Yasuji Ohtsuka

Phagocytosis of latex particles by leucocytes. I. Dependence of phagocytosis on the size and surface potential of particles.

A series of latex particles, having different sizes and surface structures, were prepared and the dependence of phagocytosis of latex particles by leucocytes on the particle size and surface potential was investigated by measuring the oxygen consumption of leucocytes. Most of the phagocytic behaviour in the initial stages can be explained by susceptibility of particles to heterocoagulation i.e. attachment of small particles (latex particles) onto large particles (leucocytes) by the colloidal attractive force between the two kinds of particles. Specific behaviour for fine particles seems to be attributed to the contribution of steric stabilization by the hydrated layer on the particle surface and to the inability for the leucocytes to recognize very fine particles as foreign materials.

New interfacial-gel copolymerization technique for steric GRIN polymer optical waveguides and lens arrays

A new interfacial-gel copolymerization technique is proposed to prepare steric gradient-index (GRIN) optical waveguides and lens arrays. Since the GRIN profile is obtained from the thin-gel phase formed on the wall of a polymer substrate, many geometrical GRIN materials, such as axial-, radial-, and spherical-GRIN, can be monolithically fabricated. In this paper the principle of GRIN formation is clarified, and a few steric radial -GRIN circuit components are demonstrated.

Graded-index plastic optical fiber composed of methyl methacrylate and vinyl phenylacetate copolymers

Graded-index plastic optical fiber whose transmission attenuation is 143 dB/km at 651-nm wavelength was fabricated by heat-drawing the corresponding GI preform rod. This rod is prepared by the interfacial-gel copolymerization technique of methyl methacrylate (MMA) and vinyl phenylacetate (VPAc). The total scattering loss of the GI preform rod is ~60 dB/km at 633 nm. The graded-index profiles of the optical fibers are almost the same as those of the corresponding preforms with cladding sheaths. The index distributions of their core regions are quadratic against the distance from the center axis. The numerical aperture estimated from the index difference is ~0.20.

Spherical gradient-index sphere lens

The sphere lens with a spherical gradient-index (GRIN) was prepared for the first time by two modified suspension polymerization techniques. The index change of the 0.05–3.0-mm diam GRIN sphere was 0.02–0.04, and the index profile was almost quadratic. The optimum condition minimizing the spherical aberration of the GRIN sphere embedded in a certain substrate was confirmed. Furthermore, 1-D and 2-D GRIN sphere lens arrays were fabricated.

Determination of the refractive-index profile of light-focusing rods: accuracy of a method using Interphako interference microscopy

Two analysis procedures to determine the refractive-index profile using Interphako interference microscopy are compared for accuracy: (I) expressing the. profile as a five-nomial equation (proposed previously by Ohtsuka and Shimizu); (II) considering ray bending due to the index gradient and using Abel inversion (proposed by Iga et al.). Computer simulations indicate that the errors of both procedures are comparable except for index mismatching between the specimen periphery (n(p)) and immersion oil (n(2)) where Analysis (I) is more accurate than Analysis (II). The partial splitting method is more practicable than total splitting for a rodlike specimen. In addition, the improved partial splitting procedure facilitates reduction of error. The index profiles of the two selected light-focusing plastic rods (LFR) were calculated with these two procedures in various conditions. The correlation between resulting profiles and measuring conditions agreed with the simulations. It is concluded that Analysis (I) is preferable to Analysis (II) when n(p) not equal n(2) and that the improved partial splitting procedure is a practicable method for determining the index profile of a LFR.

Light‐focusing plastic rod prepared from diallyl isophthalate‐methyl methacrylate copolymerization

We have prepared a light‐focusing plastic rod, having a parabolic refractive‐index distribution, from a special and simple technique of diallyl isophthalate‐methyl methacrylate copolymerization. The internal transmission loss at 6328‐A wavelength is 1.0 dB/m. The period of sine curved ray path through the rod and the constant of refractive‐index gradient are 50 mm and 0.0158 mm−2, respectively. The 13‐mm‐long 3.35‐mm‐diam rod functions as a lens with a 38 ° 54′ field angle.

Modifications of a polymer latex

Abstract Monodisperse styrene-acrylamide copolymer latex (SA) prepared by an emulsifier-free aqueous polymerization was employed for modification to obtain a series of polymer latices having the same particle size but different kinds and different amounts of functional groups on their surface. Hydrolysis of SA obeyed first-order kinetics and resulted in anionic latices having carboxyl groups. The conversion of SA to a hydroxyl group-containing latex was governed by the pH of the reaction system. The Hofmann reaction and the Mannich reaction of SA were carried out to introduce primary and tertiary amines, respectively, on the particle surface. Hydrolysis was unavoidable in both reactions, which led to the formation of amphoteric latices. The number of ionogenic groups formed and, consequently, the isoelectric points of the latices could be changed by altering the reaction conditions.

Studies on the light-focusing plastic rod. 12: The GRIN fiber lens of methyl methacrylate–vinyl phenylacetate copolymer

The light-focusing plastic rod (LFR) and fiber (LFF) were fabricated by photocopolymerization of methyl methacrylate (MMA) with vinyl phenylacetate (VPAc). The MMA-VPAc LFR has much higher clarity than that of the MMA-vinyl benzoate LFR reported previously. Using the benzoin methyl ether as the initiator, which initiates photopolymerization preferentially, led to a much steeper index distribution than using benzoyl peroxide, which initiates thermal- and photochemical polymerization simultaneously. The relationships between preparation condition and optical characteristics were clarified in terms of the index distribution, light scattering, lens function, and attenuation of light transmission.

Fundamental study on latex reagents for agglutination tests.

Competitive adsorption of Fab and Fc fragments on to particles revealed that the main driving forces for the adsorption of Fab and Fc fragments are ionic and hydrophobic forces, respectively. Latex particles were sensitized with antihuman C-reactive protein-antibody under a condition where ionic binding force was suppressed, and hence antibody was supposed to attach to the particles predominantly at the Fc site. The resulting latex indicated a high efficiency for the determination of C-reactive protein. Among the latexes used, a partially hydrolysed styrene-acrylamide copolymer latex was the best with respect to test efficiency and storage stability.

Studies on the light-focusing plastic rod. 17: Plastic GRIN rod lens prepared by photocopolymerization of a ternary monomer system

Plastic GRIN rod lenses have been fabricated by photocopolymerization of ternary monomer systems. To select the monomer appropriate to photocopolymerization, we developed a computer program to predict the physical constants of the homopolymer from the chemical structure. Furthermore, according to the model of the gradient-index formation, methyl methacrylate (MMA)–acrylonitrile–vinyl benzoate (VB) monomer system and MMA–benzyl acrylate–VB monomer system were chosen as suitable systems. In both monomer systems, plastic GRIN rods with good lens functions up to the periphery were successfully obtained.