Enhancement of bonding strength by graded structure at interface between apatite layer and bioactive tantalum metal

Tantalum metal is a candidate for use as an implant material in high load-bearing bony defects, due to its attractive features such as high fracture toughness and high workability. This metal, however, does not have bone-bonding ability, i.e. bioactivity, and therefore the development of bioactive tantalum metal is highly desirable. It is known that the essential prerequisite for an artificial material to show bioactivity is to form a bonelike apatite layer on its surface in the body environment. The same type of apatite layer is formed in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. The present authors previously showed that the apatite formation on tantalum metal in SBF was remarkably accelerated by treatment with 0.5 M-NaOH aqueous solution and subsequent firing at 300 °C, while untreated tantalum metal spontaneously formed the same apatite after a long soaking period. In the present study, the bonding strength of the apatite layer to the substrate was quantitatively evaluated in comparison with that to the untreated tantalum metal. Adhesive strength was measured as an estimation of bonding strength, and the surface microstructure of both the substrates was characterized in order to discuss the difference in the bonding strength in terms of surface structure. The apatite layer formed on the NaOH- and heat-treated tantalum metal shows higher adhesive strength than that formed on the untreated metal. The amorphous sodium tantalate layer formed on the tantalum metal by NaOH and heat treatments, has a smooth graded structure where its concentration gradually changes from the surface into the interior metal. Smooth graded structure with complex of apatite is constructed after soaking in SBF. The higher bonding strength of the apatite layer formed on the treated metal is attributed to its smooth graded structure.     

Combined effects of radon inhalation and antioxidant vitamin administration on acute alcohol-induced hepatopathy in mice

It has been reported that radon inhalation activates antioxidative functions in liver and has an antioxidative effect against hepatopathy similar to that of the antioxidative effects of ascorbic acid (VC) or α-tocopherol (VE). In this study, we examined the combined effects of radon inhalation and antioxidant vitamin administration on acute alcohol-induced hepatopathy in mice. ICR mice were subjected to intraperitoneal (i.p.) administration of alcohol after pretreating with air only (sham) or radon at a concentration of approximately 2000 Bq/m³ for 24 hours and i.p. administration of VC (300 mg/kg body weight) or VE (300 mg/kg body weight). In mice injected with alcohol, the combined radon and antioxidant vitamins treatment significantly decreased the activities of glutamic oxaloacetic transaminase in serum compared to not only the alcohol-administered group (sham group), but also the radon inhalation with alcohol administration group or the vitamin and alcohol administration group. In addition, radon inhalation significantly increased the antioxidant level, in such as the catalase activity and the total glutathione content in liver compared to the sham group. These results suggested that the combined radon and antioxidant vitamin treatment could effectively inhibit alcohol-induced hepatopathy in mice without any antagonizing action.     

Arraying needle-like TiO2 particles in a composite film by applying ac bias and its transmittance anisotropy

In an effort to improve energy-efficient windows, we experimented with a precursor slurry composite by using needle-like TiO₂ particles as the filler in a urethane matrix. Applying dc bias to the slurry failed to array the needle-like particles in the composite and to deposit on the film surface because of electrophoretic movement. However, applying ac bias of ±5 V to the precursor slurry composite for 12 h resulted in the needle-like TiO₂ particles being arrayed in the composite in a direction normal to the film surface. This resulted in an improvement in the energy efficiency of the material through an angular dependence of transmittance in the visible–near-infrared range.     

FDTD analysis of switching characteristics in magnetooptic functional devices using magnetostatic surface waves

Collinear magnetooptic interaction with magnetostatic surface waves (MSSW) can be used for wavelength‐selective switches, wavelength filters, and frequency shifters in wavelength‐division‐multiplexed (WDM) photonic networks and optical processing systems. The switching efficiency can be improved with a multilayer waveguide structure. To investigate the dynamic switching characteristics, the FDTD method was employed. The mode conversion between TE and TM mode was successfully demonstrated with FDTD simulation. The filtering characteristics were also evaluated. The FDTD results were compared with the result from the coupled mode theory, and good agreement was obtained. Switching of an optical pulse was also demonstrated by the FDTD method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(1): 40–47, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20501     

A Bayesian propensity score adjustment for latent variable modeling and MCMC algorithm

The estimation of the differences among groups in observational studies is frequently inaccurate owing to a bias caused by differences in the distributions of covariates. In order to estimate the average treatment effects when the treatment variable is binary, Rosenbaum and Rubin [1983. The central role of the propensity score in observational studies for causal effects. Biometrika 70, 41-55] proposed an adjustment method for pre-treatment variables using propensity scores. Imbens [2000. The role of the propensity score in estimating dose-response functions. Biometrika 87, 706-710] extended the propensity score methodology for estimation of average treatment effects with multivalued treatments.However, these studies focused only on estimating the marginal mean structure. In many substantive sciences such as the biological and social sciences, a general estimation method is required to deal with more complex analyses other than regression, such as testing group differences on latent variables. For latent variable models, the EM algorithm or the traditional Monte Carlo methods are necessary. However, in propensity score adjustment, these methods cannot be used because the full distribution is not specified.In this paper, we propose a quasi-Bayesian estimation method for general parametric models that integrate out the distributions of covariates using propensity scores. Although the proposed Bayes estimates are shown to be consistent, they can be calculated by existing Markov chain Monte Carlo methods such as Gibbs sampler. The proposed method is useful to estimate parameters in latent variable models, while the previous methods were unable to provide valid estimates for complex models such as latent variable models.We also illustrated the procedure using the data obtained from the US National Longitudinal Survey of Children and Youth (NLSY1979-2002) for estimating the effect of maternal smoking during pregnancy on the development of the child's cognitive functioning.     

Impact of fertilizer on a small watershed of Lake Biwa: use of sulfur and strontium isotopes in environmental diagnosis

Sulfur and strontium isotopes (delta(34)S and (87)Sr/(86)Sr) were determined in 39 river water samples collected over three different cultivation periods (April, May, and June), and in several materials used for comparison (fertilizers, detergents, soils, irrigation and agricultural waters), to evaluate the impact of fertilizers on a small agricultural watershed of Lake Biwa, in central Japan. delta(34)S values in river water decreased (from +5.8 to -2.0 per thousand) with increasing SO(4) concentrations (3.8 to 93.2 ppm) from upstream to downstream of the watershed. Comparison of river water S isotopes with those of possible source materials indicates that the enrichment of SO(4) can be attributed to the dissolution of two kinds of fertilizers: (1) compound fertilizers commonly used in this area and (2) ammonium sulfate which is applied on a small scale. In contrast, (87)Sr/(86)Sr values of river water decreased with time from April (avg. 0.71163), through May (avg. 0.71139), to June (avg. 0.71127). The tendency of the sample plots on the (87)Sr/(86)Sr vs. 1/Sr diagram suggests a time-dependent increase in the contribution of soil water to the river, which is partly affected by the Sr-bearing fertilizers. It is suggested that a maximum of 25% of dissolved Sr is derived from these fertilizers, while more than 75% of it is of rock origin. Mass balance calculations permitted us to evaluate the proportion of fertilizer contribution in each river. Combined use of S and Sr isotopes together with concentration data could be a new environmental diagnosis technique for rivers and soils in localized watersheds.     

Geometric control and tuneable pore size distribution of buckypaper and buckydiscs

The fabrication of buckypaper from unfunctionalised multi-walled carbon nanotubes (MWCNTs) without the aid of surfactants or surface modification techniques is accomplished through a novel and quick frit compression method. The dimensions can be controlled through the size of the syringe housing and the through the mass of carbon nanotubes added. Their thicknesses are typically much larger than surfactant-cast buckypaper and range from 120 μm up to 650 μm; buckypaper with thicknesses larger than 500 μm we call buckydiscs. Buckypaper and buckydiscs are mechanically robust to handle, flexible, stable in solvents and possess larger porosities than Triton-X100 cast buckypaper. They also exhibit a memory effect when bending wetted samples, returning to their former geometry on drying. Buckypaper and buckydiscs were studied by mercury intrusion porosimetry to reveal a defined distribution of mesopores and small macropores that is, along with their density and apparent free volume, dependant on the casting solvent and therefore tuneable. Moreover, the frit compression system also allows control over the 3-dimensional geometry of the buckydiscs during the casting process.