Hot-Electron Electroluminescence under RF Operation in GaN-HEMTs::A Comparison Among Operational Classes

Electroluminescence microscopy and spectroscopy are used to compare the average hot-electron concentration and temperature under radio frequency (RF) operation class A, class B, and class F modes. From the results obtained, class A results, on average, in the highest hot-electron concentration, while class F is the mode with the lowest concentration due to its “L”-shaped load line. The electron temperature extracted from the electroluminescence spectra is reduced with increasing RF power, reflecting the dominance of electroluminescence from the portion of the load line in the semi-on region. The electroluminescence method is not able to give substantial information on the portion of the load line with high field and low current density which will be responsible for the potentially damaging hottest electrons present in the channel

Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation

Hot electrons in AlGaN/GaN high electron mobility transistors are studied during radio frequency (RF) and DC operation by means of electroluminescence (EL) microscopy and spectroscopy. The measured EL intensity is decreased under RF operation compared to DC at the same average current, indicating a lower hot electron density. This is explained by averaging the DC EL intensity over the measured load line used in RF measurements, giving reasonable agreement. In addition, the hot electron temperature is lower by up to 15% under RF compared to DC, again at least partially explainable by the weighted averaging along the specific load line. However, peak electron temperature under RF occurs at high VDS and low IDS where EL is insignificant suggesting that any wear-out differences between RF and DC stress of the devices will depend on the balance between hot-carrier and field driven degradation mechanisms

A dosimetric comparison of real-time adaptive and non-adaptive radiotherapy: A multi-institutional study encompassing robotic, gimbaled, multileaf collimator and couch tracking

AbstractPurposeA study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiotherapy in the presence of patient-measured tumor motion.Methods and materialsTen institutions with robotic(2), gimbaled(2), MLC(4) or couch tracking(2) used common materials including CT and structure sets, motion traces and planning protocols to create a lung and a prostate plan. For each motion trace, the plan was delivered twice to a moving dosimeter; with and without real-time adaptation. Each measurement was compared to a static measurement and the percentage of failed points for γ-tests recorded.ResultsFor all lung traces all measurement sets show improved dose accuracy with a mean 2%/2mm γ-fail rate of 1.6% with adaptation and 15.2% without adaptation (p<0.001). For all prostate the mean 2%/2mm γ-fail rate was 1.4% with adaptation and 17.3% without adaptation (p<0.001). The difference between the four systems was small with an average 2%/2mm γ-fail rate of <3% for all systems with adaptation for lung and prostate.ConclusionsThe investigated systems all accounted for realistic tumor motion accurately and performed to a similar high standard, with real-time adaptation significantly outperforming non-adaptive delivery methods

Refining Critical Structure Contouring in STereotactic Arrhythmia Radioablation (STAR): Benchmark Results and Consensus Guidelines from the STOPSTORM.eu Consortium.

BACKGROUND AND PURPOSE In patients with recurrent ventricular tachycardia (VT), STereotactic Arrhythmia Radioablation (STAR) shows promising results. The STOPSTORM consortium was established to investigate and harmonise STAR treatment in Europe. The primary goals of this benchmark study were to standardise contouring of organs at risk (OAR) for STAR, including detailed substructures of the heart, and accredit each participating centre. MATERIALS AND METHODS Centres within the STOPSTORM consortium were asked to delineate 31 OAR in three STAR cases. Delineation was reviewed by the consortium expert panel and after a dedicated workshop feedback and accreditation was provided to all participants. Further quantitative analysis was performed by calculating DICE similarity coefficients (DSC), median distance to agreement (MDA), and 95th percentile distance to agreement (HD95). RESULTS Twenty centres participated in this study. Based on DSC, MDA and HD95, the delineations of well-known OAR in radiotherapy were similar, such as lungs (median DSC=0.96, median MDA=0.1mm and median HD95=1.1mm) and aorta (median DSC=0.90, median MDA=0.1mm and median HD95=1.5mm). Some centres did not include the gastro-oesophageal junction, leading to differences in stomach and oesophagus delineations. For cardiac substructures, such as chambers (median DSC=0.83, median MDA=0.2mm and median HD95=0.5mm), valves (median DSC=0.16, median MDA=4.6mm and median HD95=16.0mm), coronary arteries (median DSC=0.4, median MDA=0.7mm and median HD95=8.3mm) and the sinoatrial and atrioventricular nodes (median DSC=0.29, median MDA=4.4mm and median HD95=11.4mm), deviations between centres occurred more frequently. After the dedicated workshop all centres were accredited and contouring consensus guidelines for STAR were established. CONCLUSION This STOPSTORM multi-centre critical structure contouring benchmark study showed high agreement for standard radiotherapy OAR. However, for cardiac substructures larger disagreement in contouring occurred, which may have significant impact on STAR treatment planning and dosimetry evaluation. To standardize OAR contouring, consensus guidelines for critical structure contouring in STAR were established

Long term safety and visibility of a novel liquid fiducial marker foruse in image guided radiotherapy of non-small cell lung cancer

Safety and clinical feasibility of injecting a novel liquid fiducial marker for use in image guided radiotherapy in 15 patients with non-small cell lung cancer are reported. No major safety or toxicity issues were encountered. Markers present at start of radiotherapy remained visible in cone beam computed tomography and fluoroscopy images throughout the treatment course and on computed tomography images during follow-up (0–38 months). Marker volume reduction was seen until 9 months after treatment, after which no further marker breakdown was found. No post-treatment migration or marker related complications were found. Keywords: Liquid fiducial marker, Image-guided radiotherapy, NSCLC, Endoscopic ultrasound, EBU

Heterostructures for High Performance Devices

Contains an introduction, reports on thirteen research projects and a list of publications.Charles S. Draper Laboratory Contract DL-H-418483DARPA/NCIPT Subcontract 542383Joint Services Electronics Program Contract DAAL03-89-C-0001IBM Corporation FellowshipNational Science Foundation FellowshipVitesse SemiconductorAT&T Bell LaboratoriesHertz Foundation FellowshipNational Science FoundationTRWBelgian American Education Foundation (BAEF) FellowshipNational Science Foundation Grant ECS 90-08485Harvard University. Division of Applied PhysicsAT&T Bell Laboratories FellowshipNational Science Foundation Grant ECS 90-0774

Cardiac electrophysiologic interactions of bepridil, a new calcium antagonist, with enflurane, halothane, and isoflurane

Bepridil is an investigational calcium antagonist that also has fast sodium channel blocking and antidysrhythmic properties. In the present study, the potential interactions of bepridil with volatile anesthetics on cardiac electrophysiologic parameters were evaluated ] in open-chest dogs. Twenty-four dogs anesthetized with enflurane (n = 6), halothane (n = 6), isoflurane (n = 6), or chloralose (n = 6) received 2.5 mg/kg of bepridil intravenously (IV). Twenty-five additional dogs anesthetized with enflurane (n = 7), halothane (n = 6), isoflurane (n = 6), or chloralose (n = 6), received bepridil, 5.0 mg/kg, IV. Dogs anesthetized with cloralose served as controls. Cardiac electrophysiologic parameters were measured after the dogs were anesthetized and were repeated 5, 15, 30, 45, and 60 minutes after bepridil infusion. Plasma bepridil concentrations were also determined at the above time points. Synergy between bepridil and enflurane was demonstrated in the following cardiac electrophysiologic parameters: depression of sinus node function as evidenced by severe depression of sinus node automaticity and conduction; depression of atrioventricular function as evidenced by prolongation of the atrial--His bundle interval and the Wenckebach R-R interval; and, prolongation of the atrial effective refractory period. No synergy was demonstrated between bepridil and halothane or isoflurane when compared to bepridil's effects during chloralose anesthesia. It is concluded that significant synergistic cardiac electrophysiologic effects exist between bepridil and enflurane in dogs. It is recommended that caution be used when anesthetizing patients receiving bepridil with enflurane until human data on the use of this combination of pharmacologic agents is available.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27283/1/0000299.pd

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe