| 1. |
- Baltas, Konstantinos, et al.
(författare)
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The role of resource orchestration in humanitarian operations : a COVID-19 case in the US healthcare
- 2022
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Ingår i: Annals of Operations Research. - : Springer. - 0254-5330 .- 1572-9338.
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the role of resource allocation in alleviating the impact on from disruptions in healthcare operations. We draw on resource orchestration theory and analyse data stemming from US healthcare to discuss how the US healthcare system structured, bundled and reconfigured resources (i.e. number of hospital beds, and vaccines) during the COVID-19 pandemic. Following a comprehensive and robust econometric analysis of two key resources (i.e. hospital beds and vaccines), we discuss its effect on the outcomes of the pandemic measured in terms of confirmed cases and deaths, and draw insights on how the learning curve effect and other factors might influence in the efficient and effective control of the pandemic outcomes through the resource usage. Our contribution lies in revealing how different resources are orchestrated (structured, bundled, and leveraged) to help planning responses to and dealing with the disruptions to create resilient humanitarian operations. Managerial implications, limitations and future research directions are also discussed.
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| 2. |
- Fernandez-Rozadilla, Ceres, et al.
(författare)
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Deciphering colorectal cancer genetics through multi-omic analysis of 100,204 cases and 154,587 controls of European and east Asian ancestries
- 2023
-
Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 55, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- Colorectal cancer (CRC) is a leading cause of mortality worldwide. We conducted a genome-wide association study meta-analysis of 100,204 CRC cases and 154,587 controls of European and east Asian ancestry, identifying 205 independent risk associations, of which 50 were unreported. We performed integrative genomic, transcriptomic and methylomic analyses across large bowel mucosa and other tissues. Transcriptome- and methylome-wide association studies revealed an additional 53 risk associations. We identified 155 high-confidence effector genes functionally linked to CRC risk, many of which had no previously established role in CRC. These have multiple different functions and specifically indicate that variation in normal colorectal homeostasis, proliferation, cell adhesion, migration, immunity and microbial interactions determines CRC risk. Crosstissue analyses indicated that over a third of effector genes most probably act outside the colonic mucosa. Our findings provide insights into colorectal oncogenesis and highlight potential targets across tissues for new CRC treatment and chemoprevention strategies.
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| 3. |
- Forslund, Ola Kenji, et al.
(författare)
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Intertwined magnetic sublattices in the double perovskite compound LaSrNiReO6
- 2020
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9969 .- 2469-9950. ; 102:14
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Tidskriftsartikel (refereegranskat)abstract
- We report a muon spin rotation (μ+SR) study of the magnetic properties of the double perovskite compound LaSrNiReO6. Using the unique length and time scales of the μ+SR technique, we successfully clarify the magnetic ground state of LaSrNiReO6, which was previously deemed as a spin glass state. Instead, our μ+SR results point toward a long-range dynamically ordered ground state below TC=23 K, for which a static limit is foreseen at T=0. Furthermore, between 23K250 K) state. Our results reveal how two separate yet intertwined magnetic lattices interact within the unique double perovskite structure and the importance of using complementary experimental techniques to obtain a complete understanding of the microscopic magnetic properties of complex materials.
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| 4. |
- Matsubara, Nami, et al.
(författare)
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Cation Distributions and Magnetic Properties of Ferrispinel MgFeMnO4
- 2020
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:24, s. 17970-17980
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure and magnetic properties of the cubic spinel MgFeMnO4 were studied by using a series of in-house techniques along with large-scale neutron diffraction and muon spin rotation spectroscopy in the temperature range between 1.5 and 500 K. The detailed crystal structure is successfully refined by using a cubic spinel structure described by the space group Fd3¯ m. Cations within tetrahedral A and octahedral B sites of the spinel were found to be in a disordered state. The extracted fractional site occupancies confirm the presence of antisite defects, which are of importance for the electrochemical performance of MgFeMnO4 and related battery materials. Neutron diffraction and muon spin spectroscopy reveal a ferrimagnetic order below TC = 394.2 K, having a collinear spin arrangement with antiparallel spins at the A and B sites, respectively. Our findings provide new and improved understanding of the fundamental properties of the ferrispinel materials and of their potential applications within future spintronics and battery devices.
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| 5. |
- Matsubara, Nami, et al.
(författare)
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Magnetism and ion diffusion in honeycomb layered oxide K 2Ni 2TeO 6
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- In the quest for developing novel and efficient batteries, a great interest has been raised for sustainable K-based honeycomb layer oxide materials, both for their application in energy devices as well as for their fundamental material properties. A key issue in the realization of efficient batteries based on such compounds, is to understand the K-ion diffusion mechanism. However, investigation of potassium-ion (K+) dynamics in materials using e.g. NMR and related techniques has so far been very challenging, due to its inherently weak nuclear magnetic moment, in contrast to other alkali ions such as lithium and sodium. Spin-polarised muons, having a high gyromagnetic ratio, make the muon spin rotation and relaxation (μ+SR) technique ideal for probing ions dynamics in these types of energy materials. Here we present a study of the low-temperature magnetic properties as well as K+ dynamics in honeycomb layered oxide material K 2Ni 2TeO 6 using mainly the μ+SR technique. Our low-temperature μ+SR results together with complementary magnetic susceptibility measurements find an antiferromagnetic transition at TN≈ 27 K. Further μ+SR studies performed at higher temperatures reveal that potassium ions (K+) become mobile above 200 K and the activation energy for the diffusion process is obtained as Ea= 121 (13) meV. This is the first time that K+ dynamics in potassium-based battery materials has been measured using μ+SR. Assisted by high-resolution neutron diffraction, the temperature dependence of the K-ion self diffusion constant is also extracted. Finally our results also reveal that K-ion diffusion occurs predominantly at the surface of the powder particles. This opens future possibilities for potentially improving ion diffusion as well as K-ion battery device performance using nano-structuring and surface coatings of the particles.
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| 6. |
- Matsubara, Nami, et al.
(författare)
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Magnetism and ion diffusion in honeycomb layered oxide K2Ni2TeO6
- 2020
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- In the quest for developing novel and efficient batteries, a great interest has been raised for sustainable K-based honeycomb layer oxide materials, both for their application in energy devices as well as for their fundamental material properties. A key issue in the realization of efficient batteries based on such compounds, is to understand the K-ion diffusion mechanism. However, investigation of potassium-ion (K+) dynamics in materials using e.g. NMR and related techniques has so far been very challenging, due to its inherently weak nuclear magnetic moment, in contrast to other alkali ions such as lithium and sodium. Spin-polarised muons, having a high gyromagnetic ratio, make the muon spin rotation and relaxation (mu+SR) technique ideal for probing ions dynamics in these types of energy materials. Here we present a study of the low-temperature magnetic properties as well as K+ dynamics in honeycomb layered oxide material K2Ni2TeO6 using mainly the mu+SR technique. Our low-temperature mu+SR results together with complementary magnetic susceptibility measurements find an antiferromagnetic transition at T-N approximate to 27 K. Further mu+SR studies performed at higher temperatures reveal that potassium ions (K+) become mobile above 200 K and the activation energy for the diffusion process is obtained as E-a = 121(13) meV. This is the first time that K+ dynamics in potassium-based battery materials has been measured using mu+SR. Assisted by high-resolution neutron diffraction, the temperature dependence of the K-ion self diffusion constant is also extracted. Finally our results also reveal that K-ion diffusion occurs predominantly at the surface of the powder particles. This opens future possibilities for potentially improving ion diffusion as well as K-ion battery device performance using nano-structuring and surface coatings of the particles.
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| 7. |
- Nocerino, Elisabetta, et al.
(författare)
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Multiple unconventional charge density wave transitions in LaPt2Si2 superconductor clarified with high-energy X-ray diffraction
- 2023
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Ingår i: Communications Materials. - : Springer Nature. - 2662-4443. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- The quasi-2D platinum-based rare earth intermetallic LaPt2Si2 has attracted attention as it exhibits strong interplay between charge density wave order and superconductivity. However, most of the results reported on this material come from theoretical calculations, preliminary bulk investigations and powder samples, which makes it difficult to uniquely determine the temperature evolution of its crystal structure and, consequently, of its charge density wave transition. Therefore, the published literature around LaPt2Si2 is often controversial. Here, by means of high-resolution synchrotron X-ray diffraction data, we clarify some of the poorly or partially understood aspects of the physics of LaPt2Si2. In particular, we resolve the complex evolution of its crystal structure and superstructures, identifying the temperature dependence of multiple density wave transitions in good quality LaPt2Si2 single crystals. According to our findings, on cooling from room temperature LaPt2Si2 undergoes a series of subtle structural transitions which can be summarised as follows: second order commensurate tetragonal (P4/n m m)-to-incommensurate structure followed by a first order incommensurate-to-commensurate orthorhombic (P m m n) transition and then a first order commensurate orthorhombic (P m m n)-to-commensurate tetragonal (P4/n m m). The structural transitions are accompanied by both incommensurate and commensurate superstructural distortions of the lattice. The observed behavior is compatible with discommensuration of the CDW in this material.
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| 8. |
- Ohishi, Kazuki, et al.
(författare)
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The internal magnetic field in a ferromagnetic compound Y 2 Co 12 P 7
- 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 magnetic field in a ferromagnetic compound, Y2Co12P7 with T C = 150 K, was studied with μ +SR using a powder sample down to 2 K. The wTF-μ +SR measurements revealed the presence of a sharp magnetic transition at T C = 151 K, and the ZF-μ +SR measurements clarified the formation of static magnetic order below T C. The presence of two muon spin precession signals in the ZF-μ +SR spectrum below T C indicates the existence of the two different muon sites in the lattice. By considering the muon sites and local spin densities at the muon sites predicted with DFT calculations, the ordered magnetic moments of Co were successfully determined.
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| 9. |
- Ohishi, Kazuki, et al.
(författare)
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The internal magnetic field in a ferromagnetic compound Y2Co12P7
- 2023
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Ingår i: Proceedings 15th International Conference on Muon Spin Rotation, Relaxation and Resonance (SR). - : IOP Publishing. ; 2462
-
Konferensbidrag (refereegranskat)abstract
- The internal magnetic field in a ferromagnetic compound, Y2Co12P7 with T-C = 150 K, was studied with mu(+) SR using a powder sample down to 2 K. The wTF-mu(+) SR measurements revealed the presence of a sharp magnetic transition at T-C = 151 K, and the ZF-mu(+) SR measurements clarified the formation of static magnetic order below T-C. The presence of two muon spin precession signals in the ZF-mu(+) SR spectrum below TC indicates the existence of the two different muon sites in the lattice. By considering the muon sites and local spin densities at the muon sites predicted with DFT calculations, the ordered magnetic moments of Co were successfully determined.
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| 10. |
- Papadopoulos, Andreas, et al.
(författare)
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Circulating Interleukin-6 Levels and Incident Ischemic Stroke : A Systematic Review and Meta-analysis of Prospective Studies
- 2022
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Ingår i: Neurology. - 1526-632X. ; 98:10, s. 1002-1012
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Forskningsöversikt (refereegranskat)abstract
- BACKGROUND AND OBJECTIVES: Human genetic studies support a key role of interleukin-6 (IL-6) in the pathogenesis of ischemic stroke. Still, there are only limited data from observational studies exploring circulating IL-6 levels as a risk factor for ischemic stroke. Here, we set out to perform a systematic review and meta-analysis of aggregate data on cohort studies to determine the magnitude and shape of the association between circulating IL-6 levels and risk of incident ischemic stroke in the general population.METHODS: Following the PRISMA guidelines, we systematically screened the PubMed search engine from inception to March 2021 for population-based prospective cohort studies exploring the association between circulating IL-6 levels and risk of incident ischemic stroke. We pooled association estimates for ischemic stroke risk with random-effects models and explored non-linear effects in dose-response meta-analyses. Risk of bias was assessed with the Newcastle-Ottawa scale (NOS). We used funnel plots and trim-to-fill analyses to assess publication bias.RESULTS: We identified 11 studies (n=27,411 individuals; 2,669 stroke events) meeting our eligibility criteria. Mean age of all included participants was 60.5 years and 54.8% were females. Overall, quality of the included studies was high (median 8 out of 9 NOS points, interquartile range 7 to 9). In meta-analyses, 1-standard deviation increment in circulating log-transformed IL-6 levels was associated with a 19% increase in risk of incident ischemic stroke over a mean follow-up of 12.4 years (RR 1.19; 95% CI 1.10 to 1.28). A dose-response meta-analysis showed a linear association between circulating IL-6 levels and ischemic stroke risk. There was only moderate heterogeneity and the results were consistent in sensitivity analyses restricted to studies of low risk of bias and studies fully adjusting for demographic and vascular risk factors. The results also remained stable following adjustment for publication bias.DISCUSSION: Higher circulating IL-6 levels in community-dwelling individuals are associated with higher long-term risk of incident ischemic stroke in a linear pattern and independently of conventional vascular risk factors. Along with findings from genetic studies and clinical trials, these results provide additional support for a key role of IL-6 signaling in ischemic stroke.
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| 11. |
- Papadopoulos, Konstantinos, 1989
(författare)
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At the heart of Quantum Materials: Magnetism as a means and an end from a muon perspective
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Functional materials are at the center of solid state physics research and technological innovation in our era. In order to create (semi)autonomous, high precision and lightning-fast devices it is necessary to explore, modify and control the intrinsic properties of matter. This thesis focuses on quantum materials with strongly correlated physical entities, where properties may also be defined by geometry and can not thoroughly be described by classical physics. The magnetic and electrical properties of these materials are predominantly studied at an atomic level in order to understand the evolution of interactions between electron spins, charges and structure as well as dependencies from external parameters. Magnetic interactions are considered not only in the research subjects of this thesis but also in the employed experimental technique. Therefore, Chapter 2 is dedicated to a brief introduction in certain aspects of magnetism. Positive muon spin rotation, relaxation and resonance (μ+SR) is the principal experimental technique used in the presented studies. In essence this technique employs elementary particles called muons as magnetic probes in the studied samples. The reaction of muons to the local magnetic fields, which arise from the electronic structure or the atomic nuclei of solids, conveys direct or indirect information of phase transitions, dynamics or specific processes in the materials. In Chapters 3 and 4 the background and practicalities of the μ+SR technique will be elaborated to a sufficient extend that covers the scope of this thesis. The presented research encompasses a diverse array of materials with distinct structural characteristics and magnetic or electronic properties, which have been investigated utilizing μ+SR and complementary experimental techniques. A detailed introduction to each material and a summary of the experimental results can be found in Chapter 5. Concerning magnetic materials, the studies comprised LaSr1−xCaxNiReO6 and CrCl3 polycrystalline samples, as well as CoFeB/Ru/Pt superstructures. In the case of the double perovskite, three-dimensional magnet LaSr1−xCaxNiReO6, a dense and dilute magnetic phase were discovered above the critical temperature of magnetic order. The difference in size between the Sr and Ca cations alters the magnetic interaction between Ni and Re sub-lattices and as a result, the magnetically ordered phase. The magnetic phase diagram of the layered, two-dimensional magnet CrCl3 was similarly studied. The μ+SR analysis identified a dynamic layered antiferromagnetic ordering phase followed by a short range ordered ferromagnetic phase. Both studies exemplify the substantial advantage of measurements in zero external magnetic field with μ+SR. An alternative configuration with low energy μ+SR and adjustable muon implantation depth was employed to study the magnetic phases of multilayered CoFeB/Ru/Pt superstructures. A magnetic-skyrmion phase was identified and the persisting dynamics down to 50 K were studied in relation to an unexpected weak dependence on externally applied magnetic fields. Regarding ionic motion in non-magnets, a customized muon study was conducted on hybrid, organic-inorganic perovskite (CH3NH3)PbX3 (X=Br, Cl) single crystals, which constitute promising photovoltaic materials. Molecular fluctuations were studied across the structural phases of the materials with and without illumination. μ+SR results in these two environments indicate that molecular fluctuations and the type of halide ion are defining parameters on structural stability and carrier lifetimes, both of which are essential in solar cell applications.
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| 12. |
- Papadopoulos, Konstantinos, 1989
(författare)
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Correlation effects in ionic perovskite crystals
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Perovskites are a large family of versatile materials with favourable properties for spintronics and optoelectronics applications. The mineral CaTiO3 defines the archetypal crystal structure of perovskite materials with a general composition ABX3. The structure is ideally cubic, where the largest A cation is found in the centre, a smaller B cation occupies the edge sites and X anions form an octahedron around each B. Various electric and magnetic properties are observed depending on the electronic configurations, the exchange interactions and the crystal geometry formed by substitution of chemical elements or molecules. Our studies concern two classes of perovskite materials, the double perovskite, transition metal oxides LaSr1-xCaxNiReO6 for x = 0, 1 and the hybrid organometallic perovskite halides (CH3NH3)PbX3 for X = Br, Cl. We have mainly studied these compounds with muon spectroscopy (μ+SR), using muons as a magnetic probe to map the form and evolution of intrinsic electronic and nuclear magnetic fields. The rhenium-based perovskites points of interest are high magnetic transition temperatures along with a variety of metallic or insulating behaviors. In the case of LaSr1-xCaxNiReO6 , x = 0, 1 we expect the substitution of Sr with Ca to alter the type of exchange interaction between the Ni and Re cations. This incentive drove us to investigate the formation and evolution of magnetic ordering as a function of temperature in both compounds. The hybrid perovskites (CH3NH3)PbX3 , X = Br, Cl belong to the increasingly researched family of organometallic perovskite solar cell materials with long carrier diffusion lengths and a straightforward implementation into devices. However, intrinsic and extrinsic stability issues hinder the progress of application of these compounds. We aimed to indirectly identify intrinsic stability factors in the kinetics of the CH3NH3 molecule and the halide Br, Cl ion diffusion through their effect on the nuclear magnetic field distribution and dynamics.
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| 13. |
- Papadopoulos, Konstantinos I., et al.
(författare)
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Autoimmunity in sarcoidosis : the tip of the Iceberg
- 2023
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Ingår i: Clinical and Experimental Medicine. - : Springer Science and Business Media LLC. - 1591-8890 .- 1591-9528. ; 23, s. 951-953
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Tidskriftsartikel (refereegranskat)abstract
- Sarcoidosis is a mysterious condition with an etiology that has to date eluded explanation. Innumerable clinical and serological organ- and non-organ-specific autoimmune associations have been reported. Many of the associated conditions are life-threatening but easily manageable if diagnosed early. Due to the long latency that precedes the clinical onset of autoimmune diseases, it is prudent to ensure a long follow-up and a broad viewing perspective while maintaining a high index of suspicion when viewing the autoimmunity iceberg in sarcoidosis.
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| 14. |
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| 15. |
- Papadopoulos, Konstantinos, 1989, et al.
(författare)
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Influence of the magnetic sublattices in the double perovskite LaCaNiReO6
- 2022
-
Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9969 .- 2469-9950. ; 106:21
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetism of double perovskites is a complex phenomenon, determined from intra- or interatomic magnetic moment interactions, and strongly influenced by geometry. We take advantage of the complementary length and timescales of the muon spin rotation, relaxation, and resonance (μ+SR) microscopic technique and bulk ac/dc magnetic susceptibility measurements to study the magnetic phases of the LaCaNiReO6 double perovskite. As a result, we are able to discern and report ferrimagnetic ordering below TC=102K and the formation of different magnetic domains above TC. Between TC270K. An evolution of the interaction between Ni and Re magnetic sublattices, in this geometrically frustrated fcc perovskite structure, is revealed as a function of temperature through the critical behavior and thermal evolution of microscopic and macroscopic physical quantities.
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| 16. |
- Skendros, Panagiotis, et al.
(författare)
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Complement C3 inhibition in severe COVID-19 using compstatin AMY-101
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:33
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Tidskriftsartikel (refereegranskat)abstract
- Complement C3 activation contributes to COVID-19 pathology, and C3 targeting has emerged as a promising therapeutic strategy. We provide interim data from ITHACA, the first randomized trial evaluating a C3 inhibitor, AMY-101, in severe COVID-19 (PaO2/FiO2 <= 300 mmHg). Patients received AMY-101 (n = 16) or placebo (n = 15) in addition to standard of care. AMY-101 was safe and well tolerated. Compared to placebo (8 of 15, 53.3%), a higher, albeit nonsignificant, proportion of AMY-101-treated patients (13 of 16, 81.3%) were free of supplemental oxygen at day 14. Three nonresponders and two placebo-treated patients succumbed to disease-related complications. AMY-101 significantly reduced CRP and ferritin and restrained thrombin and NET generation. Complete and sustained C3 inhibition was observed in all responders. Residual C3 activity in the three nonresponders suggested the presence of a convertase-independent C3 activation pathway overriding the drug's inhibitory activity. These findings support the design of larger trials exploring the potential of C3-based inhibition in COVID-19 or other complement-mediated diseases.
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| 17. |
- 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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| 18. |
- Urushihara, Daisuke, et al.
(författare)
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Structural Transition with a Sharp Change in the Electrical Resistivity and Spin-Orbit Mott Insulating State in a Rhenium Oxide, Sr 3 Re 2 O 9
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:2, s. 507-514
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Tidskriftsartikel (refereegranskat)abstract
- We report the successful synthesis, crystal structure, and electrical properties of Sr3Re2O9, which contains Re6+ with the 5d1 configuration. This compound is isostructural with Ba3Re2O9 and shows a first-order structural phase transition at ∼370 K. The low-temperature (LT) phase crystallizes in a hettotype structure of Ba3Re2O9, which is different from that of the LT phase of Sr3W2O9, suggesting that the electronic state of Re6+ plays an important role in determining the crystal structure of the LT phase. The structural transition is accompanied by a sharp change in the electrical resistivity. This is likely a metal-insulator transition, as suggested by the electronic band calculation and magnetic susceptibility. In the LT phase, the ReO6 octahedra are rotated in a pseudo-a0a0a+ manner in Glazer notation, which corresponds to C-type orbital ordering. Paramagnetic dipole moments were confirmed to exist in the LT phase by muon spin rotation and relaxation measurements. However, the dipole moments shrink greatly because of the strong spin-orbit coupling in the Re ions. Thus, the electronic state of the LT phase corresponds to a Mott insulating state with strong spin-orbit interactions at the Re sites.
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| 19. |
- Urushihara, Daisuke, et al.
(författare)
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Structural Transition with a Sharp Change in the Electrical Resistivity and Spin-Orbit Mott Insulating State in a Rhenium Oxide, Sr3Re2O9
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:2, s. 508-515
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Tidskriftsartikel (refereegranskat)abstract
- We report the successful synthesis, crystal structure, and electrical properties of Sr3Re2O9, which contains Re6+ with the 5d(1) configuration. This compound is isostructural with Ba3Re2O9 and shows a first-order structural phase transition at similar to 370 K. The low-temperature (LT) phase crystallizes in a hettotype structure of Ba3Re2O9, which is different from that of the LT phase of Sr3W2O9, suggesting that the electronic state of Re6+ plays an important role in determining the crystal structure of the LT phase. The structural transition is accompanied by a sharp change in the electrical resistivity. This is likely a metal-insulator transition, as suggested by the electronic band calculation and magnetic susceptibility. In the LT phase, the ReO6 octahedra are rotated in a pseudo-a(0)a(0)a(+) manner in Glazer notation, which corresponds to C-type orbital ordering. Paramagnetic dipole moments were confirmed to exist in the LT phase by muon spin rotation and relaxation measurements. However, the dipole moments shrink greatly because of the strong spin-orbit coupling in the Re ions. Thus, the electronic state of the LT phase corresponds to a Mott insulating state with strong spin-orbit interactions at the Re sites.
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