1,505 research outputs found

    Stable controller design for linear systems

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    This paper is concerned with the problem of suboptimal stable mixed H2/H∞ control for linear time-invariant systems. The designed controllers are required to satisfy a prescribed H∞ performance bound or a prescribed degree of stability. By reducing the stable controller synthesis problem to a multiobjective state feedback control problem for two different state models, sufficient conditions for the solvability of the considered problem are given in terms of solutions to algebraic Riccati equations and matrix inequalities. LMI-based iterative algorithms are developed to solve the stable controller synthesis problem. All of the proposed algorithms are shown to be convergent. An example is given to illustrate the proposed methods.published_or_final_versio

    Plasma fibrinogen level as a predictor of incident metabolic syndrome in a community-based prospective study in Hong Kong Chinese

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    BACKGROUND AND AIMS: Metabolic syndrome (MS) comprises a constellation of metabolic abnormalities associated with a high risk of developing diabetes and cardiovascular diseases. Central obesity, with related insulin resistance and inflammation are considered the core of the underlying pathogenesis of MS. Fibrinogen, an acute-phase reactant in the coagulation cascade, has been shown to play pivotal role in determining the extent of local or systemic inflammation. In this study, we examined whether plasma fibrinogen was predictive of incident MS in a community-based Chinese cohort. MATERIALS AND METHODS: Subjects were recruited from the Hong Kong Cardiovascular Risk Factors Prevalence Study (CRISPS) cohort. 2780 subjects were recruited in 1995-6 with baseline assessment performed. 1416 subjects without MS at …postprin

    Predictors common to cardiovascular and cancer outcomes in a population-based 13-year prospective study in Hong Kong

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    Oral PresentationINTRODUCTION: Cardiovascular diseases (CVD) and cancer are the two leading causes of death in Hong Kong. Obesity is becoming increasingly prevalent in the local population and has been reported to be associated with CVD and some forms of cancer in the western world. In this study, we attempted to identify the aetiological factors linking obesity to both CVD and cancer among Hong Kong Chinese. METHODS: Subjects were recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS) …published_or_final_versionThe 16th Medical Research Conference, The University of Hong Kong, Hong Kong, 22 January 2011. In Hong Kong Medical Journal, 2011, v. 17 suppl. 1, p. 56, abstract no. 9

    Serum adiponectin in relation to other obesity-related biomarkers in predicting type 2 diabetes: a 5-year prospective study

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    Oral PresentationAIMS: To identify obesity-related serum biomarkers associated with the development of type 2 diabetes in a Chinese population and to examine if these biomarkers added values to conventional risk factors in diabetes prediction. METHODS: We studied 1315 non-diabetic subjects from the prospective Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS). Serum biomarkers including adiponectin, tumour necrosis …published_or_final_versionThe 17th Medical Research Conference, The University of Hong Kong, Hong Kong, 14 January 2012. In Hong Kong Medical Journal, 2012, v. 18 suppl. 1, p. 57, abstract no. 8

    Chemotherapy of tuberculosis in Hong Kong: a consensus statement

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    This consensus statement is prepared primarily as a concise reference for tuberculosis chemotherapy in Hong Kong. Treatment should be tailored to patients individually, expert advice should be sought when necessary, and 'directly observed treatment' should be used where possible. A 6-month regimen is recommended as the initial treatment of uncomplicated pulmonary tuberculosis and a 9-month regimen is recommended for retreatment. Patients with disease that is resistant to isoniazid or rifampicin may require modified regimens. Multidrug-resistant tuberculosis should be managed in specialised centres, using multiple drugs as guided by in vitro susceptibility tests. Recommended regimens to treat extrapulmonary tuberculosis are based on limited current evidence, although shorter regimens may be acceptable when better evidence emerges. A longer duration of treatment is required for diabetic, immuno-compromised, or silicotic patients. During pregnancy, streptomycin should be avoided; the safety profiles of second-line drugs have not yet been ascertained. Hepatotoxic drugs should be used with caution in patients with liver dysfunction, and extra caution and dosage reductions are required if streptomycin and ethambutol are used in patients with renal impairment.published_or_final_versio

    Serum fibroblast growth factor 21 is a superior biomarker to other adipokines in predicting incident diabetes

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    OBJECTIVE: Fibroblast growth factor 21 (FGF21) improves glucose and lipid metabolism, but high circulating levels are found in type 2 diabetes, suggesting FGF21 resistance. Serum FGF21 predicts incident diabetes, but its performance compared to established and emerging predictors is not known. We aimed to study the performance of FGF21 in diabetes prediction, relative to other adipokines and established risk factors including 2-h plasma glucose (2hG) during the oral glucose tolerance test (OGTT). DESIGN/PARTICIPANTS/MEASUREMENTS: We studied 1380 nondiabetic subjects from the Hong Kong Cardiovascular Risk Factor Prevalence Study using the second visit (2000-2004) as baseline when serum levels of FGF21 and other adipokines were measured. Glycaemic status was assessed by OGTT. Incident diabetes was defined as fasting glucose level (FG) ≥ 7 mmol/l or 2hG ≥ 11·1 mmol/l or use of antidiabetic agents, at subsequent visits. RESULTS: A total of 123 participants developed diabetes over 9·0 years (median). On multivariable logistic regression analysis, FGF21 (P = 0·003), adipocyte fatty acid-binding protein (P = 0·003) and adiponectin (P = 0·035) were independent predictors of incident diabetes. FGF21 had the best change in log likelihood when added to a diabetes prediction model (DP) based on age, family history, smoking, hypertension, BMI, dyslipidaemia and FG. It also improved the area under ROC curve (AUROC) of diabetes prediction (DP) from 0·797 to 0·819 (P = 0·0072), rendering its performance comparable to the 'DP + 2hG' model (AUROC=0·838, P = 0·19). CONCLUSIONS: As a biomarker for diabetes prediction, serum FGF21 appeared to be superior to other adipokines and, on its own, could be considered as an alternative to the OGTT. © 2016 John Wiley & Sons Ltd.postprin

    Photoinduced Dehydrogenation of Defects in Undoped a-Si:H Using Positron Annihilation Spectroscopy

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    We report changes in variable-energy positron annihilation spectroscopy measurements on undoped hydrogenated amorphous silicon films after light soaking. The change, seen predominantly in the high momentum band of the annihilation radiation, is not reversed by thermal annealing. We suggest, following recent models of the Staebler-Wronski effect, that light exposure induces hydrogen trapped in vacancylikc detects to become mobile in the Si network. The observations place constraints on models of hydrogen motion fitting macroscopic Staebler-Wronski effect kinetics and may help to achieve a definitive description of metastability in a-Si:H.published_or_final_versio

    Dynamic dyssynchrony and impaired contractile reserve of the left ventricle in beta-thalassaemia major: an exercise echocardiographic study

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    BACKGROUND: Performance of the left ventricle during exercise stress in thalassaemia patients is uncertain. We aimed to explore the phenomenon of dynamic dyssynchrony and assess contractile reserve in patients with beta-thalassaemia major and determine their relationships with myocardial iron load. METHODS AND RESULTS: Thirty-two thalassaemia patients (16 males), aged 26.8+/-6.9 years, without heart failure and 17 healthy controls were studied. Their left ventricular (LV) volumes, ejection fraction, systolic dyssynchrony index (SDI), and myocardial acceleration during isovolumic LV contraction (IVA) were determined at rest and during submaximal bicycle exercise testing using 3-dimensional and tissue Doppler echocardiography. Myocardial iron load as assessed by T2* cardiac magnetic resonance in patients were further related to indices of LV dyssynchrony and contractile reserve. At rest, patients had significantly greater LV SDI (p4.6%, control+2SD) increased from baseline 25% to 84% in patients. Delta SDI(exercise-baseline) correlated with exercise-baseline differences in LV ejection fraction (p<0.001) and stroke volume (p = 0.006). Compared with controls, patients had significantly less exercise-induced increase in LV ejection fraction, cardiac index, and IVA (interaction, all p<0.05) and had impaired contractile reserve as reflected by the gentler IVA-heart rate slope (p = 0.018). Cardiac T2* in patients correlated with baseline LV SDI (r = -0.44, p = 0.011) and IVA-heart rate slope (r = 0.36, p = 0.044). CONCLUSIONS: Resting LV dyssynchrony is associated with myocardial iron load. Exercise stress further unveils LV dynamic dyssynchrony and impaired contractile reserve in patients with beta-thalassaemia major.published_or_final_versio
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