thanh tung phan - Academia.edu (original) (raw)

Papers by thanh tung phan

International Journal of Stroke, 2012

Cerebral small vessel disease is difficult to directly visualize in vivo. Therefore, we rely on r... more Cerebral small vessel disease is difficult to directly visualize in vivo. Therefore, we rely on radiological phenotypes as surrogate markers of disease. The principal phenotypes of clinical interest are small, deep brain infarcts, cerebral white matter lesions, deep brain haemorrhages, and cerebral microbleeds. The causes or mechanisms underlying these phenotypes are understood in varying degrees of detail. This review aims to summarize recent knowledge regarding these phenotypes and place it in context with classical clinicopathological observations to provide mechanistic, clinical, and therapeutic insights into small vessel disease.

Abstracts of the International Stroke Conference, 2000

International Journal of Cardiology, 2006

Ventricular tachycardia (VT) can be a life threatening condition which can be caused by an underl... more Ventricular tachycardia (VT) can be a life threatening condition which can be caused by an underlying electrolyte disturbance, such as hypomagnesaemia. Causes of electrolyte disturbances, such as magnesium losing nephropathy, should be identified early to allow correct management of the underlying cause of the cardiac arrhythmia.

The Journal of Physical Chemistry C, 2014

ABSTRACT A combination of cyclic voltammetry, in situ electrochemical scanning tunneling microsco... more ABSTRACT A combination of cyclic voltammetry, in situ electrochemical scanning tunneling microscopy (EC-STM), and ex situ X-ray photoelectron spectroscopy (XPS) studies was employed to investigate the electrochemical behavior and to characterize the structure of adsorbed layers of a redox-active pyridine-appended zinc phthalocyanine (ZnPc) at Cu(100)/electrolyte interfaces. Additional cyclic voltammograms (CVs) of a HOPG electrode in phthalocyanine- and iodide-containing electrolyte showed four redox peak pairs related to the phthalocyanine macrocycle. Focusing on the reduction processes, the four observed cathodic waves were assigned to four single electron transfer steps causing four successive reductions of the phthalocyanine. Due to its narrow potential window, the CV of Cu(100) in the same electrolyte covers only the first three reduction features in the acidic solution superimposed by the CuI formation/dissolution processes. Surprisingly, the XPS data from the iodide and phthalocyanine covered Cu(100) surface, however, revealed a demetalation of the molecules, that is, a replacement of the central zinc atom of adsorbed ZnPc+ by hydrogen atoms resulting in the formation of the corresponding free base phthalocyanine H2Pc+. These H2Pc+ molecules form highly ordered adlayers on the iodide-modified Cu(100) surface with the coexistence of different phases, that is, one with a square-shaped unit cell enclosing an angle of (91 ± 2)° and a rhombic one with an angle of (66 ± 2)°, and intermolecular distances of 2.0 ± 0.1 nm and 2.3 ± 0.1 nm, respectively. The main symmetry axes of the H2Pc+ adlayer run parallel neither to the commensurate direction of the iodide layer underneath nor to the close-packed atomic rows of the copper substrate. Detailed molecular models are proposed which are in agreement with the patterns experimentally observed with EC-STM.

Abstracts of the International Stroke Conference, 2000

Computer Communications, 2012

a b s t r a c t WLAN (Wireless Local Area Network) has been seen to be one of the promising acces... more a b s t r a c t WLAN (Wireless Local Area Network) has been seen to be one of the promising access technologies that adapts to 4G cellular network systems in providing very high speed connection with QoS guarantee through the polling function. However, when the handover happens, the contention-based medium access mechanism which is mainly used in WLAN is invoked and introduces unbounded transmission delay due to idle time periods and retransmission because of collision during the handover. If this technique is expanded to use in a microcellular network such as connected WLAN micro-cells, contention-based mechanism, therefore, should not be used to handle the MT's handover, especially for vehicular users who change access point every few seconds. To overcome these difficulties in handover, we introduce parallel polling scheme in dynamic LMC (Logical Macro Cell) which can reduce delays much and remove packet loss rate. LMC is a virtual single macro cell which is built on a multicast group of adjacent micro-cells. In the same LMC, polling signals are sent from every BS (base station) to give MT (mobile terminal) permission to access one of these BSs. Instead of wasting much time to contend for resources of a new BS during handover, the MT answers the polling as an acknowledgment to connect to that new BS. The polling response is controlled to multicast to all BSs of the same LMC via the core network to synchronize for the next polling cycle. LMC is controlled to dynamically change when the MT comes in a new BS to make polling signals be continuous in a new LMC. Through analytical and simulation results, we show that the parallel polling scheme can achieve no handover latency, no packet loss and maintain mobile users' throughput stably in the high traffic load condition though it causes overhead on the neighboring cells in both of wired and wireless sections. At speeds of up to70 m/s, the MT can still maintain its stable connection. OMNeT++ simulator with INET project is used to evaluate our proposal.

Journal of Integral Equations and Applications, 2014

ABSTRACT

For the solution of elliptic Dirichlet boundary control problems, we propose and analyze two boun... more For the solution of elliptic Dirichlet boundary control problems, we propose and analyze two boundary element approaches. The state equation, the adjoint equation, and the optimality condition are rewritten as systems of boundary integral equations involving the standard boundary integral operators of the Laplace equation and of the Bi-Laplace equation. While the first approach is based on the use of the weakly singular Bi-Laplace boundary integral equation, the additional use of the hypersingular Bi-Laplace boundary integral equation results in a symmetric formulation, which is also symmetric in the discrete case. We prove the unique solvability of both boundary integral approaches and discuss related boundary element discretizations. In particular, we prove stability and related error estimates which are confirmed by a numerical example.

Archives of Pharmacal Research, 2010

An analytical micellar electrokinetic chromatographic method was developed and validated for the ... more An analytical micellar electrokinetic chromatographic method was developed and validated for the determination of the L-enantiomer of nateglinide. Separations were carried out in a 50 μm, 64.5/56 fused-silica capillary. The optimized conditions included 75 mM borate buffer, pH 9.2, containing 50 mM of sodium dodecyl sulfate and 25 mg/mL of methyl-β-cyclodextrin as background electrolyte, an applied voltage of 20 kV and a temperature of 15, UV detector at 210 nm. The assay was validated for the L-enantiomer of nateglinide. The limit of detection and quantification were 0.07 and 0.2% respectively. Intraday precision was ranged between 0.12 and 1.7%. Interday precision ranged between 0.73 and 1.73%. The assay was applied to the determination of the L-enantiomer of nateglinide in pharmaceutical formulations.

European Journal of Heart Failure Supplements, 2008

Aim: We used Near Infrared Spectrophotometry (NIRS) during arterial occlusion to measure resting ... more Aim: We used Near Infrared Spectrophotometry (NIRS) during arterial occlusion to measure resting skeletal muscle oxygen consumption in chronic heart failure (CHF) patients and in age-matched healthy volunteers (HVs). Methods: Fifteen CHF patients (ten males) and eleven HVs (six males) had echocardiographic evaluation followed by measurement of the oxygen consumption of the brachioradialis muscle using NIRS. This involved continuous measurement of the oxygenated haemoglobin concentration ([Oxy-Hb]) and deoxy-haemoglobin concentration ([Deoxy-Hb]) with an Oxiplex TS NIRS probe first under basal overnight fasted resting conditions followed by 1 min of forearm arterial occlusion. A linear decline was observed in [Oxy-Hb-Deoxy-Hb] during the arterial occlusion and the oxygen consumption rate was calculated from the initial slope observed. Results: CHF patients were 59 ± 2.8 years old with Left Ventricular Ejection Fraction (LVEF) 31% ± 2.2 and the HVs were 52 ± 4.8 years old with LVEF 62% ± 2.5. The resting muscle oxygen consumption rate was significantly reduced in CHF patients versus HVs (0.04 ± 0.01 mlO 2 /min/100 g versus 0.07 ± 0.01 mlO 2 /min/100 g) p b 0.005. Conclusions: There is a significant reduction in resting oxygen consumption per gram of tissue in skeletal muscle of patients with CHF.

Journal of the American College of Cardiology

We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation an... more We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation and of LV contractile function and vasculoventricular coupling (VVC) in the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and to assess myocardial energetic status in these patients. To date, no studies have investigated exercise-related changes in LV relaxation and VVC as well as in vivo myocardial energetic status in patients with HFpEF. We studied 37 patients with HFpEF and 20 control subjects. The VVC and time to peak LV filling (nTTPF, a measure of LV active relaxation) were assessed while patients were at rest and during exercise by the use of radionuclide ventriculography. Cardiac energetic status (creatine phosphate/adenosine triphosphate ratio) was assessed by the use of (31)P magnetic resonance spectroscopy at 3-T. When patients were at rest, nTTPF and VVC were similar in patients with HFpEF and control subjects. The cardiac creatine phosphate/adenosin...

$Research paper thumbnail of Left ventricular torsion and strain patterns in heart failure with normal ejection fraction are similar to age-related changes$

European Journal of Echocardiography, 2009

Aims We used speckle tracking echocardiography (STE) to make a comparison between the effects of ... more Aims We used speckle tracking echocardiography (STE) to make a comparison between the effects of ageing and of heart failure with normal ejection fraction (HfnEF) on left ventricular (LV) torsion and strain patterns. Methods and results Forty patients with HfnEF, 27 young controls and 26 older controls, were prospectively recruited. All subjects underwent clinical examination, 12-lead electrocardiogram, pulmonary function test, echocardiogram, and metabolic exercise test. LV torsion increases with advancing age (older controls vs. young controls, 2.2 + 0.9 vs. 1.4 + 0.88/cm; P ¼ 0.03). Circumferential strain was enhanced in patients with HfnEF (224.7 + 4.7 vs. 220.0 + 4.9%; P ¼ 0.003). Rotational deformation delay (time difference between peak basal rotation and peak apical rotation), global circumferential strain, E-velocity deceleration time, and LV end-diastolic volume index were independent predictors of LV torsion. LV torsion and body mass index were independent predictors of LV untwist rate. Conclusion Ageing is associated with increased LV torsion secondary to reduced rotational deformation delay and increased peak basal rotation. LV torsion and strain patterns in patients with HfnEF are similar to age-related changes apart from circumferential strain, which is enhanced in patients with HfnEF.

Circulation: Heart Failure, 2009

Background-This study assessed the chronotropic response to exercise and heart rate (HR) recovery... more Background-This study assessed the chronotropic response to exercise and heart rate (HR) recovery after exercise in a carefully phenotyped group of patients with heart failure with preserved left ventricular ejection fraction (HfpEF) and a control group of similar age and gender distribution. Methods and Results-We studied 41 patients with HfpEF, 41 healthy controls, and 16 hypertensive controls. None were taking HR-limiting medications. All study participants had clinical examination, 12-lead ECG, pulmonary function test, echocardiogram, and metabolic exercise test with HR monitoring throughout exercise. Chronotropic response was measured by the percentage of the HR reserve used during maximal exercise and the peak exercise HR as a percentage of predicted maximal HR. Patients with HfpEF were generally women (70%), overweight, aged 69Ϯ8 years. Controls were of similar gender (63%) and age (67Ϯ6 years). Patients with HfpEF had significantly reduced peak VO 2 compared with controls (20Ϯ4 mL ⅐ kg Ϫ1 ⅐ min Ϫ1 versus 31Ϯ6 mL ⅐ kg Ϫ1 ⅐ min Ϫ1 , PϽ0.001) and greater minute ventilationcarbon dioxide production relationship (VE/VCO 2 slope) (33Ϯ6 versus 29Ϯ4, PϽ0.001). Chronotropic incompetence was significantly more common in patients with HfpEF compared with matched healthy controls as measured by the percentage of the HR reserve used during maximal exercise (63% versus 2%, Ͻ0.001) and percentage of predicted maximal HR (34% versus 2%, Ͻ0.001). In addition, abnormal HR recovery 1-minute after exercise (defined as the reduction in the HR from peak exercise 1-minute after exercise) was also significantly more common in patients with HfpEF compared with controls (23% versus 2%, Pϭ0.01). Hypertensive controls showed similar chronotropic response to peak exercise and HR recovery after exercise as healthy controls.

$Research paper thumbnail of Diastolic filling abnormalities during exercise in patients with Heart Failure with a Preserved Ejection Ffraction (HFPEF) as measured by radionuclide ventriculography$

European Journal of Heart Failure Supplements, 2008

Results: 42 out of 195 patients (21.6%) were anemic (hemoglobin concentration <13 g/dl (males), <... more Results: 42 out of 195 patients (21.6%) were anemic (hemoglobin concentration <13 g/dl (males), <12 g/dl (females)). Anemic patients belonged to NYHA functional class III-IV in significantly higher proportion (71%), than non-anemic patients (48%). In anemic patients significantly lower levels of iron and transferrin saturation (p<0.0001), and significantly higher levels of soluble transferrin receptor, creatinin, erythropoietin (EPO), C-reactive protein, soluble TNF receptor I and II were found (p<0.05), than in non-anemic patients. Iron deficiency, inflammation and impaired renal function (or the combination of these) were found in the background of the anemia in 80% of patients. The role of relative EPO deficiency or hemodilution was not significant. Conclusions: According to our results, anemia in CHF can be classified with simple tests. A reasonable protocol will be presented for this purpose. Therapy based on the causes of anemia may lead to a better quality of life and may decrease patients' mortality.

Metabolism, 2011

Left ventricular torsion is increased and cardiac energetics are reduced in uncomplicated type 1 ... more Left ventricular torsion is increased and cardiac energetics are reduced in uncomplicated type 1 diabetes mellitus (T1DM). Our aim was to determine the relationships of these abnormalities to cardiovascular autonomic neuropathy (CAN) in subjects with T1DM. A cross-sectional study was conducted in 20 subjects with T1DM free of known coronary heart disease attending an outpatient clinic. Cardiovascular autonomic neuropathy was assessed using heart rate variability studies and the continuous wavelet transform method. Left ventricular function was determined by speckle tracking echocardiography. Magnetic resonance spectroscopy and stress magnetic resonance imaging were used to measure cardiac energetics and myocardial perfusion reserve index, respectively. Twenty subjects (age, 35 ± 8 years; diabetes duration, 16 ± 9 years; hemoglobin A 1c , 8.0% ± 1.1%) were recruited. Forty percent of the subjects exhibited definite or borderline CAN. Log peak radial strain was significantly increased in subjects with CAN compared with those without (1.56 ± 0.06 vs 1.43 ± 0.14, respectively; P = .011). Data were adjusted for log duration of diabetes, and log left ventricular torsion correlated (r = 0.593, P = .01) with log low-frequency to high-frequency ratio during the Valsalva maneuver. Log isovolumic relaxation time correlated significantly with log Valsalva ratio and log proportion of differences in consecutive RR intervals of normal beats greater than 50 milliseconds during deep breathing. However, CAN did not correlate with cardiac energetics or myocardial perfusion reserve index. Spectral analysis of low- Â© 2011 Elsevier Inc. frequency to high-frequency ratio power during the Valsalva maneuver is associated with altered left ventricular torsion in subjects with T1DM. Parasympathetic dysfunction is closely associated with diastolic deficits. Cardiovascular autonomic neuropathy is not however the principal cause of impaired cardiac energetics. The role of CAN in the development of cardiomyopathy warrants further evaluation.