Biomedical subjects

Tsuneo Okubo

Publications and source records attributed to Tsuneo Okubo.

4 recordsLinked to original sources

PubMed2006

Drying dissipative patterns of the colloidal crystals of silica spheres in an dc-electric field.

Drying dissipative structural patterns of the colloidal crystals of silica spheres were studied under an dc-electric field. Platinum plate electrodes of anode and cathode were set on a cover glass. The broad hills accumulated with the spheres were observed at the outer edges of the dried film without and also with the electric fields. The column-like structures were formed by the electric flux, and movement of the spheres took place toward anode. The dried film kept colloidal crystal structure, where the nearest-neighbored spheres contact each other more compactly in the areas closer to the anode. Drying times needed for the complete dryness of the suspensions decreased as the strength of the electric field increased. Addition of sodium chloride to the suspensions retarded the movement of spheres toward the anode substantially.

Colloids↗

PubMed2005

Drying dissipative structures of nonionic surfactants in aqueous solution.

Macroscopic and microscopic dissipative structural patterns form in the course of drying a series of aqueous solutions of polyoxyethylenealkyl ethers. The shift from the single round hill with accumulated surfactant molecules to the broad ring patterns of the hill in a macroscopic scale occurs as the HLB (hydrophile-liophile balance) of the surfactant molecules increases. The patterns correlate intimately with the HLB values of the surfactants. Microscopic patterns of small blocks, starlike patterns, and branched strings are formed. The size and shape of the surfactant molecules themselves influence the drying patterns in part. The pattern area and the time to dryness have been discussed as a function of surfactant concentration and HLB of the surfactants. The convection flow of water accompanying the surfactant molecules, the change in the contact angles at the drying frontier between solution and substrate in the course of dryness, and interactions among the surfactants and substrate are important for the macroscopic pattern formation. Microscopic patterns are determined in part by the shape and size of the molecules, translational Brownian movement of the surfactant molecules, and the electrostatic and hydrophobic interactions between surfactants and/or between the surfactant and substrate in the course of solidification.

Journal Article↗

PubMed2002

Microgravity effects on thermodynamic and kinetic properties of colloidal dispersions.

Microgravity experiments on the physicochemical properties of colloidal dispersions reported hitherto have been reviewed. In microgravity, reliability and reproducibility of experimental data have been improved significantly by the elimination of convection in the suspension. Vanishment of the excess downward diffusion in microgravity has also produced a significant effect on properties of colloidal suspensions. For example, colloidal crystallization rates decreased in microgravity, whereas colloidal alloy crystallization rates increased. These results demonstrate the important role of the segregation effect in normal gravity. Colloidal silica formation reactions are retarded in microgravity, a phenomenon that is correlated deeply with disappearance of the downward diffusion of heavy products.

Journal Article↗

PubMedDate not supplied

ICH Q7A; 4.40 containment of beta-lactam antibiotics: an industry perspective.

The ICH Q7A guidance was finalized at the Fifth International Conference on Harmonization in San Diego, Nov. 9-11, 2000, and has been implemented in Japan since Nov. 2, 2001. However, in ICH Q7A; 4.40, Containment, there is no clear stipulation about whether a dedicated or multi-purpose facility should be employed in the production of highly sensitizing materials of different types of beta-lactam antibiotics, such as cephalosporins and cephems. This study presents the threshold levels for the induction of anaphylaxis by beta-lactam antibiotics to show that it is possible to use a multi-purpose facility for the production of several different types of beta-lactam antibiotics except for penicillins, if there are validated cleaning standards based on threshold values.

Anaphylaxis↗