Volatile products and new polymer structures formed on Co-60 gamma-radiolysis of poly(lactic acid) and poly(glycolic acid)

A gas product analysis has been conducted on gamma-irradiated samples of poly(lactic acid) (PLA) and poly(glycolic acid) (PGA) by means of gas chromatography. The major volatile products have been identified to be CO, CO2, CH4 and C2H6 for PLA, and CO and CO2 for PGA. In addition, the yield of evolved gases for PLA has been found to be 1.81 for CO2, 0.98 for CO, 0.026 for CH4 and 0.012 for C2H6; and that for PGA to be 1.70 for CO2 and 0.42 for CO. The new chain ends formed due to gamma-induced bond cleavage in PLA have been assigned to CH3-CH2-CO-O- and CH3-CH2-O-CO-, and the G values for formation of these chain ends were found to be 1.9 and 0.6, respectively. The G value for chain scission reported previously of 2.3 is comparable with that for the formation of the propanoic acid end group. (C) 1997 Elsevier Science Limited

An ESR study of the radiolysis of semi-crystalline ethylene-propylene copolymers containing DOP mobilizer

The radiolysis of a poly(ethylene-co-propylene), Elpro, marketed by Thai Polypropylene Co. Ltd for the manufacture of medical goods has been investigated at 77 K. Calcium stearate was blended with the Elpro as a processing aid; and dioctyl phthalate, DOP, was added in various amounts as a radiation stabilizer. The ESR spectra of Elpro and Elpro+Ca were very similar and characterized principally by the presence of PP a-carbon radicals. The spectra of the samples containing DOP were similar to those for Elpro but with an additional narrow singlet arising from DOP radicals. On annealing the irradiated polymers to higher temperatures, the singlet was lost between 250 and 270 K, and at room temperature the principal radicals remaining were allyl radicals. The G-values for radical formation at 77 K for Elpro and Elpro+Ca at 77 K were 3.0 and 3.2, respectively, but incorporation of DOP resulted in lower G-values, ranging from 1.6 to 1.4 for 0.5 and 2.5 phr DOP, respectively.(c) 2005 Wiley Periodicals, Inc

Revealing the Key Proteins under Telecommunications’ Tower in Brain Tissue of Rats through Proteomics Approach: Biological effects of ELF/EMF on Brain’s tissue

Introduction: Although there are a lot of interests in telecommunications tower approaches in view of Cancer, limited researches have studied the molecular pathways, which are enriched under ELF/EMF. The aim of this study is investigating the key proteins, affected by by Tower. Materials and Methods: In this study, 30 Rats under wavelength electromagnetic waves (RF900 MHz) were randomly selected. Two-dimensional electrophorese was performed to study proteomics of Rat’s brain. Results: Totally, 26 differentially uttered proteins (DEPs) were categorized by cytoscape network analysis. Conclusion: Some key proteins in view of cancer are regulated under the face of a non-standard (unconventional) radio frequency radiation, which can induce the complement and coagulation cascades pathway. &nbsp

An electron spin resonance study on γ-irradiated poly(l-lactic acid) and poly(d,l-lactic acid)

The effect of gamma irradiation on poly(l-lactic acid) (l-PLA) and poly(d,l-lactic acid) (d,l-PLA), has been examined using ESR spectroscopy and through analysis of the changes in molecular weight. The G values for radical formation of both polylactic acids have been calculated at 77 and 300 K; G(R) = 2.0 at 77 K and G(R) = 1.5 at 300 K for l-PLA and G(R) = 2.4 at 77 K and G(R) = 1.2 at 300 K for d,l-PLA. The ESR spectrum at 300 K for the polymers was assigned to one radical, resulting from H atom abstraction from the quaternary carbon atom. The G values for crosslinking and scission have also been determined for the polymers at 300 K; G(S) = 2.3 and G(X) = 0.0 for d,l-PLA, G(S) = 2.4 and G(X) = 0.28 for l-PLA