The AlGaN-based deep ultraviolet light-emitting diodes (LED) with double electron blocking layers (d-EBLs) on both sides of the active region are investigated theoretically. They possess many excellent performances compared with the conventional structure with only a single electron blocking layer, such as a higher recombination rate, improved light output power and internal quantum efficiency (IQE). The reasons can be concluded as follows. On the one hand, the weakened electrostatic field within the quantum wells (QWs) enhances the electron–hole spatial overlap in QWs, and therefore increases the probability of radioactive recombination. On the other hand, the added n-AlGaN layer can not only prevent holes from overflowing into the n-side region but also act as another electron source, providing more electrons.
IntroductionIliopsoas abscess with septicemia in the pediatric population is rare. Early diagnosis and effective management of this emergent disorder remain challenging for clinicians.Case PresentationA 14-year-old girl presented with right lateral and posterior hip pain and fever for 7 days before admission. Blood culture was positive for Staphylococcus aureus. Enhanced magnetic resonance imaging revealed abscesses located in the right iliopsoas muscle and on the surface deep to the fascia of the right sacroiliac joint that were 6.8 cm × 6.2 cm × 5.7 cm and 3.7 cm × 3.5 cm × 2.1 cm, respectively. A diagnosis of right iliopsoas abscesses with septicemia was made. The patient received intravenous antibiotics, underwent ultrasound-guided percutaneous catheter drainage, and recovered uneventfully. Medical literature regarding this issue published in the English language during the last two decades was reviewed.DiscussionPrimary synchronous psoas and iliacus muscle abscesses are rare and emergent disorders in the pediatric age group. The diagnosis is generally delayed owing to the deep anatomic location and nonspecific signs and symptoms. A comprehensive medical history, meticulous physical examination, and judicious use of imaging studies could establish a timely and accurate diagnosis. Surgeons should be aware of the occurrence of multiple abscesses. Prompt and adequate antibiotic therapy accompanied by a mini-invasive approach, such as ultrasound-guided, laparoscopic, or video-retroperitoneoscopic drainage of the infectious focus, if indicated and feasible, is important to achieve a good outcome in the management of iliopsoas abscess.
A new structure with InGaN/AlInN/InGaN composition-graded barriers for a nitride-based light-emitting diode (LED) has been proposed and analyzed numerically. The energy band diagrams, the electrostatic fields, the carrier concentrations in the quantum well, the light output power and the internal quantum efficiency are investigated. Numerical simulation results suggest that the new structure contributes to a more uniform carrier concentration distribution, a smaller polarization electrostatic field and a more effective confinement of electrons in the active region. As a result, LEDs with this new structure attain a higher optical output power and a reduced efficiency droop of 24.7% compared with 66.6% in a conventional LED.
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