Photodegradation of polymer materials containing flame-cut agents

Photodegradation of incombustible materials [polystyrene (PSt) and polypropyrene (PP) containing 2 wt% of decabromodiphenyl oxide (DBDE) or tetrabromobisphenol-A (TBA) as a flame-cut agent] were studied using 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, UV-visible spectra and FTIR spectra were measured to identify the chemical structural changes of the polymers. Number of chain scissions, which is a measure of the polymer degradation, was estimated from the results of GPC measurements. It was found that the photostability of PP and PSt was reduced by the addition of DBDE or TBA. Photodegradation of these polymers took place by the irradiation of the light of wavelengths lower than 320 and 360 nm for the polymers containing TBA and DBDE, respectively. The most effective irradiation wavelengths for main chain scission are found to be 260–280 and 300 nm for PP or PSt–TBA samples and PP or PSt–DBDE samples, respectively. © 1993 John Wiley & Sons, Inc.     

Production of platelet-activating factor by human normodense and hypodense eosinophils

Normodense eosinophils and neutrophils from normal donors produced considerable amounts of plateletactivating factor (PAF) when stimulated with ionophore A23187. PAF produced by eosinophils appeared to be degraded more rapidly than PAF formed by neutrophils, suggesting a higher activity of PAF-degrading enzyme in eosinophils. Substantial proportions of PAF newly formed by both eosinophils and neutrophils were shown to be cell-associated. By comparison, hypodense eosinophils obtained from a patient with idiopathic hypereosinophilic syndrome produced an extremely large amount of PAF and released much of it into the incubation medium. The accelerated formation of PAF in hypodense eosinophils may be related to various cardiovascular complications associated with hypereosinophilic syndrome. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Photoresponsive peptide and polypeptide systems: Part 9. Synthesis and reversible photochromism of azo aromatic poly(L-α,ω-diaminobutyric acid)

Poly(L-α,ω-diaminobutyric acid) having azo aromatic side chains was synthesized by the water-soluble carbodiimide procedure. The photoresponsive properties of the polypeptide poly[N⁷-p-(phenylazo)benzoyl-L -α,ω-diaminobutyric acid] (PPABLDBA) due to the trans (about 71%, under visible light) cis (under ultraviolet light) photoisomerization of the azo aromatic moieties in the side chains were investigated by absorption and circular dichroism spectroscopy in hexafluoro-2-propanol (HFIP). The starting slightly turbid solution of trans-PPABLDBA becomes clear on irradiation at 360 nm, accompanied by photoconversion of the conformer of the azo moieties to cis. The backbone conformation of PPABLDBA in HFIP is right-handed helical (helical content, about 60%) when the azo moieties are trans (71%), while the conformation is random coil when cis. The backbone conformational transition of PPABLDBA from helical to coil is mostly reversible under the influence of light.     

Stoichiometry of sulphuric acid sorption by nylon 6

Sorption of sulphuric acid by Nylon 6 has been investigated. The results have been interpreted by considering the two-step dissociation of sulphuric acid in aqueous solution. Sorption occurs predominantly in the 2H⁺ + SO^2?₄ mode, but the contribution of the H⁺ + HSO^?₄ mode becomes considerable at higher concentrations. Standard affinities for both modes have been estimated.     

Improved Bonding of Partially Osteomyelitic Bone to Titanium Pins Owing to Biomimetic Coating of Apatite

Increased fixation strength of the bone-pin interface is important for inhibiting pin loosening after external fixation. In a previous study, an apatite (Ap) layer was formed on anodically oxidized titanium (Ti) pins by immersing them in an infusion fluid-based supersaturated calcium phosphate solution at 37 °C for 48 h. In the present study, an Ap layer was also successfully formed using a one-step method at 25 °C for 48 h in an infusion fluid-based supersaturated calcium phosphate solution, which is clinically useful due to the immersion temperature. After percutaneous implantation in a proximal tibial metaphysis for four weeks in rabbits (n = 20), the Ti pin coated with the Ap layer showed significantly increased extraction torque compared with that of an uncoated Ti screw even with partial osteomyelitis present, owing to dense bone formation on the Ap layer in the cortical and medullary cavity regions. When the infection status was changed from “no osteomyelitis” to “partial osteomyelitis,” the extraction torque in the Ap group with “partial osteomyelitis” was almost identical to that for “no osteomyelitis” cases. These results suggest that the Ap layer formed by the room temperature process could effectively improve the fixation strength of the Ti pin for external fixation clinically even with partial osteomyelitis present.     

The Calcium Phosphate Matrix of FGF-2-Apatite Composite Layers Contributes to Their Biological Effects

The purpose of the present study was to fabricate fibroblast growth factor (FGF)-2-apatite composite layers on titanium (Ti) pins in one step at 25 °C using a supersaturated calcium phosphate (CaP) solution, and to evaluate the physicochemical characteristics and biological effects of the coated Ti pins compared with coated Ti pins fabricated at 37 °C. Ti pins were immersed in a supersaturated CaP solution containing 0.5, 1.0, or 2.0 µg/mL FGF-2 at 25 °C for 24 h (25F0.5, 25F1.0, and 25F2.0) or containing 4.0 µg/mL FGF-2 at 37 °C for 48 h (37F4.0). Except for the 25F0.5, the chemical compositions and the mitogenic activity levels of FGF-2 of the composite layers formed by these two methods were similar, except for the Ca/P molar ratio, which was markedly smaller at 25 °C (1.55–1.56 ± 0.01–0.02, p = 0.0008–0.0045) than at 37 °C (1.67 ± 0.11). Thus, either the apatite was less mature or the amount of amorphous calcium phosphate was higher in the composite layer formed at 25 °C. In vivo, the pin tract infection rate by visual inspection for 37F4.0 (45%) was lower than that for 25F1.0 (80%, p = 0.0213), and the rate of osteomyelitis for 37F4.0 (35%) was lower than that for 25F0.5 (75%, p = 0.0341). The extraction torque for 37F4.0 (0.276 ± 0.117 Nm) was higher than that for 25F0.5 (0.192 ± 0.117 Nm, p = 0.0142) and that for 25F1.0 (0.176 ± 0.133 Nm, p = 0.0079). The invasion rate of S. aureus for 37F4.0 (35%) was lower than that for 25F0.5 (75%, p = 0.0110). On the whole, the FGF-2-apatite composite layer formed at 25 °C tended to be less effective at improving fixation strength in the bone-pin interface and resisting pin tract infections. These results suggest that the chemistry of the calcium phosphate matrix that embeds FGF-2, in addition to FGF-2 content and activity, has a significant impact on composite infection resistance and fixation strength.     

Distribution of macrolides, sulfonamides, and trimethoprim in tropical waters: ubiquitous occurrence of veterinary antibiotics in the Mekong Delta

We investigated the distributions of 12 antibiotics (viz., sulfonamides, macrolides, and trimethoprim) in the water from the Mekong Delta, Vietnam, and compared them with those in the Tamagawa River, Japan. In Vietnam, only a few antibiotics (viz., sulfamethoxazole, sulfamethazine, trimethoprim, and erythromycin-H2O) were detected in the river and canals from urban and rural sites, at concentrations of 7-360 ng/L. This contrasts with the results from the Japanese urban river, where more antibiotics (sulfamethoxazole, sulfapyridine, trimethoprim, erythromycin-H20, azithromycin, clarithromycin, and roxithromycin) were detected at concentrations ranging from 4to 448 ng/L. The concentrations of sulfonamides in the Mekong Delta were comparable to those in the Tamagawa River, whereas macrolide concentrations were lowerthanthose in the Tamagawa River. The ubiquitous occurrence of sulfamethazine, used as a veterinary medicine, in the waters in Vietnam at relatively high concentrations (15-328 ng/L) was unique. Extremely high concentrations of sulfamethazine [(18.5-19.2) x 10(3) ng/L] were detected in pig farm wastewaters, and relatively high concentrations were observed in canals near chicken and pig farms. All these data suggested the potential utility of sulfamethazine as a molecular marker of livestock-source contamination. The present study demonstrated widespread inputs of veterinary medicines to waters in Vietnam.