| 11. |
- Roy, Prasun K., et al.
(författare)
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Degradable Polyethylene : Fantasy or Reality
- 2011
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 45:10, s. 4217-4227
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Forskningsöversikt (refereegranskat)abstract
- Plastic waste disposal is one of the serious environmental issues being tackled by our society today. Polyethylene, particularly in packaging films, has received criticism as it tends to accumulate over a period of time, leaving behind an undesirable visual footprint. Degradable polyethylene, which would enter the eco-cycle harmlessly through biodegradation would be a desirable solution to this problem. However, the "degradable polyethylene" which is presently being promoted as an environmentally friendly alternative to the nondegradable counterpart, does not seem to meet this criterion. This article reviews the state of the art on the aspect of degradability of polyethylene containing pro-oxidants, and more importantly the effect these polymers could have on the environment in the long run. On exposure to heat, light, and oxygen, these polymers disintegrate into small fragments, thereby reducing or increasing the visual presence. However, these fragments can remain in the environment for prolonged time periods. This article also outlines important questions, particularly in terms of time scale of complete degradation, environmental fate of the polymer residues, and possible accumulation of toxins, the answers to which need to be established prior to accepting these polymers as environmentally benign alternatives to their nondegradable equivalents. It appears from the existing literature that our search for biodegradable polyethylene has not yet been realized.
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| 12. |
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| 13. |
- Srivastava, Rajiv, et al.
(författare)
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Chemo-enzymatic synthesis of comb polymers
- 2007
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 43:3, s. 808-817
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes the synthesis and characterization of comb polymers by a two-step chemo-enzymatic process. In the first step macromonomers bearing unsaturation at the chain end were prepared by lipase catalyzed ring-opening polymerization (ROP) of E-caprolactone (CL) and 1,5-dioxepane-2-one (DXO). The ROP was carried out in bulk at 60 degrees C under anhydrous conditions using 2-hydroxyethyl methacrylate (HEMA) as the initiator. The DP of the macromonomers was controlled by regulating the monomer: HEMA molar feed concentration. The macromonomers were then homo- or co-polymerized in the second step with alkyl methacrylate monomers (methyl methacrylate or HEMA) using AIBN initiated free radical polymerization. Characterization of the polymers was done by H-1 NMR, SEC and DSC techniques.
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| 14. |
- Ahlmen, M, et al.
(författare)
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Influence of gender on assessments of disease activity and function in early rheumatoid arthritis in relation to radiographic joint damage
- 2010
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Ingår i: Annals of the rheumatic diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 69:1, s. 230-233
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate gender differences in score on 28-joint Disease Activity Score (DAS28), Health Assessment Questionnaire (HAQ) and Signals Of Functional Impairment (SOFI) and to relate these scores to radiographic joint destruction.Methods:In all, 549 patients with early RA (62% women) from the BARFOT (for “Better Anti-Rheumatic FarmacOTherapy”) study were included. At baseline, 1, 2 and 5 years DAS28, HAQ and SOFI scoring, and radiographs of hands and feet were performed. The radiographs were scored using the van der Heijde–Sharp score.Results:In women the DAS28 was significantly higher than in men due to higher scores for general health and tender joints. Likewise, HAQ and VAS pain were rated significantly higher in women. The SOFI score was worse in men during the first 2 years, depending on higher upper limb scores. Total Sharp score (TotSharp), erosion score and joint space narrowing score did not differ between the sexes at any time point. The DAS28 area under the curve (AUC) correlated significantly with TotSharp at 5 years in both genders (r = 0.316, r = 0.313) mainly owing to swollen joints and erythrocyte sedimentation rate (ESR). The SOFI AUC correlated significantly with TotSharp in women (r = 0.135 to 0.220) but not in men.Conclusions:Despite a similar degree of radiographic joint destruction women had, compared with men, worse scores for DAS28 and HAQ, possibly due to higher pain perception and less muscular strength and perhaps because men overestimate their functional capacity.
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| 15. |
- Albertsson, Ann-Christine, et al.
(författare)
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Controlled ring-opening polymerization of lactones and lactides
- 2000
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Ingår i: Macromolecular Symposia. - 1022-1360 .- 1521-3900. ; 157, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- 1,5-dioxepan-2-one (DXO) is presented as a versatile component in biodegradable polymers for biomedical applications. Copolymerization of DXO and L-lactide yielded a semi-crystalline, yet flexible, material where the extent of crystallinity and erosion characteristics were controlled by an appropriate choice of copolymer composition. Crosslinked PDXO was polymerized as a novel biodegradable elastomer. The degradation behavior of these materials were explored in vitro. Microspheres from poly(DXO-co-L-LA) were prepared and shown to be promising candidates for controlled release. The polymer composition and drug solubility provided effective means of controlling the drug delivery pattern.
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| 16. |
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| 17. |
- Albertsson, Ann-Christine, 1945-, et al.
(författare)
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Polyesters from Large Lactones
- 2009. - 1
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Ingår i: Handbook of Ring-Opening Polymerization. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 9783527319534 ; , s. 287-306
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Albertsson, Ann-Christine, et al.
(författare)
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Recent developments in enzyme-catalyzed ring-opening polymerization
- 2008
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Ingår i: Advanced Drug Delivery Reviews. - : Elsevier BV. - 0169-409X .- 1872-8294. ; 60:9, s. 1077-1093
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Forskningsöversikt (refereegranskat)abstract
- An exponential growth has been observed in the last decade where enzymes were used as catalysts for polymerization of different monomers and due to enzyme's origin from natural sources they have been taken as a substitute for the metal-based catalytic systems. Mild polymerization conditions, high enantio- and regio-selectivity and recyclability of enzymes give them an extra edge over the use of organo-metallic catallysts. Though the enzyme-catalyzed polymerizations are environmentally highly advantageous, the high cost, large quantity of enzymes required for polymerization and formation of relatively low molecular weight polymers obstruct their employment in the industry. Due to these reasons, this technique is still at die stage of infancy to generate polymeric materials which can be converted to any useful physical form. In this article enzyme-catalyzed ring-opening polymerization of lactones, lactides, cyclic carbonates and depsipeptides has been reviewed with special focus on the molecular weight of the polymers synthesized hitherto using enzyme catalysis. It is necessary to obtain polymers of sufficient molecular weight from enzyme catalysis to withstand the specific requirements of their end applications if this technique is desired to be escalated to commercial level.
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| 19. |
- Albertsson, Ann-Christine, et al.
(författare)
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Recent developments in ring opening polymerization of lactones for biomedical applications
- 2003
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 4:6, s. 1466-1486
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Forskningsöversikt (refereegranskat)abstract
- Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbabale devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field. The effect of structure on properties and degradation has been discussed. The applications of these polymers in the biomedical field are described in detail.
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| 20. |
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