Performance of AlGaN/GaN high electron mobility transistors at nanoscale gate lengths.

The DC and RF performance of AlGaN/GaN high electron mobility transistors with nanoscale gate lengths is presented. The layer structures were grown by either metal organic chemical vapor deposition or rf plasma-assisted molecular beam epitaxy. Excellent scaling properties were observed as a function of both gate length and width and confirm that these devices are well suited to both high speed switching and power microwave applications.

Imaging of pregnancy-related complications.

Thirty-six cases of pregnancy-related complications were studied with plain radiography, ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging alone or in combination. Among the complications diagnosed with these various techniques were venous thromboembolic disorders, deep vein thrombosis, ovarian vein thrombosis, endometritis and pyometra, HELLP syndrome (hemolysis, elevated liver enzyme levels, and low platelet counts), hepatic hematoma and rupture, fatty liver, uterine rupture, various hematomas and a foreign body, tubo-ovarian abscess, cerebral venous thrombosis, cerebral ischemia, and cerebral edema. Prompt detection and appropriate management of many of these complications could result in decreased maternal and fetal mortality and morbidity. Although US should be considered first because it can be performed bedside, does not require use of ionizing radiation, and is cost-effective, CT is superior in demonstrating the extent of the abnormality and MR imaging is best for detection of neurologic complications of pregnancy. The radiologist should select the best available method and tailor the examination according to the presumptive clinical diagnosis and the individual problem to be solved.

Neonatal periventricular leukomalacia: real-time sonographic diagnosis with CT correlation.

The utility of real-time sonography in the diagnosis of neonatal periventricular leukomalacia (PVL) has been described only recently. Six cases are reported of PVL diagnosed by serial real-time scanning. The sonographic findings were correlated with the computed tomographic findings and the clinical history. In five of six infants in whom scanning was performed, characteristic multiseptated periventricular cavitations developed 2-3 weeks after birth or later. A transition from normal to increased periventricular echogenicity was often observed before the development of the periventricular cavitations in nonhemorrhagic PVL. The parenchymal abnormality demonstrated by sonography correlated well with an abnormal neurologic outcome. It is suggested that serial real-time scanning be performed in neonates whose history suggests the possibility of hypoxic-ischemic brain injury. Nonspecific predictors of PVL include seizures, apnea, disturbed mental status, abnormal muscle tone, and leg weakness.

CT and sonography in the recognition of mucocele of the appendix.

Mucocele of the appendix is uncommon, and preoperative diagnosis is rare. Diagnosis is important because some of these lesions are malignant, and early identification may reduce the incidence of pseudomyxoma peritonei. In two of three cases reviewed the correct preoperative diagnosis was established with sonography and computed tomography. These findings suggest that, in a patient who has not undergone appendectomy, the presence of a low-attenuating mass at computed tomography and a through-transmitting mass with echogenic content at sonography in the correct location is typical of mucocele.