A baseline for source localisation using the inverse modelling tool FREAR.

A global network of monitoring stations is set up that can measure tiny concentrations of airborne radioactivity as part of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. If Treaty-relevant detections are made, inverse atmospheric transport modelling is one of the methods that can be used to determine the source of the radioactivity. In order to facilitate the testing of novel developments in inverse modelling, two sets of test cases are constructed using real-world 133Xe detections associated with routine releases from a medical isotope production facility. One set consists of 24 cases with 5 days of observations in each case, and another set consists of 8 cases with 15 days of observations in each case. A series of inverse modelling techniques and several sensitivity experiments are applied to determine the (known) location of the medical isotope production facility. Metrics are proposed to quantify the quality of the source localisation. Finally, it is illustrated how the sets of test cases can be used to test novel developments in inverse modelling algorithms.

Radionuclide measurements of the international monitoring system.

The International Monitoring System (IMS) is a unique global network of sensors, tuned to measure various phenomenology, with the common goal of detecting a nuclear explosion anywhere in the world. One component of this network collects measurements of radioactive particulates and gases (collectively known as radionuclides) present in the atmosphere; through this, compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) can be verified. The radionuclide sub-network consists of 120 sensors across 80 locations, supported by 16 measurement laboratories. All radionuclide stations make use of a form of γ-ray spectroscopy to measure radionuclides from samples; this remains largely unchanged since the network was first established 25 years ago. Advances in sampling and spectroscopy systems can yield improvements to the sensitivity of the network to detect a nuclear explosion. This paper summarises the status of the IMS radionuclide network, the current suite of technology used and reviews new technology that could enhance future iterations, potentially improving the verification power of the IMS.

Transport of Multispecies Ion Crystals through a Junction in a Radio-Frequency Paul Trap.

We report on the first demonstration of transport of a multispecies ion crystal through a junction in a rf Paul trap. The trap is a two-dimensional surface-electrode trap with an X junction and segmented control electrodes to which time-varying voltages are applied to control the shape and position of potential wells above the trap surface. We transport either a single ^{171}Yb^{+} ion or a crystal composed of a ^{138}Ba^{+} ion cotrapped with the ^{171}Yb^{+} ion to any port of the junction. We characterize the motional excitation by performing multiple round-trips through the junction and back to the initial well position without cooling. The final excitation is then measured using sideband asymmetry. For a single ^{171}Yb^{+} ion, transport with a 4 m/s average speed induces between 0.013±0.001 and 0.014±0.001 quanta of excitation per round-trip, depending on the exit port. For a Ba-Yb crystal, transport at the same speed induces between 0.013±0.001 and 0.030±0.002 quanta per round-trip of excitation to the in-phase axial mode. Excitation in the out-of-phase axial mode ranges from 0.005±0.001 to 0.021±0.001 quanta per round-trip.

The Effectiveness of Direct Supervision by an Attending Compared To a Senior Resident on Quality of Supervision of Novice Anesthesiology Residents: A Randomized Study.

Background: New trainees are directly supervised by either an attending physician or a senior resident under indirect supervision from an attending physician. The main objective was to evaluate which type of direct supervision (attending vs. senior resident) would result in better quality of supervision to novice residents during their first month of training. Methods: Novice anesthesiology residents were randomized to receive direct supervision by an attending anesthesiologist or a senior resident during their introduction month of intraoperative anesthesia. The primary outcome was a validated instrument to evaluate supervision performance of the instructor. The secondary outcome was a validated anxiety scale. Results: The overall mean supervision score across the study days was greater in the residents who were directly supervised by attendings, mean (standard error [SE]) of 3.88 ± 0.03 compared with direct supervision by a senior resident, mean (SE) of 3.77 ± 0.03 a mean difference of 0.11 (95% confidence interval [CI], 0.05-0.16), P = .0012. Five of 9 individual items on the supervision survey were significantly greater in the group directly supervised by attendings compared with residents. There was no difference between groups regarding anxiety scores. In contrast, there was a mild association between supervision scores and Spielberger State-Trait Anxiety Inventory-6 anxiety scores, correlation coefficient = 0.23 (95% CI, 0.08-0.39), P < .0035. Conclusions: We detected better supervision scores when novice anesthesiology residents were directly supervised by attendings when compared with senior residents. Nevertheless, direct supervision by senior residents still provided supervision scores consistent with a safe supervision practice.

Uncertainty and source term reconstruction with environmental air samples.

Environmental air sampling is one of the principal monitoring technologies employed for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). By combining the analysis of environmental samples with Atmospheric Transport and Dispersion Modelling (ATDM), and using a Bayesian source reconstruction algorithm, an estimate of the release location, duration, and quantity can be computed. Bayesian source reconstruction uses an uncertainty distribution of the input parameters, or priors, in a statistical framework to produce posterior probability estimates of the event parameters. The quality of the event reconstruction directly depends on the accuracy of the prior uncertainty distribution. With many of the input parameters, the selection of the uncertainty distribution is not difficult. However, with environmental samples, there is one component of the uncertainty at the interface between sample measurements and the ATDM that has been overlooked. Typically, a much smaller volume or quantity of material is sampled from the much larger domain represented in the ATDM. By examining the response of a dense network of radionuclide detectors on the West Coast of Canada during the passage of the Fukushima debris plume, an initial estimate of this uncertainty was determined to be between 20% and 30% depending on sample integration time.

Bayesian source reconstruction of an anomalous Selenium-75 release at a nuclear research institute.

Atmospheric transport and dispersion models are important tools in radiation protection as they help to estimate the impact of radionuclides released into the atmosphere. In particular, such models can be used in combination with radionuclide observations to estimate unknown source term parameters, or to improve source term estimates obtained through other methods. In this paper, a Bayesian inference system was used to determine the source term parameters and their corresponding credible intervals of a real-world anomalous 75Se release at a nuclear facility in Belgium. Furthermore, a formulation is proposed that not only takes into account true detections, but also true instrumental non-detections, false alarms and real misses. The Bayesian inference system is able to correctly determine the known source location. The Bayesian inference is then refined by fixing the release location and by making stronger assumptions about the release period.

Medical isotope production, research reactors and their contribution to the global xenon background.

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans the testing of nuclear explosive devices underground, in the atmosphere and underwater. Two main technologies, radionuclide and seismo-acoustic monitoring, are deployed in the International Monitoring System used for the verification of the CTBT. Medical isotope production from fission-based processes is the dominant contributor to a worldwide background of radioxenon. This background can make the discrimination of nuclear tests from legitimate nuclear activities very challenging. Even if emissions from medical isotope producers experienced a large reduction, there remain other important sources of radioxenon that contribute to the global background such as research reactors and nuclear power plants. Until recently, the largest producer of medical isotopes was located in Canada, at the Canadian Nuclear Laboratories (CNL) facility. The characterization of CNL emissions and its research reactor can provide valuable information for effective verification of the CTBT.

International challenge to predict the impact of radioxenon releases from medical isotope production on a comprehensive nuclear test ban treaty sampling station.

The International Monitoring System (IMS) is part of the verification regime for the Comprehensive Nuclear-Test-Ban-Treaty Organization (CTBTO). At entry-into-force, half of the 80 radionuclide stations will be able to measure concentrations of several radioactive xenon isotopes produced in nuclear explosions, and then the full network may be populated with xenon monitoring afterward. An understanding of natural and man-made radionuclide backgrounds can be used in accordance with the provisions of the treaty (such as event screening criteria in Annex 2 to the Protocol of the Treaty) for the effective implementation of the verification regime. Fission-based production of (99)Mo for medical purposes also generates nuisance radioxenon isotopes that are usually vented to the atmosphere. One of the ways to account for the effect emissions from medical isotope production has on radionuclide samples from the IMS is to use stack monitoring data, if they are available, and atmospheric transport modeling. Recently, individuals from seven nations participated in a challenge exercise that used atmospheric transport modeling to predict the time-history of (133)Xe concentration measurements at the IMS radionuclide station in Germany using stack monitoring data from a medical isotope production facility in Belgium. Participants received only stack monitoring data and used the atmospheric transport model and meteorological data of their choice. Some of the models predicted the highest measured concentrations quite well. A model comparison rank and ensemble analysis suggests that combining multiple models may provide more accurate predicted concentrations than any single model. None of the submissions based only on the stack monitoring data predicted the small measured concentrations very well. Modeling of sources by other nuclear facilities with smaller releases than medical isotope production facilities may be important in understanding how to discriminate those releases from releases from a nuclear explosion.

Bayesian Inference for Source Reconstruction: A Real-World Application.

This paper applies a Bayesian probabilistic inferential methodology for the reconstruction of the location and emission rate from an actual contaminant source (emission from the Chalk River Laboratories medical isotope production facility) using a small number of activity concentration measurements of a noble gas (Xenon-133) obtained from three stations that form part of the International Monitoring System radionuclide network. The sampling of the resulting posterior distribution of the source parameters is undertaken using a very efficient Markov chain Monte Carlo technique that utilizes a multiple-try differential evolution adaptive Metropolis algorithm with an archive of past states. It is shown that the principal difficulty in the reconstruction lay in the correct specification of the model errors (both scale and structure) for use in the Bayesian inferential methodology. In this context, two different measurement models for incorporation of the model error of the predicted concentrations are considered. The performance of both of these measurement models with respect to their accuracy and precision in the recovery of the source parameters is compared and contrasted.

Five year outcomes study of dental rehabilitation conducted under general anesthesia for special needs patients.

We assessed the safety of general anesthesia for dental treatment of special needs patients as it related to American Society of Anesthesiology Physical Status (ASAPS) classification, procedure, and other factors. After Institutional Review Board review and approval, special needs patients who were admitted to the outpatient surgical operating room for comprehensive dental rehabilitation (CDR) under general anesthesia within a period of 5 years had their medical records evaluated retrospectively for intraoperative and postoperative complications both related to anesthesia and surgery. All records were evaluated by an independent evaluator who tabulated the patients' age, gender, ASAPS, and duration of procedure. N = 363, age mean = 46.93 +/- 16.835 years, age median = 48 years, male patients = 180, female patients = 183, ASAPS I =183, ASAPS II = 127, ASAPS III = 53, duration of surgery mean = 140.631 +/- 23.104 minutes, duration of surgery median time = 142.000 minutes, and number of complications = 2. One complication resulted in an ASAPS I 16-year-old boy, which was airway related, and a second was an ASAPS III 22-year-old woman, which was surgically related. Both led to unplanned inpatient admissions and were treated successfully with no residual morbidity. Dental rehabilitation of special needs patients under general anesthesia is safe. While morbidity is very low, larger studies are needed to establish risk versus benefit stratification among this patient population.

Fentanyl or dexmedetomidine combined with desflurane for bariatric surgery.

STUDY OBJECTIVE: Because fentanyl has ventilatory depressing effects, alternative methods for analgesia may be beneficial for management of bariatric surgery. We evaluated whether dexmedetomidine infusion could replace fentanyl for facilitation of open gastric bypass surgery. DESIGN: Randomized, single blinded, open label. SETTING: University teaching hospital. PATIENTS: Twenty bariatric patients with an average body mass index of 54 to 61 kg/m2 undergoing surgery for open gastric bypass. INTERVENTIONS: Patients were randomized to receive either fentanyl (0.5-microg/kg bolus, 0.5 microg.kg(-1).h(-1), n = 10) or dexmedetomidine (0.5-microg/kg bolus, 0.4 microg.kg(-1).h(-1), n = 10) for intraoperative analgesia. In both groups, end-tidal desflurane was adjusted to maintain the bispectral index at 45 to 50. MEASUREMENTS: In the operating room, blood pressure and heart rate were measured at 5-minute intervals. Bispectral index and end-tidal desflurane concentration were measured every hour. During recovery in the postanesthesia care unit, patient-evaluated pain scores and morphine use by patient-controlled analgesia pump were determined. MAIN RESULTS: During surgery, desflurane concentrations necessary to maintain the bispectral index at 45 to 50 were decreased, and blood pressure and heart rate were lower with in the dexmedetomidine compared with fentanyl group. In the postanesthesia care unit, pain scores and morphine use were decreased in the dexmedetomidine group. CONCLUSIONS: Dexmedetomidine, when used to substitute for fentanyl during gastric bypass surgery, attenuates blood pressure and provides postoperative analgesia.