The Experts below are selected from a list of 108 Experts worldwide ranked by ideXlab platform

Walter J. Lorenz - One of the best experts on this subject based on the ideXlab platform.

  • Spin-lattice Relaxation Time Measurement by means of a TurboFLASH technique
    Magnetic resonance in medicine, 1993
    Co-Authors: Stefan Blüml, Lothar R. Schad, Boris Stepanow, Walter J. Lorenz
    Abstract:

    Rapid Measurements of in vivo proton spin-lattice Relaxation Times (T1) in human tissues were performed by magnetic resonance imaging in a 1.5 T whole-body super-conducting MR scanner. The Measurements employ serial TurboFLASH imaging (Snapshot-FLASH) with scan Times for a single experiment below 4 s. Using centric phase encoding order, an appropriate fitling of the T1-parameter from images with minimum motion artifacts is possible. Comparative T1-determination with a multipoint inversion recovery and spin-echo technique was performed on phantoms containing Gd-DTPA solutions with different T1-values. We found a maximum deviation of 3.3% for T1 < 1100 ms and of 12.1% for 1100 ms < T1 < 1700 ms from the results obtained by the IR technique. In vivo Measurements of T1-Relaxation Times were performed in white and grey matter, cerebrospinal fluid, kidney, liver, spleen, muscle, and bone marrow, and yielded values that are in good agreement with reported data.

A Mackay - One of the best experts on this subject based on the ideXlab platform.

  • Nuclear magnetic resonance Relaxation in multiple sclerosis.
    Journal of Neurology Neurosurgery and Psychiatry, 1998
    Co-Authors: Hbw Larsson, Gareth J. Barker, A Mackay
    Abstract:

    OBJECTIVES The theory of Relaxation processes and their Measurements are described. An overview is presented of the literature on Relaxation Time Measurements in the normal and the developing brain, in experimental diseases in animals, and in patients with multiple sclerosis. RESULTS AND CONCLUSION Relaxation Time Measurements provide insight into development of multiple sclerosis plaques, especially the occurrence of oedema, demyelination, and gliosis. There is also evidence that normal appearing white matter in patients with multiple sclerosis is affected. What is now needed are fast and accurate Relaxation Time Measurement procedures, which cover the whole brain. Relaxation Time Measurements could then provide an important tool for studying the pathogenesis of demyelinating diseases and thus be useful in follow up studies.

  • Nuclear magnetic resonance Relaxation in multiple sclerosis.
    Journal of neurology neurosurgery and psychiatry, 1998
    Co-Authors: H B Larsson, Gareth J. Barker, A Mackay
    Abstract:

    The theory of Relaxation processes and their Measurements are described. An overview is presented of the literature on Relaxation Time Measurements in the normal and the developing brain, in experimental diseases in animals, and in patients with multiple sclerosis. Relaxation Time Measurements provide insight into development of multiple sclerosis plaques, especially the occurrence of oedema, demyelination, and gliosis. There is also evidence that normal appearing white matter in patients with multiple sclerosis is affected. What is now needed are fast and accurate Relaxation Time Measurement procedures, which cover the whole brain. Relaxation Time Measurements could then provide an important tool for studying the pathogenesis of demyelinating diseases and thus be useful in follow up studies.

Stefan Blüml - One of the best experts on this subject based on the ideXlab platform.

  • Spin-lattice Relaxation Time Measurement by means of a TurboFLASH technique
    Magnetic resonance in medicine, 1993
    Co-Authors: Stefan Blüml, Lothar R. Schad, Boris Stepanow, Walter J. Lorenz
    Abstract:

    Rapid Measurements of in vivo proton spin-lattice Relaxation Times (T1) in human tissues were performed by magnetic resonance imaging in a 1.5 T whole-body super-conducting MR scanner. The Measurements employ serial TurboFLASH imaging (Snapshot-FLASH) with scan Times for a single experiment below 4 s. Using centric phase encoding order, an appropriate fitling of the T1-parameter from images with minimum motion artifacts is possible. Comparative T1-determination with a multipoint inversion recovery and spin-echo technique was performed on phantoms containing Gd-DTPA solutions with different T1-values. We found a maximum deviation of 3.3% for T1 < 1100 ms and of 12.1% for 1100 ms < T1 < 1700 ms from the results obtained by the IR technique. In vivo Measurements of T1-Relaxation Times were performed in white and grey matter, cerebrospinal fluid, kidney, liver, spleen, muscle, and bone marrow, and yielded values that are in good agreement with reported data.

T D Bradley - One of the best experts on this subject based on the ideXlab platform.

  • ground state atomic polarization Relaxation Time Measurement of rb filled hypocycloidal core shaped kagome hc pcf
    Journal of Physics B, 2016
    Co-Authors: T D Bradley, J J Mcferran, Ekaterina Ilinova, Jenny Jouin, Philippe Thomas, Benoit Debord, M Alharbi, Frederic Gerome, F Benabid
    Abstract:

    We report on the Measurement of ground-state atomic polarization Relaxation Time of Rb vapor confined in five different hypocycloidal core-shape Kagome hollow-core photonic crystal fibers made with uncoated silica glass. We are able to distinguish between wall-collision and transit-Time effects in an optical waveguide and deduce the contribution of the atom's dwell Time at the core wall surface. In contrast with conventional macroscopic atomic cell configuration, and in agreement with Monte Carlo simulations, the measured Relaxation Times were found to be at least one order of magnitude longer than the limit set by atom-wall collisional from thermal atoms. This extended Relaxation Time is explained by the combination of a stronger contribution of the slow atoms in the atomic polarization build-up, and of the relatively significant contribution of dwell Time to the Relaxation process of the ground state polarization.

  • ground state atomic polarization Relaxation Time Measurement of rb filled hypocycloidal core shaped kagome hc pcf
    arXiv: Atomic Physics, 2015
    Co-Authors: T D Bradley, J J Mcferran, Ekaterina Ilinova, Jenny Jouin, Philippe Thomas, Benoit Debord, M Alharbi, Frederic Gerome, F Benabid
    Abstract:

    We report on the Measurement of ground state atomic polarization Relaxation tile of Rb vapor confined in five different hypocycloidal core shape Kagome hollow core photonic crystal fibers made with uncoated silica glass. We are able to distinguish between wall-collision and transit-Time effects in optical waveguide and deduce the contribution of the atom's dwell Time at the core wall surface. In contrast with convetional macroscopic atomic cell configuration, and in agreement with Monte Carlo simulations, the measured Relaxation Times were found to be at least one order of magnitude longer than the limit set by the atom-wall collisional Relaxation from thermal atoms. This extended Relaxation Time is explained by the combination of a stronger contribution of the slow atoms in the atomic polarization build-up, and of the relatively significant contribution of dwell Time to the Relaxation process of the ground state polarization.

  • atomic polarization Relaxation Time Measurement of rb filled hypocycloidal core shape kagome hc pcf
    Conference on Lasers and Electro-Optics, 2013
    Co-Authors: T D Bradley, J J Mcferran, Ekaterina Ilinova, Jenny Jouin, Philippe Thomas, F Benabid
    Abstract:

    We measured atomic polarization Relaxation-Time in PDMS coated and uncoated rubidium-loaded hypocycloidal-core Kagome HC-PCF. The measured Relaxation-Times of 32μs and 24μs in PDMS coated and uncoated fibers are longer two-orders-of-magnitude than the wall-collision-limited Relaxation Time.

F Benabid - One of the best experts on this subject based on the ideXlab platform.

  • ground state atomic polarization Relaxation Time Measurement of rb filled hypocycloidal core shaped kagome hc pcf
    Journal of Physics B, 2016
    Co-Authors: T D Bradley, J J Mcferran, Ekaterina Ilinova, Jenny Jouin, Philippe Thomas, Benoit Debord, M Alharbi, Frederic Gerome, F Benabid
    Abstract:

    We report on the Measurement of ground-state atomic polarization Relaxation Time of Rb vapor confined in five different hypocycloidal core-shape Kagome hollow-core photonic crystal fibers made with uncoated silica glass. We are able to distinguish between wall-collision and transit-Time effects in an optical waveguide and deduce the contribution of the atom's dwell Time at the core wall surface. In contrast with conventional macroscopic atomic cell configuration, and in agreement with Monte Carlo simulations, the measured Relaxation Times were found to be at least one order of magnitude longer than the limit set by atom-wall collisional from thermal atoms. This extended Relaxation Time is explained by the combination of a stronger contribution of the slow atoms in the atomic polarization build-up, and of the relatively significant contribution of dwell Time to the Relaxation process of the ground state polarization.

  • ground state atomic polarization Relaxation Time Measurement of rb filled hypocycloidal core shaped kagome hc pcf
    arXiv: Atomic Physics, 2015
    Co-Authors: T D Bradley, J J Mcferran, Ekaterina Ilinova, Jenny Jouin, Philippe Thomas, Benoit Debord, M Alharbi, Frederic Gerome, F Benabid
    Abstract:

    We report on the Measurement of ground state atomic polarization Relaxation tile of Rb vapor confined in five different hypocycloidal core shape Kagome hollow core photonic crystal fibers made with uncoated silica glass. We are able to distinguish between wall-collision and transit-Time effects in optical waveguide and deduce the contribution of the atom's dwell Time at the core wall surface. In contrast with convetional macroscopic atomic cell configuration, and in agreement with Monte Carlo simulations, the measured Relaxation Times were found to be at least one order of magnitude longer than the limit set by the atom-wall collisional Relaxation from thermal atoms. This extended Relaxation Time is explained by the combination of a stronger contribution of the slow atoms in the atomic polarization build-up, and of the relatively significant contribution of dwell Time to the Relaxation process of the ground state polarization.

  • atomic polarization Relaxation Time Measurement of rb filled hypocycloidal core shape kagome hc pcf
    Conference on Lasers and Electro-Optics, 2013
    Co-Authors: T D Bradley, J J Mcferran, Ekaterina Ilinova, Jenny Jouin, Philippe Thomas, F Benabid
    Abstract:

    We measured atomic polarization Relaxation-Time in PDMS coated and uncoated rubidium-loaded hypocycloidal-core Kagome HC-PCF. The measured Relaxation-Times of 32μs and 24μs in PDMS coated and uncoated fibers are longer two-orders-of-magnitude than the wall-collision-limited Relaxation Time.