Studies on syntheses and permeabilities of special polymer membranes. X. Effects of conditions of membrane preparation on permeation characteristics of cellulose acetate membranes in separation of aqueous polymer solutions

The effects of casting solvents, dissolution temperature of casting solution, and pH and temperature of gelation solution, etc. on the permeation characteristics of cellulose acetate membranes in the separation of polymers from their aqueous solutions were investigated, using aqueous solutions of poly(ethylene glycol) and poly(vinyl alcohol) as feed. The permeation characteristics were influenced significantly by the conditions of membrane preparation and of the permeation. It was found that a concentration polarization at the membrane surface occurred with poly(vinyl alcohol) molecules, but it was very small with poly(ethylene glycol). The above results were discussed in detail from points of view of structure of the resulting membranes and the interactions between the solvent, the solute in the feed and the cellulose acetate molecules.     

Grafting onto wool. III. Relationship between alpha- and beta-forms in wool keratin of grafted fibers

A quantitative study of the change in the x-ray intensity diffracted from the α- and β-crystalline phases of grafted fibers was carried out. It was demonstrated that a part of the α-helical sections is disrupted by the deposition of polymer and that during extension processes a marked stabilization for the remainder results from the interaction between the residues on the α-helix and the rigid polymer chain. It was also considered that the disrupted sections are identical to the portions which would be easily deformed by stretching. The results on fibers containing hydrophilic polymer suggested little possibility that the β-chain crystal is produced from the disrupted chains of α-crystallites. The mechanism of the so-called α–β transformation was proposed as ? α M, M^* ? β.     

Crosslinking structure of keratin: III. Rubberlike elasticity originating from non-uniform structures of the swollen hair and wool fibers

Hair and wool fibers treated with an 11 M LiBr solution containing N-ethylmaleimide showed typical rubberlike elasticity in a solution composed of equal volumes of 8 M LiBr and diethylene glycol monobutyl ether. Stress–strain relations of the swollen fibers were treated with a two-phase structural model: a mechanically stable phase of higher crosslinked domains and a rubbery phase with lower crosslink density. Stress–strain curves were analyzed by applying non-Gaussian chain statistics to the swollen keratin network, including microdomains, which act as reinforcing filler particles in rubber. Swollen hair showed about 2.3 times higher modulus than wool. It has been suggested that: (1) the difference in the modulus between the two keratins is attributable to the difference in the volume fraction of domains, and (2) the crosslink density of rubbery phase in hair is virtually identical to that in wool.     

Significance of elevated urinary N-acetyl-beta-D-glucosaminidase activity in chronic cadmium poisoning

N-Acetyl-beta-D-glucosaminidase (NAG) activity and beta 2-microglobulin (beta 2-m) concentration were measured in the urine of inhabitants of a cadmium-polluted area (Cd), including patients with, or suspected, "itai-itai" disease and control subjects. Urinary NAG activity increased with increasing beta 2-m concentration up to about 100 U/g creatinine; above this value the NAG activity did not increase with increasing beta 2-m concentration. Urinary NAG activity thus represents another useful indicator of renal tubular damage caused by Cd poisoning since the mechanisms for the excretion of NAG and beta 2-m into urine are thought to be different.     

Comparison of miscibility in poly(N-vinylcarbazole)/polystyrene and polyoxyethylene blends by excimer fluorescence

Summary It is for the first time found that poly(N-vinylcarbazole)(PVCz)/polystyrene (PS) blends have lower miscibility on molecular level than that of PVCz/polyoxyethylene (PEO) blends. This is obtained from excimer fluorescence properties of PVCz in PVCz (9.1–100%)/PS and PVCz (9.6–100%)/PEO blends. Schematic diagrams of phase-separated structure of the PVCz blends are proposed consistent with emission properties and phase-contrast microscopic images. Received: 8 February 2000/Revised version: 21 March 2000/Accepted: 27 March 2000     

Effect of Grain Size on the Thermal Conductivity of Si3N4

Polycrystalline Si₃N₄ samples with different grain-size distributions and a nearly constant volume content of grain-boundary phase (6.3 vol%) were fabricated by hot-pressing at 1800°C and subsequent HIP sintering at 2400°C. The HIP treatment of hot-pressed Si₃N₄ resulted in the formation of a large amount of ß-Si₃N₄ grains ∼10 µm in diameter and ∼50 µm long, and the elimination of smaller matrix grains. The room-temperature thermal conductivities of the HIPed Si₃N₄ materials were 80 and 102 Wm⁻¹K⁻¹, respectively, in the directions parallel and perpendicular to the hot-pressing axis. These values are slightly higher than those obtained for hot-pressed samples (78 and 93 Wm⁻¹K⁻¹). The calculated phonon mean free path of sintered Si₃N₄ was ∼20 nm at room temperature, which is very small as compared to the grain size. Experimental observations and theoretical calculations showed that the thermal conductivity of Si₃N₄ at room temperature is independent of grain size, but is controlled by the internal defect structure of the grains such as point defects and dislocations.     

Hydrogen ion desorption from amorphous carbon films induced by resonant core electron excitations

In order to get insight into the mechanism of structural change in tetrahedral amorphous carbon (ta-C) films that is induced by soft X-ray illumination at photon energies near the carbon core edge, the desorption of ions from ta-C films, as a possible process taking place concurrently with the photo-induced restructuring, was studied by time-of-flight (TOF) measurements of photo-ions as a function of photon energy. The results show that (1) the main ions detected are H⁺, (2) the desorption efficiency spectra exhibit a resonant peak at 286-287 eV which is common to all detected ions, and (3) is 3 eV lower than the resonant peak in the efficiency spectrum of photo-induced restructuring. These rule out the hypothesis that it is the photo-induced C-H bond rupture that causes the resonant soft X-ray-induced restructuring in ta-C films.     

Release Property of Progesterone from a Mixed-Base Suppository Consisting of Witepsol® W35 and Witepsol® E85

The mechanism of drug release from progesterone suppositories that consist of two types of hard fat (Witepsol® W35 and Witepsol® E85) was investigated. The strength, the thermodynamic characteristics, the surface structures, the drug release property, methylene blue penetration into suppositories, and change of surface structure after the dissolution test were employed for detecting characteristics of progesterone suppositories. The formulation with a mixing ratio of Witepsol W35 and Witepsol E85 at a 1:1 ratio showed the maximum strength value. The peak temperature of the suppositories showed a tendency to increase with increases in the ratio of Witepsol E85. The maximum height of the profiles measured with laser microscopy, from 20.8 μm to 29.2 μm, reached a maximum after 3 h of the dissolution test. When the suppositories were immersed in pH 7.4 phosphate buffer containing 0.5% methylene blue at 37°C, the penetrating area increased with time. The weight of the suppositories also increased with time. According to these findings, it was suggested that the release of drug from a mixed type of suppository containing progesterone was via the matrix and pores.     

History of plasticity and metal forming analysis

The research history of mechanics, physics and metallurgy of plastic deformation, and the development of metal forming analysis are reviewed. The experimental observations of plastic deformation and metal forming started in France by Coulomb and Tresca. In the early 20th century, fundamental investigation into plasticity flourished in Germany under the leadership of Prandtl, but many researchers moved out to the USA and UK when Hitler came in power. In the second half of the 20th century, some analyzing methods of metal forming processes were developed and installed onto computers as software, and they are effectively used all over the world.     

Disambiguating Japanese compound verbs

The purpose of this study is to disambiguate Japanese compound verbs (JCVs) using two methods: (1) a statistical sense discrimination method based on verb-combinatoric information, which feeds into a first-sense statistical sense disambiguation method and (2) a manual rule-based sense disambiguation method which draws on argument structure and verb semantics. In evaluation, we found that the rule-based method outperformed the statistical method at 94.6% token-level accuracy, suggesting that fine-grained semantic analysis is an important component of JCV disambiguation. At the same time, the performance of the fully automated statistical method was found to be surprisingly good at 82.6%, without making use of syntactic or lexical semantic knowledge.