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Sökning: WFRF:(Venditti Richard A.)

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1.
  • Ayoub, Ali, et al. (författare)
  • Effect of plasticizers and polymer blends for processing softwood kraft lignin as carbon fiber precursors
  • 2021
  • Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 28:2, s. 1039-1053
  • Tidskriftsartikel (refereegranskat)abstract
    • Plasticizers depress the glass transition temperature (T-g) of polymers and produce a flowable material at lower temperatures. The use of plasticizers to depress T-g of lignin is important, since at high processing temperatures lignin crosslinks, making it intractable. The goal of this study was to assess plasticizers and polymer blends for the ability to retard a commercial softwood kraft lignin from crosslinking and also serve as thermal and rheological property modifiers during thermal processing in the attempt to produced moldable and spinnable lignin for lignin and carbon fiber products. The T-g of the lignin and the lignin mixed with various amounts of plasticizers and with different thermo-mechanical mixing were determined using differential scanning calorimetry. The T-g and the change in heat capacity at the glass transition (Delta C-p) decreased and increased, respectively, about linearly within this plasticizers range with increased plasticizer weight percentage. Gel permeation chromatography results for extruded lignin as well as extruded lignin-plasticizer blends with glycerol, N-allyurea, citric acid with and without sodium hypophosphite, and oleic acid indicate that the presence of these materials reduced the rate of molecular weight increase at temperatures between 100 and 200 degrees C. Continuous, homogenous films and fibers could be produced by thermal processing with plasticized lignin samples and plasticized lignin-polymer blends, but not with lignin alone. These fibers could be carbonized, yielding up to about 50% of carbon. The present findings have shown the advantages of plasticizers in thermally processing a commercial softwood kraft lignin.
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2.
  • Rockette-Wagner, Bonny, et al. (författare)
  • The impact of lifestyle intervention on sedentary time in individuals at high risk of diabetes
  • 2015
  • Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 58:6, s. 1198-1202
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims/hypothesis The Diabetes Prevention Program (DPP) lifestyle intervention successfully achieved its goal of increasing leisure physical activity levels. This current study examines whether the lifestyle intervention also changed time spent being sedentary and the impact of sedentary time on diabetes development in this cohort. Methods 3,232 DPP participants provided baseline data. Sedentary behaviour was assessed via an interviewer-administered questionnaire and reported as time spent watching television specifically (or combined with sitting at work). Mean change in sedentary time was examined using repeated measures ANCOVA. The relationship between sedentary time and diabetes incidence was determined using Cox proportional hazards models. Results During the DPP follow-up (mean: 3.2 years), sedentary time declined more in the lifestyle than the metformin or placebo participants (p < 0.05). For the lifestyle group, the decrease in reported mean television watching time (22 [95% CI 26, 17] min/day) was greater than in the metformin or placebo groups (p < 0.001). Combining all participants together, there was a significantly increased risk of developing diabetes with increased television watching (3.4% per hour spent watching television), after controlling for age, sex, treatment arm and leisure physical activity (p < 0.01), which was attenuated when time-dependent weight was added to the model. Conclusions/interpretation In the DPP, the lifestyle intervention was effective at reducing sedentary time, which was not a primary goal. In addition, in all treatment arms, individuals with lower levels of sedentary time had a lower risk of developing diabetes. Future lifestyle intervention programmes should emphasise reducing television watching and other sedentary behaviours in addition to increasing physical activity.
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