Identification of antimutagenic activities in the extract of an edible brown alga,Hijikia fusiforme (Hijiki) by umu gene expression system in Salmonella typhimurium (TA 1535/pSK 1002)

A significant antimutagenic activity was found in the hot-water-soluble extract of an edible brown alga, Hijikia fusiforme (Hijiki in Japanese) which showed a significant inhibitory effect on the umu gene expression system in SOS response against DNA damage of Salmonella typhimurium induced by typical genotoxic substances such as N-methyl-N′-nitro-nitrosoguanidine (MNNG), furylfuramide (AF-2), 2-acetylaminofluorene(2AAF) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), This activity was divided into polysaccharide and non-polysaccharide fractions and the former fraction showed a relatively high antimutagenic activity compared with that of the latter fraction. The polysaccharide fraction caused roughly equal inhibitory effects on MNNG-, AF-2-, 2-AAF- or Trp-P-1-induced mutagenesis and the major portion of the antimutagenic activity of this fraction was estimated to have a molecular weight of more than 30 kDa. The non-polysaccharide fraction also exhibited significant antimutagenic activities against MNNG-, AF-2-, 2-AAF- or Trp-P-1-induced mutagenesis and the major activity or this fraction was associated with low-molecular-weight substances with less than 3.5 kDa. We discuss the biological significance of the antimutagenic activities from H fusiforme which were compared with those of Laminaria japonica and Undaria pinnatifida reported previously.     

Turbulent diffusion combustion model using chemical equilibrium combined with the eddy dissipation concept for reducing detailed chemical mechanisms: An application of H2‐air turbulent diffusion flame

This research aims at building a turbulent diffusion combustion model based on chemical equilibrium and kinetics for simplifying a complex chemical mechanism. This paper presents the combustion model based on chemical equilibrium combined with an eddy dissipation concept model (CE‐EDC); the model is validated by simulating a H₂‐air turbulent diffusion flame. In the CE‐EDC model, the reaction rate of fuels and intermediate species are estimated by using the equations of the EDC model. Then, the reacted fuels and intermediate species are assumed to be in chemical equilibrium; the amounts of the other species are determined by the Gibbs free energy minimization method by using the amounts of the reacted fuels, intermediate species, and air as reactants. An advantage of the CE‐EDC model is that the amounts of the combustion products can be determined without using detailed chemical mechanisms. Moreover, it can also predict the amounts of the intermediate species. The obtained results are compared with Takagi's experimental data and the data computed by the EDC model, which uses the complex chemical mechanisms. The mole fractions of H₂, O₂, H₂O, temperature, and velocity obtained by using our CE‐EDC model were in good agreement with the reference data without taking into account the chemical reaction rates of the O₂ and H₂O. Furthermore, the mole fractions of OH and H are in good agreement with the results of the EDC model at high temperatures. On the other hand, the chemical equations involving OH and H were used for predicting the mole fractions of OH and H, which were similar to those obtained from the EDC model at low temperatures. Using the present CE‐EDC model, amounts of combustion products can be calculated by using a reduced chemical mechanism and the Gibbs free energy minimization theory. The accuracy of this model is in the same order as that of the EDC model. The CE‐EDC model uses reduced chemical mechanism concerning selected species, while the result of the chemical equilibrium calculation was employed to the other species; further, the accuracy of the CE‐EDC model is the same as that of the EDC model as to major species, T, U, and k. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20296     

Effect of annealing at temperature around glass transition temperature on molecular orientation and shrinkage of ethylene–vinyl alcohol copolymers

The effect of annealing on the molecular arrangement of ethylene–vinyl alcohol copolymers (EVA) was studied by optical methods. Drawn samples were annealed at temperatures near the glass transition temperature T_g in two cases; the first case allowed thermal shrinkage and the second case did not. For annealing below T_g, the hydroxyl groups were rearranged only to the stable position. Thermal shrinkage occurred by annealing at temperatures between T_g and T_g + 20–30 K. In the case of annealing at temperatures above T_g + 30 K, thermal shrinkage and crystallization occurred. The crystallization by annealing made the drawn sample difficult to shrink.     

Effect of uniaxial stretching on the tensile impact test for poly(ethylene terephthalate)

In order to correlate impact strength with the structure of polymeric materials, a tensile impact test was carried out using a uniaxially stretched poly(ethylene terephthalate) (PET) sheet. The structural factors were the draw ratio (λ) and the cut-out angle (θ) under the conditions of constant impacting speed (10.5 m/sec = 1.8 × 10⁴%/sec) and temperature (20° ± 1°C). The occurrence of structural anisotropy by stretching of isotropic amorphous quench-rolled PET was classified into three drawing stages: λ = ?1.5 or 2.0, ?3.5, and over 3.5. This is related to a deformation mechanism of masses with dimensions a few tenths of a μm and their boundaries. The boundaries are not clear until adiabatic deformation (mechanical impact) is applied. The area supporting the mechanical strength was limited to just a small section. Its character was affected by macroscopic deformation only in the direction parallel or near to the stretching direction, since the mechanical properties were not changed for the range of the cut-out angle θ = 45–90°.     

Gradient-Index polymer materials and their optical devices

A gradient-index (GRIN) plastic optical fiber was prepared by a heat-drawing process of the GRIN preform rod obtained by a new interfacial-gel copolymerization technique. The attenuation loss of the GRIN fiber was 179 kB/km at 650-nm wave-length and its numerical aperture was 0.20-0.25. To attain low loss and highly dense integrated circuits, steric radial-GRIN optical waveguide components such as GRIN branching, star coupler, multi-coupler, and a 2-D GRIN lens array, were monolithically fabricated by this technique. A novel spherical GRIN sphere lens, whose index function is symmetrical about the center of the sphere, with a low spherical aberration, was prepared by a modified suspension polymerization technique. A W-shaped GRIN sphere has been newly proposed to further reduce the spherical aberration, compared with the parabolic GRIN sphere previously proposed.