High-temperature formation phases and crystal structure of hot-pressed thermoelectric compounds with chalcopyrite-type structure

In this study, we introduced the temperaturedependent formation phases and crystallographic parameters of hot-pressed silver gallium telluride AgGaTe_2 and copper gallium telluride CuGaTe_2 with chalcopyrite structure from 300 to 800 K. These two compounds are potential thermoelectric materials in the intermediate temperature range; however, the temperature-dependent formation phases and crystallographic parameters of hotpressed samples have not yet been analyzed in detail. The crystal structure analysis based on synchrotron X-ray diffraction(SXRD) measurements clarifies that impurity phases such as Te and Ag_2 Te in the AgGaTe_2 matrix and Te and CuTe in the CuGaTe_2 matrix appear at some temperature regions above 300 K. The existence of such impurity phases could be correlated with the increases of the electrical resistivity and Seebeck coefficient of the samples after multiple measurement cycles of the temperature-dependent transport properties from 300 to 800 K.The tetragonal lattice parameters a and c, tetragonal lattice volume, thermal expansion coefficients, tetragonal distortion, anion displacement parameter, and isotropic displacement parameter of the hot-pressed AgGaTe_2 and CuGaTe_2 were also analyzed. These crystallographic parameters are expected to substantially affect the thermoelectric properties of AgGaTe_2 and CuGaTe_2. Our results provide prospect of the long-term high-temperature stability and clues of the detailed analysis on the transport properties of hot-pressed AgGaTe_2 and CuGaTe_2, which should aid their development for thermoelectric applications.     

Preparation and characterization of stable dispersions of carbon black and nanodiamond in culture medium for in vitro toxicity assessment

Stable dispersions of carbon black and nanodiamond in culture medium were prepared by adding a pre-mixed dispersion of commercial carbon black or nanodiamond in aqueous bovine serum albumin (BSA) solution to culture medium. Dynamic light scattering revealed that carbon black and nanodiamond dispersions prepared in both NaCl solution and culture medium were highly stable. From DLVO theory and the results of zeta potential measurements, the theoretical effect of the electrostatic interactions between adsorbed BSA molecules was found to be minimal. The asymmetric flow field-flow fractionation measurements revealed that 0.05 or 0.56 mg/mL of BSA molecules were adsorbed on 0.11 or 1.09 mg/mL of carbon black, respectively, indicating 1:2 complexation of BSA with the colloidal particles. In the case of nanodiamond, 0.06 or 0.60 mg/mL of BSA molecules were adsorbed on 0.10 or 1.05 mg/mL of nanodiamond, respectively, indicating 1:2 complexation of BSA, which is the same ratio as in the case of carbon black. The adsorbed BSA molecules served as an effective stabilizing agent for the carbon black and nanodiamond, ensuring dispersion stability for at least 1 week. The preparation of the dispersions can be easily carried out by other researchers for toxicity studies.     

In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used.To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates.Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.     

Effect of Rare Earth Elements on Chill Formation and Nodule Count in Thin-section Spheroidal-Graphite Cast Iron

It was found that there was a close relationship between chill formation and nodule count in spheroidal-graphite (s-g) cast irons and, further, that there was a critical nodule count above which chill did not appear. The relationship between the critical nodule count and the cooling rate of specimens was expressed in the following quadratic equation:

N=0.58R²+19.07R+1.01

where N is the critical nodule count (mm^?2) and R is the cooling rate (°C/sec). Nodule count was increased by adding small amounts of a rare earth in combination with small amounts of calcium. Some heterogeneous phases with diameters of 1 μ or more were observed at the centres of graphite spheroids. These phases were composed of spherical rare-earth sulphides containing MgS, CaS and MgO. It is suggested that rare-earth sulphides contribute as a substrate on which graphite spheroids are formed in thin section cast irons, containing rare earth elements.     

Ultra Low-Dose Radiation: Stress Responses and Impacts Using Rice as a Grass Model

We report molecular changes in leaves of rice plants (Oryza sativa L. - reference crop plant and grass model) exposed to ultra low-dose ionizing radiation, first using contaminated soil from the exclusion zone around Chernobyl reactor site. Results revealed induction of stress-related marker genes (Northern blot) and secondary metabolites (LC-MS/MS) in irradiated leaf segments over appropriate control. Second, employing the same in vitro model system, we replicated results of the first experiment using in-house fabricated sources of ultra low-dose gamma (γ) rays and selected marker genes by RT-PCR. Results suggest the usefulness of the rice model in studying ultra low-dose radiation response/s.     

Migration of 4-nonylphenol from polyvinyl chloride food packaging films into food simulants and foods.

Migration of 4-nonylphenol (NP) from polyvinyl chloride (PVC) films for food packaging into food simulants and foods has been studied in domestic applications such as wrapping of food and reheating in a microwave oven. The migration of NP from the PVC films was determined by high-performance liquid chromatography with electrochemical coulometric-array detection (LC/ED). Twelve PVC films intended for commercial use and ten for domestic applications (total: 22 samples) were analysed. Some of the PVC films (two home-use and ten retail-use) contained NP at concentrations of between 500 and 3300 microg/g. Migration of NP from the films was influenced by the test conditions (n-heptane at 25 degrees C for 60 min, distilled water at 60 degrees C for 30 min and 4% acetic acid at 60 degrees C for 30 min). The amount of NP migrating from the PVC films into n-heptane (0.33-1.6 microg/cm2) was higher than the amount migrating into distilled water or 4% acetic acid (up to 9.7 ng/cm2) for the 11 films in which NP was detected. Up to 0.23% of the NP migrated into distilled water and 4% acetic acid and up to 62.5% into n-heptane. In addition, we investigated NP migration into cooked rice samples wrapped in PVC film. Using spiked samples the method gave an average recovery of 83.7% (n = 5) with a standard deviation of 2.5%. Migration of NP ranged from not detectable (< 1.0 ng/g) to 410.0 ng/g by reheating samples in a microwave oven for 1 min and from not detectable to 76.5 ng/g by keeping samples at room temperature for 30 min.     

Characteristics of creeping discharge developed in a narrow gap between insulators and effect of a backside electrode

Discharge characteristics have been investigated for a needle–plane electrode configuration containing insulating barriers with a narrow gap which has been placed between the needle and the plane. The characteristics of creeping discharge developed in the narrow gap of the barrier filled with SF₆ are especially considered. In the case of a configuration with a backside electrode below the needle, the corona generated from the needle easily extended to the gap. On the other hand, for a configuration without a backside electrode, the corona has hardly extended to the gap, and on increasing the applied voltage the corona developed greatly in the gap. This difference in corona extension should affect the flashover characteristics in the present system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 27–36, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10248     

Scaling theory for double-gate SOI MOSFET's

A scaling theory for double-gate SOI MOSFETs, which gives guidance for device design (silicon thickness t_si; gate oxide thickness t_ox) that maintains a subthreshold factor for a given gate length is discussed. According to the theory, a device can be designed with a gate length of less than 0.1 μm while maintaining the ideal subthreshold factor. This is verified numerically with a two-dimensional device simulator     

Lymphocytes mediate TNF-alpha-induced endothelial cell adhesion molecule expression: studies on SCID and RAG-1 mutant mice

TNF-alpha is known to elicit a rapid increase in the expression of specific endothelial cell adhesion molecules (ECAMs) within different vascular beds. The aim of this study was to determine whether lymphocytes contribute to the increased ECAM expression elicited by TNF-alpha. A dual radiolabeled mAb technique was used to quantify constitutive and TNF-alpha-induced expression of ICAM-1, VCAM-1, E-selectin, and P-selectin in different vascular beds (lung, heart, stomach, mesentery, small intestine, large intestine, and muscle) in wild-type and SCID mice. In reconstitution experiments, either whole splenocytes, T cell-enriched splenocytes, or B cell-enriched splenocytes were injected into SCID mice 48 h before TNF-alpha administration. Although the constitutive expression of ECAMs differed only slightly between wild-type and SCID mice, TNF-alpha-induced ECAM expression was markedly blunted in SCID mice compared with wild-type mice. This blunted response to TNF-alpha was also demonstrated for VCAM-1 in recombination activating gene (RAG)-1 mutant mice. Reconstitution studies revealed that administration of 50 x 10(6) splenocytes in SCID mice at 48 h before cytokine treatment restored the TNF-alpha-induced expression of VCAM-1 to levels normally observed in wild-type mice. Reconstitution with T cell- but not B cell-enriched splenocytes, also restored the TNF-alpha-induced expression of VCAM-1 in SCID mice to wild-type levels. These results implicate circulating T lymphocytes as modulators of the increased ECAM expression elicited by TNF-alpha.