Structure and mechanical properties of polyethylene-fullerene composites

The microhardness of films of fullerene-polyethylene composites prepared by gelation from semidilute solution, using ultrahigh molecular weight polyethylene (PE) (6×10⁶), has been determined. The composite materials were characterized by optical microscopy and X-ray diffraction techniques. The microhardness of the films is shown to increase notably with the concentration of fullerene particles within the films. In addition, a substantial hardening of the composites is obtained after annealing the materials at high temperatures (T _a=130 °C) and long annealing times (t _a=10⁵s). The hardening of the composites with annealing temperature has been identified with the thickening of the PE crystalline lamellae. Comparison of X-ray scattering data and the microhardness values upon annealing leads to the conclusion of phase separation of C₆₀ molecules from the polyethylene crystals within the material. The temperature dependence is discussed in terms of the independent contribution of the PE matrix of the C₆₀ aggregates to the hardness value.     

The use of phase diagrams and thermodynamic databases for electronic materials

Phase diagrams and a thermodynamic database constructed by the Calculation of Phase Diagrams approach offer powerful tools for alloy design and materials development. This article presents recent progress on the thermodynamic database for microsolders and copper-based alloys, which is useful for the development of lead-free solders and prediction of interfacial phenomena between solders and the copper substrate in electronic packaging technology. In addition, examples of phase diagram applications are presented to facilitate the development of Co-Cr-based magnetic recording media in hard disks and new ferromagnetic shape-memory alloys. For more information, contact K. Ishida, Tohoku University, Department of Materials Science, Graduate School of Engineering, Aoba-yama 02, Sendai 980-8579, Japan.     

Synthesis of Metastable Tetragonal (t') Zirconia–Ceria Solid Solutions by the Polymerized Complex Method

Homogeneous metastable tetragonal ( t ') solid solutions of ZrO₂— x mol% CeO₂ ( x = 20 and 50) were successfully synthesized by the organic polymerized complex method. The citric acid-ethylene glycol solution containing Zr and Ce ions was polymerized at about 140°C and then heat-treated at about 350°C to obtain a precursor. The black precursor was heated at 450°C and then fired up to 1300° or 1590°C, resulting in the homogeneous solid solutions.     

Nanocrystallization of Pd74Si18Au8 metallic glass

The crystallization process of Pd₇₄Si₁₈Au₈ amorphous alloy has been investigated by transmission electron microscopy, small angle X-ray scattering and three-dimensional atom probe techniques. Although literature suggests that the alloy decomposes into two glassy phases prior to the crystallization, we found that the crystallization occurs directly from a single amorphous phase by the primary crystallization of fcc Pd–Au solid solution, followed by the polymorphous crystallization of the remaining amorphous phase to a Pd₃Si phase.     

Pb-Free solders: Part 1. Wettability testing of Sn−Ag−Cu alloys with Bi additions

Maximum bubble pressure, dilatometric, and meniscographic methods were used in the investigations of the surface tension, density, wetting time, wetting force, contact angle, and interfacial tension of liquid alloys of Sn−Ag−Cu eutectic composition with various additions of Bi. Density and surface tension measurements were conducted in the temperature range 250–900 °C. Surface tensions at 250 °C measured under a protective atmosphere of Ar−H₂ were combined with data from meniscographic studies done under air or with a protective flux. The meniscographic data with a nonwetted teflon substrate provided data on interfacial tension (solder-flux), surface tension in air, and meniscographic data with a Cu substrate allowed determinations of wetting time, wetting force, and calculation of contact angle. The calculated wetting angles from meniscographic studies for binary Sn−Ag eutectic and two ternary Sn−Ag−Cu alloys were verified by separate measurements by the sessile drop method under a protective atmosphere with a Cu substrate. Additions of Bi to both ternary alloys improve the wettability and move the parameters somewhat closer to those of traditional Sn−Pb solders.     

Pb-Free solders: Part II. Application of ADAMIS database in modeling of Sn−Ag−Cu alloys with Bi additions

The ADAMIS database was used for calculation of the surface tension of the quaternary Sn−Ag−Cu−Bi liquid alloys by Butler's model. The resultant data were compared with those from the maximum bubble pressure measurements from Part I. The same thermodynamic database was next applied for the calculation of various phase equilibria. It was established that the Bi addition to the ternary Sn−Ag−Cu alloys (Sn-2.6Ag-0.46Cu and Sn-3.13Ag-0.74Cu in at.%; Sn-2.56Ag-0.26 Cu and Sn-2.86Ag-O.40Cu in mass%) causes lowering of the melting temperature and the surface tension to make the tested alloys closer to, traditional Sn−Pb solders. The simulation of the solidification by Scheil's model showed that the alloys with the higher Bi concentration are characterized by the lifting-off failure due to the segregation of Bi at the solder/substrate boundary. Thus, in modeling of new Pb-free solders, a compromise among various properties should be taken into consideration.     

Single-crystal growth and characterization of Cu2O and CuO

We have prepared a large number of crystals of cuprous oxide (Cu2O) by various procedures. Photoluminescence spectra of these crystals were studied to examine the concentration of defects, especially copper vacancy VCu to seek favourable conditions for growing Cu2O crystal. High-quality single crystals of Cu2O were prepared by the floating-zone melting method in air. Several synthetic crystals (specimens FA, FZ and GZ) and also a natural crystal were studied by X-ray analysis, inductively coupled plasma spectroscopy analysis, optical absorption, photoluminescence, photoconductivity and cyclotron resonance absorption, photoluminescence, photoconductivity and cyclotron resonance absorption to characterize their optical and electrical qualities. The best values of mobility and scattering time of photocarriers at T = 4.2 K are estimated to be h1.8 × 105 cm2 V–1 s–1 and h60 ps for positive holes, and 1.3 × 105 cm2 V–1 s–1 and 70 ps for electrons in Cu2O. Further, we report preliminary experimental results on transport property of crystals also of cupric oxide (CuO) purified by the floating-zone melting method.     

Design and control of JAIST active robotic walker

This paper presents the design and control of a novel assistive robotic walker that we call “JAIST active robotic walker (JARoW)”. JARoW is developed to provide potential users with sufficient ambulatory capability in an efficient, cost-effective way. Specifically, our focus is placed on how to allow easier maneuverability by creating a natural interface between the user and JARoW. For the purpose, we develop a rotating infrared sensor to detect the user’s lower limb movement. The implementation details of the JARoW control algorithms based on the sensor measurements are explained, and the effectiveness of the proposed algorithms is verified through experiments. Our results confirmed that JARoW can autonomously adjust its motion direction and velocity according to the user’s walking behavior without requiring any additional user effort.     

Lyapunov function-based obstacle avoidance scheme for a two-wheeled mobile robot

An obstacle avoidance scheme of a two-wheeled mobile robot is shown by selecting an appropriate Lya- punov function. When considering the obstacle, the Lyapunov function may have some local minima. A method which erases the local minima is proposed by using a function which covers the minima with a plane surface. The effectiveness of the proposed method is verified by numerical simulations.     

An application of the 2-nitrobenzenesulfenyl method to proteomic profiling of human colorectal carcinoma: A novel approach for biomarker discovery

In the development of novel biomarkers, the proteomic approach is advantageous because using it the cancer-associated proteins can be directly identified. We previously developed a 2-nitrobenzenesulfenyl (NBS) method to improve quantitative proteome analysis. Here, we applied this method to proteomic profiling of colorectal carcinoma (CRC) to identify novel proteins with altered expression in CRC. Each pair of tumor and normal tissue specimens from 12 CRC patients was analyzed, and approximately 5000 NBS-labeled paired peaks were quantified. Peaks with altered signal intensities (>1.5-fold) and occurring frequently in the samples (>70%) were selected, and 128 proteins were identified by MS/MS analyses as differentially expressed proteins in CRC tissues. Many proteins were newly revealed to be CRC related; 30 were reported in earlier studies of CRC. Six proteins that were up-regulated in CRC (ZYX, RAN, RCN1, AHCY, LGALS1, and VIM) were further characterized and validated by Western blot and immunohistochemistry. All six were found to be CRC-localized, either in cancer cells or in stroma cells near the cancer cells. These results indicate that the proteins identified in this study are novel candidates for CRC markers, and that the NBS method is useful in proteome mining to discover novel biomarkers.