The empirical accuracy of uncertain inference models

Uncertainty is a pervasive feature of the domains in which expert systems are designed to function. Research design to test uncertain inference methods for accuracy and robustness, in accordance with standard engineering practice is reviewed. Several studies were conducted to assess how well various methods perform on problems constructed so that correct answers are known, and to find out what underlying features of a problem cause strong or weak performance. For each method studied, situations were identified in which performance deteriorates dramatically. Over a broad range of problems, some well known methods do only about as well as a simple linear regression model, and often much worse than a simple independence probability model. The results indicate that some commercially available expert system shells should be used with caution, because the uncertain inference models that they implement can yield rather inaccurate results

Fully-Coupled Simulation of Cosmic Reionization. I: Numerical Methods and Tests

We describe an extension of the Enzo code to enable fully-coupled radiation hydrodynamical simulation of inhomogeneous reionization in large $\sim (100 Mpc)^3$ cosmological volumes with thousands to millions of point sources. We solve all dynamical, radiative transfer, thermal, and ionization processes self-consistently on the same mesh, as opposed to a postprocessing approach which coarse-grains the radiative transfer. We do, however, employ a simple subgrid model for star formation which we calibrate to observations. Radiation transport is done in the grey flux-limited diffusion (FLD) approximation, which is solved by implicit time integration split off from the gas energy and ionization equations, which are solved separately. This results in a faster and more robust scheme for cosmological applications compared to the earlier method. The FLD equation is solved using the hypre optimally scalable geometric multigrid solver from LLNL. By treating the ionizing radiation as a grid field as opposed to rays, our method is scalable with respect to the number of ionizing sources, limited only by the parallel scaling properties of the radiation solver. We test the speed and accuracy of our approach on a number of standard verification and validation tests. We show by direct comparison with Enzo's adaptive ray tracing method Moray that the well-known inability of FLD to cast a shadow behind opaque clouds has a minor effect on the evolution of ionized volume and mass fractions in a reionization simulation validation test. We illustrate an application of our method to the problem of inhomogeneous reionization in a 80 Mpc comoving box resolved with $3200^3$ Eulerian grid cells and dark matter particles.Comment: 32 pages, 23 figures. ApJ Supp accepted. New title and substantial revisions re. v

The future of North American trade policy: lessons from NAFTA

This repository item contains a single issue of the Pardee Center Task Force Reports, a publication series that began publishing in 2009 by the Boston University Frederick S. Pardee Center for the Study of the Longer-Range Future.This Task Force Report written by an international group of trade policy experts calls for significant reforms to address adverse economic, environmental, labor and societal impacts created by the 1994 North American Free Trade Agreement (NAFTA). The report is intended to contribute to the discussion and decisions stemming from ongoing reviews of proposed reforms to NAFTA as well as to help shape future trade agreements. It offers detailed proposals on topics including services, manufacturing, agriculture, investment, intellectual property, labor, environment, and migration. Fifteen years after NAFTA was enacted, there is widespread agreement that the trade treaty among the United States, Canada and Mexico has fallen short of its stated goals. While proponents credit the agreement with stimulating the flow of goods, services, and investment among the North American countries, critics in all three countries argue that this has not brought improvements in the standards of living of most people. Rather than triggering a convergence across the three nations, NAFTA has accentuated the economic and regulatory asymmetries that had existed among the three countries. [TRUNCATED

Impact of blood group on survival following critical illness: a single-centre retrospective observational study

Background Predicting patient outcomes following critical illness is challenging. Recent evidence has suggested that patients with blood group AB are more likely to survive following major cardiac surgery, and this is associated with a reduced number of blood transfusions. However, there are no current data to indicate whether a patient’s blood group affects general intensive care outcomes. Objective The objective of this study was to determine if ABO blood group affects survival in intensive care. The primary outcome measure was 90-day mortality with a secondary outcome measure of the percentage of patients receiving a blood transfusion. Design Retrospective analysis of electronically collected intensive care data, blood group and transfusion data. Setting General intensive care unit (ICU) of a major tertiary hospital with both medical and surgical patients. Patients All patients admitted to ICU between 2006 and 2016 who had blood group data available. Intervention None. Measurements and main results 7340 patients were included in the study, blood group AB accounted for 3% (221), A 41% (3008), B 10.6% (775) and O 45.4% (3336). These values are similar to UK averages. Baseline characteristics between the groups were similar. Blood group AB had the greatest survival benefit (blood group AB 90-day survival estimate 76.75, 95% CI 72.89 to 80.61 with the overall estimate 72.07, 95% CI 71.31 to 72.82) (log-rank χ2 16.128, p=0.001). Transfusion requirements were similar in all groups with no significant difference between the percentages of patients transfused (AB 23.1%, A 21.5%, B 18.7%, O 19.9%, Pearson χ2 5.060 p=0.167). Conclusion Although this is primarily a hypothesis generating study, intensive care patients with blood group AB appeared to have a higher 90-day survival compared with other blood groups. There was no correlation between blood group and percentage of patients receiving transfusion

Heart rate variability predicts 30-day all-cause mortality in intensive care units

Background: Autonomic nervous function, as quantified by heart rate variability (HRV), has shown promise in predicting clinically important outcomes in the critical care setting; however, there is debate concerning its utility. HRV analysis was assessed as a practical tool for outcome prediction in two South African hospitals and compared with Acute Physiology and Chronic Health Evaluation II (APACHE II) scoring.Method: In a dual centre, prospective, observational cohort study of patients admitted to the intensive care units (ICU) of two hospitals in KwaZulu-Natal, South Africa frequency domain HRV parameters were explored as predictors of: all-cause mortality at 30 days after admission; ICU stay duration; the need for invasive ventilation; the need for inotrope/vasopressor therapy; and the need for renal replacement therapy. The predictive ability of HRV parameters against the APACHE II score for the study outcomes was also compared.Results: A total of 55 patients were included in the study. Very low frequency power (VLF) was shown to predict 30-day mortality in ICU (odds ratio 0.6; 95% confidence interval 0.396–0.911). When compared with APACHE II, VLF remained a significant predictor of outcome, suggesting that it adds a unique component of prediction. No HRV parameters were predictive for the other secondary outcomes.Conclusion: This study found that VLF independently predicted all-cause mortality at 30 days after ICU admission. VLF provided additional predictive ability above that of the APACHE II score. As suggested by this exploratory analysis larger multi-centre studies seem warranted.Keywords: APACHE II, autonomic nervous system, critical care, heart rate variability, mortalit

Discordance in investigator-reported and adjudicated sudden death in TIOSPIR

Accurate and consistent determination of cause of death is challenging in chronic obstructive pulmonary disease (COPD) patients. TIOSPIR (N=17 135) compared the safety and efficacy of tiotropium Respimat 5/2.5 µg with HandiHaler 18 µg in COPD patients. All-cause mortality was a primary end-point. A mortality adjudication committee (MAC) assessed all deaths. We aimed to investigate causes of discordance in investigator-reported and MAC-adjudicated causes of death and their impact on results, especially cardiac and sudden death. The MAC provided independent, blinded assessment of investigator-reported deaths (n=1302) and assigned underlying cause of death. Discordance between causes of death was assessed descriptively (shift tables). There was agreement between investigator-reported and MAC-adjudicated deaths in 69.4% of cases at the system organ class level. Differences were mainly observed for cardiac deaths (16.4% investigator, 5.1% MAC) and deaths assigned to general disorders including sudden death (17.4% investigator, 24.6% MAC). Reasons for discrepancies included investigator attribution to the immediate (e.g. myocardial infarction (MI)) over the underlying cause of death (e.g. COPD) and insufficient information for a definitive cause. Cause-specific mortality varies in COPD, depending on the method of assignment. Sudden death, witnessed and unwitnessed, is common in COPD and often attributed to MI without supporting evidence