This is a review of the replacement phenomena of chemisorbed gases on metal surfases. The replacement phenomena are discussed by classifing into two groups. The first group is “the simple mutual replacement”. In this group, the replacement phenomena are complicated at higher coverage. In the co-adsorption and/or the mutual replacement of H2 and CO, the surface species contained both H and CO are found, while in the simultaneous adsorption of H2 and CO, the LEED patterns of the adsorbed surface differ from these of the N2-covered surface or the CO-covered one. These results support that there is a strong interaction between the different kind adsorbates on the surface. In the second group called “the reactive replacement”, the preadsorbed CO on the surface is replaced by oxygen subsequently adsorbed with reaction such as CO2 desorption. In the cases discussed, qualitatively the sequence of the replacement are explaned by the value of the heat of adsorption. The nature of the replacement process will be clarified by the extensive studies including the adsorbate-adsorbate interaction.
Thin films of BN were prepared by a reactive sputtering method and the current-voltage (I-V) characteristics of an Al-BN-Au device were examined. The thickness of BN films ranged from 50 to 1000Å. The transmission electron microscopy and the infrared absorption measurements were conducted on thin films deposited on unheated Si substrates. The I-V characteristic for the unformed devices was in good agreement with the theoretical value for Schottky emission and the formed devices exhibited the voltage-controlled negative resistance (VCNR) phenomenon. The VCNR which was observed in this work differed, however, from that of oxide devices in that the voltage at the peak current depends on the partial pressure of O2 (Po2). Furthermore, it was found that the I-V characteristic of the formed samples fitted the relation, I=αV+βV2, below about 10-5Torr.
Modulation thresholds of the retina-brain visual system were measured with interference fringes formed by an apparatus which has been developed in our laboratory. Modulation thresholds of the foveal receptor-brain system were then calculated from these results and the MTF of the retina decided by H. Ohzu et al. It has been found that modulation sensitivities or line spread functions can be approximated by three Gaussian functions, one of which represents the excitatory high frequency response. The others represent the second excitatory and inhibitory responses at low frequency range, varying dynamically with retinal illuminance. Over-all visual system was also examined by moire fringes, and the MTFs of the eye optics were obtained. The performance of the eye optics, retina and other parts of the foveal visual system have been independently estimated. It also has been confirmed from experience of use by abnormal subjects that this technique and instrument can be applied to clinical ophthalmology.
Using the Sparrow criterion, the resolution of small double-bar targets placed in a bright background is investigated for an optical system under partially coherent illumination. The analysis is performed in one dimension. It is shown that the best resolution can be attained under the illumination condition that the ratio of the numerical aperture of the condenser to that of the objective is unity. It is further shown that the resolution of small double-bar targets with unequal complex transmittance becomes poorer compared with that for the case of equal transmittance.
The pendulum type mechanical analog of a small area Josephson junction is constructed with real time read out system of rotating angles and angular velocities. The rotating pendulum is driven by a torque generated electromagnetically. This torque corresponds to the applied current in the real junction. The angular velocity of the pendulm, which corresponds to the voltage in the junction, is converted to an electrical signal by a pulsed encorder. Resolution of the angle measurement is approximately one percent. Motions of the system is described by a simple equation of motion with an uncertainty below ten percent. Simulated d. c. characteristics show reasonable agreement with the experimental results of a point-contact junction. Profiles of a. c. Josephson voltage can be traced adequately, and switching characteristics are also simulated with appropriate boundary conditions.
Experimental results conducted in our la boratory showed that the electro-optical effects were closely related with surface alignment and dielectric anisotropy in DSM-type liquid crystal devices. Dielectric anisotropy of about -0. 2 was desirable for devices from view points of the threshold voltage, the contrast ratio and the recovery time. The vertical aligned cells (vertical cells) give higher con trast ratio but the parallel-aligned cells (parallel cells) give faster -response time and recovery time.
The relationship between the phase diagram and the composition dependence of the helical pitch was discussed for nematic-cholesteric liquid crystal mixtures. It is shown that the helical pitch versus composition curve has an extremum value for those mixtures in which the appearance of the smectic phase at an intermediate composition region is remarkably prominent. The result indicates that a lateral intermolecular interaction plays an important role in determining the helical structure of nematic-cholesteric mixtures.
The composition dependence of the helical pitch was discussed for ternary mixtures consisting of two nematic and one cholesteric compounds. It is shown that the reciprocal pitch follows the linear additive law as a function of composition between the two nematic components in the ternary mixtures. The result indicates that the helical pitch in the ternary mixtures can be estimated from the two helical pitch versus composition curves obtained for binary mixtures of each nematic and the cholesteric compounds.