Estimation of the Surface Energy of Polymer Solids

The methods to estimate the surface tension of polymer solids using contact angles have been reviewed in the first part. They are classified into the following three groups depending on the theories or the equations applied: (1) the methods using the Young's equation alone, (2) the methods using the combined equation of Young and Good-Girifalco, and (3) the methods using the equations of work of adhesion. Some notes and comments are given for each method and results are compared with each other. The two-liquids method for rather high energy surface is also introduced.

Next, some new possibilities to evaluate the surface tension of polymer solids are presented by our new contact angle theory in consideration of the friction between a liquid drop and a solid surface. The advancing and receding angles of contact (θ _a and θ _r ) are explained by the frictional tension γ_F and accordingly two kinds of the critical surface tension γ_C (γ_Ca and γ_Cr ) are given.

This work has shown that one of the recommendable ways to evaluate γ_S is either the maximum γ_LV cos θ_a or the maximum γ_C using the advancing contact angle θ_a alone, and another way is the arithmetic or the harmonic mean of the γ_Ca and γ_Cr . A depiction to determine the γ_C such as ln(1 + cos θ₀ ) vs. γ_LV with cos θ₀ = (cos θ₀ + cos θ_r )/2 has also been proposed.     

Sonochemical Preparation and Properties of Pt–3Y-TZP Nano-Composites

A uniformly aggregated 3 mol% yttria-stabilized tetragonal zirconia nano-powder (3Y-TZP) was prepared using thermal hydrolysis and the ultrasonic deagglomeration technique. The possibility of nano-engineering of Pt–3Y-TZP composite aggregates was studied. The as-synthesized Pt nano-particles (∼2 nm) were impregnated into zirconia nano-aggregates (20–45 nm). The morphology manipulation technique allowed production of the composite zirconia-based aggregates in which a significant fraction of the Pt particles was embedded into the densified zirconia aggregates. Using the colloidal technique and low-temperature (1150°C) sintering, we prepared the Pt-zirconia (0.5–1.5 wt% of platinum) nano-composites with average 3Y-TZP grain sizes of 120 nm, and with the platinum grains size in the range of 20–60 nm. The catalytic properties of composite Pt–3Y-TZP nano-composites were studied and described.     

Hydrodesulfurization activity of highly dispersed Co sulfide clusters prepared in zeolite cages

Zeolite-supported highly dispersed Co sulfide clusters are synthesized using Co(CO)₃ (NO) as a precursor. The amount of Co inCoS_x/zeolite anchored by a CVD technique increases as the Al/Si ratio of the zeolite increases, whereas the activity per Co atomdecreases for thiophene hydrodesulfurization (HDS). When an Na-exchanged USY zeolite is used, the Co sulfide catalyst shows a muchhigher HDS activity than a conventional Co—Mo/Al₂ O₃ catalyst. It is considered from XAFS and NO adsorption techniques that thehigh HDS activity of CoS_x/USY-Na is due to an extremely high dispersion of Co sulfide clusters. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation of Co–Mo/B2O3/Al2O3 catalysts for hydrodesulfurization: Effect of citric acid addition

The effect of citric acid (CA) addition was studied on the HDS of thiophene over Co–Mo/(B)/Al₂O₃ catalysts. The catalysts were characterized by means of LRS, Mo K-edge EXAFS, NO adsorption capacity measurements, and UV–vis spectra. The catalysts were subjected to a chemical vapor deposition (CVD) technique using Co(CO)₃NO as a precursor of Co in order to get deeper insights into the effect of citric acid addition. It was shown that the HDS activity was enhanced by the citric acid addition up to the CA/Mo mole ratio of around 1 and leveled off with further addition. The amount of Co anchored by the CVD was increased by the addition of citric acid, suggesting an increase in the dispersion of MoS₂ particles on the catalyst by the simultaneous presence of Co, Mo and citric acid, in conformity with the increase in the NO adsorption capacity. In contrast to Co–Mo catalysts, the edge dispersion of MoS₂ particles in Mo/B/Al₂O₃ was not affected by the addition of citric acid. The LRS, UV–vis spectra and Mo K-edge EXAFS showed that Co–CA and Mo–CA surface complexes are formed by the addition of citric acid. The Co–CA surface complex is more preferentially formed on CoMo/Al than on CoMo/B/Al, in agreement with a greater promoting effect of citric acid at a lower CA/Mo mole ratio for CoMo/Al than for CoMo/B/Al.     

Cloning and in vitro and in vivo expression of plant glutathione S-transferase zeta class genes

The cDNAs encoding the zeta class of glutathione S-transferases (GSTs) (GSTZs), which are multifunctional enzymes, were cloned from Arabidopsis thaliana L. and three lines of Brassica napus L. by RT PCR, and named AtGSTZ for A. thaliana ecotype Columbia gll, and BnGSTZ-A, BnGSTZ-B and BnGSTZ-C for B. napus cv. Shan 2A, Shan 213 and Ken C1, respectively. Sequence analysis revealed that the sequences of Shan 2A and Shan 2B were identical, and Ken C1 was different only in 3.8% of the sequence. Comparison of these sequences with published sequences in GeneBank showed that the sequences of the Brassica species were unpublished. The cDNAs were then inserted into two vectors for in vivo expression in Escherichia coli and in vitro expression in a wheat-germ cell-free protein synthesis system. All GSTZs were well expressed both in vivo and in vitro as an enzymatically active form, showing that all of them had both dichloroacetic acid dechlorinating and maleylacetone isomerase activities.     

Velocity, electromechanical coupling factor and acoustic loss of surface shear waves propagating along x-axis on rotated Y-cut plates of LiNbO3

Velocity and propagation loss of surface shear waves are measured on free-space and metallised surfaces of LiNbO3 crystals along the x-axis of rotated Y-cut plates as a function of rotation about the x-axis between 35° and 70°. The coupling factor obtained from the velocities is 0.20 for a 35° rotated Y-cut plate and 0.09 for a 70° plate. The coupling factor changes linearly with the rotation angle. The propagation losses over the whole range measured here are less than 5 dB/cm on both free-space and on metallised surfaces. These losses are fairly low and very favourable for fabricating s.a.w. filters.     

Solid-state microwave relay systems in Japan

In response to the rapidly increasing demand for communication facilities, microwave relay systems have played an important role in Japan's telecommunications network because of their economy and capability for broadband transmission. Their progress has been marked during the past 20 years and this development has been supported by advances in such diverse fields as radio propagation, antennas, microwave and electronic circuitry, electron devices, and, particularly, in solid-state techniques. This article reviews the history of microwave relay systems and describes the past and expected future contributions of the solid-state technology to these systems.