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Wong RJ, Nguyen MT, Trinh HN, Huynh A, Ly MT, Nguyen HA, Nguyen KK, Yang J, Garcia RT, Levitt B, da Silveira E, Gish RG. Community-based real-world treatment outcomes of sofosbuvir/ledipasvir in Asians with chronic hepatitis C virus genotype 6 in the United States. J Viral Hepat 2017; 24:17-21. [PMID: 27677786 DOI: 10.1111/jvh.12609] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 08/23/2016] [Indexed: 01/08/2023]
Abstract
Sofosbuvir/ledipasvir (SOF/LDV) is the first all-oral ribavirin-free treatment approved for chronic hepatitis C virus (HCV) genotype 6, offering a safe and highly efficacious treatment option. Large studies evaluating real-world outcomes of this regimen are lacking. We aim to evaluate real-world treatment outcomes for HCV genotype 6. A retrospective cohort study evaluated 65 adults (age ≥18) with chronic HCV genotype 6 treated with SOF/LDV without ribavirin at a community gastroenterology clinic in the United States from November 2014 to May 2016. Rates of undetectable virus at week 4 on treatment, at end of treatment (EOT) and SVR12 were stratified by the presence of cirrhosis and prior treatment (treatment naïve vs treatment experienced). Among 65 patients with chronic HCV genotype 6 treated with SOF/LDV (52.3% male, mean age 66.3 years [SD 9.7], 41.5% cirrhosis and 15.4% treatment experienced), 97.3% had undetectable virus at week 4 on treatment, 96.9% had undetectable virus at EOT and 95.3% achieved SVR12. SVR12 was 100% in females vs 91.2% in males, P=.096, and 92.3% in patients with cirrhosis vs 97.4% in those without cirrhosis, P=.347. Resistance testing of treatment failures was attempted but unsuccessful due to lack of conforming primers to define the possible resistance mutations. Among the largest U.S. community-based real-world cohort of Asian chronic HCV genotype 6 patients treated with all-oral SOF/LDV without ribavirin, SVR12 was similar to SVR12 reported in clinical trials, confirming the safety and effectiveness of this regimen and validating current HCV genotype 6 treatment guideline recommendations.
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Chen Q, Chiheb S, Fysekidis M, Jaber Y, Brahimi M, Nguyen MT, Millasseau S, Cosson E, Valensi P. Arterial stiffness is elevated in normotensive type 2 diabetic patients with peripheral neuropathy. Nutr Metab Cardiovasc Dis 2015; 25:1041-1049. [PMID: 26474725 DOI: 10.1016/j.numecd.2015.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Revised: 06/19/2015] [Accepted: 08/02/2015] [Indexed: 12/22/2022]
Abstract
BACKGROUND AND AIMS Arterial stiffness, a measure of macrovascular damage predictive of poor cardio-vascular outcomes, is strongly related to age and hypertension (HT). In diabetic patients peripheral neuropathy (PN) has been found to be associated with increased arterial stiffness, which might be due to the concomitant presence of HT. The aim of this study was to examine in type-2 diabetic patients, the relationship between arterial stiffness and presence or absence of PN and HT separately. METHODS AND RESULTS Arterial stiffness was measured with the gold standard carotid-femoral pulse wave velocity (PWV) in 447 type-2 diabetic subjects of whom 66% were hypertensive, 53% had PN, and 40% had both. Patients with PN were older, more often hypertensive and had higher PWV than those free of PN. Patients were separated according to the presence or absence of PN and HT. PWV values above the 90th percentile age- and blood pressure-adjusted reference range (PWV+) were different across these groups (p < 0.005) with the following respective prevalences: 27.2%, 53.4%, 33.3% and 30.6%. Only PWV+ was significantly associated with PN and hypertension in the interaction analysis. CONCLUSION Well controlled hypertensive patients did not have elevated arterial stiffness compared to normotensive patients. This might be due to anti-hypertensive treatment although our study design does not allow us to confirm it. A strong association between PN and arterial stiffness was only present in normotensive patients, suggesting that normotensive type 2 diabetic patients with PN and elevated arterial stiffness should be carefully managed to prevent future macrovascular complications.
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Nguyen MT, Charlebois K. The clinical utility of whole-exome sequencing in the context of rare diseases - the changing tides of medical practice. Clin Genet 2015; 88:313-9. [PMID: 25421945 DOI: 10.1111/cge.12546] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 10/30/2014] [Accepted: 11/21/2014] [Indexed: 01/07/2023]
Abstract
Whole-exome sequencing (WES) carries the potential to facilitate the identification of disease causing genes. This is particularly relevant concerning rare diseases, which proves particularly difficult for physicians to diagnose. However, the complexity of this technology renders its applicability onto the clinical setting uncertain. Our study thus aims to understand physicians' perspectives regarding the clinical utility of WES, particularly for providing a diagnosis for patients with rare diseases. Ten semi-structured interviews were conducted with physicians with experience and familiarity with WES, and the major themes that emerged from our interviews were (i) the relevance of WES in diagnosing patients with rare diseases (appropriateness); (ii) the cost-effectiveness of WES (accessibility), (iii) the practical issues related to the clinical implementation of WES (practicability); and (iv) ethical, legal and social issues (acceptability). Our study highlights how the clinical implementation of WES presents additional challenges where rare diseases are taken into consideration.
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Nguyen MT, Pham I, Chemla D, Valensi P, Cosson E. Decreased stroke volume−brachial pulse pressure ratio in patients with type 2 diabetes over 50 years: the role of peripheral neuropathy. Nutr Metab Cardiovasc Dis 2013; 23:1093-1100. [PMID: 23541167 DOI: 10.1016/j.numecd.2013.01.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2012] [Revised: 01/11/2013] [Accepted: 01/15/2013] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND AIMS To document the stroke volume to pulse pressure ratio (SV/PP, an index of total arterial compliance) and its correlates in patients with type 2 diabetes (T2DM) aged over 50 years whose peripheral neuropathy and silent myocardial ischemic (SMI) status were known. METHODS AND RESULTS A total of 360 patients with T2DM aged ≥ 50 years, without cardiac history or symptom, left ventricular systolic dysfunction, dilatation and hypokinesia, were retrospectively enrolled. The SV/PP was calculated from echocardiographic left ventricular measurements and brachial blood pressure at rest. Peripheral neuropathy was defined as the presence of any two or more of the following: neuropathic symptoms, decreased distal sensation, or decreased or absent ankle reflexes. SMI was defined as an abnormal stress myocardial scintigraphy and/or stress echocardiography. A low SV/PP ratio (<0.53 ml/m²/mmHg, first tertile) was associated with age, creatinine clearance, 24 h urinary albumin excretion rate, peripheral neuropathy, hypertension, serum total cholesterol and triglycerides levels (p < 0.05-0.0001). In multivariate analysis, age (OR 1.1 [1.0-1.2], p < 0.01), triglycerides (OR 1.5 [1.2-2.0], p = 0.01) and peripheral neuropathy (OR 2.2 [1.2-3.9], p = 0.009) were independently associated with a low SV/PP. The patients with peripheral neuropathy had lower SV (p < 0.01) and higher PP (p < 0.05) than those without, and only lower SV after adjustment for age and nephropathy. Similar results were obtained in the patients with and without SMI. CONCLUSION Peripheral neuropathy was independently associated with decreased SV/PP, mainly through decreased SV, in patients with T2DM over 50 years.
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Nguyen MT, Csermely P, Sőti C. Hsp90 chaperones PPARγ and regulates differentiation and survival of 3T3-L1 adipocytes. Cell Death Differ 2013; 20:1654-63. [PMID: 24096869 DOI: 10.1038/cdd.2013.129] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 07/24/2013] [Accepted: 08/21/2013] [Indexed: 11/09/2022] Open
Abstract
Adipose tissue dysregulation has a major role in various human diseases. The peroxisome proliferator-activated receptor-γ (PPARγ) is a key regulator of adipocyte differentiation and function, as well as a target of insulin-sensitizing drugs. The Hsp90 chaperone stabilizes a diverse set of signaling 'client' proteins, thereby regulates various biological processes. Here we report a novel role for Hsp90 in controlling PPARγ stability and cellular differentiation. Specifically, we show that the Hsp90 inhibitors geldanamycin and novobiocin efficiently impede the differentiation of murine 3T3-L1 preadipocytes. Geldanamycin at higher concentrations also inhibits the survival of both developing and mature adipocytes, respectively. Further, Hsp90 inhibition disrupts an Hsp90-PPARγ complex, leads to the destabilization and proteasomal degradation of PPARγ, and inhibits the expression of PPARγ target genes, identifying PPARγ as an Hsp90 client. A similar destabilization of PPARγ and a halt of adipogenesis also occur in response to protein denaturing stresses caused by a single transient heat-shock or proteasome inhibition. Recovery from stress restores PPARγ stability and adipocyte differentiation. Thus, our findings reveal Hsp90 as a critical stress-responsive regulator of adipocyte biology and offer a potential therapeutic target in obesity and the metabolic syndrome.
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Cosson E, Nguyen MT, Chanu B, Balta S, Takbou K, Valensi P. The report of male gender and retinopathy status improves the current consensus guidelines for the screening of myocardial ischemia in asymptomatic type 2 diabetic patients. Nutr Metab Cardiovasc Dis 2013; 23:557-565. [PMID: 22502874 DOI: 10.1016/j.numecd.2012.01.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 12/30/2011] [Accepted: 01/25/2012] [Indexed: 11/21/2022]
Abstract
BACKGROUND AND AIMS American Diabetes Association (ADA), French-speaking Societies for diabetes & cardiology (ALFEDIAM-SFC) and Cardiac Radionuclide Imaging (CRI) have proposed guidelines for the screening of silent myocardial ischemia (SMI). The aim of the study was to evaluate their diagnostic values and how to improve them. METHODS AND RESULTS 731 consecutive type 2 diabetic patients with ≥1 additional risk factor were screened between 1992 and 2006 for SMI by stress myocardial scintigraphy and for silent coronary artery disease (CAD) by coronary angiography. A total of 215 (29.4%) patients had SMI, and 79 of them had CAD. ADA (Odds Ratio 1.7 [95% Confidence Interval: 1.2-2.5]; p < 0.05), ALFEDIAM-SFC (OR 1.5 [1.0-2.5], p < 0.05) and CRI criteria (OR 2.0 [1.4-2.8], p < 0.01) predicted SMI. Considering the presence of male gender and retinopathy added to the prediction of SMI allowed by ADA criteria (c statistic: area under the curve AROC 0.651 [0.605-0.697] versus 0.582 [0.534-0.630]), p < 0.01 and ALFEDIAM-SFC criteria (AROC 0.672 [0.620-0.719] versus 0.620 [0.571-0.670], p < 0.05). CRI prediction of SMI was improved by considering the presence of macroproteinuria and retinopathy (AROC 0.621 [0.575-0.667] versus 0.594 [0.548-0.641], p < 0.01). Severe retinopathy (OR 3.4 [1.2-9.4], p < 0.05), smoking habits (OR 2.1 [1.1-4.2], p < 0.05) and triglyceride levels (OR 1.3 [1.0-1.6], p < 0.05) were independent predictors of CAD in the patients with SMI. CONCLUSION Current guidelines criteria are able to predict SMI but prediction may be improved by considering male gender and the presence of retinopathy. CAD is more frequent in the patients with SMI who are current smokers, have severe retinopathy and higher triglyceride levels.
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Alexiou K, Wilbring M, Nguyen MT, Tugtekin SM, Kappert U, Matschke K. Transcatheter aortic valve implantation reduces grade of concomitant mitral- and tricuspid valve regurgitation and improves right ventricular function. Thorac Cardiovasc Surg 2013. [DOI: 10.1055/s-0032-1332711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Velázquez JJ, Tikhomirov VK, Chibotaru LF, Cuong NT, Kuznetsov AS, Rodríguez VD, Nguyen MT, Moshchalkov VV. Energy level diagram and kinetics of luminescence of Ag nanoclusters dispersed in a glass host. OPTICS EXPRESS 2012; 20:13582-91. [PMID: 22714386 DOI: 10.1364/oe.20.013582] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A site-selective spectroscopy study of Ag nanoclusters dispersed in oxyfluoride glass hosts has been carried out. The nano- to millisecond, essentially non-exponential, luminescence kinetics of Ag nanoclusters has been detected in the spectral range from 450 to 1000 nm, when excited at discrete wavelengths in the range 250 to 450 nm. Based on these experimental observations, the energy level configuration coordinate diagram for the involved ground and excited singlet/triplet states of the Ag nanoclusters has been proposed and confirmed by the density functional theory (DFT). The sites for the Ag nanoclusters are argued to be multiple. The structure/geometry of the involved Ag nanoclusters has been suggested to involve spin-paired dimers Ag²⁺, or tetramers Ag₄²⁺, with a varying elongation/distortion along the tetramer diagonals.
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Appelbaum LG, Cain MS, Darling EF, Stanton SJ, Nguyen MT, Mitroff SR. Corrigendum to “What is the identity of a sports spectator?” [Personality and Individual Differences 52 (2012) 422–427]. PERSONALITY AND INDIVIDUAL DIFFERENCES 2012. [DOI: 10.1016/j.paid.2011.12.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Gregory Appelbaum L, Cain MS, Darling EF, Stanton SJ, Nguyen MT, Mitroff SR. What is the identity of a sports spectator? PERSONALITY AND INDIVIDUAL DIFFERENCES 2012. [DOI: 10.1016/j.paid.2011.10.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Claes P, Janssens E, Ngan VT, Gruene P, Lyon JT, Harding DJ, Fielicke A, Nguyen MT, Lievens P. Structural identification of caged vanadium doped silicon clusters. PHYSICAL REVIEW LETTERS 2011; 107:173401. [PMID: 22107515 DOI: 10.1103/physrevlett.107.173401] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Indexed: 05/31/2023]
Abstract
The geometry of cationic silicon clusters doped with vanadium, Si(n)V(+) (n=12-16), is investigated by using infrared multiple photon dissociation of the corresponding rare gas complexes in combination with ab initio calculations. It is shown that the clusters are endohedral cages, and evidence is provided that Si(16)V(+) is a fluxional system with a symmetric Frank-Kasper geometry.
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Cosson E, Nguyen MT, Hamo-Tchatchouang E, Banu I, Chiheb S, Charnaux N, Valensi P. What would be the outcome if the American Diabetes Association recommendations of 2010 had been followed in our practice in 1998-2006? Diabet Med 2011; 28:567-74. [PMID: 21480967 DOI: 10.1111/j.1464-5491.2010.03215.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
AIMS In 2010, the American Diabetes Association has published recommendations on the population to be screened for dysglycaemia; the diagnostic criteria for intermediate hyperglycaemia and diabetes using oral glucose tolerance testing and HbA(1c); and the patients eligible for treatment with metformin. We aimed to evaluate the consequences of screening with oral glucose tolerance test or HbA(1c) in an at-risk population. METHODS Among 1177 overweight or obese consecutive adults without known diabetes who were referred to our department for weight management, we selected 1157 individuals (83% female; 80% European) fulfilling the American Diabetes Association 2010 criteria for dysglycaemia screening. RESULTS Mean age was 41.2 ± 13 years, BMI 37.0 ± 7.2 kg/m(2), fasting plasma glucose 4.9 ± 0.8 mmol/l and HbA(1c) (turbidimetric immunoassay) 5.7 ± 0.7% (39 mmol/mol). Based on oral glucose tolerance test and HbA(1c), respectively, 76 (6.6%) and 113 (9.8%) patients had diabetes, including 34 sharing both criteria; 307 (26.5%) and 478 (41.3%) had intermediate hyperglycaemia; and 130 (11.2%) and 255 (22.0%) would be treated with metformin. The sensitivity/specificity of HbA(1c) ≥ 6.5% (48 mmol/mol) for the diagnosis of diabetes according to the oral glucose tolerance test were 44.7/92.7%. Diabetes risk scores and UK Prospective Diabetes Study cardiovascular risk score were the highest in the 130 patients having both an abnormal oral glucose tolerance test and HbA(1c) ≥ 5.7%. CONCLUSIONS In a population at risk for diabetes, the HbA(1c) strategy could lead to diagnosing more cases of dysglycaemia and to treating more patients with metformin than the oral glucose tolerance test strategy. The consistency of either diagnostic criteria was low. The patients with the highest a priori risk of diabetes and cardiovascular disease were those fulfilling both oral glucose tolerance test and HbA(1c) criteria.
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Boarnet MG, Joh K, Siembab W, Fulton W, Nguyen MT. Retrofitting the suburbs to increase walking: evidence from a land-use-travel study. URBAN STUDIES (EDINBURGH, SCOTLAND) 2011; 48:129-159. [PMID: 21174897 DOI: 10.1177/0042098010364859] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This paper reports results from a detailed travel diary survey of 2125 residents in the South Bay area of Los Angeles County - a mature, auto-oriented suburban region. Study areas were divided into four centres, typical of compact development or smart growth, and four linear, auto-oriented corridors. Results show substantial variation in the amount of walking across study areas. Trips are shorter and more likely to be via walking in centres. A key to the centres' increased walking travel is the concentration of local shopping and service destinations in a commercial core. Yet the amount of business concentration that is associated with highly pedestrian-oriented neighbourhoods is from three to four times as large as what can be supported by the local resident base, suggesting that pedestrian-oriented neighbourhoods necessarily import shopping trips, and hence driving trips, from larger surrounding catchment areas. The results suggest both land use and mobility strategies that can be appropriate for suburban regions.
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Cosson E, Nguyen MT, Pham I, Pontet M, Nitenberg A, Valensi P. N-terminal pro-B-type natriuretic peptide: an independent marker for coronary artery disease in asymptomatic diabetic patients. Diabet Med 2009; 26:872-9. [PMID: 19719707 DOI: 10.1111/j.1464-5491.2009.02788.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS To determine whether plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, a marker for cardiac failure and potentially for the severity of coronary artery disease (CAD), predicts silent myocardial ischaemia (SMI) and silent CAD in asymptomatic high-risk diabetic patients. METHODS Five hundred and seventeen asymptomatic diabetic patients with > or = 1 additional cardiovascular risk factor but without heart failure were prospectively screened between 1998 and 2008 for SMI, defined as an abnormal stress myocardial scintigraphy, and subsequently for significant (> 70%) angiographic CAD. The 323 patients with interpretable echocardiography and for whom NT-proBNP was measured were included in this analysis. RESULTS SMI was found in 108 (33.4%) patients, 39 of whom had CAD. NT-proBNP was higher in the patients with CAD than in the patients without CAD [45.0 (1-3199) vs. 20.0 (1-1640) pg/ml; P < 0.0001 median (range)], even after adjustment for confounding factors: age, gender, body mass index, glycated haemoglobin (HbA(1c)), retinopathy, nephropathy, hypertension, echocardiographic parameters (P < 0.05). NT-proBNP in the third tertile (> or = 38 pg/ml) predicted CAD with a sensitivity of 59% and a specificity of 67%. In a multiple logistic regression analysis including NT-proBNP > or = 38 pg/ml, age, body mass index, gender, HbA(1c), hypertension, retinopathy, nephropathy, peripheral occlusive arterial disease, left ventricular systolic dysfunction, dilatation and hypertrophy and Type 1 transmitral flow, NT-proBNP > or = 38 pg/ml was the only significant independent predictor of silent CAD [odds ratio (OR) 3.1 (95% confidence interval 1.3-7.6), P = 0.015]. CONCLUSIONS NT-proBNP measurement helps to better define asymptomatic diabetic patients with an increased likelihood for CAD, independently of cardiac function and structure.
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Kwok NM, Ha QP, Nguyen MT, Li J, Samali B. Bouc-Wen model parameter identification for a MR fluid damper using computationally efficient GA. ISA TRANSACTIONS 2007; 46:167-79. [PMID: 17349644 DOI: 10.1016/j.isatra.2006.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Accepted: 08/10/2006] [Indexed: 05/14/2023]
Abstract
A non-symmetrical Bouc-Wen model is proposed in this paper for magnetorheological (MR) fluid dampers. The model considers the effect of non-symmetrical hysteresis which has not been taken into account in the original Bouc-Wen model. The model parameters are identified with a Genetic Algorithm (GA) using its flexibility in identification of complex dynamics. The computational efficiency of the proposed GA is improved with the absorption of the selection stage into the crossover and mutation operations. Crossover and mutation are also made adaptive to the fitness values such that their probabilities need not be user-specified. Instead of using a sufficiently number of generations or a pre-determined fitness value, the algorithm termination criterion is formulated on the basis of a statistical hypothesis test, thus enhancing the performance of the parameter identification. Experimental test data of the damper displacement and force are used to verify the proposed approach with satisfactory parameter identification results.
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Flammang R, Srinivas R, Nguyen MT, Gerbaux P. Letter: OCCO*+, NNCO*+ and NNNN*+ radical cations. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2007; 13:173-5. [PMID: 17881784 DOI: 10.1255/ejms.844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Chemical ionization of a mixture of nitrogen and carbon monoxide produces three stable isobaric species at m/z 56: OCCO, OCNN and NNNN radical cations. Separated at increased resolution, these ions are readily identified by collisional activation. Neutralization-reionization experiments performed on two different mass spectrometers have not allowed the detection of any recovery signals for the corresponding neutrals.
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Nguyen MT, Oey I, Hendrickx M, Van Loey A. Effect of pressure and temperature combination on the stability of (6R,S) 5-methyl and (6R,S) 5-formyltetrahydrofolic acid in model system. COMMUNICATIONS IN AGRICULTURAL AND APPLIED BIOLOGICAL SCIENCES 2006; 71:291-5. [PMID: 17191524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
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Janssens E, Neukermans S, Nguyen HMT, Nguyen MT, Lievens P. Quenching of the magnetic moment of a transition metal dopant in silver clusters. PHYSICAL REVIEW LETTERS 2005; 94:113401. [PMID: 15903854 DOI: 10.1103/physrevlett.94.113401] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Indexed: 05/02/2023]
Abstract
Single magnetic atoms embedded in a nonmagnetic host exhibit the Kondo effect in the bulk limit, while in very small molecules the magnetic atom is hardly affected by the matrix. In a combined theoretical (density functional theory) and experimental (photofragmentation and mass spectrometry) study we consider the intermediate case of nanometer sized transition-metal-doped silver clusters. In particular, we provide experimental evidence for enhanced stability of the cobalt-doped silver cluster Ag10Co+ and show theoretically that it has a symmetric endohedral geometry with a closed 18-electron singlet electronic shell structure. This implies that the magnetic moment on the cobalt atom is quenched.
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Joly Y, Knoppers BM, Nguyen MT. Stored tissue samples: through the confidentiality maze. THE PHARMACOGENOMICS JOURNAL 2005; 5:2-5. [PMID: 15647759 DOI: 10.1038/sj.tpj.6500288] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Nguyen MT, Van Loey A, Hendrickx M. Isobaric-isothermal degradation kinetics of (6R,S) 5-formyltetrahydrofolic acid. COMMUNICATIONS IN AGRICULTURAL AND APPLIED BIOLOGICAL SCIENCES 2005; 70:255-8. [PMID: 16366320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
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Compernolle S, Kiran B, Chibotaru LF, Nguyen MT, Ceulemans A. Ab initio study of small graphitic cones with triangle, square, and pentagon apex. J Chem Phys 2004; 121:2326-36. [PMID: 15260787 DOI: 10.1063/1.1757440] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Accurate geometries of carbon nanocones of different sizes with a triangle, square or pentagon at the apex have been determined for the first time using a quantum chemical optimization method. The structure close to the apex is distorted from an ideal conical surface. The charging effect of the central defect is quite different from that predicted by tight-binding calculations. The symmetry behavior of the frontier orbitals and the size of the highest occupied molecular orbital-lowest unoccupied molecular orbital gap versus cone type and size is explained. The density of states quickly converges towards that of graphite when the size of the cone increases. In comparison to previous results in the literature it is found that the local densities of states of cones, that are locally different but belong to the same topo-combinatoric class, share common features.
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Arroqui C, Messagie I, Nguyen MT, Van Loey A, Hendrickx M. Comparative study on pressure and temperature stability of 5-methyltetrahydrofolic acid in model systems and in food products. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2004; 52:485-492. [PMID: 14759137 DOI: 10.1021/jf0349432] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A comparative study on the pressure and temperature stability of 5-methyltetrahydrofolic acid (5-CH(3)-H(4)folate) was performed in model/buffer systems and food products (i.e., orange juice, kiwi puree, carrot juice, and asparagus). Effects of pH and ascorbic acid (0.5 mg/g) on 5-CH(3)-H(4)folate stability in buffer systems were studied on a kinetic basis at different temperatures (from 65 to 160 degrees C) and different pressure/temperature combinations (from 100 to 700 MPa/from 20 to 65 degrees C). These studies showed that (i) the degradation of 5-CH(3)-H(4)folate in all model systems could be described by first-order reaction kinetics, (ii) the thermostability of 5-CH(3)-H(4)folate was enhanced by increasing pH up to 7, (iii) 5-CH(3)-H(4)folate was relatively pressure stable at temperatures lower than 40 degrees C, and (iv) ascorbic acid enhanced both the thermo- and barostabilities of 5-CH(3)-H(4)folate. In food products, temperature and pressure stabilities of 5-CH(3)-H(4)folate were studied at different temperatures (70-120 degrees C) and different pressure/temperature combinations (from 50 to 200 MPa/25 degrees C and 500 MPa/60 degrees C). 5-CH(3)-H(4)folate in orange juice and kiwi puree was relatively temperature (up to 120 degrees C) and pressure (up to 500 MPa/60 degrees C) stable in contrast to carrot juice and asparagus. Addition of ascorbic acid (0.5 mg/g) in carrot juice resulted in a remarkable protective effect on pressure (500 MPa/60 degrees C/40 min) and temperature degradation (120 degrees C/40 min) of 5-CH(3)-H(4)folate.
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Nguyen MT, Van Loey A, Hendrickx M. Effect of pH on temperature stability of folates. COMMUNICATIONS IN AGRICULTURAL AND APPLIED BIOLOGICAL SCIENCES 2004; 69:203-6. [PMID: 15560222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
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Barbieri M, Allman J, Pham BS, Nguyen MT. Demographic trends in Vietnam. POPULATION. ENGLISH SELECTION 2002; 8:209-34. [PMID: 12157937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
"Asia's four ¿little dragons' (South Korea, Hong Kong, Singapore and Taiwan) have in common not only an economic boom, but also the same rapid demographic transition. How does Vietnam, whose economy is poised for a take-off, stand in this respect? In an attempt to answer this question, [the authors] study the growing corpus of information which a number of ad hoc surveys have added to the 1979 and 1989 population censuses."
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Nguyen MT, Greenberg SB, Fitzhugh KR, Glasier CM. Pediatric imaging: sedation with an injection formulation modified for rectal administration. Radiology 2001; 221:760-2. [PMID: 11719673 DOI: 10.1148/radiol.2213010236] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine if rectal sedation with thiopental sodium produced for intravenous administration provides safe and effective sedation for children undergoing diagnostic imaging. MATERIALS AND METHODS Five hundred twenty-five consecutive children (mean age, 2.7 years +/- 2.2 [SD]) underwent magnetic resonance imaging (n = 425), computed tomography (n = 89), and nuclear medicine (n = 11) examinations after rectal administration of thiopental sodium injection solution. The solution was prepared from thiopental sodium powder mixed with sterile water to create a concentration of 100 mg/mL. The dose ranged from 25 to 40 mg per kilogram of body weight, with a total dose limit of 1.5 g. The percentages of successful sedations and adverse reactions were evaluated on the basis of data collected at the time of the sedation. RESULTS Sedation was successful in 504 (96%) children. Ten (2%) children experienced desaturation, but only three of the 10 experienced sedation failure. All cases of desaturation were treated successfully with head repositioning, administration of supplemental oxygen, or both. No children experienced vomiting, acute rectal irritation, paradoxical hyperactivity, or prolonged sedation. CONCLUSION Thiopental sodium sedation for pediatric imaging, with use of a rectal solution prepared from thiopental sodium preparation for intravenous injection, is safe and effective.
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