Corrections to Kusnetz method for measurements of radon progeny concentrations in air

In 1956, H.L. Kusnetz proposed a quick method for radon progeny concentration measurement in mine atmosphere using a single gross-alpha count of a membrane-filtered air. The method is still widely used today and is based on a number of impractical assumptions. An instantaneous sampling time (less than ten seconds), is one of these assumptions that ignores the build-up and decay of the progeny on the filter paper during the sampling period, which is typically in the order of a few minutes. Of special concern is the 214Bi decay during the sampling period, since 214Po's alphas are lost during the sampling time and cannot be accounted for during the counting time. In addition, the method assumes that 214Bi activity during the counting period is constant. This inaccurate assumption can result in a smaller count rate, especially when counting times are long. Hence, underestimated working levels are expected when using Kusnetz factors without correcting for the sampling and counting times. In this technical report, exact sampling and counting time corrections to the method are provided along with the updated Kusnetz factors that correspond to common equilibrium conditions to correctly estimate the Working Level in air. Additionally, time corrections to the commonly used self-absorption correction formula and the lower level of detectability (LLD) equation used for any sample measurement are given.

Steel Bar Counting from Images with Machine Learning

Counting has become a fundamental task for data processing in areas such as microbiology, medicine, agriculture and astrophysics. The proposed SA-CNN-DC (Scale Adaptive—Convolutional Neural Network—Distance Clustering) methodology in this paper is designed for automated counting of steel bars from images. Its design consists of two Machine Learning techniques: Neural Networks and Clustering. The system has been trained to count round and squared steel bars, obtaining an average detection accuracy of 98.81% and 98.57%, respectively. In the steel industry, counting steel bars is a time consuming task which highly relies on human labour and is prone to errors. Reduction of counting time and resources, safety and productivity of employees and high confidence of the inventory are some of the advantages of the proposed methodology in a steel warehouse.

The Roth score as a triage tool for detecting hypoxaemia in general practice: a diagnostic validation study in patients with possible COVID-19

Aim: To validate the Roth score as a triage tool for detecting hypoxaemia. Backgrounds: The virtual assessment of patients has become increasingly important during the corona virus disease (COVID-19) pandemic, but has limitations as to the evaluation of deteriorating respiratory function. This study presents data on the validity of the Roth score as a triage tool for detecting hypoxaemia remotely in potential COVID-19 patients in general practice. Methods: This cross-sectional validation study was conducted in Dutch general practice. Patients aged ≥18 with suspected or confirmed COVID-19 were asked to rapidly count from 1 to 30 in a single breath. The Roth score involves the highest number counted during exhalation (counting number) and the time taken to reach the maximal count (counting time). Outcome measures were (1) the correlation between both Roth score measurements and simultaneous pulse oximetry (SpO2) on room air and (2) discrimination (c-statistic), sensitivity, specificity and predictive values of the Roth score for detecting hypoxaemia (SpO2 < 95%). Findings: A total of 33 physicians enrolled 105 patients (52.4% female, mean age of 52.6 ± 20.4 years). A positive correlation was found between counting number and SpO2 (rs = 0.44, P < 0.001), whereas only a weak correlation was found between counting time and SpO2 (rs = 0.15, P = 0.14). Discrimination for hypoxaemia was higher for counting number [c-statistic 0.91 (95% CI: 0.85–0.96)] than for counting time [c-statistic 0.77 (95% CI: 0.62–0.93)]. Optimal diagnostic performance was found at a counting number of 20, with a sensitivity of 93.3% (95% CI: 68.1–99.8) and a specificity of 77.8% (95% CI: 67.8–85.9). A counting time of 7 s showed the best sensitivity of 85.7% (95% CI: 57.2–98.2) and specificity of 81.1% (95% CI: 71.5–88.6). Conclusions: A Roth score, with an optimal counting number cut-off value of 20, maybe of added value for signalling hypoxaemia in general practice. Further external validation is warranted before recommending integration in telephone triage.

PGE distribution in the chromitite layers at Eastern Chrome Mine, Eastern Bushveld Complex, South Africa: A descriptive study with comparison of EPMA and LA-ICP-MS methods for detection of trace PGE in base metal sulphides

A descriptive petrographic study was carried out on the chromitites (LG-6 to UG-3a) of a single borehole from the Winterveld Chrome Mine, Eastern BC, along with analysis by both EPMA and LA-ICP-MS of the PGE contents of base metal sulphides (BMS) found within these layers. EPMA measurements were optimized to measure trace amounts of PGE by increased probe current and counting time, yielding very low detection limits for this method (12 to 38 ppm). However, analytical error proved to be very high (over ~30%) in samples that showed PGE values below 100 ppm. Also, the possibility of interference on PGE spectra by other elements, especially on Rh, is high. Therefore, these measurements can only be considered semi-quantitative indicators of elemental PGE concentration. Our findings confirmed that pentlandite of the BC chromitites contains Pd and Rh, probably in solid solution. Pt was found in discrete minerals (braggite, cooperite) throughout the sequence, and Ru, Ir and Os were found as early-stage minerals such as laurite, associated with chromite rather than sulphide. The PPGE increase upwards in the chromitite layers relative to the IPGE. An immiscible sulphide phase contributed to collection of the PGE in the chromitites of the MG-4 and above. The chromitites of the LG-6 to MG-1 show less evidence of hosting an immiscible sulphide phase, and pentlandite of these layers does not appear to host Rh, although Pd was found. Although this borehole is located only 1.5 km away from the centre of the Steelpoort Fault Zone, a possible feeder zone for the BC, large-scale disruption of the chromitite layers was not observed. An intrusive pegmatoidal pyroxenite was found to occur beneath the LG-6, and contained PGE-bearing sulphides, although the origin of this mineralization is most likely from the LG-6 chromitite itself. A sulphide vein occurring in silicate was also analysed and was found to be PGE-deficient compared to the sulphides of the chromitite layers.

Midwifery e obstetrícia: uma variação denominativa

A área de obstetrícia possui tradições muito vinculadas à cultura de cada país. Tendo em vista esse contexto, o presente trabalho tem o objetivo de tratar da variação denominativa existente no par de línguas inglês e português em um artigo acadêmico desse âmbito. Com base no texto Counting Time in Pregnancy and Labour (DOWNE; DYKES, 2009) e na tradução feita pela autora do artigo, trataremos das traduções de termos técnicos, principalmente vinculados à área de atuação das midwives, que ilustram essas diferenças culturais na forma em que o parto ocorre na Inglaterra e no Brasil. Como resultado, foi possível observar que a escolha de traduzir ‘midwifery’ por ‘obstetrícia’, apesar de ter sido aconselhada por uma profissional da área, não foi a solução considerada mais adequada. Foi possível concluir que, em um contexto em que há discrepância entre as culturas do país-fonte e do país-alvo, seria conveniente que o tradutor escrevesse um prefácio ou nota do tradutor onde fosse explicado de que forma ocorrem essas diferenças culturais.

The Diagnostic Accuracy of Subjective Dyspnea in Detecting Hypoxemia Among Outpatients with COVID-19

Objectives: The majority of patients with mild-to-moderate COVID-19 can be managed using virtual care. Dyspnea is challenging to assess remotely, and the accuracy of subjective dyspnea measures in capturing hypoxemia have not been formally evaluated for COVID-19. We explored the accuracy of subjective dyspnea in diagnosing hypoxemia in COVID-19 patients. Methods: This is a retrospective cohort study of consecutive outpatients with COVID-19 who met criteria for home oxygen saturation monitoring at a university-affiliated acute care hospital in Toronto, Canada from April 3, 2020 to June 8, 2020. Hypoxemia was defined by oxygen saturation <95%. Dyspnea measures were treated as diagnostic tests, and we determined their sensitivity (SN), specificity (SP), negative/positive predictive value (NPV/PPV), and positive/negative likelihood ratios (+LR/-LR) for detecting hypoxemia. Results: During the study period 64/298 (21.5%) of patients met criteria for home oxygen saturation monitoring, and of these 14/64 (21.9%) were diagnosed with hypoxemia. The presence/absence of dyspnea had limited accuracy for diagnosing hypoxemia, with SN 57% (95% CI 30-81%), SP 78% (63%-88%), NPV 86% (72%-94%), PPV 42% (21%-66%), +LR 2.55 (1.3-5.1), -LR 0.55 (0.3-1.0). An mMRC dyspnea score >1 (SP 97%, 95%CI 82%-100%), Roth Maximal Count <12 (SP 100%, 95%CI 75-100%), and Roth Counting time < 8 seconds (SP 93%, 95%CI 66%-100%) had high SP that could be used to rule in hypoxemia, but displayed low SN (≤50%). Conclusions: Subjective dyspnea measures have inadequate accuracy for ruling out hypoxemia in high-risk patients with COVID-19. Safe home management of patients with COVID-19 should incorporate home oxygenation saturation monitoring.