Extrinsic Point Defects in Low-Positive Thermal Expansion Al2W3O12 and Their Effects on Thermal and Optical Properties.

A2M3O12-type ceramics are potentially useful in a variety of applications due to their peculiar thermal and mechanical properties. In addition, their intrinsic coefficients of thermal expansion can be finely tuned through different mechanisms. Despite the great influence of extrinsic point defects on physical properties, only a few reports have dealt with their relationship to thermal expansion and thermal conductivity. Extrinsic oxygen vacancies in orthorhombic Al2W3O12, in different concentrations, were formed through heat treatments in argon or hydrogen atmospheres. X-ray powder diffraction, diffuse reflectance spectroscopy, and Raman and electron paramagnetic resonance spectroscopies were used to study the as-formed vacancies, and X-ray photoelectron spectroscopy was employed to propose a charge compensation mechanism. It was found that the intrinsic coefficient of thermal expansion of orthorhombic Al2W3O12 was severely affected by extrinsic oxygen vacancies. Thermal expansion was decreased up to 40% (from 25 to 400 °C) with respect to the extrinsic-point-defect-free counterpart. Unit-cell volumes of defective orthorhombic Al2W3O12 were larger, while their W-O bonds were weaker, likely leading to higher lattice flexibility and enhanced low-energy transverse acoustic modes. Extrinsic oxygen vacancies could be an additional mechanism for fine-tuning the intrinsic coefficients of thermal expansion in A2M3O12-type ceramics and in other framework structures built through two or threefold linkages.

Crystal Structure and Properties of Imidazo-Pyridine Ionic Liquids.

Computational studies were performed on novel protic ionic liquids imidazolium-[1,2-a]-pyridine trifluoroacetate [ImPr][TFA] synthesized by the reaction of imidazo-[1,2a]-pyridine (ImPr) with trifluoroacetic acid (TFA), and on fused salt imidazolium-[1,2-a]-pyridine maleamic carbonate [ImPr][Mal] synthesized by reaction of ImPr with maleamic acid (Mal). Synthesis was performed as one-pot reactions, which applies green chemistry tenets. Both these compounds begin to decompose at 180°C. Our computational studies suggest another thermal reaction channel, in which [ImPr][Mal] can also thermally polymerizes to polyacrylamide which then cyclizes. This is thermal product remains stable up to 700 degrees, consistent with our thermogravimetric studies. [ImPr][TFA] exhibited good conductivity and ideal ionic behavior, as evaluated by a Walden plot. X-ray crystallography of [ImPr][TFA] revealed a tightly packed system for the crystals as a result of strong ionic interaction, pi-stacking, and fluorine-CH interactions. Both synthesized compounds exhibited some CO2 absorptivity, with [ImPr][Mal] outperforming [ImPr][TFA] in this regard. The quantum chemistry based computational methods can shed light on many properties of these ionic liquids, but they are challenged in fully describing their ionic nature. © 2017 Wiley Periodicals, Inc.

Quantitative feature analysis of continuous analytic wavelet transforms of electrocardiography and electromyography.

Theoretical and practical advances in time-frequency analysis, in general, and the continuous wavelet transform (CWT), in particular, have increased over the last two decades. Although the Morlet wavelet has been the default choice for wavelet analysis, a new family of analytic wavelets, known as generalized Morse wavelets, which subsume several other analytic wavelet families, have been increasingly employed due to their time and frequency localization benefits and their utility in isolating and extracting quantifiable features in the time-frequency domain. The current paper describes two practical applications of analysing the features obtained from the generalized Morse CWT: (i) electromyography, for isolating important features in muscle bursts during skating, and (ii) electrocardiography, for assessing heart rate variability, which is represented as the ridge of the main transform frequency band. These features are subsequently quantified to facilitate exploration of the underlying physiological processes from which the signals were generated.This article is part of the theme issue 'Redundancy rules: the continuous wavelet transform comes of age'.

Biomechanical investigation of prolonged driving in an ergonomically designed truck seat prototype.

A postural evaluation during a prolonged driving task was conducted to determine the ergonomic validity of a new freely adjustable truck seat prototype. Twenty participants were recruited to perform two 2-h simulated driving sessions. Postures were assessed using motion capture, accelerometers and pressure pads. Subjective discomfort was also monitored in 15-min increments using ratings of perceived discomfort (RPD) and the Automotive Seating Discomfort Questionnaire. Participants had a more neutral spine posture during the first hour of the drive and reported lower RPDs while sitting in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan helped reduce the average sitting pressure. The industry-standard truck seat may lead to the development of poor whole body posture, and the proposed ergonomic redesign of a new truck seat helped improve sitting posture and reduce perceived discomfort. Practitioner Summary: A new freely adjustable truck seat prototype was compared to an Industry standard seat to assess hypothesised improvements to sitting posture and discomfort for long haul driving. It was found that the adjustable panels in the prototype helped promote spine posture, reduce sitting pressure and improved discomfort ratings.

Origins of ultralow thermal conductivity in bulk [6,6]-phenyl-C61-butyric acid methyl ester (PCBM).

Bulk PCBM has exceptionally low thermal conductivity, 0.07 W m(-1) K(-1) at room temperature. We show that its ultralow thermal conductivity is an intrinsic property. Based on results for thermal conductivity and heat capacity measurements down to <2 K, along with Raman spectroscopy and dilatometry, a new model for minimum thermal conductivity was developed. In the model the thermal energy is transferred between entities of phonons oscillating in a range of frequencies, and limited by the atomic density and the phonon mean speed. The model accurately represents the low thermal conductivity for both PCBM and C60/C70.

Determination of phase stability of elemental boron.

Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or ß) is stable at ambient conditions. Through experiment, we quantify the relative stability of α-boron and ß-boron as a function of temperature. The ground-state energies of α-boron and ß-boron are nearly identical. For all temperatures up to 2000 K, the complicated ß-boron structure is more stable than the simpler α-boron structure at ambient pressure. Below 1000 K, ß-boron is entropically stabilized with respect to α-boron owing to its partially occupied sites, whereas at higher temperatures ß-boron is enthalpically stabilized with respect to α-boron. We show that α-boron only becomes stable on application of pressure.

Investigating the autonomic nervous system and cognitive functions as potential mediators of an association between cardiovascular disease and driving performance.

Cardiovascular disease (CVD) impacts the autonomic nervous system and cognitive functions related to activities of daily living, including driving an automobile. Although CVD has been linked to unsafe driving, mechanisms underlying this relationship remain elusive. The aim of this study was to examine the role of cognitive functions and the autonomic nervous system as potential mediators of driving performance. Nineteen individuals having recently suffered a cardiac event and 16 individuals with no history of CVD completed a simulated drive using a STISIM simulator to assess driving performance. Heart rate was recorded throughout testing using a Polar RS800CX heart rate monitor, and measures of executive, orienting, and alerting functions were obtained through the Attention Network Test. We used the Baron and Kenny analysis method to assess potential mediating effects of the relationship between CVD and driving performance. Executive function was the only potential mediator investigated to be associated with driving (p < 0.01) and CVD (p < 0.05); however, it did not appear to play a mediating role (p = 0.28). These results suggest that individuals with CVD exhibit decrements in complex cognitive tasks such as driving and that further research is needed to better understand the mechanisms underlying this relationship.

Relationship between occupational stress injury score and simulated patient-care scenario performance among experienced paramedics.

BACKGROUND: It is well-known that psychosocial health status of paramedics may be altered by their job demands. However, it is unknown whether psychosocial health status can affect occupational performance. OBJECTIVE: The goal of this study was to explore whether a paramedic's symptom severity of Occupational Stress Injury (OSI) was related to simulated patient-care performance. METHODS: Nineteen paramedics with 15.0±8.7 years of paramedic experience participated in this study. Participants completed both an OSI symptom severity questionnaires, and a patient-care simulation. Vagal activity was also collected during the patient-care simulation. The simulation was used to assess experienced paramedics in a realistic stressful setting. Based on the provincial standard in New Brunswick, an experienced paramedic instructor graded the patient-care simulation using the provincial standard charts, observing performance videos and assessing data from the manikin. RESULTS: The current study suggests that paramedics who self-reported elevated symptoms of OSI were less likely to successfully complete the simulated patient-care scenario. CONCLUSION: This research suggests that the presence of self-reported elevated symptoms of OSI negatively impacts paramedics' performance during a stressful work task simulation. Therefore, to help paramedics maintain optimal performance, it may be important to ensure that paramedics have access to appropriate resources to monitor and improve their psychosocial health.

Phase Transition and Coefficients of Thermal Expansion in Al2-xInxW3O12 (0.2 ≤ x ≤ 1).

Materials from theA2M3O12 family are known for their extensive chemical versatility while preserving the polyhedral-corner-shared orthorhombic crystal system, as well as for their consequent unusual thermal expansion, varying from negative and near-zero to slightly positive. The rarest are near-zero thermal expansion materials, which are of paramount importance in thermal shock resistance applications. Ceramic materials with chemistry Al2-xInxW3O12 (x = 0.2-1.0) were synthesized using a modified reverse-strike co-precipitation method and prepared into solid specimens using traditional ceramic sintering. The resulting materials were characterized by X-ray powder diffraction (ambient and in situ high temperatures), differential scanning calorimetry and dilatometry to delineate thermal expansion, phase transitions and crystal structures. It was found that the x = 0.2 composition had the lowest thermal expansion, 1.88 × 10-6 K-1, which was still higher than the end member Al2W3O12 for the chemical series. Furthermore, the AlInW3O12 was monoclinic phase at room temperature and transformed to the orthorhombic form at ca. 200 °C, in contrast with previous reports. Interestingly, the x = 0.2, x = 0.4 and x = 0.7 materials did not exhibit the expected orthorhombic-to-monoclinic phase transition as observed for the other compositions, and hence did not follow the expected Vegard-like relationship associated with the electronegativity rule. Overall, compositions within the Al2-xInxW3O12 family should not be considered candidates for high thermal shock applications that would require near-zero thermal expansion properties.

Novel method to produce single-walled carbon nanotube films and their thermal and electrical properties.

Single-walled carbon nanotube films are promising candidates for applications requiring transparent conductors due to their low sheet resistance and high transparency in the visible region. Vacuum filtration is a common and easy to implement technique to produce such films but it is complicated by the need to transfer the films to desired substrates. Here we report conditions under which single-walled carbon nanotube films produced by vacuum filtration detach from the filter membrane upon submersion into water, providing a facile method to transfer filtration-produced nanotube films to desired substrates. Sheet resistance and transparency measurements show that these films are competitive with other high conductivity films made through more cumbersome procedures. Films post-treated with nitric acid or made with acid pre-treated nanotubes have superior performance to those made with high-purity nanotubes without any acid treatment. Thermal imaging by scanning thermal microscopy indicates that heat dissipation by the film is comparable to that of a glass substrate.

Physiological responses during paramedics' simulated driving tasks.

BACKGROUND: Most ambulance collisions happen in emergency driving conditions and are caused by human factors. OBJECTIVE: This study investigated the influence of human factors associated with time pressure, patient-care intervention, and health status on the physiological responses of simulated emergency driving tasks. METHODS: A cohort of seventeen experienced paramedics performed a battery of three simulated diving tasks. The driving tasks were a non-urgent and two urgent driving simulations (one to the scene and one to the hospital). The second urgent driving task was preceded by a patient-care simulation (unstable cardiac patient with cardiopulmonary resuscitation). RESULTS: The physiological responses between the three driving tasks were not significantly different due to time pressure and patient-care intervention. It is postulated that the physiological response of experienced paramedics was influenced by the fact that they are accustomed to handling stressful situations daily. Furthermore, it was observed that paramedics with health conditions were more physiologically aroused during the urgent driving scenarios (pre and post-intervention), suggesting they might have an elevated risk of collision when they drive with urgency. Paramedics with health conditions also had higher physiological responses for the post-intervention baseline, leading to a longer recovery time period, which might represent an elevated risk of developing chronic health problems or amplifying existing ones. CONCLUSIONS: The findings of this research suggest that experienced paramedics manage the influence of time pressure and the impact of challenging patient-care well. Paramedics with health conditions represent an elevated risk of collision.

Exploration of the health status of experienced New Brunswick paramedics.

BACKGROUND: Literature reports that paramedics represent an at-risk occupation for the development of health problems. At least half of the paramedic population presents at least one risk factor associated with a negative health condition. These reports may suffer a "mono-method bias" where most reported outcomes are based on a single screening tool approach (may attenuate or inflate the prevalence). OBJECTIVE: The current study characterizes the health status of a cohort of twenty-five experienced New Brunswick (Canadian province) paramedics. METHODS: To understand possible limitations of past research, health status was characterized using four different methods: two methods using only one health measure and two were combined methods, integrating outcomes from at least two health measures to determine the prevalence of a given health status. RESULTS: Mono-bias was observed when using the single health measure methods. The difference among the four methods highlighted that a third of the cohort seemed unaware of their health condition. This result shed additional light on paramedics' health, where a high proportion of paramedics worked without knowledge of their health conditions. Based on a two health measures combined method, it was observed that only two-fifths of the current sample had no health conditions or could otherwise be considered as a "healthy". CONCLUSIONS: Because the literature has focused on single screening methods, our results were difficult to compare. However, there was a consensus that paramedics represent an at-risk occupation comprised of health problems. This study was exploratory and should be the basis for further research.

Occupational health profile of Canadian Maritimes truck drivers.

BACKGROUND: There are over 12,000 professional truck drivers in the Canadian Maritime provinces, with the majority being in New Brunswick and Nova Scotia. Previous studies have focused on the health of Canadian and American truck drivers but the occupational health status of truck drivers in the Maritime Provinces remains undocumented. OBJECTIVE: The objective of this cross-sectional study was to provide a general, occupational health and demographic characteristics description of professional truck drivers in the Maritimes. METHODS: One-hundred and four male truck drivers from the Canadian Maritime Provinces volunteered for this study. Nine occupational health indicators were measured (seven were self-reported via questionnaire and two were physical measurements). Participants self-reported their age, years of truck driving experience and education. RESULTS: Only one-quarter of the current sample had no health conditions. In contrast, more than half were obese, one third had back problems, and one-sixth had a high risk of developing cardiovascular disease (CVD). The group comparison analysis showed that the group without health condition was younger and more educated than the group with multiple health conditions. For this study, age and low rate of education were associated with an increased number of health conditions. CONCLUSIONS: Similar to health profiles of other populations of North American truck drivers, this study suggests that the majority of truck drivers in the Canadian Maritime Provinces have at least one poor indicator of occupational health.

A pre/post evaluation of fatigue, stress and vigilance amongst commercially licensed truck drivers performing a prolonged driving task.

Purpose. The main purpose of this research study was to evaluate changes in fatigue, stress and vigilance amongst commercially licensed truck drivers involved in a prolonged driving task. The secondary purpose was to determine whether a new ergonomic seat could help reduce both physical and cognitive fatigue during a prolonged driving task. Two different truck seats were evaluated: an industrial standard seat and a new truck seat prototype. Methods. Twenty male truck drivers were recruited to attend two testing sessions, on two separate days, with each session randomized for seat design. During each session, participants performed two 10-min simulated driving tasks. Between simulated sessions, participants drove a long-haul truck for 90 min. Fatigue and stress were quantified using a series of questionnaires whereas vigilance was measured using a standardized computer test. Results. Seat interactions had a significant effect on fatigue patterns. Conclusion. The new ergonomic seat design holds potential in improving road safety and vehicle accidents due to fatigue-related accidents.

Exploring simulated driving performance among varsity male soccer players.

Background: It is documented that male athletes display riskier behaviors while driving (as well as in life in general) than female athletes and nonathletes. However, the literature has reported that athletes show better driving ability than nonathletes. This paradox between behaviors and abilities motivated the present study to further understand the collision risk of varsity athletes. Objective: The current study estimates the performance differences between varsity male soccer players and male undergraduate nonathletes on (1) a driving task and (2) three perceptual-cognitive tasks (associated with collision risk prediction; i.e., Useful Field of View [UFOV] test). Methods: Thirty-five male undergraduate students (15 varsity soccer players, 20 undergraduate nonathletes) took part in this study. Driving performance was assessed during 14 min of urban commuting using a driving simulator. While completing the simulated driving task and UFOV test, the physiological responses were monitored using an electrocardiograph (ECG) to document heart rate variability (HRV). Results: Varsity soccer players showed more risky behaviors at the wheel compared to their nonathlete student peers. Varsity soccer players spent more time over the speed limit, committed more driving errors, and adopted fewer safe and legal behaviors. However, no difference was observed between both groups on driving skill variables (i.e., vehicle control, vehicle mobility, ecodriving). For subtests 1 and 2 of the UFOV (i.e., processing speed, divided attention), both groups performed identically (i.e., 17 ms). The nonathlete group tended to perform better on the selective attention task (i.e., subtest 3 of UFOV test; 63.2 ± 6.2 ms vs. 87.2 ± 10.7 ms, respectively; this difference was not significant, P = .76). Conclusion: Preventive driving measures should be enforced in this high-risk population to develop strategies for risk reduction in male team athletes.

Data supporting micromechanical models for the estimation of Young's modulus and coefficient of thermal expansion of titanate nanotube/Y2W3O12/HDPE ternary composites.

This article presents several micromechanical models to predict the Young's modulus and the coefficient of thermal expansion of titanate nanotube/Y2W3O12/HDPE composites. The equations and assumptions of the selected micromechanical models are described in detail for this ternary system. Data of the elastic constants, coefficient of thermal expansion of composite components and other associated parameters, obtained either by literature survey or processing of literature information, are compiled in this work. For further interpretation of the data presented in this article, please see our research article entitled "The effect of titanate nanotube/Y2W3O12 hybrid fillers on mechanical and thermal properties of HDPE-based composites" (Pontón et al., 2019).

Ergonomic evaluation of a new truck seat design: a field study.

A postural evaluation of commercial licensed truck drivers was conducted to determine the ergonomic benefits of a truck seat prototype in comparison with an industry standard seat. Twenty commercially licensed truck drivers were recruited to perform a 90-min driving task. Postures were assessed using accelerometers and a backrest and seat pan pressure mapping system. Subjective discomfort measurements were monitored using two questionnaires: ratings of perceived discomfort (RPD) and the automotive seating discomfort questionnaire (ASDQ). Participants reported significantly higher discomfort scores when sitting in the industry standard seat. Participants sat with more lumbar lordosis and assumed a more extended thoracic posture when seated in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan also helped reduce the average sitting pressure on both the seat pan and the backrest. The prototype provided several postural benefits for commercially certified truck drivers, as it did for a young and healthy population.

'How deep are your pockets?' Autoethnographic reflections on the cost of raising a child with autism.

BACKGROUND: In this article, we reflected on our experience of the cost of parenting a child with autism, including our ongoing search for educational and therapeutic intervention. OBJECTIVES: We aimed to give an academic insight into the state of autism education and care in South Africa as seen by us, with special attention to its cost and sustainability. METHODS: Using evocative autoethnography as storied scholarship together with critical autism studies, we reflected on stories of the past 5 years since our son's diagnosis. RESULTS: Our experiences agree with international studies that establish autism as the most expensive disability. In addition to the high costs of diagnosis, existing intervention and support approaches are unaffordable for the majority of South Africans. We recommend that teachers should be trained to participate in early screening and diagnosis, as well as co-therapists, to strengthen the implementation of inclusive education. CONCLUSION: The kind of autism intervention currently offered in South Africa is financially and socially unsustainable. Instead of positioning autism as an individual or family dilemma, it should be addressed as an educational and societal issue. Future research should explore cost-effective options for a developing country context, while promoting best practice within inclusive settings.

Assessing heart rate variability through wavelet-based statistical measures.

Because of its utility in the investigation and diagnosis of clinical abnormalities, heart rate variability (HRV) has been quantified with both time and frequency analysis tools. Recently, time-frequency methods, especially wavelet transforms, have been applied to HRV. In the current study, a complementary computational approach is proposed wherein continuous wavelet transforms are applied directly to ECG signals to quantify time-varying frequency changes in the lower bands. Such variations are compared for resting and lower body negative pressure (LBNP) conditions using statistical and information-theoretic measures, and compared with standard HRV metrics. The latter confirm the expected lower variability in the LBNP condition due to sympathetic nerve activity (e.g. RMSSD: p=0.023; SDSD: p=0.023; LF/HF: p=0.018). Conversely, using the standard Morlet wavelet and a new transform based on windowed complex sinusoids, wavelet analysis of the ECG within the observed range of heart rate (0.5-1.25Hz) exhibits significantly higher variability, as measured by frequency band roughness (Morlet CWT: p=0.041), entropy (Morlet CWT: p=0.001), and approximate entropy (Morlet CWT: p=0.004). Consequently, this paper proposes that, when used with well-established HRV approaches, time-frequency analysis of ECG can provide additional insights into the complex phenomenon of heart rate variability.

Effects of an aerobic exercise program on driving performance in adults with cardiovascular disease.

Cardiovascular disease (CVD) has been linked to decreases in driving performance and an increased crash risk. Regular exercise has been linked to improved driving performance among healthy adults. The aim of the current study was to investigate the relationship between a 12-week cardiac rehabilitation (CR) program and driving performance among individuals with CVD. Twenty-five individuals, including 12 cardiac adults and 13 healthy adults, took part in this study. Simulated driving performance was assessed using a standardized demerit-based scoring system at 0 and 12 weeks. Cardiac participants completed a 12-week CR program between evaluations. At baseline, cardiac participants had a higher number of demerit points than healthy adults (120.9±38.1 vs. 94.7±28.3, P=0.04). At follow-up, there was an improvement in both groups' driving evaluations, but the improvement was greater among the cardiac group such that there was no longer a difference in driving performance between both groups (94.6±30 vs. 86.9±34.8, P=0.51). Participation in an aerobic exercise-based CR program appears to lead to improvements in simulated driving performances of individuals with CVD.