Low-dislocation-density GaN from a single growth on a textured substrate

The density of threading dislocations (TD) in GaN grown directly on flat sapphire substrates is typically greater than 10{sup 9}/cm{sup 2}. Such high dislocation densities degrade both the electronic and photonic properties of the material. The density of dislocations can be decreased by orders of magnitude using cantilever epitaxy (CE), which employs prepatterned sapphire substrates to provide reduced-dimension mesa regions for nucleation and etched trenches between them for suspended lateral growth of GaN or AlGaN. The substrate is prepatterned with narrow lines and etched to a depth that permits coalescence of laterally growing III-N nucleated on the mesa surfaces before vertical growth fills the etched trench. Low dislocation densities typical of epitaxial lateral overgrowth (ELO) are obtained in the cantilever regions and the TD density is also reduced up to 1 micrometer from the edge of the support regions

Low-Dislocation-Density GaN from a Single Growth on a Textured Substrate

The density of threading dislocations (TD) in GaN grown directly on flat sapphire substrates is typically greater than 10{sup 9}/cm{sup 2}. Such high dislocation densities degrade both the electronic and photonic properties of the material. The density of dislocations can be decreased by orders of magnitude using cantilever epitaxy (CE), which employs prepatterned sapphire substrates to provide reduced-dimension mesa regions for nucleation and etched trenches between them for suspended lateral growth of GaN or AlGaN. The substrate is prepatterned with narrow lines and etched to a depth that permits coalescence of laterally growing III-N nucleated on the mesa surfaces before vertical growth fills the etched trench. Low dislocation densities typical of epitaxial lateral overgrowth (ELO) are obtained in the cantilever regions and the TD density is also reduced up to 1 micrometer from the edge of the support regions

Pleiotropic effect of the proton pump inhibitor esomeprazole leading to suppression of lung inflammation and fibrosis

Background: The beneficial outcome associated with the use of proton pump inhibitors (PPIs) in idiopathic pulmonary fibrosis (IPF) has been reported in retrospective studies. To date, no prospective study has been conducted to confirm these outcomes. In addition, the potential mechanism by which PPIs improve measures of lung function and/or transplant-free survival in IPF has not been elucidated. Methods: Here, we used biochemical, cell biological and preclinical studies to evaluate regulation of markers associated with inflammation and fibrosis. In our in vitro studies, we exposed primary lung fibroblasts, epithelial and endothelial cells to ionizing radiation or bleomycin; stimuli typically used to induce inflammation and fibrosis. In addition, we cultured lung fibroblasts from IPF patients and studied the effect of esomeprazole on collagen release. Our preclinical study tested efficacy of esomeprazole in a rat model of bleomycin-induced lung injury. Furthermore, we performed retrospective analysis of interstitial lung disease (ILD) databases to examine the effect of PPIs on transplant-free survival. Results: The cell culture studies revealed that esomeprazole controls inflammation by suppressing the expression of pro-inflammatory molecules including vascular cell adhesion molecule-1, inducible nitric oxide synthase, tumor necrosis factor-alpha (TNF-alpha) and interleukins (IL-1 beta and IL-6). The antioxidant effect is associated with strong induction of the stress-inducible cytoprotective protein heme oxygenase-1 (HO1) and the antifibrotic effect is associated with potent inhibition of fibroblast proliferation as well as downregulation of profibrotic proteins including receptors for transforming growth factor beta (TGF beta), fibronectin and matrix metalloproteinases (MMPs). Furthermore, esomeprazole showed robust effect in mitigating the inflammatory and fibrotic responses in a murine model of acute lung injury. Finally, retrospective analysis of two ILD databases was performed to assess the effect of PPIs on transplant-free survival in IPF patients. Intriguingly, this data demonstrated that IPF patients on PPIs had prolonged survival over controls (median survival of 3.4 vs 2 years). Conclusions: Overall, these data indicate the possibility that PPIs may have protective function in IPF by directly modulating the disease process and suggest that they may have other clinical utility in the treatment of extra-intestinal diseases characterized by inflammatory and/or fibrotic phases.Stanford School of Medicine [1049528-149- KAVFB]; Tobacco-Related Disease Research Program of the University of California [20FT-0090]; National Institutes of Health National Heart, Lung, and Blood Institute [5K01HL118683, P01HL114470]; Houston Methodist Research Institute [25150001]; Stanford SPARK Translational Research ProgramSCI(E)[email protected]

Pleiotropic effect of the proton pump inhibitor esomeprazole leading to suppression of lung inflammation and fibrosis

BackgroundThe beneficial outcome associated with the use of proton pump inhibitors (PPIs) in idiopathic pulmonary fibrosis (IPF) has been reported in retrospective studies. To date, no prospective study has been conducted to confirm these outcomes. In addition, the potential mechanism by which PPIs improve measures of lung function and/or transplant-free survival in IPF has not been elucidated.MethodsHere, we used biochemical, cell biological and preclinical studies to evaluate regulation of markers associated with inflammation and fibrosis. In our in vitro studies, we exposed primary lung fibroblasts, epithelial and endothelial cells to ionizing radiation or bleomycin; stimuli typically used to induce inflammation and fibrosis. In addition, we cultured lung fibroblasts from IPF patients and studied the effect of esomeprazole on collagen release. Our preclinical study tested efficacy of esomeprazole in a rat model of bleomycin-induced lung injury. Furthermore, we performed retrospective analysis of interstitial lung disease (ILD) databases to examine the effect of PPIs on transplant-free survival.ResultsThe cell culture studies revealed that esomeprazole controls inflammation by suppressing the expression of pro-inflammatory molecules including vascular cell adhesion molecule-1, inducible nitric oxide synthase, tumor necrosis factor-alpha (TNF-α) and interleukins (IL-1β and IL-6). The antioxidant effect is associated with strong induction of the stress-inducible cytoprotective protein heme oxygenase-1 (HO1) and the antifibrotic effect is associated with potent inhibition of fibroblast proliferation as well as downregulation of profibrotic proteins including receptors for transforming growth factor β (TGFβ), fibronectin and matrix metalloproteinases (MMPs). Furthermore, esomeprazole showed robust effect in mitigating the inflammatory and fibrotic responses in a murine model of acute lung injury. Finally, retrospective analysis of two ILD databases was performed to assess the effect of PPIs on transplant-free survival in IPF patients. Intriguingly, this data demonstrated that IPF patients on PPIs had prolonged survival over controls (median survival of 3.4 vs 2 years).ConclusionsOverall, these data indicate the possibility that PPIs may have protective function in IPF by directly modulating the disease process and suggest that they may have other clinical utility in the treatment of extra-intestinal diseases characterized by inflammatory and/or fibrotic phases

Longitudinal Assessment of Resident Performance Using Entrustable Professional Activities

Question What is the progression of performance for entrustable professional activities (EPAs) throughout pediatric residency training and at graduation? Findings This multisite cohort study of 1987 pediatric residents found that developmental growth curves can be established for EPAs. When generated to reflect the results in this study, at least 90% of trainees achieved the level of unsupervised practice at the end of residency for only 8 of the 17 EPAs studied. Meaning This study suggests that gaps exist between observed practice readiness and standards needed to produce physicians able to meet the health needs of the patient populations they serve based on the general pediatrics EPAs. Importance Entrustable professional activities (EPAs) are an emerging workplace-based, patient-oriented assessment approach with limited empirical evidence. Objective To measure the development of pediatric trainees' clinical skills over time using EPA-based assessment data. Design, Setting, and Participants Prospective cohort study of categorical pediatric residents over 3 academic years (2015-2016, 2016-2017, and 2017-2018) assessed on 17 American Board of Pediatrics EPAs. Residents in training at 23 pediatric residency programs in the Association of Pediatric Program Directors Longitudinal Educational Assessment Research Network were included. Assessment was conducted by clinical competency committee members, who made summative assessment decisions regarding levels of supervision required for each resident and each EPA. Data were collected from May 2016 to November 2018 and analyzed from November to December 2018. Interventions Longitudinal, prospective assessment using EPAs. Main Outcomes and Measures Trajectories of supervision levels by EPA during residency training and how often graduating residents were deemed ready for unsupervised practice in each EPA. Results Across the 5 data collection cycles, 1987 residents from all 3 postgraduate years in 23 residency programs were assigned 25503 supervision level reports for the 17 general pediatrics EPAs. The 4 EPAs that required the most supervision across training were EPA 14 (quality improvement) on the 5-level scale (estimated mean level at graduation, 3.7; 95% CI, 3.6-3.7) and EPAs 8 (transition to adult care; mean, 7.0; 95% CI, 7.0-7.1), 9 (behavioral and mental health; mean, 6.6; 95% CI, 6.5-6.6), and 10 (resuscitate and stabilize; mean, 6.9; 95% CI, 6.8-7.0) on the expanded 5-level scale. At the time of graduation (36 months), the percentage of trainees who were rated at a supervision level corresponding to "unsupervised practice" varied by EPA from 53% to 98%. If performance standards were set to align with 90% of trainees achieving the level of unsupervised practice, this standard would be met for only 8 of the 17 EPAs (although 89% met this standard for EPA 17, performing the common procedures of the general pediatrician). Conclusions and Relevance This study presents initial evidence for empirically derived practice readiness and sets the stage for identifying curricular gaps that contribute to discrepancy between observed practice readiness and standards needed to produce physicians able to meet the health needs of the patient populations they serve. Future work should compare these findings with postgraduation outcomes data as a means of seeking validity evidence. This cohort study measures the development of pediatric resident clinical skills using assessments based on entrustable professional activities