Influencing factors for diamond formation from several starting carbons

The possible influencing factors for diamond formation which prevent non-graphitic carbons from transforming to diamond in the presence of nickel as solvent-catalyst were pursued. The relative amount of nickel to carbon did not affect the behaviour of each starting carbon on diamond formation. The existence of a graphitic structure in the starting carbon was not the major prerequisite for diamond formation. Adsorbed gases on the starting carbon and atmospheric gases in the high pressure cell were found to be the most important influencing factors for diamond formation. Hydrogen and chemical species containing hydrogen atoms were the most harmful.     

A fuzzy self-tuning parallel genetic algorithm for optimization

The genetic algorithm (GA) is now a very popular tool for solving optimization problems. Each operator has its special approach route to a solution. For example, a GA using crossover as its major operator arrives at solutions depending on its initial conditions. In other words, a GA with multiple operators should be more robust in global search. However, a multiple operator GA needs a large population size thus taking a huge time for evaluation. We therefore apply fuzzy reasoning to give effective operators more opportunity to search while keeping the overall population size constant. We propose a fuzzy self-tuning parallel genetic algorithm (FPGA) for optimization problems. In our test case FPGA there are four operators—crossover, mutation, sub-exchange, and sub-copy. These operators are modified using the eugenic concept under the assumption that the individuals with higher fitness values have a higher probability of breeding new better individuals. All operators are executed in each generation through parallel processing, but the populations of these operators are decided by fuzzy reasoning. The fuzzy reasoning senses the contributions of these operators, and then decides their population sizes. The contribution of each operator is defined as an accumulative increment of fitness value due to each operator's success in searching. We make the assumption that the operators that give higher contribution are more suitable for the typical optimization problem. The fuzzy reasoning is built under this concept and adjusts the population sizes in each generation. As a test case, a FPGA is applied to the optimization of the fuzzy rule set for a model reference adaptive control system. The simulation results show that the FPGA is better at finding optimal solutions than a traditional GA.     

Synthesis of cementite-dispersed carbons by pressure pyrolysis of organoiron copolymers

Cementite-dispersed carbons were synthesized by pressure pyrolysis of divinylbenzene-vinylferrocene and styrene-vinylferrocene copolymer at temperatures below 600° C and the pressure of 125 MPa. The pyrolysis process of both copolymers was analysed by infrared spectra and magnetization of the pyrolysed substances. The absorption band of iron-carbon bond of divinylbenzene-vinylferrocene copolymer decreased on increasing its pyrolysis temperature from 300 to 450° C and finally disappeared at 500° C. The carbonization of divinylbenzene-vinylferrocene proceeded more rapidly than styrene-vinylferrocene at temperatures between 450 and 500° C. Styrene-vinylferrocene was heat-treated at 250° C for 2 h under 100 MPa affording a paramagnetic product, whereas the paramagnetic character of divinylbenzene-vinylferrocene was revealed after heat-treatment at 380° C. The saturation magnetization of cementite-dispersed carbon synthesized from both kinds of copolymers was comparable when the pressure pyrolysis was carried out at temperatures between 520 to 600° C at 125 MPa. The saturation magnetization of cementite-dispersed carbon formed at 550° C under 125 MPa was correlated linearly with the iron content in carbon. Threedimensional cross-linked divinylbenzene-vinylferrocene copolymer gave the highly dispersed cementite particles less than 50 nm with the coercive force of 950 Oe. On the other hand, the larger particle size of cementite up to 120 nm and the lower coercive force about 400 Oe were obtained in carbon matrix prepared by the pressure pyrolysis of styrene-vinylferrocene copolymer.     

Magnetic Properties of Ca3Ru2O7 Grown by a Floating Zone Method

We have succeeded in growing single crystals of Ca₃Ru₂O₇ by a floating zone method. The temperature dependence of magnetic susceptibility was measured in the temperature range from 2 to 300 K for the field along ab-plane and c-axis. The magnetic susceptibility shows anisotropic behavior. For T>55 K, the susceptibilities of both directions increase like the Curie–Weiss behavior with decreasing temperature. In the temperature range between 55 and 48 K, the susceptibility along ab-plane decreases steeply, while the one along c-axis is almost constant, which implies that the magnetic moment is aligned antiferromagnetically in the ab-plane. The susceptibilities drastically decrease in both directions at 48 K and are almost independent of temperature below 30 K.     

A static voltage fluctuation compensator for AC electric railway using self-commutated inverters

In this paper, the authors describe the basic configuration of an RPC (Railway Static Power Conditioner), its compensation principles and successful test results (using a small model of RPC). An ac electric railway is placed under a rapidly changing single-phase load. To avoid a voltage fluctuation under single-phase loads, electric power is received from a large source. At a feeding substation, three-phase electric power is transformed into two kinds of directional single-phase feeding electric power. The authors have already proposed a static voltage compensator for the ac electric railway, called “RPC.” The RPC links a pair of feeding circuits, using two self-commutated inverters. At the substation, the RPC accommodates an active power in the directional pair of feeding circuits to balance three-phase power, and possess a reactive power to regulate a three-phase voltage fluctuation. At a sectioning post, it can compensate for voltage drop using reactive power. It can also act as an active filter to compensate for harmonics. The authors have made a small model (220 V, 20 kVA) of the RPC, and report on the test results obtained using this small model under various conditions. The results indicate that the RPC can accommodate single phase loads, such as transformers and thyristors, can handle an exciter rush current from a transformer, can compensate for harmonics, and so on.     

Status of microchimerism in recipients 15 years after living related kidney transplantation

To study the relevance of microchimerism to the long-term outcome of renal allografting, we analyzed the frequency of microchimerism in kidney transplant recipients who had stable graft function for 15 years or longer. Among the 104 recipients who underwent kidney transplantation between 1971 and 1980, 27 renal allografts (26%) are still functioning. Among these 27 patients, 13 recipients whose donor was still alive and cooperative were investigated for the presence of microchimerism in the peripheral blood and for their immunological status. Microchimerism was tested using the polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) method. To test the sensitivity of PCP-SSCP, the peripheral blood obtained within 5 weeks after transplantation (four kidney transplants, three liver transplants) was also examined. Microchimerism was detectable in five patients within 5 weeks of transplantation (kidney transplantation, 3/4; liver transplantation 2/3. However, in the patients studied 15 years after transplantation, microchimerism was detected in only one recipient (1/13). In this chimeric patient, mixed lymphocyte response revealed high responsiveness against donor antigen. In contrast, some patients who did not have chimerism showed donor-specific hyporesponsiveness in mixed lymphocyte response assay and did not develop antidonor antibody, according to flow cytometric analysis. Microchimerism is an infrequent state in the long-term survivors of kidney allografting, and this state is irrelevant to donor-specific unresponsiveness.     

Effect of high-pressure pre-treatment of starting carbon on diamond formation

Four starting carbons differing in crystallinity and grain size were pre-treated with or without nickel at 3 GPa and 1800° C or at 6 GPa and 1700° C. Diamond synthesis from carbons pre-treated and then further treated in vacuum was carried out at 8 GPa and 1700° C. Pre-treated carbons with or without nickel, which were fully or partly graphitized, changed a little or did not convert to diamond at 8 GPa and 1700° C. Diamond did form from the pre-treated carbons after treatment in a vacuum at 1000° C. Diamond formation, even from the graphitized carbons, was found to be inhibited mainly by gases adsorbed on the treated carbon during the pre-treatment under high pressure.     

Electronic Structure of Sr2MoO4

The band structure for Sr₂MoO₄, which is isostructural with the unconventional spin-triplet superconductor Sr₂RuO₄, has been calculated within the local-density approximation. The results of the neutron-diffraction structure refinement used in the calculation are also presented. The elecronic structure of Sr₂MoO₄ resembles that of Sr₂RuO₄, while in Sr₂MoO₄ the anisotropy of Fermi velocity is considerably larger than that in Sr₂RuO₄. The neutron diffraction results and the structure optimization result suggest that the MoO₆ octahedron is less elongated than the previously reported value.     

Purification of properties of Saccharomyces cerevisiae cystathionine β-synthase

Cystathionine β-synthase (β-CTSase), which catalyses cystathionine synthesis from serine and homocysteine, was purified to homogeneity from Saccharomyces cerevisiae. The molecular mass of the enzyme was estimated to be 235 kDa by gel filtration and 55 kDa by sodium dodecyl sulphate–polyacrylamide gel electrophoresis, indicating that it is a homotetramer. The N-terminal amino acid sequence of the enzyme perfectly coincided with that deduced from the nucleotide sequence of CYS4, except for the absence of initiation methionine. The purified β-CTSase catalysed cysteine synthesis from serine (or O-acetylserine) and H₂S. From this finding, we discuss the multifunctional nature and evolutionary divergence of S-metabolizing enzymes.