Mapping lightning in the sky with a mini array

Mini arrays are commonly used for infrasonic and seismic studies. Here we report for the first time the detection and mapping of distant lightning discharges in the sky with a mini array. The array has a baseline to wavelength ratio $\sim$4.2 ${ \cdot}$ $10^{-2}$ to record very low frequency electromagnetic waves from 2 to 18 kHz. It is found that the mini array detects $\sim$69 lightning pulses per second from cloud-to-ground and in-cloud discharges, even though the parent thunderstorms are $\sim$900-1100 km away and a rigorous selection criterion based on the quality of the wavefront across the array is used. In particular, lightning pulses that exhibit a clockwise phase progression are found at larger elevation angles in the sky as the result of a birefringent subionospheric wave propagation attributed to ordinary and extraordinary waves. These results imply that long range lightning detection networks might benefit from an exploration of the wave propagation conditions with mini arrays

Evolving the Landscape of Polymer Laser Powder Bed Fusion:Expanding Frontiers in Process and Materials

Laser Based Powder Bed Fusion of Polymers (PBF-LB/P) is one of the pioneering Additive Manufacturing (AM) processes, using a laser to selectively consolidate a powder feedstock into threedimensional (3D) components. The technique functions by depositing a thin layer of powder in the build plane of the system, laser scanning the cross-sectional area of the geometry, and repeating this cycle in a layer-by-layer fashion to fabricate a component. This allows the production of complex geometries unattainable by conventional processing while inheriting mechanical properties resembling those of traditional plastic fabrication. Conventional PBF-LB/P systems utilise a CO2 laser to consolidate the powder. This study aims to investigate the utility of a fibre laser source for processing polymer powders. The functionality of the fibre laser in the process was extensively studied through three primary investigations. The first study focuses on developing the relevant process knowledge and understanding of laser processing of polymer powders, describing the critical influential factors for developing an experiment capable of defining the fibre laser utility. The second investigation relates the critical elements of the first study, delivering an experimental infrastructure designed for testing the main hypothesis. The third and final exploration establish the functionality of the fibre laser in the process, utilising the laser source in the experimental infrastructure for producing components, which were scrutinised concerning the success of the production.To investigate the fibre laser utility in the process, an open architecture system is constructed. The open architecture allows access to all relevant process settings and parameters. This is achieved by utilisation of the tools developed throughout the Open Additive Manufacturing Initiative, presenting the open architecture for several industrially relevant AM processes. The main driver and hindrance for fibre laser processing of polymers is the wavelength of 1080 nm,delivered by the laser. This wavelength does not match the agitation frequency of the polymer constituent elements or compounds, leading to low energy absorption by the polymer. The wavelength, however, allows for the small spot size and considerable Rayleigh length of the laser. A metric for the requirement of an optical absorber was examined and quantified by fibre laser processing polymer powder, utilising the experimental infrastructure. The study investigated the use of two different coloured powders of the same type of PA11 polymer, where one is the pure white type, and the other contains the optical absorption quality by being coloured black. A minimum concentration of 5% black powder in a mix of white and black is sufficient for producinghigh-fidelity components. From the exploration of the utility of fibre lasers in PBF-LB/P, it is concluded that the laser source can deliver satisfactory detail resolution, comparable to what is found in the industry. The fibre laser aid the utilisation by providing key parameters not offered by the conventional CO2 laser source. These are the ease of beam delivery, high beam quality, and considerable Rayleigh length, enabling the fine details achieved herein. <br/

Barriers and enablers to promoting grandchildren’s physical activity and reducing screen time: a qualitative study with Australian grandparents

Abstract Background With an increasing number of grandparents providing care to their grandchildren, calls have been made for these caregivers to be considered important stakeholders in encouraging children’s engagement in health-promoting behaviors, such as physical activity. Understanding the perspectives of grandparents who provide care is crucial to informing efforts that aim to increase children’s physical activity, yet little is understood about their perceptions of specific barriers and enablers to promoting children’s physical activity and reducing screen time. The present study sought to explore these perceptions. Methods Semi-structured focus groups and individual interviews were conducted with grandparents who reported providing care to a grandchild aged 3 to 14 years. A total of 20 grandparents were sampled (mean age = 67.8 years). Data were subjected to reflexive thematic analysis. Results Key reported barriers to physical activity included (i) the effort (physical and logistical) and financial cost associated with organizing physical activities, (ii) grandparents’ age and mobility issues (e.g., due to injury or illness), (iii) caring for children of different ages (e.g., older children having different physical activity interests than younger children), and (iv) a local environment that is not conducive to physical activity (e.g., lack of appropriate facilities). Barriers to reducing screen time included (i) parents sending children to care with electronic devices and (ii) children’s fear of missing out on social connection that occurs electronically. Strategies and enablers of physical activity included (i) integrating activity into caregiving routines (e.g., walking the dog), (ii) involving grandchildren in decision making (e.g., asking them in which physical activities they wish to engage), (iii) encouraging grandchildren to engage in activity with other children, and (iv) creating a physical and social environment that supports activity (e.g., owning play equipment). A common strategy for reducing screen time was the creation of a home environment that is not conducive to this activity (e.g., removing electronic devices from view). Conclusions Findings suggest that grandparents may benefit from resources that assist them to identify activities that are inexpensive and require minimal effort to organize. Activities that account for grandparents’ age and health status, as well as any environmental barriers, are likely to be well-received

Process optimisation of PA11 in fiber-laser powder-bed fusion through loading of an optical absorber

Industrial laser processing is rapidly shifting towards fiber lasers with wavelengths between 780nm and 2200nm. This can be largely contributed to the excellent beam properties and, ease of operation. However, for Additive Manufacturing of polymers, CO2 lasers at wavelengths of 10,6µm are pre- dominantly used. CO2 lasers provide unmatched energy absorption by the C-H bonds of Polyamide (PA). To remedy this, the current study investigates using a high-power fiber laser (1080nm) for consolidating PA11 mixed with a black optical absorber. Several compositions are produced by mixing commercially available white and black powder. Aiming at finding the optimum optical absorber loading and the corresponding process parameters, allowing the highest possible compo- nent fidelity, while achieving the lightest hue of grey possible to allow for later colouring. The experiment is conducted on an in-house developed Open Architecture Laser Powder-Bed Fusion system. The parts are examined through, surface roughness, and mechanical characterisation.Mechanical Engineerin

Longitudinal associations between biomarkers of inflammation and changes in depressive symptoms in patients with type 1 and type 2 diabetes

Background: Depressive disorders represent a frequent comorbidity of type 1 diabetes (T1D) and type 2 diabetes (T2D). Subclinical inflammation increases the risk of depressive symptoms in the general population, but the relationship appears complex and bidirectional, and longitudinal data from patients with diabetes are lacking. Therefore, this study aimed to analyse associations between changes in depressive symptoms and changes in biomarkers of inflammation in patients with T1D and T2D and to investigate the hypothesis that higher baseline levels of biomarkers of inflammation are related to a less pronounced reduction of depressive symptoms over time. Methods: Depressive symptoms and systemic levels of six biomarkers of inflammation were assessed in 168 individuals with T1D and 103 individuals with T2D who participated in baseline and 1-year follow-up examinations. Data were obtained from two matching randomised controlled trials addressing diabetes distress and depressive symptoms. Longitudinal associations between biomarkers and depressive symptoms were estimated using linear regression models adjusting for multiple confounders. Results:In patients with T2D, reductions in depressive symptoms were associated with reductions in high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-18 and IL-1 receptor antagonist (IL-1RA) (P ≤ 0.016), whereas no associations were seen for IL-6, CCL2 and adiponectin. Higher CCL2 levels at baseline were associated with lower subsequent reduction in depressive symptoms (P = 0.018). Neither baseline levels nor changes in biomarkers in subclinical inflammation were associated with changes in depressive symptoms in patients with T1D. Conclusions: Reductions of depressive symptoms were longitudinally associated with reductions in biomarkers of inflammation in patients with T2D. Higher baseline CCL2 levels were related with lower reduction of depressive symptoms in this group. No such associations were observed in patients with T1D, suggesting that risk factors and pathomechanisms linking inflammation and depression may differ between diabetes types