Toxic Substance Contamination: The Risk-Benefit Approach to Causation Analysis

This article argues that the dilemma described above requires change and proposes a new standard for causation in this type of toxic contamination case. Part I examines the difficulties posed by conventional common law relief mechanisms, and the inadequacies of existing statutory relief mechanisms. Part II scrutinizes a more lenient burden of proof standard, the risk-benefit approach, which some courts have applied when faced with situations involving scientific uncertainties. The risk-benefit approach will be applied to causation analysis in the context of damage recoveries, using the. Hemlock, Michigan, situation as a case study. Part III discusses present congressional proposals, and compares the economic efficiencies of such legislative action with those of a judicially implemented relaxation of causation requirements. This article concludes that relaxation of causation requirements through the adoption of the risk-benefit approach is a response the judicial system can and should make in cases involving scientific uncertainty

Laboratory and intra-oral tests of the degradation of elastic chains

Two brands of elastic chain, Alastic (Unitek Co.) and Power Chain II (Ormco Co.), were tested for force development in laboratory and intra-oral experiments. During the laboratory test, the chains were extended to 180 and 215 per cent of their original passive length and the force exerted at this length was measured at the start and after 15 minutes, 2, 8 and 24 hours, 3 days and 1, 2, 3 and 4 weeks of continuous extension. The two brands behaved similarly. After 4 weeks, they had lost 25-30 per cent of their initial force. The decrease of the force value was greatest in the beginning of the test period, with a decline of 6-11 per cent during the first 15 minutes and 10-16 per cent during the first 2 hours. The intra-oral tests were performed in 10-25 subjects, who wore the elastic chains continuously for up to 4 weeks. The chains were extended up to 200 per cent of their original passive length. In one test, the force development was measured at the start and after 8 and 24 hours, 5 days and 1, 2, 3 and 4 weeks. In two other tests the force was measured after 1 day and 4 weeks, respectively. The two brands behaved similarly. The decline of the force value during intra-oral use was greater than in the laboratory tests. After 4 weeks, the force was only 43-52 per cent of the original value. The decline was greatest in the initial phase after insertion; after 8 hours the force had declined by 28-34 per cent. Thus, an initial force of 300g was reduced to 200g after 8 hours and to less than 150g after 4 weeks: in no specimen was the force after 4 weeks less than 100

Spatial and temporal variablity of nonmethane hydrocarbon mixing ratios and their relation to photochemical lifetime

The relationship between temporal and spatial variability of C2-C8 nonmethane hydrocarbon mixing ratios and their HO lifetimes (τ) is presented for samples collected during the 1993 North Atlantic Regional Experiment (NARE) and from other urban and remote sites. The C2-C4 alkanes, acetylene and benzene typically define a trend of the form slnx=Aτ-b where slnx is the standard deviation of the ln of the mixing ratio. The relationship extended over a wider range of hydrocarbons in winter. The exponent b ranged in value from 0.2±0.023 for winter urban data where C2-C8 hydrocarbons defined a strongly correlated trend, to 0.56±0.15 for C2-C4 hydrocarbons at a coastal site in Nova Scotia during NARE. The trends are significantly different from that given by the Junge relationship [Junge, 1974]. Data from the Azores do not display such a trend and were likely influenced by local emissions. Variance trends are a useful analytical tool for examining the validity of hydrocarbon measurements

Validation of Geant4-based Radioactive Decay Simulation

Radioactive decays are of concern in a wide variety of applications using Monte-Carlo simulations. In order to properly estimate the quality of such simulations, knowledge of the accuracy of the decay simulation is required. We present a validation of the original Geant4 Radioactive Decay Module, which uses a per-decay sampling approach, and of an extended package for Geant4-based simulation of radioactive decays, which, in addition to being able to use a refactored per-decay sampling, is capable of using a statistical sampling approach. The validation is based on measurements of calibration isotope sources using a high purity Germanium (HPGe) detector; no calibration of the simulation is performed. For the considered validation experiment equivalent simulation accuracy can be achieved with per-decay and statistical sampling

Radioactive Decays in Geant4

The simulation of radioactive decays is a common task in Monte-Carlo systems such as Geant4. Usually, a system either uses an approach focusing on the simulations of every individual decay or an approach which simulates a large number of decays with a focus on correct overall statistics. The radioactive decay package presented in this work permits, for the first time, the use of both methods within the same simulation framework - Geant4. The accuracy of the statistical approach in our new package, RDM-extended, and that of the existing Geant4 per-decay implementation (original RDM), which has also been refactored, are verified against the ENSDF database. The new verified package is beneficial for a wide range of experimental scenarios, as it enables researchers to choose the most appropriate approach for their Geant4-based application

Probing the outer edge of an accretion disk : a Her X-1 turn-on observed with RXTE

We present the analysis of Rossi X-ray Timing Explorer (RXTE) observations of the turn-on phase of a 35 day cycle of the X-ray binary Her X-1. During the early phases of the turn-on, the energy spectrum is composed of X-rays scattered into the line of sight plus heavily absorbed X-rays. The energy spectra in the 3–17 keV range can be described by a partial covering model, where one of the components is influenced by photoelectric absorption and Thomson scattering in cold material plus an iron emission line at 6.5 keV. In this paper we show the evolution of spectral parameters as well as the evolution of the pulse profile during the turn-on. We describe this evolution using Monte Carlo simulations which self-consistently describe the evolution of the X-ray pulse profile and of the energy spectrum

Documentation of adherence to infection prevention best practice in patient records: a mixed-methods investigation.

BACKGROUND Healthcare-associated infections remain a preventable cause of patient harm in healthcare. Full documentation of adherence to evidence-based best practices for each patient can support monitoring and promotion of infection prevention measures. Thus, we reviewed the extent, nature, and determinants of the documentation of infection prevention (IP) standards in patients with HAI. METHODS We reviewed electronic patient records (EMRs) of patients included in four annual point-prevalence studies 2013-2016 who developed a device- or procedure-related HAI (surgical site infection (SSI), catheter-associated urinary tract infection (CAUTI), ventilator-associated infection (VAP), catheter-related bloodstream infection (CRBSI)). We examined the documentation quality of mandatory preventive measures published as institutional IP standards. Additionally, we undertook semi-structured interviews with healthcare providers and a two-step inductive (grounded theory) and deductive (Theory of Planned Behaviour) content analysis. RESULTS Of overall 2972 surveyed patients, 249 (8.4%) patients developed 272 healthcare-associated infections. Of these, 116 patients met the inclusion criteria, classified as patients with SSI, CAUTI, VAP, CRBSI in 78 (67%), 21 (18%), 10 (9%), 7 (6%), cases, respectively. We found documentation of IP measures in EMRs in 432/1308 (33%) cases. Documentation of execution existed in the study patients' EMRs for SSI, CAUTI, VAP, CRBSI, and overall, in 261/931 (28%), 27/104 (26%), 46/122 (38%), 26/151 (17%), and 360/1308 (28%) cases, respectively, and documentation of non-execution in 67/931 (7%), 2/104 (2%), 0/122 (0%), 3/151 (2%), and 72/1308 (6%) cases, respectively. Healthcare provider attitudes, subjective norms, and perceived behavioural control indicated reluctance to document IP standards. CONCLUSIONS EMRs rarely included conclusive data about adherence to IP standards. Documentation had to be established indirectly through data captured for other reasons. Mandatory institutional documentation protocols or technically automated documentation may be necessary to address such shortcomings in patient safety documentation

Ground-based intercomparison of two isoprene measurement techniques

International audienceAn informal intercomparison of two isoprene (C5H8) measurement techniques was carried out during Fall of 1998 at a field site located approximately 3 km west of Boulder, Colorado, USA. A new chemical ionization mass spectrometric technique (CIMS) was compared to a well-established gas chromatographic technique (GC). The CIMS technique utilized benzene cation chemistry to ionize isoprene. The isoprene levels measured by the CIMS were often larger than those obtained with the GC. The results indicate that the CIMS technique suffered from an anthropogenic interference associated with air masses from the Denver, CO metropolitan area as well as an additional interference occurring in clean conditions. However, the CIMS technique is also demonstrated to be sensitive and fast. Especially after introduction of a tandem mass spectrometric technique, it is therefore a candidate for isoprene measurements in remote environments near isoprene sources