Enhanced iron magnetic moment in the ThFe11C2 intermetallic compound

International audienceDetailed theoretical investigations on the electronic and magnetic properties of the ThFe11C2 compound have been performed using both the linear muffin-tin orbital and Korringa-Kohn-Rostocker methods of band structure calculation. The structure of the ThFe11C2 compound has three inequivalent iron sites with different local environment. A strongly enhanced magnetic moment is observed on certain Fe positions, coexisting with much lower magnetic moments on other iron positions of the lattice. Band structure calculations indeed show that the Fe magnetic moments depend strongly on the local environment. The average Fe magnetic moment obtained from these calculations is in good agreement with the experimental average Fe moment obtained from magnetization measurements. The orbital contribution to the magnetic moment is found to be especially large on the Fe 4b position. Comparing calculated hyperfine fields with experimental results, it is found that the calculated and experimental hyperfine fields are correlated. However, similarly to the results reported before for elemental Fe, the magnitude of all calculated Fe hyperfine fields is about 25% smaller. The agreement with the Mössbauer measurements is improved by scaling the core polarization contribution and by estimating the orbital valence d-electrons contribution to the magnetic hyperfine fields using the local spin density approximation + dynamical mean field theory calculated orbital moments

Magnetic anisotropy of deposited transition metal clusters

We present results of magnetic torque calculations using the fully relativistic spin-polarized Korringa-Kohn-Rostoker approach applied to small Co and Fe clusters deposited on the Pt(111) surface. From the magnetic torque one can derive amongst others the magnetic anisotropy energy (MAE). It was found that this approach is numerically much more stable and also computationally less demanding than using the magnetic force theorem that allows to calculate the MAE directly. Although structural relaxation effects were not included our results correspond reasonably well to recent experimental data

Electron-electron interaction strength in ferromagnetic nickel determined by spin-polarized positron annihilation

The two-photon momentum distribution of annihilating electron-positron pairs in ferromagnetic nickel (Ni) was determined by measuring the spin-polarized two-dimensional angular correlation of annihilation radiation (ACAR). The spectra were compared with theoretical results obtained within LDA+DMFT, a combination of the local density approximation (LDA) and the many-body dynamical mean-field theory (DMFT). The self-energy describing the electronic correlations in Ni is found to make important anisotropic contributions to the momentum distribution which are not present in LDA. Based on a detailed comparison of the theoretical and experimental results the strength of the local electronic interaction U in ferromagnetic Ni is determined as 2.0 +- 0.1 eV

Electronic structure of β\beta-SiAlON: effect of varying Al/O concentration at finite temperatures relevant for thermal quenchin

$\beta$-Si$_{6-z}$Al$_{z}$O$_{z}$N$_{8-z}$ is a prominent example of systems suitable as hosts for creating materials for light-emitting diodes. In this work, the electronic structure of a series of ordered and disordered $\beta$-Si$_{6-z}$Al$_{z}$O$_{z}$N$_{8-z}$ systems is investigated by means of ab initio calculations, using the FLAPW and the Green function KKR methods. Finite temperature effects are included within the alloy analogy model. We found that the trends with the Al/O doping are similar for ordered and disordered structures. The electronic band gap decreases with increasing $z$ by about 1 eV when going from $z$=0 to $z$=2. The optical gap decreases analogously as the electronic band gap. The changes in the density of states (DOS) at Si and N atoms introduced by doping $\beta$-Si$_{3}$N$_{4}$ with Al and O are comparable to the DOS at Al and O atoms themselves. The bottom of the conduction band in $\beta$-Si$_{6-z}$Al$_{z}$O$_{z}$N$_{8-z}$ is formed by extended states residing on all atomic types. Increasing the temperature leads to a shift of the bottom of the conduction band to lower energies. The amount of this shift increases with increasing doping $z$.Comment: 11 pages, 11 figures, 1 tabl

Poor outcome in hypoxic endometrial carcinoma is related to vascular density

Background Identification of endometrial carcinoma (EC) patients at high risk of recurrence is lacking. In this study, the prognostic role of hypoxia and angiogenesis was investigated in EC patients. Methods Tumour slides from EC patients were stained by immunofluorescence for carbonic anhydrase IX (CAIX) as hypoxic marker and CD34 for assessment of microvessel density (MVD). CAIX expression was determined in epithelial tumour cells, with a cut-off of 1%. MVD was assessed according to the Weidner method. Correlations with disease-specific survival (DSS), disease-free survival (DFS) and distant disease-free survival (DDFS) were calculated using Kaplan–Meier curves and Cox regression analysis. Results Sixty-three (16.4%) of 385 ECs showed positive CAIX expression with high vascular density. These ECs had a reduced DSS compared to tumours with either hypoxia or high vascular density (log-rank p = 0.002). Multivariable analysis showed that hypoxic tumours with high vascular density had a reduced DSS (hazard ratio [HR] 3.71, p = 0.002), DDFS (HR 2.68, p = 0.009) and a trend for reduced DFS (HR 1.87, p = 0.054). Conclusions This study has shown that adverse outcome in hypoxic ECs is seen in the presence of high vascular density, suggesting an important role of angiogenesis in the metastatic process of hypoxic EC. Differential adjuvant treatment might be indicated for these patients.publishedVersio

Band structure of CuMnAs probed by optical and photoemission spectroscopy

5 pages, 5 figures + Supplementary InformationTetragonal phase of CuMnAs progressively appears as one of the key materials for antiferromagnetic spintronics due to efficient current-induced spin-orbit torques whose existence can be directly inferred from crystal symmetry. Theoretical understanding of spintronic phenomena in this material, however, relies on the detailed knowledge of electronic structure (band structure and corresponding wave functions) which has so far been tested only to a limited extent. We show that AC permittivity (obtained from ellipsometry) and UV photoelectron spectra agree with density functional calculations. Together with the x-ray diffraction and precession electron diffraction tomography, our analysis confirms recent theoretical claim [Phys.Rev.B 96, 094406 (2017)] that copper atoms occupy lattice positions in the basal plane of the tetragonal unit cell.We acknowledge support from National Grid Infrastructure MetaCentrum provided under the programme “Projects of Large Research, Development, and Innovations Infrastructures” (CESNET LM2015042); Grant Agency of the Czech Republic under Grant No. 15-13436S; CEDAMNF (CZ.02.1.01/0.0/0.0/15_003/0000358) of the Czech ministry of education (MŠMT) as well as its LM2015087 and LNSMLNSpin grants; Cariplo Foundation, Grant No. 2013-0726 (MAGISTER); Spanish MINECO under MAT2015-67593-P project and the ‘Severo Ochoa’ Programme (SEV-2015-0496); EU FET Open RIA Grant No. 766566; Engineering and Physical Sciences Research Council Grant No. EP/P019749/1. P.W. acknowledges support from the Royal Society through a University Research Fellowship.Peer reviewe

Monogenic variants in dystonia: an exome-wide sequencing study

Background Dystonia is a clinically and genetically heterogeneous condition that occurs in isolation (isolated dystonia), in combination with other movement disorders (combined dystonia), or in the context of multisymptomatic phenotypes (isolated or combined dystonia with other neurological involvement). However, our understanding of its aetiology is still incomplete. We aimed to elucidate the monogenic causes for the major clinical categories of dystonia. Methods For this exome-wide sequencing study, study participants were identified at 33 movement-disorder and neuropaediatric specialty centres in Austria, Czech Republic, France, Germany, Poland, Slovakia, and Switzerland. Each individual with dystonia was diagnosed in accordance with the dystonia consensus definition. Index cases were eligible for this study if they had no previous genetic diagnosis and no indication of an acquired cause of their illness. The second criterion was not applied to a subset of participants with a working clinical diagnosis of dystonic cerebral palsy. Genomic DNA was extracted from blood of participants and whole-exome sequenced. To find causative variants in known disorder-associated genes, all variants were filtered, and unreported variants were classified according to American College of Medical Genetics and Genomics guidelines. All considered variants were reviewed in expert round-table sessions to validate their clinical significance. Variants that survived filtering and interpretation procedures were defined as diagnostic variants. In the cases that went undiagnosed, candidate dystonia-causing genes were prioritised in a stepwise workflow. Findings We sequenced the exomes of 764 individuals with dystonia and 346 healthy parents who were recruited between June 1, 2015, and July 31, 2019. We identified causative or probable causative variants in 135 (19%) of 728 families, involving 78 distinct monogenic disorders. We observed a larger proportion of individuals with diagnostic variants in those with dystonia (either isolated or combined) with coexisting non-movement disorder-related neurological symptoms (100 [45%] of 222;excepting cases with evidence of perinatal brain injury) than in those with combined (19 [19%] of 98) or isolated (16 [4%] of 388) dystonia. Across all categories of dystonia, 104 (65%) of the 160 detected variants affected genes which are associated with neurodevelopmental disorders. We found diagnostic variants in 11 genes not previously linked to dystonia, and propose a predictive clinical score that could guide the implementation of exome sequencing in routine diagnostics. In cases without perinatal sentinel events, genomic alterations contributed substantively to the diagnosis of dystonic cerebral palsy. In 15 families, we delineated 12 candidate genes. These include IMPDH2, encoding a key purine biosynthetic enzyme, for which robust evidence existed for its involvement in a neurodevelopmental disorder with dystonia. We identified six variants in IMPDH2, collected from four independent cohorts, that were predicted to be deleterious de-novo variants and expected to result in deregulation of purine metabolism. Interpretation In this study, we have determined the role of monogenic variants across the range of dystonic disorders, providing guidance for the introduction of personalised care strategies and fostering follow-up pathophysiological explorations

Contribution of Carbon Concrete Construction to the Circular and Resource Economy

Fibre-reinforced composites are used in many industries. In the construction industry, for example, the building material carbon concrete is increasingly being used successfully. Although the demand for fibre-reinforced composites and fibre-reinforced plastics made of carbon fibres has risen continuously by approximately 11% per year over the last 10 years, there is currently still no coherent integration of fibre-containing waste into the corresponding material cycles. In addition, there are ever-increasing requirements for environmental and climate protection, which necessitate a transformation from linear waste management to a cycle-oriented recycling and resource management overall. Carbon concrete construction is already providing an important impetus for the construction industry. The use of reinforcement made of mat or grid-shaped and bar-shaped carbon fibres basically makes a significant contribution to the conservation of resources, and ultimately a reduction in CO2 emissions of up to 80% is possible. In connection with recyclability, it is demonstrated that with today’s common facilities, both the deconstruction and dismantling of components and structures made of carbon concrete and the collection and sorting of the demolition material using camera-based sorting with a grade purity of 98% are already possible. In addition, the article provides an outlook on the project WIRreFa|WIR! recyceln Fasern (We recycle fibres) and its approach to closing the material cycle of fibre composites