High hole concentration was achieved in Mg-doped AlxGa1−xN (x ∼ 0.4) by using indium-surfactant-assisted delta doping method. A maximum carrier concentration of 4.75 × 1018 cm−3 was obtained, which is three times higher than that of the conventionally delta-doped sample. Sheet resistivity as low as 2.46 × 104 Ω/sq was realized, benefiting from the high hole concentration (p). Analysis results show that the Mg incorporation is effectively enhanced, while the compensation ratio and acceptor activation energy (EA) are significantly reduced by using In surfactant. It was also found that the In surfactant may induce stronger valence-band modulation, contributing to the decrease of EA and the increase of p.

Retrograde jejunogastric intussusception (JGI) is a rare but potentially fatal complication after previous gastrectomy or gastric bypass surgery. Because of the prevalence of bariatric surgery, the number of cases of postoperative intussusception has increased markedly. Here, we present the case of a patient with retrograde jejunogastric intussusception, having a previous history of subtotal gastrectomy and gastrojejunostomy for peptic ulcer disease. Correct preoperative diagnosis was made by plain abdominal film, upper gastrointestinal series, computed tomographic scan, and esophagogastroduodenoscopy. The diagnosis was confirmed by laparoscopic examination.

Laparoscopy has been used for the diagnosis and treatment for hemodynamically stable patients with penetrating abdominal trauma. This study evaluated whether diagnostic and therapeutic laparoscopy can be used as effectively in select patients with blunt abdominal trauma. All hemodynamically stable patients undergoing operations for blunt abdominal trauma over a 10-year period (2006–2015) at a tertiary medical center were included. Patients undergoing laparotomy were categorized as group A. Patients who underwent laparoscopy were categorized as group B. The clinical outcomes of the 2 groups were compared. There were 139 patients in group A and 126 patients in group B. Group A patients were more severely injured (mean injury severity score of 23.3 vs. 18.9, P < .001) and had a higher frequency of traumatic brain injuries (25.2% vs. 14.3%, P = .039). The sensitivity and specificity of diagnostic laparoscopy for patients in group B was 99.1% and 100.0%, respectively. No non-therapeutic laparotomies were performed in group B, and the success rate of therapeutic laparoscopy was 92.0% (103/112) for patients with significant intra-abdominal injuries. Patients in the 2 groups had similar perioperative and postoperative outcomes in terms of operation times, blood loss, blood transfusion requirements, mortality, and complications (all, P > .05). Laparoscopy is a feasible and safe tool for the diagnosis and treatment of hemodynamically stable patients with blunt abdominal trauma who require surgery.

No abstract

A game-theoretic analysis of decode and forward cooperative communications is presented for additive white Gaussian noise (AWGN) and Rayleigh fading channels. Cooperative communications is modeled as a repeated game in which the two participating terminals are selfish and seek to maximize their own payoff, a general utility function that monotonically increases with signal-to-noise ratio. Results show a Nash Equilibrium in which users mutually cooperate can be obtained for AWGN channels when strict power control is enforced and users care about future payoff. However, such power control may not be necessary to achieve cooperative Nash Equilibrium when the game is played in Rayleigh fading channels. We study the Rayleigh fading channel as a two state Markov model in this paper. In this case, a mutually cooperative Nash Equilibrium 1) always exists when the utility function is convex and users care somewhat about future payoff; and 2) may not always exist when the utility function is concave, especially in adverse channel conditions. Examinations of several widely-used concave functions, however, demonstrate that mutual cooperation is more likely when users increase their value on future payoff. Additionally, it is shown that improving the effective uplink channel conditions of users, e.g., by using multiple transmit antennas, further encourages cooperation.