Hiroaki Tsujimoto

The relationship between electropermeabilization and cell cycle and cell size of Saccharomyces cerevisiae

Yeast cells (Sacchromyces cerevisiae) in 0.9% NaCl solution containing phloxine B (dye) were treated by an application of a rectangular electric pulse. We input microscopic images of the yeast suspensions after the application into a computer, and measured whether each cell dyes or not, the phase in the cell cycle, and each cell size, using the software we had developed. After those measurements, we discussed the relationship between the yield of electropermeabilization (the ratio of dyed cells to the total cell number) and the phase in the cell cycle, and cell size. From the results, it was found that the yeast cells from S-phase to M-phase (S-M phase) in the cell cycle tend to be more permeated than G1-phase yeast cells, and in both phases the yield decreases with the increase in cell size.

Temperature Dependence of Anomalous Loop in Double-Layered Amorphous GdCo Film

The magnetic properties of double-layered amorphous GdCo film consisting of films with different compensation temperatures were studied. The theoretical hysteresis loops and their temperature dependence were deduced using the double-layer model. It was confirmed that the magnetic properties of the double-layered amorphous GdCo film agreed well with the prediction by the double-layer model. From the temperature dependence of the double-layered film, it is shown that an apparent compensation temperature exists between the original compensation temperatures in each layer. The appearance of the inverted loop is explained using the double-layer model; this was confirmed by experiments in the double-layered amorphous GdCo film.

The estimation of the yeast growth phase by nonlinear dielectric properties of the measured electric current

Abstract We measured the activity of yeast in each growth phase by using nonlinear dielectric properties. In this paper, we used a 2-electrode system, rather than the previous 4-electrode system, to measure the current waves for the analysis of the phase angle of response waves and the facilitation of the measurements. As a result, in the exciting frequency and field, 14 Hz and 0.75 V cm or 1.25 V cm −1 , the 2nd harmonic of the response wave for cell suspensions showed a significant difference between the induction phase and the others. However, for the supernatant of suspensions, there was no difference in the power spectrum of the even-numbered harmonics. With the phase angle, the same tendency was observed in the power spectrum. When another combination of field and frequency (0.25 or 1.75 V cm −1 and 7, 28, 35 or 42 Hz) was applied, there were no significant differences in either the power spectrum or the phase angle. These results were different from those measured by a 4-electrode system, although the range of frequency and field are almost the same. However, we found that the 2nd harmonics in the induction phase were different from those in the other phases. We can say that this 2-electrode system is applicable for the estimation of the growth of yeast cells.

Preparation and Properties of (NiZn)Fe2O4 Film by RF Reactive Sputtering

A reactive rf-sputtering method is used for depositing polycrystalline (NiZn)Fe2O4 films. The relations between the magnetic properties of the ferrite films and the sputtering conditions are examined in detail. The best condition of rf-sputtering, under which the magnetization of the films as well as the bulks is obtained and the initial relative permeabilities amount to 50~100 even in the frequency region over the Snoeks limit, is found. Finally, the way to improve the preparation of the films is discussed.

Real-Time Write Strategy Optimization Method for Optical Discs

An optimization method of the write strategy for optical discs to realize stable recording within the whole area of each optical disc is proposed. In this method, the write strategy is continuously optimized in the real-time base during the recording operation against the variation of recording characteristics in optical discs, in accordance with the recording position in the radial direction and environmental conditions. The optimization algorithm to select the suitable write strategy parameters to be optimized was established with reference to the database previously prepared. The effectiveness and lack of side effects in this method are experimentally confirmed using optical discs.