Incompressible viscous flow near the leading edge of a flat plate admitting slip

The shear stress at the leading edge, calculated on basis of the Navier-Stokes equations and the no-slip boundary condition, approaches infinity. However, taking into account the mean free path of the molecules, which implies admitting a certain slip, the shear stress becomes inversely proportional to the square root of the Knudsen number κ if κ→0. κ is defined as the ratio between the mean free path and the viscous length. The new boundary condition modifies the shear stress only within the Knudsen region of which the size is of the order of 3 to 4 times the mean free path.

The K-12 Online Teaching Dynamic: A Study of Educators at Multiple Cyber Charter Schools in Pennsylvania

This study harvested and synthesized information on K-12 online educators within the State of Pennsylvania through structured interviews and artifact evaluations. As parents, students, and the greater K-12 educational community look for innovative ways to increase rigor and student achievement in the 21st century, educational technology is viewed as the conduit to that end. Using a multi-site case study approach, comprehensive research brought to the surface a profile of effective K-12 online educators teaching at various Pennsylvania cyber charter schools. This study sought to answer the following questions: What are the characteristics and competencies of effective K-12 online educators in Pennsylvania cyber charter schools? What evidence displays skills that are specific to effective K-12 online educators in Pennsylvania? These educators rely on their skills acquired during traditional pre-service training to teach in an online environment. Study participants stated they require skills that go above and beyond traditional knowledge, skills collectively known as digital pedagogy. In the 21st century, digital pedagogy skills are moving to the forefront of teacher usage and knowledge base. This is evidenced from the study participants' statements and the adoption of online teacher certification and credentialing by state departments of education.Ed.D., Educational Leadership and Management -- Drexel University, 201

Treatment of ink-containing wastewater by coagulation/flocculation using biopolymers

A coagulation/flocculation process using a selection of biopolymers (chitosan and tannin) was used to treat an ink-containing effluent generated in the processing of packaging. The efficiency of the process was investigated in terms of the influence of pH, coagulant and flocculant concentrations, as well as chitosan characteristics (especially the molecular weight). The process was particularly efficient under acidic solutions: the amount of coagulant and flocculant to be used were significantly reduced by limiting the pH to 5. Optimum conditions for colour abatement (measured at 528 nm) were obtained at pH 5 using the most viscous chitosan (highest molecular weight) at a concentration close to 20 mg·ℓ-1 and a concentration of tannin close to 70-100 mg·ℓ-1.. Water SA Vol.31 (3) 2005: pp.369-37

Transforming towards sustainable health and wellbeing systems:Eight guiding principles based on the experiences of nine Dutch Population Health Management initiatives

Introduction Population Health Management initiatives are increasingly introduced, aiming to develop towards sustainable health and wellbeing systems. Yet, little is known about which strategies to implement during this development. This study provides insights into which strategies are used, why, and when, based on the experiences of nine Dutch Population Health Management initiatives. Methods The realist evaluation approach was used to gain an understanding of the relationships between context, mechanisms and outcomes when Population Health Management strategies were implemented. Data were retrieved from three interview rounds (n = 207) in 2014, 2016 and 2017. Data was clustered into guiding principles, underpinned with strategy-context-mechanism-outcome configurations. Results The Dutch initiatives experienced different developments, varying between immediate large-scale collaborations with eventual relapse, and incremental growth towards cross-sector collaboration. Eight guiding principles for development towards health and wellbeing systems were identified, focusing on: 1. Shared commitment for a Population Health Management-vision; 2. Mutual understanding and trust; 3. Accountability; 4. Aligning politics and policy; 5. Financial incentives; 6. A learning cycle based on a data-infrastructure; 7. Community input and involvement; and 8. Stakeholder representation and leadership. Conclusion Development towards a sustainable health and wellbeing system is complex and time-consuming. Its success not only depends on the implementation of all eight guiding principles, but is also influenced by applying the right strategies at the right moment in the development

What’s in a Realist Configuration? Deciding Which Causal Configurations to Use, How, and Why

Background: Realist studies represent an increasingly popular approach for exploring complex interventions’ successes and failures. The theory-driven approach seeks to explain “what works, how, why, in which contexts, for whom, and to what extent” using context–mechanism–outcome (CMO) configurations. When the approach was first developed, CMO configurations were the method for expressing causal explanations. Increasingly, realist studies have been conducted using different variations of the heuristic such as strategy–context–mechanism–outcome (SCMO) configurations or intervention–context–actor–mechanism–outcome (ICAMO) configurations. Researchers have highlighted a lack of methodological guidance regarding which additional explanatory factors can be included in configurations (e.g., strategies, interventions, actors). This article aims to clarify and further develop the concept of configurations by discussing how explanatory factors could be robustly added to the original CMO configuration as put forward by Pawson and Tilley. Comparing the use of different types of configurations: We draw on two of our own studies, one which formulated CMO configurations and one which formulated SCMO configurations, and on an evidence scan of realist studies. We explored the effects these different configurations had on studies’ findings and highlight why researchers chose CMOs or SCMOs. Finally, we provide recommendations regarding the use of configurations. These are as follows: Using additional explanatory factors is possible but consider the research scope to select the configuration appropriate for the study; Be transparent about the choice in configuration and include examples of configurations; Further studies about the use of additional explanatory factors are needed to better understand the effects on each step in the realist evaluation cycle; and New ways of disseminating realist findings are needed to balance transparency regarding the use of configurations. Conclusions: Adding explanatory factors is possible and can be insightful depending on the study’s scope and aims; however, any configuration type must adhere to the rule of generative causation

Saturable elimination of piperacillin in critically ill patients:implications for continuous infusion

The study aimed to evaluate saturation of piperacillin elimination in critically ill adult patients. Seventeen critically ill adult patients received continuous and intermittent infusion of piperacillin/tazobactam. Piperacillin plasma concentrations (n = 217) were analysed using population pharmacokinetic (PopPK) modelling. Post-hoc simulations were performed to evaluate the type I error rate associated with the study. Unseen data were used to validate the final model. The mean error (ME) and root mean square error (RMSE) were calculated as a measure of bias and imprecision, respectively. A PopPK model with parallel linear and non-linear elimination best fitted the data. The median and 95% confidence interval (CI) for the model parameters drug clearance (CL), volume of central compartment (V), volume of peripheral compartment (V-p) and intercompartmental clearance (Q) were 9 (7.69-11) L/h, 6.18 (4.93-11.2) L, 11.17 (7.26-12) L and 15.61 (12.66-23.8) L/h, respectively. The Michaelis-Menten constant (K-m) and the maximum elimination rate for Michaelis-Menten elimination (V-max) were estimated without population variability in the model to avoid overfitting and inflation of the type I error rate. The population estimates for K-m and V-max were 37.09 mg/L and 353.57 mg/h, respectively. The bias (ME) was -20.8 (95% CI -26.2 to -15.4) mg/L, whilst imprecision (RMSE) was 49.2 (95% CI 41.2-56) mg/L. In conclusion, piperacillin elimination is (partially) saturable. Moreover, the population estimate for K-m lies within the therapeutic window and therefore saturation of elimination should be accounted for when defining optimum dosing regimens for piperacillin in critically ill patients. (C) 2019 Elsevier B.V. and International Society of Chemotherapy. All rights reserved

Negative calcium balance despite normal plasma ionized calcium concentrations during citrate anticoagulated continuous venovenous hemofiltration (CVVH) in ICU patients

Background: Supplementation of calcium during continuous venovenous hemofiltration (CVVH) with citrate anticoagulation is usually titrated using a target blood ionized calcium concentration. Plasma calcium concentrations may be normal despite substantial calcium loss, by mobilization of calcium from the skeleton. Aim of our study is to develop an equation to calculate CVVH calcium and to retrospectively calculate CVVH calcium balance in a cohort of ICU-patients. Methods: This is a single-center retrospective observational cohort study. In a subcohort of patients, all calcium excretion measurements in patients treated with citrate CVVH were randomly divided into a development set (n = 324 in 42 patients) and a validation set (n = 441 in 42 different patients). Using mixed linear models, we developed an equation to calculate calcium excretion from routinely available parameters. We retrospectively calculated calcium balance in 788 patients treated with citrate CVVH between 2014 and 2021. Results: Calcium excretion (mmol/24 h) was - 1.2877 + 0.646*[Ca](blood,total) * ultrafiltrate (l/24 h) + 0.107*blood flow (ml/h). The mean error of the estimation was - 1.0 +/- 6.7 mmol/24 h, the mean absolute error was 4.8 +/- 4.8 mmol/24 h. Calculated calcium excretion was 105.8 +/- 19.3 mmol/24 h. Mean daily CVVH calcium balance was - 12.0 +/- 20.0 mmol/24 h. Mean cumulative calcium balance ranged from - 3687 to 448 mmol. Conclusion: During citrate CVVH, calcium balance was negative in most patients, despite supplementation of calcium based on plasma ionized calcium levels. This may contribute to demineralization of the skeleton. We propose that calcium supplementation should be based on both plasma ionized calcium and a simple calculation of calcium excretion by CVVH.[GRAPHICS].Afdeling Klinische Chemie en Laboratoriumgeneeskunde (AKCL