Response to comment on "solid recovered fuel: Materials flow analysis and fuel property development during the mechanical processing of biodried waste"

Laner and Cencic1 comment on Velis et al. (2013)2 clarifying certain points on the use of the material flow analysis (MFA) software STAN3. We welcome the correspondence and the opportunity this exchange provides to discuss optimal approaches to using STAN. In keeping with Velis et al.2 these physically impossible, and otherwise insignificant, negative flows have enabled improvements to STAN. Here, we elaborate on the practicalities of using STAN in our research and on the correctness and validation of our results, notwithstanding the inclusion of negative flows. We explain the contribution of our approach to solid waste management and resource recovery

The Atacama Cosmology Telescope: Data Characterization and Map Making

We present a description of the data reduction and mapmaking pipeline used for the 2008 observing season of the Atacama Cosmology Telescope (ACT). The data presented here at 148 GHz represent 12% of the 90 TB collected by ACT from 2007 to 2010. In 2008 we observed for 136 days, producing a total of 1423 hours of data (11 TB for the 148 GHz band only), with a daily average of 10.5 hours of observation. From these, 1085 hours were devoted to a 850 deg^2 stripe (11.2 hours by 9.1 deg) centered on a declination of -52.7 deg, while 175 hours were devoted to a 280 deg^2 stripe (4.5 hours by 4.8 deg) centered at the celestial equator. We discuss sources of statistical and systematic noise, calibration, telescope pointing, and data selection. Out of 1260 survey hours and 1024 detectors per array, 816 hours and 593 effective detectors remain after data selection for this frequency band, yielding a 38% survey efficiency. The total sensitivity in 2008, determined from the noise level between 5 Hz and 20 Hz in the time-ordered data stream (TOD), is 32 micro-Kelvin sqrt{s} in CMB units. Atmospheric brightness fluctuations constitute the main contaminant in the data and dominate the detector noise covariance at low frequencies in the TOD. The maps were made by solving the least-squares problem using the Preconditioned Conjugate Gradient method, incorporating the details of the detector and noise correlations. Cross-correlation with WMAP sky maps, as well as analysis from simulations, reveal that our maps are unbiased at multipoles ell > 300. This paper accompanies the public release of the 148 GHz southern stripe maps from 2008. The techniques described here will be applied to future maps and data releases.Comment: 20 pages, 18 figures, 6 tables, an ACT Collaboration pape

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme

The association between increasing maternal age at first birth and decreased rates of spontaneous vaginal birth in South Australia from 1991 to 2009

Background Caesarean section rates in Australia rose over the period 1999-2009, as did maternal age at first birth. The contribution of the rise of maternal age to the rise in caesarean sections remains unclear. Aims To estimate the effect of increasing maternal age on the incidence of emergency caesarean section or instrumental delivery in term singleton first births in South Australia. Methods We undertook a population-based study of 117 981 term singleton first births, which followed labour during the period 1991-2009, using data from the South Australian Perinatal Statistics Collection. The main outcome measures were deliveries other than spontaneous vaginal births (SVB) (emergency caesarean section or instrumental birth) and emergency caesarean section alone. Logistic regression analysis was performed. Results Increasing maternal age at first birth was found to be associated with delivery other than SVB and emergency caesarean section. The adjusted odds of delivery other than SVB increased multiplicatively by approximately 1.49 (95% CI, 1.47-1.51) per five-year rise in maternal age, and the odds of emergency caesarean section increased multiplicatively by approximately 1.39 (95% CI, 1.37-1.42) per five-year rise. Although there are likely to be many reasons for the effect, increases in maternal age at first birth made a contribution in up to 75% of the observed increase in delivery other than SVB from 44.0% to 49.6% over the study period. Conclusions Rising maternal age at first birth appeared to contribute to a large proportion of the increase in deliveries other than SVB in South Australia

The association between increasing maternal age at first birth and decreased rates of spontaneous vaginal birth in South Australia from 1991 to 2009

Background: Caesarean section rates in Australia rose over the period 1999–2009, as did maternal age at first birth. The contribution of the rise of maternal age to the rise in caesarean sections remains unclear. Aims: To estimate the effect of increasing maternal age on the incidence of emergency caesarean section or instrumental delivery in term singleton first births in South Australia. Methods: We undertook a population‐based study of 117 981 term singleton first births, which followed labour during the period 1991–2009, using data from the South Australian Perinatal Statistics Collection. The main outcome measures were deliveries other than spontaneous vaginal births (SVB) (emergency caesarean section or instrumental birth) and emergency caesarean section alone. Logistic regression analysis was performed. Results: Increasing maternal age at first birth was found to be associated with delivery other than SVB and emergency caesarean section. The adjusted odds of delivery other than SVB increased multiplicatively by approximately 1.49 (95% CI, 1.47–1.51) per five‐year rise in maternal age, and the odds of emergency caesarean section increased multiplicatively by approximately 1.39 (95% CI, 1.37–1.42) per five‐year rise. Although there are likely to be many reasons for the effect, increases in maternal age at first birth made a contribution in up to 75% of the observed increase in delivery other than SVB from 44.0% to 49.6% over the study period. Conclusions: Rising maternal age at first birth appeared to contribute to a large proportion of the increase in deliveries other than SVB in South Australia

Solid Recovered Fuel: Influence of Waste Stream Composition and Processing on Chlorine Content and Fuel Quality

Solid recovered fuel (SRF) produced by mechanical–biological treatment (MBT) of municipal waste can replace fossil fuels, being a CO₂-neutral, affordable, and alternative energy source. SRF application is limited by low confidence in quality. We present results for key SRF properties centered on the issue of chlorine content. A detailed investigation involved sampling, statistical analysis, reconstruction of composition, and modeling of SRF properties. The total chlorine median for a typical plant during summer operation was 0.69% w/w_d, with lower/upper 95% confidence intervals of 0.60% w/w_d and 0.74% w/w_d (class 3 of CEN Cl indicator). The average total chlorine can be simulated, using a reconciled SRF composition before shredding to <40 mm. The relative plastics vs paper mass ratios in particular result in an SRF with a 95% upper confidence limit for ash content marginally below the 20% w/w_d deemed suitable for certain power plants; and a lower 95% confidence limit of net calorific value (NCV) at 14.5 MJ kg_ar^–1. The data provide, for the first time, a high level of confidence on the effects of SRF composition on its chlorine content, illustrating interrelationships with other fuel properties. The findings presented here allow rational debate on achievable vs desirable MBT-derived SRF quality, informing the development of realistic SRF quality specifications, through modeling exercises, needed for effective thermal recovery

Solid Recovered Fuel: Materials Flow Analysis and Fuel Property Development during the Mechanical Processing of Biodried Waste

Material flows and their contributions to fuel properties are balanced for the mechanical section of a mechanical–biological treatment (MBT) plant producing solid recovered fuel (SRF) for the UK market. Insights for this and similar plants were secured through a program of sampling, manual sorting, statistics, analytical property determination, and material flow analysis (MFA) with error propagation and data reconciliation. Approximately three-quarters of the net calorific value (Q_net,p,ar) present in the combustible fraction of the biodried flow is incorporated into the SRF (73.2 ± 8.6%), with the important contributors being plastic film (30.7 MJ kg_ar^–1), other packaging plastic (26.1 MJ kg_ar^–1), and paper/card (13.0 MJ kg_ar^–1). Nearly 80% w/w of the chlorine load in the biodried flow is incorporated into SRF (78.9 ± 26.2%), determined by the operation of the trommel and air classifier. Through the use of a novel mass balancing procedure, SRF quality is understood, thus improving on the understanding of quality assurance in SRF. Quantification of flows, transfer coefficients, and fuel properties allows recommendations to be made for process optimization and the production of a reliable and therefore marketable SRF product