Comparative Study of Power Semiconductor Devices in a Multilevel Cascaded H-Bridge Inverter

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET and IGBT modeling tools in Saber® were extensively utilized to create the models of the power devices used in the simulations. The inverter system is also analyzed using Saber-Simulink cosimulation method to feed control signals from Simulink into Saber. The results in this investigation show better performances using a SiC MOSFET-based grid-connected BESS inverter with a better return of investment

Static aspects of accommodation: age and presbyopia

AbstractAlthough the progressive reduction in accommodative amplitude with increased age is well documented, little is known about several other aspects of static or steady-state accommodation to provide a comprehensive assessment of changes related to age and presbyopia. Static components of accommodation (tonic accommodation, depth-of-focus, slope of the stimulus/response function, and accommodative controller gain) were assessed objectively using an infrared (IR) optometer in 30 human subjects aged 21–50 years; depth-of-focus was also determined psychophysically as was accommodative amplitude. Tonic accommodation and the amplitude of accommodation decreased with increased age, whereas the subjective depth-of-focus increased; the other parameters remained unchanged. The decrease in tonic accommodation and amplitude of accommodation was attributed to biomechanical factors, whereas the increase in subjective depth-of-focus was believed to result from increased tolerance to defocus related to the gradual onset of presbyopia. Constancy of the objective depth-of-focus suggested absence of age effects on the neurologic control of reflex accommodation, whereas the lack of systematic change in slope and controller gain provided support for the Hess–Gullstrand theory of accommodation and presbyopia

Conformational properties of monosubstituted cyclohexane guest molecules constrained within zeolitic host materials. A solid-state NMR investigation

The conformational properties of monosubstituted cyclohexane guest molecules (C6H11X with X = CH3, OH, Cl, Br and I) included within microporous solid host materials (silicalite-I, H-ZSM-5, NH4-mordenite and zeolite NH4-Y) have been elucidated via high-resolution solid-state 13C NMR spectroscopy. For all of the inclusion compounds investigated, the fraction of monosubstituted cyclohexane molecules in the equatorial conformation is similar to that in solution, suggesting that these host materials do not impose any significant constraints upon the conformational properties of the monosubstituted cyclohexane guest molecules. For the monohalogenocyclohexane guest molecules (C6H11X with X = Cl, Br and I), this result is in marked contrast to the situation for the same guest molecules in the thiourea host structure, for which the conformational properties of the guest molecules are substantially different from those of the same molecules in solution. For cyclohexanol (C6H11OH) in H-ZSM-5, some amount of dicyclohexyl ether (C6H11OC6H11) is observed, and is analogous to the proposed production of dimethyl ether in the first stage of methanol-to-gasoline conversion on this zeolite. The comparatively low temperature (ambient temperature) at which this conversion from cyclohexanol to dicyclohexyl ether occurs is noteworthy. In addition to our high-resolution solid-state 13C NMR studies of these materials, 1H MAS and 27AI MAS NMR spectra have also been recorded, and are discussed

GC-MS Analysis of β-Carotene Ethenolysis Products and their Synthesis as Potentially Active Vitamin A Analogues

β-Carotene ethenolysis under promotion of well-defined ruthenium catalysts were examined as a novel method of synthesis of vitamin A derivatives. Efficient reaction was promoted by the second-generation Hoveyda catalyst. The products of ethenolysis in positions C15-C15′, C11-C12, and C9-C10 were detected, but cleavage of the C11-C12 double bond predominated. Even better regioselectivity at this position was observed for cross—metathesis between β-carotene and functionalized alkenes

Coronary CT Angiography and 5-Year Risk of Myocardial Infarction.

BACKGROUND: Although coronary computed tomographic angiography (CTA) improves diagnostic certainty in the assessment of patients with stable chest pain, its effect on 5-year clinical outcomes is unknown. METHODS: In an open-label, multicenter, parallel-group trial, we randomly assigned 4146 patients with stable chest pain who had been referred to a cardiology clinic for evaluation to standard care plus CTA (2073 patients) or to standard care alone (2073 patients). Investigations, treatments, and clinical outcomes were assessed over 3 to 7 years of follow-up. The primary end point was death from coronary heart disease or nonfatal myocardial infarction at 5 years. RESULTS: The median duration of follow-up was 4.8 years, which yielded 20,254 patient-years of follow-up. The 5-year rate of the primary end point was lower in the CTA group than in the standard-care group (2.3% [48 patients] vs. 3.9% [81 patients]; hazard ratio, 0.59; 95% confidence interval [CI], 0.41 to 0.84; P=0.004). Although the rates of invasive coronary angiography and coronary revascularization were higher in the CTA group than in the standard-care group in the first few months of follow-up, overall rates were similar at 5 years: invasive coronary angiography was performed in 491 patients in the CTA group and in 502 patients in the standard-care group (hazard ratio, 1.00; 95% CI, 0.88 to 1.13), and coronary revascularization was performed in 279 patients in the CTA group and in 267 in the standard-care group (hazard ratio, 1.07; 95% CI, 0.91 to 1.27). However, more preventive therapies were initiated in patients in the CTA group (odds ratio, 1.40; 95% CI, 1.19 to 1.65), as were more antianginal therapies (odds ratio, 1.27; 95% CI, 1.05 to 1.54). There were no significant between-group differences in the rates of cardiovascular or noncardiovascular deaths or deaths from any cause. CONCLUSIONS: In this trial, the use of CTA in addition to standard care in patients with stable chest pain resulted in a significantly lower rate of death from coronary heart disease or nonfatal myocardial infarction at 5 years than standard care alone, without resulting in a significantly higher rate of coronary angiography or coronary revascularization. (Funded by the Scottish Government Chief Scientist Office and others; SCOT-HEART ClinicalTrials.gov number, NCT01149590 .)

Hypertension, Microvascular Pathology, and Prognosis After an Acute Myocardial Infarction

The rationale for our study was to investigate the pathophysiology of microvascular injury in patients with acute ST-segment–elevation myocardial infarction in relation to a history of hypertension. We undertook a cohort study using invasive and noninvasive measures of microvascular injury, cardiac magnetic resonance imaging at 2 days and 6 months, and assessed health outcomes in the longer term (URL: http://www.clinicaltrials.gov. Unique identifier: NCT02072850). Three hundred twenty-four patients with acute myocardial infarction (mean age, 59 [12] years; blood pressure, 135 [25] / 79 [14] mm Hg; 237 [73%] male, 105 [32%] with antecedent hypertension) were prospectively enrolled during emergency percutaneous coronary intervention. Compared with patients without antecedent hypertension, patients with hypertension were older (63 [12] years versus 57 [11] years; P<0.001) and a lower proportion were cigarette smokers (52 [50%] versus 144 [66%]; P=0.007). Coronary blood flow, microvascular resistance within the culprit artery, infarct pathologies, inflammation (C-reactive protein and interleukin-6) were not associated with hypertension. Compared with patients without antecedent hypertension, patients with hypertension had less improvement in left ventricular ejection fraction at 6 months from baseline (5.3 [8.2]% versus 7.4 [7.6]%; P=0.040). Antecedent hypertension was a multivariable associate of incident myocardial hemorrhage 2-day post-MI (1.81 [0.98–3.34]; P=0.059) and all-cause death or heart failure (n=47 events, n=24 with hypertension; 2.53 [1.28–4.98]; P=0.007) postdischarge (median follow-up 4 years). Severe progressive microvascular injury is implicated in the pathophysiology and prognosis of patients with a history of hypertension and acute myocardial infarction

Comparing biomarker profiles of patients with heart failure:atrial fibrillation vs. sinus rhythm and reduced vs. preserved ejection fraction

Aims: The clinical correlates and consequences of atrial fibrillation (AF) might be different between heart failure with reduced vs. preserved ejection fraction (HFrEF vs. HFpEF). Biomarkers may provide insights into underlying pathophysiological mechanisms of AF in these different heart failure (HF) phenotypes. Methods and results: We performed a retrospective analysis of the BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF), which was an observational cohort. We studied 2152 patients with HFrEF [ejection fraction (EF < 40%)], of which 1419 were in sinus rhythm (SR) and 733 had AF. Another 524 patients with HFpEF (EF ≥50%) were studied, of which 286 in SR and 238 with AF. For the comparison of biomarker profiles, 92 cardiovascular risk markers were measured (Proseek® Olink Cardiovascular III panel). The circulating risk marker pattern observed in HFrEF was different than the pattern in HFpEF: in HFrEF, AF was associated with higher levels of 77 of 92 (84%) risk markers compared to SR; whereas in HFpEF, many more markers were higher in SR than in AF. Over a median follow-up of 21 months, AF was associated with increased mortality risk [multivariable hazard ratio (HR) of 1.27; 95% confidence interval (CI) 1.09–1.48, P = 0.002]; there was no significant interaction between heart rhythm and EF group on outcome. Conclusion: In patients with HFrEF, the presence of AF was associated with a homogeneously elevated cardiovascular risk marker profile. In contrast, in patients with HFpEF, the presence of AF was associated with a more scattered risk marker profile, suggesting differences in underlying pathophysiological mechanisms of AF in these HF phenotypes

Is Acute heart failure a distinctive disorder? An analysis from BIOSTAT-CHF

AimsThis retrospective analysis sought to identify markers that might distinguish between acute heart failure (HF) and worsening HF in chronic outpatients.Methods and ResultsThe BIOSTAT‐CHF index cohort included 2516 patients with new or worsening HF symptoms: 1694 enrolled as inpatients (acute HF) and 822 as outpatients (worsening HF in chronic outpatients). A validation cohort included 935 inpatients and 803 outpatients. Multivariable models were developed in the index cohort using clinical characteristics, routine laboratory values, and proteomics data to examine which factors predict adverse outcomes in both conditions and to determine which factors differ between acute HF and worsening HF in chronic outpatients, validated in the validation cohort.Patients with acute HF had substantially higher morbidity and mortality (6 months mortality was 12..3% for acute HF and 4..7% for worsening HF in chronic outpatients). Multivariable models predicting 180‐day mortality and 180‐day HF re‐admission differed substantially between acute HF and worsening HF in chronic outpatients. CA‐125 was the strongest single biomarker to distinguish acute HF from worsening HF in chronic outpatients, but only yielded a C‐index of 0..71. A model including multiple biomarkers and clinical variables achieved a high degree of discrimination with a C‐index of 0..913 in the index cohort and 0..901 in the validation cohort.ConclusionThe study identifies different characteristics and predictors of outcome in acute HF patients as compared to outpatients with chronic HF developing worsening HF. The markers identified may be useful in better diagnosing acute HF and may become targets for treatment development.</h4

Heart failure treatment up-titration and outcome and age: an analysis of BIOSTAT-CHF

Aims: Several studies have shown that older patients with heart failure with reduced ejection fraction (HFrEF) are undertreated. The aim of this study was to evaluate the association of up‐titration of angiotensin‐converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB) and beta‐blockers on outcome across the age spectrum in HFrEF patients. Methods and results: We analysed HFrEF patients on sub‐optimal doses of ACEI/ARB and/or beta‐blockers from the BIOSTAT‐CHF study stratified by age. Patients underwent a 3‐month up‐titration period. We used inverse probability weighting to adjust for the likelihood of successful up‐titration to determine the association of achieved dose with mortality and/or heart failure hospitalisation, testing for an interaction with age. Over a median follow‐up of 21 months in 1720 HFrEF patients (76.5% male, mean age 67 years), the primary outcome occurred in 558 patients. Increased percentage of target dose of ACEI/ARB and beta‐blocker achieved at 3 months were both significantly associated with reduced incidence of the primary outcome, [ACEI‐ARB: hazard ratio (HR) per 12.5% increase in dose: 0.92, 95% confidence interval (CI) 0.91–0.94, P &lt; 0.001; beta‐blocker: HR 0.98, 95% CI 0.95–1.00, P = 0.046], with a significant interaction with age seen for beta‐blockers but not ACEI/ARB (P = 0.034 and P = 0.22, respectively). Conclusions: Achieving higher doses of ACEI/ARB was associated with improved outcome regardless of age. However, achieving higher doses of beta‐blockers was only associated with improved outcome in younger, but not in older patients

Current Smoking and Prognosis After Acute ST-Segment Elevation Myocardial Infarction:New Pathophysiological Insights

Objectives: The aim of this study was to mechanistically investigate associations among cigarette smoking, microvascular pathology, and longer term health outcomes in patients with acute ST-segment elevation myocardial infarction (MI). Background: The pathophysiology of myocardial reperfusion injury and prognosis in smokers with acute ST-segment elevation MI is incompletely understood. Methods: Patients were prospectively enrolled during emergency percutaneous coronary intervention. Microvascular function in the culprit artery was measured invasively. Contrast-enhanced magnetic resonance imaging (1.5-T) was performed 2 days and 6 months post-MI. Infarct size and microvascular obstruction were assessed using late gadolinium enhancement imaging. Myocardial hemorrhage was assessed with T2* mapping. Pre-specified endpoints included: 1) all-cause death or first heart failure hospitalization; and 2) cardiac death, nonfatal MI, or urgent coronary revascularization (major adverse cardiovascular events). Binary logistic regression (odds ratio [OR] with 95% confidence interval [CI]) with smoking status was used. Results: In total, 324 patients with ST-segment elevation MI were enrolled (mean age 59 years, 73% men, 60% current smokers). Current smokers were younger (55 ± 11 years vs. 65 ± 10 years, p &lt; 0.001), with fewer patients with hypertension (52 ± 27% vs. 53 ± 41%, p = 0.007). Smokers had better TIMI (Thrombolysis In Myocardial Infarction) flow grade (≥2 vs. ≤1, p = 0.024) and ST-segment resolution (none vs. partial vs. complete, p = 0.010) post–percutaneous coronary intervention. On day 1, smokers had higher circulating C-reactive protein, neutrophil, and monocyte levels. Two days post-MI, smoking independently predicted infarct zone hemorrhage (OR: 2.76; 95% CI: 1.42 to 5.37; p = 0.003). After a median follow-up period of 4 years, smoking independently predicted all-cause death or heart failure events (OR: 2.20; 95% CI: 1.07 to 4.54) and major adverse cardiovascular events (OR: 2.79; 95% CI: 2.30 to 5.99). Conclusions: Smoking is associated with enhanced inflammation acutely, infarct-zone hemorrhage subsequently, and longer term adverse cardiac outcomes. Inflammation and irreversible myocardial hemorrhage post-MI represent mechanistic drivers for adverse long-term prognosis in smokers. (Detection and Significance of Heart Injury in ST Elevation Myocardial Infarction. [BHF MR-MI]; NCT02072850)