Investigating the performance characteristics of bromine quenched Geiger-Müller detectors with age and temperature.

The halogen quench gas present within a Geiger-Müller detector will govern its operational lifetime. Such halogen gases are highly corrosive and are very likely to interact with their surroundings. This factor must be taken into account when designing GM detectors to extend their lifetimes. The quench gas depletion is thought to be linked to the current resulting from the gas ionisation from each detection event. As such, GM detector lifetimes are typically expressed in units of total counts accumulated. At elevated temperatures, the molecules will possess more thermal energy and become more likely to interact. To preserve the amount of halogen gas in each detector, three different corrosion-resistant techniques have been considered for investigation; the samples used are ZP1200 GM detectors that consist of 446 stainless steel components. The surface treatment techniques used to prepare each sample were labeled as “raw” for an oxygen plasma process, “passivated” for a combination of a nitric acid passivation and an oxygen plasma process and, finally, “plated” for a combination of a chromium plating process and an oxygen plasma process. The effectiveness of each process has been studied at temperatures of up to 175 oC. A Caesium-137 source was used to age all detector samples by irradiating them with dose rates of 1.3 mSv/hr. 32 samples were aged at room temperature and another 32 samples were aged in parallel at an elevated temperature of 125 oC. At room temperature, all detector types produced stable detectors with operational parameters that did not change significantly with age. The plated samples did show an initial rise in their starting voltage (Vs) measurements. At 125 oC, the plated detectors produced the most stable lifetime performance after an initial Vs conditioning period. The passivated and raw detector samples, however, showed a drop in their Vs values. Preliminary studies carried out at 175 oC confirm the superiority of the chromium plating process at resisting performance degradation at elevated temperatures. After investigating the surfaces of the detector components, no changes with age in the bromine content were observed. The plated cathodes showed no bromine deposits when investigated using Energy Dispersive X-Ray Spectroscopy. Bromine was detected on the passivated and raw cathode surfaces, but its quantity remained unchanged with age. The impact of contamination on the performance of gas-filled radiation detectors was also investigated in collaboration with the Institut Laue-Langevin in Grenoble, France

Production and measurement of fission product noble gases

Gaseous fission products have been produced via thermal neutron irradiation of a highly-enriched uranium target and extracted using a custom gas processing system for measurement on a prototype, high-resolution β − γ coincidence detection system. The gas was extracted and measured in two stages in order to measure the prompt and β−–delayed fission products. This paper presents an overview of the system used to produce gaseous fission products, and the results of the advanced coincidence spectrometry techniques used to identify and quantify decays from the radionuclides produced, including the noble gases 85Kr, 85mKr, 88Kr, 133Xe, 135Xe, 133mXe and 135mXe, as well as 133I and 88Rb. The measurements were validated by determination of the nuclear decay half-lives, specifically for the ground state decay of 135Xe, which was found to be 9.15(49) hours and consistent with the literature value. This work demonstrates the UK capability to produce gaseous radionuclides for quality assurance and calibration purposes in Radionuclide Laboratories supporting the Comprehensive Nuclear-Test-Ban Treaty (CTBT).•Gaseous fission products have been produced through neutron irradiation of highly-enriched uranium at NPL.•A high-resolution beta-gamma coincidence detection system has been used to measure the gaseous fission products.•This paper compares the expected isotopic activity ratios from nuclear decay-ingrowth calculations with measurements.•The 135Xe half-life was determined through measurement and is in excellent agreement with the literature value

Epidemiology and outcomes of hospital-acquired bloodstream infections in intensive care unit patients: the EUROBACT-2 international cohort study

Purpose In the critically ill, hospital-acquired bloodstream infections (HA-BSI) are associated with significant mortality. Granular data are required for optimizing management, and developing guidelines and clinical trials. Methods We carried out a prospective international cohort study of adult patients (≥ 18 years of age) with HA-BSI treated in intensive care units (ICUs) between June 2019 and February 2021. Results 2600 patients from 333 ICUs in 52 countries were included. 78% HA-BSI were ICU-acquired. Median Sequential Organ Failure Assessment (SOFA) score was 8 [IQR 5; 11] at HA-BSI diagnosis. Most frequent sources of infection included pneumonia (26.7%) and intravascular catheters (26.4%). Most frequent pathogens were Gram-negative bacteria (59.0%), predominantly Klebsiella spp. (27.9%), Acinetobacter spp. (20.3%), Escherichia coli (15.8%), and Pseudomonas spp. (14.3%). Carbapenem resistance was present in 37.8%, 84.6%, 7.4%, and 33.2%, respectively. Difficult-to-treat resistance (DTR) was present in 23.5% and pan-drug resistance in 1.5%. Antimicrobial therapy was deemed adequate within 24 h for 51.5%. Antimicrobial resistance was associated with longer delays to adequate antimicrobial therapy. Source control was needed in 52.5% but not achieved in 18.2%. Mortality was 37.1%, and only 16.1% had been discharged alive from hospital by day-28. Conclusions HA-BSI was frequently caused by Gram-negative, carbapenem-resistant and DTR pathogens. Antimicrobial resistance led to delays in adequate antimicrobial therapy. Mortality was high, and at day-28 only a minority of the patients were discharged alive from the hospital. Prevention of antimicrobial resistance and focusing on adequate antimicrobial therapy and source control are important to optimize patient management and outcomes

Presentation, management, and outcomes of older compared to younger adults with hospital-acquired bloodstream infections in the intensive care unit: a multicenter cohort study

Purpose: Older adults admitted to the intensive care unit (ICU) usually have fair baseline functional capacity, yet their age and frailty may compromise their management. We compared the characteristics and management of older (≥ 75 years) versus younger adults hospitalized in ICU with hospital-acquired bloodstream infection (HA-BSI). Methods: Nested cohort study within the EUROBACT-2 database, a multinational prospective cohort study including adults (≥ 18 years) hospitalized in the ICU during 2019-2021. We compared older versus younger adults in terms of infection characteristics (clinical signs and symptoms, source, and microbiological data), management (imaging, source control, antimicrobial therapy), and outcomes (28-day mortality and hospital discharge). Results: Among 2111 individuals hospitalized in 219 ICUs with HA-BSI, 563 (27%) were ≥ 75 years old. Compared to younger patients, these individuals had higher comorbidity score and lower functional capacity; presented more often with a pulmonary, urinary, or unknown HA-BSI source; and had lower heart rate, blood pressure and temperature at presentation. Pathogens and resistance rates were similar in both groups. Differences in management included mainly lower rates of effective source control achievement among aged individuals. Older adults also had significantly higher day-28 mortality (50% versus 34%, p < 0.001), and lower rates of discharge from hospital (12% versus 20%, p < 0.001) by this time. Conclusions: Older adults with HA-BSI hospitalized in ICU have different baseline characteristics and source of infection compared to younger patients. Management of older adults differs mainly by lower probability to achieve source control. This should be targeted to improve outcomes among older ICU patients