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RISS 인기검색어
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- 저자 : Simpkins, B. (검색결과 4 건)
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Polarization and Space-Charge-Limited Current in III-Nitride Heterostructure Nanowires
Mastro, M. A.,Hong-Youl Kim,Jaehui Ahn,Simpkins, B.,Pehrsson, P.,Jihyun Kim,Hite, J. K.,Eddy, C. R. IEEE 2011 IEEE transactions on electron devices Vol.58 No.10
<P>An undoped AlGaN/GaN nanowire (NW) demonstrated p-type conductivity solely based on the formation of hole carriers in response to the negative polarization field at the (000-1) AlGaN/GaN facet. A transistor based on this NW displayed a low-voltage transition from ohmic to space-charge-limited conduction. A numerical simulation showed that a highly asymmetric strain exists across the triangular cross section, which creates a doublet peak in the piezoelectric-induced polarization sheet charge at the (000-1) facet. Additionally, there is a strong interplay between the charge at the (000-1) AlGaN/GaN interface with depletion from the three surfaces, as well as an interaction with the opposing polarization fields at two semipolar {- 110-1} facets. The charge distribution and resultant conduction regime is highly interdependent on the configuration of the multilayer structure, and it is not amenable to an analytical model.</P>
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Group III-nitride radial heterojunction nanowire light emitters
Michael A. Mastro,Josh Caldwell,Mark Twigg,Blake Simpkins,Orest Glembocki,Ron T. Holm,Charles R. Eddy, Jr.,Fritz Kub,김홍렬,Jaehui Ahn,김지현 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
Heterojunction nanowires were fabricated via a vapor-liquid-solid growth mechanism in a metal organic chemical vapor deposition system. The structure consisted of a n-type GaN:Si core surrounding by a distinct p-type AlGaN:Mg shell. Transmission electron microscopy revealed that the nanowires were free of extended defects. Photoluminescence measured a strong UV emission peak. Additionally, sources of mid-gap transitions are linked to surface states on the nanowire surface.
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Outcome Prediction in Cerebral Venous Thrombosis: The IN-REvASC Score
Piers Klein,Liqi Shu,Thanh N. Nguyen,James E. Siegler,Setareh Salehi Omran,Alexis N. Simpkins,Mirjam Heldner,Adam de Havenon,Hugo J. Aparicio,Mohamad Abdalkader,Marios Psychogios,Maria Cristina Vedova 대한뇌졸중학회 2022 Journal of stroke Vol.24 No.3
Background We identified risk factors, derived and validated a prognostic score for poor neurological outcome and death for use in cerebral venous thrombosis (CVT). Methods We performed an international multicenter retrospective study including consecutive patients with CVT from January 2015 to December 2020. Demographic, clinical, and radiographic characteristics were collected. Univariable and multivariable logistic regressions were conducted to determine risk factors for poor outcome, mRS 3-6. A prognostic score was derived and validated. Results A total of 1,025 patients were analyzed with median 375 days (interquartile range [IQR], 180 to 747) of follow-up. The median age was 44 (IQR, 32 to 58) and 62.7% were female. Multivariable analysis revealed the following factors were associated with poor outcome at 90- day follow-up: active cancer (odds ratio [OR], 11.20; 95% confidence interval [CI], 4.62 to 27.14; P<0.001), age (OR, 1.02 per year; 95% CI, 1.00 to 1.04; P=0.039), Black race (OR, 2.17; 95% CI, 1.10 to 4.27; P=0.025), encephalopathy or coma on presentation (OR, 2.71; 95% CI, 1.39 to 5.30; P=0.004), decreased hemoglobin (OR, 1.16 per g/dL; 95% CI, 1.03 to 1.31; P=0.014), higher NIHSS on presentation (OR, 1.07 per point; 95% CI, 1.02 to 1.11; P=0.002), and substance use (OR, 2.34; 95% CI, 1.16 to 4.71; P=0.017). The derived IN-REvASC score outperformed ISCVT-RS for the prediction of poor outcome at 90-day follow-up (area under the curve [AUC], 0.84 [95% CI, 0.79 to 0.87] vs. AUC, 0.71 [95% CI, 0.66 to 0.76], χ2 P<0.001) and mortality (AUC, 0.84 [95% CI, 0.78 to 0.90] vs. AUC, 0.72 [95% CI, 0.66 to 0.79], χ2 P=0.03). Conclusions Seven factors were associated with poor neurological outcome following CVT. The INREvASC score increased prognostic accuracy compared to ISCVT-RS. Determining patients at highest risk of poor outcome in CVT could help in clinical decision making and identify patients for targeted therapy in future clinical trials.
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Madeleine Matthiesen,Michael S. Kelly,Kristina Dzara,Arabella Simpkin Begin 한국보건의료인국가시험원 2022 보건의료교육평가 Vol.19 No.-
Purpose: Residents and attendings agree on the importance of feedback to resident education. However, while faculty report providingfrequent feedback, residents often do not perceive receiving it, particularly in the context of teaching. Given the nuanced differences between feedback and teaching, we aimed to explore resident and attending perceptions of feedback and teaching in the clinical setting. Methods: We conducted a qualitative study of internal medicine residents and attendings from December 2018 through March 2019at the Massachusetts General Hospital to investigate perceptions of feedback in the inpatient clinical setting. Residents and faculty wererecruited to participate in focus groups. Data were analyzed using thematic analysis to explore perspectives and barriers to feedback provision and identification. Results: Five focus groups included 33 total participants in 3 attending (n=20) and 2 resident (n=13) groups. Thematic analysis of focus group transcripts identified 7 themes which organized into 3 thematic categories: (1) disentangling feedback and teaching, (2) delivering high-quality feedback, and (3) experiencing feedback in the group setting. Residents and attendings highlighted importantthemes in discriminating feedback from teaching. They indicated that while feedback is reactive in response to an action or behavior,teaching is proactive and oriented toward future endeavors. Conclusion: Confusion between the critical concepts of teaching and feedback may be minimized by allowing them to each have theirintended impact, either in response to prior events or aimed toward those yet to take place.
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