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We present a first-principles investigation of NdFe12 and NdFe12X (X = B, C, N, O, and F) crystals with the ThMn12 structure. Intersite magnetic couplings in these compounds, the so-called exchange couplings, are estimated by using Liechtenstein’s method. It is found that the Nd–Fe couplings are sensitive to the interstitial dopant X, with the Nd–Fe(8j) coupling in particular reduced significantly for X = N. This suggests that magnetocrystalline anisotropy decays quickly with rising temperature in the X = N system although nitrogenation has advantages over other dopants in terms of enhancing low-temperature magnetic properties. The Curie temperature is also calculated from the magnetic couplings by using the mean field approximation. Introduction of X enhances the Curie temperature, with both structural changes and chemical effects found to play important roles in this enhancement. [ABSTRACT FROM AUTHOR]

Recently synthesized NdFe12N has excellent magnetic properties, while it is thermodynamically unstable. Using the first-principles method, we study the effect of substitutional 3d transition metal elements to the mother compound NdFe12. We find that Co has a positive effect on the stability of the ThMn12 structure. In contrast to Ti substitution, Co substitution does not reduce the magnetization significantly. The crystal field parameter hr²iA20 is nearly unchanged by Co substitution, and nitrogenation to NdFe11Co greatly enhances hr²iA20. This suggests that Co is a good candidate as a substitutional element for NdFe12N. [ABSTRACT FROM AUTHOR]

We demonstrate that knowledge of chemical physics on a materials system can be automatically extracted from first-principles calculations using a data mining technique; this information can then be utilized to construct a simple empirical atomic potential model. By using unsupervised learning of the generative Gaussian mixture model, physically meaningful patterns of atomic local chemical environments can be detected automatically. Based on the obtained information regarding these atomic patterns, we propose a chemical-structure-dependent linear mixture model for estimating the atomic potential energy. Our experiments show that the proposed mixture model significantly improves the accuracy of the prediction of the potential energy surface for complex systems that possess a large diversity in their local structures. [ABSTRACT FROM AUTHOR]

A classical spin model derived ab initio for rare-earth-based permanent magnet compounds is presented. Our target compound, NdFe12N, is a material that goes beyond today's champion magnet compound Nd2Fe14B in its intrinsic magnetic properties with a simpler crystal structure. Calculated temperature dependence of the magnetization and the anisotropy field agrees with the latest experimental results in the leading order. Having put the realistic observables under our numerical control, we propose that engineering 5d-electron-mediated indirect exchange coupling between 4f-electrons in Nd and 3d-electrons from Fe would most critically help enhance the material's utility over the operation-temperature range. [ABSTRACT FROM AUTHOR]

Recent progress in understanding the electronic band topology and emergent topological properties encourage us to reconsider the band structure of well-known materials including elemental substances. Controlling such a band topology by external field is of particular interest from both fundamental and technological viewpoints. Here we report possible signatures of the pressure-induced topological phase transition from a semiconductor to a Weyl semimetal in elemental tellurium probed by transport measurements. Pressure variation of the periods of Shubnikov-de Haas oscillations, as well as oscillation phases, shows an anomaly around the pressure theoretically predicted for topological phase transition. This behavior is consistent with the pressure-induced band deformation and resultant band-crossing effect. Moreover, effective cyclotron mass is reduced toward the critical pressure, potentially reflecting the emergence of massless linear dispersion. The present result paves the way for studying the electronic band topology in well-known compounds and topological phase transition by the external field. [ABSTRACT FROM AUTHOR]

We analyze the Curie temperatures of rare-earth transition metal binary alloys using machine learning. In order to select important descriptors and descriptor groups, we introduce a newly developed subgroup relevance analysis and adopt hierarchical clustering in the representation. We execute exhaustive search and demonstrate that our approach results in the successful selection of important descriptors and descriptor groups. It helps us to choose the combination of descriptors and to understand the meaning of the selected combination of descriptors. [ABSTRACT FROM AUTHOR]

We present a first-principles study of RFe12-xCrx (R = Y, Nd, Sm) crystals with ThMn12 structure. We discuss, within the mean field approximation, intersite magnetic couplings calculated using Liechtenstein's formula and convert them into Curie temperatures, TC, which are found to become larger when a small amount of Cr (x ≤ 0.5) is introduced into the system. This enhancement is larger than that for Co in the dilute limit, x → 0. In contrast, above x > 0.5, the Curie temperature decreases as Cr concentration increases. This behavior is analyzed using an expansion of TC in terms of concentration. [ABSTRACT FROM AUTHOR]

Strong permanent magnets mainly consist of rare earths (R) and transition metals (T). The main phase of the neodymium magnet, which is the strongest magnet, is Nd2Fe14B. Sm2Fe17N3 is another magnet compound having excellent magnetic properties comparable to those of Nd2Fe14B. Their large saturation magnetization, strong magnetocrystalline anisotropy, and high Curie temperature originate from the interaction between the T-3d electrons and R-4 f electrons. This article discusses the magnetism of rare-earth magnet compounds. The basic theory and firstprinciples calculation approaches for quantitative description of the magnetic properties are presented, together with applications to typical compounds such as Nd2Fe14B, Sm2Fe17N3, and the recently synthesized NdFe12N. [ABSTRACT FROM AUTHOR]

The iron chalcogenides FeTe and FeSe belong to the family of iron-based superconductors. We study the magnetism in these compounds in the normal state using the ab initio downfolding scheme developed for strongly correlated electron systems. In deriving ab initio low-energy effective models, we employ the constrained GW method to eliminate the double counting of electron correlations originating from the exchange correlations already taken into account in the density functional theory. By solving the derived ab initio effective models, we reveal that the elimination of the double counting is important in reproducing the bicollinear antiferromagnetic order in FeTe, as is observed in experiments. We also show that the elimination of the double counting induces a unique degeneracy of several magnetic orders in FeSe, which may explain the absence of the magnetic ordering. We discuss the relationship between the degeneracy and the recently found puzzling phenomena in FeSe as well as the magnetic ordering found under pressure. [ABSTRACT FROM AUTHOR]

We study magnetic properties of NdFe12, NdFe11Ti, and NdFe11TiN theoretically from first-principles. These materials are related to strong ferromagnets containing rare-earth elements. The crystal electric field parameter A20 at the Nd site is calculated using the density functional theory in the generalized gradient approximation, with the open-core treatment for the Nd-f states. A20 in NdFe12 is -83 K, while substitution of an iron atom at the 8i site with titanium changes the sign of A20, suggesting that the Ti substitution induces a complex magnetic structure. Interstitial nitrogenation substantially increases A20 to 439 K, which is consistent with strong uniaxial anisotropy observed in the experiments. Titanium substitution suppresses the magnetization substantially, whereas nitrogenation enhances the magnetization. [ABSTRACT FROM AUTHOR]

We derive a second-order perturbation formula for an electronic system subject to spin–orbit interactions (SOI). The energy correction originates in the spin-conserving and the spin-flip transitions. The former are represented by the orbital angular momentum (OAM) acquired via the SOI. The latter come from the quantum fluctuation effect. By using our formula, we examine the relativistic electronic structures of a d orbital chain and L10 alloys. The appearance of OAM in the chain is understood by using a parabolic-bands model and the exact expressions of the single-particle states. The total energy is found to be accurately reproduced by the formula. The self-consistent fully relativistic first-principles calculations based on the density functional theory are performed for five L10 alloys. It is found that the formula reproduces qualitatively the behavior of their exact magnetocrystalline anisotropy (MCA) energies. While the MCA of FePt, CoPt, and FePd originates in the spin-conserving transitions, that in MnAl and MnGa originates in the spin-flip contributions. For FePt, CoPt, and FePd, the tendency of the MCA energy with the variation in the lattice constant obeys basically that of the spin-flip contributions. These results indicate that not only the anisotropy of OAM, but also that of spin-flip contributions must be taken into account for the understanding of the MCA of the L10 alloys. [ABSTRACT FROM AUTHOR]

We study magnetic properties of NdFe12, NdFe11Ti, and NdFe11TiN theoretically from first-principles. These materials are related to strong ferromagnets containing rare-earth elements. The crystal electric field parameter A20 at the Nd site is calculated using the density functional theory in the generalized gradient approximation, with the open-core treatment for the Nd-f states. A20 in NdFe12 is -83 K, while substitution of an iron atom at the 8i site with titanium changes the sign of A20, suggesting that the Ti substitution induces a complex magnetic structure. Interstitial nitrogenation substantially increases A20 to 439 K, which is consistent with strong uniaxial anisotropy observed in the experiments. Titanium substitution suppresses the magnetization substantially, whereas nitrogenation enhances the magnetization. [ABSTRACT FROM AUTHOR]

Aims: Neointimal formation remains a major limitation after arterial reconstruction. To overcome this problem, we focused on two important transcription factors, nuclear factor-kappaB (NFκB) and E2F. The purpose of this study was to determine the effects of simultaneous inhibition of these transcription factors on the formation of neointimal hyperplasia. [ABSTRACT FROM PUBLISHER]

Cohesive mechanisms and electronic properties of C 60 fullerites, various C 60 compounds including superconducting alkali fullerides and alkaline-earth fullerides, and polymerized C 60 materials studied in the framework of the density functional theory are reported. In various environments C 60 shows different cohesive mechanisms, i.e., van der Waals cohesion, ionic cohesion, metallic cohesion, and even covalent bonding. C 60 is an atomlike building block of new materials but has rich properties which one single atom can never show. The presence of two different facets on C 60, pentagons and hexagons, is pointed out to be very important in considering their solid-state electronic properties. [ABSTRACT FROM AUTHOR]

Cohesive mechanisms and electronic properties of C 60 fullerites, various C 60 compounds including superconducting alkali fullerides and alkaline-earth fullerides, and polymerized C 60 materials studied in the framework of the density functional theory are reported. In various environments C 60 shows different cohesive mechanisms, i.e., van der Waals cohesion, ionic cohesion, metallic cohesion, and even covalent bonding. C 60 is an atomlike building block of new materials but has rich properties which one single atom can never show. The presence of two different facets on C 60, pentagons and hexagons, is pointed out to be very important in considering their solid-state electronic properties. [ABSTRACT FROM AUTHOR]

Abstract. An unusual case of a toothpick perforating the stomach, then penetrating the liver, and thereafter forming a liver abscess is reported. A 48-year-old woman who had ingested a toothpick 1 month earlier was admitted to our hospital because of severe epigastralgia which had progressively worsened. A laparotomy was performed because a granulomatous abscess in the liver due to this ingested foreign body was suspected. We found a granulomatous abscess in the liver due to the penetration of the toothpick through the stomach. The toothpick had become completely embedded about 2 cm deep in the left lobe of the liver. When dissecting the tumor, a 5.5-cm toothpick was removed, and a partial lateral resection of the liver was performed. The histological diagnosis was a hepatic abscess with granulomatous change. This was a rare case of a migration of an ingested toothpick into the liver through the stomach. [ABSTRACT FROM AUTHOR]

Abdominal aortic aneurysm (AAA) is a common degenerative condition with high mortality in older men. Elective surgical or endovascular repair is performed to prevent rupture of large AAAs. In contrast, despite gradual expansion, small AAAs have a low risk of rupture, and there is currently no well-defined treatment strategy for them. Therefore, a pharmacological approach for AAA is expected in the clinical setting. Indeed, several therapeutic effects of pharmacological agents have been reported in experimental models, and some agents have undergone clinical trials. Treatment with statins, angiotensin-converting enzyme-inhibitors, antibiotics, and anti-inflammatory agents appears to inhibit the growth rate of AAA in humans. However, as the sample size and follow-up period were limited in these studies, a large randomized study with long-term follow-up of small AAA should be performed to clarify the effect of these agents. Recently, the regression of AAA using molecular pharmacological approaches was reported in experimental studies. The characteristics of these strategies are the regulation of multiple molecular mediators and the signalling networks associated with AAA formation. On the basis of the results of these investigations, it may be possible to repair the injured aortic wall and obtain the remission of AAA using pharmacological therapy. [ABSTRACT FROM AUTHOR]