• Canada
• UK Research and Innovation close
• UKRI|EPSRC close
• 2007 close
• 2011 close

Aerosols are important in a wide range of scientific disciplines, from the delivery of drugs to the lungs, to their impact on the earth's climate and their role in climate change, through to their application in the delivery of fuels for combustion, and their processing in plasmas to prepare functionalised materials. Defined as a dispersion of solid or liquid particles within the gas phase, aerosol properties are governed by the chemical composition and size of the individual particles. It is also widely recognised that the chemical composition of the surface of a particle can play a critical role in governing the properties of the aerosol. This is primarily because aerosols can present a large surface area to the surrounding gas phase. Any chemistry that occurs must be mediated through transfer of molecules from the gas phase into the bulk of the particle across the surface. The chemical make-up of the surface can significantly influence this transfer. Further, it is recognised that particles are generally not uniform in composition throughout their volume. For example, a single particle may consist of organic and water phases that are not mixed, but are phase separated. This can have a profound influence on the properties of a particle when compared with the properties expected for a particle characterised by uniform mixing.In this research we will investigate the relationship between the chemical, physical and optical properties of aerosol particles and their chemical composition and uniformity in composition. We will develop new techniques to examine the internal structure within a single particle, to explore how different chemicals mix or separate in a single particle, and to investigate the ease with which molecules are taken up at the surface of the particle. In addition, we will develop a new instrument to measure how efficiently a particle absorbs light. In the atmosphere, aerosol particles can scatter sunlight back into space, counteracting the heat trapping properties of the greenhouse gases. However, some pollutant particles, such as black carbon produced in combustion, strongly absorb sunlight enhancing the warming of the atmosphere. The impact of aerosols remains poorly quantified and new techniques are required to study their light absorption properties.The novel experiments described above are based around two new powerful techniques. Using a tightly focussed laser beam, we can hold onto a single particle indefinitely. Known as optical tweezers, this approach has been widely used for holding particles in liquids. However, we have shown that the same approach can be used to hold onto aerosol particles. Further, light can become trapped in spherical aerosol droplets in much the same way as light undergoes total internal reflection in the formation of a rainbow. The light can travel a distance of metres around the edge of the droplet before escaping. By measuring the wavelength of the light, we can determine how far the light must travel to make one complete circuit of the droplet circumference. Not only can this provide a very accurate way of determining the size of the droplet, but it can enable us to make sensitive measurements of the composition of the droplet near the droplet surface. It is anticipated that the development and application of these new techniques will yield important new information on the properties of aerosols and their behaviour in many of the complex scientific problems highlighted above.

Since the development of the first Kerr-lens mode-locked lasers in 1990, practical femtosecond lasers in a wide variety of configurations have delivered handsomely to a significant number of major scientific developments. It has to be recognised that the application space remains limited by the cost, complexity, skilled-user requirements and restricted flexibility of the current generation of ultrafast lasers. In this proposed joint project we seek to lead the way in the development of a new generation of ultrafast lasers. By adopting a modular approach for laser design we are aiming to demonstrate a platform from which lasers can be designed to address a wide range of user-specific requirements. By taking this approach, lasers for use in communications, for example, will have the necessary high repetition rates and low peak powers whereas for biophotonics high peak powers will be delivered to take full advantage of exploitable optical nonlinearities. We plan to work with vibronic crystals in both bulk and waveguide geometries and semiconductor quantum dot structures as the primary gain media. Although vibronic crystals have been deployed widely in ultrashort-pulse lasers the flexibility offered by conventional laser designs is very limited. To remedy this situation we intend to revolutionise cavity design to enable electrical control of the laser output parameters. For example, we wish to provide a means to users to change from an unmodelocked status to a femtosecond-pulse regime on demand. Also, by exploiting waveguiding in vibronic crystals we are confident that we can introduce a new generation of highly compact lasers that will combine many of the advantages of a semiconductor laser with the most attractive features of crystal based devices. In some preliminary work in the Ultrafast Photonics Collaboration we have shown the potential of semiconductor quantum dot structures as broadband gain media that can support the amplification and generation of femtosecond optical pulses. We now seek to build on those promising results and move towards truly flexible ultrafast lasers that will be amenable to external electronic control of the gain and loss components. Progress is expected to lead to a new generation of lasers that can give applications compatibility that far exceeds available traditional laser system designs. Within this strategy we plan to employ hybrid approaches where the benefits of semiconductor lasers will be combined with the energy storage capabilities of crystals to deliver compact and rugged sources having pulse characteristics that cover a range of durations, energies and profiles.A major part of this project effort will be devoted to the development of control functionality in ultrafast lasers. The intention is to use direct electrical control of intracavity components to deliver designer options for pulse shaping, modulated data streams, wavelength tuning and tailored dispersion. To ensure that this research is applicable we will evaluate the laser developments in the context of a set of identified demonstrators. These implementations will be used to show how design flexibility can deliver optimised lasers for biological, medical, communications and related applications.We have put together a research team having complementary of expertise and established track records of international excellence in photonics. This project as a whole will be managed from St Andrews University but all three research groups will undertake interactive research on all aspects of the laser development. We are confident that the work of this team will represent cutting-edge fundamental and translational research and it should represent a world leading strength for the UK in the development of new ultrafast lasers.

In this project we propose to investigate techniques that will allow an additional human sense, haptic touch (or reflected force), to be sent over the Internet. Today's telecommunications and computer networks have been designed to carry information that pertains to only two human senses: the auditory sense (for example sound and speech), and the visual sense (for example video, graphic, and text etc). The Internet is now being reengineered so that it can provide different levels of service for different types of traffic, e.g. to support the transport of voice over its IP protocol (VOIP). This has lead to the design of network architectures that can support different Quality of Service (QoS) levels. It is clear that introducing into networks the ability to carry information relating to other senses will open up an enormous potential for both new and dramatically improved applications. The ability to embed touch or force into applications and then distribute them across the Internet will have significant implications in areas such as collaborative design, immersive reality and teleconferencing, distance learning and training, virtual reality showrooms and museums. It is now also recognised that the introduction of a haptic component to interactive games has increased users' quality of experience, and this has in turn increased the market demand for these types of applications. It is also clear that the network service (i.e. QoS) needed to support other senses such as touch (haptics) will be significantly different from that which currently exists.Almost all haptic applications are designed whereby the haptic device is connected to a single stand-alone system, or where dedicated connections are used to provide remote interaction. Architecting the Internet to provide an acceptable service for distributed haptic applications therefore represents a significant challenge that this research aims to address. A related challenge is to design architectures that can scale to support the QoS required for the interaction of multiple haptic devices (or users).Recent research has shown that each type of network impairment affects the sense of force feedback in a particular way. Network delay can make the user feel a virtual object before it is visually in contact, or to move into solid objects. Delay also desynchronizes the different copies of the virtual environment. Jitter makes the user feel that the object's mass is variable. Packet loss can reduce the amount the force felt by the user. The effect of these impairments is to introduce unwanted artefacts into the virtual environment. However they also effect the interaction with the physical world and a more serious consequence is to cause damage to the haptic device, and in some situations may also cause physical damage to the end user. To date, the network has not been seriously considered in the design of haptic compensation algorithms. However the introduction of graded QoS architectures (e.g. Diffserv) into the next generation Internet now offers the capability to bound effects such as packet delay jitter and loss. These guarantees can be used to offer specific levels of tolerance (spatial and haptic) to different applications. Therefore a major contribution of the research will be to develop compensation techniques that consider the current level of service that the network can offer and map these against different types of haptic applications.A series of trials investigating the performance of the derived architectures and compensation algorithms will be conducted with the collaborators who represent key constituents in this technology area: BT (network operator, UK), LABEIN (haptic applications, Spain), HandshakeVR (haptics software, Canada), and Immersion (haptic device manufacturer, California). The results will provide valuable knowledge to the designers of future devices, DHVEs and to the designers of the networks that have to support them.

Software systems are rarely written from scratch: they evolve over long periods of time. When a change is made, this often affects many different locations in a system, and it is hard to make a change consistently. For that reason, automated tools to help the process of software change are desirable. Refactoring refers to the process of restructuring an existing piece of software, often prior to introducing new functionality, or to take advantage of a new technology. Refactoring must preserve the behaviour of existing code;,and tools that help in refactoring both assist in the restructuring process and in checking that the behaviour has not changed. Unfortunately today's refactoring tools are very hard to construct, they are still quite limited in functionality, and they often contain bugs.This project aims to construct a framework for better refactoring tools. In particular, the work is driven by refactorings for a new set of language features, called `aspect-oriented programming' that have recently been added to Java.Our framework will be based on developments in three separate areas of computer science:* `strategies' to control the process of rewriting program code, from the `term rewriting' community* `reference attribute grammars' to specify the conditions that guarantee behaviour is preserved, from the `compilers' community* `incremental evaluation' of declarative rules, from the `functional and logic programming' communityThe quality of our framework will be assessed by coding selected case studies using alternative methods. In particular, we shall implement several refactorings directly in Eclipse, the leading development environment for writing aspect-oriented programs in industry.