Origin of the Verwey transition in magnetite: Group theory, electronic structure, and lattice dynamics study

The Verwey phase transition in magnetite has been analyzed using the group theory methods. It is found that two order parameters with the symmetries $X_3$ and $\Delta_5$ induce the structural transformation from the high-temperature cubic to the low-temperature monoclinic phase. The coupling between the order parameters is described by the Landau free energy functional. The electronic and crystal structure for the cubic and monoclinic phases were optimized using the {\it ab initio} density functional method. The electronic structure calculations were performed within the generalized gradient approximation including the on-site interactions between 3d electrons at iron ions -- the Coulomb element $U$ and Hund's exchange $J$. Only when these local interactions are taken into account, the phonon dispersion curves, obtained by the direct method for the cubic phase, reproduce the experimental data. It is shown that the interplay of local electron interations and the coupling to the lattice drives the phonon order parameters and is responsible for the opening of the gap at the Fermi energy. Thus, it is found that the metal-insulator transition in magnetite is promoted by local electron interactions, which significantly amplify the electron-phonon interaction and stabilize weak charge order coexisting with orbital order of the occupied $t_{2g}$ states at Fe ions. This provides a scenario to understand the fundamental problem of the origin of the Verwey transition in magnetite.Comment: 17 pages, 5 figures, 8 tables. Accepted version to be published in Phys. Rev.

ギョウセイ ノ タチバ カラ

The mortality rate for diabetes in Tokushima Prefecture has been the highest in the nation for thirteen years consecutively. To combat this, the prefectural government held an urgent campaign to promote awareness of diabetes last November and warn residents about the risk of this disease. Turning this crisis into an opportunity for change, the people of Tokushima have worked activity toward the prevention of diabetes, tackling the issue as a community. January 2006 saw the launch of the Tokushima Citizen Council for Health and the creation of additional tools to support efforts to improve public health : the Awa Odori Exercise program and the Healthy Awa Recipes series. During the present fiscal year, which began in April 2006, the prefectural government has been working with relevant organizations to organize special events to boost diabetes awareness, to advance preventive measures for lifestylerelated diseases, to launch a special“80-20”dental health program aimed at helping people keep 20 of their own teeth until age 80, and to promote healthy menus, among other activities. Walking and riding bicycles are great way to overcome a lack of exercise and fight type 2 diabetes. By avoiding automobile use when possible, residents can also help make Tokushima an eco-friendly city. As the Awa Odori Exercise program gains nationwide recognition, it will spread the word across Japan about the health benefits of this form of dance. The Healthy Awa Recipes, meanwhile, are closely tied to nutrition-education efforts and the movement to grow and consume food products locally. In these way the prefecture’s diabetes prevention measures are an effective way to kill three birds with one stone : not only do they help reduce incidence of the disease, they also boost national awareness of Tokushima and increase self-sufficiency in the prefectural economy. Through these programs, we hope to make Tokushima a prefecture that no longer sits in the unhappy position of having the nation’s highest diabetes mortality

Magnetite: Raman study of the high-pressure and low-temperature effects

We report the results of a low-temperature (300K-15K) high-pressure (up to 22GPa) Raman study of the Verwey transition in magnetite (Fe3O4). We use additional Raman modes observed below the Verwey transition to determine how the transition temperature changes with the quasihydrostatic pressure. Increase of the pressure results in the linear decrease of the Verwey transition temperature, with no discontinuity. The corresponding pressure coefficient dTV/dP is found to be ~ -5.2 K/GPa. Such a decrease is substantially larger than the one predicted by the mean-field Coulomb interaction model of the transition

Occurrence of the eelgrass pathogen, Labyrinthula zosterae, in Japan

The marine slime mold Labyrinthula zosterae, the causative agent of wasting disease of eelgrass Zostera marina, has been isolated from both 2. marina and 2. caulescens on the south coast of Japan. In addition, wasting-disease symptoms were produced in disease tests on leaves of Z. japonica and 2. marina using axenic cultures of L. zosterae isolated from Z. caulescens and Z. marina. Thus, the known host species of L. zosterae are expanded to include 3 species of Zostera. Although symptomatic necrotic lesions were observed in field-collected seagrass leaves, widespread die-off from wasting disease was not evident on the south coast of Japan

Modeling the multiple effects of temperature and radiation on rice quality

Ongoing climate change is likely to enhance the deterioration of rice quality that has been observed in western Japan, especially in Kyushu, since the 1990s. Therefore, it is important to examine the response of rice quality to environmental variation over a wide geographical domain. To that end, the aims of this study were (i) to propose a statistical model to predict rice quality based on temperature, total radiation during the ripening period, and their multiple effects; and (ii) to evaluate the model validity and uncertainty in prediction. A Bayesian calibration was adopted to account for uncertainty in the parameter values associated with non-climatic factors. The validation results showed that the model performed well in capturing the temporal trend and interannual variation in observed rice quality in all prefectures of Kyushu. We then performed the prediction experiment for rice quality in the extremely hot summer of the year 2010, which was omitted from the model calibration data. The results showed that the predictive capability of the statistical model is somewhat dependent on the calibration data, but this dependency does not necessarily mean that useful predictions for climates not in the calibration data are impossible

Ab Initio Phonon Dispersions for PbTe

We report first principles calculations of the phonon dispersions of PbTe both for its observed structure and under compression. At the experimental lattice parameter we find a near instability of the optic branch at the zone center, in accord with experimental observations.This hardens quickly towards the zone boundary. There is also a very strong volume dependence of this mode, which is rapidly driven away from an instability by compression. These results are discussed inrelation to the thermal conductivity of the material.Comment: 3 figures; typos corrected. Figure 1 replaced to correct labe

Expression of RAE-1, a ligand of the NKG2D Receptor, in Mice Adipocytes

Although epidemiological evidence has confirmed the role of heavy alcohol consumption as an established risk factor for esophageal, liver, and breast cancers, the molecular mechanisms underlying this effect are not fully understood, particularly with regard to breast cancer. In this study, expression of the retinoic acid early inducible-1 (RAE-1) gene was determined in mice adipocytes. RAE-1 is a ligand of the natural-killer group 2 member D (NKG2D) receptor, which plays a crucial role in tumor immunity. RT-PCR and Western blotting analysis demonstrated that TNF-α treatment induced RAE-1 mRNA and RAE-1 protein expression in adipocytes obtained from differentiated 3T3-F442A cells. Real-time RT-PCR analysis showed that 300 mM ethanol enhanced RAE-1 mRNA expression, which peaked 6 h after administration. In addition, RAE-1 mRNA was detected in visceral adipose tissue obtained from mice. These observations indicate that RAE-1mRNA is expressed in adipocytes and that its expression is enhanced by TNF-α, which has been shown to be induced in adipose tissue by long-term alcohol consumption. Furthermore, ethanol directly enhanced RAE-1 mRNA expression, suggesting that alcohol consumption enhances RAE-1 expression in adipose tissue and might modify tumor immunity. This finding might provide novel insight into the mechanism of alcohol-associated carcinogenesis

Charge and orbital order in Fe_3O_4

Charge and orbital ordering in the low-temperature monoclinic structure of magnetite (Fe_3O_4) is investigated using LSDA+U. While the difference between t_{2g} minority occupancies of Fe^{2+}_B and Fe^{3+}_B cations is large and gives direct evidence for charge ordering, the screening is so effective that the total 3d charge disproportion is rather small. The charge order has a pronounced [001] modulation, which is incompatible with the Anderson criterion. The orbital order agrees with the Kugel-Khomskii theory.Comment: 4 pages, 2 figure

Assessing uncertainty and complexity in regional-scale crop model simulations

Crop models are imperfect approximations to real world interactions between biotic and abiotic factors. In some situations, the uncertainties associated with choices in model structure, model inputs and parameters can exceed the spatiotemporal variability of simulated yields, thus limiting predictability. For Indian groundnut, we used the General Large Area Model for annual crops (GLAM) with an existing framework to decompose uncertainty, to first understand how skill changes with added model complexity, and then to determine the relevant uncertainty sources in yield and other prognostic variables (total biomass, leaf area index and harvest index). We developed an ensemble of simulations by perturbing GLAM parameters using two different input meteorology datasets, and two model versions that differ in the complexity with which they account for assimilation. We found that added complexity improved model skill, as measured by changes in the root mean squared error (RMSE), by 5-10% in specific pockets of western, central and southern India, but that 85% of the groundnut growing area either did not show improved skill or showed decreased skill from such added complexity. Thus, adding complexity or using overly complex models at regional or global scales should be exercised with caution. Uncertainty analysis indicated that, in situations where soil and air moisture dynamics are the major determinants of productivity, predictability in yield is high. Where uncertainty for yield is high, the choice of weather input data was found critical for reducing uncertainty. However, for other prognostic variables (including leaf area index, total biomass and the harvest index) parametric uncertainty was generally the most important source, with a contribution of up to 90% in some cases, suggesting that regional-scale data additional to yield to constrain model parameters is needed. Our study provides further evidence that regional-scale studies should explicitly quantify multiple uncertainty sources