Quantifying air-sea gas exchange using noble gases in a coastal upwelling zone

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in IOP Conference. Series: Earth and Environmental Science 35 (2016): 012017, doi:10.1088/1755-1315/35/1/012017.The diffusive and bubble-mediated components of air-sea gas exchange can be quantified separately using time-series measurements of a suite of dissolved inert gases. We have evaluated the performance of four published air-sea gas exchange parameterizations using a five-day time-series of dissolved He, Ne, Ar, Kr, and Xe concentration in Monterey Bay, CA. We constructed a vertical model including surface air-sea gas exchange and vertical diffusion. Diffusivity was measured throughout the cruise from profiles of turbulent microstructure. We corrected the mixed layer gas concentrations for an upwelling event that occurred partway through the cruise. All tested parameterizations gave similar results for Ar, Kr, and Xe; their air-sea fluxes were dominated by diffusive gas exchange during our study. For He and Ne, which are less soluble, and therefore more sensitive to differences in the treatment of bubble-mediated exchange, the parameterizations gave widely different results with respect to the net gas exchange flux and the bubble flux. This study demonstrates the value of using a suite of inert gases, especially the lower solubility ones, to parameterize air-sea gas exchange.Funding for this work was provided by NSF award OCE-1060840 to RHR Stanley, NSF award OCE-1129644 to DP Nicholson, an Ocean Ventures Fund award from the WHOI Academic Programs Office to CC Manning, and graduate scholarships from NSERC and CMOS to CC Manning

A survey investigating postero-anterior chest X-ray clinical technique amongst radiographers and assistant practitioners in the UK: An extended pilot study

IntroductionWhilst many technical factors for the postero-anterior (PA) chest projection are well-researched and standardised, anecdotal evidence suggests a discrepancy regarding positioning of the X-ray tube; some radiographers using a horizontal tube, and others apply an angle. Currently there is a lack of published evidence supporting the benefits of either technique.MethodsFollowing University ethical approval, an invitation e-mail containing a link to a short questionnaire and participant information sheet was sent to radiographers and assistant practitioners in Liverpool and the surrounding areas, via professional networks/research team contacts. Questions related to length of experience, highest qualification and reasoned choice of horizontal versus angled tube preference in Computed Radiography (CR) and Digital Radiography (DR) rooms. The survey was open for nine weeks, with reminders at five and eight weeks.ResultsThere were 63 respondents. Both techniques were commonplace, with a non-statistically significant preference (p = 0.439) for a horizontal tube in both DR rooms (59%, n = 37) and CR rooms (52%, n = 30). Angled technique was employed by 41% (n = 26) of participants in DR rooms and 48% (n = 28) in CR rooms. Many participants indicated 'taught', or 'protocol', influenced their approach (46% [n = 29] in DR, 38% [n = 22] in CR). 35% (n = 10) of participants using caudal angulation, identified dose optimisation as the rationale in both CR and DR rooms. Most specifically noted reduced dose to the thyroid (69% [n = 11] in CR, 73% [n = 11] in DR).ConclusionsThere is evidence of variation in practice regarding horizontal versus an angled X-ray tube but no consistent rationale for either choice.Implications for practiceThere is a need to standardise tube positioning in PA chest radiography in line with future empirical research into the dose-optimisation implications of tube angulation

Using noble gases to compare parameterizations of air‐water gas exchange and to constrain oxygen losses by ebullition in a shallow aquatic environment

Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 123 (2018): 2711-2726, doi:10.1029/2018JG004441.Accurate determination of air‐water gas exchange fluxes is critically important for calculating ecosystem metabolism rates from dissolved oxygen in shallow aquatic environments. We present a unique data set of the noble gases neon, argon, krypton, and xenon in a salt marsh pond to demonstrate how the dissolved noble gases can be used to quantify gas transfer processes and evaluate gas exchange parameterizations in shallow, near‐shore environments. These noble gases are sensitive to a variety of physical processes, including bubbling. We thus additionally use this data set to demonstrate how dissolved noble gases can be used to assess the contribution of bubbling from the sediments (ebullition) to gas fluxes. We find that while literature gas exchange parameterizations do well in modeling more soluble gases, ebullition must be accounted for in order to correctly calculate fluxes of the lighter noble gases. In particular, for neon and argon, the ebullition flux is larger than the differences in the diffusive gas exchange flux estimated by four different wind speed‐based parameterizations for gas exchange. We present an application of noble gas derived ebullition rates to improve estimates of oxygen metabolic fluxes in this shallow pond environment. Up to 21% of daily net oxygen production by photosynthesis may be lost from the pond via ebullition during some periods of biologically and physically produced supersaturation. Ebullition could be an important flux of oxygen and other gases that is measurable with noble gases in other shallow aquatic environments.NSF. Grant Numbers 1233678, 1238212, DEB 1354494; Woods Hole Oceanographic Institution (WHOI); National Defense Science and Engineering Graduate Fellowship; Northeast Climate Science Center Grant Number: DOI G12AC000012019-03-0

Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in Whycocomagh Bay, a Canadian estuary in the Bras d\u27Or Lake system

Sea ice is an important control on gas exchange and primary production in polar regions. We measured net oxygen production (NOP) and gross oxygen production (GOP) using near-continuous measurements of the O2∕Ar gas ratio and discrete measurements of the triple isotopic composition of O2, during the transition from ice-covered to ice-free conditions, in Whycocomagh Bay, an estuary in the Bras d\u27Or Lake system in Nova Scotia, Canada. The volumetric gross oxygen production was 5.4+2.8-1.6 role= presentation \u3e5.4+2.8−1.6 mmol O2 m−3 d−1, similar at the beginning and end of the time series, and likely peaked at the end of the ice melt period. Net oxygen production displayed more temporal variability and the system was on average net autotrophic during ice melt and net heterotrophic following the ice melt. We performed the first field-based dual tracer release experiment in ice-covered water to quantify air–water gas exchange. The gas transfer velocity at \u3e90 % ice cover was 6 % of the rate for nearly ice-free conditions. Published studies have shown a wide range of results for gas transfer velocity in the presence of ice, and this study indicates that gas transfer through ice is much slower than the rate of gas transfer through open water. The results also indicate that both primary producers and heterotrophs are active in Whycocomagh Bay during spring while it is covered in ice

The use of videofluoroscopy (VFS) and fibreoptic endoscopic evaluation of swallowing (FEES) in the investigation of oropharyngeal dysphagia in stroke patients: A narrative review.

ObjectivesPatients with suspected acute stroke require rapid assessment of swallowing on admission. If aspiration is suspected, this takes the form of specialist assessment, using either videofluoroscopy (VFS) or fibreoptic endoscopic evaluation of swallowing (FEES). The review aim was to evaluate and compare the effectiveness of each method in stroke patients. Literature was collected from the databases Scopus, Web of Science and Medline, and articles included in the review were published within the last 10 years, in the English language.Key findingsSensitivity and specificity ranged from 0.29-0.33 and 0.96-1.0 for VFS, respectively, and 0.37-1.0 and 0.65-0.87 for FEES, respectively, depending on the type of bolus utilised. VFS is the current gold-standard for the investigation of oropharyngeal dysphagia (OD), however, radiation dose and patient transport implications mean FEES may be preferred. FEES has limitations including 'whiteout' and the invasive nature of the endoscope. The NICE guidelines do not recommend a definitive protocol specifically in stroke patients. This suggests further research may be required to determine the most effective method.ConclusionFEES is a beneficial first line examination, providing limited invasiveness, and administering a high level of patient suitability, without using ionising radiation. VFS could potentially be useful following FEES to secure full visualisation, ensuring an aspiration event is not missed during FEES.Implications for practiceUse of FEES as the first line test rather than VFS, ensures radiation dose is as low as reasonably practicable (ALARP). Ongoing research to ensure protocols follow current best practice can help ensure accurate management of oropharyngeal dysphagia in stroke patients

Diagnostic and therapeutic radiography MSc dissertations: A rich source of clinically relevant research and development

Conference: UK Imaging and Oncology Congress Online 2021, 7-25 June 202

Continuum theory of vacancy-mediated diffusion

We present and solve a continuum theory of vacancy-mediated diffusion (as evidenced, for example, in the vacancy driven motion of tracers in crystals). Results are obtained for all spatial dimensions, and reveal the strongly non-gaussian nature of the tracer fluctuations. In integer dimensions, our results are in complete agreement with those from previous exact lattice calculations. We also extend our model to describe the vacancy-driven fluctuations of a slaved flux line.Comment: 25 Latex pages, subm. to Physical Review

Variation in the length and structure of reports written by reporting radiographers: A retrospective study.

IntroductionThe literature suggests that there is variation in various features of the written radiology report for a range of body areas and imaging modalities. The retrospective study presented here aims to determine if similar variation is demonstrated in a group of 5 reporting radiographers in a UK NHS Trust.MethodsFull reports for 1530 knee radiographic examinations performed from accident and emergency referrals were extracted for a 12-month period from a Radiology Information System (RIS) into Excel. Copied into Word, the word count function was used for each report and the number of words and characters (without spaces) was returned into Excel. Average word count and word length per report, by radiographer, were calculated for the following sections of the report: report title, main body and signature. SPSS was used to perform inferential statistical analysis.ResultsA wide range in the maximum and minimum average report lengths (60.88 v 17.83 words) was demonstrated. Statistically significant differences (p ConclusionVariation in report structure and length, as well as word length, was seen, comparable to studies of radiologist reports. Further research is required to investigate the drivers of this variation, and determine if there is any clinical significance