Swelling behaviour of rubber vulcanizates: 2. Effects of tensile strain on swelling

The effects of tensile strain on the swelling behaviour of acrylonitrile-butadiene copolymer rubber vulcanizates were studied by real-time pulsed nuclear magnetic resonance (n.m.r.) measurements and volume swelling measurements at equilibrium. It was shown that tensile strain causes an increase of the initial swelling rate evaluated by n.m.r. measurements and of the swelling ratio of the rubber matrix at equilibrium. This behaviour was discussed qualitatively in terms of the molecular mobility of the network chains on the basis of Treloar's theory for swelling under deformation. It was suggested that the presence of reinforcing fillers in the rubber matrix exerts two noticeable effects on swelling under deformation: (1) a transient effect through some oriented structure induced by stretching, which restricts the increase of the swelling rate; (2) a strain amplification effect, which causes the increase of the average local strain in the rubber matrix and enhances the swelling ratio more remarkably proportional to the filler concentration as compared with that of the unfilled system.     

PCR-based identification of pathogenic Candida species using primer mixes specific to Candida DNA topoisomerase II genes

For rapid identification of Candida to the species level, degenerated primers and specific primers based on the genomic sequences of DNA topoisomerase II of C. albicans, C. dubliniensis, C. tropicalis (genotypes I and II), C. parapsilosis (genotypes I and II), C. krusei, C. kefyr, C. guilliermondii, C. glabrata, C. lusitaniae and Y. lipolytica were designed and their specificities tested in PCR-based identifications. Each of the specific primers selectively and exclusively amplified its own DNA fragment, not only from the corresponding genomic DNA of the Candida sp. but also from DNA mixtures containing other DNAs from several fungal species. For a simpler PCR-based identification, the specific primers were divided into three groups (PsI, PsII and PsIII), each of which contained four specific primer pairs. PCR with the primer mixes yielded four different sizes of PCR product, corresponding to each Candida sp. in the sample DNA. To obtain higher sensitivity of PCR amplification, sample DNAs were preamplified by the degenerated primer pair (CDF28/CDR148), followed by the main amplification using the primer mixes. By including this nested PCR step, 40 fg yeast genomic DNA was detected in the sample. Furthermore, we applied this nested PCR to a clinical diagnosis, using splenic tissues from experimentally infected mice and several clinical materials from patients. In all cases, the nested PCR amplifications detected proper DNA fragments of Candida spp., which were also identified by the standard identification tests. These results suggest that nested PCR, using primer mixes of the Candida DNA topoisomerase II genes, is simple and feasible for the rapid detection/identification of Candida to species level in clinical materials.     

Enzymatic degradation of esters of dichloropropanols: removal of chlorinated glycerides from processed foods

The esters of dichloropropanols from the byproduct of hydrolysates during food processing were degraded by the cell-free extracts of a dichloropropanol-assimilating bacterium of Pseudomonas sp. OS-K-29. 1-Acyloxy-2,3-dichloropropane was hydrolysed into the corresponding carbonic acid and 2,3-dichloropropanol, and then the dichloropropanol was dechlorinated. The esterase activity of the cell-free extracts was effective for the esters of the dichloropropanols and monoacylglycerides, but not for hydrolysing the lipase substrates such as triacylglycerides and Tween 60. A comparative study using a series of octanoyl glycerides and the esters of the dichlopropanols showed that the substrate specificities of the cell-free extracts were similar to the monoacylglyceride lipase from Penicillium camembertii.     

Copolymerization of phenylacetylene with various acetylenes by W- and Mo-based catalysts

In the copolymerization of phenylacetylene with various acetylenes catalysed by WCl₆·Ph₄Sn, the relative reactivity of monomer decreased with increasing steric effect of monomer, e.g. HC  Cn-Bu, HC  Cn-Hex > HC  CPh, HC  Cs-Bu > HC  Ct-Bu, MeCCPh, CICCPh. While 1-chloro-2-phenylacetylene (a disubstituted acetylene) showed high reactivity in the homopolymerization by Mobased catalysts, the reactivity was remarkably depressed in the presence of phenylacetylene as comonomer. Based on these results, the relative reactivity of the acetylenic monomers in copolymerization was explained in terms of competitive coordination of monomers to the propagating end.     

Preparation of high-modulus poly(ethylene terephthalate) fibers by vibrating hot drawing

A novel drawing method, vibrating hot drawing, was successfully applied to poly(ethylene terephthalate) fiber, which has a normal molecular weight (IV = 0.7 dL/g) and was prepared by melt spinning. The process was divided into three steps, with differing conditions in drawing temperature, applied tension, vibrating frequency, and amplitude. The drawing temperature and vibration frequency were decided by considering the α_a dispersion of the polymer. In spite of a low draw ratio (7.7) and a low crystallinity (0.55), the birefringence and dynamic storage modulus at room temperature of the 3rd-step fiber reached 0.260 and 36 GPa, respectively. The modulus remains at a high level at elevated temperatures, for example, 29 GPa at 100°C and 17 GPa at 200°C. Further, it was found from temperature and intensity of the α_a dispersion peak that the movements of amorphous chains are strongly inhibited. © 1996 John Wiley & Sons, Inc.     

Nucleotide sequences of alcohol acetyltransferase genes from lager brewing yeast,Saccharomyces carlsbergensis

The nucleotide sequences of alcohol acetyltransferase genes isolated from lager brewing yeast, Saccharomyces carlsbergensis have been determined. S. carlsbergensis has one ATF1 gene and another homologous gene, the Lg-ATF1 gene. There was a high degree of homology between the amino acid sequences deduced for the ATF1 protein and the Lg-ATF1 protein (75·7%), but the N-terminal region has a relatively low degree of homology. Southern analysis and contour-clamped homogeneous electric field analysis of Saccharomyces strains suggest that the ATF1 gene is located on chromosome XV in S. cerevisiae and that the Lg-ATF1 gene might originate from the ‘non-S. cerevisiae’ genome of S. carlsbergensis, which is similar to that of S. bayanus and S. pastorianus. The nucleotide sequence data reported in this paper will appear in the DDBJ, EMBL and GenBank data banks with the Accession Numbers D63449 (ATF1) and D63450 (Lg-ATF1).     

Fracture and acoustic emission characteristics of glass fiber reinforced plastics panels for hot water

This study deals with the fracture process and acoustic emission (AE) characteristics of a randomly oriented E-glass fiber mat reinforcement with a crosslinked polyester. These panels were evaluated after they were immersed in hot water. The fiber volume content of the panel was 19%. Glass fiber reinforced plastics (GFRP) panels wer immersed in water at 81°C. Bending and AE monitoring tests were Performed and after bending, the cross-section of the specimen was observed by an optical microscope and SEM. The influence of degradation, due to water immersion, on the changes of fracture process of GFRP is discussed. The dominant fracture mode of the virgin specimen was matrix cracks, whereas that of the immersed specimen was debondings at the fiber bundle/matrix and fiber/matrix interfaces. This change was caused by reduction of the bonding strength at the interface. The scale of fracture can be estimated by both AE amplitude and AE energy and this estimation method was used to estimate the fracture mode changes of GFRP panels immersed in hot water.     

Energetics of BAMO

3,3-Bis(azidomethyl)oxetane (BAMO) is a typical energetic azide polymer containing two N₃, bonds in the molecular structure. Since BAMO is a solidified polymer at room temperature, a liquid BAMO copolymer with tetrahydrofuran (THF) was synthesized in order to gain energetic binders for solid propellants. Various types of experiments were carried out to elucidate the decomposition and combustion processes of BAMO polymer, BAMO/THF copolymer, and crosslinked BAMO/THF copolymer. The heat produced by the decomposition is caused by the bond breakage of -N₃ to produce N₂, gas. The burning rate characteristics of crosslinked BAMO/THF copolymer depend largely on the mole fraction ratio of BAMO and THF.     

The influence of drawing,twisting, heat setting and untwisting on the structure and mechanical properties of melt spun polypropylene filament

The changes in structure and mechanical properties of melt spun polypropylene filaments were determined as the filaments were successively (i) drawn, (ii) twisted, (iii) annealed, and (iv) untwisted. Filaments spun to two different melt draw down levels were studied. The effects of draw temperature and draw ratio, extent of twist, annealing temperature, and the extent of untwisting were examined. Melt spun and twisted filaments (draw ratio of 1) were also considered. Structural characterization techniques used in this study include wide angle (WAXS) and small angle (SAXS) diffraction, scanning electron microscopy (SEM), birefringence and density measurement. Drawing increased crystalline orientation and at low temperatures disrupted the monoclinic unit. cell existing in the melt spun fibers. The drawing produced considerable fibrillation under all conditions even when carried out at 120°C. The fibrillation quid void formation due to low temperature drawing was more pronounced. The variation of WAXS patterns and mechanical properties of twisted drawn filaments was interpreted by presuming that the fibrils act in a manner analogous to that of the filaments in a continuous filament twisted yarn. In the case of incompletely drawn filaments the effect of additional drawing occurring during twistin must be considered. Twisted fibers annealed at 150°C sowed a drastic reduction in tensile properties, while those annealed at 125°C did not set the twist and caused the fibers to tend to untwist. Annealing at 140°C appeared to give satisfactory heat setting. Annealing of cold drawn and cold drawn and twisted fibers increased the density, removed many defects and reformed a well defined monoclinic crystal structure and a lamellar morphology. Untwisting of heat set filaments tended to give back the properties of hot drawn fibers. In some cases, however, the opening of cracks was noted.