Bonding wire interconnection de-embedding for GaN high electron mobility transistor loadpull measurement with fixture.

Test fixtures with high power capacity and an impedance matching network are generally chosen for measurements of high-power gallium nitride high electron mobility transistors. To make interconnection of the test fixtures and devices under test, wire bonding is an effective assembly method. Bonding wires become dominant parasitic elements, especially in the S parameter measurement and loadpull measurement, which should be taken into account and accurately de-embedded for device measurements and modeling. In this paper, test fixtures and through-reflect-line calibration kits are designed to achieve the S parameter measurements of the bonding wire with a vector network analyzer. Equivalent inductances of the bonding wire can be obtained with the electromagnetic simulation model and compact circuit model proposed based on the test fixture. The good agreement of the equivalent inductances extracted with the test fixture and models verified that the way to characterize bonding wire interconnection is effective and accurate. Cree's CGHV1J006D is chosen to take the S parameter measurement for proving the accurate model of the bonding wire. Finally, the equivalent inductance of the 2 mm gate-width transistor is obtained with the electromagnetic model. The drain impedance is accurately calculated after the loadpull measurement with bonding wire effects de-embedded, which matches the loadline theory.

Improved measurement techniques for high-power transistor modeling.

Measurement for modeling of the high-power transistors is difficult due to its high-power and low-impedance characteristics. In this paper, novel methods and devices were designed and applied to achieve precise measurements of the high-power transistors. Fixtures capable of withstanding high voltage and current were designed to replace traditional radio frequency (RF) probes for higher power capacity. To reduce the impact of capacitive and inductive components of traditional bias tees on the rising/falling edge, two wideband 90° hybrid couplers that were connected back-to-back were designed for pulsed measurements. The measurement system of stable S-parameters with the Vector Network Analyzer (VNA) was reported, which could protect the devices and laboratory equipment from damage of self-oscillation. Application of several innovative approaches enabled accurate I-V characteristic and S-parameters measurements of high-power transistors in DC or pulsed mode. Experimental results of a 30 W gallium nitride high-electron-mobility transistor verified the validity.

Less Vertebral Bone Mass after Treatment with Macitentan in Mice: A Pilot Study.

PURPOSE: Blood vessels and skeleton interact together. Endothelin-1 is a potent vasoconstrictor and also has an effect on bone metabolism. The dual antagonist to both endothelin-1 type A and B receptors, Macitentan, has been approved for clinical management of pulmonary arterial hypertension while little is known about the secondary effect of the drug on spine. We aimed to answer how vertebral bone mass responded to Macitentan treatment in mice. METHODS: Sixteen male balb/c mice at 6 months were randomly assigned into 2 groups. Vehicle and Macitentan were administrated via intraperitoneal injection to Control group and Treatment group, respectively, for 4 months. At sacrifice, plasma endothelin-1 was evaluated with ELISA and vertebral bone mass was evaluated with Microcomputed Tomography and histological analysis. RESULTS: We found higher plasma endothelin-1 level (p<0.01) and less vertebral bone mass (p<0.05) in Treatment group compared to controls. Moreover, less osteoblasts and more osteoclasts were observed in the vertebral trabecular bone in the Treatment group compared to controls, by immunohistochemistry of the cell-specific markers. CONCLUSIONS: Treatment with Macitentan is associated with significant lower vertebral bone mass and therefore the secondary effect of dual antagonists to endothelin-1 receptors on the skeleton should be monitored and investigated in clinical practice. Both osteoblasts and osteoclasts may be involved while the molecular mechanism needs to be further explored.

Intraoperative frozen section analysis of urethral margin biopsies during radical prostatectomy.

OBJECTIVES: To evaluate the accuracy and potential clinical value of intraoperative frozen section analysis (FSA) on urethral margin (UM) tissue during radical prostatectomy. Positive surgical margins increase the risk of post-operative cancer recurrence. Positive surgical margins are frequently found at the apex. The utility of intraoperative FSA of the margins is controversial. METHODS: We reviewed a consecutive series of radical prostatectomy cases (n = 1669) performed at our institution, in which UMs were routinely evaluated by intraoperative FSA. RESULTS: The submitted UM tissue contained cancer glands in 111 cases (6.7%). On FSA, the pathologists detected cancer in 55 cases (3.3%), missed cancer in 38 (2.3%), and reported atypical glands in 18 (1.1%). FSA of the UMs had a sensitivity of 59.1%, specificity of 99.8%, and positive and negative predictive value of 94.8% and 97.6%, respectively. The low sensitivity resulted from a substantial false-negative rate (n = 38), which was largely attributed to limited sampling on FSA (n = 31). Of the 55 patients (3.3%) whose positive UMs were detected by FSA, 20 (1.2%) had cancer-free margins after tissue re-excision. A positive final UM was associated with greater biochemical recurrence (P = .0073). However, the few patients limited the statistical analysis of the benefit of margin conversion through tissue re-excision (P = .35). CONCLUSIONS: Although experienced pathologists can evaluate the UMs on FSA with good accuracy, FSA has a relatively low sensitivity. Our data have indicated a low yield and a questionable value of routine FSA during radical prostatectomy.