Photooxidative degradation of polyethylene containing flame retardants by monochromatic light

Photodegradation of incombustible polymer materials [high-density (HD) and low-density (LD) polyethylene (PE) containing 0.5 to 2.0 phr of decabromodiphenyl ether (DBDE) or tetrabromobisphenol A (TBA) as a flame retardant] were studied using an Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm. Ultraviolet and Fourier transform infrared (FTIR) spectra were taken to estimate the chemical changes caused by photoirradiation. Molecular weight change was followed by gel permeation chromatography (GPC) measurements. It was found that the photostability of PE samples was reduced by the addition of flame retardants. The threshold wavelengths of photodegradation are 320 nm and 360 nm for PE–TBA samples and PE–DBDE samples, respectively. Main-chain scission is favored when the irradiation was carried out with the light of wavelength 300 nm for HDPE–DBDE and HDPE–TBA samples. The most effective irradiation wavelengths for crosslinking are found to be 300 nm and 280 nm for LDPE–DBDE and LDPE–TBA samples, respectively. 1995 John Wiley & Sons, Inc.     

Automatic EEG interpretation adaptable to individual electroencephalographer using artificial neural network

In view of the fact that the visual EEG interpretation could be a subjective task and may vary among the electroencephalographers, the main objective of this study was to develop an automatic EEG interpretation system which is adaptable to each electroencephalographer. The system adapted to each electroencephalographer would bring a close automatic EEG interpretation to that done by the electroencephalographer's visual interpretation. The adaptable automatic EEG interpretation was accomplished by using the constructive neural network with forgetting factor. The artificial neural network was constructed so as to give the integrative interpretation of the EEG based on the intermediate judgment of 13 items that characterized the visual interpretation. The developed method was evaluated based on the visually inspected EEG data of 37 patients by electroencephalographer‐A and the data of 20 patients by electroencephalographer‐B. The adapted ANN showed good agreement with each electroencephalographer's visual inspection. The proposed automatic EEG interpretation by use of the ANN can be a powerful assistant tool for individual electroencephalographers for their EEG interpretation. Copyright © 2001 John Wiley & Sons, Ltd.     

A kinetic investigation of thermally initiated emulsion copolymerization of styrene and methylmethacrylate without conventional initiators

The thermally initiated emulsion copolymerization of styrene (ST) and methyl methacrylate (MMA) was carried out in the absence of conventional initiators. The hydroperoxide (HPO) concentration in the monomers, sodium dodecyl sulfate (SDS), deionized water, and the formulation of those for emulsion copolymerization were measured. The HPO concentration in ST and MMA increased with the storage time, and were considered to be the major sources of HPO. The thermal decomposition of hydroperoxide in monomers, the thermal initiation of ST by Mayo mechanism, and the complex formation between SDS and the monomers were proposed to be three main sources of the radical generation. It was confirmed that new polymer particles were generated throughout the polymerization process, and consequently resulted in a broader distribution of polymer particle size, compared with that for conventional emulsion polymerization. Approximately 80 wt % of monomer conversion was obtained in the presence of SDS at 373 K in 24 h. The initiation rate of the 30 wt % monomer charge was faster than those of 10 wt % and 20 wt % monomer charge. The latex instability at higher solid content was improved by adding electrolyte to promote the electrostatic repulsion force between the polymer particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 455–467, 2002; DOI 10.1002/app.2343     

Uptake by macrophages of low-density lipoprotein damaged by nitrogen dioxide in air

In order to know whether nitrogen dioxide, an environmental and endogenous free radical toxin, can participate in the formation of atherosclerotic lesions, damage to low-density lipoprotein (LDL) by nitrogen dioxide and uptake of the damaged LDL by macrophages were investigated. A solution of LDL at pH 7.5 was exposed to an atmosphere of nitrogen dioxide (70 ppm) in air at 37°C for 5 or 10 h. Lipid oxidation was induced by the exposure as assessed by the formation of thiobarbituric acid reactive substances. Apolipoprotein B was covalently cross-linked via nondisulfide bonds. Fluorescence analysis showed that tryptophan residues were extensively decreased, and amino acid analysis indicated that the contents of histidine, lysine, and tyrosine residues were decreased by 30–40, 10–20, and 20–30%, respectively. Binding of LDL to thioglycolate-induced mouse peritoneal macrophages was markedly increased by the exposure as observed by the binding of mouse erythrocytes coated with LDL. The activity of LDL to convert macrophages into lipid-laden foam cells was also increased by the exposure. Modification of lysine residues of apo B with lipid oxidation products formed by the exposure may be responsible for the uptake by macrophages. The results suggest the possibility that exposure of LDLin vivo to nitrogen dioxide participates in the formation of atherosclerotic lesions.     

Experiment and numerical simulation of double-layered RC plates under impact loadings

This paper is to investigate and to propose a method to improve the impact resistance of reinforced concrete (RC) plates against projectile impact, and the damage of double-layered RC plates is examined experimentally and simulated analytically. In tests, a projectile launching apparatus, which is a 40 mm smooth-bore airgun, was used. Based on experimental results, numerical simulations with the DYNA-3D code, which takes account of the dynamic constitutive law of concrete, were done to find the applicability of the present computer code to the analysis of double-layered RC plates under high-speed impact loadings. In this study, the impact resistance of concrete plate is defined as the degree of local damage. In both experiments and numerical simulations, the effect of double-layering on the impact resistance is discussed.     

Relationship between the presence of side-holes in bone marrow aspiration needle and the number of harvested bone marrow mononuclear cells

The aim of this study was to evaluate the yield of nucleated cells in bone marrow harvested by means of Downs' Islam aspiration needles with or without side-holes. Twenty marrow donors for HLA identical sibling transplants were studied. Bone marrow nucleated cells were harvested 50 ml in the right iliac bone with a Downs' Islam aspiration needle with or without side-holes and 50 ml in the left with another kind of needle by means of 5 ml aspirations in each donor. There were no significant difference between the number of nucleated cells by means of Downs' Islam aspiration needles with and without side-holes by cross-over analysis. All nucleated cell counts were 33.06 +/- 12.93 x 10(3)/microliter (mean +/- standard deviation) by means of the needle with side-holes and 32.90 +/- 15.25 x 10(3)/microliter by means of the needle without side-holes. The Downs' Islam aspiration needle without side-holes seems to be better in bone marrow harvest from normal volunteers than that with side-holes, because the former may be stronger than the latter.     

Depth profiling study on the migration of tritium in titanium induced by deuterium-ion bombardment

A thin titanium layer with uniformly absorbed tritium (T/Ti ˜1.0) was bombarded by 390 keV D₃⁺ ions (130 keV per deuteron). Bombardment was performed at low (111 K) and room temperatures up to fluences of 5.9 × 10¹⁸ D/cm² and 3.0 × 10¹⁸ D/cm², respectively. Depth profiles of tritium up to a depth of 0.8 mg/cm² (˜1.8 μm) were measured and the change of the profile with fluence was investigated by means of the T(d, )n nuclear reaction. At both of the temperatures, a dip was formed on the depth profile of tritium at the depth around the projected range, indicating that the deuteron bombardment induced the migration of tritium against the concentration gradient. At the low temperature, the dip showed a gradual growth with fluence and saturation of the growth at the higher fluences, which could not be described by the existing model for isotope mixing. The spectrum of protons from the D(d, p)T reaction obtained in the same measurement suggested that the release of deuterium suddenly started at the final stage of the present bombardment. The dip formed at room temperature was larger than that at the low temperature. The migration of tritium induced by the bombardment is discussed on the basis of the experimental results obtained.     

Small-angle X-ray scattering of long-period structures forming bundles

Small-angle X-ray scattering (SAXS) patterns have been calculated based on a structure model, which consisted of the bundles of long-period structures. The proposed model has produced various scattering patterns of polymers, such as the equatorial, layer line, four-spot, droplet-shaped and triangular scattering. The 0.5th order scattering has arisen when the disorder in or between the long-period structures was large even though the structure did not have the periodicity directly related to the scattering maximum. A slight decrease in the disorder due to slip between the long-period structures has accounted for the sudden change of the SAXS pattern of a poly(ethylene terephthalate) fiber from the four-spot to the layer line scattering which was caused by a slight tensile deformation.     

Purification, molecular cloning, and characterization of TRP32, a novel thioredoxin-related mammalian protein of 32 kDa

We purified a protein of 32 kDa from human thymoma HPB-ALL cells that was co-purified with a catalytic fragment of MST (mammalian STE-20-like), a kinase of the STE20 family, which is proteolytically activated by caspase in apoptosis (Lee, K.-K., Murakawa, M., Nishida, E., Tsubuki, S., Kawashima, S., Sakamaki, K., and Yonehara, S. (1998) Oncogene 16, in press). Molecular cloning of the gene encoding this 32-kDa protein (TRP32) reveals that it is a novel protein of 289 amino acid residues and contains an NH2-terminal thioredoxin domain with a conserved thioredoxin active site. The human and mouse TRP32 proteins have 99% homology, and the thioredoxin domains are completely identical. The thioredoxin domain of TRP32 has thioredoxin-like reducing activity, which can reduce the interchain disulfide bridges of insulin in vitro. However, the thioredoxin domain of TRP32 is more sensitive to oxidation than human thioredoxin. Northern blot analysis showed that TRP32 is expressed in all human tissues. Expression of TRP32 was also confirmed in all mammalian cell lines tested by Western blot analysis using anti-TRP32 monoclonal antibody. Subcellular fractionation and immunostaining analysis showed TRP32 is cytoplasmic protein. These findings suggest that TRP32 is a novel cytoplasmic regulator of the redox state in higher eukaryotes.