed due to the disappearance of tight-binding energies around the missing carbon atoms in GNRs. The size of the lattices namely width and length are varied and studied. Non-equilibrium Green's function (NEGF) formalism is employed to obtain the electronics structure namely band structure and density of states (DOS) and all simulation is implemented in MATLAB. The band structure and DOS plot are then compared between pristine and defected GNRs under varying length and width of GNRs. It is revealed that there are clear distinctions between band structure, numerical DOS and Green's function DOS of pristine and defective GNRs.
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.
침의 치료기전에 대한 신경기반 및 신경기능 가설 -침자극과 관계된 신경기반 및 체액성 반응, 신경적 반응, 면역반응-
조장희,황선출,손영돈,강창기,박태석,배선준,성강경,Cho, Z.H,Hwang, S.C,Wong, E.K.,Son, Y.D,Kang, C.K,Park, T.S,Bai, S.J,Sung, K.K 대한침구의학회 2003 대한침구의학회지 Vol.20 No.5
Acupuncture therapy has demonstrated efficacy in several clinical areas, and of these areas the understanding of pain has progressed immensely in the last two decades. The underlying mechanisms of acupuncture in general and the analgesic effect in particular are still not clearly delineated. The leading hypothesis include the effects of local stimulation, neuronal gating, release of endogenous opiates, and the placebo effect. Accumulating evidence suggests that the central nervous system(CNS) is essential for the processing of these effects, via its modulation of the autonomic nervous system, neuro-immune system, and hormonal regulation. These processes tap into basic survival mechanisms. As such, understanding the effects of acupuncture within a neuroscience-based framework becomes vital. We propose a model which incorporates the stress-induced hypothalamus-pituitary-adrenal axis(HPA-axis) model of Akil et al., the cholinergic anti-inflamatory observations of Tracey et al., and Petrovic et al.
Molecular Surveillance Identifies Multiple Transmissions of Typhoid in West Africa
Wong, Vanessa K.,Holt, Kathryn E.,Okoro, Chinyere,Baker, Stephen,Pickard, Derek J.,Marks, Florian,Page, Andrew J.,Olanipekun, Grace,Munir, Huda,Alter, Roxanne,Fey, Paul D.,Feasey, Nicholas A.,Weill, F Public Library of Science 2016 PLoS neglected tropical diseases Vol.10 No.9
<▼1><P><B>Background</B></P><P>The burden of typhoid in sub-Saharan African (SSA) countries has been difficult to estimate, in part, due to suboptimal laboratory diagnostics. However, surveillance blood cultures at two sites in Nigeria have identified typhoid associated with <I>Salmonella enterica</I> serovar Typhi (<I>S</I>. Typhi) as an important cause of bacteremia in children.</P><P><B>Methods</B></P><P>A total of 128 <I>S</I>. Typhi isolates from these studies in Nigeria were whole-genome sequenced, and the resulting data was used to place these Nigerian isolates into a worldwide context based on their phylogeny and carriage of molecular determinants of antibiotic resistance.</P><P><B>Results</B></P><P>Several distinct <I>S</I>. Typhi genotypes were identified in Nigeria that were related to other clusters of <I>S</I>. Typhi isolates from north, west and central regions of Africa. The rapidly expanding <I>S</I>. Typhi clade 4.3.1 (H58) previously associated with multiple antimicrobial resistances in Asia and in east, central and southern Africa, was not detected in this study. However, antimicrobial resistance was common amongst the Nigerian isolates and was associated with several plasmids, including the IncHI1 plasmid commonly associated with <I>S</I>. Typhi.</P><P><B>Conclusions</B></P><P>These data indicate that typhoid in Nigeria was established through multiple independent introductions into the country, with evidence of regional spread. MDR typhoid appears to be evolving independently of the haplotype H58 found in other typhoid endemic countries. This study highlights an urgent need for routine surveillance to monitor the epidemiology of typhoid and evolution of antimicrobial resistance within the bacterial population as a means to facilitate public health interventions to reduce the substantial morbidity and mortality of typhoid.</P></▼1><▼2><P><B>Author Summary</B></P><P>Typhoid fever, a serious bloodstream infection caused by the bacterium <I>Salmonella</I> Typhi, is a major cause of disease and death around the world. There have been limited data on the epidemiology of typhoid in many countries in sub-Saharan African, including Nigeria. Recent evidence, however, showed that typhoid was an important cause of bacteraemia in children residing in two regions of Nigeria. Here, we analyzed the whole genome sequences of 128 <I>S</I>. Typhi isolates from two studies in order to elucidate the population structure and characterize the genetic components of antimicrobial resistance. We found that the multiple <I>S</I>. Typhi genotypes identified were closely related to other <I>S</I>. Typhi from neighboring regions of Africa and that multidrug resistance (MDR) was common among these isolates, and in many cases was associated with the IncHI1 plasmid known to cause MDR typhoid. These results provide evidence that typhoid was established in Nigeria as a result of several independent introductions into the country and that there has been extensive exchange of <I>S</I>. Typhi in and around the region of West Africa. This study emphasizes the importance of surveillance to improve our understanding of the epidemiology of typhoid, which is needed to underpin public health measures to reduce the spread of disease and facilitate patient management.</P></▼2>
Kim, D.K.,Incecik, A.,Choi, H.S.,Wong, E.W.C.,Yu, S.Y.,Park, K.S. Elsevier 2018 Ocean engineering Vol.157 No.-
<P><B>Abstract</B></P> <P>In the present study, an innovative method for estimating fatigue performance of risers under vortex-induced vibration (VIV) is proposed. Generally, fatigue performance is affected by the surrounding environment such as wind, wave, and current. It is well known that current is the most influential load among all for offshore risers. In structural safety aspect, strength and fatigue are the most important factors for riser design. In addition, fatigue design is affinitive to the VIV phenomenon. For the analysis of fatigue performance of riser, SHEAR7 numerical simulation code which is commonly used in offshore industry is applied. In order to identify the relation between current load and fatigue performance of riser, Fatigue damage versus Current index (F-C) diagram has been proposed. F-C diagram may cover change of current profiles and help predict the fatigue damage under VIV. In case of current profile, a total of sixty cases of current scenarios are considered based on six representative sea-states. The obtained results from this study will be a useful guideline to predict the effect of current on the fatigue performance of riser.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An innovative method for the estimation of fatigue performance of offshore riser is proposed. </LI> <LI> Current index (CI) concept is proposed by considering the parameters of current profile. </LI> <LI> F-C (Fatigue damage vs. Current index) diagrams for offshore riser are established. </LI> <LI> The proposed method shows good agreement with existing method. </LI> <LI> The F-C diagrams will be useful in judging the safety level of offshore riser subjected to VIV fatigue by current load. </LI> </UL> </P>