Evolving radiological protection guidelines for exploration-class missions.

International Space Station partner nations have yet to agree on career radiation dose constraints. This is of increasing concern for collaborative mission planning beyond low-Earth orbit, since it is likely that one or two long-duration missions will expose crew to a cumulative dose that approaches or exceeds their current respective limits. As with radiological effects, the cumulative health impact of the numerous other injuries and illnesses documented during spaceflight is inherently heightened with longer and farther missions, say to the Moon and Mars. This paper summarizes the origin of existing radiological constraints employed by the Canadian Space Agency and explores how to build upon these protection practices to address the challenges associated with beyond low-Earth orbit missions. The discussion then leads into a review of conventional risk metrics currently under evaluation by space-faring nations to quantify risk of radiation-induced cancer mortality. This paper concludes with a proposal for the application of an existing burden of disease model termed the Disability Adjusted Life Year, to space exploration. This model can accommodate the many health hazards of spaceflight, including ionizing radiation, on a common scale. It has the potential to serve as an intuitive communication tool for informing on the impact of spaceflight on crew health.

A commentary on the impact of modelling results to inform mission planning and shield design.

A correspondence has been received in reference to a recently published article titled "On the decision making criteria for cis-lunar reference scenarios". The intent of the paper was to demonstrate: (i) a novel methodology for calculating the dose from solar particle events (SPEs), and (ii) the impact of the SPE parametric model, shield thickness, dose metric, and radiation transport code on choosing a worst-case scenario. This effort assumed a spherical, aluminum spacecraft with an internal diameter of 3.8 m and with varying wall thickness ranging from 2 to 10 cm. A brief component of this article compared the dose from several solar particle events (SPEs) inside the spherical spacecraft geometry as calculated with Monte Carlo radiation transport code MCNPX and the on-line tool OLTARIS. In this comparison, the MCNPX simulation parameters assumed a volume-averaged dose while OLTARIS calculations assumed a point-dose estimate at the center of the spherical geometry. These modeling assumptions were detailed in the initial publication. The differences in the neutron, proton, and light-ion fluences and doses obtained between both codes were generally attributed to differences transport methodologies, nuclear physics models, boundary condition setup and detector regions. The commentary received demonstrated when both codes used a point-detector geometry and/or volume-averaged geometries, the two would yield similar proton fluences. This is a worthwhile observation that further emphasizes the impact of modeling assumption. The commentary further suggested however that the volume-averaged dose results "artificially reduced" estimates and that it was both "misleading" and "not-applicable" for use in storm shelter design. The response presented here will reiterate the context of the initial assumptions made, demonstrate the variability in point-dose estimates relative to a volume-averaged dose estimate, state why a volume-averaged estimate is equally applicable in this context, and lastly reference other factors that can give rise to increased uncertainty.

Spontaneous Necrotizing Fasciitis.

Necrotizing soft tissue infections typically begin with direct inoculation of bacteria into the subcutaneous tissues. Here, we present a case with no such exposure, but with severe necrotizing fasciitis. We present a middle-aged man presented to the emergency department for a presumed allergic reaction after having initially sought care twice at an urgent care facility. The patient had swelling, but no tenderness of his right lateral chest and flank. Subsequent imaging showed extensive fluid in the fascial planes of the right chest wall requiring surgical debridement. Necrotizing fasciitis that is not treated with surgical debridement carries a mortality rate approaching 100%. This case highlights a potential atypical presentation as well as highlights the fact that the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score lacks sensitivity to rule out a necrotizing soft tissue infection, requiring surgical debridement for diagnosis.

On the decision making criteria for cis-lunar reference mission scenarios.

Space agencies are currently developing reference mission scenarios to determine if occupational dose limits, already adopted for low-Earth orbit (LEO) missions to the International Space Station (ISS), are also applicable for deep space cis-lunar missions. These cis-lunar missions can potentially last upwards of a year, during which astronauts will experience a daily low-dose from galactic cosmic radiation (GCR) and a potentially high-dose from single, or multiple, solar particle events (SPEs). Unlike GCR exposure, SPEs are difficult to predict and model due to their sporadic nature. Consequently, mission planners have decided to rely on historical SPE spectra to prepare for the 'worst case' scenario. Assuming a spherical aluminum shell as a reference spacecraft, this paper demonstrates how the choice of SPE parametric model, shield thickness, dose metric, and radiation transport code can impact the decision-making criteria for the worst case SPE, the estimated GCR dose, and consequently whether current LEO dose limits are applicable.

Measuring cosmic-ray exposure in aircraft using real-time personal dosemeters.

Aircrew exposure to radiation was measured on several long-haul flights using two small commercial electronic personal dosemeters: one was a photon dosemeter, the NRF20; the other was a neutron dosemeter, the NRY21-both manufactured by Fuji Electric Systems Co. Ltd. for radiation protection at nuclear facilities. Non-neutron doses were measured using the photon dosemeter, and neutron doses were measured using the neutron dosemeter. The measured non-neutron doses at commercial aviation altitudes agree with the EPCARD (European Program Package for the Calculation of Aviation Route Doses) dose calculation within a difference of 8 %. However, the recorded neutron doses were 5-15 times larger than the EPCARD calculation. These over-measurements are dependent on cut-off rigidities.

Iron(III) coordination chemistry of alterobactin A: a siderophore from the marine bacterium Alteromonas luteoviolacea.

Alterobactin A is a siderophore produced by the oceanic bacterium Alteromonas luteoviolacea. The thermodynamic stability constant of the ferric alterobactin A (Alt-A) complex was estimated from electrochemical measurements on the basis of a previously reported linear relationship between the reduction potentials and the pH-independent stability constants for known iron(III) complexes. The reduction potential of the ferric alterobactin A complex determined by square wave voltammetry is -0.972 V vs SCE and reversible, corresponding to a thermodynamic stability constant of 10(51+/-2). Potentiometric titration of Fe(III)-Alt-A shows the release of six protons on complexation of Fe(III) to Alt-A. The 1H NMR resonances of the Ga(III)-Alt-A complex show that the C-4, C-5, and C-6 catecholate protons and the C(alpha) and C(beta) protons of both beta-hydroxyaspartate moieties are shifted downfield relative to the free ligand, which along with the potentiometric titration data is consistent with a complex in which Fe(III) is coordinated by both catecholate oxygen atoms and both oxygen atoms of each beta-hydroxyaspartate. The UV-vis spectrum of Fe(III)-Alt-A is invariant over the pH range 4-9, indicating the coordination does not change over a wide pH range. In addition, in the absence of a coordinated metal ion, the serine ester of Alt-A hydrolyzes forming Alt-B.

Tympanostomy tubes for otitis media: quality-of-life improvement for children and parents.

We measured quality of life issues for both children and their parents on the premise that parental quality of life should be an aspect of cost-effectiveness in otitis media treatment. The patients were less than 18 years of age and had had myringotomy with tube insertion at the head and neck surgery department of a large health maintenance organization. Quality of life for patients, parents, and caregivers was evaluated by telephone survey of parents or caregivers and by retrospective chart review of the number of pre- and postoperative healthcare visits and antibiotic usage. Chart review showed a significant postoperative reduction in the number of clinic visits and in use of antibiotic drugs after insertion of tympanostomy tubes. Improved postoperative hearing was noted, and tympanostomy tube insertion was shown to be safe. The chart-review cost analysis showed that tympanostomy tube insertion is a cost-effective treatment for otitis media in children, and the telephone survey results showed that it improves quality of life for children and their parents or other caregivers.

Odontoma of the middle ear: case report with 25-year follow-up.

We report the 25-year follow-up on the first reported case of odontoma in the middle ear. Diagnosis of odontoma had been made on the basis of radiography films that showed a middle ear mass with multiple toothlike areas of radiopacity. No clinical intervention was recommended. At 25-year follow-up, audiometry showed progressive mixed hearing loss on the affected side and mild ipsilateral sensorineural hearing loss. Computed tomography better characterized the discrete mass, which was shaped similar to a dental crown. To avoid jeopardizing cochlear and facial nerve function, no surgical intervention was pursued, and we recommended use of a BiCROS (bilateral contralateral routing of signal) hearing aid.