Mesopore immobilised bis(oxazoline) catalysts for enantioselective catalysis

Mesoporous silica materials have the potential to replace many conventional silicas for uses such as supports for heterogeneous catalysis and absorbents. The large pore size and high surface area make them ideal for supporting bulky organometallic catalysts for enantioselective reactions. We have immobilised chiral bis(oxazoline) metal complexes onto the surfaces of some of these versatile supports (MCM-41 and MCM-48) via different tethering strategies. The resulting heterogeneous catalysts were shown to be highly active in the enantioselective cyclopropanation of styrene with ethyl diazoacetate

Hydrodynamics of the atomic force microscope

With a proven ability to uncover fundamental biological processes, the atomic force microscope (AFM) represents one of the most valuable and versatile tools available to the biophysical sciences. We study the unsteady small-scale flows generated within the AFM by its sensing probe (a long thin cantilever), which have received relatively little attention to date, yet which are increasingly relevant in an age of microdevices. The early parts of this thesis investigate some canonical two-dimensional flows driven by oscillations of an infinite-length rigid cantilever. These prove amenable to analysis and enable us to investigate many of the important physical phenomena and compile a comprehensive collection of asymptotic expressions for the drag. The corresponding results lay out the influence of a nearby wall, geometry and oscillation frequency. The limitations of a two-dimensional approach are then explored through the development of a novel unsteady slender-body theory (USBT) for finite-length cylinders, an asymptotic treatment of which offers corrections to traditional resistive-force-theory (RFT) methods by accounting for geometric factors and flow inertia. These ideas are then extended to the study of thin rectangular plates. Two key parameters are identified which promote two-dimensionality in the flow, namely the frequency of oscillation and the proximity of a nearby boundary. We then examine flexible cylinders and plates by coupling the hydrodynamics to linearized elastic beam and plate equations, which simulate the hydrodynamically-damped high-speed deformable motion of the AFM's cantilever, when driven either externally or by Brownian motion. In the latter case, we adopt an approach which offers notable improvements over the most advanced method currently available to the AFM community

Hydrodynamics of the atomic force microscope

With a proven ability to uncover fundamental biological processes, the atomic force microscope (AFM) represents one of the most valuable and versatile tools available to the biophysical sciences. We study the unsteady small-scale flows generated within the AFM by its sensing probe (a long thin cantilever), which have received relatively little attention to date, yet which are increasingly relevant in an age of microdevices. The early parts of this thesis investigate some canonical two-dimensional flows driven by oscillations of an infinite-length rigid cantilever. These prove amenable to analysis and enable us to investigate many of the important physical phenomena and compile a comprehensive collection of asymptotic expressions for the drag. The corresponding results lay out the influence of a nearby wall, geometry and oscillation frequency. The limitations of a two-dimensional approach are then explored through the development of a novel unsteady slender-body theory (USBT) for finite-length cylinders, an asymptotic treatment of which offers corrections to traditional resistive-force-theory (RFT) methods by accounting for geometric factors and flow inertia. These ideas are then extended to the study of thin rectangular plates. Two key parameters are identified which promote two-dimensionality in the flow, namely the frequency of oscillation and the proximity of a nearby boundary. We then examine flexible cylinders and plates by coupling the hydrodynamics to linearized elastic beam and plate equations, which simulate the hydrodynamically-damped high-speed deformable motion of the AFM's cantilever, when driven either externally or by Brownian motion. In the latter case, we adopt an approach which offers notable improvements over the most advanced method currently available to the AFM community

Public experiences of mass casualty decontamination

In this article, we analyze feedback from simulated casualties who took part in field exercises involving mass decontamination, to gain an understanding of how responder communication can affect people’s experiences of and compliance with decontamination. We analyzed questionnaire data gathered from 402 volunteers using the framework approach, to provide an insight into the public’s experiences of decontamination and how these experiences are shaped by the actions of emergency responders. Factors that affected casualties’ experiences of the econtamination process included the need for greater practical information and better communication from responders, and the need for privacy. Results support previous findings from small-scale incidents that involved decontamination in showing that participants wanted better communication from responders during the process of decontamination, including more practical information, and that the failure of responders to communicate effectively with members of the public led to anxiety about the decontamination process. The similarity between the findings from the exercises described in this article and previous research into real incidents involving decontamination suggests that field exercises provide a useful way to examine the effect of responder communication strategies on the public’s experiences of decontamination. Future exercises should examine in more detail the effect of various communication strategies on the public’s experiences of decontamination. This will facilitate the development of evidence-based communication strategies intended to reduce anxiety about decontamination and increase compliance among members of the public during real-life incidents that involve mass decontamination

The drag on a microcantilever oscillating near a wall

Motivated by devices such as the atomic force microscope, we compute the drag experienced by a cylindrical body of circular or rectangular cross-section oscillating at small amplitude near a plane wall. The body lies parallel to the wall and oscillates normally to it; the body is assumed to be long enough for the dominant flow to be two-dimensional. The flow is parameterized by a frequency parameter γ² (a Strouhal number) and the wall–body separation Δ (scaled on body radius). Numerical solutions of the unsteady Stokes equations obtained using finite-difference computations in bipolar coordinates (for circular cross-sections) and boundary-element computations (for rectangular cross-sections) are used to determine the drag on the body. Numerical results are validated and extended using asymptotic predictions (for circular cylinders) obtained at all extremes of (γ, Δ)-parameter space. Regions in parameter space for which the wall has a significant effect on drag are identified.R. J. Clarke, S. M. Cox, P. M. Williams and O. E. Jense

Identification of mechanically representative samples for aperiodic honeycombs

Honeycombs are a class of metamaterials widely used in engineering. Traditionally they have been comprised of periodic arrays of hexagonal, triangular and square cells however there have been many studies into novel variations of these lattices. Recent works have focused on the mechanical properties of metamaterials based on lattices with aperiodic order. This promising new field of study offers the potential for a wider range of available mechanical properties. With this potential comes challenges in producing, testing and simulating these structures. Analysis cannot be carried out on a unit cell as aperiodic patterns lack translational symmetry. Furthermore, it is unknown how much of the structure is required for a representative sample. This study uses a statistical approach to investigate how patch size influences the ability to accurately estimate the mechanical properties of aperiodic honeycombs. By exploiting a numerical framework requiring minimal computational resources, 1600 simulations were carried out on randomly sampled patches. This was supported by mechanically testing a targeted set of 40 additively manufactured honeycombs. It was found that in most cases increases in patch size resulted in consistent reductions in variation of properties with the samples varying by less than 5.3% from the mean when considering Young’s modulu

Science with the Second Wide Field and Planetary Camera

With the commencement of Cycle 4 observations, the General Observer community will have access to the second Wide Field and Planetary Camera (WFPC-2), a replacement for the original WFPC instrument. WFPC-2, a wide-field photometric camera which covers the spectrum from 1200 to 10000 Angstroms, will be installed in the Hubble radial bay during the currently manifested December 1992 Shuttle servicing mission. Besides optical correction for the aberrated Hubble primary mirror, the WFPC-2 incorporates evolutionary improvements in photometric imaging capabilities. The CCD sensors, signal chain electronics, filter set, FUV performance, internal calibrations, and operational efficiency have all been improved through new technologies and lessons learned from WFPC operations and Hubble experience since launch. Here we provide an overview of the new instrument, beginning with the assumption that the reader is already familiar with the original WFPC now in service