The ability to control the evolution of a reaction is a long-standing goal of chemistry. One approach is to use the electric field provided by a laser pulse as the guide. Recent work has focused on shaping and timing the pulse so that the field interacts with the molecules in a particular way to influence the energy flow through the molecule and thus eventually the course of a reaction. The optimal pulse shape is achieved by using a feedback loop , focusing on a signal related to the desired outcome and allowing a computer algorithm to change the pulse shape during repeated cycles of the experiment until the signal is maximised. This optimal control scheme has proved to be able to control a wide range of chemical systems, but the complicated pulse shapes provide little insight into the procedure, and the experiments have a black box nature. A different, very appealing, approach to control through a laser field is to use the field to change the shape of the potential energy surface over which the reaction proceeds. This can be acheived using a strong pulse which induces Stark shifting of the surface. By careful timing of a pulse of the appropriate strength, it has been shown that it is possible to control the products from IBr dissociation by effectively changing the barrier height to the different possible channels.The project aims to investigate theoretically this potentially general approach to laser control. The results should start to build up a picture of how the complicated potential energy surfaces of small molecules are altered by interaction with the field. This will help in the development of experiments and in our understanding of how molecules behave in a light field.
The aerospace industry is striving to design lighter structures to give higher payloads, lower carbon emissions, and improved fuel efficiency. In order to do this, materials must be used as efficiently as possible, and so it is essential that their behaviour under load is fully understood. Traditional engineering design uses laboratory data to determine the dimensions of structural elements. In many cases these data are from simplified testing of cracked samples and can be very conservative. This can lead to over-engineered components which weigh more than the optimum design.The work proposes to develop experimental techniques capable of generating data that can be used to model actual, lightweight, safety-critical components. Examples of such components are wing skin panels, which, with their array of stiffeners and holes, present a complex loading problem, where any cracks are subjected to loads in several directions thereby altering their direction of growth.Two experimental techniques will be studied: Thermoelastic Stress Analysis (TSA) and Digital Image Correlation (DIC). In TSA, temperature changes experienced by a structure under cyclic loading are measured. These changes in temperature are caused by the applied loads and their magnitude is proportional to the sum of the principal stresses on the surface of the structure. DIC, on the other hand, uses a high resolution digital camera to track surface features in three dimensions. The images are analysed to determine the relative displacements due to loading. Both these techniques can be used to determine the mechanisms of crack propagation through a metallic or composite structure loaded simultaneously in more than one direction.It is proposed to spend three months in North America using the TSA and DIC methodologies to investigate crack tip stress fields under biaxial loads in both metallic and composite materials. This work will be used to improve understanding of the relationship between different load magnitudes, loading modes, and plastic crack tip behaviour. Another key output will be the establishment of future collaborative research projects. The majority of the trip will be spent at the Composite Vehicle Research Centre (CVRC) at Michigan State University, USA. An invitation has also been received to visit the Structures and Materials Performance Laboratory at the Institute for Aerospace Research (IAR) in Ottawa, Canada. The CVRC has established a comprehensive array of laboratory facilities for testing materials and components, with a suite of state-of-the-art optical experimental mechanics equipment. The IAR is part of the National Research Council Canada, the Canadian government's organisation for research and development and has extensive research facilities in experimental mechanics, including interests in DIC and TSA, with applications in a range of aerospace structures. Both these world-leading research institutions offer the potential to develop first class research partnerships in key cross-functional, and industrially relevant disciplines.
The vision for this research is to develop a novel toolset for flight simulation fidelity enhancement. This represents a step-change in simulator qualification, is well-timed making a significant contribution to the UoL initiated NATO STO AVT-296-RTG activity and will have an immediate impact through engagement with Industry partners. High fidelity modelling and simulation are prerequisites for ensuring confidence in decision making during aircraft design and development, including performance and handling qualities estimation, control law development, aircraft dynamic loads analysis, and the creation of a realistic piloted simulation environment. The ability to evaluate/optimise concepts with high confidence and stimulate realistic pilot behaviour are the kernels of quality flight simulation, in which pilots can train to operate aircraft proficiently and safely and industry can design with lower risk. Regulatory standards such as CS-FSTD(H) and FAA AC120-63 describe the certification criteria and procedures for rotorcraft flight training simulators. These documents detail the component fidelity required to achieve "fitness for purpose", with criteria based on "tolerances", defined as acceptable differences between simulation and flight, typically +/- 10% for the flight model. However, these have not been updated for several decades, while on the military side, the related practices in NATO nations are not harmonised and have often been developed for specific applications. Methods to update the models for improved fidelity are mostly ad-hoc and, without a strong scientific foundation, are often not physics-based. This research will provide a framework for such harmonisation removing the barriers to adopting physics-based flight modelling and will create new, more informed, standards. In this research two aspects of fidelity will be tackled, predictive fidelity (the metrics and tolerances in the standards) and perceptual fidelity (pilot opinion). The predictive fidelity aspect of the research will use System Identification techniques to provide a systematic framework for 'enhancing' a physics-based simulation model. The perceptual fidelity research will develop a rational, novel process for task-specific motion tuning together with a robust methodology for capturing pilots' subjective assessment of the overall fidelity of a simulator. Extensive use will be made of flight simulation and real-world flight tests throughout this project in both the predictive and perceptual fidelity research.
Ultra-short and ultra-intense laser pulses provide an impressive camera into the world of electron motion. Attoseconds and sub-femtoseconds are the natural time scale of multi-electron dynamics during the ionization and break-up of atoms and molecules. The overall aim of the proposed work is to investigate attosecond phenomena, pathways of correlated electron dynamics and effects due to the magnetic field of light in three and four-electron ionization in atoms and molecules triggered by intense near-infrared and mid-infrared laser pulses. Correlated electron dynamics is of fundamental interest to attosecond technology. For instance, an electron extracted from an atom or molecule carries information for probing the spatio-temporal properties of an ionic system with angstrom resolution and attosecond precision paving the way for holography with photoelectrons. Moreover, studies of effects due to the magnetic field of light in correlated multi-electron processes are crucial for understanding a variety of chemical and biological processes, such as the response of driven chiral molecules. Chiral molecules are not superimposable to their mirror image and are of particular interest, since they are abundant in nature. The proposed research will explore highly challenging ultra-fast phenomena involving three and four-electron dynamics and effects due to the magnetic field of light in driven atoms and during the break-up of driven two and three-center molecules. We will investigate the physical mechanisms that underly these phenomena and devise schemes to probe and control them. Exploring these ultra-fast phenomena constitutes a scientific frontier due to the fast advances in attosecond technology. These fundamental processes are largely unexplored since most theoretical studies are developed in a framework that does not account for the magnetic field of light. Moreover, correlated three and four-electron escape is currently beyond the reach of quantum mechanical techniques. Hence, new theoretical tools are urgently needed to address the challenges facing attoscience. In response to this quest, we will develop novel, efficient and cutting-edge semi-classical methods that are much faster than quantum-mechanical ones, allow for significant insights into the physical mechanisms, compliment experimental results and predict novel ultra-fast phenomena. These semi-classical techniques are appropriate for ionization processes through long-range Coulomb forces. Using these techniques, we will address some of the most fundamental problems facing attoscience. Our objectives are: 1) Identify and time-resolve novel pathways of correlated three-electron dynamics in atoms driven by near-infrared and mid-infrared laser pulses. 2) Explore effects due to the magnetic field of light in correlated two and three-electron escape during ionization in atoms as well as in two and three-center molecules driven by near-infrared and mid-infrared laser pulses that are either linearly or elliptically polarized or by vector beams, i.e. "twisted" laser fields, an intriguing form of light that twists like a helical corkscrew. 3) Control correlated multi-electron ionization and the formation of highly exited Rydberg states in four-active-electron three-center molecules by employing two-color laser fields or vector beams.
Oil crops are one of the most important agricultural commodities. In the U.K. (and Northern Europe and Canada) oilseed rape is the dominant oil crop and worldwide it accounts for about 12% of the total oil and fat production. There is an increasing demand for plant oils not only for human food and animal feed but also as renewable sources of chemicals and biofuels. This increased demand has shown a doubling every 8 years over the last four decades and is likely to continue at, at least, this rate in the future. With a limitation on agricultural land, the main way to increase production is to increase yields. This can be achieved by conventional breeding but, in the future, significant enhancements will need genetic manipulation. The latter technique will also allow specific modification of the oil product to be achieved. In order for informed genetic manipulation to take place, a thorough knowledge of the biosynthesis of plant oils is needed. Crucially, this would include how regulation of oil quality and quantity is controlled. The synthesis of storage oil in plant seeds is analogous to a factory production line, where the supply of raw materials, manufacture of components and final assembly can all potentially limit the rate of production. Recently, we made a first experimental study of overall regulation of storage oil accumulation in oilseed rape, which we analysed by a mathematical method called flux control analysis. This showed that it is the final assembly that is the most important limitation on the biosynthetic process. The assembly process requires several enzyme steps and we have already highlighted one of these, diacylglycerol acyltransferase (DGAT), as being a significant controlling factor. We now wish to examine enzymes, other than DGAT, involved in storage lipid assembly and in supply of component parts. This will enable us to quantify the limitations imposed by different enzymes of the pathway and, furthermore, will provide information to underpin logical steps in genetic manipulation leading to plants with increased oil synthesis and storage capabilities. We will use rape plants where the activity of individual enzymes in the biosynthetic pathway have been changed and quantify the effects on overall oil accumulation. To begin with we will use existing transgenic oilseed rape, with increased enzyme levels, where increases in oil yields have been noted; these are available from our collaborators (Canada, Germany). For enzymes where there are no current transgenic plants available, we will make these and carry out similar analyses. Although our primary focus is on enzymes that increase oil yields, we will also examine the contribution the enzyme phospholipid: diacylglycerol acyltransferase (PDAT) makes to lipid production because this enzyme controls the accumulation of unsaturated oil, which has important dietary implications. In the analogous model plant Arabidopsis, PDAT and DGAT are both important during oil production. Once we have assembled data from these transgenic plants we will have a much better idea of the control of lipid production in oilseed rape. Our quantitative measurements will provide specific targets for future crop improvements. In addition, because we will be monitoring oil yields as well as flux control we will be able to correlate these two measures. Moreover, plants manipulated with multiple genes (gene stacking) will reveal if there are synergistic effects of such strategies. Because no one has yet defined quantitatively the oil synthesis pathway in crops, data produced in the project will have a fundamental impact in basic science. By combining the expertise of three important U.K. labs. with our world-leading international collaborators, this cross-disciplinary project will ensure a significant advance in knowledge of direct application to agriculture.