The future of aircraft lies in highly intelligent vehicles which are able to adapt themselves to different missions and take-off and land anywhere. Tailsitters, aircraft capable of controlled transitions between horizontal flight (like a fixed-wing aircraft) and vertical flight (like a rotary-wing aircraft), are one such form of vehicle. The focus of this research stems from a collaboration between the Surrey Space Centre and QinetiQ involving a new class of VTOL tailsitter - the QinetiQ Eye-On™ UAV - which offers uniqueness from all other known tailsitters in its use of twin helicopter rotors, elevons and a rudderless flying-wing design. A core objective of this research is to develop a control and navigation architecture capa.ble of handling the transitional flight regime in tailsitters and to understand the mechanism by which a transition can be controlled. Very little past research has addressed either of these in detail, often including only cursory modelling and simulation, no regard to how transitions can be 'shaped', and with no consideration of optimisation of transitions or whether their control laws are even robust. Another shortcoming of past literature is the minimal amount of experimental work undertaken which mostly uses only generic, simple single-propeller aircraft and does not consider transitional flight. Furthermore, examination of real-world applications where a tailsitter can be used has also been barely considered in literature. The limitations are addressed in three research divisions: I, II, III. {I} Development of a novel six degree of freedom (6-DOF) non-linear model with custom-designed numerical fluid dynamics, has allowed. high-fidelity simulation of all flight regimes to be performed. The developed control and navigation architecture is the first all-encompassing control architecture for the class of twin rotor tailsitters; it uses rudimentary low-level controllers and is capable of performing three different transitions: vertical to horizontal (V to H) , H to V (altitude elevation) and H to V (altitude invariant). The last of these is a ground-breaking discovery; transitions from H to V can be performed with virtually no increase in altitude. One improvement from past literature is that transitioning is undertaken in a closed-loop manner by commanding the vehicle to follow velocity and pitch setpoints. A carefully selected set of parameters has been devised to allow transitions to be shaped by transition time period, flight speed, sample size and smoothness of the control setpoint command. For the first time optimisation is applied to obtain ideal parameters for the transitions and robustness simulations stochastically consider environmental disturbances and variation of vehicle mass. [II] A comprehensive experimental framework has been developed tha.t uses various advanced testbed configurations to validate the control architecture, requiring the fusion of both aeroplane and helicopter technologies. Initially, an indoor motion capture testbed uses a series of precursory vehicles (including both quadrotor and Chinook) to pioneer taiisitter technology. A thrust testbed was also developed to explore thrust curve relationships and obtain optimal thrust zones for differing flight regimes. The outdoor testbed required the development of a complete self-contained autopilot system, including telemetry and ground station, which was tested in a progressive fl ight campaign spanning four flight locations across the UK. The experimentation forms the first demonstration of &-DOF untethered flight for the class of twin rotor tailsitters in VTOL, manual transitional and semi-autonomous transitiona.l modes. [III] In terms of systems analysis, two distinct civil and military scenarios are evaluated: linear asset monitoring, and perch and stare (which includes an innovative miniaturisation analysis) . The first thorough and realistic consideration is also given to the use of a reusable tailsitter v.'ith a docking station for staged exploration in extra-terrestrial environments. Industrially, the research programme extensively develops the technology necessary for autonomous flight of the UAV and extends from Technology Readiness Level (TRL) 2 to 6. Academically, significant contributions have been made to the field including: tailsitter modelling, transitioning methodology, control architecture, optimisation, testbed design, flight experimentation, systems design.

no / Since the development of the first cytotoxic agents, synthetic organic chemistry has advanced enormously. The synthetic and medicinal chemists of today are at the centre of drug development and are involved in most, if not all, processes of drug discovery. Recent decreases in government funding and reformed educational policies could, however, seriously impact on drug discovery initiatives worldwide. Not only could these changes result in fewer scientific breakthroughs, but they could also negatively affect the training of our next generation of medicinal chemists.

Textbook accounts of vertebrate embryonic development have been based largely upon experiments on amphibian embryos, which have shown that the tissues of the trunk and tail are organised from distinct precursors that existed during gastrulation. In the mouse and chick, however, retrospective clonal analyses and transplantation experiments have demonstrated that the amniote body instead arises progressively from a population of axial precursors that are common to both the neural and mesodermal tissues of the trunk and tail. For this reason, they are known as neuro-mesodermal progenitors (NMps). Detailed studies of NMps have been precluded by their lack of a unique gene expression profile and the technical difficulties associated with isolating them from the embryo. Mouse embryonic stem cells (ESCs) provide the possibility of instead deriving them in vitro. ESCs have been used to model developmental processes, partly through large cellular aggregates known as embryoid bodies. These structures do not, however, resemble the axial organisation of the embryo and they develop in a disordered manner. This thesis presents a novel culture system of small, three-dimensional aggregates of ESCs (gastruloids) that can recreate the events of early post-implantation development, including axial elongation. Gastruloids are the first ESC-based model for axial elongation morphogenesis; this body of work characterises their development and identifies a candidate population of NMps within their elongating tissues. Additionally, this work establishes a xenotransplantation assay for testing the functional properties of in vitro-derived NMp populations in the chicken embryo and applies it to NMps from gastruloid cultures. The results of this assay show that gastruloids are a credible source of NMps in vitro and therefore offer a new experimental means to interrogate their properties. The use of gastruloids to recreate embryonic development has implications for basic research as a synthetic system and for the therapeutic derivation of other embryonic progenitors through bioengineering.