Critical evaluation of different mass transfer equations to model N2O emissions from water resource recovery facilities with diffuse aeration.

N2O measurements by liquid sensors in aerated tanks are an input to gas-liquid mass-transfer models for the prediction of N2O off-gas emissions. The prediction of N2O emissions from Water Resource Recovery Facilities (WRRFs) was evaluated by three different mass-transfer models using Benchmark Simulation Model 1 (BSM1) as a reference model. Inappropriate selection of mass-transfer model may result in miscalculation of carbon footprints based on soluble N2O online measurements. The film theory considers a constant mass-transfer expression, while more complex models suggest that emissions are affected by the aeration type, efficiency, and tank design characteristics. The differences among model predictions were 10-16% at dissolved oxygen (DO) concentration of 0.6 g/m3, when biological N2O production was the highest, while the flux of N2O was 20.0-24 kg N2O-N/d. At lower DO, the nitrification rate was low, while at DO higher than 2 g/m3, the N2O production was reduced leading to higher rates of complete nitrification and a flux of 5 kg N2O-N/d. The differences increased to 14-26% in deeper tanks, due to the pressure assumed in the tanks. The predicted emissions are also affected by the aeration efficiency when KLaN2O depends on the airflow instead of the KLaO2. Increasing the nitrogen loading rate under DO concentration of 0.50-0.65 g/m3 increased the differences in predictions by 10-20% in both alpha 0.6 and 1.2. A sensitivity analysis indicated that the selection of different mass-transfer models did not affect the selection of biochemical parameters for N2O model calibration.

Optimizing the configuration of integrated nutrient and energy recovery treatment trains: A new application of global sensitivity analysis to the generic nutrient recovery model (NRM) library.

This paper describes the use of global sensitivity analysis (GSA) for factor prioritization in nutrient recovery model (NRM) applications. The aim was to select the most important factors influencing important NRM model outputs such as biogas production, digestate composition and pH, ammonium sulfate recovery, struvite production, product purity, particle size and density, air and chemical requirements, scaling potential, among others. Factors considered for GSA involve: 1) input waste stream characteristics, 2) process operational factors, and 3) kinetic parameters incorporated in the NRMs. Linear regression analyses on Monte Carlo simulation outputs were performed, and the impact of the standardized regression coefficients on major performance indicators was evaluated. Finally, based on the results, the paper describes the original use of GSA to obtain insight in complex nutrient recovery systems and to propose an optimal nutrient and energy recovery treatment train configuration that maximizes resource recovery and minimizes energy and chemical requirements.

Compliance with QUOROM and quality of reporting of overlapping meta-analyses on the role of acetylcysteine in the prevention of contrast associated nephropathy: case study.

OBJECTIVE: To appraise multiple systematic reviews on the same clinical topic, focusing on predictors and correlates of quality of reporting of meta-analysis (QUOROM) scores. DESIGN: Case study. SETTING: Reviews providing at least individual quantitative estimates on role of acetylcysteine in the prevention of contrast associated nephropathy. DATA SOURCES: PubMed, the database of abstracts of reviews of effects, and the Cochrane database of systematic reviews (updated March 2005). MAIN OUTCOME MEASURES: Funding, compliance with the QUOROM checklist, scores on the Oxman and Guyatt quality index, and authors' recommendations. RESULTS: 10 systematic reviews, published August 2003 to March 2005, were included. Nine pooled events despite heterogeneity and five recommended routine use of acetylcysteine, whereas the remaining studies called for further research. Compliance with the 18 items on the QUOROM checklist was relatively high (median 16, range 11 to 17), although shorter manuscripts had significantly lower scores (R = 0.73; P = 0.016). Reviewers who reported previous not for profit funding were more likely to score higher on the Oxman and Guyatt quality index. No association was found between QUOROM and Oxman and Guyatt scores (R = -0.06; P = 0.86), mainly because of greater emphasis of the Oxman and Guyatt scores on the appraisal of bias in selection and validity assessment (inadequate in five reviews). CONCLUSIONS: Multiple systematic reviews on the same clinical topic varied in quality of reporting and recommendations. Longer manuscripts and previous not for profit funding were associated with higher quality.

Incidence, predictors, and outcomes of coronary dissections left untreated after drug-eluting stent implantation.

AIMS: Coronary dissections left untreated after percutaneous coronary intervention are associated with unfavourable outcomes. However, their role after drug-eluting stent (DES) implantation is still undescribed. We assessed incidence, predictors, and outcomes of residual dissections in DES-treated lesions. METHODS AND RESULTS: Consecutive patients undergoing DES implantation were enrolled in four Italian centres, with baseline, procedural, and outcome data entered into a dedicated database. Residual dissections were classified according to the National Heart Lung and Blood Institute criteria. End-points of interest were in-hospital, 1-month, and 6-month major adverse cardiovascular events (MACE, i.e. death, myocardial infarction, or target vessel revascularization), and stent thrombosis (ST). Among the 2418 included patients (4630 lesions), a total of 77 (1.7%) final dissections occurred in 67 (2.8%) subjects. Dissections were more frequent in longer and complex lesions and in the left anterior descending, and were associated with increased rates of in-hospital (11.9 vs. 5.2%, P=0.017) and 1-month MACE (13.4 vs. 6.0%, P=0.013), with similar 6-month trends. Cumulative ST was also greater in patients with dissections (6.3 vs. 1.3%, P=0.011). Even non-obstructive dissections with thrombolysis in myocardial infarction 3 flow conferred a significantly worse prognosis. CONCLUSION: This study, reporting for the first time on incidence, predictors, and outcomes of residual dissections in DES-treated coronary lesions, demonstrates their adverse clinical impact and supports the pursuit of a strategy of sealing dissection flaps with other DES.

Validation of predictors of intraprocedural stent thrombosis in the drug-eluting stent era.

Although predictors of acute intraprocedural stent thrombosis (IPST) in the drug-eluting stent era have been proposed, external validation is lacking. We thus analyzed the occurrence of IPST in the RECIPE study and found that, among 1,320 patients who underwent drug-eluting stent implantation, IPST occurred in 6 (0.5%), with in-hospital major adverse events in 4 (67%). IPST was predicted by number and total length of implanted stents, baseline minimal lumen diameter, and, in a pooled analysis that incorporated values from the present study and a previous study, use of elective glycoprotein IIb/IIIa inhibitors. Such results may provide useful information to guide prevention of this complication.