Silacyclohex-4-enes: novel silene-cycloadducts for organic synthesis

Silenes, compounds containing a Si=c double bond, are highly reactive and are normally observed as transient intermediates which readily dimerise. Evidence for their existence was first reported in 1967 by Gusel'nikov and Flowers.(^1) However, since then only minimal effort has been made to exploit their unique reactivity in organic synthesis. This thesis describes research concerning the chemistry of silenes and more specifically their Diels-Alder adducts, silacyclohex-4-enes. These cycloadducts were utilised as building blocks for organic synthesis, enabling the total synthesis of prelactone B (R = 'Pr) and an analogue (R = Ph) to be achieved in high yields over 5 steps (Figure I) Figure 1 In addition, a unique application of the Hosomi-Sakurai reaction to the cycloadducts provides access to a unique 1,4-monoprotected diol and tetrahydronaphthalene, both possessing four contiguous chiral centres. This methodology was then applied to the total synthesis of the podophyllotoxin analogue, epipicropodophylin (Figure 2

Photon echo quantum memories in inhomogeneously broadened two level atoms

Here we propose a solid-state quantum memory that does not require spectral holeburning, instead using strong rephasing pulses like traditional photon echo techniques. The memory uses external broadening fields to reduce the optical depth and so switch off the collective atom-light interaction when desired. The proposed memory should allow operation with reasonable efficiency in a much broader range of material systems, for instance Er3+ doped crystals which have a transition at 1.5 um. We present analytic theory supported by numerical calculations and initial experiments.Comment: 7 pages, 8 figure

Freezing properties of alkenyl succinic anhydrides derived from linear isomerised olefins

Alkenyl succinic anhydrides are important specialty chemicals that are used in the paper, oilfield and fuel additives industries. In this paper we investigate the link between the physical properties of alkenyl succinic anhydrides and the identities of their linear alkyl olefin precursors. We describe a straightforward GC analysis of olefin isomer distributions and show that these correlate well with the freezing temperatures of the subsequent alkenyl succinic anhydride products. This allows the identification of olefin isomer profiles that are required to give the desired physical properties in the alkenyl succinic anhydrides; it also provides a method to predict the freezing temperatures of alkenyl succinic anhydrides synthesised from a particular supply of olefin

Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage

Coherent control of collective spontaneous emission in an extended atomic ensemble resonantly interacting with single-photon wave packets is analyzed. A scheme for coherent manipulation of collective atomic states is developed such that superradiant states of the atomic system can be converted into subradiant ones and vice versa. Possible applications of such a scheme for optical quantum state storage and single-photon wave packet shaping are discussed. It is shown that also in the absence of inhomogeneous broadening of the resonant line, single-photon wave packets with arbitrary pulse shape may be recorded as a subradiant state and reconstructed even although the duration of the wave packets is larger than the superradiant life-time. Specifically the applicability for storing time-bin qubits, which are used in quantum cryptography is analyzed.Comment: 11 pages, 4 figures, submitted to PR

Professional male rugby union players’ perceived psychological recovery and physical regeneration during the off-season

Objectives: We explored male professional rugby union players’ experiences and perceptions of their mental and physical health and well-being across the northern hemisphere off-season.Methods: 34 professional male rugby union players participated in individual semi-structured interviews (mean (SD) age=27.5 (4.3) years). Interviews were recorded, transcribed verbatim, and analysed using reflexive thematic analysis.Results: The off-season was characterised by three phases players undergo to preserve their mental and physical health and well-being to recover from the previous season and regenerate in preparation for the upcoming season. These included decompression from previous season, cognitive detachment from the rugby environment, and preparation for pre-season. Successful progression through all three phases was influenced by several variables (work and life demands, contextual factors, experience level). Recovery and regeneration strategies focused on physical distancing/getting away from the rugby environment to cognitively detach. Injured players appear an at-risk sub-group for threats to mental well-being (isolation, anxiety, reduced sense of achievement) as a result of reduced or minimal time away from the workplace due to treatment obligations. Younger professionals are a sub-group at risk of overtraining/injury due to inadequate rest, especially as this group are least likely to seek support/guidance.Conclusions: This study is the first investigation into male professional rugby union players’ experiences and perceptions of their mental and physical health and well-being across the off-season period. It highlights the distinct phases players undertake to mentally recover and regenerate and the need to consider education and support for potential at risk sub-groups

The evolution of bits and bottlenecks in a scientific workflow trying to keep up with technology: Accelerating 4D image segmentation applied to nasa data

In 2016, a team of earth scientists directly engaged a team of computer scientists to identify cyberinfrastructure (CI) approaches that would speed up an earth science workflow. This paper describes the evolution of that workflow as the two teams bridged CI and an image segmentation algorithm to do large scale earth science research. The Pacific Research Platform (PRP) and The Cognitive Hardware and Software Ecosystem Community Infrastructure (CHASE-CI) resources were used to significantly decreased the earth science workflow's wall-clock time from 19.5 days to 53 minutes. The improvement in wall-clock time comes from the use of network appliances, improved image segmentation, deployment of a containerized workflow, and the increase in CI experience and training for the earth scientists. This paper presents a description of the evolving innovations used to improve the workflow, bottlenecks identified within each workflow version, and improvements made within each version of the workflow, over a three-year time period

Semi-Supervised Learning with Graphs: Covariance Based Superpixels for Hyperspectral Image Classification

In this paper, we present a graph-based semi-supervised framework for hyperspectral image classification. We first introduce a novel superpixel algorithm based on the spectral covariance matrix representation of pixels to provide a better representation of our data. We then construct a superpixel graph, based on carefully considered feature vectors, before performing classification. We demonstrate, through a set of experimental results using two benchmarking datasets, that our approach outperforms three state-of-the-art classification frameworks, especially when an extremely small amount of labelled data is used.Case Studentship with the NP

Strong coupling cavity QED using rare-earth-ion dopants in monolithic resonators: what you can do with a weak oscillator

We investigate the possibility of achieving the strong coupling regime of cavity quantum electrodynamics using rare earth ions as impurities in monolithic optical resonators. We conclude that due to the weak oscillator strengths of the rare earths, it may be possible but difficult, to reach the regime where the single photon Rabi frequency is large compared to both the cavity and atom decay rates. However reaching the regime where the saturation photon and atom numbers are less than one should be much more achievable. We show that in this `bad cavity' regime, transfer of quantum states and an optical phase shift conditional on the state of the atom is still possible, and suggest a method for coherent detection of single dopants.Comment: 10 pages, 6 figure

Role of contrast-enhanced ultrasound (CEUS) in paediatric practice: an EFSUMB position statement

The use of contrast-enhanced ultrasound (CEUS) in adults is well established in many different areas, with a number of current applications deemed off-label, but the use supported by clinical experience and evidence. Paediatric CEUS is also an off-label application until recently with approval specifically for assessment of focal liver lesions. Nevertheless there is mounting evidence of the usefulness of CEUS in children in many areas, primarily as an imaging technique that reduces exposure to radiation, iodinated contrast medium and the patient-friendly circumstances of ultrasonography. This position statement of the European Federation of Societies in Ultrasound and Medicine (EFSUMB) assesses the current status of CEUS applications in children and makes suggestions for further development of this technique