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Search Results: 1 - 10 of 206919 matches for " Joshua G. X. Wong "
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Risk Factors for Fatality among Confirmed Adult Dengue Inpatients in Singapore: A Matched Case-Control Study
Tun-Linn Thein, Yee-Sin Leo, Dale A. Fisher, Jenny G. Low, Helen M. L. Oh, Victor C. Gan, Joshua G. X. Wong, David C. Lye
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081060
Abstract: Objectives To identify demographic, clinical and laboratory risk factors for death due to dengue fever in adult patients in Singapore. Methods Multi-center retrospective study of hospitalized adult patients with confirmed dengue fever in Singapore between 1 January 2004 and 31 December 2008. Non-fatal controls were selected by matching age and year of infection with fatal cases. World Health Organization 1997, 2009 criteria were applied to define dengue hemorrhagic fever (DHF), warning signs and severe dengue. Statistical significance was assessed by conditional logistic regression modeling. Results Significantly more fatal cases than matched controls had pre-existing co-morbid conditions, and presented with abdominal pain/tenderness. Median pulse rates were significantly higher while myalgia was significantly less frequent in cases. . Fatal cases also had higher leucocyte counts, platelet counts, serum sodium, potassium, urea, creatine and bilirubin levels on admission compared to controls. There was no statistical significant difference between the prevalence of DHF and hematocrit level among cases and controls. Multivariate analysis showed myalgia and leucocyte count at presentation were independent predictors of fatality (adjusted odds ratios 0.09 and 2.94 respectively). None of the controls was admitted to intensive care unit (ICU) or given blood transfusion, while 71.4% and 28.6% of fatal cases received ICU admission and blood transfusion. Conclusions Absence of myalgia and leucocytosis on admission were independently associated with fatality in our matched case-control study. Fatalities were also commonly associated with co-morbidities and clinicians should be alarmed if dengue patients fulfilled severe dengue case definition on admission.
Challenges in Dengue Fever in the Elderly: Atypical Presentation and Risk of Severe Dengue and Hospita-Acquired Infection
Emily K. Rowe ,Yee-Sin Leo,Joshua G. X. Wong,Tun-Linn Thein,Victor C. Gan,Linda K. Lee,David C. Lye
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002777
Abstract: Background/methods To better understand dengue fever in the elderly, we compared clinical features, World Health Organization (WHO) dengue classification and outcomes between adult (<60) and elderly (≥60) dengue patients. We explored the impact of co-morbidity and hospital-acquired infection (HAI) on clinical outcomes in the elderly. All patients managed at the Communicable Disease Centre, Singapore, between 2005 and 2008 with positive dengue polymerase chain reaction (PCR) or who fulfilled WHO 1997 or 2009 probable dengue criteria with positive dengue IgM were included. Results Of the 6989 cases, 295 (4.4%) were elderly. PCR was positive in 29%. The elderly suffered more severe disease with more dengue haemorrhagic fever (DHF) (29.2% vs. 21.4%) and severe dengue (SD) (20.3% vs. 14.6%) (p<0.05). Classic dengue symptoms were more common in the adult group. The elderly were less likely to fulfill WHO 1997 (93.6% vs. 96.4%) (p = 0.014), but not WHO 2009 probable dengue (75.3% vs. 71.5%). Time to dengue diagnosis was similar. There was no significant difference in the frequency of warning signs between the two groups, but the elderly were more likely to have hepatomegaly (p = 0.006) and malaise/lethargy (p = 0.033) while the adults had significantly more mucosal bleeding (p<0.001). Intensive care admission occurred in 15 and death in three, with no age difference. Notably, the elderly stayed in hospital longer (median 5 vs. 4 days), and suffered more pneumonia (3.8% vs. 0.7%) and urinary infection (1.9% vs. 0.3%) (p = 0.003). Predictors of excess length of stay were age (adjusted odds ratio [aOR] 2.01, 95% confidence interval [CI] 1.37–2.88), critical illness (aOR 5.13, 95%CI 2.59–9.75), HAI (aOR 12.06, 95%CI 7.39–19.9), Charlson score (aOR 6.9, 95%CI 2.02–22.56) and severe dengue (DHF/dengue shock syndrome/SD) (aOR 2.24, 95%CI 1.83–2.74). Conclusion Elderly dengue patients present atypically and are at higher risk of DHF, SD and HAI. Aside from dengue severity, age, co-morbidity and HAI were associated with longer hospital stay.
Self-Reported Pain Intensity with the Numeric Reporting Scale in Adult Dengue
Joshua G. X. Wong, Victor C. Gan, Ee-Ling Ng, Yee-Sin Leo, Siew-Pang Chan, Robin Choo, David C. Lye
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0096514
Abstract: Background Pain is a prominent feature of acute dengue as well as a clinical criterion in World Health Organization guidelines in diagnosing dengue. We conducted a prospective cohort study to compare levels of pain during acute dengue between different ethnicities and dengue severity. Methods Demographic, clinical and laboratory data were collected. Data on self-reported pain was collected using the 11-point Numerical Rating Scale. Generalized structural equation models were built to predict progression to severe disease. Results A total of 499 laboratory confirmed dengue patients were recruited in the Prospective Adult Dengue Study at Tan Tock Seng Hospital, Singapore. We found no statistically significant differences between pain score with age, gender, ethnicity or the presence of co-morbidity. Pain score was not predictive of dengue severity but highly correlated to patients’ day of illness. Prevalence of abdominal pain in our cohort was 19%. There was no difference in abdominal pain score between grades of dengue severity. Conclusion Dengue is a painful disease. Patients suffer more pain at the earlier phase of illness. However, pain score cannot be used to predict a patient’s progression to severe disease.
An improved beam waist formula for ultrashort, tightly-focused linearly, radially, and azimuthally polarized laser pulses in free space
Liang Jie Wong,Franz X. K?rtner,Steven G. Johnson
Physics , 2013, DOI: 10.1364/OL.39.001258
Abstract: We derive an asymptotically accurate formula for the beam waist of ultrashort, tightly-focused fundamental linearly-polarized, radially-polarized, and azimuthally-polarized modes in free space. We compute the exact beam waist via numerical cubature to ascertain the accuracy with which our formula approximates the exact beam waist over a broad range of parameters of practical interest. Based on this, we describe a method of choosing parameters in the model given the beam waist and pulse duration of a laser pulse.
Detecting Novel Genetic Variants Associated with Isoniazid-Resistant Mycobacterium tuberculosis
Sandhya Shekar, Zhen Xuan Yeo, Joshua C. L. Wong, Maurice K. L. Chan, Danny C. T. Ong, Pumipat Tongyoo, Sin-Yew Wong, Ann S. G. Lee
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102383
Abstract: Background Isoniazid (INH) is a highly effective antibiotic central for the treatment of Mycobacterium tuberculosis (MTB). INH-resistant MTB clinical isolates are frequently mutated in the katG gene and the inhA promoter region, but 10 to 37% of INH-resistant clinical isolates have no detectable alterations in currently known gene targets associated with INH-resistance. We aimed to identify novel genes associated with INH-resistance in these latter isolates. Methodology/Principal Findings INH-resistant clinical isolates of MTB were pre-screened for mutations in the katG, inhA, kasA and ndh genes and the regulatory regions of inhA and ahpC. Twelve INH-resistant isolates with no mutations, and 17 INH-susceptible MTB isolates were subjected to whole genome sequencing. Phylogenetically related variants and synonymous mutations were excluded and further analysis revealed mutations in 60 genes and 4 intergenic regions associated with INH-resistance. Sanger sequencing verification of 45 genes confirmed that mutations in 40 genes were observed only in INH-resistant isolates and not in INH-susceptible isolates. The ratios of non-synonymous to synonymous mutations (dN/dS ratio) for the INH-resistance associated mutations identified in this study were 1.234 for INH-resistant and 0.654 for INH-susceptible isolates, strongly suggesting that these mutations are indeed associated with INH-resistance. Conclusion The discovery of novel targets associated with INH-resistance described in this study may potentially be important for the development of improved molecular detection strategies.
High-Resolution Melting Analysis for the Rapid Detection of Fluoroquinolone and Streptomycin Resistance in Mycobacterium tuberculosis
Ann S. G. Lee, Danny C. T. Ong, Joshua C. L. Wong, Gilman K. H. Siu, Wing-Cheong Yam
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031934
Abstract: Background Molecular methods for the detection of drug-resistant tuberculosis are potentially more rapid than conventional culture-based drug susceptibility testing, facilitating the commencement of appropriate treatment for patients with drug resistant tuberculosis. We aimed to develop and evaluate high-resolution melting (HRM) assays for the detection of mutations within gyrA, rpsL, and rrs, for the determination of fluoroquinolone and streptomycin resistance in Mycobacterium tuberculosis (MTB). Methodology/Principal Findings A blinded series of DNA samples extracted from a total of 92 clinical isolates of MTB were analyzed by HRM analysis, and the results were verified using DNA sequencing. The sensitivity and specificity of the HRM assays in comparison with drug susceptibility testing were 74.1% and 100.0% for the detection of fluoroquinolone resistance, and 87.5% and 100.0% for streptomycin resistance. Five isolates with low level resistance to ofloxacin had no mutations detected in gyrA, possibly due to the action of efflux pumps, or false negativity due to mixed infections. One fluoroquinolone-resistant isolate had a mutation in a region of gyrA not encompassed by our assay. Six streptomycin-resistant strains had undetectable mutations by HRM and DNA sequencing, which may be explained by the fact that not all streptomycin-resistant isolates have mutations within rpsL and rrs, and suggesting that other targets may be involved. Conclusion The HRM assays described here are potentially useful adjunct tests for the efficient determination of fluoroquinolone and streptomycin resistance in MTB, and could facilitate the timely administration of appropriate treatment for patients infected with drug-resistant TB.
Effect of suprathermal electrons on central plasma relaxation oscillations during localized electron cyclotron heating on the HL-1M Tokamak
Liu, Y.;Guo, G.C.;Ding, X.T.;Wong, K.L.;
Brazilian Journal of Physics , 2002, DOI: 10.1590/S0103-97332002000100022
Abstract: in this paper we discuss the typical behavior of hl-1m tokamak plasmas during ecrh. a large variety ofsawtooth types have been observed at different ech power deposition locations. the observed central mhd activities detected by the soft x-ray diode array include saturated sawtooth, partially saturated sawtooth, double sawtooth, and strong m=1 bursts superimposed on the ramp phase of sawtooth. complete suppression of sawtooth is achieved during ecrh, when the heating power is applied on the high-field side of low-density plasmas, and exceeds a threshold value of power. the m=1 bursts riding on the ramp phase of sawtooth can only be excited when the ecrh location is near the q=1 surface at the high field side. the conditions under which the various relaxation activities are produced, or suppressed, are described. experimental results imply that the energetic electrons, generated during ecrh, are responsible for the modification or stabilization or excitation of the instability. near the q=1 surface, while the passing electrons play a roleto reduce the shear and tend to stabilize the sawtooth activity, the barely-trapped electrons play a role to enhance or drive aninternal kink instability.
Effect of suprathermal electrons on central plasma relaxation oscillations during localized electron cyclotron heating on the HL-1M Tokamak
Liu Y.,Guo G.C.,Ding X.T.,Wong K.L.
Brazilian Journal of Physics , 2002,
Abstract: In this paper we discuss the typical behavior of HL-1M tokamak plasmas during ECRH. A large variety ofsawtooth types have been observed at different ECH power deposition locations. The observed central MHD activities detected by the soft x-ray diode array include saturated sawtooth, partially saturated sawtooth, double sawtooth, and strong m=1 bursts superimposed on the ramp phase of sawtooth. Complete suppression of sawtooth is achieved during ECRH, when the heating power is applied on the high-field side of low-density plasmas, and exceeds a threshold value of power. The m=1 bursts riding on the ramp phase of sawtooth can only be excited when the ECRH location is near the q=1 surface at the high field side. The conditions under which the various relaxation activities are produced, or suppressed, are described. Experimental results imply that the energetic electrons, generated during ECRH, are responsible for the modification or stabilization or excitation of the instability. Near the q=1 surface, while the passing electrons play a roleto reduce the shear and tend to stabilize the sawtooth activity, the barely-trapped electrons play a role to enhance or drive aninternal kink instability.
Comparison Tests of Variable-Stepsize Algorithms for Stochastic Ordinary Differential Equations of Finance
Yin Mei Wong,Joshua Wilkie
Physics , 2006,
Abstract: Since the introduction of the Black-Scholes model stochastic processes have played an increasingly important role in mathematical finance. In many cases prices, volatility and other quantities can be modeled using stochastic ordinary differential equations. Available methods for solving such equations have until recently been markedly inferior to analogous methods for deterministic ordinary differential equations. Recently, a number of methods which employ variable stepsizes to control local error have been developed which appear to offer greatly improved speed and accuracy. Here we conduct a comparative study of the performance of these algorithms for problems taken from the mathematical finance literature.
Integrated and Seamless Services for Active Aging, a Model for Zhuhai  [PDF]
H. C. J. Wong, Y. F. Ng, X. L. Yuan
Journal of Biosciences and Medicines (JBM) , 2014, DOI: 10.4236/jbm.2014.26007
Abstract:

The Aging Tsunami as it is often quoted to describe the worrying situations of rapidly aging in China has not met with detail planning in facilities upgrade and careful consideration in service models. Broad brushed central policies categorizes services into home care, community care and institutional care and set policy goals at 90-6-4, representing the percentage of older people in receiving respective care. This leaves local officials helpless on how these ideals can be actualized. Some cities have inclined to build huge older people homes and pour resources into institutional care, forgetting the need for older people to be connected with the society. This paper reviews the historical developments of older people services in Hong Kong and recommends an integrative model of social work services connecting institutional, community and home care into a seamless network. The city of Zhuhai will be presented as a perfect experimental city on how its existing facilities can be converted and developed according to the model. Survey on the situations of the 16 public older people homes will be used to illustrate the potentials of an integrative model.

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