Novel ET-coordinated copper(I) complexes: syntheses, structures, and physical properties (ET = BEDT-TTF = Bis(ethylenedithio)tetrathiafulvalene)

New molecular charge-transfer complexes of bis(ethylenedithio)tetrathiafulvalene (ET), (ET)Cu(2)Br(4) (1), (ET)(2)Cu(6)Br(10) (2), (ET)(2)[Cu(4)Br(6)ET] (3), (ET)(2)Cu(2)Br(4) (4), (ET)(2)Cu(3)Br(7)(H(2)O) (5), and (ET)(2)Cu(6)Br(10)(H(2)O)(2) (6), have been synthesized by diffusing reaction of ET and Cu(II)Br(2). Their crystal structures and physical properties have been investigated. X-ray analyses revealed that ET molecules coordinated to the copper ions with the sulfur atoms of the ethylenedithio groups in all compounds. The Cu-S distances are found in the range 2.268(5)-2.417(8) A, being close to the typical Cu(I)-S coordination bond distances. Strong d-pi interactions between d-electrons of the copper ions and pi-electrons of the ET molecules can be expected through the Cu-S coordination bonds. ET molecules behave as trans-bidentate ligands bonding to two different copper ions in 1 and 3, as cis-bidentate ligands in 2, 5, and 6, and as monodentate ligands in 4. In the crystal structure of 3, there are two types of ET molecules in the crystal structure, where the first type is a trans-bidentate ligand and the second forms a stacking structure by itself. Compounds 1, 2, 4, and 6 show semiconducting behavior down to low temperature (sigma(RT) = 1.6 x 10(-2) S cm(-1) and E(a) = 122 meV for 1, sigma(RT) = 2.1 S cm(-1) and E(a) = 21 meV for 2, sigma(RT) = 5.4 x 10(-4) S cm(-1) and E(a) = 239 meV for 4, and sigma(RT) = 5.1 x 10(-2) S cm(-1) and E(a) = 207 meV for 6). On the other hand, in 3, a metal-like region is observed along the b-axis and c-axis, due to the contribution of stacked ET molecules, and a metal-semiconductor transition occurs at 280 and 270 K, respectively. Also, 5 exhibits metallic conductivity in the temperature ranges 240-300 and 200-300 K along the b-axis and c-axis, respectively, despite the oxidation state of ET with 2+.     

Determination of traces of gallium and indium in ores by electrothermal-atomization atomic absorption spectrometry with matrix modifications

Methods were developed for the determination of gallium and indium in complex ores by electrothermal-atomization atomic absorption Spectrometry using matrix modifications. Nickel and nickel-ammonium sulfate as matrix modifier has enhanced the absorption signals for gallium and indium, respectively, eliminating the matrix interferences to allow their solutions in nitric acid to be used as calibration standards. No matrix separations are necessary. Results are quoted for a variety of black ore samples (Kuroko). The RSDs are 7.0% for gallium and 5.3% for indium at their 10 g/g levels, and the inverse sensitivities are 20 pg of gallium and 38 pg of indium for respective 1% absorption.     

A modification of profile empirical likelihood for the exponential-tilt model

We consider semiparametric models whose infinite-dimensional parameter corresponds to a probability distribution. The NPMLE based on the profile empirical likelihood for this kind of semiparametric model has attracted considerable interest. We propose the use of a modified profile empirical likelihood to improve the accuracy of this estimation. We consider applications to the exponential-tilt model and show that the accuracy of the proposed estimator is better than that of the conventional NPMLE by numerical study.     

Grain-boundary faceting at a = 3, [110]/{112} grain boundary in a cubic zirconia bicrystal

The atomic structure of a = 3, [110]/{112} grain boundary in a yttria-stabilized cubic zirconia bicrystal has been investigated by high-resolution transmission electron microscopy (HRTEM). It was found that the grain boundary migrated to form periodic facets, although the bicrystal was initially joined so as to have the symmetric boundary plane of {112}. The faceted boundary planes were indexed as {111}/{115}. The structure of the {111}/{115} grain boundary was composed of an alternate array of two types of structure unit: {112}- and {111}-type structure units. HRTEM observations combined with lattice statics calculations verified that both crystals were relatively shifted by (α/4)[110] along the rotation axis to form a stable grain-boundary structure. A weak-beam dark-field image revealed that there was a periodic array of dislocations along the grain boundary. The grain-boundary dislocations were considered to be introduced by the slight misorientation from the perfect = 3 orientation. The fact that the periodicity of the facets corresponded to that of the grain-boundary dislocations must indicate that the introduction of the grain-boundary dislocations is closely related to the periodicity of the facets. An atomic flipping model has been proposed for the facet growth from the initial = 3, {112} grain boundary.     

Information geometry of small diffusions

Information geometrical quantities such as metric tensors and connection coefficients for small diffusion models are obtained. Asymptotic properties of bias-corrected estimators for small diffusion models are investigated from the viewpoint of information geometry. Several results analogous to those for independent and identically distributed (i.i.d.) models are obtained by using the asymptotic normality of the statistics appearing in asymptotic expansions. In contrast to the asymptotic theory for i.i.d.models, the geometrical quantities depend on the magnitude of noise.

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Bayesian shrinkage prediction for the regression problem

We consider Bayesian shrinkage predictions for the Normal regression problem under the frequentist Kullback-Leibler risk function.Firstly, we consider the multivariate Normal model with an unknown mean and a known covariance. While the unknown mean is fixed, the covariance of future samples can be different from that of training samples. We show that the Bayesian predictive distribution based on the uniform prior is dominated by that based on a class of priors if the prior distributions for the covariance and future covariance matrices are rotation invariant.Then, we consider a class of priors for the mean parameters depending on the future covariance matrix. With such a prior, we can construct a Bayesian predictive distribution dominating that based on the uniform prior.Lastly, applying this result to the prediction of response variables in the Normal linear regression model, we show that there exists a Bayesian predictive distribution dominating that based on the uniform prior. Minimaxity of these Bayesian predictions follows from these results.     

First-principles investigation of R2O3(ZnO)3 (R=Al, Ga, and In) in homologous series of compounds

Atomic and electronic structures of R₂O₃(ZnO)₃ (R=Al, Ga, and In), which are included in homologous series of compounds, are investigated using first-principles calculations based on density functional theory. Three models with different R atom arrangements in the five-fold and four-fold coordination sites are examined. Al and Ga prefer the five-fold coordination sites. The formation energies are much larger than those of the competing phases, ZnR₂O₄, with a normal spinel structure. On the other hand, In₂O₃(ZnO)₃ shows no clear site preference and can be more stable than the spinel at high temperatures when configurational entropy contribution is taken into account. Electronic states near the conduction band bottom are mainly composed of Zn-4s orbital in Al₂O₃(ZnO)₃, while the contributions of Ga-4s and In-5s are comparable to Zn-4s in Ga₂O₃(ZnO)₃ and In₂O₃(ZnO)₃.     

Bayesian prediction based on a class of shrinkage priors for location-scale models

A class of shrinkage priors for multivariate location-scale models is introduced. We consider Bayesian predictive densities for location-scale models and evaluate performance of them using the Kullback–Leibler divergence. We show that Bayesian predictive densities based on priors in the introduced class asymptotically dominate the best invariant predictive density.