| 1. |
|
|
| 2. |
|
|
| 3. |
- Adam, A, et al.
(författare)
-
Abstracts from Hydrocephalus 2016.
- 2017
-
Ingår i: Fluids and Barriers of the CNS. - : Springer Science and Business Media LLC. - 2045-8118. ; 14:Suppl 1
-
Tidskriftsartikel (refereegranskat)
|
|
| 4. |
|
|
| 5. |
- Bernien, M., et al.
(författare)
-
Tailoring the Nature of Magnetic Coupling of Fe-Porphyrin Molecules to Ferromagnetic Substrates
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:4, s. 047202-
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that an antiferromagnetic coupling between paramagnetic Fe-porphyrin molecules and ultrathin Co and Ni magnetic films on Cu(100) substrates can be established by an intermediate layer of atomic oxygen. The coupling energies have been determined from the temperature dependence of x-ray magnetic circular dichroism measurements. By density functional theory+U calculations the coupling mechanism is shown to be superexchange between the Fe center of the molecules and Co surface-atoms, mediated by oxygen.
|
|
| 6. |
- Bezerra-Neto, Manoel M., et al.
(författare)
-
Complex magnetic structure of clusters and chains of Ni and Fe on Pt(111)
- 2013
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3, s. 3054-
-
Tidskriftsartikel (refereegranskat)abstract
- We present an approach to control the magnetic structure of adatoms adsorbed on a substrate having a high magnetic susceptibility. Using finite Ni-Pt and Fe-Pt nanowires and nanostructures on Pt(111) surfaces, our ab initio results show that it is possible to tune the exchange interaction and magnetic configuration of magnetic adatoms (Fe or Ni) by introducing different numbers of Pt atoms to link them, or by including edge effects. The exchange interaction between Ni (or Fe) adatoms on Pt(111) can be considerably increased by introducing Pt chains to link them. The magnetic ordering can be regulated allowing for ferromagnetic or antiferromagnetic configurations. Noncollinear magnetic alignments can also be stabilized by changing the number of Pt-mediated atoms. An Fe-Pt triangularly-shaped nanostructure adsorbed on Pt(111) shows the most complex magnetic structure of the systems considered here: a spin-spiral type of magnetic order that changes its propagation direction at the triangle vertices.
|
|
| 7. |
- Bois, G., et al.
(författare)
-
Benchmark DEBORA : Assessment of MCFD compared to high-pressure boiling pipe flow measurements
- 2024
-
Ingår i: International Journal of Multiphase Flow. - : Elsevier BV. - 0301-9322 .- 1879-3533. ; 179
-
Tidskriftsartikel (refereegranskat)abstract
- A benchmark activity on two-fluid simulations of high-pressure boiling upward flows in a pipe is performed by 12 participants using different MCFD (Multiphase Computational Fluid Dynamics) codes and closure relationships. More than 30 conditions from DEBORA experiment conducted by CEA are considered. Each case is characterised by the flow rate, inlet temperature, wall heat flux and outlet pressure. High-pressure Freon (R12) at 14 bar and 26 bar is boiled in a 19.2mm pipe heated over 3.5m. Flow rates range from 2000 kg m−2 s−1 to 5000 kg m−2 s−1 and exit quality x ranges from single-phase conditions to x=0.1 which leads to a peak void fraction of α=70%. In these high pressure conditions, bubbles remain small and there is no departure from the bubbly flow regime (François et al., 2011; Hösler, 1968). However, different kind of bubbly flows are observed: wall-peak, intermediate peak or core-peak, depending on the case considered. Measurements along the pipe radius near the end of the heated section are compared to code predictions. They include void fraction, bubble mean diameter, vapour velocity and liquid temperature. The benchmark covered two phases. In the first phase of the benchmark activities, experimental data were given to the participants, allowing to compare the simulation results and to develop, to select or to adjust the models in the CMFD codes. The second phase included blind cases where the participants could not compare to the measurements. In between the two phases, possible additional model adjustments or calibrations were performed. Overall, the benchmark involved very different closures and a wide range of models’ complexity was covered. Yet, it is extremely difficult to have a robust closure for all conditions considered, even knowing experimental measurements. The wall-to-core peak transition is not captured consistently by the models. The degree of subcooling and the void fraction level are also difficult to assess. We were not capable of showing superiority of some physical closures, even for part of the model. The interaction between mechanisms and their hierarchy are extremely difficult to understand. Although departure from nucleate boiling (DNB) was not considered in this benchmarking exercise, it is expected that DNB predictions at high-pressure conditions depend strongly on the near-wall flow, temperature, and void fraction distributions. Therefore, the suitability of the closures also limits the accuracy of DNB predictions. The benchmark also demonstrated that in order to progress further in models development and validation, it is compulsory to have new measurements that include simultaneously as many variables as possible (including liquid temperature, velocity, cross-correlations and wall temperature); also, a better knowledge of the local bubble sizes distributions is the key to discriminate performances of interfacial area modelling (IATE, MUSIG or iMUSIG models, considering for instance the possibility of two classes of bubbles having totally different behaviour regarding the lift force). Following this benchmark impulse, we hope that future activities will be engaged on high-pressure boiling water experiments with a continuation of models’ comparisons and development.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Igarashi, R. N., et al.
(författare)
-
First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface
- 2012
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:1, s. 014436-
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of Mn nanostructures on the Fe(001) surface have been studied using the noncollinear first-principles real space-linear muffin-tin orbital-atomic sphere approximation method within density-functional theory. We have considered a variety of nanostructures such as adsorbed wires, pyramids, and flat and intermixed clusters of sizes varying from two to nine atoms. Our calculations of interatomic exchange interactions reveal the long-range nature of exchange interactions between Mn-Mn and Mn-Fe atoms. We have found that the strong dependence of these interactions on the local environment, the magnetic frustration, and the effect of spin-orbit coupling lead to the possibility of realizing complex noncollinear magnetic structures such as helical spin spiral and half-skyrmion.
|
|
| 11. |
|
|
| 12. |
- Lüder, J., et al.
(författare)
-
Electronic correlations revealed by hybrid functional and GW calculations in the anti-aromatic biphenylene molecule
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The biphenylene molecule is an interesting new candidate as a building block for advanced 2D materials. In this study, the molecular properties of biphenylene, like ionization potential and electron affinity, as well as the HOMO-LUMO gap were computed with the GW approach and with hybrid functional Density Functional Theory. B3LYP, HSE and HSE06 were compared as well as with the OT-RSH approach. The electronic structure of the valence states obtained by GW calculations and hybrid functionals was compared to experimental valence photoelectron spectroscopy data.
|
|
| 13. |
- Lüder, J., et al.
(författare)
-
Theory of X-ray spectroscopy of strongly correlated systems
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- X-ray absorption spectroscopy measured at the L-edge of transition metals (TMs) is a powerful element-selective tool providing direct information about the correlation effects in the 3d states. The theoretical modelling of the 2p to 3d excitation processes remains a challenge for contemporary ab initio electronic structure techniques, due to strong core-hole and multiplet effects influencing the spectra. In this work we present a realisation of the method combining the density functional theory with multiplet ligand field theory, proposed in Phys. Rev. B 85, 165113 (2012). The core of this approach is the solution of the single-impurity Anderson model (SIAM), parameterised from first principles.In our implementation, we adopt the dynamical mean-field theory and utilize the local Hamiltonian and the hybridisation function, projected onto TM 3d states, in order to construct the SIAM. We show that the current method can be used as an alternative to the construction of the Wannier functions. The developed computational scheme is applied to calculate the L-edge spectra for several TM monoxides. An excellent agreement between the theory and experiment is found for all studied systems. The possible extensions of the method as well as its limitations are discussed.
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Bidermane, Ieva, 1984-, et al.
(författare)
-
Atomic Contributions to the Valence Band Photoelectron Spectra of Metal-free, Iron and Manganese Phthalocyanines
- 2015
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 205, s. 92-97
-
Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- The present work reports a photoelectron spectroscopy study of the low-energy region of the valence band of metal-free phthalocyanine (H2Pc) compared with those of iron phthalocyanine (FePc) and manganese phthalocyanine (MnPc). We have analysed in detail the atomic orbital composition of the valence band both experimentally, by making use of the variation in photoionization cross-sections with photon energy, and theoretically, by means of density functional theory. The atomic character of the Highest Occupied Molecular Orbital (HOMO), reflected on the outermost valence band binding energy region, is different for MnPc as compared to the other two molecules. The peaks related to the C 2p contributions, result in the HOMO for H2Pc and FePc and in the HOMO-1 for MnPc as described by the theoretical predictions, in very good agreement with the experimental results. The DFT simulations, discerning the atomic contribution to the density of states, indicate how the central metal atom interacts with the C and N atoms of the molecule, giving rise to different partial and total density of states for these three Pc molecules.
|
|
| 19. |
- Björck, Matts, et al.
(författare)
-
Segregation and interdiffusion in (Fe,Co)/Pt superlattices
- 2009
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:8, s. 085428-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the chemical structure of (Fe,Co)/Pt superlattices, which recently have shown high uniaxial magnetocrystalline anisotropy combined with high saturation magnetic moments. In particular, the homogeneity of the (Fe,Co) alloy is studied with a combination of x-ray and neutron reflectometry-the latter in a configuration where magnetic scattering is negligible. It is deduced, with support from off-specular x-ray reflectivity patterns and corresponding simulations, that the lower (Fe,Co)-on-Pt interface contains more Co than the upper Pt-on-(Fe,Co) interface. This can occur as Co interdiffuses into Pt more easily than Fe, as shown by density-functional calculations. The effect of this interdiffusion and segregation on the uniaxial anisotropy is discussed, and it is found that the previously observed discrepancy between experimental and theoretical anisotropy values can be quantitatively accounted for.
|
|
| 20. |
- Boya, K., et al.
(författare)
-
Possible candidate for the realization of the floating phase in the S=5/2 frustrated spin-chain model : K3Fe(MoO4)2(Mo2O7 )
- 2024
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 109:15
-
Tidskriftsartikel (refereegranskat)abstract
- The frustrated spin-chain (FSC) systems exhibit exotic ground states and distinct quantum phase transitions. The ?=1/2 FSC is known to exhibit the Kosterlitz-Thouless transition from a commensurate gapless phase to a fully dimerized gapped phase upon the ratio of next-nearest-neighbor to nearest-neighbor coupling (?=?2/?1) being tuned. On the other hand, the ?=5/2 FSC system is known to show transitions from a commensurate gapless phase to partially dimerized and incommensurate floating phases [Chepiga, Affleck, and Mila, Phys. Rev. B 105, 174402 (2022)]. While a large region of the floating phase has been theoretically predicted for the ?=5/2 FSC model when ?>0.43, it is yet to be explored experimentally. Here, we have investigated a compound K3Fe(MoO4)2(Mo2O7), having well-separated ?=5/2 FSCs. The electronic structure calculations show that the ?=?2/?1 is close to 0.9, being similar to another FSC compound Bi3FeMo2O12 (?≈1.1). No magnetic long-range order is found down to 0.09 K, despite the relatively sizable Curie-Weiss temperature ???=−18K. The magnetic heat capacity shows the power-law behavior, indicating that the compound exhibits gapless excitations. Based on the experimental results and the theoretical calculations employed by density functional theory, we argue that the titled system is a possible candidate for exhibiting the floating phase.
|
|
| 21. |
- Brucas, R., et al.
(författare)
-
Magnetic anisotropy and evolution of ground-state domain structures in bcc Fe81Ni19/Co(001) superlattices
- 2008
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : The American Physical Society. - 1098-0121 .- 1550-235X. ; 78:2, s. 024421-
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic anisotropy and evolution of striped magnetic domain structures in bcc Fe81Ni19/Co(001) superlattices with the total thickness ranging from 85 to 1370 nm has been studied by magneto-optical Kerr effect and magnetic force microscopy. At a thickness of about 85 nm [25 bilayers (BL)] the domains appear as stripe domains, typical for perpendicular anisotropy films, with the weak cubic anisotropy of the in-plane magnetization component stabilizing the stripe direction. The magnetic domain period strongly depends on the thickness of the superlattice. As the thickness increases, the equilibrium magnetization orients at oblique angles with respect to the film plane and continuously varies with the thickness from in-plane to out-of-plane. We first apply a simple phenomenological model which correctly predicts the transition from in-plane to out-of-plane magnetization as well as increasing domain period and saturation field with increasing BL number. The results indicate the presence of partial flux-closure domains at the film surface with the tilt angle continuously varying with the superlattice thickness. By solving a linearized Landau–Lifshitz equation together with Maxwell’s equations in magnetostatic approximation for samples consisting of up to 1000 individual layers, we calculate the spin-wave dispersion and determine the stability conditions for the saturated ferromagnetic state. From these results the dependence of the saturation field on the number of layers is inferred and agrees well with the experiment. The uniaxial bulk anisotropy is attributed to distortions along the c axis and the results further show evidence for the presence of an easy-plane interface anisotropy in these samples.
|
|
| 22. |
- Chen, Chi-Hua, et al.
(författare)
-
Leveraging genome characteristics to improve gene discovery for putamen subcortical brain structure
- 2017
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Discovering genetic variants associated with human brain structures is an on-going effort. The ENIGMA consortium conducted genome-wide association studies (GWAS) with standard multi-study analytical methodology and identified several significant single nucleotide polymorphisms (SNPs). Here we employ a novel analytical approach that incorporates functional genome annotations (e.g., exon or 5′UTR), total linkage disequilibrium (LD) scores and heterozygosity to construct enrichment scores for improved identification of relevant SNPs. The method provides increased power to detect associated SNPs by estimating stratum-specific false discovery rate (FDR), where strata are classified according to enrichment scores. Applying this approach to the GWAS summary statistics of putamen volume in the ENIGMA cohort, a total of 15 independent significant SNPs were identified (conditional FDR < 0.05). In contrast, 4 SNPs were found based on standard GWAS analysis (P < 5 × 10−8). These 11 novel loci include GATAD2B, ASCC3, DSCAML1, and HELZ, which are previously implicated in various neural related phenotypes. The current findings demonstrate the boost in power with the annotation-informed FDR method, and provide insight into the genetic architecture of the putamen.
|
|
| 23. |
- Chimata, Raghuveer, et al.
(författare)
-
Magnetism and ultrafast magnetization dynamics of Co and CoMn alloys at finite temperature
- 2017
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 95:21
-
Tidskriftsartikel (refereegranskat)abstract
- Temperature-dependent magnetic experiments such as pump-probe measurements generated by a pulsed laser have become a crucial technique for switching the magnetization in the picosecond time scale. Apart from having practical implications on the magnetic storage technology, the research field of ultrafast magnetization poses also fundamental physical questions. To correctly describe the time evolution of the atomic magnetic moments under the influence of a temperature-dependent laser pulse, it remains crucial to know if the magnetic material under investigation has magnetic excitation spectrum that is more or less dependent on the magnetic configuration, e.g., as reflected by the temperature dependence of the exchange interactions. In this paper, we demonstrate from first-principles theory that the magnetic excitation spectra in Co in fcc, bcc, and hcp structures are nearly identical in a wide range of noncollinear magnetic configurations. This is a curious result of a balance between the size of the magnetic moments and the strength of the Heisenberg exchange interactions, that in themselves vary with configuration, but put together in an effective spin Hamiltonian results in a configuration-independent effective model. We have used such a Hamiltonian, together with ab initio calculated damping parameters, to investigate the magnon dispersion relationship as well as ultrafast magnetization dynamics of Co and Co-rich CoMn alloys.
|
|
| 24. |
- Coleman, V. A., et al.
(författare)
-
Defect Formation In Graphene Nanosheets By Acid Treatment : An X-Ray Absorption Spectroscopy And Density Functional Theory Study
- 2008
-
Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 41:6, s. 062001-4
-
Tidskriftsartikel (refereegranskat)abstract
- In-plane defects have been introduced into graphene nanosheets by treatment with hydrochloric acid. Acid treatment induces bond cleavage in the C–C network via electrophilic attack. These resultant vacancy sites will then undergo further reactions with the surrounding ambient to produce C–O and C–H bonds. A σ* resonance at 287 eV in the carbon K-edge x-ray absorption spectra is observed with acid treatment and is assigned to C–O states. Theoretical modelling of a di-vacancy in a graphene bilayer reproduces all essential features of this resonance and in addition predicts a metallic conductivity of states around this vacancy. The possibility of engineering the properties of graphene via the routes explored here is an important step towards establishing strategies for building devices based on this material.
|
|
| 25. |
|
|
| 26. |
- Ghosh, S., et al.
(författare)
-
Electronic structure and magnetism of disordered bcc Fe alloys
- 2001
-
Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 23:4, s. 455-461
-
Tidskriftsartikel (refereegranskat)abstract
- We study the electronic structure and magnetic properties of disordered bcc CoxFe1-x, CrxFe1-x and MnxFe1-x alloys in their ferromagnetic phases using the Augmented Space Recursion (ASR) technique coupled with the tight-binding linearized muffin tin orbital (TB-LMTO) method. We calculate the density of states and magnetic moment of these alloys to show the variation upon alloying Fe with the other neighbouring 3d transition metals using arguments based on charge transfer, exchange splitting and hybridization effects.
|
|
| 27. |
- Haferman, H., et al.
(författare)
-
Competing anisotropies in bcc Fe81Ni19/Co(001) superlattices
- 2009
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:7, s. 073102-073102-3
-
Tidskriftsartikel (refereegranskat)abstract
- Amagnetization reorientation transition has been observed in Fe81Ni19/Co(001) superlattices bymeans of magneto-optical Kerr effect and magnetic force microscopy measurements.The transition is driven by the variation of the interfacedensity. First-principles calculations are combined with a linear stability analysisof the Landau–Lifshitz equation to clarify the mechanism that drivesthe transition. We are able to identify it as beingdriven by competing interface in-plane and uniaxial bulk out-of-plane anisotropies.The origin of the bulk anisotropy is attributed to tetragonaldistortions experimentally observed in these superlattices.
|
|
| 28. |
- Herper, Heike C., et al.
(författare)
-
Iron porphyrin molecules on Cu(001) : Influence of adlayers and ligands on the magnetic properties
- 2013
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:17, s. 174425-
-
Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of Fe octaethylporphyrin molecules on Cu(001) have been investigated by means of density functional theory (DFT) methods and x-ray absorption spectroscopy. The molecules have been adsorbed on the bare metal surface and on an oxygen-covered surface, which shows a root 2 x 2 root 2R45 degrees reconstruction. In order to allow for a direct comparison between magnetic moments obtained from sum-rule analysis and DFT, we calculate the spin dipolar term 7T (theta), which is also important in view of the magnetic anisotropy of the molecule. The measured x-ray magnetic circular dichroism shows a strong dependence on the photon incidence angle, which we could relate to a huge value of 7T (theta), e. g., on Cu(001), 7T (theta) amounts to -2.07 mu(B) for normal incidence leading to a reduction of the effective spin moment (m(s) + 7T (theta)). Calculations have also been performed to study the influence of possible ligands such as Cl and O atoms on the magnetic properties of the molecule and the interaction between molecule and surface because the experimental spectra display a clear dependence on the ligand, which is used to stabilize the molecule in the gas phase. Both types of ligands weaken the hybridization between surface and porphyrin molecule and change the magnetic spin state of the molecule, but the changes in the x-ray absorption are clearly related to residual Cl ligands.
|
|
| 29. |
|
|
| 30. |
- Jafri, Hassan, et al.
(författare)
-
Control of Conductivity in Graphene by Formation of Defects
- 2008
-
Ingår i: AVS 55th International Symposium & Exhibition 2008, October 19-24, Boston, USA.
-
Konferensbidrag (refereegranskat)abstract
- Due to their large surface areas, the conductivity of graphene and carbonnano-sheets depends strongly on their chemical environment. This is thebase for future environmental sensors containing graphene sheets. Here, abinitiocalculations propose a possibility of conductivity increase. In theexperiment, a 1-2 orders of magnitude increase of the conductivity isobserved experimentally on sub-nanometTe carbon nano-sheets by using anin-situ nano-manipulation set-up. The conductivity of the graphene sheetswas assessed from first-principle simulations. Insertion of defects in thegraphene sheets can lead to a strong increase of the conductivity of singlegraphene sheets. To study this result experimentally, we carried outconductivity measurements on sub-nanometre graphene nano-sheets that aredeposited on W -substrates by radio-frequency plasma-enhanced chemicalvapour deposition. This deposition process creates free-standingmicrometer-sized carbon nano-sheets with sub-nanometre thickness. Thesenano-sheets were exposed to an acid treatment. It has been shown recentlythat such acid treatment creates defects in these sheets. Using a nanomanipulatorinside a scanning electron microscope, we individuallycontacted the nano-sheets and measured their resistance as a function oftheir functionalization. From more than 1000 measurements we obtain a 1-2order of magnitude increase of conductivity in the functionalised carbonnano-sheets as compared to just water treated or untreated carbon nanosheets.This result corresponds well to the conductivity change obtainedfrom theory. This study makes it possible to create environmental sensorsbased on graphene like carbon nano-sheets.
|
|
| 31. |
- Klar, D., et al.
(författare)
-
Oxygen-tuned magnetic coupling of Fe-phthalocyanine molecules to ferromagnetic Co films
- 2013
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 88:22, s. 224424-
-
Tidskriftsartikel (refereegranskat)abstract
- The coupling of submonolayer coverages of Fe-phthalocyanine molecules on bare and oxygen-covered ferromagnetic Co(001) films was studied by x-ray-absorption spectroscopy, especially the x-ray magnetic circular dichroism, in combination with density functional theory. We observe that the magnetic moments of the paramagnetic molecules are aligned even at room temperature, resulting from a magnetic coupling to the substrate. While the magnetization of the Fe ions directly adsorbed on the Co surface is parallel to the magnetization of the Co film, the introduction of an oxygen interlayer leads to an antiparallel alignment. As confirmed by theory, the coupling strength is larger for the system FePc/Co than for FePc/O/Co, causing a stronger temperature dependence of the Fe magnetization for the latter system. Furthermore, the calculations reveal that the coupling mechanism changes due to the O layer from mostly direct exchange to Co of the bare surface to a 180 degrees antiferromagnetic superexchange via the O atoms. Finally, by comparing the experimental x-ray-absorption spectra at the N K edge with the corresponding calculations, the contribution of the individual orbitals has been determined and the two inequivalent N atoms of the molecules could be distinguished.
|
|
| 32. |
- Kou, R. H., et al.
(författare)
-
Charge transfer-tuned magnetism in Nd-substituted Gd5Si4
- 2018
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 8:12
-
Tidskriftsartikel (refereegranskat)abstract
- We report a charge-transfer mechanism in tuning of magnetism of Nd-substituted Gd5-xNdxSi4 (x=1 and 2.5) compounds. The X-ray absorption near edge structure measurements demonstrated that Nd substitutions for Gd induce charge transfer of 5d electrons from Gd to Nd. The charge transfer weakens spin-orbital coupling of Gd but strengthens that of Nd. Consequently, the magnetization responses of the substituted compounds to low magnetic fields are increased while their saturation magnetization is reduced. Electronic structure calculations showed that the charge transfer stabilizes a ferromagnetic and a ferrimagnetic structure in the compounds with x = 1 and 2.5, respectively, but that it does not change the 5d-3p hybridization significantly. It is suggested that the charge transfer of 5d electrons may occur in other rare earth-substituted Gd5Si4 compounds allowing for tuning of their magnetism.
|
|
| 33. |
- Kovachev, Petar Stefanov, et al.
(författare)
-
RNA modulates aggregation of the recombinant mammalian prion protein by direct interaction
- 2019
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Recent studies have proposed that nucleic acids act as potential cofactors for protein aggregation and prionogenesis. By means of sedimentation, transmission electron microscopy, circular dichroism, static and dynamic light scattering, we have studied how RNA can influence the aggregation of the murine recombinant prion protein (rPrP). We find that RNA, independent of its sequence, source and size, modulates rPrP aggregation in a bimodal fashion, affecting both the extent and the rate of rPrP aggregation in a concentration dependent manner. Analogous to RNA-induced liquid-liquid phase transitions observed for other proteins implicated in neurodegenerative diseases, high protein to RNA ratios stimulate rPrP aggregation, while low ratios suppress it. However, the latter scenario also promotes formation of soluble oligomeric aggregates capable of seeding de novo rPrP aggregation. Furthermore, RNA co-aggregates with rPrP and thereby gains partial protection from RNase digestion. Our results also indicate that rPrP interacts with the RNAs with its N-terminus. In summary, this study elucidates the proposed adjuvant role of RNA in prion protein aggregation and propagation, and thus advocates an auxiliary role of the nucleic acids in protein aggregation in general.
|
|
| 34. |
- Lamichhane, S., et al.
(författare)
-
First-Principles Study of Adsorption of Halogen Molecules on Graphene-MoS2 Bilayer Hetero-system
- 2016
-
Ingår i: 24Th Condensed Matter Days National Conference (Cmdays2016). - : IOP Publishing.
-
Konferensbidrag (refereegranskat)abstract
- We have performed density functional theory based first-principles calculations to study the stability, geometrical structures and electronic properties of pure 3x3 supercell of MoS2, 4x4 supercell of graphene, graphene-MoS2 bilayer hetero-system, F-2, Cl-2, Br-2 and I-2 molecules on hetero-system within the DFT-D-2 level of approximations. The preferable site and adsorption energy of halogen molecules are studied. The most stable geometries are considered to study their electronic band structure, Density of states and magnetic properties with reference to individual 2D components, graphene and MoS2.
|
|
| 35. |
|
|
| 36. |
|
|
| 37. |
|
|
| 38. |
|
|
| 39. |
- Lo, Min-Tzu, et al.
(författare)
-
Genome-wide analyses for personality traits identify six genomic loci and show correlations with psychiatric disorders
- 2017
-
Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 49:1, s. 152-156
-
Tidskriftsartikel (refereegranskat)abstract
- Personality is influenced by genetic and environmental factors(1) and associated with mental health. However, the underlying genetic determinants are largely unknown. We identified six genetic loci, including five novel loci(2,3), significantly associated with personality traits in a meta-analysis of genome-wide association studies (N = 123,132-260,861). Of these genome-wide significant loci, extraversion was associated with variants in WSCD2 and near PCDH15, and neuroticism with variants on chromosome 8p23.1 and in L3MBTL2. We performed a principal component analysis to extract major dimensions underlying genetic variations among five personality traits and six psychiatric disorders (N = 5,422-18,759). The first genetic dimension separated personality traits and psychiatric disorders, except that neuroticism and openness to experience were clustered with the disorders. High genetic correlations were found between extraversion and attention-deficit- hyperactivity disorder (ADHD) and between openness and schizophrenia and bipolar disorder. The second genetic dimension was closely aligned with extraversion-introversion and grouped neuroticism with internalizing psychopathology (e.g., depression or anxiety).
|
|
| 40. |
- Lo, Min-Tzu, et al.
(författare)
-
Modeling prior information of common genetic variants improves gene discovery for neuroticism
- 2017
-
Ingår i: Human Molecular Genetics. - : OXFORD UNIV PRESS. - 0964-6906 .- 1460-2083. ; 26:22, s. 4530-4539
-
Tidskriftsartikel (refereegranskat)abstract
- Neuroticism reflects emotional instability, and is related to various mental and physical health issues. However, the majority of genetic variants associated with neuroticism remain unclear. Inconsistent genetic variants identified by different genome-wide association studies (GWAS) may be attributable to low statistical power. We proposed a novel framework to improve the power for gene discovery by incorporating prior information of single nucleotide polymorphisms (SNPs) and combining two relevant existing tools, relative enrichment score (RES) and conditional false discovery rate (FDR). Here, SNP's conditional FDR was estimated given its RES based on SNP prior information including linkage disequilibrium (LD)-weighted genic annotation scores, total LD scores and heterozygosity. A known significant locus in chromosome 8p was excluded before estimating FDR due to long-range LD structure. Only one significant LD-independent SNP was detected by analyses of unconditional FDR and traditional GWAS in the discovery sample (N = 59 225), and notably four additional SNPs by conditional FDR. Three of the five SNPs, all identified by conditional FDR, were replicated (P < 0.05) in an independent sample (N = 170 911). These three SNPs are located in intronic regions of CADM2, LINGO2 and EP300 which have been reported to be associated with autism, Parkinson's disease and schizophrenia, respectively. Our approach using a combination of RES and conditional FDR improved power of traditional GWAS for gene discovery providing a useful framework for the analysis of GWAS summary statistics by utilizing SNP prior information, and helping to elucidate the links between neuroticism and complex diseases from a genetic perspective.
|
|
| 41. |
- Lundasen, T, et al.
(författare)
-
PPARalpha is a key regulator of hepatic FGF21
- 2007
-
Ingår i: Biochemical and biophysical research communications. - : Elsevier BV. - 0006-291X. ; 360:2, s. 437-440
-
Tidskriftsartikel (refereegranskat)
|
|
| 42. |
- Mikkelsen, Anders, et al.
(författare)
-
Defect structure of Ga1-xMnxAs: A cross-sectional scanning tunneling microscopy study
- 2004
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:8
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the atomic scale structure of molecular beam epitaxy grown Ga1-xMnxAs compounds with various Mn concentrations by cross-sectional scanning tunneling microscopy and first principles calculations. Only bright protrusions close to the top layer As atoms are directly correlated with the bulk Mn concentration. Atomically resolved filled and empty states images of this defect are compared to images derived from first principles calculations. We identify the Mn related defect as substitutional Mn in the second layer Ga site. Surprisingly no substitutional Mn is observed in the top-most Ga layer. The experimental results are consistent with the energetics of our first principles total energy calculations.
|
|
| 43. |
- Papadakis, Raffaello, et al.
(författare)
-
Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene
- 2016
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S 0), becomes exergonic in the first triplet state (T 1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T 1 state and also in its first singlet excited state (S 1), opposite to S 0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T 1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T 1 and S 1 states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO 2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions. © The Author(s) 2016.
|
|
| 44. |
|
|
| 45. |
- Wessley, O, et al.
(författare)
-
Final state effects in the X-ray absorption spectra of La0.7Sr0.3MnO3
- 2004
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 272-276:3, s. 1780-1781
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comparison of theoretical calculations of the electronic structure of La0.7Sr0.3MnO3 with measurements of the unoccupied local density of states for Mn obtained from X-ray absorption spectroscopy (XAS). We compare two different theoretical calculations of the Mn XAS spectra, one based on the local spin density approximation (LSDA) and the other one based on an atomic Hartree–Fock calculation for the Mn ions. In the atomic calculation the solid state effects are introduced through a cubic crystal field where the crystal field strength is obtained from the LSDA calculation. It is found that the atomic calculations agree better with experimental data.
|
|
| 46. |
- Xu, D. B., et al.
(författare)
-
Large enhancement of magnetic moment in L1(0) ordered FePt thin films by Nd substitutional doping
- 2015
-
Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 48:25
-
Tidskriftsartikel (refereegranskat)abstract
- We studied L1(0) ordered Fe50Pt50-xNdx alloy films, which showed a large enhancement (similar to 18.4% at room temperature and similar to 11.7% at 10 K) of magnetic moment with 6 atomic % of Nd. Analysis of the x-ray magnetic circular dichroism spectra at the Fe L-3,L-2 edges and Nd M-5,M-4 edges in Fe50Pt44Nd6 films indicated a significant contribution of the Nd orbital moment. The origin of the large enhancement of magnetic moment was attributed to the effect of ferromagnetic coupling of the total magnetic moments between Fe and Nd. Density functional theory based first principles calculations supported the experimental observations of increasing moment due to Nd substitution of Pt.
|
|
| 47. |
- Zhu, Y., et al.
(författare)
-
Proteogenomics produces comprehensive and highly accurate protein-coding gene annotation in a complete genome assembly of Malassezia sympodialis
- 2017
-
Ingår i: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 45:5, s. 2629-2643
-
Tidskriftsartikel (refereegranskat)abstract
- Complete and accurate genome assembly and annotation is a crucial foundation for comparative and functional genomics. Despite this, few complete eukaryotic genomes are available, and genome annotation remains a major challenge. Here, we present a complete genome assembly of the skin commensal yeast Malassezia sympodialis and demonstrate how proteogenomics can substantially improve gene annotation. Through long-read DNA sequencing, we obtained a gap-free genome assembly for M. sympodialis (ATCC 42132), comprising eight nuclear and one mitochondrial chromosome. We also sequenced and assembled four M. sympodialis clinical isolates, and showed their value for understanding Malassezia reproduction by confirming four alternative allele combinations at the two mating-type loci. Importantly, we demonstrated how proteomics data could be readily integrated with transcriptomics data in standard annotation tools. This increased the number of annotated protein-coding genes by 14% (from 3612 to 4113), compared to using transcriptomics evidence alone. Manual curation further increased the number of protein-coding genes by 9% (to 4493). All of these genes have RNA-seq evidence and 87% were confirmed by proteomics. The M. sympodialis genome assembly and annotation presented here is at a quality yet achieved only for a few eukaryotic organisms, and constitutes an important reference for future host-microbe interaction studies.
|
|
