Facilitation of a tropical seagrass by a chemosymbiotic bivalve increases with environmental stress

Facilitation of foundation species is critical to the structure, function and persistence of ecosystems. Understanding the dependence of the strength of this facilitation on environmental conditions is important for informed ecosystem management and for predicting the impacts of global change. In coastal seagrass habitats, chemosymbiotic lucinid bivalves can facilitate seagrasses by decreasing potentially toxic levels of sulphide in sediment porewater. However, variation in the strength of lucinid–seagrass facilitation with environmental context has not been experimentally investigated. We tested the hypothesis that the presence of the tiger lucine Codakia orbicularis becomes more important to the growth and survival of the seagrass Thalassia testudinum under decreased light availability and increased sulphide stress. In a mesocosm experiment, we reduced average ambient-light to T. testudinum by 64% and/or increased sediment porewater sulphide concentrations by ~200% and compared growth and tissue chemistry of T. testudinum with and without C. orbicularis. We found that T. testudinum was better able to maintain growth under shading and sulphide stress when C. orbicularis was present. C. orbicularis strongly decreased sediment porewater sulphide, an effect that minimized sulphur build-up in seagrass tissue and was likely achieved through bioirrigation as well as chemoautotrophy. The relative effects of C. orbicularis on T. testudinum growth were strongest in the presence of environmental stressors. Synthesis. The strength of lucinid–seagrass facilitation increases under environmental conditions that hinder the ability of seagrass to detoxify sulphide. Our results provide evidence of a potential mechanism by which the spatiotemporal association between lucinids and seagrasses is maintained and support the incorporation of interspecific facilitation into conservation and restoration strategies for foundation species in the face of increasing anthropogenic impact and global change

A Modeling Methodology for Real-Time/Multimedia Operating Systems

Real-time scheduling theory attempts to guarantee that a real-time task set will always meet its deadlines. Historically, there has existed a wide gap between real-time scheduling theory and the reality of applying the theory to task sets implemented via real-time operating systems (RTOSs). This paper provides a framework to account for implementation costs in real-time scheduling theory. In addition, an engineering methodology that allows users and developers to accurately model and evaluate RTOSs is presented. We use this methodology to model three different commercial real-time operating systems that are being used in multimedia applications. We show how to use the RTOS scheduling models to evaluate the performance and design of RTOSs. 1.0 Introduction Real-time scheduling theory attempts to guarantee that a set of real-time tasks can meet their timing requirements under worst case conditions [LIU73]. However, this idealized scheduling theory has generally ignored the implementati..

A Prospective Multicenter Study Evaluating Endoscopy Competence Among Gastroenterology Trainees in the Era of the Next Accreditation System

PURPOSE: The Next Accreditation System requires training programs to demonstrate competence among trainees. Within gastroenterology (GI), there are limited data describing learning curves and structured assessment of competence in esophagogastroduodenoscopy (EGD) and colonoscopy. In this study, the authors aimed to demonstrate the feasibility of a centralized feedback system to assess endoscopy learning curves among GI trainees in EGD and colonoscopy. METHOD: During academic year 2016-2017, the authors performed a prospective multicenter cohort study, inviting participants from multiple GI training programs. Trainee technical and cognitive skills were assessed using a validated competence assessment tool. An integrated, comprehensive data collection and reporting system was created to apply cumulative sum analysis to generate learning curves that were shared with program directors and trainees on a quarterly basis. RESULTS: Out of 183 fellowships invited, 129 trainees from 12 GI fellowships participated, with an overall trainee participation rate of 72.1% (93/129); the highest participation level was among first-year trainees (90.9%; 80/88), and the lowest was among third-year trainees (51.2%; 27/53). In all, 1,385 EGDs and 1,293 colonoscopies were assessed. On aggregate learning curve analysis, third-year trainees achieved competence in overall technical and cognitive skills, while first- and second-year trainees demonstrated the need for ongoing supervision and training in the majority of technical and cognitive skills. CONCLUSIONS: This study demonstrated the feasibility of using a centralized feedback system for the evaluation and documentation of trainee performance in EGD and colonoscopy. Furthermore, third-year trainees achieved competence in both endoscopic procedures, validating the effectiveness of current training programs

Discovery of 1‑[3-(1-Methyl‑1<i>H</i>‑pyrazol-4-yl)-5-oxo‑5<i>H</i>‑benzo[4,5]cyclohepta[1,2‑<i>b</i>]pyridin-7-yl]‑<i>N</i>‑(pyridin-2-ylmethyl)methanesulfonamide (MK-8033): A Specific c‑Met/Ron Dual Kinase Inhibitor with Preferential Affinity for the Activated State of c‑Met

This report documents the first example of a specific inhibitor of protein kinases with preferential binding to the activated kinase conformation: 5<i>H</i>-benzo­[4,5]­cyclohepta­[1,2-<i>b</i>]­pyridin-5-one <b>11r</b> (MK-8033), a dual c-Met/Ron inhibitor under investigation as a treatment for cancer. The design of <b>11r</b> was based on the desire to reduce time-dependent inhibition of CYP3A4 (TDI) by members of this structural class. A novel two-step protocol for the synthesis of benzylic sulfonamides was developed to access <b>11r</b> and analogues. We provide a rationale for the observed selectivity based on X-ray crystallographic evidence and discuss selectivity trends with additional examples. Importantly, <b>11r</b> provides full inhibition of tumor growth in a c-Met amplified (GTL-16) subcutaneous tumor xenograft model and may have an advantage over inactive form kinase inhibitors due to equal potency against a panel of oncogenic activating mutations of c-Met in contrast to c-Met inhibitors without preferential binding to the active kinase conformation