High Speed Visible Light Communication Using Blue GaN Laser Diodes

GaN-based laser diodes have been developed over the last 20 years making them desirable for many security and defence applications, in particular, free space laser communications. Unlike their LED counterparts, laser diodes are not limited by their carrier lifetime which makes them attractive for high speed communication, whether in free space, through fiber or underwater. Gigabit data transmission can be achieved in free space by modulating the visible light from the laser with a pseudo-random bit sequence (PRBS), with recent results approaching 5 Gbit/s error free data transmission. By exploiting the low-loss in the blue part of the spectrum through water, data transmission experiments have also been conducted to show rates of 2.5 Gbit/s underwater. Different water types have been tested to monitor the effect of scattering and to see how this affects the overall transmission rate and distance. This is of great interest for communication with unmanned underwater vehicles (UUV) as the current method using acoustics is much slower and vulnerable to interception. These types of laser diodes can typically reach 50-100 mW of power which increases the length at which the data can be transmitted. This distance could be further improved by making use of high power laser arrays. Highly uniform GaN substrates with low defectivity allow individually addressable laser bars to be fabricated. This could ultimately increase optical power levels to 4 W for a 20-emitter array. Overall, the development of GaN laser diodes will play an important part in free space optical communications and will be vital in the advancement of security and defence applications

Impact of Legislated and Best Available Emission Control Measures on UK Particulate Matter Pollution, Premature Mortality, and Nitrogen-Sensitive Habitats

Past emission controls in the UK have substantially reduced precursor emissions of health-hazardous fine particles (PM2.5) and nitrogen pollution detrimental to ecosystems. Still, 79% of the UK exceeds the World Health Organization (WHO) guideline for annual mean PM2.5 of 5 μg m-3 and there is no enforcement of controls on agricultural sources of ammonia (NH3). NH3 is a phytotoxin and an increasingly large contributor to PM2.5 and nitrogen deposited to sensitive habitats. Here we use emissions projections, the GEOS-Chem model, high-resolution data sets, and contemporary exposure-risk relationships to assess potential human and ecosystem health co-benefits in 2030 relative to the present day of adopting legislated or best available emission control measures. We estimate that present-day annual adult premature mortality attributable to exposure to PM2.5 is 48,625 (95% confidence interval: 45,188-52,595), that harmful amounts of reactive nitrogen deposit to almost all (95%) sensitive habitat areas, and that 75% of ambient NH3 exceeds levels safe for bryophytes and lichens. Legal measures decrease the extent of the UK above the WHO guideline to 58% and avoid 6,800 premature deaths by 2030. This improves with best available measures to 36% of the UK and 13,300 avoided deaths. Both legal and best available measures are insufficient at reducing the extent of damage of nitrogen pollution to sensitive habitats. Far more ambitious reductions in nitrogen emissions (>80%) than is achievable with best available measures (34%) are required to halve the amount of excess nitrogen deposited to sensitive habitats

The Promise and Realities of the Use of Cyber Technologies for Promoting Research in Public STEM Museum Experiences

Cyberlab at OSU Final Report.A seven-year effort funded by the United States’ National Science Foundation and the Oregon Sea Grant College Program sought to identify and deploy in a public STEM museum setting a suite of digital tools for collecting and supporting analysis of data on the use of the setting in near real time and as evidence for in situ learning. In addition to full-museum camera coverage and data collection, five exhibit-based research platforms were developed to allow for collection of linked video, audio, and digital input (keystroke, touch screen manipulation) data at particular locations in the museum. A further effort explored the use of social media data mining tools as well as apps for research on how learners create continuity across STEM learning experiences distributed temporally and geographically. Returns on investment for research on informal learning were proven to be high with signifiant gains for researchers working with the museum and for building research partnerships with other museums and informal STEM learning environments (e.g., Maker Faires, public exhibits, tourism in marine environments), but return on investment for museum operations and programmatic advancement were relatively minor. While the project proved that a public museum can successfully employ current video-based, cyber-linked technologies to document and study learning outside of a laboratory setting, it also demonstrated that such activity is most likely beyond the budgetary and information technology capacity of most public institutions. However, the project also piloted and provided proof of concept for smaller, mobile efforts using many of the same technologies and tools in scaled-down but efficient research and evaluation efforts.Keywords: Cyberlearning; Informal Learning Environments; STEM; Video-based Researc