First-principles study on structural, electronic, magnetic and thermodynamic properties of lithium ferrite LiFe5O8.

Lithium ferrite, LiFe5O8 (LFO), has attracted great attention for various applications, and there has been extensive experimental studies on its material properties and applications. However, no systematic theoretical study has yet been reported, so understanding of its material properties at the atomic scale is still required. In this work, we present a comprehensive investigation into the structural, electronic, magnetic and thermodynamic properties of LFO using first-principles calculations. We demonstrate that the ordered α-phase with ferrimagnetic spin configuration is energetically favourable among various crystalline phases with different magnetic configurations. By applying the DFT + U approach with U = 4 eV, we reproduce the lattice constant, band gap energy, and total magnetization in good agreement with experiments, emphasizing the importance of considering strong correlation and spin-polarization effects originating from the 3d states of Fe atoms. We calculated the phonon dispersions of LFO with ferrimagnetic and non-magnetic states, and subsequently evaluated the Gibbs free energy differences between the two states, plotting the P-T diagram for thermodynamic stability of the ferrimagnetic against non-magnetic state. From the P-T diagram, the Curie temperature is found to be ∼925 K at the normal condition and gradually increase with increasing pressure. Our calculations explain the experimental observations for material properties of LFO, providing a comprehensive understanding of the underlying mechanism and useful guidance for enhancing performance of LFO-based devices.

Superior thermoelectric properties of ternary chalcogenides CsAg5Q3 (Q = Te, Se) predicted using first-principles calculations.

Tailoring novel thermoelectric materials (TEMs) with a high efficiency is challenging due to the difficulty in realizing both low thermal conductivity and high thermopower factor. In this work, we propose ternary chalcogenides CsAg5Q3 (Q = Te, Se) as promising TEMs based on first-principles calculations of their thermoelectric properties. Using lattice dynamics calculations within self-consistent phonon theory, we predict their ultralow lattice thermal conductivities below 0.27 W m-1 K-1, revealing the strong lattice anharmonicity and rattling vibrations of Ag atoms as the main origination. By using the mBJ exchange-correlation functional, we calculate the electronic structures with the direct band gaps in good agreement with experiments, and evaluate the charge carrier lifetime as a function of temperature within the deformation potential theory. Our calculations to solve Boltzmann transport equations demonstrate high thermopower factors of 2.5 mW m-1 K-2 upon p-type doping at 300 K, comparable to the conventional dichalcogenide thermoelectric GeTe. With these ultralow thermal conductivities and high thermopower factors, we determine a relatively high thermoelectric figure of merit ZT along the z-axis, finding the maximum value of ZTz to be 2.5 at 700 K for CsAg5Se3 by optimizing the hole concentration. Our computational results highlight the great potentiality of CsAg5Q3 (Q = Te, Se) for high-performance thermoelectric devices operating at room temperature.

Differential association of metabolic syndrome and low-density lipoprotein cholesterol with incident cardiovascular disease according to sex among Koreans: a national population-based study.

AIMS: To investigate sex differences in the association of metabolic syndrome (MetS) and/or low-density lipoprotein cholesterol (LDL-C) with the incidence of cardiovascular and cerebrovascular disease (CCVD). METHODS AND RESULTS: A total of 4 702 458 individuals, aged between 40 and 70, without a previous diagnosis of CCVD, underwent at least two health screenings between 2009 and 2011. Of them, 4 193 878 individuals (48.6% women) fulfilled the study requirements. The main outcome measured was the incidence of CCVD. By the end of 2017, 68 921 CCVD events occurred. Men in high LDL-C only, MetS only, and both MetS and high LDL-C groups had higher risks of CCVD. Women in MetS only and both MetS and high LDL-C groups, but not those in high LDL-C only group, had higher risks of CCVD than those in the reference group. The effect of the interaction between the presence of MetS and high LDL-C levels on the primary outcome was found among women (P for interaction 0.016) but not among men (P for interaction 0.897). A combination of MetS and LDL-C > 3.4 mmol/L increased the risk of CCVD as compared to MetS or LDL-C > 3.4 mmol/L alone in both men and women. CONCLUSIONS: Metabolic syndrome confers an increased risk of CCVD irrespective of sexes; LDL-C > 3.4 mmol/L alone has a greater influence on CCVD occurrence in men than in women. Metabolic syndrome and high LDL-C beget a synergistically detrimental impact on the incidence of CCVD in both men and women. Treatment of dyslipidaemia and metabolic syndrome should be tailored according to patient characteristics.

Aneurysmal subarachnoid hemorrhage in third and fourth decades of life.

OBJECTIVE: The aim of this study was to compare clinical characteristics of ruptured aneurysms in young adults, of the third and fourth decades of life, and to compare several clinical characteristics affecting the outcome of patients. METHODS: We retrospectively investigated 1459 patients who underwent surgery and endovascular treatment for ruptured cerebral aneurysms from June 1992 to December 2010 and compared clinical characteristics. We also reviewed pre-existing medical conditions and perioperative complications. RESULTS: Among 1459 patients, there were 21 patients (1.44%) in the third decade and 104 patients (7.13%) in the fourth decade of life. Within two age groups, 88 (70.4%) were male and 37 (29.6%) were female, a ratio of 2.37 : 1. In both groups, we observed the anterior cerebral artery (ACA) aneurysm with the most frequency (p=0.028). In general, favorable outcome was achieved in both age groups (90.5% and 81.7%, respectively). An initial univariate analysis showed Hunt-Hess grade, Fisher grade, location of aneurysm, and rebleeding significantly associated with outcome after aneurysm rupture. Further, multivariate analysis demonstrated that only Hunt-Hess grade (grade 4-5) was a risk factor for the outcome (odds ratio=9.730, 95% confidence interval 2.069-45.756, p=0.004). CONCLUSION: The incidence of subarachnoid hemorrhage (SAH) was higher in the male population of the third and fourth decades of life. Aneurysms on the ACA were most frequently occurred in both age groups and the outcome of aneurysmal SAH among the third and fourth decades was favorable. Multivariate analysis revealed that high Hunt-Hess grade was a risk factor for patient's outcome.

Immunohistochemical analysis of apoptosis-inducing factor (AIF) expression in gastric carcinomas.

Mounting evidence suggests that both survival and death of cells play an important role in tumorigenesis. Apoptosis-inducing factor (AIF), a mitochondrial protein, plays an important role in the caspase-independent apoptosis. Also, recent studies have demonstrated that AIF has an oxidoreductase function that confers survival on the cells. As the roles of AIF in cancers are largely unknown, it may be important to identify the expression pattern of AIF in cancer tissues. In this study, which aims at defining the role of AIF in gastric tumorigenesis, we analyzed the expression of AIF in 60 gastric adenocarcinomas using immunohistochemistry. AIF expression was detected in the cytoplasm in 42 cases (70%) of gastric carcinoma. We also analyzed AIF expression in early (EGC) and advanced gastric carcinomas (AGC). AIF was expressed in 25 (73%) of 34 intestinal-type cancers and in 17 (65%) of 26 diffuse-type cancers. However, there was no significant difference in AIF expression with respect to the histological subtypes or the depth of invasions, either. In normal gastric mucosal cells, parietal cells, but not other mucosal cells, expressed AIF. Increased expression of AIF in malignant gastric epithelial cells compared to the normal mucosal cells suggests that AIF expression may play a role in gastric tumorigenesis. Also, the data suggest that AIF expression may play a role in the function of the gastric parietal cells.