Determination of the activity and nuclear decay data of 157Tb.

Terbium-157 was radiochemically extracted from an irradiated tantalum target. Since the resulting material contained a significant impurity of 158Tb, 157Tb was isotopically purified using laser resonance ionization at the RISIKO mass separator in Mainz and then implanted on an aluminum (Al) foil. The implanted 157Tb was measured by two different calibrated gamma-ray spectrometers to determine photon emission rates. After dissolving the Al foil, a high purity 157Tb solution was obtained. The corresponding activity concentration was determined with a low relative uncertainty of 0.52% through a combination of liquid scintillation counting using the TDCR method and 4π(X,e)(LS)-(X,γ)(CeBr3) coincidence counting. By combining the results from all measurement techniques, emission intensities for K X-rays and gamma-rays were derived and found to be 16.05(31)% and 0.0064(2)%, respectively. The probability for K electron capture of the first forbidden non-unique transition to the ground state was determined to be 17.16(35)%. The probabilities for the electron-capture branch to the excited level and the ground state were found to be 0.084(4)% and 99.916(4)%, respectively. A Q+ value of 60.23(18) keV was estimated based on simplified BetaShape calculations, assuming an allowed transition.

Evolution of traceable radon emanation sources from MBq to few Bq.

In the framework of the EMPIR project traceRadon, stable atmospheres with low-level radon activity concentrations have to be produced for calibrating radon detectors designed to measure outdoor air activity concentrations. The traceable calibration of these detectors at very low activity concentrations is of special interest to the radiation protection, climate observation, and atmospheric research communities. Radiation protection networks (such as the EUropean Radiological Data Exchange Platform (EURDEP)) and atmospheric monitoring networks (such as the Integrated Carbon Observation System (ICOS)) need reliable and accurate radon activity concentration measurements for a variety of reasons, including: the identification of Radon Priority Areas (RPA); improving the sensitivity and reliability of radiological emergency early warning systems (Melintescu et al., 2018); for more reliable application of the Radon Tracer Method (RTM) to estimate greenhouse gas (GHG) emissions; for improved global "baseline" monitoring of changing GHG concentrations and quantification of regional pollution transport (Chambers et al., 2016), (Chambers et al., 2018); and for evaluating mixing and transport parameterisations in regional or global chemical transport models (CTMs) (Zhang et al., 2021), (Chambers et al., 2019). To achieve this goal, low activity sources of radium with a variety of characteristics were produced using different methods. Sources ranging from MBq 226Ra down to several Bq 226Ra were developed and characterised during the evolution of production methods, and uncertainties below 2 % (k=1) were achieved through dedicated detection techniques, even for the lowest activity sources. The uncertainty of the lowest activity sources was improved using a new online measurement technique for which the source and detector were combined in the same device. This Integrated Radon Source Detector device, henceforth an IRSD, reaches a counting efficiency approaching 50 % through detection under quasi 2π sr solid-angle. At the time of this study the IRSD was already produced with 226Ra activities between 2 Bq and 440 Bq. To compare the working performance of the developed sources (i.e., to establish a reference atmosphere), study the stability of the sources, and to establish traceability to national standards, an intercomparison exercise was carried out at the PTB facility. Here we present the various source production techniques, the determination of their radium activity, and determination of their radon emanation (including assigned uncertainties). This includes details of the implementation of the intercomparison set-up, and a discussion of the results of the source characterisations.

Development of 222Rn Emanation Sources with Integrated Quasi 2π Active Monitoring.

In this work, a novel approach for the standardization of low-level 222Rn emanation is presented. The technique is based on the integration of a 222Rn source, directly, with an α-particle detector, which allows the residual 222Rn to be continuously monitored. Preparation of the device entails thermal physical vapor deposition of 226RaCl2 directly onto the surface of a commercially available ion implanted Si-diode detector, resulting in a thin-layer geometry. This enables continuous collection of well resolved α-particle spectra of the nuclei, decaying within the deposited layer, with a detection efficiency of approximately 0.5 in a quasi 2π geometry. The continuously sampled α-particle spectra are used to derive the emanation by statistical inversion. It is possible to achieve this with high temporal resolution due to the small background and the high counting efficiency of the presented technique. The emanation derived in this way exhibits a dependence on the relative humidity of up to 15% in the range from 20% rH to 90% rH. Traceability to the SI is provided by employing defined solid-angle α-particle spectrometry to characterize the counting efficiency of the modified detectors. The presented technique is demonstrated to apply to a range covering the release of at least 1 to 210 222Rn atoms per second, and it results in SI-traceable emanation values with a combined standard uncertainty not exceeding 2%. This provides a pathway for the realization of reference atmospheres covering typical environmental 222Rn levels and thus drastically improves the realization and the dissemination of the derived unit of the activity concentration concerning 222Rn in air.

Ion implantation of 226Ra for a primary 222Rn emanation standard.

Laser resonance ionization at the RISIKO 30 kV mass separator has been used to produce isotopically and isobarically pure and well quantified 222Rn emanation standards. Based upon laser-spectroscopic preparation studies, ion implantation into aluminum and tungsten targets has been carried out, providing overall implantation efficiencies of 40% up to 60%. The absolute implanted activity of 226Ra was determined by the technique of defined solid-angle α-particle spectrometry, where excellent energy resolution was observed. The 222Rn emanation coefficient of the produced targets was studied using α-particle and γ-ray spectrometry, and yielded results between 0.23 and 0.34, with relative uncertainty on the order of 1%. No dependence exceeding a 1% change of the emanation on humidity could be identified in the range of 15 %rH to 75 %rH, whereas there were hints of a slight correlation between the emanation and temperature. Additionally, and as expected, the emanation coefficient was found to be dependent on the target material as well as the implanted dose.

Activity standardization by means of liquid scintillation counting and determination of the half-life of 89Zr.

A89Zr solution was measured by means of liquid scintillation counting techniques in order to determine the activity concentration. Two methods were used: the CIEMAT/NIST efficiency tracing method with 3H as a tracer, and the triple-to-double coincidence ratio method. The counting efficiencies were computed with a stochastic model. The very detailed investigation showed that a few corrections are particularly important: Asymmetries in the photodetector responses as well as the backscattering of high-energy gamma rays must be taken into account. Corresponding corrections have therefore been applied. In addition, a detailed uncertainty analysis was carried out and the uncertainties compared with those determined by other research groups. The activity concentrations obtained from the two methods agree well and a combined result was used to establish calibration factors for ionization chambers, which are important secondary standardization instruments. The ionization chambers were combined with a new high-precision current measurement device to provide outstanding linearity. Measurement data from one chamber were used to determine the half-life, which was found to be T1/2=(78.373 ± 0.023) h.

Job mobility and job performance: beliefs about social and occupational (dis)advantages as mediators.

Background. Modern working conditions require an increased amount of spatial mobility from employed personnel. Research suggests that different types of job mobility might exert negative effects on well-being and health, and additionally have different costs and benefits for the work and the social domains. Methods. Using data from 3191 members of the German Armed Forces, we investigated the effects of four different types of job mobility (long-distance commuters, overnighters, residential mobiles and multi-mobiles) in contrast to non-mobiles on employees' subjective job performance as an occupationally relevant outcome. Moreover, we expected beliefs about social and occupational advantages and disadvantages to mediate the effects of job mobility on subjective job performance. Results. A single concrete event during relocation had fewer negative consequences compared to the effects of circular mobility or multi-mobility. Moreover, beliefs about occupational and social advantages and disadvantages were differently associated with the different types of job mobility and partially mediated the direct effects of job mobility on job performance. Conclusions. Not all types of job mobility are an impairment and extra-organizational stress. Rather, the evaluation and perception of occupational and social (dis)advantages is crucial for the effects of different types of job mobility on organizational relevant outcomes.

The Effectiveness of Combat Tactical Breathing as Compared with Prolonged Exhalation.

Tactical breathing (TB) is used by military and law enforcement personnel to reduce stress and maintain psychomotor and cognitive performance in dangerous situations (Grossman and Christensen, in On combat: the psychology and physiology of deadly conflict in war and in peace, PPCT Research Publications, Belleville, 2008). So far, empirical evidence on the effectiveness of TB is limited and there are breathing techniques that are easier to learn and to apply. This study compared the effectiveness of tactical breathing and prolonged exhalation (ProlEx) under laboratory conditions. Thirty healthy participants performed a Stroop interference task under time pressure and noise distraction. Time pressure was induced with short inter-trial intervals of 350 ms and short trial durations of 1500 ms. Acoustic distraction was realised with white noise with intensity increasing from 77 to 89 dB SPL over the course of an experimental block. In a counterbalanced repeated-measures design, participants used either TB or ProlEx to reduce the induced psychological and physiological arousal. Stress reactions were assessed on the subjective level (Steyer et al., in Multidimensional mood questionnaire (MDMQ), Hogrefe, Göttingen, 1997) and on the physiological level (heart rate, heart rate variability, electrodermal activity). Results showed no significant differences between breathing techniques on the subjective level. While participants showed a lower physiological arousal in the TB condition, better performance was achieved in the ProlEx condition. Results indicate that TB may be superior in passive coping conditions, while ProlEx is more effective when active coping is required.

A new primary emanation standard for Radon-222.

New emanation sources for Rn-222 have been developed by electrodeposition of Ra-226 onto stainless-steel discs. With a high resolution of up to 20 keV FWHM in the Ra-226 peak at 4.87 MeV, defined solid-angle alpha-particle spectrometry is the method of choice to determine the deposited Ra-226 activity. The amount of emanating Rn-222 is determined by gamma-ray spectrometry using HPGe-detectors. The measurement is based on the distorted equilibrium of the Ra-226 decay chain due to Rn-222 emanation. Comparative gamma-ray spectrometric measurements with sealed, Rn-222 tight sources of the same type and geometry make the knowledge of emission probabilities and detection efficiency unnecessary. The new emanation sources allow the production of stable reference atmospheres in the regime below 300 Bq⋅m-3 with uncertainties not exceeding 2% for k = 1.

Half-life determination and comparison of activity standards of 231Pa.

The results of an international comparison of activity measurements of a solution of 231Pa are reported and analysed. Prior to this, no known standardisation of 231Pa by activity measurement had been carried out. The comparison was run in 2017-2018 involving eight laboratories, and returned results with no identifiable inconsistencies between methods or laboratories. The results, including one mass determination, gave a231Pa activity concentration of 41.461(48) kBq g-1 and a231Pa atom concentration of 61.48(23) × 1015 atoms g-1, from which a half-life value of 32 570(130) years was derived.

Effects of a Workplace-Based Sleep Health Program on Sleep in Members of the German Armed Forces.

STUDY OBJECTIVES: To develop and evaluate a brief manual-based sleep health program within the workplace health promotion of the German Armed Forces. METHODS: The sleep health program comprised four weekly group sessions. Sixty-three members (48 males) were randomly allocated to either a treatment group or a waiting control group matching for age, sex, and baseline Pittsburgh Sleep Quality Index (PSQI). The control group had to wait before participating in the sleep health program until the treatment group finished the intervention. Sleep was assessed by ambulatory polysomnography (PSG) as well as with evening and morning protocols at baseline (t0), directly after the treatment group participated in the sleep health program (t1), and after the control group finished participation (t2). The PSQI, the Insomnia Severity Index (ISI), and the Epworth Sleepiness Scale (ESS) were applied at the same three time points, and during a 3-month follow-up evaluation (t3). RESULTS: Fifty-seven out of the 63 randomized individuals (42 males, mean age = 40.6 years; complete PSG data: n = 36; complete questionnaire data: n = 39) participated in the sleep health program. Objective wake after sleep onset, sleep efficiency, latency to persistent sleep, self-reported sleep latency, restfulness, PSQI, and ISI scores improved with medium or large effects in both groups. ESS scores decreased with moderate effects in the treatment group only. CONCLUSIONS: The sleep health program had a positive and stable effect on objective and self-reported sleep parameters, and it is suitable as a preventive measure in members of the German Armed Forces. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Title: Development and Evaluation of a Sleep-coaching Program; Identifier: NCT02896062; URL: https://clinicaltrials.gov/ct2/show/record/NCT02896062.

Social cognitive aspects of the participation in workplace health promotion as revealed by the theory of planned behavior.

Health-promoting efforts strongly depend on individual cognitions such as attitudes as well as social cognitive aspects of the work environment such as leadership and support. Using the theory of planned behavior (TPB) as a theoretical frame, participation behavior of employees in courses offered by the workplace health promotion (WHP) program of the German Armed Forces was investigated. Social cognitive aspects of the work environment, such as leadership behaviors by setting an example or optimizing organization of work, were included in the TPB components of subjective norm and perceived behavioral control, which allowed for an investigation of the specific effects of leadership on WHP participation. A survey study with N=1385 members of the German Armed Forces was conducted in 2015 in Germany. Results showed that perceived behavioral control and attitudes towards WHP were the strongest predictors for WHP participation. While subjective norm was positively related to attitudes, it had a slightly negative effect on intention to participate in WHP activities. These findings suggest that the most effective way for leadership to increase WHP participation is to enhance perceived behavioral control. Quite contrary, creating a positive subjective norm regarding WHP participation may even result in psychological reactance.

Ship management attitudes and their relation to behavior and performance.

OBJECTIVE: The aim of this study was to adapt the Crew Resource Management (CRM) Attitudes Questionnaire (CMAQ) to the maritime domain, to assess the ship management attitudes of junior naval officers, and to determine the extent to which these attitudes correlate with behavior and performance in a naval exercise. BACKGROUND: CRM attitudes have been shown to be associated with performance in aviation, but it is unclear whether this construct is applicable and relevant to the maritime domain. METHOD: Participants were 121 active seafarers and 101 junior officers of the German Navy who completed the Ship Management Attitudes Questionnaire-German Navy (SMAQ-GN). Ratings of nontechnical skills and ratings of mission success of the junior officers were collected during a real-world naval exercise. RESULTS: Internal consistencies of SMAQ-GN were similar to those of the original CMAQ and retest reliability was rather high. Attitudes of junior officers toward communication and coordination were positive. Regarding command responsibility and the recognition of stressor effects, positive as well as neutral and negative attitudes were found. Overall, attitudes did not correlate with behavior and performance. Separate analysis of those participants reporting negative to neutral ship management attitudes showed substantial positive correlations of attitudes with behavior and performance. CONCLUSION: Ship management attitudes play a significant role in commanding ships. The attitude-performance linkage is not linear. Behavior and performance are less effective in officers with negative attitudes and equally effective in officers with slightly positive and very positive attitudes. APPLICATION: Ship management attitudes can be used to assess training needs for nautical teams.

Does inert gas narcosis have an influence on perception of pain?

The effect of an increased nitrogen partial pressure under hyperbaric conditions is known as nitrogen narcosis (NN). At an ambient pressure of about 4 bar, reduced cognitive performance as well as euphoric effects are reported. We examined the effect of NN on pain perception. 22 subjects completed an experimental (50 meters = 6 bar) and a simulated control dive (0 m = 1 bar) in a hyperbaric chamber. Before and during each dive a standardized cold pressure test was performed. The intensity of pain perceived was assessed with the help of a visual analogue scale; additionally, subjects assessed the subjective effect of NN. The study showed that the perceived pain intensity is significantly reduced under nitrogen narcosis conditions (F1.21 = 5.167, p < 0.034) when compared to the perceived pain intensity under the control dive conditions (F1.21 = 0.836, p = 0.371). A connection between perceived pain intensity and subjects experience of the NN was not found under the experimental dive condition (r = 0.287, p = 0.195). We could show that even relatively moderate hyperbaric conditions may have an influence on the perception of pain. The results are highly relevant since nitrogen narcosis occurs in divers as well as in medical personnel or construction workers, working under hyperbaric conditions.

Neuropsychological deficits in scuba divers: an exploratory investigation.

OBJECTIVE: To investigate whether divers with varying levels of experience and without a history of reported decompression sickness (DCS) show neuropsychometric alterations possibly as a result of so-called repetitive "silent" paradoxical gas embolisms. METHODS: Using reaction time as a psychometric measure, 17 experienced military divers (ED, logging between 150 and 1,200 diving hours) and eight very experienced military divers (VED, logging between 2,800 and 9,800 diving hours) with no decompression sickness (DCS) in their medical histories were compared to 23 healthy controls without any diving history, matched as closely as possible with respect to age for the two diving groups. Motor reaction time, decision reaction time and error rates were measured during completion of both simple and complex reaction time tasks. RESULTS: Compared to their control group, VED showed significantly higher motor reaction times on both tasks and significantly higher decision reaction times in the complex task. ED were not found to be different from their respective controls. No changes in performance quality in terms of increased errors were observed in any of the tasks for either diving group. CONCLUSIONS: The findings support the proposed possibility that minimal cerebral lesions occur after diving even without DCS. Further studies with this highly selective population of very experienced divers using more elaborate neurocognitive and neuromotor tasks seem warranted.

Image-guided navigation: the surgeon's perspective on performance consequences and human factors issues.

BACKGROUND: Image-guided navigation (IGN) represents a first step in the automation of surgical functions. The use of IGN can involve several human factors issues that must be taken into account when evaluating their impact on surgical performance and patient safety. METHODS: A nationwide survey was conducted among 213 surgeons from 112 German hospitals in order to assess the perceived performance consequences and human factors issues of IGN, including changes of situation awareness, performance and workload, as well as issues of overreliance, skill degradation and usability. RESULTS: Generally, surgeons report improved performance and patient safety related to the use of IGN. However, issues of increased time pressure and mental demands were reported by inexperienced users. Furthermore, overreliance on IGN represents a risk, albeit only in a minority of respondents. CONCLUSIONS: IGN is evaluated as a helpful tool for surgeons. However, special care should be taken to provide surgeons with sufficient time and training during familiarization with an IGN system.

Impact of automated decision aids on performance, operator behaviour and workload in a simulated supervisory control task.

In studies reporting automation effects on overall system performance and on the operator, the methods used to measure workload often did not appropriately reflect the complexity of this construct. The present study addresses the impact of automation on operator workload and behaviour in process control fault management. Workload effects were assessed with subjective, cardiovascular and secondary task performance indicators. Interactions with the interface of the process control simulation directed at gathering information and controlling the system were recorded. Automation made operators more efficient, allowing faster fault management with less information sampling and control actions. Subjective workload ratings were significantly lower in the assisted conditions as compared to manual, which was not reflected in cardiovascular and secondary task measures. Participants' information sampling activity did not differ between medium and high level of automation. Results suggest that participants paid constantly high attention to their task even with highly automated support.

Mismatch negativity on the cone of confusion.

Localization of sounds by the auditory system is based on the analysis of three sources of information: interaural level differences (ILD, caused by an attenuation of the sound as it travels to the more distant ear), interaural time differences (ITD, caused by the additional amount of time it takes for the sound to arrive at the more distant ear), and spectral cues (caused by direction-specific spectral filter properties of the pinnae). Although in a number of psychophysiological studies cortical processes of ITD and ILD analysis were investigated, there is hitherto no evidence on the cortical processing of spectral cues for sound localization. The objective of the present experiment was to test whether it is possible to observe electrophysiological correlates of sound localization based on spectral cues. In an auditory oddball experiment, 80 ms of broadband noise from varying free field locations were presented to inattentive participants. Mismatch negativities (MMNs) were observed for pairs of standards and location deviants located symmetrically with respect to the interaural axis. As interaural time and level differences are identical for such pairs of sounds, the observed MMNs most likely reflect cognitive processes of sound localization utilizing the spectral filter properties of the pinnae. MMN latencies suggest that sound localization based on spectral cues is slower than ITD- or ILD-based localization.

Evaluation of a navigation system for ENT with surgical efficiency criteria.

The aim of this study is the evaluation of a navigation system (NaviBase) for ENT surgery. For this purpose, a new methodology for the evaluation of surgical and ergonomic system properties has been developed. The practicability of the evaluation instruments will be examined using the example of the overall assessment of the system in comparison with the current surgical standard and with other systems using clinical efficiency criteria. The evaluation is based on 102 ENT surgical applications; of these, 89 were functional endoscopic sinus surgeries (FESS). The evaluation of surgical and ergonomic performance factors was performed by seven ENT surgeons. To evaluate surgical system properties, the Level of Quality (LOQ) in 89 cases of the FESS was determined. It compares the existing information of the surgeon with that of the navigation system on a scale of 0 to 100 and with a mean value of 50 and places it in a relationship to the clinical impact. The intraoperative change of the planned surgical strategy (Change of Surgical Strategy) was documented. The ergonomic factors of the system with the categories of Overall Confidence (Trust), awareness of the situation (Situation Awareness), influence on the operating team, requirements for specific skills (Skill Set Requirement), and cognitive load (Workload Shift) were recorded for all surgical procedures as Level of Reliance (LOR). In the evaluation of the surgical system properties, an average evaluation of the quality of the information, as an LOQ of 63.59, resulted. Every second application of the navigation system (47.9%), on average, led to a change in the surgical strategy. An extension/enhancement of the indication of the endonasal approach through the use of the navigation system was shown in 7 of 102 (6.8%) cases. The completion of the resection in the FESS was rated by 74% of group I and 11% of group II as better in comparison with the standard approach. Total confidence shows a positive evaluation of 3.35 in the LOR. To supplement the evaluation of the navigation system, the technical parameters were included. The maximum deviation, Amax, of the displayed position of the reference value amounted to 1.93 mm. The average deviation was at 1.29 mm with an SD above all values, sd, of 0.29. The subsequent economic evaluation resulted in an effective average extra expenditure of time of 1.35 minutes per case. The overall evaluation of the system imparts application-relevant information beyond the technical details and permits comparability between different assistance systems.

Kanizsa subjective figures capture visual spatial attention: evidence from electrophysiological and behavioral data.

Figural binding and attention are two important processes that help to perceive the outside world. Binding is necessary to link together the different features of single objects which are represented in a distributed fashion in the brain. Attention serves to focus onto a small subset of incoming information. It is still not clear how exactly these two mechanisms operate and interact. We performed two experiments employing illusory Kanizsa figures (KFs) to investigate the temporal order of figural binding and spatial attention. In a visual search task, subjects had to detect the presence of a KF among distractor stimuli. We found only a slight increase of reaction times when increasing the number of distractors, indicating that KFs popped out and drew the perceiver's attention. In a further event-related potential (ERP) study, we used displays of the search task as non-informative cue for a subsequent target choice-reaction task. Enhanced contralateral negative amplitudes (starting at about 230 ms) over ventral occipital areas were found for cue displays which included a KF. For target stimuli, faster reaction times and enhanced ipsilateral N1 amplitudes over occipito-parietal areas were observed for validly (target presentation inside a KF) as compared to invalidly cued targets (target presentation outside a KF). Furthermore, enhanced contralateral N1 amplitudes were found for invalidly cued targets. It might be that interactions between perceptual closure processing of the ventral pathway and spatial target processing of the dorsal pathway contributed to the present result. We conclude that KFs automatically capture spatial attention when used as visual cues.

Phase-locking and amplitude modulations of EEG alpha: Two measures reflect different cognitive processes in a working memory task.

It has been demonstrated in numerous experiments that oscillatory EEG responses in the alpha frequency band (8-12 Hz) increase with memory load during the retention interval in working memory tasks. However, the findings diverge with respect to which measurement of alpha activity is influenced by memory processes. Here, we differentiate between evoked and total alpha activity in order to separate effects of phase-locking and amplitude modulation. We present data from a delayed-matching-to-sample task (S1-S2 paradigm) for which we compared EEG alpha responses between a perception and a memory condition. Increased total alpha activity was found in the retention interval for the memory as compared to the perception condition. Evoked alpha activity, however, did not differentiate between memory and perception conditions but, instead, was increased for the more complex condition of processing non-Kanizsa figures as compared to Kanizsa figures. Thus, our results demonstrate a functional differentiation between evoked and total alpha activity. While alpha phase locking seemed to be influenced mainly by task complexity, alpha amplitude clearly reflected memory demands in our paradigm.