Various nonlinear optical effects are discussed which may show up when a laser pulse shorter than the relaxation times excites a resonant two-level system. They include self-induced transparency, superradiance, photon echo, optical amplification, optical nutation, higher-order resonant effects and some related effects in solids.
A new technique to produce very high static pressure is first described. It involves a method with which a spherical pressure vessel containing specimen is to be shrinked uniformly in a compressed liquid. The load forces acting upon the sphere outer surface are centrally concentrated to compress the specimen. The pressure can thus be elevated to the value at least higher than 2 Mb. When the density of vitreous silica compressed in the vessel above mentioned is measured and compared with the data of shock compression by Wackerle and Al'tshuler, it is possible to make an order estimation of the produced pressure. Next to be reported is the results of our recent experiments on the metallic transitions in such 3d transition metal oxides as α-Fe2O3, Cr203, TiO2, etc. Finally, a scope and a review on the modern high pressure physics are to be given.
The measuring principle of a movable tube flowmeter is based on Newton's law of motion, namely, the time rate of the momentum increase of a system is equal to the force acting on it. Under the assumption that the velocity at the ends of the movable tube are uniform, the flow rate may be calculated theoretically regardless of viscosity of the fluid. In the flowmeter, here reported, which we have named the perpendicular type, the inlet and outlet directions are perpendicular to each other. A flowmeter of this type has the merit that the flow rate is independent of the flow conditions (momentum, pressure, density and so on of the fluid) at one end of the movable tube. The merit seems to be especially useful for measurement of a compressible fluid. Two trial flowmeters of different kinds are examined experimentally by differential pressure measuring method and force measuring method, and the results of experiments are in good agreement with the theory.
The dielectric measurements of PAN and its four pyrolyzates are carried out in the temperature range from room temperature to about 140°C at frequencies from 0.3 Hz to 1 MHz. In the case of pyrolysis at about 180°C, conjugated double bonds are locally formed, resulting in restrictions of dipole orientation, and the Maxwell-Wagner type dispersion appears. For the pyrolysis around 300°C, on the other hand, the dispersion decreases in magnitude and shifts to a higher frequency. Moreover, in the range of higher temperature and lower frequency another dispersion due to space charge is observed.
The mechanical vibration noise in a He-Ne laser was investigated. The vibration noise in the laser output was calculated as a function of both the oscillating mode number and the amplitude of the mirror vibration. The noise was also measured when a mirror was put into forced vibration from using a piezo-electric transducer. From these data, it was found that the amplitude of the translational vibration must be less than λ/30, or the amplitude of the rotational vibration must be less than 0. 3 sec of arc, if it is required to sustain the fluctuation of laser output below 0.1%.
A study of electret thermal analysis (E. T. A.) has been made on tripalmitin and tristearin. Measurements of direct current conductivity (a), differential thermal analysis (D. T. A.) and dielectric constant (ω') and loss (ω") at 1 kHz were concurrently carried out at various temperatures for the same substances for comparison. The depolarization current shows peaks at temperatures at which crystalline transitions and melting take place. Under the same rate of increase in temperature, the peak temperatures for a and of the D. T. A. curve agree fairly well with those of the depolarization current. The results suggest that the E. T. A. can be used as a new technique of thermal analysis of materials of low molecular weight such as oils, fats and waxes.