We use first-principle calculations to investigate the electronic structure of InSe and In2Se3. The interlayer binding energy is found to be in the same range as for other 2D systems, and the ...monolayers are found to be dynamically stable, which suggest the possibility to obtain them as isolated layers. The GW approximation including spin–orbit is used to obtain the bandgaps, which are in the range relevant for application in electronics. Also, it is shown that an electric field perpendicular to the layers can induce a semiconductor to metal transition in this family of compounds.
Abstract Objectives The study aimed to investigate early and long-term outcome of thoracic endovascular aortic repair (TEVAR) for acute complicated type B dissection. Design This was a retrospective, ...single-centre, consecutive case series. Materials and Methods During the period 1999–2009, TEVAR was carried out in 50 patients with non-traumatic acute complicated type B dissection, and in another 10 patients with acute complications, including rupture, end-organ ischaemia and acute dilatation during the primary hospitalisation, but >14 days after onset of symptoms. Thus, in total, 60 patients were included; 22 with a DeBakey type IIIa dissection and 38 with a type IIIb; median age was 67 years. Early (30-day) and long-term (5-year) survival, re-intervention rate and complications were recorded until 1 July 2010. Results Within 30 days, two (3%) deaths, one (2%) paraplegia and three (5%) strokes were observed. Five-year survival was 87% and freedom from re-intervention at 5 years was 65%. Conclusions In patients with acute complicated type B aortic dissection, TEVAR can be performed with excellent early and long-term survival, whereas morbidity and long-term durability must be further elucidated.
By means of first principles calculations, we investigate the nature of exchange coupling in ferromagnetic bcc Fe on a microscopic level. Analyzing the basic electronic structure reveals a drastic ...difference between the 3d orbitals of E_{g} and T_{2g} symmetries. The latter ones define the shape of the Fermi surface, while the former ones form weakly interacting impurity levels. We demonstrate that, as a result of this, in Fe the T_{2g} orbitals participate in exchange interactions, which are only weakly dependent on the configuration of the spin moments and thus can be classified as Heisenberg-like. These couplings are shown to be driven by Fermi surface nesting. In contrast, for the E_{g} states, the Heisenberg picture breaks down since the corresponding contribution to the exchange interactions is shown to strongly depend on the reference state they are extracted from. Our analysis of the nearest-neighbor coupling indicates that the interactions among E_{g} states are mainly proportional to the corresponding hopping integral and thus can be attributed to be of double-exchange origin. By making a comparison to other magnetic transition metals, we put the results of bcc Fe into context and argue that iron has a unique behavior when it comes to magnetic exchange interactions.
Progress in materials science depends on the ability to discover new materials and to obtain and understand their properties. This has recently become particularly apparent for compounds with reduced ...dimensionality, which often display unexpected physical and chemical properties, making them very attractive for applications in electronics, graphene being so far the most noteworthy example. Here, we report some previously unknown two-dimensional materials and their electronic structure by data mining among crystal structures listed in the International Crystallographic Structural Database, combined with density-functional-theory calculations. As a result, we propose to explore the synthesis of a large group of two-dimensional materials, with properties suggestive of applications in nanoscale devices, and anticipate further studies of electronic and magnetic phenomena in low-dimensional systems.
We present a method for performing atomistic spin dynamic simulations. A comprehensive summary of all pertinent details for performing the simulations such as equations of motions, models for ...including temperature, methods of extracting data and numerical schemes for performing the simulations is given. The method can be applied in a first-principles mode, where all interatomic exchange is calculated self-consistently, or it can be applied with frozen parameters estimated from experiments or calculated for a fixed spin-configuration. Areas of potential application to different magnetic questions are also discussed. The method is finally applied to one situation where the macrospin model breaks down; magnetic switching in ultra strong magnetic fields.
Abstract We report on the stabilization of ferromagnetic skyrmions in zero external magnetic fields, in exchange-biased systems composed of ferromagnetic–antiferromagnetic (FM-AFM) bilayers. By ...performing atomistic spin dynamics simulations, we study cases of compensated, uncompensated, and partly uncompensated FM-AFM interfaces, and investigate the impact of important parameters such as temperature, inter-plane exchange interaction, Dzyaloshinskii–Moriya interaction, and magnetic anisotropy on the skyrmions appearance and stability. The model with an uncompensated FM-AFM interface leads to the stabilization of individual skyrmions and skyrmion lattices in the FM layer, caused by the effective field from the AFM instead of an external magnetic field. Similarly, in the case of a fully compensated FM-AFM interface, we show that FM skyrmions can be stabilized. We also demonstrate that accounting for interface roughness leads to stabilization of skyrmions both in compensated and uncompensated interface. Moreover, in bilayers with a rough interface, skyrmions in the FM layer are observed for a wide range of exchange interaction values through the FM-AFM interface, and the chirality of the skyrmions depends critically on the exchange interaction.
By means of first-principles GW calculations, we have studied the electronic structure properties of MX sub(2) (M = Mo, W; X = S, Se, Te) bilayers, including hybrid structures of MX sub(2) building ...blocks. The effect of spin-orbit coupling on the electronic structure and the effect of van der Waals interaction on the geometry were taken into account. All the homogeneous bilayers are identified as indirect band-gap materials, with an increase of the band gap when Mo is changed to W, and a decrease of the band gap when the atomic number of is increased. The same behavior is also observed for hybrid bilayers with common chalcogen atoms, while bilayers with common metal atoms have a direct band gap. Finally, it is shown that due to their particular band alignment, some heterobilayers enable electron-hole separation, which is of interest for solar cell applications.
Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We ...find that the first three borides of this series are stable phases, while AlCo2B2 and AlNi2B2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2 are more brittle, while AlCo2B2 and AlNi2B2 are more ductile. We propose that the elasticity of AlFe2B2 can be improved by alloying it with cobalt or nickel, or a combination of them. We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono- and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.
The coexistence of charge density wave (CDW) and superconductivity in tantalum disulfide (2H−TaS2) at low temperature is boosted by applying hydrostatic pressures to study both vibrational and ...magnetic transport properties. Around Pc, we observe a superconducting dome with a maximum superconducting transition temperature Tc=9.1 K. First-principles calculations of the electronic structure predict that, under ambient conditions, the undistorted structure is characterized by a phonon instability at finite momentum close to the experimental CDW wave vector. Upon compression, this instability is found to disappear, indicating the suppression of CDW order. The calculations reveal an electronic topological transition (ETT), which occurs before the suppression of the phonon instability, suggesting that the ETT alone is not directly causing the structural change in the system. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods. While a d wave and single-gap BCS prediction cannot describe the lower critical field Hc1 data, the temperature dependence of the Hc1 can be well described by a single-gap anisotropic s-wave order parameter.
Abstract
Background
The Swedish Quality Register for Ear Surgery (SwedEar) is a national register monitoring surgical procedures and outcomes of ear surgery to facilitate quality improvement. The ...value of the register is dependent on the quality of its data. SwedEar has never been validated regarding data quality or missing entries. Therefor, the purpose of this study was to assess coverage, completeness and response rate in the register and validate the physicians’ reported data accuracy.
Methods
In this validation study, the completeness, response rate and missing registrations were analysed. Data in SwedEar were compared with the yearly collected statistics of otosurgical procedures in The Swedish Otosurgical Society and the comparison of rates between groups was calculated with Fisher’s exact test. Validation of registered data accuracy was performed on every 20
th
registered case during a five-year period. Data were reabstracted from medical records and compared with the original registration. Interrater agreement, reliability measures, Cohen’s kappa, Gwet’s AC1 and positive predictive value were calculated.
Results
SwedEar has a coverage of 100%. The completeness of registered cases was 84% and the response rate was 74%. The validation of data accuracy assessed 13 530 variables, including audiograms. Less than 3% of incorrect or missing variables were identified. For most of the pre- and postoperative variables the Kappa and Gwet´s AC1 results show an almost perfect agreement (> 0.80). For audiogram data the ICC shows an excellent reliability (> 0.9) for all but one value.
Conclusion
This validation shows that SwedEar has excellent coverage, high completeness, and that the data in the register have almost perfect reliability. The data are suitable for both clinical and research purposes. Further efforts to improve completeness are warranted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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