Study of Self-Heating and High-Power Microwave Effects for Enhancement-Mode p-Gate GaN HEMT

The self-heating and high-power microwave (HPM) effects that can cause device heating are serious reliability issues for gallium nitride (GaN) high-electron-mobility transistors (HEMT), but the specific mechanisms are disparate. The different impacts of the two effects on enhancement-mode p-gate AlGaN/GaN HEMT are first investigated in this paper by simulation and experimental verification. The simulation models are calibrated with previously reported work in electrical characteristics. By simulation, the distributions of lattice temperature, energy band, current density, electric field strength, and carrier mobility within the device are plotted to facilitate understanding of the two distinguishing mechanisms. The results show that the upward trend in temperature, the distribution of hot spots, and the thermal mechanism are the main distinctions. The effect of HPM leads to breakdown and unrecoverable thermal damage in the source and drain areas below the gate, while self-heating can only cause heat accumulation in the drain area. This is an important reference for future research on HEMT damage location prediction technology and reliability enhancement

The beneficial effects of renin–angiotensin system blockades on 2 year outcomes in coronary artery ectasia patients

<p><b>Objectives:</b> This study was designed to investigate the impact of renin–angiotensin system blockade (RASB) therapy with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers on the outcomes of coronary artery ectasia (CAE).</p> <p><b>Methods:</b> The CAE patients identified by coronary angiography from our center were consecutively enrolled. We obtained the baseline discharge prescription of RASB from the medical records system and conducted follow-up through telephone interviews. Cox regression models, propensity score and subgroup analysis were used to assess the impact of RASB on all-cause mortality and non-fatal myocardial infarction. Both the unadjusted and adjusted Kaplan–Meier curves stratified by RASB therapy were plotted.</p> <p><b>Results:</b> There were 595 patients with CAE in total and 333 (56.0%) were prescribed RASB therapy. Over a 2 year follow-up time, 16 all-cause deaths and 10 non-fatal myocardial infarctions were identified. Those patients treated with RASB had a significantly lower all-cause mortality and non-fatal myocardial infarction rate with an adjusted hazard ratio of 0.32 (95% confidence interval: 0.13 to 0.77, <i>p</i> = .011). The outcome benefits of RASB therapy were further confirmed in the propensity score analysis and subgroup analysis.</p> <p><b>Conclusions:</b> This observational study suggests that RASB therapy is associated with a lower risk of all-cause mortality and non-fatal myocardial infarction in patients with CAE.</p