NMR study of the radiation-induced cross-linking of poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether)

The gamma-radiolysis of poly(tetrafluoroethylene-co-perfuoromethyl vinyl ether) (TFE/PMVE) was investigated using solid state F-19 and C-13 NMR spectroscopy. Chain scission products identified in the polymer were saturated chain ends -CF2CF3 (G = 1.0), methyl ether end groups -CF2OCF3 (G = 0.9), acid end groups -CF2COOH (G = 0.5), and a small amount of terminal unsaturation -CF=CF2 (G = 0.2). A mechanism for the formation of these scission products was proposed and the G value for main chain scission, G(S), was determined to be 1.4. Cross-linking of TFE/PMVE was found to proceed via a Y-linking mechanism. The G value for cross-linking, G(X), was determined to be 0.9. A maximum of 0.2 mol % cross-links were formed under the experimental conditions.

Effect of temperature on the gamma-radiolysis of poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether)

The effect of irradiation temperature on the polymer properties was investigated for the fluoroelastomer poly(tetrafluoroethylene-co-perfluoromethylvinyl ether) (TFE/PMVE). TFE/PMVE samples were gamma-irradiated to 150 kGy at temperatures ranging from 77 K to 373 K. Analysis of the sol/gel behaviour, tensile properties, and glass transition temperatures indicated that crosslinking commenced in the temperature range 195 to 263 K, for a dose of 150 kGy. The latter temperature was 13 K below the glass transition temperature. Crosslinking remained relatively constant to higher temperatures. Chain scission reactions were found to occur well below the glass transition temperature and increased at higher temperatures. The optimum temperature for the radiation crosslinking of TFE/PMVE, for the temperatures investigated, was 263 K. (C) 1998 Elsevier Science Ltd. All rights reserved.

Thermal and mechanical properties of radiation crosslinked poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether)

The gamma-radiolysis of poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether) (TFE/PMVE) was investigated using chemical and mechanical analyses. The polymer was found to form an insoluble network with a dose of gelation of 15.8 kGy. Tensile and glass transition temperature measurements indicated the predominance of crosslinking, with optimal elastomeric properties reached in the dose range of 120 to 200 kGy. Photoacoustic FTIR spectroscopy CPAS) showed the formation of new carboxylic acid end groups on irradiation. These new end groups were shown to decrease the thermal oxidative stability of the crosslinked network as determined by thermal gravimetric analysis. Electron spin resonance (ESR) studies of the polymer at 77 K indicated the presence of radical precursors. A G-value of 1.1 was determined for radical production at 77 K. Comparison of radical concentrations for a copolymer with a different mole ratio of PMVE, indicated that the PMVE units contribute to scission reactions. (C) 1998 Elsevier Science Ltd. All rights reserved.

An ESR study of irradiated poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA)

Poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) with 2 mol% perfluoropropyl vinyl ether (PPVE) was exposed to gamma -irradiation in vacuum at both 77 K and room temperature and the ESR spectra recorded. Both the main chain, similar to CF2-(CF)-F-.-CF(2)similar to, and end chain, similar to (CF2CF2)-F-. radicals were identified at both temperatures and their thermal stabilities measured, No radicals unique to the radiolytic cleavage at the PPVE units were observed at room temperature, either due to the low concentration of the comonomer or beta -scission to form a chain end radical and a nonradical species. G-values for radical formation at room temperature and 77 K were found to be 0.93 and 0.16, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.

Water sorption into poly[(2-hydroxyethyl methacrylate)-co-(1-vinyl-2-pyrrolidone]at 310 K

Poly(2-hydroxyethyl methacrylate) and copolymers of 2-hydroxyethyl methacrylate (HEMA) and 1-vinyl-2-pyrrolidone (VP) in the form of cylindrical samples (approximate to8mm x 20mm) have been prepared and the sorption of water into these cylinders has been studied by the mass-uptake methods and by magnetic-resonance imaging. The equilibrium water contents for the cylinders were found to vary systematically with the copolymer composition. Diffusion of water into the cylinders was found to follow Fickian behaviour for cylinders with high HEMA contents, with the diffusion coefficients obtained from mass-uptake studies dependent on the copolymer composition, varying from 1.7 x 10(-11) m(2) s(-1) for poly(HEMA) to 2.0 x 10(-11) m(2) s(-1) for poly(HEMA-co-VP) with a composition of 1:1. However, NMR-imaging studies showed that, while the profiles of the water diffusion fronts for cylinders with high HEMA contents were Fickian, that for the 1:1 copolymer was not and indicated that the mechanism was Case III. The polymers which were rich in VP were characterized by a water-sorption process which follows Case-III behaviour. (C) 2003 Society of Chemical Industry.

Metabolic and kinetic analysis of poly(3-hydroxybutyrate) production by recombinant Escherichia coli

A quantitatively repeatable protocol was developed for poly(3-hydroxybutyrate) (PHB) production by Escherichia coli XL1-Blue (pSYL107). Two constant-glucose fed-batch fermentations of duration 25 h were carried out in a 5-L bioreactor, with the measured oxygen volumetric mass-transfer coefficient (k(L)a) held constant at 1.1 min(-1). All major consumption and production rates were quantified. The intracellular concentration profiles of acetyl-CoA (300 to 600 mug.g RCM-1) and 3-hydroxy-butyryl-CoA (20 to 40 mug.g RCM-1) were measured, which is the first time this has been performed for E. coli during PHB production. The kinetics of PHB production were examined and likely ranges were established for polyhydroxyalkanoate (PHA) enzyme activity and the concentration of pathway metabolites. These measured and estimated values are quite similar to the available literature estimates for the native PHB producer Ralstonia eutropha. Metabolic control analysis performed on the PHB metabolic pathway showed that the PHB flux was highly sensitive to acetyl-CoA/CoA ratio (response coefficient 0.8), total acetyl-CoA + CoA concentration (response coefficient 0.7), and pH (response coefficient -1.25). It was less sensitive (response coefficient 0.25) to NADPH/NADP ratio. NADP(H) concentration (NADPH + NADP) had a negligible effect. No single enzyme had a dominant flux control coefficient under the experimental conditions examined (0.6, 0.25, and 0.15 for 3-ketoacyl-CoA reductase, PHA synthase, and 3-ketothiolase, respectively). In conjunction with metabolic flux analysis, kinetic analysis was used to provide a metabolic explanation for the observed fermentation profile. In particular, the rapid onset of PHB production was shown to be caused by oxygen limitation, which initiated a cascade of secondary metabolic events, including cessation of TCA cycle flux and an increase in acetyl-CoA/CoA ratio. (C) 2001 John Wiley & Sons. Inc. Biotechnol Bioeng 74: 70-80, 2001.

Copolymers obtained by the radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) substrates. 1. Preparation and structural investigation

A study has been made to investigate the radiation grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA) substrates, using the simultaneous irradiation method. Two PFA polymers of different comonomer perfluoropropyl vinyl ether (PPVE) content and degree of crystallinity were used. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the six different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The grafting of styrene onto the PFA substrates was confirmed by FTIR-ATR and micro-Raman spectroscopy, The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate.

Comparative study of the radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) and polypropylene substrates. I: Kinetics and structural investigation

A comparative study has been made of the radiation grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) and polypropylene (PP) substrates, using the simultaneous irradiation method. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate and irradiation dose on the grafting yield were investigated. Under the same grafting conditions it was found that a higher degree of grafting of styrene was obtained using a mixture of dichloromethane/methanol solvents for PFA and methanol for PP and the degree of grafting was higher in PP than in PFA at all doses. However, the micro-Raman spectroscopy analysis of the graft revealed that, for the same degree of grafting, the penetration depth of the grafted polystyrene into the substrate was higher in PFA than in PP substrates. In both polymers the crystallinity was hardly affected by the grafting process and the degree of crystallinity decreased slightly with grafting dose. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be 0.6 and 1.4 order for PFA and 0.15 and 2.2 for PP, respectively. The degree of grafting increased with increasing radiation dose in both polymers. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield for PFA and PP was accompanied by a proportional increase in the penetration depth of the graft into the substrates. (C) 2003 Society of Chemical Industry.

Polymeric grafting of acrylic acid onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Surface functionalization for tissue engineering applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt processed disks and solvent cast films were modified by graft co-polyinerization with acrylic acid (AAc) in methanol solution at ambient temperature using gamma irradiation (dose rate of 4.5 kGy/h). To assess the presence of carboxylic acid groups on the surface, reaction with pentafluorophenol was performed prior to X-ray photoelectron spectroscopy analysis. The grafting yield for all samples increased with monomer concentration (2-15%), and for the solvent cast films, it also increased with dose (2-9 kGy). However, the grafting yield of the melt processed disks was largely independent of the radiation dose (2-8 kGy). Toluidine blue was used to stain the modified materials facilitating, visual information about the extent of carboxylic acid functionalization and depth penetration of the grafted copolymer. Covalent linking of glucosamine to the functionalized surface was achieved using carbodimide chemistry verifying that the modified substrates are suitable for biomolecule attachment.

Alcohol use and risk taking among regular ecstasy users

We examine alcohol use in conjunction with ecstasy use and risk-taking behaviors among regular ecstasy users in every capital city in Australia. Data on drug use and risks were collected in 2004 from a national sample of 852 regular ecstasy users (persons who had used ecstasy at least monthly in the preceding 6 months). Users were grouped according to their typical alcohol use when using ecstasy: no use, consumption of between one and five standard drinks, and consumption of more than five drinks (binge alcohol use). The sample was young, well educated, and mainly working or studying. Approximately two thirds (65%) of the regular ecstasy users reported drinking alcohol when taking ecstasy. Of these, 69% reported usually consuming more than five standard drinks. Those who did not drink alcohol were more disadvantaged, with greater levels of unemployment, less education, higher rates of drug user treatment, and prison history. They were also more likely than those who drank alcohol when using ecstasy to be drug injectors and to be hepatitis C positive. Excluding alcohol, drug use patterns were similar between groups, although the no alcohol group used cannabis and methamphetamine more frequently. Binge drinkers were more likely to report having had three or more sexual partners in the past 6 months and were less likely to report having safe sex with casual partners while under the influence of drugs. Despite some evidence that the no alcohol group were more entrenched drug users, those who typically drank alcohol when taking ecstasy were as likely to report risks and problems associated with their drug use. It appears that regular ecstasy users who binge drink are placing themselves at increased sexual risk when under the influence of drugs. Safe sex messages should address the sexual risk associated with substance use and should be tailored to reducing alcohol consumption, particularly targeting heavy alcohol users. The study's limitations are noted.

Differential patterns of Male and Female mtDNA exchange across the Atlantic Ocean in the blue mussel, Mytilus edulis

Comparisons among loci with differing modes of inheritance can reveal unexpected aspects of population history. We employ a multilocus approach to ask whether two types of independently assorting mitochondrial DNAs (maternally and paternally inherited: F- and M-mtDNA) and a nuclear locus (ITS) yield concordant estimates of gene flow and population divergence. The blue mussel, Mytilus edulis, is distributed on both North American and European coastlines and these populations are separated by the waters of the Atlantic Ocean. Gene flow across the Atlantic Ocean differs among loci, with F-mtDNA and ITS showing an imprint of some genetic interchange and M-mtDNA showing no evidence for gene flow. Gene flow of F-mtDNA and ITS causes trans-Atlantic population divergence times to be greatly underestimated for these loci, although a single trans-Atlantic population divergence time (1.2 MYA) can be accommodated by considering all three loci in combination in a coalescent framework. The apparent lack of gene flow for M-mtDNA is not readily explained by different dispersal capacities of male and female mussels. A genetic barrier to M-mtDNA exchange between North American and European mussel populations is likely to explain the observed pattern, perhaps associated with the double uniparental system of mitochondrial DNA inheritance.

Review of diagnostic screening instruments for alcohol and other drug use and other psychiatric disorders

In recent years there has been a growing recognition that many people with drug or alcohol problems are also experiencing a range of other psychiatric and psychological problems. The presence of concurrent psychiatric or psychological problems is likely to impact on the success of treatment services. These problems vary greatly, from undetected major psychiatric illnesses that meet internationally accepted diagnostic criteria such as those outlined in the Diagnostic and Statistical Manual (DSM-IV) of the American Psychiatric Association (1994), to less defined feelings of low mood and anxiety that do not meet diagnostic criteria but nevertheless impact on an individual’s sense of wellbeing and affect their quality of life.

Acid-mediated conversion of methylene-interrupted bisepoxides to tetrahydrofurans: A biomimetic transformation

The acid-mediated transformation of syn and anti methylene interrupted cis,cis and cis,trans bisepoxides to tetrahydrofurans is high yielding, and demonstrates both regioselectivity and stereoselectivity. Trans,trans methylene interrupted bisepoxides do not yield tetrahydrofurans under the same conditions.

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.

A novel tricopper(II) complex of a polyamine alcohol

The trinuclear copper(II) complex of a new polyamino alcohol ligand has been isolated; it exhibits a structure similar to that found at the active site of ascorbate oxidase.