The 1.6-Kv AlGaN/GaN HFETs

The breakdown voltages in unpassivated nonfield-plated AlGan/GaN HFETs on sapphire substrates were studied. These studies reveal that the breakdown is limited by the surface flashover rather than by the AlGan/GaN channel. after elimination of the surface flashover in air, the breakdown voltage scaled linearly with the gate-drain spacing reaching 1.6 kV at 20 mu m. The corresponding static ON-resistance was as low as 3.4 m Omega(.)cm(2). This translates to a power device figure-of-merit V-BR(2)/R-ON = 7.5 x 10(8) V-2 . n(-1) cm(-2), which, to date, is among the best reported values for an AlGan/GaN HFET

Silicon Dioxide-Encapsulated High-Voltage AlGaN/GaN HFETs for Power-Switching Applications

In this letter, new approach in achieving high breakdown voltages in AlGan/GaN heterostructure field-effect transistors (HFETs) by suppressing surface flashover using solid encapsulation material is presented. Surface flashover in III-Nitride-based HFETs limits the operating voltages at levels well below breakdown voltages of GaN. This premature gate-drain breakdown can be suppressed by immersing devices in high-dielectric-strength liquids (e.g., Fluorinert); however, such a technique is not practical. In this letter, AlGan/GaN HFETs encapsulated with PECVD-deposited SiO2 films demonstrated breakdown voltage of 900 V, very similar to that of devices immersed in Fluorinert liquid. Simultaneously, low dynamic ON-resistance of 2.43 m Omega. cm(2) has been achieved, making the developed AlGan/GaN HFETs practical high-voltage high-power switches for power-electronics applications

Digital Oxide Deposition of SiO\u3csub\u3e2\u3c/sub\u3e Layers for III-Nitride Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors

We present a digital-oxide-deposition (DOD) technique to deposit high quality SiO2dielectric layers by plasma-enhanced chemical vapor deposition using alternate pulses of silicon and oxygen precursors. The DOD procedure allows for a precise thickness control and results in extremely smooth insulating SiO2 layers. An insulating gate AlGaN∕GaNheterostructurefield-effect transistor(HFET) with 8nm thick DOD SiO2dielectric layer had a threshold voltage of −6V (only 1V higher than that of regular HFET), very low threshold voltage dispersion, and output continuous wave rf power of 15W∕mm at 55V drain bias

Psychopathology predicts the outcome of medial branch blocks with corticosteroid for chronic axial low back or cervical pain: a prospective cohort study

<p>Abstract</p> <p>Background</p> <p>Comorbid psychopathology is an important predictor of poor outcome for many types of treatments for back or neck pain. But it is unknown if this applies to the results of medial branch blocks (MBBs) for chronic low back or neck pain, which involves injecting the medial branch of the dorsal ramus nerves that innervate the facet joints. The objective of this study was to determine whether high levels of psychopathology are predictive of pain relief after MBB injections in the lumbar or cervical spine.</p> <p>Methods</p> <p>This was a prospective cohort study. Consecutive patients in a pain medicine practice undergoing MBBs of the lumbar or cervical facets with corticosteroids were recruited to participate. Subjects were selected for a MBB based on operationalized selection criteria and the procedure was performed in a standardized manner. Subjects completed the Brief Pain Inventory (BPI) and the Hospital Anxiety and Depression Scale (HADS) just prior to the procedure and at one-month follow up. Scores on the HADS classified the subjects into three groups based on psychiatric symptoms, which formed the primary predictor variable: <it>Low</it>, <it>Moderate</it>, or <it>High </it>levels of psychopathology. The primary outcome measure was the percent improvement in average daily pain rating one-month following an injection. Analysis of variance and chi-square were used to analyze the analgesia and functional rating differences between groups, and to perform a responder analysis.</p> <p>Results</p> <p>Eighty six (86) subjects completed the study. The <it>Low </it>psychopathology group (n = 37) reported a mean of 23% improvement in pain at one-month while the <it>High </it>psychopathology group (n = 29) reported a mean worsening of -5.8% in pain (p < .001). Forty five percent (45%) of the <it>Low </it>group had at least 30% improvement in pain versus 10% in the <it>High </it>group (p < .001). Using an analysis of covariance, no baseline demographic, social, or medical variables were significant predictors of pain improvement, nor did they mitigate the effect of psychopathology on the outcome.</p> <p>Conclusion</p> <p>Psychiatric comorbidity is associated with diminished pain relief after a MBB injection performed with steroid at one-month follow-up. These findings illustrate the importance of assessing comorbid psychopathology as part of a spine care evaluation.</p

Analyzing a fake news authorship network

This project synthesizes a set of 246 fake news websites previously identified in three earlier research projects. From this dataset, we extract a set of all authors who have written for these sites in 2016. This authorcentric dataset is itself a contribution that will allow future analysis of the fake news ecosystem. Based on the data we collected, we construct a network of fake news sites, linking them if they shared a common author. Our analysis shows a tight cluster of author-sharing sites, with a small core set of sites sharing dozens of authors

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Pulmonary and peritoneal tuberculosis associated with tumor necrosis factor-alpha inhibitor use: a case report and review of the literature.

The association between the use of tumor necrosis factor-α inhibitors and the increased risk of granulomatous infections, especially tuberculosis, has been well documented. Given the rapidly expanding list of inflammatory conditions for which tumor necrosis factor-α inhibitors are receiving FDA approval, the incidence of tuberculosis in this patient population has increased. Despite heightened awareness by physicians, the diagnosis of tuberculosis can remain challenging, given that extrapulmonary sites of infection are more frequently involved. We present a case of pulmonary and peritoneal tuberculosis in a gentleman being treated with a tumor necrosis factor-α inhibitor and discuss the diagnostic challenges of establishing the diagnosis

An efficient high frequency drive circuit for GaN power HFETs

The requirements for driving gallium nitride (GaN) heterostructure field-effect transistors (HFETs) and the design of a resonant drive circuit for GaN power HFET switches are discussed in this paper. The use of wideband III-nitride (such as GaN) devices today is limited to telecom and low-power applications. The current lack of high-frequency high-power drivers prevents their application in power converters. The proposed circuit is based upon resonant switching transition techniques, by means of an LC tag, to recover part of the power back into the voltage source in order to reduce the power loss. This circuit also uses level shifters to generate the zero and negative gate-source voltages required to turn the GaN HFET on and off, and it is highly tolerant to input-signal timing variances. The circuit reduces the overall power consumed in the driver and thus reduces the power loss. This is particularly important for high-frequency driver operation to take full advantage, in terms of efficiency, of the superior switching speed of GaN devices. In this paper, the topology of the low-power-loss high-speed drive circuit is introduced. Some simulation results and preliminary experimental measurements are discussed

A resonant drive circuit for GaN power MOSHFET

The rapid development of the research on Gallium Nitride semiconductor material and the unique properties of GaN (such as high electron mobility and saturation velocity, high sheet carrier concentration at hetero-junction interfaces, high breakdown voltages, and low thermal- impedance) make the material promising in high-power, high-temperature applications. Accordingly, a design for a drive circuit for GaN switches is increasingly in demand. Until now, however, specific gate drivers for GaN switches are not available yet. In this paper, a new resonant drive circuit for GaN power MOSHFET switches is discussed. This circuit employs a resonant LC tag to recover part of the power back into the voltage source in order to reduce the power loss. It also applies a topology which can increase the voltage level relative to the energy supply, generate the zero and negative gate-source voltages required to turn the GaN MOSHFET on and off, and make the circuit highly tolerant to input signal timing variance. This function reduces the overall power consumed in the driver and thus reduces the power loss. This is particularly important for high-frequency driver operation, to take full advantage of the superior switching speed of GaN devices. In this paper, the topology of the low-power-loss, high-speed drive circuit will be introduced and the simulation results will be discussed