Integrating the theory of sampling into a nuclear forensic investigation.

We present a study case where the theory of sampling (TOS) is used to make defensible inferences in a nuclear forensic investigation. The forensic investigations focused on five suspicious radioactive materials seized in 2019. All errors introduced by sampling and sub-sampling the radioactive materials are evaluated according to TOS. A maximum sampling error of 35% was tolerated. The uses of TOS enabled the forensic team to make inferences about the seized materials and therefore make confidence-based statements about the exceeding of limits established in the Swiss Radiological Protection Ordinance for radioactive substances. The analysis of the isotope and activity ratios allowed the team to exclude some potential sources of the radioactive contamination; however, it was not possible to determine its origin precisely.

Assessment of residual radionuclide levels at the Bokak and Bikar Atolls in the northern Marshall Islands.

The Bikar and Bokak Atolls, located in the northern Marshall Islands, are extremely isolated and consist of pristine marine and terrestrial ecosystems. Both atolls may have experienced significant radioactive deposition following the nuclear weapon testing conducted at Bikini and Enewetak proving grounds. Here we report activity concentrations of artificial radionuclides (239Pu, 240Pu, 241Pu, 241Am, 137Cs and 90Sr) in marine and terrestrial samples collected from Bikar and Bokak Atolls. Artificial radionuclides in soil from the Majuro Atoll are also reported and form a radiological baseline against which the levels at the other atolls can be compared. We observed low levels of artificial radionuclides in soil from Majuro and Bokak, but significantly higher levels in soil from Bikar. The residual radioactivity in the Bikar environment is comparable to the levels previously reported for other nearby atolls, including Taka and Utrik, but lower than for Rongerik, Rongelap, Bikini and Enewetak. An analysis of 240Pu/239Pu isotope ratios and estimations of the dates of contamination from 241Am/241Pu activity ratios both indicated that the Bikar Atoll was contaminated mainly by radioactive fallout from the Castle Bravo test in 1954. We compare the results of our measurements at Bikar and Bokak to data from other atolls in the Marshall Islands and to regions of the world affected by both global and regional fallout from atmospheric nuclear weapons testing and nuclear accidents.

Scale-up of phosphate remobilization from sewage sludge in a microbial fuel cell.

Phosphate remobilization from digested sewage sludge containing iron phosphate was scaled-up in a microbial fuel cell (MFC). A 3litre triple chambered MFC was constructed. This reactor was operated as a microbial fuel cell and later as a microbial electrolysis cell to accelerate cathodic phosphate remobilization. Applying an additional voltage and exceeding native MFC power accelerated chemical base formation and the related phosphate remobilization rate. The electrolysis approach was extended using a platinum-RVC cathode. The pH rose to 12.6 and phosphate was recovered by 67% in 26h. This was significantly faster than using microbial fuel cell conditions. Shrinking core modelling particle fluid kinetics showed that the reaction resistance has to move inside the sewage sludge particle for considerable rate enhancement. Remobilized phosphate was subsequently precipitated as struvite and inductively coupled plasma mass spectrometry indicated low levels of cadmium, lead, and other metals as required by law for recycling fertilizers.

A pretest prognostic score to assess patients undergoing exercise or pharmacological stress testing.

OBJECTIVE: A previously developed pretest score was validated to stratify patients presenting for exercise testing with suspected coronary disease according to the presence of angiographic coronary disease. Our goal was to determine how well this pretest score risk stratified patients undergoing pharmacological and exercise stress tests concerning prognostic endpoints. DESIGN: Retrospective cohort analysis. SETTING: University hospital stress laboratory. PATIENTS: 7452 unselected ambulatory patients with symptoms of suspected coronary disease undergoing stress testing between 1995 and 2004. MAIN OUTCOMES MEASURES: All-cause death, cardiac death and non-fatal myocardial infarction. RESULTS: The rate of all-cause death was 5.5% (CI 5.0 to 6.1) with 4.3 (SD 2.4) years of follow-up (Exercise 2.8% (CI 2.3 to 3.2) v Pharmacological group 11.9% (CI 10.5 to 13.3); p<0.001). The rate of cardiac death/myocardial infarction was 2.6% (CI 2.2 to 3.0) (Exercise 1.4% (CI 1.1 to 1.8) v Pharmacological group 5.3% (CI 4.3 to 6.2); p<0.001). In both groups, stratification by pretest score was significant for all-cause death and the combined endpoint. However, stratification was more effective in the pharmacological group using the combined endpoint rather than all-cause death. Pharmacological stress patients in intermediate and high risk groups were at higher risk than their respective exercise test cohorts. Referral for pharmacological stress testing was found to be an independent predictor of time to death (2.7 (CI 2.0 to 3.6); p<0.001). CONCLUSION: A pretest score previously validated to stratify according to angiographic outcomes, effectively risk stratified pharmacological and exercise stress patients according to the combined endpoint of cardiac death/myocardial infarction.