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Nylon-6,6 vesicles are synthesized by the interfacial polycondensation of hexamethylenediamine and adipoyl chloride in microgravity, and their size and shape are compared with those formed in normal gravity. Two methods are applied for the nylon syntheses. First, a carbon tetrachloride solution of adipoyl chloride (AC) is sprayed into an aqueous solution of hexamethylenediamine (HD) in a reaction column from the nozzle at the bottom of the column, and inversely HD solution is sprayed into the AC solution column. Nylon vesicles containing the solvent inside are formed. In the second method, both of the reaction solutions are sprayed in an air column and the reaction proceeds by the collision of both mists. For both methods, the reaction is followed by the transmitted-light intensity of the reaction mixture. Furthermore, the products are analyzed by microscopic observation. The nylon vesicles were not completely spherical in most cases, even if formed in microgravity. However, the size and the aspect ratio of the vesicles in microgravity are always smaller than those in normal gravity.

Rotational relaxation times (τ) of anisotropic tungstic acid colloids (3.24 μm in major axis) in aqueous suspension are measured in microgravity (0G), normal gravity (1G) and at 2G. The measurements at 0G and 2G are achieved by parabolic and circular flights, respectively. The limiting slopes of the relaxation curves in the plots of the transmitted light intensity against time are close to zero at 0G irrespective of the flow directions in the flow cell, whereas those at 1G and especially at 2G depend on the flow direction by the convection of the suspension and particle sedimentation. Experimental errors at the τ values at 0G are small compared with those at 1G and 2G, which is ascribed to the lack of movement of impurities in the suspension such as quite small air bubbles, which cannot be recognized with the naked eye, and the convection of the suspension in microgravity. More reliable rotational relaxation times are obtained in microgravity; however, the relaxation times themselves are quite insensitive to gravity. Theτ values observed are larger than those calculated from the particle size, which indicates the important contribution of the electrical double layers formed around the colloidal particles.

Rotational relaxation times (τ) of anisotropic tungstic acid colloids in aqueous suspension containing sodium chloride or ethyl alcohol are studied in microgravity achieved by free-fall experiments. Experimental errors at 0 G, in many cases, are small compared with those at 1 G, which is ascribed to the lack of the convection of suspension in microgravity. Much more reliable data of the diffusion coefficients are obtained in microgravity. The limiting slopes of the relaxation curves in the plots of the transmitted-light intensity against time at 1 G depend on the flow direction of the suspension in the flow cell, whereas those at 0 G are close to zero irrespective of the flow direction. Sodium chloride decreases τ, whereas ethanol addition increases this time. These effects are ascribed to the thinning of the electrical double layers and to the increase in the suspension viscosity.

Rate coefficients (k) in the colloidal crystallization of monodispersed silica spheres in the presence of sodium chloride are studied in microgravity achieved by parabolic flights of an aircraft. Time-resolved reflection spectroscopy is made with a continuous circulating-type stopped-flow cell system. The k values decrease as the salt concentration increases both at 0 and 1 G and those in microgravity are smaller than those in normal gravity by 16% (maximum), especially in water and in the presence of a small amount of the salt lower than 2 × 10−6 mol/l. The rates in flight at 1 G are larger by 15% (maximum) compared with those at 1 G on the ground. The k values obtained at 0 G, 1 G in flight and 1 G on the ground agree excellently with each other for the suspensions with 3 × 10−6 and 4 × 10−6 mol/l sodium chloride. Disappearance of the downward diffusion of spheres and no convection of the suspensions are important for retardation in microgravity.

Nuclear spin maser based on a new masing mechanism is proposed, which is applicable to high-precision measurements of the electric dipole moment of neutron. To test this idea, a spin maser with a spin-polarized 129Xe gas as a working substance was constructed. After a detailed investigation of the spin maser operation in an ordinary spin-masing mechanism, we introduced an additional component in the feedback loop of the maser in order to implement the proposed masing mechanism. A self-sustained oscillation of transverse spins has been observed which clearly indicates a realization of spin masing arising from the new masing mechanism.

Rotational relaxation times (τ) and diffusion coefficients of ellipsoidal colloids of tungstic acid are studied in aqueous suspension in microgravity by free-fall experiments. τ values are evaluated from the relaxation traces of the optical transmittance of the suspension using the stopped-flow technique. Experimental errors at 0 G are small compared with those at 1 G, which is ascribed to lack of the movement of impurities in suspension such as quite small dust and bubbles and the convection of the suspension in microgravity. The limiting slopes of the relaxation curves in the plots of the transmittance against time at 1 G depend on the flow direction of the suspension in the flow cell, whereas those at 0 G remain zero irrespective of the flow direction. For more reliable diffusion coefficients are obtained in microgravity; however, the diffusion coefficients themselves are quite insensitive to gravity.