| 1. |
- Docherty, Anna R, et al.
(författare)
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GWAS Meta-Analysis of Suicide Attempt: Identification of 12 Genome-Wide Significant Loci and Implication of Genetic Risks for Specific Health Factors.
- 2023
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Ingår i: The American journal of psychiatry. - : American Psychiatric Association Publishing. - 1535-7228 .- 0002-953X. ; 180:10, s. 723-738
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Tidskriftsartikel (refereegranskat)abstract
- Suicidal behavior is heritable and is a major cause of death worldwide. Two large-scale genome-wide association studies (GWASs) recently discovered and cross-validated genome-wide significant (GWS) loci for suicide attempt (SA). The present study leveraged the genetic cohorts from both studies to conduct the largest GWAS meta-analysis of SA to date. Multi-ancestry and admixture-specific meta-analyses were conducted within groups of significant African, East Asian, and European ancestry admixtures.This study comprised 22 cohorts, including 43,871 SA cases and 915,025 ancestry-matched controls. Analytical methods across multi-ancestry and individual ancestry admixtures included inverse variance-weighted fixed-effects meta-analyses, followed by gene, gene-set, tissue-set, and drug-target enrichment, as well as summary-data-based Mendelian randomization with brain expression quantitative trait loci data, phenome-wide genetic correlation, and genetic causal proportion analyses.Multi-ancestry and European ancestry admixture GWAS meta-analyses identified 12 risk loci at p values <5×10-8. These loci were mostly intergenic and implicated DRD2, SLC6A9, FURIN, NLGN1, SOX5, PDE4B, and CACNG2. The multi-ancestry SNP-based heritability estimate of SA was 5.7% on the liability scale (SE=0.003, p=5.7×10-80). Significant brain tissue gene expression and drug set enrichment were observed. There was shared genetic variation of SA with attention deficit hyperactivity disorder, smoking, and risk tolerance after conditioning SA on both major depressive disorder and posttraumatic stress disorder. Genetic causal proportion analyses implicated shared genetic risk for specific health factors.This multi-ancestry analysis of suicide attempt identified several loci contributing to risk and establishes significant shared genetic covariation with clinical phenotypes. These findings provide insight into genetic factors associated with suicide attempt across ancestry admixture populations, in veteran and civilian populations, and in attempt versus death.
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| 2. |
- Mullins, Niamh, et al.
(författare)
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Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors
- 2022
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Ingår i: Biological Psychiatry. - : Elsevier. - 0006-3223 .- 1873-2402. ; 91:3, s. 313-327
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders.METHODS: We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors.RESULTS: Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged.CONCLUSIONS: Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.
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| 3. |
- Zhou Hagström, Nanna, 1993-, et al.
(författare)
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Megahertz-rate ultrafast X-ray scattering and holographic imaging at the European XFEL
- 2022
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Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 1454-1464
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Tidskriftsartikel (refereegranskat)abstract
- The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, results from the first megahertz-repetition-rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL are presented. The experimental capabilities that the SCS instrument offers, resulting from the operation at megahertz repetition rates and the availability of the novel DSSC 2D imaging detector, are illustrated. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative, providing an ideal test-bed for operation at megahertz rates. Our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
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| 4. |
- Fan, Tingting, et al.
(författare)
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Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:46, s. 14206-14211
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 mu m, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N-4,N-5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.
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| 5. |
- Jangid, Rahul, et al.
(författare)
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Extreme Domain Wall Speeds under Ultrafast Optical Excitation
- 2023
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 131:25
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved ultrafast EUV magnetic scattering was used to test a recent prediction of > 10 km/s domain wall speeds by optically exciting a magnetic sample with a nanoscale labyrinthine domain pattern. Ultrafast distortion of the diffraction pattern was observed at markedly different timescales compared to the magnetization quenching. The diffraction pattern distortion shows a threshold dependence with laser fluence, not seen for magnetization quenching, consistent with a picture of domain wall motion with pinning sites. Supported by simulations, we show that a speed of approximate to 66 km/s for highly curved domain walls can explain the experimental data. While our data agree with the prediction of extreme, nonequilibrium wall speeds locally, it differs from the details of the theory, suggesting that additional mechanisms are required to fully understand these effects.
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| 6. |
- Svedberg, Erik B.
(författare)
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Non-equilibrium Surfaces of Metallic Thin Films
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Growth and structural characterization of metallic multilayers have been performed on the Mo/W, Mo/V and Ag/Ni systems utilizing magnetron sputtering under ultra-high-vacuum deposition conditions. Structural characterization has been performed both in situ and ex situ with several electron beam probing techniques as well as x-ray diffraction. The investigations have focused primarily on the relationship between the deposition process and the resulting layer quality including studies of the initial conditions for the layers, as induced by the substrate and its interaction with the initial metal layer. For the Mo/W system, I have established by x-ray diffraction that magnetron sputtering creates asymmetric interfaces in single-crystal superlattices, and that this asymmetry is caused by the difference in energies of the energetic neutrals impinging on the surface during growth. With existing knowledge of the Mo/V system, a technique for assessing the relationship between surface microstructure and growth conditions was evaluated. The methodology employed in situ reflection high energy electron diffraction (RHEED) analysis during magnetron sputtering; a technique not widely used due to the difficulties of incorporating a RHEED system into a sputtering chamber with its high gas pressures during the deposition process. This work makes it possible to determine the effect of changed process parameters directly, even though post-processing of the data provided both additional information and better statistics. For both the Mo/W and Mo/V material systems, the substrate was MgO and the initial metal layer was Mo. To fully assess the initial conditions that will determine the growth of the metallic superlattices on the ceramic substrate, in situ scanning tunnelling microscopy was employed in conjunction with electron beam techniques. I have shown independently by both in situ low energy electron diffraction (LEED) and time-resolved in situ RHEED measurements that oxygen is present on the Mo surface during the initial stages, up to ~300Å, of Mo deposition, and that it originates from the oxygen within the MgO substrate. The oxygen causes the growing Mo surface to continuously reconstruct with the (×), p(2x2) and c(2x2) structures and, for the first time, scanning tunnelling microscope images of the p(2x2) and c(2x2) reconstructions are shown. The measurements also reveal a surface which is typically interspersed with random 2x2 holes, only visible by techniques such as scanning tunnelling microscopy. Their non-periodic nature prevents observation with diffraction based techniques. In pre-studies of the Ag/Ni system, the growth temperature dependence of dc-magnetron sputter deposited Ni films on MgO substrateswas determined by x-ray diffraction. In the interval of 20°C to 700° C, three temperature ranges were observed: (1) CD at room temperature, the texture of the Ni film was <0 2 2> coexistingwith <1 -4 1> and traces of <0 0 2> texture; (2) from 100°C to 200°C, a singleNi domain of <0 0 2> texture was formed; and (3) @ from 300°C to 700°C, the texture was <7 5 -1> which at higher temperatures gradually became better defined. The most useful Ni films are likely to be the smooth single-crystal films grown at 100-200°C . The reason for these textural changes is the increased Ni atom mobility with temperature. In one example, the change from single crystallinity to <7 5 -1> texture at around 250°C, this change accommodates both the strong Ni metal-metal bonds as well as placing each interfacial Ni atom in the preferred position, directly on top of an O atom in the MgO, with a minimal mismatch between the two crystal lattices. These atomic rearrangements have a higher degree of probability at the elevated temperature above ~250°C. All the depositions within this thesis are done far from equilibrium conditions, where the knowledge of growth behaviour is still incomplete. Hopefully this work will take that knowledge one small step further.
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| 7. |
- Turenne, Diego, et al.
(författare)
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Nonequilibrium sub–10 nm spin-wave soliton formation in FePt nanoparticles
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:13
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic nanoparticles such as FePt in the L10 phase are the bedrock of our current data storage technology. As the grains become smaller to keep up with technological demands, the superparamagnetic limit calls for materials with higher magnetocrystalline anisotropy. This, in turn, reduces the magnetic exchange length to just a few nanometers, enabling magnetic structures to be induced within the nanoparticles. Here, we describe the existence of spin-wave solitons, dynamic localized bound states of spin-wave excitations, in FePt nanoparticles. We show with time-resolved x-ray diffraction and micromagnetic modeling that spin-wave solitons of sub–10 nm sizes form out of the demagnetized state following femtosecond laser excitation. The measured soliton spin precession frequency of 0.1 THz positions this system as a platform to develop novel miniature devices.
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| 8. |
- Unikandanunni, Vivek, et al.
(författare)
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Anisotropic ultrafast spin dynamics in epitaxial cobalt
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:23
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the ultrafast spin dynamics in an epitaxial hcp(11⎯⎯00) cobalt thin film. By performing pump-probe magneto-optical measurements with the magnetization along either the easy or hard magnetic axis, we determine the demagnetization and recovery time for the two axes. We observe an average of 33% slower dynamics along the easy magnetization axis, which we attribute to magneto-crystalline anisotropy of the electron-phonon coupling, supported by our ab initio calculations. This points toward an unambiguous and previously undisclosed role of anisotropic electron–lattice coupling in ultrafast magnetism.
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| 9. |
- Unikandanunni, Vivek, 1993-, et al.
(författare)
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Inertial Spin Dynamics in Epitaxial Cobalt Films
- 2022
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 129:23
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the spin dynamics driven by terahertz magnetic fields in epitaxial thin films of cobalt in its three crystalline phases. The terahertz magnetic field generates a torque on the magnetization which causes it to precess for about 1 ps, with a subpicosecond temporal lag from the driving force. Then, the magnetization undergoes natural damped THz oscillations at a frequency characteristic of the crystalline phase. We describe the experimental observations solving the inertial Landau-Lifshitz-Gilbert equation. Using the results from the relativistic theory of magnetic inertia, we find that the angular momentum relaxation time η is the only material parameter needed to describe all the experimental evidence. Our experiments suggest a proportionality between η and the strength of the magnetocrystalline anisotropy.
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| 10. |
- Vaskivskyi, Igor, et al.
(författare)
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Element-Specific Magnetization Dynamics in Co-Pt Alloys Induced by Strong Optical Excitation
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:21, s. 11714-11721
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Tidskriftsartikel (refereegranskat)abstract
- Ever since its first observation, the microscopic origin of ultrafast magnetization dynamics has been actively debated. Even more questions arise when considering composite materials featuring a combination of intrinsic and proximity-induced magnetic moments. Currently, it is unknown whether the specific ultrafast dynamics of different sublattices in the popular ferromagnets consisting of 3d (Co, Fe) and 4d, 5d (Pd, Pt) transition metals are playing a crucial role in various effects, including all-optical magnetization switching. Here we investigate the element-specific dynamics of Co-Pt alloys on femtosecond and picosecond time scales using magneto-optical spectroscopy in the extended ultraviolet (EUV) region. Our results reveal that despite the proximity-induced nature of the magnetization of Pt atoms, the two sublattices in the alloy can have different responses to the optical excitation featuring distinct demagnetization rates. Additionally we show that it is important to consider the modification of magnetic anisotropy in opto-magnetic experiments as the vast majority of them are sensitive only to a single projection of the magnetic moment on the predefined axis, which may lead to experimental artifacts.
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