Analysis of the Microstructure of Mg2Si Thermoelectric Devices

High-performance Mg₂Si thermoelectric devices have been obtained by spark plasma sintering of high-purity, pre-synthesized, all-molten Mg₂Si powder. We studied the effects of source powder particle size on thermoelectric performance. To improve the performance, further investigation of the microstructure of the devices is needed. In this work we studied the microstructure of grain boundaries and interfaces between electrodes and Mg₂Si sintered bodies to increase understanding of Mg₂Si thermoelectric devices.     

Optical manipulation of multiple stable states in photorefractive four-wave mixing

Abstract

We propose an approach to manipulate the convergence in multiple solutions of phase conjugate reflectivity in photorefractive four-wave mixing. Although a method forcibly adding a π-phase shift to an incident beam has been already proposed to control the reflectivity, some restrictions have been required in the boundary conditions for the successful operation. Here, we control the reflectivity with the boundary conditions in which the phase shift operation is ineffective by itself. In our method, the phase shift operation is combined with the procedure of turning an incident beam on and off. With a numerical analysis of four-wave mixing, we show that our new approach brings drastic change in the spatial distribution of the index grating and leads the phase conjugate reflectivity which was not manipulated previously.     

Automatic restraint and visual detection of fatigue crack growth when applying an anti-fatigue smart paste to bolt holes

An anti-fatigue smart paste, which consists of fine alumina particles and silicone grease with low viscosity, was applied to a bolt hole (and its periphery in some cases) in a steel plate specimen, and the effects of the smart paste on automatic restraint and visual detection of fatigue crack growth were experimentally investigated through fatigue tests. Fractographic observations using a scanning electron microscope were also carried out. As a result, approximately 20～410% increase in failure life was produced by the wedge effect of the alumina particles in the smart paste. When the smart paste was applied, remarkable black colour developed in the white paste along the paths of crack growth, exceedingly facilitating the visual detection of the crack growth.     

Effects of dissolved organic matter surrogates on the partitioning of 17beta-estradiol and p-nonylphenol between synthetic membrane vesicles and water

Partition coefficients of two estrogenic compounds, 17beta-estradiol (E2) and p-nonylphenol (NP), between synthetic membrane vesicles (K'lipw values) and water were determined using equilibrium dialysis to evaluate the potential biological uptake of these compounds with and without the presence of dissolved natural organic matter (DOM) surrogates, Suwannee River fulvic acid, dialyzed Aldrich humic acid, and polyphenolic tannic acid. Overall, K'lipw values for E2 and NP reduced by 20-30% with the increase of DOM concentration from 0 to approximately 4 mg of C/L, a typical DOM concentration in the aquatic environment. This trend for E2 and NP is similar to that obtained by other researchers for moderately hydrophobic compounds including polycyclic aromatic hydrocarbons with three or four rings. A three-phase compartment model with three independent interactions, the sorption of E2 or NP by DOM surrogate (Koc), the sorption of DOM surrogates by membrane vesicles (KlipDOM), and the partition of E2 or NP by membrane vesicles (Klipw), was proposed, and K'lipw values for E2 or NP in the presence of DOM were calculated. The model predicted the decrease in Klipw values with the increase of DOM concentration, and the predictions using the three linear interactions agreed satisfactorily with the experimental results at relatively lower concentration of DOM.     

Long Crack R-Curve of Aligned Porous Silicon Nitride

Long crack R -curve of a porous Si₃N₄ with aligned fibrous grains was investigated, using a chevron-notched beam technique. A crack was constrained to propagate normal to the grain alignment. The crack growth resistance of aligned porous Si₃N₄ was much larger compared with that of dense Si₃N₄ ceramics. Microstructure observations showed that pullouts of fibrous grains in aligned porous Si₃N₄ markedly increased during crack propagation relative to those of dense Si₃N₄, due to the existence of pores. The efficient grain pullouts in porous Si₃N₄ increased the bridging stress at the crack wake.     

Suppression of inducible nitric oxide synthase expression and amelioration of lipopolysaccharide-induced liver injury by polyphenolic compounds in Eucalyptus globulus leaf extract

Eucalyptus leaf extract (ELE) is rich in hydrolyzable tannins. We examined the effects of ELE and its constituents on lipopolysaccharide (LPS)-induced liver injury in mice. Mice fed a diet supplemented with 1% ELE were intraperitoneally administered LPS. Six hours later, the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were significantly lower in the ELE-supplemented mice than in the controls; LPS-induced hepatic inducible nitric oxide synthase (iNOS) expression was also suppressed. ELE lowered LPS-stimulated iNOS expression in cultured RAW 264.7 macrophages. Furthermore, the aglycones of hydrolyzable tannins, gallic acid (GA) and ellagic acid (EA), inhibited iNOS induction to a greater extent than did ELE (15-fold higher). When mice were fed a 1% GA or EA diet, the increase in the serum ALT and AST activities and hepatic iNOS expression in response to the LPS challenge were significantly attenuated. Thus, hydrolyzable tannins in ELE ameliorate LPS-induced liver injury.     

Identification of an insertion sequence, IS1203 variant, in a Shiga toxin 2 gene of Escherichia coli O157:H7

An insertion sequence composed of 1310 bp was found in Shiga toxin 2 genes of some isolates of Escherichia coli O157:H7. This insertion sequence showed extremely high homology with IS1203 of E. coli O111:H(-). This IS1203 variant was inserted in the region encoding the amino-terminus of the B subunit with a duplication of 3 bp at the target site, resulting in inactivation of the Shiga toxin 2 gene.     

Evaluation of method for simultaneous determination of pesticide residues in fruits and vegetables by collaborative study

A collaborative study involving 8 laboratories was conducted to evaluate a method for the simultaneous determination of pesticide residues in 6 types of fruits and vegetables (spinach, tomato, apple, radish, cabbage and carrot). The method of analysis was the same as reported by Kakimoto et al. in 2003. One hundred and thirty-nine pesticides were spiked by each of 8 laboratories at levels of 0.1 microg/g (pesticides analyzed by GC/MS) or 0.5 microg/g (pesticides analyzed by HPLC) into the 6 kinds of samples. Statistical analysis showed that 111 pesticides could be analyzed with practical precision by this method. For screening purposes, the method could analyze 118 pesticides. The median values of the limits of detection were 0.001-0.041 microg/g. The calibration curves were linear in the range of 0.5-5 microg/mL for most pesticides with median correlation coefficients of 0.983-1.000.     

Effects of physical-chemical characteristics on the sorption of selected endocrine disruptors by dissolved organic matter surrogates

Sorption coefficients (K(oc) values) of selected endocrine disruptors for a wide variety of dissolved organic matter (DOM) were measured using fluorescence quenching and solubility enhancement. 17beta-Estradiol, estriol, 17alpha-ethynylestradiol, p-nonylphenol, p-tert-octylphenol, and dibutylphthalate were selected as endocrine disruptors. Aldrich humic acid, Suwannee River humic and fulvic acids, Nordic fulvic acid, alginic acid, dextran, and tannic acid were selected as DOM surrogates. The resulting sorption coefficients (log K(oc)) were independent of octanol-water partitioning coefficients (log K(ow)) of the selected endocrine disruptors, indicating the hydrophobic interaction is not the predominant sorption mechanism. Moreover, the K(oc) values for the selected endocrine disruptors, especially the steroid estrogens, correlated much better with UV absorptivity at 272 nm (A272) and phenolic group concentration of the DOM than with either the H/O or the (O+N)/C atomic ratio of the DOM. This suggests that the sorption mechanism is closely related to the interaction between pi-electrons and the hydrogen bonds, i.e., the affinity between phenolic groups of the steroid estrogens and DOM is suggested to provide a relatively large contribution to the overall sorption and yield the K(oc) values of the steroid estrogens as high as those of the alkylphenols and dibutylphthalate, which are suggested to be dominated by nonspecific hydrophobic interaction.     

A Broadcasting Scheme Considering Units to Play Continuous Media Data

Due to the recent proliferation of digital broadcasting systems, various schemes for broadcasting continuous media data such as music or movies have been studied. In general broadcasting systems, since clients have to wait until their desired data are broadcast, these schemes reduce the waiting time by dividing the data into several segments of equal size. However, continuous media data often have units for playing portions of the data. For example, data encoded by MPEG2 can be played every GOP (group of pictures). In this paper, we propose a scheme to reduce the waiting time considering the units. Our proposed scheme divides a continuous media data at every unit. By scheduling divided data so that clients finish receiving a unit before starting to play the unit, waiting time is effectively reduced.