• Canada
• 2018-2022close
• 2018 close

Many applications of THz radiation require sources that are compact, low-cost, and operate at room temperature. In this project, a low-noise optically-controlled THz array antenna system will be developed, addressing a significant barrier in the adoption of THz technology. We will demonstrate a novel 'system on a chip', integrating a thin film antenna array, photodiode array, semiconductor optical amplifier (SOA) array and optical beam forming network. The SOA array enhances the pump power and ensures all array elements are evenly pumped. The beam former is used to control the phase difference between the THz radiation from different THz antennas, and thus scanning of THz beam can be realized. A THz repetition frequency mode-locked laser will be used as the light source to lock the phase of optical signals in the chip, greatly reducing the linewidth of the THz emission. The advantages of this THz emitter system include a high peak intensity due to radiation from the antennas combining coherently, room temperature operation, continuous-wave operation, compact form factor, and a narrow steerable beam. The sources will be assessed for use in systems for high-bandwidth wireless communications and for medical imaging.

Sea ice extent in the Arctic Ocean has seen a steady decline since satellite-borne measurements began in the late 1970s. Sea ice supports the growth of ice algae, a fundamental component of the Arctic carbon cycle, providing food to Arctic animals. When sea ice melts every spring, ice algae are released to the water where they are either consumed by pelagic animals, or sink to the seafloor. Gaining an accurate understanding of these pathways for this important energy rich carbon resource represents a major scientific challenge that holds the key to understanding the future of Arctic ecosystems. However, until recently, this has not been possible because of the challenges associated with distinguishing sea ice carbon from other similar sources of carbon, such as phytoplankton. Having recently overcome these challenges in the last 3 years, it is now possible to unambiguously trace the pathway of sea ice-derived carbon. Recent findings have therefore shown that sea ice-derived carbon can be found in Arctic animals year-round. This is believed to be because excess (not consumed during sinking) sea ice-derived carbon that sinks can also become 'stored' within sediments where it can remain available as a food source to animals year-round. Consequently, if this idea is correct, our present assumption of the role sea ice carbon plays in the ecosystem is severely underestimating its importance. This project will bring together the expertise of British, Canadian and American scientists in a new collaborative partnership to assess whether the seafloor (e.g. rock, sand, mud, silt) acts as a 'store' of Arctic sea ice-derived primary production that can be considered available for marine animals to consume. Completion of the project aims relies upon collaboration between Brown's established (Mundy) and new (Iken) links within the assembled team. We will carry out studies on the marine region around Southampton Island, northwest Hudson Bay (Nunavut) which encompasses one of Canada's largest summer and winter aggregations of Arctic marine mammals. By sharing resources with a funded Canadian research project we will access a unique field site to collect primary preliminary data to improve understanding of ecosystem structure and function. Our findings will be relevant to the whole Arctic region and so will stimulate new research interests on an international scale.

Accounting for high genetic diversity in ecologically-important traits is a fundamental problem in evolutionary biology. Individuals vary enormously at the genetic level, even within local populations, and we do not understand why. Recent work implicates an advantage to rare types as a critical factor maintaining genetic variation in many species, but we have little understanding of how this process actually unfolds in the wild. To address this gap, we need to (1) understand how ecological and social interactions promote or erode genetic diversity, and (2) link these interactions among organisms directly to the genes underlying the traits that mediate these interactions. This project will link a genetically diverse trait in the Trinidad guppy (Poecilia reticulata) to the ecological and social interactions that shape its evolution, and to the underlying genes that shape this diversity. Our previous work indicates that interactions with predators and with potential mates both favour rare colour patterns in this species. To determine which of the processes is most responsible for promoting diversity, we will collect data on predation risk and mating behaviour in multiple natural populations and relate these data to the degree of genetically-based diversity in colour patterns. Then, using populations and closely related species that vary in their genetic diversity, we will use whole-genome DNA sequencing to identify genes that control this highly variable trait. This will allow us to determine how ecological and molecular processes interact to promote or constrain evolution under balancing selection. Finally, we will directly test the idea that interactions between potential mates can maintain diversity in this species by observing evolution in real time in experimental populations with different opportunities for mate choice.