Surface structures of synthetic diamonds

Diamond crystals of about 2 mm in size were grown by the temperature gradient method using Ni, Ni-Fe alloy and Fe as solvent metals. Several characteristic patterns were seen on the surfaces of the grown diamonds and were found to correspond to the texture of the quenched solvent metals. A vague vein-like pattern appeared when Ni was used. The surface patterns became finer with the increase of the content of Fe in Ni-Fe alloy, and when 70 wt% Fe-30 wt% Ni alloy was used, very fine dendritic patterns were seen on all of the faces of diamond in accordance with the symmetries of the lattice. The patterns are formed by the precipitation of carbon atoms in the space of the dendrites of the solvent metals during the quenching process. Lamellar patterns and etch pits were seen when Fe was used. The patterns are formed when Fe dissolves the diamond surfaces to produce Fe₃C during the quenching process.     

Fatigue characteristics of ultra high molecular weight polyethylene with different molecular weight for implant material

In order to investigate the effect of molecular weight on fatigue characteristics in the ultra high molecular weight polyethylene (UHMWPE), tension–tension fatigue tests of notched specimens were carried out in the present study. The effects of frequency and stress ratio on the fatigue characteristics were also investigated and fractography was discussed. The fatigue strength does not increase with increasing molecular weight. The fatigue strength might be influenced by the high degree of crystallinity in spite of the decreased tie molecule density in this study. Almost no effect of frequency on the number of cycles to failure can be observed. However, the higher the frequency, the higher the crack tip temperature. The effects of heat and strain rate on the fatigue strength must be considered in polymer materials. At a high stress ratio, the stress–number of cycles to failure (S–N) curves shift to high number cycles to failure side. Both stress amplitude and mean stress influence the fatigue life of UHMWPE. © 2001 Kluwer Academic Publishers     

Formation and crystallization of gels in the Na2O-SiO2-TiO2-ZrO2 system

5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) gels together with Na₂O-MO₂ gels (MO₂ = SiO₂, TiO₂, ZrO₂) were synthesized and effect of Na₂O addition to the gel formation and crystallization behavior were studied. From Si(OC₂H₅)₄, Ti(iso-OC₃H₇)₄, Zr(n-OC₃H₇)₄ and NaOCH₃ solutions in EtOH without H₂O, transparent, opaque and heterogeneous gels were obtained. By SEM observation, it was found that the opague bulk gels, rich in TiO₂ or ZrO₂ component, contain agglomerated spherical particles of less than 10 m diameter. Crystallization temperature (Tc) measured by DTA decreased sharply from 1258°C (SiO₂) to 613°C (30Na₂O·70SiO₂) due to the increasing non-bridging oxygens in the Na₂O-SiO₂ system. But in the Na₂O-TiO₂ and Na₂O-ZrO₂ systems, Tc increased as Na₂O content was increased up to 10 mol%. The thermal stability, defined by Tc/TL ratio, decreased from Tc/TL = 0.77 (SiO₂) to 0.57 (5Na₂O·95SiO₂) or increased from Tc/TL = 0.30 (TiO₂) to 0.67 (30Na₂O·70TiO₂) with Na₂O addition. In the 5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) system maximum Tc was 891°C at 5Na₂O·76SiO₂·19ZrO₂ composition and decreased as TiO₂ or ZrO₂ contents increased. Compared with the SiO₂-TiO₂-ZrO₂ gels, Tc of the 5 mol%Na₂O containing gels (Na₂O-SiO₂-TiO₂-ZrO₂) was lower in SiO₂ rich composition and higher in TiO₂ or ZrO₂ rich compositions. It is assumed that addition of Na₂O changed the structure of amorphous TiO₂ and ZrO₂ someway to increase their thermal stability or amorphous forming ability. After DTA run up to 1000°C, cystalline phases precipitated in the 5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) gels were determined by XRD analysis.     

Emerging cell array based on reaction–diffusion

This article demonstrates the self-replication and self-organization phenomena based on a reaction–diffusion mechanism by computer simulation. The simulation model consists of a one-dimensional cell array. Each cell contains two kinds of chemical substances, activator u and inhibitor v, that can generate a reaction–diffusion wave, which is a spatial concentration pattern. The cells are supposed to be divided or deleted depending on the concentrations of chemical substances. We tried several kinds of diffusion coefficient in the model, and in some simulations, a self-replication process and a generating cell array with a metabolic process were observed. By applying the division rule and the apoptosis rule, cell arrays duplicate in two oscillating states, i.e., self-replication processes were observed. By applying a division rule and an annihilation rule, a cell array that has a stable length is generated by changing the cell components, i.e., generating a cell array by a metabolic process was observed. Surprisingly, these two phenomena are realized independently of the initial number of cells. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Shape oscillation of bubbles in a row excited by ultrasonic vibration

Behaviors of bubble(s) exposed to an ultrasonic vibration are focused. Size of the bubbles interested in the present study is of O(1 mm) in diameter. The bubbles were injected through the micro syringe to the test fluid (water or water/surfactant mixture) filled in the rectangular tank. Ultrasonic vibration was irradiated to the bubble(s) after the detachment of the bubble from the tip of the syringe; thus the bubbles were exposed to the periodic oscillation in rising the test fluid. The authors clearly detect radial and shape oscillations under the large-amplitude vibration by use of high-speed camera. Preferable mode number of the shape oscillation, and the transition process from the radial to the shape oscillation are discussed.     

EACLE : Energy-Aware Clustering Scheme with Transmission Power Control for Sensor Networks

In this paper, we propose a new energy efficient clustering scheme with transmission power control named “EACLE” (Energy-Aware CLustering scheme with transmission power control for sEnsor networks) for wireless sensor networks, which are composed of the following three components; “EACLE clustering” is a distributed clustering method by means of transmission power control, “EACLE routing” builds a tree rooted at a sink node and sets the paths from sensor nodes taking energy saving into consideration, and “EACLE transmission timing control” changes the transmission timing with different levels of transmission power to avoid packet collisions and facilitates packet binding. With an indoor wireless channel model which we obtained from channel measurement campaigns in rooms and corridors and an energy consumption model which we obtained from a measurement of a chipset, we performed computer simulations to investigate the performance of EACLE in a realistic environment. Our simulation results indicate that EACLE outperforms a conventional scheme such as EAD (Energy-Aware Data-centric routing) in terms of communication success rate and energy consumption. Furthermore, we fully discuss the impact of transmission power and timing control on the performance of EACLE.     

Densification of magnesia-based inert matrix fuels using asbestos waste-derived materials as a sintering additive

A new concept for densification of minor actinide-containing inert matrix fuels (IMFs) using asbestos waste-derived materials was proposed for the effective utilization of resources and health protection of the general public. In this concept, magnesium silicates, which are mainly generated by the decomposition of asbestos in low temperature heat-treatments, are used as a sintering additive to achieve high density magnesia (MgO) -based IMFs at relatively low sintering temperature. In the present study, preliminary fabrication tests of MgO-based IMFs with magnesium silicates were carried out using cerium oxide (CeO₂) as a representative of minor actinide oxides. The sintered densities of MgO-based IMFs increased with use of the additives. The sintering behavior of MgO-based IMFs with magnesium silicate additives was discussed from the viewpoints of the effects of magnesium silicates on the densification of the MgO and CeO₂.     

Chitosan and marine phospholipids reduce matrix metalloproteinase activity in myeloma SP2 tumor‐bearing mice

An animal experiment was conducted to assess the antitumor effects of chitosan‐coated liposomes on myeloma SP2. The animal experimental groups designed for myeloma SP2 tumor‐bearing BALB/c mice were provided with five different drinks: (I) control (double‐distilled water); (II) squid phospholipid liposomes alone 1.0 mg/mL; (III) chitosan alone 5.0 mg/mL; (IV) squid phospholipid liposomes 1.0 mg/mL with chitosan 5.0 mg/mL in the form of a simple mixture; and (V) squid phospholipid liposomes 1.0 mg/mL coated with chitosan 5.0 mg/mL. At 20 days after implantation of the myeloma SP2 cells into mice, oral administration of the experimental drinks was provided for 35 days. There was significant suppression of tumor growth when chitosan and squid phospholipids were administered simultaneously in a simple mixture or as chitosan‐coated liposomes. Matrix metalloproteinase (MMP)‐2 and MMP‐9 activity was significantly less in the serum of mice that consumed chitosan‐coated liposomes than in control mice. We found that decreased tumor burden was related to MMP secretion. Therefore, chitosan‐coated marine phospholipid liposomes might be useful as potential agents for the treatment of myeloma SP2.     

Effect of catalyst combination on growth of single-walled carbon nanotubes

A new effective catalysts combination of iron — nickel for alcohol CVD technique was found. This catalyst catalyzed well as well as the typical catalyst of iron — cobalt catalysts, but gave a different diameter distribution. Calculating their electrical density of states under the assumption of their solid lattice structures, the result was fairly consistent with experimental results. The number of electrical states near Fermi level that is considered to be important for catalytic reaction is enough and the DOS of iron – nickel catalyst was quite similar to that of cobalt unlike manganese – copper catalyst. Consequently, a blend of catalysts that has a similar DOS to cobalt and has enough states near the Fermi level can be a good catalyst for alcohol CVD.     

Synthesis and characterization of fluorene-carbazole and fluorene-phenothiazine copolymers with carbazole and oxadiazole pendants for organic light emitting diodes

We report the synthesis and characterization of new series of the fluorene based polymers with carbazole and oxadiazole pendants for the generation of the white emission out of the EL device. In the fluorene backbone, hole transporting units such as carbazole or phenothiazine were incorporated to improve the EL brightness and efficiency. The PFCzOxd-co-PCzs and PFCzOxd-co-PPTZs in EL spectra showed maximum peaks at around 430 nm and additional large peaks at around 530 and 500 nm, respectively. In case of PFCzOxd-alt-PCz and PFCzCzPCz-co-PFOxdOxdPCz, the EL spectra of the polymers showed two distinct peaks comprising the maximum at 427 nm, which corresponds to the EL spectra of the conjugated backbone, and additional broad peaks at around 540 and 530 nm, respectively. The CIE coordinates of the devices from PFCzOxd-alt-PCz and PFCzCzPCz-co-PFOxdOxdPCz were (0.28, 0.33) and (0.25, 0.32), respectively, approaching the value of the standard white of National Television System Committee (NTSC) (0.33, 0.33).