Dish-like drying patterns of the water-soluble gelatin sheet wetted by an aqueous droplet.

Drying dissipative patterns of the water-soluble gelatin sheet wetted by an aqueous droplet were observed as a function of time elapsed. The arrayed clusters of dishes formed at the broad ring area and grew outward toward multiple arrays with time. The drying patterns formed by the cooperative contribution of wetting, swelling, dissolving, evaporative, convectional, sedimentary and solidifying processes. Drying patterns were studied also for aqueous ethanol, aqueous NaCl solutions and dispersions of colloidal silica and poly(methyl methacrylate) spheres. The dish patterns were observed for the water-soluble substrates, for the first time, in this work.

Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboadenylic acid) and poly(ribouridylic acid).

Dissipative drying patterns of aqueous mixtures of potassium salts of poly(riboadenylic acid) (KPolyA) and poly(ribouridylic acid) (KPolyU) were studied on a cover glass, a watch glass and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and the inner area of the dried film was observed. The fine multiple ring structures formed when the affinity of the polymer with the substrate is strong. Microscopic drying patterns changed drastically depending on the location in the dried film. Microscopic drying patterns were mainly dendritic long rods and sword (halberd)-like rods. They are assigned to the crystals of double-stranded and triple-stranded helices of the A:U and A:2U complexes, respectively. Cross-like drying patterns are also observed originated from the salt-polymer interaction.

Dissipative crystallization of potassium salt of poly(riboadenylic acid).

Dissipative patterns during the course of dryness of aqueous solution of potassium salt of poly(riboadenylic acid) (KPolyA) in the presence of potassium chloride were studied on a cover glass, a watch glass and a glass dish. Accumulation of KPolyA polymers forming the broad ring area and the drastic change in size and shape of the polymer single crystals depending on the location of the dried film, which are the typical effects of the dissipative crystallization, took place. Polymer crystals formed were spherulites, dendritic and rod-like assemblies, which are composed of the single or double helical chains depending on the pH-value of the initial solution.

Electro-optic effects of colloidal crystals.

Many kinds of electro-optic effects of colloidal crystals are observed and discussed on the basis of the fundamental properties of colloidal crystals themselves. Several electro-optic effects of colloidal crystals have been found by the authors mainly by use of light-scattering, reflection- and transmitted-light intensity measurements in an electric field, (a) waveform deformation, (b) phase-shift effects, (c) second-order harmonics generation, (d) self-resonance frequency generation (characteristic frequency and harmonic oscillation), (e) peak wavelength-shift effects and (f) waveform transformation. These electro-optic responses are explained successfully by the resonance-, visco-elastic- and structural relaxation-parameters of colloidal crystals.

Drying dissipative structures of lycopodium spore particles in aqueous dispersion.

Drying dissipative structures of aqueous dispersions of lycopodium particles (31 microm in average diameter) from the spores of Lycopodium clavatum were studied as a function of the particle concentrations in the presence and the absence of sodium chloride. The drying patterns formed on a cover glass, a watch glass and a Petri glass dish were observed macroscopically and microscopically. Lycopodium particles were the combination of hemisphere and tetrahedron in their shape and possessed the weakly acidic groups on their surfaces. The vague broad ring structure was observed even for the very large colloidal particles, and their size on a cover glass decreased as particle concentration decreased. Microscopic drying patterns almost disappeared except the short chain-like patterns. These observations support that the convectional contribution on the dissipative drying pattern formation is still effective in the lycopodium suspensions, though the convectional forces in the suspension are very weak compared with the sedimentation forces.

Phase behaviour of deionized binary mixtures of charged colloidal spheres.

We review recent work on the phase behaviour of binary charged sphere mixtures as a function of particle concentration and composition. Both size ratios Γ and charge ratios Λ are varied over a wide range. Unlike the case for hard spheres, the long-ranged Coulomb interaction stabilizes the crystal phase at low particle concentrations and shifts the occurrence of amorphous solids to particle concentrations considerably larger than the freezing concentration. Depending on Γ and Λ, we observe upper azeotrope, spindle, lower azeotrope and eutectic types of phase diagrams, all known well from metal systems. Most solids are of body centred cubic structure. Occasionally stoichiometric compounds are formed at large particle concentrations. For very low Γ, entropic effects dominate and induce a fluid-fluid phase separation. Since for charged spheres the charge ratio Λ is also decisive for the type of phase diagram, future experiments with charge variable silica spheres are suggested.

Rheological properties of deionized Chinese ink.

Rheological properties for Chinese ink in exhaustively deionized aqueous media were carefully examined. In the steady shear measurement, the shear viscosities of the ink could be well explained by considering the "effective" volume fraction of the particles in the ink including the electrical double layers and by using Einstein's equation for dilute suspension viscosity, when the particle volume fraction was substantially low. In the case that the volume fraction was higher, the shear viscosities showed extremely higher than those from Einstein's prediction, though the ink remained a Newtonian liquid. In the stress-strain measurement, the shear moduli were observed at strain smaller than 0.2. The "weak" aggregation among the particles in the ink under no shear or low shear rates was supported. It should be noted that the glue in the suspension plays an important role for the good liquidity of the ink and for the "weak" bridges among the particles resulting its good dispersion stability.

Colloidal crystals of core-shell type spheres with poly(styrene) core and poly(ethylene oxide) shell.

Elastic modulus and crystal growth kinetics have been studied for colloidal crystals of core-shell type colloidal spheres (diameter=160-200 nm) in aqueous suspension. Crystallization properties of three kinds of spheres, which have poly(styrene) core and poly(ethylene oxide) shell with different oxyethylene chain length (n=50, 80 and 150), were examined by reflection spectroscopy. The suspensions were deionized exhaustively for more than 1 year using mixed bed of ion-exchange resins. The rigidities of the crystals range from 0.11 to 120 Pa and from 0.56 to 76 Pa for the spheres of n=50 and 80, respectively, and increase sharply as the sphere volume fraction increase. The g factor, parameter for crystal stability, range from 0.029 to 0.13 and from 0.040 to 0.11 for the spheres of n=50 and 80, respectively. These g values indicate the formation of stable crystals, and the values were decreased as the sphere volume fraction increased. Two components of crystal growth rate coefficients, fast and slow, were observed in the order from 10(-3) to 10(1)s(-1). This is due to the secondary process in the colloidal crystallization mechanism, corresponding to reorientation from metastable crystals formed in the primary process and/or Ostwald-ripening process. There are no distinct differences in the structural, kinetic and elastic properties among the colloidal crystals of the different core-shell size spheres, nor difference between those of core-shell spheres and silica or poly(styrene) spheres. The results are very reasonably interpreted by the fact that colloidal crystals are formed in a closed container owing to long-range repulsive forces and the Brownian movement of colloidal spheres surrounded by extended electrical double layers, and their formation is not influenced by the rigidity and internal structure of the spheres.

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.

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.

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.

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.