Search

Different electrical and thermoelectric properties of a Si-based thermoelectric generator (TEG) are described based on the Kubo–Greenwood formalism. Temperature and doping dependence, phonon scattering (acoustic and optical phonons), and scattering on impurities are included. Comparisons with experimentally verified data confirm the validity of the model. Experimental studies were carried out on a micromechanically fabricated TEG. Devices were realized using a standard CMOS SOI technology in a lateral geometry. All thermopiles are located on a thin membrane to reduce the heat flow. The thickness of the membrane was adjusted between 20 and 30 µm ensuring also sufficient mechanical stability. Measurements on individual devices confirm the results of the theoretical model. The Seebeck coefficient was calculated and experimentally measured as S = 0.5 mV/K at an acceptor level of 1019 cm−3 at room temperature. The power factor is S2 · σ = 0.0073 W/mK2. [ABSTRACT FROM AUTHOR]

Musculoskeletal disorders (MSDs) are the main cause of pain leading to high economic burden and psychosocial disadvantages. In addition, psychological stress impacts the overall health as well as the quality of life. Elementary school teachers clearly are a cohort with a high risk of MSDs and stress. The 'BelaPrim' study was conducted to determine the physical and psychological conditions of elementary school teachers in Upper Austria and to investigate the influence of physical and psychological parameters on MSDs. Physical and mental strain was determined with the Nordic Musculoskeletal Questionnaire (NMQ) and the 11-item short version of a German work-related behaviour and experience assessment (AVEM), respectively. Despite a high prevalence of MSDs, high scores were found on personality dimensions. Furthermore, qualitative results indicated the need of administrative/pedagogical support. A linear regression model showed that body height (+), work engagement (+), and emotions (−) are predictors for the occurrence of back pain. Practitioner summary: Despite a high proportion of physical complaints, Upper Austrian elementary school teachers show good mental health. Body height, a high work engagement, and low level of emotions are predictors for the occurrence of back pain. Health initiatives for elementary schools should have a multifactorial view to improve teachers' health. Abbreviations: BA: professional ambition; BE: willingness to spend; VB: striving for perfection PE: ability to distance; DF: tendency to resign in case of failure; RT: offensive problem-solving: OP; inner calm and balance; IR: experiencing success at work; EE: life satisfaction; LZ and SU: experiencing social support [ABSTRACT FROM AUTHOR]

Implementing sit/stand workstations in sedentary work environments is a common way to reduce sedentary time, but their medium-term effect on cognitive performance is unclear. To address this circumstance, eighteen office workers participated in a two-arm, randomised controlled cross-over trial (ClinicalTrials.gov Identifier: NCT02825303), either working at a traditional (sit) or an interventional (sit/stand) workplace for 23 weeks. Cognitive performance (working speed, reaction time, concentration performance, accuracy), workload and relevant covariates (salivary cortisol level, heart rate, physical activity, sitting time) were measured pre- and post-intervention under laboratory conditions. MANOVA and RMANOVA results did not show differences in performance parameters and workload, respectively, between sit/stand and traditional workplace users. Differences in text editing accuracy and cortisol levels for sit/stand workstation users indicate potential connectivity to cognitive parameters which should be further examined with large-scale studies. Practitioner summary: Medium-term effects of working at sit/stand workstations on cognitive performance and workload are unexplored. This randomised controlled trial suggests that cognitive performance and workload are unaffected for sit/stand workstation users after 23 weeks of use. However, accuracy appeared to improve and physiological stress appeared to be altered. Abbreviations: BMI: body mass index; IPAQ: International physical activity questionnaire; MET: metabolic equivalent of task; MANOVA: multivariate ANOVA; NASA TLX: NASA task load index; RMANOVA: repeated measures ANOVA [ABSTRACT FROM AUTHOR]

Prolonged sitting is a risk factor for several diseases and the prevalence of worksite-based interventions such as sit-to-stand workstations is increasing. Although their impact on sedentary behaviour has been regularly investigated, the effect of working in alternating body postures on cognitive performance is unclear. To address this uncertainty, 45 students participated in a two-arm, randomised controlled cross-over trial under laboratory conditions. Subjects executed validated cognitive tests (working speed, reaction time, concentration performance) either in sitting or alternating working postures on two separate days (ClinicalTrials.gov Identifier: NCT02863731). MANOVA results showed no significant difference in cognitive performance between trials executed in alternating, standing or sitting postures. Perceived workload did not differ between sitting and alternating days. Repeated measures ANOVA revealed significant learning effects regarding concentration performance and working speed for both days. These results suggest that working posture did not affect cognitive performance in the short term. Practitioner Summary: Prior reports indicated health-related benefits based on alternated (sit/stand) body postures. Nevertheless, their effect on cognitive performance is unknown. This randomised controlled trial showed that working in alternating body postures did not influence reaction time, concentration performance, working speed or workload perception in the short term. [ABSTRACT FROM AUTHOR]

Electroluminescence (EL) of light-emitting diodes (LED) with different active regions and photoluminescence (PL) of Ge layers embedded in Si barriers on Si substrates has been studied. Increasing the tensile strain in the active region of Ge LEDs by using GeSn virtual substrate technology leads to an enhancement of the direct band luminescence. An intensity increase by a factor of four is achieved due to n-type doping with an antimony concentration of 3 × 1019 cm−3. The EL of LEDs with a GeSn/Ge multi quantum well structure as active region show an increased direct band luminescence of GeSn by a factor of 16 compared to an intrinsic Ge LED, revealing the advantage of carrier confinement. A high density of threading dislocations, due to the lattice mismatch of Ge and Si, causes a huge drop of PL intensity in the range of one to two orders of magnitude in the temperature range from 80 to 350 K. Thin and pseudomorphically grown Ge layers between Si barrier layers exhibit a huge PL intensity due to the absence of threading dislocations. Taking into account the thickness of the active region the direct band luminescence intensity is increased by two orders of magnitude. [ABSTRACT FROM AUTHOR]

Background: Prolonged sitting is ubiquitous in modern society and linked to several diseases. Height-adjustable desks are being used to decrease worksite based sitting time (ST). Single-desk sit-to-stand workplaces exhibit small ST reduction potential and short-term loss in performance. The aim of this paper is to report the study design and methodology of an ACTIVE OFFICE trial.Design: The study was a 1-year three-arm, randomized controlled trial in 18 healthy Austrian office workers. Allocation was done via a regional health insurance, with data collection during Jan 2014 - March 2015. Participants were allocated to either an intervention or control group. Intervention group subjects were provided with traditional or two-desk sit-to-stand workstations in either the first or the second half of the study, while control subjects did not experience any changes during the whole study duration. Sitting time and physical activity (IPAQ-long), cognitive performance (text editing task, Stroop-test, d2R test of attention), workload perception (NASA-TLX) and physiological parameters (salivary cortisol, heartrate variability and body weight) were measured pre- and post-intervention (23 weeks after baseline) for intervention and control periods. Postural changes and sitting/standing time (software logger) were recorded at the workplace for the whole intervention period.Discussion: This study evaluates the effects of a novel two-desk sit-to-stand workplace on sitting time, physical parameters and work performance of healthy office based workers. If the intervention proves effective, it has a great potential to be implemented in regular workplaces to reduce diseases related to prolonged sitting.Trial Registration: ClinicalTrials.gov Identifier: NCT02825303 , July 2016 (retrospectively registered). [ABSTRACT FROM AUTHOR]

Antimony-doped Ge-LEDs were subjected to electroluminescence studies at temperatures about 300 K and 80 K. The LEDs were grown on Si substrates by MBE. The thickness of the active layer was 300 nm. For the p+nn+-LEDs the Sb concentrations were 1 × 1018, 1 × 1019, 3 × 1019, 4 × 1019, 7 × 1019 or 1 × 1020 cm-3, respectively. As reference a p+in+-LED without intentional doping in the active layer was used. The investigated specimen exhibited dominance of the direct transition line at about 0.8 eV. Moreover, luminescence indirect transition was observed. In general, the spectra reveal higher EL intensities at room temperature as compared to 80 K. With decreasing temperature the direct peak was blue shifted. The highest EL intensity was found for the LED with Sb concentration of 3 × 1019 cm-3. With increasing Sb doping a red-shift of the direct peak was observed, caused by band gap narrowing. In addition, a simulated curve of the direct transition was compared with our samples and fits well with the measured spectra. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Experimental observations and quantum mechanical device simulations point to different electronic properties of dislocations in silicon and germanium. The experimental data suggest a supermetallic behavior of the dislocations in Si and thus the high strain in the dislocation core is thought to cause the confinement of the charge carriers, which leads to the formation of a 1D electron gas along a dislocation (quantum wire). The resulting significant increase in the electron concentration corresponds to a marked increase in the drain current of metal–oxide–semiconductor field‐effect transistor (MOSFET). The specific resistance of an individual dislocation in Ge is about nine orders of magnitude higher than for a dislocation in Si. The experimental measurements of the strain in dislocation cores in Ge are still missing. Based on the band structure data, the generation of a strain equivalent to that of the dislocation cores in Si appears to be very challenging because of the transition from an indirect into a direct semiconductor with about tenfold lower strain levels. The lower strain in the dislocation core in germanium may not support the carrier confinement as proposed for the dislocation core of silicon, and consequently 1D electron gases are not expected to form along the dislocations in Ge. [ABSTRACT FROM AUTHOR]