Laser-Annealing and Solid-Phase Epitaxy of Selenium Thin-Film Solar Cells

Selenium has resurged as a promising photovoltaic material in solar cell research due to its wide direct bandgap of 1.95 eV, making it a suitable candidate for a top cell in tandem photovoltaic devices. However, the optoelectronic quality of selenium thin-films has been identified as a key bottleneck for realizing high-efficiency selenium solar cells. In this study, we present a novel approach for crystallizing selenium thin-films using laser-annealing as an alternative to the conventionally used thermal annealing strategy. By laser-annealing through a semitransparent substrate, a buried layer of high-quality selenium crystallites is formed and used as a growth template for solid-phase epitaxy. The resulting selenium thin-films feature larger and more preferentially oriented grains with a negligible surface roughness in comparison to thermally annealed selenium thin-films. We fabricate photovoltaic devices using this strategy, and demonstrate a record ideality factor of n=1.37, a record fill factor of FF=63.7%, and a power conversion efficiency of PCE=5.0%. The presented laser-annealing strategy is universally applicable and is a promising approach for crystallizing a wide range of photovoltaic materials where high temperatures are needed while maintaining a low substrate temperature

Direction of Attentional Focus in Prosthetic Training: Current Practice and Potential for Improving Motor Learning in Individuals with Lower Limb Loss

Objective: Adopting an external focus of attention has been shown to benefit motor performance and learning. However, the potential of optimizing attentional focus for improving prosthetic motor skills in lower limb prosthesis (LLP) users has not been examined. In this study, we investigated the frequency and direction of attentional focus embedded in the verbal instructions in a clinical prosthetic training setting. Methods: Twenty-one adult LLP users (8 female, 13 male; 85% at K3 level; mean age=50.5) were recruited from prosthetic clinics in the Southern Nevada region. Verbal interactions between LLP users and their prosthetists (mean experience=10 years, range=4-21 years) during prosthetic training were recorded. Recordings were analyzed to categorize the direction of attentional focus embedded in the instructional and feedback statements as internal, external, mixed, or unfocused. We also explored whether LLP users’ age, time since amputation, and perceived mobility were associated with the proportion of attentional focus statements they received. Results: We recorded a total of 20 training sessions, yielding 904 statements of instruction from 338 minutes of training. Overall, one verbal interaction occurred every 22.1 seconds. Among the statements, 63% were internal, 9% external, 3% mixed, and 25% unfocused. Regression analysis revealed that female, older, and higher functioning LLP users were significantly more likely to receive internally-focused instructions (p=0.006, 0.035, and 0.024, respectively). Conclusions: Our results demonstrate that verbal instructions and feedback are frequently provided to LLP users during prosthetic training. Most verbal interactions are focused internally on the LLP users’ body movements and not externally on the intended movement effects. Impact Statement: While more research is needed to explore how motor learning principles may be applied to improve LLP user outcomes, clinicians should consider adopting the best available scientific evidence during treatment. Overreliance on internally-focused instructions as observed in the current study may hinder prosthetic skill learning

Experiences of baby-led weaning: trust, control, and renegotiation

Baby-led weaning (Rapley 2013) is an approach to introducing solid foods that relies on the presence of self-feeding skills and is increasing in popularity in the UK and New Zealand. This study aimed to investigate the reported experiences and feelings of mothers using a BLW approach in order to better understand the experiences of the mother and infant, the benefits and challenges of the approach, and the beliefs which underpin these experiences. 15 UK Mothers were interviewed over the course of a series of five emails using a semi-structured approach. The email transcripts were anonymised and analysed using thematic analysis (Braun & Clarke 2006). There were four main themes which were identified from the analysis: i) Trusting the child, ii) Parental control and responsibility, iii) Precious milk and, iv) Renegotiating baby-led weaning. The themes identified reflect a range of different ideals and pressures that this group of mothers tried to negotiate in order to provide their infants with a positive and healthy introduction to solid foods. One of the key issues of potential concern is the timing at which some of the children ingested complementary foods. Although complementary foods were made available to the infants at 6 months of age, in many cases they were not ingested until much later. These findings have potentially important implications for mother’s decision-making, health professional policy and practice, and future research

Laser-induced saturated fluorescence as a method for the determination of radical concentrations in flames

Kohse-Höinghaus K, Perc W, Just T. Laser-induced saturated fluorescence as a method for the determination of radical concentrations in flames. Berichte der Bunsen-Gesellschaft. 1983;87:1052-1057

Development of temperature imaging using two-line atomic fluorescence

This work aims to advance understanding of the coupling between temperature and soot. The ability to image temperature using the two-line atomic fluorescence (TLAF) technique is demonstrated. Previous TLAF theory is extended from linear excitation into the nonlinear fluence regime. Nonlinear regime two-line atomic fluorescence (NTLAF) provides superior signal and reduces single-shot uncertainty from 250 K for conventional TLAF down to 100 K. NTLAF is shown to resolve the temperature profile across the stoichiometric envelope for hydrogen, ethylene, and natural gas flames, with deviation from thermocouple measurements not exceeding 100 K, and typically ≲30 K. Measurements in flames containing soot demonstrate good capacity of NTLAF to exclude interferences that hamper most two-dimensional thermometry techniques.Paul R. Medwell, Qing N. Chan, Peter A. M. Kalt, Zeyad T. Alwahabi, Bassam B. Dally, and Graham J. Natha

Radon intercomparison tests – Katowice, 2016

At the beginning of the year 2016, the representatives of the Polish Radon Centre decided to organize profi ciency tests (PTs) for measurements of radon gas and radon decay products in the air, involving radon monitors and laboratory passive techniques. The Silesian Centre for Environmental Radioactivity of the Central Mining Institute (GIG), Katowice, became responsible for the organization of the PT exercises. The main reason to choose that location was the radon chamber in GIG with a volume of 17 m3, the biggest one in Poland. Accordingly, 13 participants from Poland plus one participant from Germany expressed their interest. The participants were invited to inform the organizers about what types of monitors and methods they would like to check during the tests. On this basis, the GIG team prepared the proposal for the schedule of exercises, such as the required level(s) of radon concentrations, the number and periods of tests, proposed potential alpha energy concentration (PAEC) levels and also the overall period of PT. The PT activity was performed between 6th and 17th June 2016. After assessment of the results, the agreement between radon monitors and other measurement methods was confi rmed. In the case of PAEC monitors and methods of measurements, the results of PT exercises were consistent and confi rmed the accuracy of the calibration procedures used by the participants. The results of the PAEC PTs will be published elsewhere; in this paper, only the results of radon intercomparison are described