Optimisation of xenon-rich stopped-flow spin-exchange optical pumping for functional lung imaging

Spin-exchange optical pumping (SEOP) is a hyperpolarisation method used in the hyperpolarisation of noble gases and can enhance nuclear spin polarisation by five orders of magnitude. Hyperpolarised (HP) 129-Xe has many properties that make it ideally suited to clinical lung imaging, but since its first demonstration in animals in 1994 and humans in 1996, translation to the clinic has been hampered by challenges associated with scaling up production. Within this thesis, construction and demonstration of a clinical-scale stopped-flow hyperpolariser is described, the design of which is based on the record holding XeUS and XeNA polarisers developed previously by our consortium, which had aimed to address the issue of production scale-up. Modifications enhancing the ease of operation and utility in-clinic are presented, as are modifications that reduce the capital cost of such a system. These include a re-design of the gas manifold and the development of a low-cost low-field NMR spectrometer which achieved an SNR of 125 at a cost of ~$300, a 13-fold improvement in cost/SNR compared with the existing spectrometer at a saving of ~$19,000. In continuous-flow 129-Xe polarisers there has long been a discrepancy in the polarisation achieved and that predicted by the standard model of SEOP which was shown recently to be due to the presence of rubidium clusters. Here, the standard model is applied to- and validated for the first time against the stopped-flow regime. The validated model is used to explore parameter space to identify the most effective ways to increase production yield in future stopped-flow polarisers. Stopped-flow SEOP in the xenon-rich regime presents unique thermal management problems due to the absence of gas flow and abundance of poorly thermally conductive, Rb spin destroying Xe. Raman spectroscopy is used to spatially examine in-cell thermal behaviour under steady-state and turbulent 'rubidium runaway' conditions as a function of temperature and Xe density and the beneficial impact of adding thermally conductive helium to the standard N2-Xe gas mix is demonstrated. Hybrid Rb-Cs-Xe SEOP is demonstrated for the first time and examined using in-situ NMR and Raman spectroscopies. High polarisations of ~50% were obtained. Finally, progress on the HP-Xe clinical trial is presented to illustrate the impact of the 4-fold increase in SNR that will come with the installation of the new N-XeUS stopped-flow polariser

Optimisation of xenon-rich stopped-flow spin-exchange optical pumping for functional lung imaging

Spin-exchange optical pumping (SEOP) is a hyperpolarisation method used in the hyperpolarisation of noble gases and can enhance nuclear spin polarisation by five orders of magnitude. Hyperpolarised (HP) 129-Xe has many properties that make it ideally suited to clinical lung imaging, but since its first demonstration in animals in 1994 and humans in 1996, translation to the clinic has been hampered by challenges associated with scaling up production. Within this thesis, construction and demonstration of a clinical-scale stopped-flow hyperpolariser is described, the design of which is based on the record holding XeUS and XeNA polarisers developed previously by our consortium, which had aimed to address the issue of production scale-up. Modifications enhancing the ease of operation and utility in-clinic are presented, as are modifications that reduce the capital cost of such a system. These include a re-design of the gas manifold and the development of a low-cost low-field NMR spectrometer which achieved an SNR of 125 at a cost of ~$300, a 13-fold improvement in cost/SNR compared with the existing spectrometer at a saving of ~$19,000. In continuous-flow 129-Xe polarisers there has long been a discrepancy in the polarisation achieved and that predicted by the standard model of SEOP which was shown recently to be due to the presence of rubidium clusters. Here, the standard model is applied to- and validated for the first time against the stopped-flow regime. The validated model is used to explore parameter space to identify the most effective ways to increase production yield in future stopped-flow polarisers. Stopped-flow SEOP in the xenon-rich regime presents unique thermal management problems due to the absence of gas flow and abundance of poorly thermally conductive, Rb spin destroying Xe. Raman spectroscopy is used to spatially examine in-cell thermal behaviour under steady-state and turbulent 'rubidium runaway' conditions as a function of temperature and Xe density and the beneficial impact of adding thermally conductive helium to the standard N2-Xe gas mix is demonstrated. Hybrid Rb-Cs-Xe SEOP is demonstrated for the first time and examined using in-situ NMR and Raman spectroscopies. High polarisations of ~50% were obtained. Finally, progress on the HP-Xe clinical trial is presented to illustrate the impact of the 4-fold increase in SNR that will come with the installation of the new N-XeUS stopped-flow polariser

Electric Field Control of Shallow Donor Impurities in Silicon

We present a tight-binding study of donor impurities in Si, demonstrating the adequacy of this approach for this problem by comparison with effective mass theory and experimental results. We consider the response of the system to an applied electric field: donors near a barrier material and in the presence of an uniform electric field may undergo two different ionization regimes according to the distance of the impurity to the Si/barrier interface. We show that for impurities ~ 5 nm below the barrier, adiabatic ionization is possible within switching times of the order of one picosecond, while for impurities ~ 10 nm or more below the barrier, no adiabatic ionization may be carried out by an external uniform electric field. Our results are discussed in connection with proposed Si:P quantum computer architectures.Comment: 18 pages, 6 figures, submitted to PR

Opacity calculation for target physics using the ABAKO/RAPCAL code

Radiative properties of hot dense plasmas remain a subject of current interest since they play an important role in inertial confinement fusion (ICF) research, as well as in studies on stellar physics. In particular, the understanding of ICF plasmas requires emissivities and opacities for both hydro-simulations and diagnostics. Nevertheless, the accurate calculation of these properties is still an open question and continuous efforts are being made to develop new models and numerical codes that can facilitate the evaluation of such properties. In this work the set of atomic models ABAKO/RAPCAL is presented, as well as a series of results for carbon and aluminum to show its capability for modeling the population kinetics of plasmas in both LTE and NLTE regimes. Also, the spectroscopic diagnostics of a laser-produced aluminum plasma using ABAKO/RAPCAL is discussed. Additionally, as an interesting application of these codes, fitting analytical formulas for Rosseland and Planck mean opacities for carbon plasmas are reported. These formulas are useful as input data in hydrodynamic simulation of targets where the computation task is so hard that in line computation with sophisticated opacity codes is prohibitive

The effects of an experimental programme to support students’ autonomy on the overt behaviours of physical education teachers

Although the benefits of autonomy supportive behaviours are now well established in the literature, very few studies have attempted to train teachers to offer a greater autonomy support to their students. In fact, none of these studies has been carried out in physical education (PE). The purpose of this study is to test the effects of an autonomy-supportive training on overt behaviours of teaching among PE teachers. The experimental group included two PE teachers who were first educated on the benefits of an autonomy supportive style and then followed an individualised guidance programme during the 8 lessons of a teaching cycle. Their behaviours were observed and rated along 3 categories (i.e., autonomy supportive, neutral and controlling) and were subsequently compared to those of three teachers who formed the control condition. The results showed that teachers in the experimental group used more autonomy supportive and neutral behaviours than those in the control group, but no difference emerged in relation to controlling behaviours. We discuss the implications for schools of our findings

Superstripes and complexity in high-temperature superconductors

While for many years the lattice, electronic and magnetic complexity of high-temperature superconductors (HTS) has been considered responsible for hindering the search of the mechanism of HTS now the complexity of HTS is proposed to be essential for the quantum mechanism raising the superconducting critical temperature. The complexity is shown by the lattice heterogeneous architecture: a) heterostructures at atomic limit; b) electronic heterogeneity: multiple components in the normal phase; c) superconducting heterogeneity: multiple superconducting gaps in different points of the real space and of the momentum space. The complex phase separation forms an unconventional granular superconductor in a landscape of nanoscale superconducting striped droplets which is called the "superstripes" scenario. The interplay and competition between magnetic orbital charge and lattice fluctuations seems to be essential for the quantum mechanism that suppresses thermal decoherence effects at an optimum inhomogeneity.Comment: 20 pages, 3 figures; J. Supercon. Nov. Mag. 201

Sloan Digital Sky Survey IV: mapping the Milky Way, nearby galaxies, and the distant universe

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median ). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July