115 results on '"Kong, Yong"'
Search Results
2. Hypoxic-Mediated Oxidative Stress Condition and Hydroxyapatite-Inducing Osteogenic Differentiation of Human Mesenchymal Stem Cells: A Mathematical Modeling Study
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Bala Sundaram Muthuvenkatachalam, Yu Sheng Qiu, Qiong Wu, Palanisamy Arulselvan, Guo Zhong He, Akon Higuchi, Sanjiv Rampal, K. B. Swamy, Rajan Mariappan, Pooi Ling Mok, Yan Chao Cui, Seoh Wei Teh, S. Suresh Kumar, Gang Bu, Zhong Sun, Kong Yong Then, Kok Pian Ang, and Antony V. Samrot
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Cellular differentiation ,0206 medical engineering ,Nonunion ,Biomedical Engineering ,Pharmaceutical Science ,Medicine (miscellaneous) ,Bioengineering ,Avascular necrosis ,02 engineering and technology ,Tissue engineering ,Osteogenesis ,Bone cell ,medicine ,Humans ,General Materials Science ,Femur ,business.industry ,Mesenchymal stem cell ,Cell Differentiation ,Mesenchymal Stem Cells ,Models, Theoretical ,021001 nanoscience & nanotechnology ,medicine.disease ,020601 biomedical engineering ,Oxidative Stress ,Durapatite ,Cancer research ,Stem cell ,0210 nano-technology ,business - Abstract
Avascular necrosis (AVN) of the bones remains a major clinical challenge. Fractures in the talus, the scaphoid, and the neck of the femur are especially challenging to heal due to the low blood vessel network and the lack of collateral blood supply. These fractures are associated with high rates of nonunion and increased infections that require repeated operations. Conventional treatments by autografting or allografting bone replacement and synthetic bone implants have limitations, including the invasiveness of operative procedures, tissue supply insufficiency, and the risk of host rejection. The advancement in tissue engineering has revealed the potential of stem cells as restorative agents for bone injuries. The administration of mesenchymal stem cells (MSCs) into the talus, the scaphoid, and the neck of the femur could produce enhanced osteogenesis via the manipulation of MSC culture conditions. In this study, we used hydroxyapatite as the nanomaterial, and hypoxic milieu to enhance MSC differentiation capacity into the osteogenic lineage, allowing for more rapid and efficient bone cell replacement treatment. Our results demonstrate 1% oxygen and 12.5 μg/mL of hydroxyapatite (HAP) as the optimal conditions to incorporate the osteogenic medium for the osteogenic induction of MSCs. We also established a proof of concept that the addition of HAP and hypoxic conditions could augment the osteoinductive capacity of MSCs. We also developed an accurate mathematical model to support future bone cell replacement therapy.
- Published
- 2020
3. Understanding the multifaceted mechanisms of diabetic wound healing and therapeutic application of stem cells conditioned medium in the healing process
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Anjan Das, Lai Woon Fui, Then Kong Yong, Michael Phang Weng Lok, Vijayendran Govindasamy, and Then Khong Lek
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Chemokine ,0206 medical engineering ,Biomedical Engineering ,Medicine (miscellaneous) ,Adipose tissue ,02 engineering and technology ,Bioinformatics ,Diabetes Complications ,Biomaterials ,03 medical and health sciences ,Diabetes mellitus ,medicine ,Animals ,Humans ,030304 developmental biology ,Wound Healing ,0303 health sciences ,biology ,Mechanism (biology) ,business.industry ,Mesenchymal stem cell ,Mesenchymal Stem Cells ,medicine.disease ,020601 biomedical engineering ,Transplantation ,Culture Media, Conditioned ,biology.protein ,Intercellular Signaling Peptides and Proteins ,Wounds and Injuries ,Stem cell ,Wound healing ,business - Abstract
Mesenchymal stem cells (MSCs) transplantation seems to be a promising new therapy for diabetic wound healing (DWH), and currently, arrays of MSCs from various sources ranging from umbilical, adipose to dental sources are available as a treatment modality for this disease. However, it now appears that only a fraction of transplanted cells actually assimilate and survive in host tissues suggesting that the major mechanism by which stem cells participate in tissue repair are most likely related to their secretome level. These include a wide range of growth factors, cytokines, and chemokines, which can be found from the conditioned medium (CM) used to culture the cells. Basic studies and preclinical work confirm that the therapeutic effect of CMs are comparable with the application of stem cells. This review describes in detail the wound healing process in diabetes and the cellular and biological factors that influence the process. Subsequently, through a comprehensive literature search of studies related to wound healing in diabetics, we aim to provide an overview of scientific merits of using MSCs-CM in the treatment of diabetic wound as well as the significant caveats, which restricts its potential use in clinical set-ups. To our best knowledge, this is one of the first review papers that collect the importance of stem cells as an alternative treatment to the DWH. We anticipate that the success of this treatment will have a significant clinical impact on diabetic wounds.
- Published
- 2019
4. Decreased Nonlinear Harmonic Generation in Longitudinal Leaky SAW Resonators Based on YZ-cut LiNbO3 Substrate
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Yook-Kong Yong and Xiangnan Pang
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Materials science ,business.industry ,Surface acoustic wave ,Lithium niobate ,Harmonic analysis ,Resonator ,chemistry.chemical_compound ,symbols.namesake ,Optics ,chemistry ,Harmonics ,Harmonic ,symbols ,High harmonic generation ,Rayleigh scattering ,business - Abstract
The second (H2) and third (H3) harmonic generations in surface acoustic wave (SAW) resonators based on the YZ-cut LiNbO 3 operating in both longitudinal leaky SAW (LLSAW) mode and Rayleigh SAW mode were investigated and compared. For the Rayleigh SAW mode, the patterns and trends of nonlinearly excited harmonics in the YZ-cut LiNbO 3 were the same as those of 128° YX LiNbO 3 except that the peaks of nonlinear harmonic responses in YZ-cut LiNbO 3 were denser than the latter. However, for the YZ-cut LiNbO 3 LLSAW resonators, the peaks of the nonlinear harmonic responses would be 20 to 30 dBm lower than those in the Rayleigh SAW resonators. For the YZ-cut LiNbO 3 LLSAW resonators, we found that the quasi-periodic peaks in the nonlinear harmonics response would disappear at a substrate thickness of 500 μm. Results showed that the nonlinear harmonic generation concerns in SAW filters and duplexers may be substantially reduced by the use of longitudinal leaky SAW based on YZ-cut LiNbO 3 .
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- 2021
5. Generation and characterization of a humanized anti-IL-17A rabbit monoclonal antibody
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Yi Zhou, Meijuan Wu, Wu Yiliang, Qiu Jiwan, Qiu Zhihua, Li Wang, Chen Wei, Kong Yong, Chen Tao, and Qiao Huaiyao
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Keratinocytes ,Chemokine ,medicine.drug_class ,Chemokine CXCL1 ,Pharmacology ,Monoclonal antibody ,Antibodies, Monoclonal, Humanized ,Autoimmune Diseases ,Mice ,Pharmacokinetics ,In vivo ,medicine ,Animals ,Humans ,Autoimmune disease ,biology ,Chemotactic Factors ,Dose-Response Relationship, Drug ,business.industry ,Interleukin-6 ,Interleukin-17 ,Interleukin-8 ,Biological activity ,medicine.disease ,Macaca mulatta ,In vitro ,biology.protein ,Rabbits ,Antibody ,business ,Biotechnology ,Signal Transduction - Abstract
Interleukin-17A (IL-17A) produced by Th17 cells, contributes to the pathogenesis of various autoimmune diseases by stimulating the release of cytokines and chemokines and its regulation. Anti-IL-17A antibody which blocks the function of IL-17A has been proved to be an effective treatment of autoimmune disease. The aim of our study was to generate a potential humanized anti-IL-17A therapeutic monoclonal antibody (mAb) through a comprehensive panel of in vitro and in vivo biological activity studies, as well as physicochemical characterization. HZD37-5, a humanized monoclonal antibody specifically recognizing N78 loci of IL-17A, binds to human and rhesus monkeys, blocks IL-17 induced signal transduction and the release of IL-6, IL-8, CXCL-1 and G-GSF. In an in vivo efficacy mouse model, HZD37-5 significantly inhibited human IL-17A induced-keratinocyte chemoattractant (KC) secretion in a dose-dependent manner. The pharmacokinetics (PK) study result of HZD37-5 in rhesus monkeys indicated that HZD37-5 had favorable PK characteristics with limited distribution (78.0–78.8 ml/kg), slow elimination (5.00–6.45 ml/day/kg), long half-life (9.1–10.7 days) and high bioavailability (103%) following a single IV or SC dose at 1.5 mg/kg. These findings provided a comprehensive preclinical characterization of HZD37-5 and supported that it may be developed as a potential therapeutic for the treatment of autoimmune diseases, including psoriasis, psoriatic arthritis, axial spondyloarthritis, etc.
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- 2021
6. Spontaneous Corneal Clearance Despite Dislocated Graft after Descemet’s Stripping Automated Endothelial Keratoplasty
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Mae-Lynn Catherine Bastion, Then Kong Yong, and Aina Malindri Dasrilsyah
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medicine.medical_specialty ,business.industry ,Ophthalmology ,medicine ,business ,Stripping (fiber) - Published
- 2020
7. Case series of cultivated oral mucosa epithelium transplantation for limbal stem cell failure
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Ghee Chien Ooi, Aida Zairani Mohd Zahidin, Umi Kalthum Md Noh, Kong Yong Then, Safinaz Mohd Khialdin, and Kah Lay Oh
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medicine.medical_specialty ,Visual acuity ,genetic structures ,business.industry ,Chemical burn ,Corneal Transplant ,Ocular rosacea ,medicine.disease ,eye diseases ,Epithelium ,Transplantation ,Ophthalmology ,medicine.anatomical_structure ,medicine ,Limbal stem cell ,sense organs ,Oral mucosa ,medicine.symptom ,business - Abstract
Purpose: To report a case series of seven eyes (six patients) with severe limbal stem cell failure who underwent cultivated oral mucosa epithelium transplantation (COMET) in preparation for corneal transplant surgery and assess the change in visual acuity postoperatively. Design: Case series. Methods: A retrospective analysis of an interventional case series of six patients with severe limbal stem cell deficiency who underwent COMET between 2012 and 2015 was performed. Six eyes had COMET followed by corneal transplant, and one eye had corneal transplant preceding COMET. The change in the visual acuity after operation was evaluated. Results: A total of six patients with seven eyes were studied. All of them had severe ocular surface disease with limbal stem cell deficiency (LSCD) secondary to chemical injury (five eyes), SJS (one eye), and severe ocular rosacea (one eye). Four eyes had improvements in visual acuity, two of which achieved best corrected visual acuity (BCVA) of 6/12. Conclusion: The use of COMET helps to optimize the ocular surface in severe LSCD for further corneal transplant surgeries. It has helped to improve the graft uptake and subsequent visual improvement, especially in chronic chemical burn cases.
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- 2018
8. Giganteone A and malabaricone C as potential pharmacotherapy for diabetes mellitus
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Kong Yong Loo, Siti Mariam Adbul Wahab, Kok Hoong Leong, Muhamad Aqmal Othman, Khalijah Awang, and Yasodha Sivasothy
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Plant Science ,Pharmacology ,medicine.disease_cause ,01 natural sciences ,Biochemistry ,Analytical Chemistry ,Structure-Activity Relationship ,Pharmacotherapy ,Diabetes mellitus ,medicine ,Diabetes Mellitus ,Humans ,Hypoglycemic Agents ,Glycoside Hydrolase Inhibitors ,Antidiabetic agents ,Glycemic ,010405 organic chemistry ,business.industry ,Organic Chemistry ,Biphenyl Compounds ,alpha-Glucosidases ,Resorcinols ,medicine.disease ,0104 chemical sciences ,Molecular Docking Simulation ,010404 medicinal & biomolecular chemistry ,Malabaricone C ,business ,Oxidative stress - Abstract
The use of antidiabetic agents which control glycemic levels in the blood and simultaneously inhibit oxidative stress is an important strategy in the prevention of Diabetes Mellitus and its complications. In our previous study, malabaricone C (3) and its dimer, giganteone A (5) exhibited significant DPPH free radical scavenging activities which were lower than the activity of the positive control, ascorbic acid. These compounds were evaluated for their α-glucosidase inhibitory activities at different concentrations (0.02–2.5 mM) in the present study. Compounds 3 (IC50 59.61 µM) and 5 (IC50 39.52 µM) were identified as active alpha-glucosidase inhibitors, each respectively being 24 and 37 folds more potent than the standard inhibitor, acarbose. Based on the molecular docking studies, compounds 3 and 5 docked into the active site of the α-glucosidase enzyme, forming mainly hydrogen bonds in the active site.
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- 2021
9. Chronic inflammation involves CCL11 and IL-13 to facilitate the development of liver cirrhosis and fibrosis in chronic hepatitis B virus infection
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Chook Jack Bee, Rosmawati Mohamed, Kok Keng Tee, Muttiah Barathan, Esaki M. Shankar, Hong-Yien Tan, Behnaz Riazalhosseini, Yean-Kong Yong, Yi-Wen Ting, Sui-Weng Wong, Vijayakumar Velu, and Marie Larsson
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0301 basic medicine ,Adult ,Chemokine CCL11 ,Liver Cirrhosis ,Male ,medicine.medical_specialty ,Hepatitis B virus ,Cirrhosis ,Clinical Biochemistry ,medicine.disease_cause ,Gastroenterology ,03 medical and health sciences ,0302 clinical medicine ,Hepatitis B, Chronic ,Fibrosis ,Internal medicine ,Granulocyte Colony-Stimulating Factor ,medicine ,Diabetes Mellitus ,Humans ,Inflammation ,Hepatitis B Surface Antigens ,Interleukin-13 ,business.industry ,Platelet Count ,Fatty liver ,General Medicine ,Middle Aged ,medicine.disease ,Biomechanical Phenomena ,Fatty Liver ,030104 developmental biology ,Liver ,DNA, Viral ,030211 gastroenterology & hepatology ,Female ,Liver function ,Steatosis ,Transient elastography ,business ,Viral load ,Biomarkers - Abstract
The pathogenesis involving non-alcoholic fatty liver disease (NAFLD) in the context of chronic HBV (CHB) virus infection requires to be understood for developing improved modalities of diagnosis and treatment. We retrospectively investigated the association between NAFLD and CHB virus infection in the context of liver fibrosis. Among the 522 consecutive CHB patients who underwent transient elastography between years 2013 and 2016, we studied 455 subjects in the current investigation. Controlled attenuation parameter (CAP) and liver stiffness measurement (LSM) scores were generally higher in patients with steatosis and fibrosis or cirrhosis. Antiviral treatment had significantly reduced the hepatitis B virus (HBV) viral load. Other liver function markers showed a significant positive correlation with both CAP and LSM scores. Plasma IL-13 was independently associated with increased CAP score where every increase of 1 unit of IL-13 was associated with an increase in CAP score by 0.98 unit. CCL11 was independently associated with LSM with every increase of CCL11 by a unit that, in turn, was associated with an increase of LSM score. We found that there was a high concurrence of NAFLD among patients with CHB virus infection. The presence of metabolic syndrome and chronic inflammation in CHB virus-infected patients were two independent factors that led to the progression of liver cirrhosis, with IL-13 playing the key role in linking the metabolic with the inflammatory components.
- Published
- 2021
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10. A FRAMEWORK OF CHALLENGES FACING THE SAFE CITY PROGRAMME IN KUALA LUMPUR
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Chee Kong Yong, Seng Boon Lim, Mohd Fadzil Abdul Rashid, and Jalaluddin Abdul Malek
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Kuala lumpur ,business.industry ,05 social sciences ,Geography, Planning and Development ,Urban policy ,010501 environmental sciences ,Public relations ,01 natural sciences ,Urban Studies ,Crime prevention ,Political science ,0502 economics and business ,Sustainability ,Thematic analysis ,Resilience (network) ,business ,050203 business & management ,0105 earth and related environmental sciences ,Tertiary Prevention - Abstract
The Safe City Programme was launched one and a half-decade ago in Malaysia as one of the National Key Result Areas (NKRAs) strategy to curb crimes. However, the crime rates, in particular in Kuala Lumpur (KL), have shown little evidence of abating. Little is understood of the actual challenges facing the programme. Therefore, questions have been raised and many researchers are attracted to focus on this scenario. Thus, this study aimed to assess local players’ views of the challenges facing the safe city programme in KL and to provide a framework for the prevention strategies. The research involved qualitative in-depth interviews with key players in the area of safe city, crime experts and officials, and community heads. Themes and a framework were formulated through thematic analysis. The results showed that the understanding of a safe city programme could be differentiated through the lens of sustainability and resilience challenges, as well as their levels of prevention. Thus, the grey area of tertiary prevention strategies could be identified and strengthened.
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- 2020
11. Optimal Cut of Quartz Crystal/FeGaB RF Magnetic Sensors
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Yook-Kong Yong and Xiangnan Pang
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0303 health sciences ,Materials science ,business.industry ,020206 networking & telecommunications ,Magnetostriction ,02 engineering and technology ,Substrate (electronics) ,Piezoelectricity ,Crystal ,03 medical and health sciences ,Resonator ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,Thin film ,business ,Quartz ,Excitation ,030304 developmental biology - Abstract
The heterostructures made of magnetostrictive and piezoelectric layers have been recently investigated for the application of magnetic sensors and antenna. In this paper we investigate the possibility of FeGaB thin film on quartz crystal substrate with different orientations of quartz layer. Response of magnetic FeGaB/AlN nanoplate resonator under RF magnetic excitation was simulated by finite element program COMSOL. The results were compared with available experiment and confirmed the validity of available material properties of FeGaB thin film and current simulation method. Quartz/FeGaB composite resonator structures based on different modes of vibration were studied. Quartz/FeGaB resonator based on in-plane extensional modes was found to have a large magnetoelectric coupling effect. These findings can be used to design RF magnetic sensors based on Quartz/FeGaB bilayer plate.
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- 2020
12. High Dose of Intravenous Allogeneic Umbilical Cord-Derived Mesenchymal Stem Cells (CLV-100) Infusion Displays Better Immunomodulatory Effect among Healthy Volunteers: A Phase 1 Clinical Study
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Sze-Piaw Chin, Mohd-Yusoff Mohd-Shahrizal, Mohd-Zuhar Liyana, Kong Yong Then, Soon Keng Cheong, and Kar Wey Yong
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medicine.medical_specialty ,Article Subject ,biology ,business.industry ,medicine.medical_treatment ,Mesenchymal stem cell ,Cell Biology ,RC31-1245 ,Effective dose (pharmacology) ,Umbilical cord ,Gastroenterology ,Proinflammatory cytokine ,Interleukin 10 ,Cytokine ,Interleukin 1 receptor antagonist ,medicine.anatomical_structure ,Internal medicine ,medicine ,biology.protein ,business ,Interleukin 6 ,Molecular Biology ,Research Article - Abstract
Background. Mesenchymal stem cells (MSCs) express growth factors and other cytokines that stimulate repair and control the immune response. MSCs are also immunoprivileged with low risk of rejection. Umbilical cord-derived MSCs (UCMSCs) are particularly attractive as an off-the-shelf allogeneic treatment in emergency medical conditions. We aim to determine the safety and efficacy of intravenous allogeneic infusion of UCMSCs (CLV-100) by Cytopeutics® (Selangor, Malaysia) in healthy volunteers, and to determine the effective dose at which an immunomodulatory effect is observed. Methodology. Umbilical cord samples were collected after delivery of full-term, healthy babies with written consent from both parents. All 3 generations (newborn, parents, and grandparents) were screened for genetic mutations, infections, cancers, and other inherited diseases. Samples were transferred to a certified Good Manufacturing Practice laboratory for processing. Subjects were infused with either low dose (LD, 65 million cells) or high dose (HD, 130 million cells) of CLV-100 and followed up for 6 months. We measured cytokines using ELISA including anti-inflammatory cytokines interleukin 1 receptor antagonist (IL-1RA), interleukin 10 (IL-10), pro-/anti-inflammatory cytokine interleukin 6 (IL-6), and the proinflammatory cytokine tumor necrosis factor-alpha (TNF-α). Results. 11 healthy subjects (LD, n = 5 ; HD, n = 6 ; mean age of 55 ± 13 years) were recruited. All subjects tolerated the CLV-100 infusion well with no adverse reaction throughout the study especially in vital parameters and routine blood tests. At 6 months, the HD group had significantly higher levels of anti-inflammatory markers IL1-RA ( 705 ± 160 vs. 306 ± 36 pg / mL ; p = 0.02 ) and IL-10 ( 321 ± 27 vs. 251 ± 28 pg / m L; p = 0.02 ); and lower levels of proinflammatory marker TNF-α ( 74 ± 23 vs. 115 ± 15 pg / mL ; p = 0.04 ) compared to LD group. Conclusion. Allogeneic UCMSCs CLV-100 infusion is safe and well-tolerated in low and high doses. Anti-inflammatory effect is observed with a high-dose infusion.
- Published
- 2020
13. The Effect of Pretilt and Twisted Angle on Twisted Nematic Liquid Crystal Filter
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Han Hua, Yang Liu, and Kong Yong
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Materials science ,Birefringence ,Computer simulation ,business.industry ,Physics::Optics ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Soft Condensed Matter ,010309 optics ,Wavelength ,Optics ,law ,Liquid crystal ,Distortion ,0103 physical sciences ,Photonics ,0210 nano-technology ,business - Abstract
The effect of pretilt and twisted angle on twisted nematic liquid crystal filter (TNLCF) is studied theoretically and experimentally in this paper, based on the birefringence and distortion characteristic of twisted nematic liquid crystal, the output performance of TNLCF has been analyzed through numerical simulation firstly, then the corresponding experiment results verify the correctness of the simulation results, which show that the output performance of TNLCF is indeed related to pretilt angle and twisted angle of liquid crystal–with the increasing of the twisted angle the central wavelength of TNLCF will shift to the long wavelength, with the increasing of pretilt angle for the top glass substrate and the decreasing of pretilt angle for the bottom glass substrate the central wavelength of TNLCF will shift to the short wavelength, and if the pretilt angle of the bottom glass substrate is increased and the pretilt angle of the top glass substrate is reduced at the same time in some certain value or otherwise the shift trend of the central wavelength will be not evident. These results will offer an important reference value for the design and application of TNLCF as we believe.
- Published
- 2018
14. A Fully Integrated Quartz MEMS VHF TCXO
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Richard J. Joyce, S. E. Seman, Randall L. Kubena, Matthew D. Cross, Hung Nguyen, David T. Chang, Jeffrey F. Garstecki, Fred P. Stratton, Yook-Kong Yong, and Deborah J. Kirby
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010302 applied physics ,Microelectromechanical systems ,Materials science ,Acoustics and Ultrasonics ,Silicon ,business.industry ,Electrical engineering ,Quartz resonator ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Temperature measurement ,CMOS ,chemistry ,0103 physical sciences ,Optoelectronics ,Wafer ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Instrumentation ,Crystal oscillator ,Quartz ,Eutectic system - Abstract
We report on a 32-MHz quartz temperature compensated crystal oscillator (TCXO) fully integrated with commercial CMOS electronics and vacuum packaged at wafer level using a low-temperature MEMS-after quartz process. The novel quartz resonator design provides for stress isolation from the CMOS substrate, thereby yielding classical AT-cut f/T profiles and low hysteresis which can be compensated to±0.2 parts per million over temperature using on-chip third-order compensation circuitry. The TCXO operates at low power of 2.5 mW and can be thinned to as part of the wafer-level eutectic encapsulation. Full integration with large state-of-the-art CMOS wafers is possible using carrier wafer techniques.
- Published
- 2018
15. Do Pathogens from Corneal Scraping Show Their True Colours Better in Bactec Bottles?
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Logeswary K, Aida Zairani Mohd Zahidin, Hazlita Mohd Isa, Kong Yong Then, and Wan Haslina Wan Abdul Halim
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Culture plates ,food.ingredient ,business.industry ,Modified technique ,Antimicrobial ,medicine.disease ,Keratitis ,Microbiology ,03 medical and health sciences ,0302 clinical medicine ,food ,030221 ophthalmology & optometry ,medicine ,Agar ,030212 general & internal medicine ,business - Abstract
Identification of causative organisms of clinically suspected microbial keratitis is very important so that appropriate targeted antimicrobial treatment can be offered to patients. The current routine method of corneal scraping specimens on to multiple agar culture plates for microbiological study is not really providing encouraging result. Our trial of modified technique of using BACTEC broth for three clinically suspected microbial keratitis cases worked 100% to identify the causative organisms in cases of microbial keratitis.
- Published
- 2017
16. Looking into dental pulp stem cells in the therapy of photoreceptors and retinal degenerative disorders
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Badr Alzahrani, Aisha Farhana, Mae-Lynn Catherine Bastion, K. B. Swamy, Chenshen Lam, Antony V. Samrot, Kong Yong Then, Abdallah M. Elgorban, Hiba Amer Alsaeedi, Avin Ee-Hwan Koh, Akon Higuchi, Najat Marraiki, Suresh Kumar Subbiah, Bala Sundaram Muthuvenkatachalam, Pooi Ling Mok, and Seoh Wei Teh
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Retinal degeneration ,medicine.medical_treatment ,Biophysics ,Retina ,chemistry.chemical_compound ,Dental pulp stem cells ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Photoreceptor Cells ,Dental Pulp ,Radiation ,Retinal pigment epithelium ,Radiological and Ultrasound Technology ,business.industry ,Stem Cells ,Retinal Degeneration ,Retinal ,Stem-cell therapy ,medicine.disease ,Transplantation ,medicine.anatomical_structure ,chemistry ,Stem cell ,business ,Neuroscience ,Stem Cell Transplantation - Abstract
Blindness and vision impairment are caused by irremediable retinal degeneration in affected individuals worldwide. Cell therapy for a retinal replacement can potentially rescue their vision, specifically for those who lost the light sensing photoreceptors in the eye. As such, well-characterized retinal cells are required for the replacement purposes. Stem cell-based therapy in photoreceptor and retinal pigment epithelium transplantation is well received, however, the drawbacks of retinal transplantation is the limited clinical protocols development, insufficient number of transplanted cells for recovery, the selection of potential stem cell sources that can be differentiated into the target cells, and the ability of cells to migrate to the host tissue. Dental pulp stem cells (DPSC) belong to a subset of mesenchymal stem cells, and are recently being studied due to its high capability of differentiating into cells of the neuronal lineage. In this review, we look into the potential uses of DPSC in treating retinal degeneration, and also the current data supporting its application.
- Published
- 2019
17. Dental pulp stem cells therapy overcome photoreceptor cell death and protects the retina in a rat model of sodium iodate-induced retinal degeneration
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K. B. Swamy, Chenshen Lam, Seoh Wei Teh, Min Hwei Ng, Hazlita Mohd Isa, Sue Ngein Leow, Chi D Luu, Kong Yong Then, Jaikumar Nandakumar, Mohd Hairul Nizam Harun, Bala Sundaram Muthuvenkatachalam, Antony V. Samrot, Avin Ee-Hwan Koh, Mae-Lynn Catherine Bastion, Hiba Amer Alsaeedi, Pooi Ling Mok, Muhamad Fakhri bin Mohd Saleh, Munirah Binti Abd Rashid, and Suresh Subbiah Kumar
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Retinal degeneration ,Male ,Pathology ,medicine.medical_specialty ,medicine.medical_treatment ,030303 biophysics ,Biophysics ,Iodates ,Apoptosis ,02 engineering and technology ,Retinal Pigment Epithelium ,Mesenchymal Stem Cell Transplantation ,Photoreceptor cell ,Rats, Sprague-Dawley ,03 medical and health sciences ,chemistry.chemical_compound ,stomatognathic system ,Dental pulp stem cells ,Electroretinography ,Medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,Photoreceptor Cells ,Dental Pulp ,0303 health sciences ,Retina ,Radiation ,Retinal pigment epithelium ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,Retinal Degeneration ,Retinal ,Mesenchymal Stem Cells ,Stem-cell therapy ,021001 nanoscience & nanotechnology ,medicine.disease ,Rats ,Disease Models, Animal ,medicine.anatomical_structure ,chemistry ,sense organs ,0210 nano-technology ,business - Abstract
Blindness and vision loss contribute to irreversible retinal degeneration, and cellular therapy for retinal cell replacement has the potential to treat individuals who have lost light sensitive photoreceptors in the retina. Retinal cells are well characterized in function, and are a subject of interest in cellular replacement therapy of photoreceptors and the retinal pigment epithelium. However, retinal cell transplantation is limited by various factors, including the choice of potential stem cell source that can show variability in plasticity as well as host tissue integration. Dental pulp is one such source that contains an abundance of stem cells. In this study we used dental pulp-derived mesenchymal stem cells (DPSCs) to mitigate sodium iodate (NaIO3) insult in a rat model of retinal degeneration. Sprague-Dawley rats were first given an intravitreal injection of 3 × 105 DPSCs as well as a single systemic administration of NaIO3 (40 mg/kg). Electroretinography (ERG) was performed for the next two months and was followed-up by histological analysis. The ERG recordings showed protection of DPSC-treated retinas within 4 weeks, which was statistically significant (* P ≤ .05) compared to the control. Retinal thickness of the control was also found to be thinner (*** P ≤ .001). The DPSCs were found integrated in the photoreceptor layer through immunohistochemical staining. Our findings showed that DPSCs have the potential to moderate retinal degeneration. In conclusion, DPSCs are a potential source of stem cells in the field of eye stem cell therapy due to its protective effects against retinal degeneration.
- Published
- 2019
18. MEMS RF Magnetoelectric FeGaB/Quartz Receivers
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Yook-Kong Yong, R. L. Kubena, Xiangnan Pang, Richard J. Joyce, and W. W. Wall
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0303 health sciences ,Frequency response ,Materials science ,business.industry ,020206 networking & telecommunications ,Magnetostriction ,02 engineering and technology ,Piezoelectricity ,03 medical and health sciences ,Magnetization ,Resonator ,Electric field ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,Radio frequency ,Thin film ,business ,030304 developmental biology - Abstract
Recent research work on the theoretical and experimental possibilities of acoustically actuated MEMS RF magnetoelectric antennas using piezoelectric-magnetostrictive multilayers have been published, for example in ref. [1], [2]. A mechanism of electromagnetic-acoustic coupling was achieved in the composite ferromagnetic/piezoelectric heterostructure. The magnetostrictive thin film provided the function of converting the RF magnetic signal to acoustic vibration of the composite resonator while the piezoelectric body realized the transduction of acoustic wave to electric signal. In this paper, we proposed a novel MEMS RF FeGaB/Quartz receiver sensor where FeGaB had a relatively stronger piezomagnetic coefficient compared to other ferromagnetic materials such as nickel. The quartz resonator had the advantages of high Q, low resistance, and high frequency-temperature stability. Experiments were set up to measure the remnant magnetization state of FeGaB thin film deposited on AT- and SC-cut quartz wafers. Consistent comparison results were obtained between the simulated and measured magnetization curves of FeGaB thin films. A 10 MHz AT-cut quartz resonator coated with 200-nm-thick FeGaB layer was fabricated and tested. The frequency response of a similar uncoated quartz resonator was also tested so that the difference between the responses of coated and uncoated resonator respectively could yield a qualitative view of the magnetic field response. A special setup of experiments were taken to reduce the electric field effect of the RF signal. The simulated frequency responses of the coated and uncoated resonators showed trends that were consistent with the experimental results.
- Published
- 2019
19. Retinal degeneration rat model: A study on the structural and functional changes in the retina following injection of sodium iodate
- Author
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Mohammed Safwan Ali Khan, Munirah Binti Abd Rashid, Muhamad Fakhri bin Mohd Saleh, Hiba Amer Alsaeedi, Chi D Luu, Mohd Hairul Nizam Harun, Pooi Ling Mok, Chenshen Lam, S. Suresh Kumar, Min Hwei Ng, Hazlita Mohd Isa, Avin Ee-Hwan Koh, Sue Ngein Leow, Kong Yong Then, and Mae-Lynn Catherine Bastion
- Subjects
Retinal degeneration ,medicine.medical_specialty ,Retinal Disorder ,genetic structures ,Biophysics ,Iodates ,Apoptosis ,Retina ,Rats, Sprague-Dawley ,chemistry.chemical_compound ,Ophthalmology ,Retinitis pigmentosa ,medicine ,Electroretinography ,Animals ,Radiology, Nuclear Medicine and imaging ,Sodium iodate ,Radiation ,Retinal pigment epithelium ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,Retinal Degeneration ,Macular degeneration ,medicine.disease ,eye diseases ,Rats ,Disease Models, Animal ,medicine.anatomical_structure ,chemistry ,sense organs ,business ,DNA Damage - Abstract
Retinal disorders account for a large proportion of ocular disorders that can lead to visual impairment or blindness, and yet our limited knowledge in the pathogenesis and choice of appropriate animal models for new treatment modalities may contribute to ineffective therapies. Although genetic in vivo models are favored, the variable expressivity and penetrance of these heterogeneous disorders can cause difficulties in assessing potential treatments against retinal degeneration. Hence, an attractive alternative is to develop a chemically-induced model that is both cost-friendly and standardizable. Sodium iodate is an oxidative chemical that is used to simulate late stage retinitis pigmentosa and age-related macular degeneration. In this study, retinal degeneration was induced through systemic administration of sodium iodate (NaIO3) at varying doses up to 80 mg/kg in Sprague-Dawley rats. An analysis on the visual response of the rats by electroretinography (ERG) showed a decrease in photoreceptor function with NaIO3 administration at a dose of 40 mg/kg or greater. The results correlated with the TUNEL assay, which revealed signs of DNA damage throughout the retina. Histomorphological analysis also revealed extensive structural lesions throughout the outer retina and parts of the inner retina. Our results provided a detailed view of NaIO3-induced retinal degeneration, and showed that the administration of 40 mg/kg NaIO3 was sufficient to generate disturbances in retinal function. The pathological findings in this model reveal a degenerating retina, and can be further utilized to develop effective therapies for RPE, photoreceptor, and bipolar cell regeneration.
- Published
- 2019
20. Development of Steatohepatitis and Fibrosis in Chronic HBV Infection Is Linked to Inflammatory Responses Mediated by IL-13 and CCL11
- Author
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Hong-Yien Tan, Sui-Weng Wong, Muttiah Barathan, Chook Jack Bee, Behnaz Riazalhosseini, Yean-Kong Yong, Esaki M. Shankar, Marie Larsson, Kok Keng Tee, Rosmawati Mohamed, and Yi-Wen Ting
- Subjects
medicine.medical_specialty ,Cirrhosis ,business.industry ,Fatty liver ,Context (language use) ,Disease ,medicine.disease ,Internal medicine ,Medicine ,Liver function ,Steatohepatitis ,Metabolic syndrome ,business ,Transient elastography - Abstract
Background: In view of the importance of chronic HBV (CHB) infection and the global burden of non-alcoholic fatty liver disease (NAFLD), it is imperative to understand the potential interplay between the two diseases. Methods: Here, we retrospectively investigated the association between NAFLD and CHB infection in the context of liver fibrosis. Among the 522 consecutive CHB patients who underwent transient elastography between year 2013 and 2016, we studied 449 subjects in the current investigation. Findings: CAP and LSM scores were generally higher in patients with steatosis and fibrosis or cirrhosis. Antiviral treatment had significantly reduced the HBV viral load. Other liver function markers showed a significant positive correlation with both CAP and LSM scores. Plasma IL-13 was independently associated with increased CAP score where every increase of 1 unit of IL-13 was associated with an increase in CAP score by 0.98 unit. CCL11 was independently associated with LSM with every increase of CCL11 by a unit that, in turn, was associated with an increase of LSM score. Interpretations: Together, we found that there was a high concurrence of NAFLD among patients with CHB. The presence of metabolic syndrome and chronic inflammation in CHB patients were two independent factors that led to progression of liver cirrhosis, with IL-13 playing the key role in linking the metabolic with the inflammatory components. Plasma markers of liver steatosis and fibrosis progression are key to development of cell-targeted therapies exploiting specific molecular pathways. Funding Statement: This work was supported by a grant from the Frontier Research Grant (FRG), FG019-17AFR to Mohamed Rosmawati and Xiamen University Malaysia Research Funding (XMUMRF), XMUMRF/2018-C2/ILAB/0001. Marie Larsson is supported by the Swedish Research Council, the Swedish Physicians against AIDS Research Foundation; VINNMER for Vinnova, Linkoping University Hospital Research Fund, ALF Grants Region Ostergotland, FORSS. Declaration of Interests: The authors declare no conflicts interest. Ethics Approval Statement: The medical records of patients were extracted from the hospital database using patients’ unique hospital registration number. This study was approved by the Medical Ethics Committee of the University Malaya Medical Centre (MEC-938.42).
- Published
- 2019
21. Revisiting the role of erythropoietin for treatment of ocular disorders
- Author
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Rusheni Munisvaradass, Kong Yong Then, E. H. Koh, Sue Ngein Leow, S. Suresh Kumar, S. L. Shirley Ding, Pooi Ling Mok, and Mae-Lynn Catherine Bastion
- Subjects
0301 basic medicine ,Eye Diseases ,genetic structures ,Glaucoma ,Review ,Bioinformatics ,03 medical and health sciences ,chemistry.chemical_compound ,hemic and lymphatic diseases ,medicine ,Humans ,Optic neuritis ,Erythropoietin ,business.industry ,Retinal detachment ,Retinopathy of prematurity ,Retinal ,Diabetic retinopathy ,Macular degeneration ,medicine.disease ,eye diseases ,Ophthalmology ,030104 developmental biology ,chemistry ,sense organs ,business ,medicine.drug - Abstract
Erythropoietin (EPO) is a glycoprotein hormone conventionally thought to be responsible only in producing red blood cells in our body. However, with the discovery of the presence of EPO and EPO receptors in the retinal layers, the EPO seems to have physiological roles in the eye. In this review, we revisit the role of EPO in the eye. We look into the biological role of EPO in the development of the eye and the physiologic roles that it has. Apart from that, we seek to understand the mechanisms and pathways of EPO that contributes to the therapeutic and pathological conditions of the various ocular disorders such as diabetic retinopathy, retinopathy of prematurity, glaucoma, age-related macular degeneration, optic neuritis, and retinal detachment. With these understandings, we discuss the clinical applications of EPO for treatment of ocular disorders, modes of administration, EPO formulations, current clinical trials, and its future directions.
- Published
- 2016
22. Effective Treatment of Epithelial Downgrowth in Persistent Wound Leak Following Removal of Silicone Oil
- Author
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Kong Yong Then, Mae-Lynn Catherine Bastion, and Aida Zairani Mohd Zahidin
- Subjects
medicine.medical_specialty ,genetic structures ,business.industry ,Clinical Biochemistry ,lcsh:R ,Wound leak ,lcsh:Medicine ,General Medicine ,retinal redetachment ,Silicone oil ,eye diseases ,Surgery ,chemistry.chemical_compound ,chemistry ,cornea epithelial downgrowth ,medicine ,Effective treatment ,Epithelial downgrowth ,5-fluorouracil ,sense organs ,business - Abstract
This case report aims to share the successful management of Epithelial Downgrowth (ED) which occurred following persistent wound leak, after Removal of Silicone Oil (ROSO) via the anterior chamber. A teenage male with history of high myopia underwent bilateral phacoemulsification and implantation of Multifocal Intraocular Lens (MFIOLs). Four months later, he complained of left eye floaters and blurring of vision. Fundus showed left vitreous haemorrhage with lens subluxation. Left 23 gauge pars plana vitrectomy revealed multiple retinal tears. Endolaser and gas injection with MFIOL repositioning was done. Retinal redetachment and MFIOL subluxation occurred six weeks postoperatively. Revision vitrectomy with silicone oil and explantation of MFIOL was performed rendering left eye aphakic. Four months later, he underwent ROSO via a superior corneal incision. Positive Seidels was seen two weeks post-ROSO and resuturing was performed. Unfortunately, advancing ED was noted at the superior cornea. One month after ROSO, scleral fixated IOL implantation with manual removal of ED and intracameral injection of 5-fluorouracil (5-FU) were performed. Twelve months postoperatively, cornea remained clear with a pinhole vision of 6/7.5 and retina was flat. In conclusion, wound leak after ROSO via the anterior chamber in aphakic individuals may predispose to ED. Key to treatment of this sight threatening condition is thoughtful anterior segment examination. Manual removal of the membrane combined with 5-FU injection during secondary lens implantation surgery is an effective treatment.
- Published
- 2018
23. The use of bone marrow derived mesenchymal stem cell for cornea regeneration in rabbit model
- Author
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C.M. Rohaina, A.R. Ropilah, M. Azlina, Min Hwei Ng, Bt Hj Idrus Ruszymah, and Kong Yong Then
- Subjects
Pathology ,medicine.medical_specialty ,Stromal cell ,business.industry ,Regeneration (biology) ,Mesenchymal stem cell ,eye diseases ,Transplantation ,Corneal Disorder ,Ophthalmology ,medicine.anatomical_structure ,Tissue engineering ,Cornea ,Medicine ,sense organs ,Bone marrow ,business - Abstract
Aim or Purpose: To evaluate the use of autologous bone marrow derived mesenchymal stem cells (BM-MSCs) to treat cornea stromal defect in a rabbit model. Methods: A non-randomized interventional controlled animal study involving twenty one adult New Zealand white rabbits. Corneal deep lamellar dissections were created in three groups of rabbits and treated accordingly. Group I; Autologous bone marrow derived MSCs with autologous fibrin and human amniotic membrane. Group II; Autologous fibrin with human amniotic membrane without MSCs. Group III; No treatment. Clinical outcome was evaluated by corneal re-epithelization, corneal opacity, corneal thickness and histology. Results: BM-MSCs were successfully isolated from bone marrow of seven rabbits based on the adherence property of the cells to the plastic of the cell culture plate. At day 60 corneal thicknesses was significantly thicker in Group I. The localization of PKH26 labeled BM-MSCs showed an increase in cell density at the transplanted site, proving its role in cornea stromal regeneration. Although the cornea clarity was not achieved in this study, we believe that cornea stromal remodeling requires many months to years to regain its original optical quality. Conclusion: Locally transplanted BM-MSCs may be a useful source for cornea stromal regeneration. The use of autologous BM-MSCs offers a promising option for treating corneal disorder without the risk of immune-rejection and calcification.
- Published
- 2017
24. Introduction to the 2014 IUS special issue on ultrasonics
- Author
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Paul D. Wilcox, F. Levent Degertekin, Mostafa Fatemi, and Yook-Kong Yong
- Subjects
medicine.medical_specialty ,Acoustics and Ultrasonics ,business.industry ,Medicine ,Medical physics ,Electrical and Electronic Engineering ,Ultrasonography ,business ,Instrumentation - Published
- 2015
25. On the acceleration sensitivity and its active reduction by edge electrodes in at-cut Quartz resonators
- Author
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Randall L. Kubena, Deborah J. Kirby, David T. Chang, Yook-Kong Yong, and Jianfeng Chen
- Subjects
Body force ,Materials science ,Cantilever ,Acoustics and Ultrasonics ,business.industry ,Bending ,Piezoelectricity ,Vibration ,Acceleration ,Resonator ,Optics ,Physics::Accelerator Physics ,Sensitivity (control systems) ,Electrical and Electronic Engineering ,business ,Instrumentation - Abstract
Incremental piezoelectric equations for small vibrations superposed on initial deformations are presented. The equations are implemented in COMSOL finite element models (FEA). Equations are validated by comparing the results for the force sensitivity coefficient Kf of a circular quartz plate subjected to a pair of diametrical forces with measured data. The model results show a consistent trend with the experimental results, and the relative difference between our FEA results and Ballato's measured result is about 13%. A detailed study of the acceleration sensitivity of a rectangular AT-cut quartz plate is presented. The plate resonator is fixed along one edge as a cantilever. For AT-cut quartz resonators with the crystal digonal X-axis perpendicular to plate X-axis, the in-plane acceleration sensitivity is found to be negligible compared with the out-of-plane (Y-axis) acceleration sensitivity. For AT-cut quartz resonators with the crystal digonal X-axis parallel to plate X-axis, the Y-axis acceleration sensitivity is found to be rectified, that is the fractional change in frequency is positive with respect to both positive and negative Y-axis accelerations. The Y-axis acceleration sensitivity is small in comparison with the in-plane acceleration sensitivity for small body forces. However, for large body forces, the Y-axis acceleration sensitivity dominates because it increases nonlinearly with the Y-axis acceleration. The resonator rectified acceleration sensitivity is confirmed by phase noise measurements. For reduced acceleration sensitivity, two pairs of electrodes along the plate edges reduce the bending of the plate resonator and subsequently reduce acceleration sensitivity. We present a new method using these edge electrodes in which a dc bias field is employed to control the resonant frequency of resonator subjected to g body forces. A dc bias field with an appropriate dc bias voltage could potentially yield a reduction of acceleration sensitivity in Y-axis direction of about two orders of magnitude.
- Published
- 2015
26. Spoil to Soil
- Author
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Yubo Yan, Meththika Vithanage, Ravi Naidu, Girish Choppala, DeAnn Presley, Yasser Awad, Soon Kong Yong, Dan Tsang, Dane Lamb, Liang Wang, Nanthi Bolan, and Christopher Barton
- Subjects
Engineering ,Rehabilitation ,business.industry ,medicine.medical_treatment ,medicine ,business ,complex mixtures ,Environmental planning ,Mine site - Published
- 2017
27. Nonlinear frequency response of second harmonic generation in SAW IDT resonators
- Author
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Yook-Kong Yong and Xiangnan Pang
- Subjects
010302 applied physics ,Physics ,Frequency response ,business.industry ,Acoustics ,Lithium niobate ,Electrical engineering ,Second-harmonic generation ,01 natural sciences ,Harmonic analysis ,Nonlinear system ,Resonator ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Harmonic ,High harmonic generation ,business - Abstract
A general purpose finite element model that yielded directly the nonlinear frequency response of the second harmonic generation in SAW IDT resonators was developed. The model enabled us to study the effects of the nonlinear material constants, voltage drive, duty factor, and IDT geometry on f-2f nonlinear interactions. Specifically we have applied our model to the study of nonlinear frequency response of second harmonic generation in lithium niobate YX-127o SAW IDT resonators. Lithium niobate was chosen because a complete set of its nonlinear material constants was known and published in the literature. A complete set of nonlinear piezoelectric equations along with their material constants for a lithium niobate YX-127o SAW IDT 836 MHz resonator was implemented in a finite element program. Two sets of finite element matrix equations were derived for the fundamental SAW mode and its 2nd harmonic mode, respectively. We demonstrated how two frequency domain interfaces could be coupled together to simulate the f-2f nonlinear interactions. The fundamental Rayleigh SAW mode was excited by a drive voltage at the IDT that in turn generated the 2nd harmonic mode at twice the frequency. A higher voltage drive lead to higher 2f interactions. Effects of the 2nd harmonic generation on the fundamental SAW mode and its Q were observed when the voltage drive was greater than 0.5V. For example, when the drive voltage was 0.1V the fundamental mode was clean. But when the drive voltage was increased to 0.5V the fundamental mode exhibited Q reduction and stronger f-2f interactions were observed, namely, there were stronger interactions of the 2f BAW mode with the f SAW mode. There was an optimal duty factor of 0.4 to 0.5 for the least f-2f interactions. Thinner electrode thickness resulted in stronger f-2f interactions.
- Published
- 2017
28. Force frequency effects in third overtone thickness shear quartz resonators
- Author
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Yook-Kong Yong and Jianfeng Chen
- Subjects
Cantilever ,Materials science ,business.industry ,Negative frequency ,Overtone ,Geometry ,Bending of plates ,Edge (geometry) ,01 natural sciences ,Finite element method ,Stress (mechanics) ,Acceleration ,Optics ,0103 physical sciences ,business ,010301 acoustics - Abstract
The behavior of vibrating crystal plates under the action of external forces was studied. The plates were respectively subjected to diametrical compression force and bending force in different configurations: (a) a clamped cantilever, (b) a cantilever with displaced knife edges, and (c) a dual support mounting with displaced knife edge applied midway between. Finite element models were developed using the theory of small deformations superposed on finite initial deformations in Lagrangian formulation. The model results compared well with the experimental results by Mingins, Ballato, et. al., [3, 4]. For the AT-cut plate, the azimuth Ψ angles of frequency insensitivity due to compressional force were found at Ψ∼65° and 115°. For the plate bending in a clamped cantilever configuration a W-shaped plot of negative frequency deviations was observed when Ψ was varied from 0° to 180°, while the maximum positive frequency deviations occurred at Ψ∼270°. For the plate bending of cantilever with displaced knife edges, the results were similar to the plate bending in a clamped cantilever configuration. For the plate bending of dual support mounting with displaced knife edge applied in midway, the results for Ψ = 0° to 180° were very similar to Ψ = 180° to 360°. By searching out the effects of frequency deviations, optimal angles can be obtained to minimize or eliminate them.
- Published
- 2017
29. The use of intravenous pulse-steroid therapy in optic neuropathy from nasopharyngeal carcinoma
- Author
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Karen Bulan Reyes and Kong Yong Goh
- Subjects
medicine.medical_specialty ,genetic structures ,business.industry ,Pulse (signal processing) ,medicine.medical_treatment ,medicine.disease ,eye diseases ,Surgery ,Radiation therapy ,Optic neuropathy ,Ophthalmology ,Steroid therapy ,Nasopharyngeal carcinoma ,medicine ,Carcinoma ,Optic nerve ,In patient ,business - Abstract
Although nasopharyngeal carcinoma (NPC) is commonly seen in patients from Asia, optic neuropathy is a rare initial presenting symptom of this disease. This is an interventional case report discussing the clinical response of NPC-related optic neuropathy to pulse-steroid therapy. We discuss two patients who initially presented with signs of optic neuropathy. On imaging, a skull-base tumor was noted infiltrating the area of the affected optic nerve. An excision biopsy of the tumor revealed nasopharyngeal carcinoma. Both patients were pulsed with intravenous (IV) methlyprednisolone one gm/day for three days, followed by oral steroids (one mg/kg/BW) with gradual tapering. After two weeks, both showed visual improvement and chemo- and radiation therapy commenced at this time. In these two cases, pulse-steroid therapy did not hinder the chemo- and radiation therapy for nasopharyngeal carcinoma. Steroid therapy brought immediate visual recovery and gradual oral tapering could assist in optimizing visual outcomes for patients with compressive optic neuropathy from nasopharyngeal carcinoma.
- Published
- 2013
30. Controversies in ocular trauma classification and management: review
- Author
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Kamiar Mireskandari, Rupesh Agrawal, Goh Kong Yong, and Mehul A Shah
- Subjects
medicine.medical_specialty ,genetic structures ,medicine.medical_treatment ,Corneal abrasion ,Poison control ,Optic neuropathy ,Eye Injuries ,Endophthalmitis ,Vitrectomy ,medicine ,Humans ,Intensive care medicine ,Hyphema ,business.industry ,Sympathetic ophthalmia ,Cataract surgery ,Prognosis ,medicine.disease ,eye diseases ,Anti-Bacterial Agents ,Surgery ,Posterior segment of eyeball ,Ophthalmology ,Cryotherapy ,Steroids ,sense organs ,business - Abstract
Ocular trauma is a topic of unresolved controversies and there are continuous controversial and debatable management strategies for open-globe injuries (OGIs). International classification of ocular trauma proposed almost 15 years ago needs to be reviewed and to be more robust in predicting the outcome in the setting of OGIs. Anterior segment trauma involves controversies related to patching for corneal abrasion, corneal laceration repair, and medical management of hyphema. Timing of cataract surgery and intraocular lens implantation in the setting of trauma is still debated worldwide. There are unresolved issues regarding the management of OGIs involving the posterior segment. Timing of vitrectomy has been and will continue to be debated by proponents of early versus delayed intervention. The use of prophylactic cryotherapy and scleral buckle is still practiced differently throughout the world. The role of intravitreal antibiotics in posterior segment trauma in the absence of infection is still debated. Similarly, the use of vitrectomy versus vitreous tap in the setting of traumatic endophthalmitis is not fully resolved. In optic neuropathy, the role of intravenous methylprednisolone versus conservative management is always debated and still there are no evidence-based guidelines about the beneficial role of pulse steroid therapy. The role of optic canal decompression in the setting of acute traumatic optic neuropathy is also not conclusive. Orbital and adnexal trauma has been shown to adversely affect the outcome of OGI patients but both lids and orbital injury are not taken as preoperative variables in international ocular trauma classification. The timing of intervention in blow-out fracture is still debated. The pediatric age group, owing to the high risk of amblyopia and intraocular inflammation as well as strong vitreoretinal adhesions, has to be managed by different principles. Although the risk of sympathetic ophthalmia is very rare, it is always one of the key debated issues while managing traumatized eyes with no light perception vision. Prospective, controlled clinical studies are not possible in the OGI setting and this article reviews pertinent data regarding these management issues and controversies, and provides recommendations for treatment based on the available published data and the authors' personal experience.
- Published
- 2013
31. Lagrangian model of the frequency-temperature behavior of SAW resonators
- Author
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Xiangnan Pang and Yook-Kong Yong
- Subjects
Materials science ,business.industry ,010401 analytical chemistry ,Mathematical analysis ,02 engineering and technology ,01 natural sciences ,Finite element method ,0104 chemical sciences ,Stress (mechanics) ,Nonlinear system ,Resonator ,020303 mechanical engineering & transports ,Optics ,Thermoelastic damping ,0203 mechanical engineering ,Boundary value problem ,business ,Temperature coefficient ,Reference frame - Abstract
The experimental studies of temperature coefficient of frequency (TCF) of SAW resonators were usually modeled by TCF models first proposed by Bechmann, Ballato and Lukaszeck[1]. These models unfortunately were not frame invariant with regards to the material property tensors of the crystal substrate and metal interdigital transducers (IDTs). Furthermore the models did not have the 3rd order nonlinear elastic constants that were needed to account for the effects of thermal strains from mountings, boundary constraints, and material interfaces. We employed a Lagrangian model of TCF of SAW resonators wherein governing equations for incremental vibrations superposed on thermal strains were implemented in a finite element program. The model used material coordinates referred to a fixed reference frame at a reference temperature, therefore the material property tensors were frame invariant. In addition it had a term that was a product of the 3rd order nonlinear elastic constants and thermoelastic strains. This product could account for the thermoelastic strains from interfacial stresses and boundary conditions. The objective of our study was to provide an accurate and detailed finite element model of the effects of the crystal substrate, metal IDTs, and stack layers on the TCF of SAW resonators. Good comparisons of model results with the experimental results were found for the 1 GHz lithium tantalate YXl 42° shear horizontal SAW resonator. Characterization of the electrode film properties was found to be important, especially when the film thickness was increased from 2000 A to 4000 A.
- Published
- 2016
32. Effects of initial nonlinear strains and nonlinear elastic constants in force-frequency and acceleration sensitivity of quartz resonators
- Author
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Yook-Kong Yong and Jianfeng Chen
- Subjects
Materials science ,business.industry ,010401 analytical chemistry ,Bending ,Mechanics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Condensed Matter::Materials Science ,Nonlinear system ,Resonator ,Acceleration ,Capacitor ,Optics ,law ,0103 physical sciences ,Phase noise ,Sensitivity (control systems) ,business ,010301 acoustics ,Quartz - Abstract
The acceleration sensitivity and its related problem of force-frequency in quartz resonators were studied. We studied the effects of initial nonlinear strains versus the effects of nonlinear elastic constants on the force-frequency problem of quartz resonators subjected to bending forces. We found that for quartz thickness shear resonators subjected to bending, the force frequency effect could be described primarily by the effects of nonlinear elastic constants with negligible effects from initial nonlinear strains. Since the acceleration sensitivity of quartz resonators is due mainly to bending forces, we proposed a set of simplified equations for these problems which were easier to implement in commercial finite element software.
- Published
- 2016
33. The elastic stiffness of langasite at high temperatures and its temperature compensated orientations
- Author
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Yook-Kong Yong and Gobong Choi
- Subjects
Materials science ,business.industry ,Stiffness ,Thermodynamics ,Effective temperature ,Atmospheric temperature range ,01 natural sciences ,Thermal expansion ,Vibration ,Crystal ,Optics ,0103 physical sciences ,medicine ,Material constants ,medicine.symptom ,Material properties ,business ,010301 acoustics - Abstract
The langasite crystal has the capability of no phase change at temperatures exceeding 600°C for high temperature applications. Since the material properties of langasite were measured usually at 25 0C as the reference temperature they are no longer accurate at high temperature environments. We employ a Lagrangian formulation to investigate the temperature behavior of thickness vibrations of langasite in a wide temperature range from 25°C to 600°C. The analysis only requires the elastic constants and their effective temperature derivatives of elastic constants and thermal expansion coefficients to predict the material constants at any given temperature. Based on the new values of the elastic constants and thermal expansion coefficients, the zero-valued temperature coefficients of frequency are investigated. The presently identified temperature compensated crystal cuts of the thickness-shear modes of langasite at different temperatures were compared with those at reference temperature and also with some cuts found in the literature.
- Published
- 2016
34. Suturing techniques and postoperative management in penetrating keratoplasty in the United Kingdom
- Author
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Tassos Georgiou, Kong Yong Then, Bobby Paul, Fook Chang Lam, Ioannis Mavrikakis, Venkata S. Avadhanam, Richard M.H. Lee, and Christopher Liu
- Subjects
Suturing techniques ,medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,corneal graft ,Topical antibiotics ,Clinical Ophthalmology ,corneal surgery ,Host tissue ,penetrating keratoplasty ,Postoperative management ,anterior segment surgery ,corneal transplantation ,Ophthalmology ,Postal questionnaire ,cornea ,Medicine ,business ,Corneal transplantation ,Continuous suture ,Granny knot ,Original Research - Abstract
Richard MH Lee,1 Fook Chang Lam,1 Tassos Georgiou,1 Bobby Paul,1 Kong Yong Then,1 Ioannis Mavrikakis,1 Venkata S Avadhanam,1 Christopher SC Liu1,21Sussex Eye Hospital, Brighton, United Kingdom; 2Tongdean Eye Clinic, Hove, United KingdomAims: To report on the suturing techniques and aspects of postoperative management in penetrating keratoplasty in the United Kingdom.Methods: A postal questionnaire was sent to 137 ophthalmic consultants identified from a Royal College of Ophthalmology database as having a special interest in anterior segment surgery. The questionnaire surveyed surgeon preferences for surgical and suturing technique for penetrating keratoplasty surgery, and the postoperative care of corneal grafts.Results: In all, 68% of questionnaires were completed and returned: 73% of respondents used a Flieringa ring or equivalent, 94% routinely used cardinal sutures, with 50.5% removing them at the end of the procedure. The most common suturing technique for routine penetrating keratoplasty was a single continuous suture (35%). In these cases, a 10/0 nylon suture was used by 89%. Sixty-six percent changed their technique in high-risk cases, 52% used a 3-1-1 knot, and 75% made a distinction between a reef and granny knot, with 76% using a reef. Thirty percent buried the knots within the donor material, and 29% within the host tissue. Twenty-five percent had no routine time for graft suture removal, but 41% removed them between 1 and 2 years post-surgery. After suture removal, 98% used steroids and 88% used topical antibiotics. Thirty-four percent stopped topical steroids before suture removal, with 38% stopping topical steroids more than 3 months prior to suture removal.Conclusion: This survey demonstrates that there is considerable variation in suturing techniques and postoperative care for penetrating keratoplasty. These significant variations in practice need to be considered when interpreting outcomes and research.Keywords: corneal graft, penetrating keratoplasty, anterior segment surgery, cornea, corneal surgery, corneal transplantation
- Published
- 2012
35. Abnormal Peripapillary Nerve Fibre Layer Thickness Demonstrated by Optical Coherence Tomography in Cases of Optic Atrophy: Is There a Correlation With Aetiology?
- Author
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Chee-Fang Chin and Kong Yong Goh
- Subjects
medicine.medical_specialty ,Pathology ,genetic structures ,medicine.diagnostic_test ,business.industry ,Nerve fibre layer ,medicine.disease ,eye diseases ,Normative database ,Ophthalmology ,Quadrant (abdomen) ,medicine.anatomical_structure ,Atrophy ,Optical coherence tomography ,medicine ,sense organs ,Neurology (clinical) ,business ,Optic disc - Abstract
Optical coherence tomography of the peripapillary nerve fibre layer has been used in optic atrophy for identification of axonal loss and for differential diagnosis. In the present study, we aim to evaluate whether the pattern of peripapillary nerve fibre layer thinning, based on the optical coherence tomography normative database, correlates with aetiology in cases of optic atrophy. This retrospective study is approved by the Tan Tock Seng Hospital Ethics Review Board. Consecutive patients with optic atrophy seen in the Neuro-Ophthalmology Clinic between May 2005 and August 2006 were included. The normal eyes of the patients served as controls. All patients underwent imaging using Stratus optical coherence tomography of the peripapillary nerve fibre layer, optic disc photographs and Humphrey perimetry. The aetiology of each case of optic atrophy were made by means other than the optical coherence tomography. Significant nerve fibre layer thinning was defined as a reading in the red quadrant on the Stratus...
- Published
- 2010
36. SH-SAW propagation in layered functionally graded piezoelectric material structures loaded with viscous liquid
- Author
-
Yook-Kong Yong, Kai Xian, Ji Wang, and Jianke Du
- Subjects
Permittivity ,Materials science ,Piezoelectric coefficient ,business.industry ,Mechanical Engineering ,Surface acoustic wave ,Computational Mechanics ,Viscous liquid ,Piezoelectricity ,Optics ,Dispersion relation ,Composite material ,Phase velocity ,Material properties ,business - Abstract
We investigate the properties of shear horizontal surface acoustic wave propagation in layered functionally graded piezoelectric material structures loaded with viscous liquid. The piezoelectric material is polarized in the z-direction and the material properties change gradually along the thickness of the layer. Interfacial mechanical conditions are continuity of particle velocity and stress components at the interface. We here assume that the liquid is electrically insulated and its permittivity is much less than that of the piezoelectric material. The solutions of dispersion relations are obtained for insulated liquid with electrically open or shorted conditions by means of transfer matrix method. The effects of the gradient variation of material constants on the phase velocity and attenuation are presented and discussed in detail. The analytical method and the results are useful for the design of the resonators and sensors.
- Published
- 2009
37. Conceptual Design of a High-Q, 3.4-GHz Thin Film Quartz Resonator
- Author
-
Mihir S Patel and Yook-Kong Yong
- Subjects
Frequency response ,Materials science ,Acoustics and Ultrasonics ,business.industry ,Piezoelectric sensor ,Electrical engineering ,Quartz crystal microbalance ,Capacitance ,Resonator ,Q factor ,Optoelectronics ,Electrical and Electronic Engineering ,Thin film ,business ,Instrumentation ,Coupling coefficient of resonators - Abstract
Theoretical analyses and designs of high-Q, quartz thin film resonators are presented. The resonators operate at an ultra-high frequency of 3.4 GHz for application to high-frequency timing devices such as cesium chip-scale atomic clocks. The frequency spectra for the 3.4-GHz thin film quartz resonators, which serve as design aids in selecting the resonator dimensions/configurations for simple electrodes, and ring electrode mesa designs are presented here for the first time. The thin film aluminum electrodes are found to play a major role in the resonators because the electrodes are only one third the thickness and mass of the active areas of the plate resonator. Hence, in addition to the material properties of quartz, the elastic, viscoelastic, and thermal properties of the electrodes are included in the models. The frequency-temperature behavior is obtained for the best resonator designs. To improve the frequency-temperature behavior of the resonators, new quartz cuts are proposed to compensate for the thermal stresses caused by the aluminum electrodes and the mounting supports. Frequency response analyses are performed to determine the Q-factor, motional resistance, capacitance ratio, and other figures of merit. The resonators have Q's of about 3800, resistance of about 1300 to 1400 ohms, and capacitance ratios of 1100 to 2800.
- Published
- 2009
38. Drive level dependency in quartz resonators
- Author
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Yook-Kong Yong, Mihir S Patel, and Masako Tanaka
- Subjects
Engineering ,Acoustics ,Drive level dependency ,Stress (mechanics) ,Resonator ,Materials Science(all) ,Modelling and Simulation ,General Materials Science ,Power density ,business.industry ,Cauchy stress tensor ,Mechanical Engineering ,Applied Mathematics ,Electrical engineering ,Q-factor ,Quartz ,Condensed Matter Physics ,Spurious modes ,Mechanics of Materials ,Modeling and Simulation ,Q factor ,business ,Current density ,Excitation ,Voltage - Abstract
Common piezoelectric resonators such as quartz resonators have a very high Q and ultra stable resonant frequency. However, due to small material nonlinearities in the quartz crystal, the resonator is drive level dependent, that is, the resonator level of activity and its frequency are dependent on the driving, or excitation, voltage. The size of these resonators will be reduced to one fourth of their current sizes in the next few years, but the electrical power which is applied will not be reduced as much. Hence, the applied power to resonator size ratio will be larger, and the drive level dependency may play a role in the resonator designs. We study this phenomenon using the Lagrangian nonlinear stress equations of motion and Piola–Kirchhoff stress tensor of the second kind. Solutions are obtained using COMSOL for the AT-cut, BT-cut, SC-cut and other doubly rotated cut quartz resonators and the results compared well with experimental data. The phenomenon of the drive level dependence is discussed in terms of the voltage drive, electric field, power density and current density. It is found that the drive level dependency is best described in terms of the power density. Experimental results for the AT-, BT- and SC-cut resonators in comparison with our model results are presented. Results for new doubly rotated cuts are presented. The effects of spurious modes, quality factor and air damping on DLD are presented.
- Published
- 2009
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39. Effects of electromagnetic radiation on the Q of quartz resonators
- Author
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John R. Vig, Yook-Kong Yong, Arthur Ballato, and Mihir S Patel
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Dielectric resonator antenna ,Materials science ,Acoustics and Ultrasonics ,business.industry ,Piezoelectric sensor ,Electromagnetic spectrum ,Electromagnetic radiation ,Piezoelectricity ,Resonator ,Optics ,Q factor ,Electrical and Electronic Engineering ,business ,Instrumentation ,Helical resonator - Abstract
The quartz resonator Q with aluminum electrodes was studied with respect to its fundamental thickness shear mode frequency and its viscoelastic, viscopiezoelectric, and viscopiezoelectromagnetic behaviors. The governing equations for viscoelasticity, viscopiezoelectricity, and viscopiezoelectromagnetism were implemented for an AT-cut quartz resonator. To simulate the radiation conditions at infinity for the viscopiezoelectromagnetic model, perfectly matched layers over a surface enclosing the resonator were implemented to absorb all incident electromagnetic radiation. The shape of the radiation spectrum of a 5.6 MHz AT-cut quartz resonator was found to compare relatively well the measured results by Campbell and Weber. The mesa-plate resonator was studied for a frequency range of 1.4 GHz to 3.4 GHz. The resonator Q was determined to be influenced predominantly by the quartz viscoelasticity; however at frequencies greater than 2.3 GHz, the quartz electromagnetic radiation had an increasingly significant effect on the resonator Q. At 3.4 GHz, the electromagnetic radiation accounted for about 14% of the loss in resonator Q. At frequencies less than 2 GHz, the calculated resonator Q compared well with the intrinsic Q(x) provided by the formula Q(x) = 16 x 10(6)/f where f was in MHz. At frequencies higher than 2.3 GHz, the aluminum electrodes had significant effects on the resonator Q. At 3.4 GHz, the electromagnetic radiation loss in the electrodes was an order of magnitude greater than their viscoelastic loss; hence, the vibrating aluminum electrodes became an efficient emitter of electromagnetic waves. The effects of electrical resistance in both the electrodes and quartz were determined to be negligible.
- Published
- 2009
40. The Incidence of Neuro-Ophthalmic Diseases in Singapore: A Prospective Study in Public Hospitals
- Author
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Wan-Ling Wong, Kong Yong Goh, James F. Cullen, Alvin Seah, Sharon Tow, Esther Fu, Su Ann Lim, Clement Tan, and Tien Yin Wong
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Adult ,Male ,Pathology ,medicine.medical_specialty ,Optic Neuritis ,Adolescent ,Eye Diseases ,Epidemiology ,Population ,Prevalence ,Neuro-ophthalmology ,Young Adult ,Age Distribution ,Asian People ,Risk Factors ,Diabetes mellitus ,Oculomotor Nerve Diseases ,medicine ,Humans ,Optic Neuropathy, Ischemic ,Prospective Studies ,Sex Distribution ,Child ,Prospective cohort study ,education ,Aged ,Aged, 80 and over ,Singapore ,education.field_of_study ,Hospitals, Public ,business.industry ,Incidence ,Incidence (epidemiology) ,Middle Aged ,medicine.disease ,Cranial Nerve Diseases ,Confidence interval ,Ophthalmology ,Child, Preschool ,Female ,business ,Abducens Nerve Diseases ,Demography - Abstract
To describe the incidence of neuro-ophthalmic diseases in a multi-ethnic Asian population in Singapore.Prospective study in public hospitals in Singapore. All neuro-ophthalmic cases seen in four public sector hospitals over a 22-month period (September 2002 to June 2004) were identified using a standardized protocol. The 2004 Singapore population was used as a denominator to estimate annual incidence. The prevalence of ischemic risk factors (hypertension, diabetes, and hypercholesterolemia) among cases was compared to population data.A total of 1,356 patients with neuro-ophthalmic diseases were seen during the study period, of which 627 were new incident cases. The overall annual incidence of neuro-ophthalmic diseases was 9.81 per 100,000 (95% confidence interval, 8.80-10.90). The incidence increased with age. After controlling for age, the annual incidence was similar between men (10.75 per 100,000) and women (9.00 per 100,000), but was higher in Chinese (10.33 per 100,000) and Indians (9.34 per 100,000) than in Malays (6.62 per 100,000). The three commonest specific neuro-ophthalmic conditions were abducens nerve palsy (1.27 per 100,000), anterior ischemic optic neuropathy (1.08 per 100,000) and oculomotor nerve palsy (0.91 per 100,000). The incidence of optic neuritis was 0.83 per 100,000. Compared with the Singapore general population, the prevalence of diabetes was significantly higher in people aged 40-59, while the prevalence of hypercholesterolemia was significantly higher in 60-69 year age group.In this study of public hospitals in Singapore, the incidence of neuro-ophthalmic diseases was higher in Chinese and Indians compared to Malays.
- Published
- 2009
41. A finite element analysis of frequency–temperature relations of AT-cut quartz crystal resonators with higher-order Mindlin plate theory
- Author
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Yook-Kong Yong, T. Imai, J.-D. Yu, and Ji Wang
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Materials science ,Field (physics) ,business.industry ,Mechanical Engineering ,Computational Mechanics ,Mechanics ,Finite element method ,Vibration ,Resonator ,Optics ,Normal mode ,Plate theory ,Solid mechanics ,Mode coupling ,business - Abstract
The frequency–temperature characteristics of quartz crystal resonators, particularly the frequency stability in a specific temperature range in which the vibration modes are strongly coupled, has been an important requirement in most applications. The analytical work on frequency–temperature relations has been done over the last decades in many aspects, ranging from the fundamental theory for the thermal effect on vibrations of elastic solids to simplified plate equations of a few strongly coupled vibration modes. However, it has been clearly observed that due to complications of the resonator structures such as the presence of a mounting structure and electrodes, simple and analytical solutions will not be able to consider all the factors which will have inevitable and noticeable effects. In this paper, we incorporate the frequency–temperature theory for crystal plates based on the incremental thermal field formulation by Lee and Yong into our finite element analysis implementation, which is then used to analyze the free vibrations of crystal plates with the higher-order Mindlin plate theory. The effect of electrodes on the frequency–temperature relation is also considered. The computational results are compared with experimental ones from actual products. The satisfactory agreement demonstrates the precise prediction of the frequency–temperature behavior and practical applications of the finite element analysis in product modeling and development.
- Published
- 2008
42. A Simple Photomask with Photoresist Mask Layer for Ultraviolet-Photolithography and Its Application for Selectively Photochemical Surface Modification of Polymers
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Yun Xiao, Fang Zhao-lun, Chen Heng-wu, Kong Yong, and Hao Zhen-Xia
- Subjects
business.industry ,Chemistry ,Gold plating ,Nanotechnology ,Photoresist ,medicine.disease_cause ,Analytical Chemistry ,law.invention ,Mercury-vapor lamp ,Colloidal gold ,law ,medicine ,Optoelectronics ,Surface modification ,Photomask ,Photolithography ,business ,Ultraviolet - Abstract
According to ultraviolet (UV) spectroscopic studies, a positive AZ photoresist film thicker than 10 (m can hardly transmit UV lights of wavelengths 200–285 nm. A simple photomask for UV photolithography was prepared using a quartz glass plate coated with a light-obstructing film of positive AZ photoresist, and the quality of the photomask and fidelity of the pattern transferred by the photomask were evaluated. The developed AZ photoresist photomask was used for fabrication of gold microelectrode on polycarbonate (PC) sheets. PC sheetswere exposed to the UV lights emitted from a low-pressure mercury lamp and passed through the photomask. The PC sheets were subjected to selective surface photolysis in the exposed area. After a series of wet chemical reactions, nano gold particles serving as the catalyst for electroless plating were deposited on the irradiated area. Gold microelectrodes were then generated by immersing the selectively activated PC sheet in an electroless gold plating bath for a specific time. Without need for a clean room, the photomasks can be prepared by a chemist in a common chemical laboratory with low-cost materials and simple procedures.
- Published
- 2007
43. Study on Trust Management-Based Cluster-Head Selection in Wireless Sensor Networks
- Author
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Yan Yi Xin and Kong Yong
- Subjects
Engineering ,Key distribution in wireless sensor networks ,Visual sensor network ,Wireless ad hoc network ,business.industry ,Wireless network ,Sensor node ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,Mobile wireless sensor network ,Wireless WAN ,business ,Wireless sensor network ,Computer network - Abstract
WSN (Wireless Sensor Networks) is a distributed sensor network, with its ends being the sensors able to sense and detect the external world. As the sensors in the WSN communicate in a wireless way, network setting is flexible and equipment location is uncertain. A wireless sensor network system typically includes end device, sink node and coordinator. The routing protocol in a wireless sensor network realizes information transmission by seeking the optimal path between the source node and the target node and its primary design goal is to improve the safety and reliability of the entire network. This paper focuses on the communication mode realized through cluster - head node selection based on the trust management mechanism introduced into the hierarchical routing protocol, and through MATLAB simulation test, the performance of use of trust management technology to select cluster-head nodes for communication transmission is made.
- Published
- 2015
44. Design of a novel length extension vibratory gyroscope
- Author
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Gobong Choi and Yook-Kong Yong
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Engineering ,Frequency response ,business.industry ,Acoustics ,Vibrating structure gyroscope ,Gyroscope ,Angular velocity ,Rotation ,Finite element method ,law.invention ,Vibration ,law ,Ring laser gyroscope ,Electronic engineering ,business - Abstract
In this paper, we introduce a novel design length extension vibratory gyroscope to detect the angular velocity rotation about z-axis. The proposed gyroscope is a new type of a gyroscope which utilizes a length extension mode as a driving mode and a flexure mode as a sensing mode to detect the Coriolis force generated by the rotation of the system. The gyroscope was designed and gyro-characteristics were simulated using COMSOL, finite element method (FEM) software. Quartz and langatate crystals are used for gyroscopes and compared. The driving frequencies and sensing frequencies of each gyroscope are obtained by optimizing the geometries of the each gyroscope using eigenfrequency analyses. Frequency response analyses were performed to simulate the gyro-characteristics of the gyroscopes which subjected to the angular velocity about z-axis. The results show that the length extension gyroscope can be used as a gyro-sensor. Moreover, we find that langatate crystals are more suitable materials for higher precision piezoelectric gyro-sensors than quartz crystal.
- Published
- 2015
45. Clinical Ophthalmic Presentations of Central Neurocytoma
- Author
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A. Loh, Kong Yong Goh, Jovina L. S. See, and M. Yang
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Round cells ,Pathology ,medicine.medical_specialty ,genetic structures ,business.industry ,Neuronal differentiation ,Central nervous system ,medicine.disease ,eye diseases ,Ophthalmology ,Rare tumor ,Lateral ventricles ,medicine.anatomical_structure ,medicine ,Foramen ,Central neurocytoma ,Neurology (clinical) ,Presentation (obstetrics) ,business - Abstract
Central neurocytoma is a rare tumor of the central nervous system occurring in young adults, typically located in the lateral ventricles and around the foramen of Monro. The neoplasm is composed of uniform round cells with neuronal differentiation and is associated with a varied biologic behavior. We report 2 cases of central neurocytomas presenting to the ophthalmologist as chronic progressive blurring of vision. The available literature on the presentation, pathology, and treatment of central neurocytomas is also reviewed.
- Published
- 2006
46. Application of a DC-bias to reduce acceleration sensitivity in quartz resonators
- Author
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Mihir S Patel and Yook-Kong Yong
- Subjects
Acceleration ,Materials science ,Mechanics of Materials ,business.industry ,Mechanical Engineering ,Quartz resonator ,Optoelectronics ,Sensitivity (control systems) ,Electrical and Electronic Engineering ,Condensed Matter Physics ,business ,Electronic, Optical and Magnetic Materials ,DC bias - Published
- 2005
47. On the correction of the higher-order Mindlin plate theory
- Author
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Jiun-Der Yu, Yook-Kong Yong, and Ji Wang
- Subjects
Power series ,business.industry ,Mechanical Engineering ,Mathematical analysis ,Mindlin–Reissner plate theory ,Structural engineering ,Elasticity (physics) ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Vibration ,Mechanics of Materials ,Normal mode ,Plate theory ,Flexural vibration ,Electrical and Electronic Engineering ,High frequency vibration ,business ,Mathematics - Abstract
The Mindlin plate theory was developed to provide accurate solutions of vibrations in the vicinity of the fundamental thickness-shear mode, which has a very high frequency compared to flexural vibrations. The most important application of the theory is the high frequency vibrations of crystal plates although it has been applied to many problems beyond the original purpose. Recent studies found that, to improve the frequency solutions for plates with larger aspect ratios, the third-order plate based on Mindlin's power series expansion has to be used. It was shown through comparisons with three-dimensional elasticity solutions that the fundamental thickness-shear frequency is almost exact. The third-order theory was applied to frequency, mode shape, and other related analyses. In this study, we reconfirm that the third-order plate theory is very accurate because it has an almost exact cut-off frequency for the fundamental thickness-shear mode. By adopting a procedure developed by Mindlin, we find the inaccuracies in cut-off frequencies of the fundamental thickness modes and their overtones can be improved through the introduction of new correction factors. Corrections can be made with either the natural or symmetric procedure. Correction factors for natural and symmetric procedures based on stresses will be given.
- Published
- 2005
48. Parasellar aneurysm mimicking an optic neuritis
- Author
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Jin Fong Cheng and Kong Yong Goh
- Subjects
medicine.medical_specialty ,genetic structures ,medicine.diagnostic_test ,business.industry ,medicine.medical_treatment ,Optic chiasm ,Magnetic resonance imaging ,Clipping (medicine) ,medicine.disease ,eye diseases ,Surgery ,Optic neuropathy ,Lesion ,Ophthalmology ,Aneurysm ,medicine.anatomical_structure ,Neuroimaging ,Medicine ,Optic neuritis ,Neurology (clinical) ,medicine.symptom ,business - Abstract
An acute painful unilateral loss of vision in a young adult with obvious signs and symptoms of optic neuropathy usually suggests a diagnosis of optic neuritis. However, a similar clinical picture can be caused by a compressive lesion in the anterior visual pathways. Although such lesions are rare, they can only be diagnosed through neuroimaging studies.We describe a 37-year-old Chinese female, who presented with mild pain and decreased vision in the left eye two weeks prior to consultation. A diagnosis of retrobulbar optic neuritis was made and she underwent pulsed intravenous therapy of 1 g methyl-prednisolone daily over three days. The magnetic resonance imaging done three days later showed a partially thrombosed paraseller aneurysm, abutting and displacing the optic chiasm laterally. She underwent a right temporal craniotomy and clipping of the aneurysm. This report highlights the importance of neuroimaging in unmasking compressive lesions in patients presenting with presumed optic neuritis.
- Published
- 2004
49. Reduction of frequency deviations in quartz resonators by electric potentials of plate electrodes
- Author
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Jianfeng Chen, Randall L. Kubena, David T. Chang, Yook-Kong Yong, and Deborah J. Kirby
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Body force ,Physics ,Acceleration ,Resonator ,Optics ,business.industry ,Direct current ,Electrode ,Perpendicular ,Sensitivity (control systems) ,Mechanics ,business ,Finite element method - Abstract
We present a new method in which a direct current (DC) bias field is used to control the resonant frequency of resonator subjected to body forces. The plate electrodes were used to create the DC bias field. Sensing electrodes were used to measure the body forces that cause the acceleration sensitivity. Finite element models were developed using the theory of small deformations superposed on finite initial deformations in Lagrangian formulation. The model results compared consistently well with the measured values for the force sensitivity coefficient K f of a circular plate subjected to a pair of diametrical forces; hence validating our model for acceleration sensitivity. For our 1 GHz AT-cut quartz plate resonator with the crystal digonal X-axis perpendicular to plate X-axis, the in-plane acceleration sensitivity is negligible, while the Y-axis acceleration sensitivity is maximum. A DC bias field with an appropriate DC bias voltage could yield a reduction in acceleration sensitivity from 10−10/g to 10−12/g in the Y-axis
- Published
- 2014
50. Special amplitude-frequency effects in VHF quartz resonators
- Author
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Joyce Richard, Rose Brian, Yook-Kong Yong, and Kubena Randall
- Subjects
Physics ,business.industry ,Overtone ,Mode (statistics) ,Resonance ,Signal ,Nonlinear system ,Resonator ,Amplitude ,Optics ,Astrophysics::Solar and Stellar Astrophysics ,Physics::Chemical Physics ,business ,Coupling coefficient of resonators - Abstract
High drive levels of the fundamental mode of a quartz shear-mode resonator can result not only in a frequency shift of the fundamental mode (amplitude-frequency effect) but also in nonlinear interactions with the third overtone mode. One such interaction reported here is a frequency shift of the third overtone mode. In addition, the third harmonic of the fundamental driving signal is generated which can appear close to, or directly at the third overtone resonance, depending on the relationship between the fundamental mode and third overtone mode frequencies. We examine these effects in 33-MHz fundamental mode AT-cut and SC-cut quartz resonators in which the fundamental mode and third overtone mode frequencies were closely matched by design.
- Published
- 2014
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