| 1. |
- Beecham, Ashley H, et al.
(författare)
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Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis.
- 2013
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Ingår i: Nature genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 45:11, s. 1353-60
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Tidskriftsartikel (refereegranskat)abstract
- Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 1.0 × 10(-4)). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 subjects with multiple sclerosis and 26,703 healthy controls. In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 5.0 × 10(-8)), 3 of which we found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants at 103 discrete loci outside of the major histocompatibility complex. With high-resolution Bayesian fine mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals.
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| 2. |
- Sugiyama, Jun, et al.
(författare)
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How Li diffusion in spinel Li[Ni1/2Mn3/2]O4 is seen with μ ±SR
- 2021
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Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156.
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Tidskriftsartikel (refereegranskat)abstract
- The diffusive behavior in a spinel-type Li+ ion battery material, Li[Ni1/2Mn3/2]O4, has been studied with positive and negative muon spin rotation and relaxation (μ±SR) measurements in the temperature range between 200 and 400 K using a powder sample. The implanted μ+ locates at an interstitial site near O2- ion so as to form a O-H like bond, while the implanted μ- is mainly captured by an oxygen nucleus, resulting in the formation of muonic oxygen. This means that local magnetic environments in Li[Ni1/2Mn3/2]O4 were investigated from the two different sites in the lattice, i.e., one is an interstitial site for μ+SR and the other is an oxygen site for μ-SR. Since both μ+SR and μ-SR detected an increase in the fluctuation rate of a nuclear magnetic field for temperatures above 200 K, the origin of this increase is clearly confirmed as Li diffusion. Assuming a random walk process with the hopping of thermally activated Li+ between a regular Li site and the nearest neighboring vacant octahedral sites, a self-diffusion coefficient of Li+ was found to range above 10-11 cm2/s at temperatures above 250 K with an activation energy of about 0.06 eV.
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| 3. |
- Sugiyama, Jun, et al.
(författare)
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Lithium diffusion in LiMnPO4 detected with mu +/- SR
- 2020
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- Positive- and negative-muon spin rotation and relaxation (mu(+/-) SR) was first used to investigate fluctuations of nuclear magnetic fields in an olivine-type battery material, LiMnPO4, in order to clarify the diffusive species, namely, to distinguish between a mu(+) hopping among interstitial sites and Li+ ions diffusing in the LiMnPO4 lattice. Muon diffusion can only occur in mu+SR, because the implanted mu(-) forms a stable muonic atom at the lattice site, and therefore any change in linewidth measured with mu-SR must be due to Li+ diffusion. Since the two measurements exhibit a similar increase in the field fluctuation rate with temperature above 100 K, it is confirmed that Li+ ions are in fact diffusing. The diffusion coefficient of Li+ at 300 K and its activation energy were estimated to be 1.4(3) x 10(-10) cm(2)/s and 0.19(3) eV, respectively. Such combined mu(SR)-S-+/- measurements are thus shown to be a suitable tool for detecting ion diffusion in solid-state energy materials.
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| 4. |
- Sugiyama, Jun, et al.
(författare)
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Negative muon spin rotation and relaxation on superconducting MgB 2
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Konferensbidrag (refereegranskat)abstract
- The internal nuclear magnetic field in a superconducting MgB2 powder sample was studied with a μ- SR technique. Although the past μ +SR study on MgB2 reported the appearance of a dynamic behavior even below Tc due to μ + diffusion, μ- SR shows a static behavior in the whole temperature range measured, as expected. The ZF-μ- SR spectra do not suggest any appearance of additional magnetic field below Tc within the experimental accuracy. Considering the small asymmetry of the μ- SR signal, it is a challenge to detect the appearance of an internal magnetic field below Tc caused by the time reversal symmetry breaking.
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| 5. |
- Sugiyama, Jun, et al.
(författare)
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Negative muon spin rotation and relaxation on superconducting MgB2
- 2023
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Ingår i: Proceedings 15th International Conference on Muon Spin Rotation, Relaxation and Resonance (SR). - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- The internal nuclear magnetic field in a superconducting MgB2 powder sample was studied with a mu-SR technique. Although the past mu+SR study on MgB2 reported the appearance of a dynamic behavior even below T-c due to mu(+) diffusion, mu-SR shows a static behavior in the whole temperature range measured, as expected. The ZF-mu-SR spectra do not suggest any appearance of additional magnetic field below T-c within the experimental accuracy. Considering the small asymmetry of the mu-SR signal, it is a challenge to detect the appearance of an internal magnetic field below Tc caused by the time reversal symmetry breaking.
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