| 1. |
- Ackermann, M., et al.
(författare)
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MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 751:2
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Tidskriftsartikel (refereegranskat)abstract
- The blazarAO 0235+164 (z=0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to gamma-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the gamma-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R-g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.
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| 2. |
- Eichhorn, S. J., et al.
(författare)
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Current international research into cellulose as a functional nanomaterial for advanced applications
- 2022
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Ingår i: Journal of Materials Science. - : Springer Nature. - 0022-2461 .- 1573-4803. ; 57:10, s. 5697-5767
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Tidskriftsartikel (refereegranskat)abstract
- This review paper provides a recent overview of current international research that is being conducted into the functional properties of cellulose as a nanomaterial. A particular emphasis is placed on fundamental and applied research that is being undertaken to generate applications, which are now becoming a real prospect given the developments in the field over the last 20 years. A short introduction covers the context of the work, and definitions of the different forms of cellulose nanomaterials (CNMs) that are most widely studied. We also address the terminology used for CNMs, suggesting a standard way to classify these materials. The reviews are separated out into theme areas, namely healthcare, water purification, biocomposites, and energy. Each section contains a short review of the field within the theme and summarizes recent work being undertaken by the groups represented. Topics that are covered include cellulose nanocrystals for directed growth of tissues, bacterial cellulose in healthcare, nanocellulose for drug delivery, nanocellulose for water purification, nanocellulose for thermoplastic composites, nanocellulose for structurally colored materials, transparent wood biocomposites, supercapacitors and batteries.
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| 3. |
- Jonoobi, Mehdi, et al.
(författare)
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A comparison of modified and unmodified cellulose nanofiber reinforced polylactic acid (PLA) prepared by twin screw extrusion
- 2012
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 20:4, s. 991-997
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5 wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones.
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| 4. |
- Herrera, Natalia, et al.
(författare)
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Functionalized blown films of plasticized polylactic acid/chitin nanocomposite : Preparation and characterization
- 2016
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 92, s. 846-852
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Tidskriftsartikel (refereegranskat)abstract
- Bionanocomposite films prepared with melt compounding and film blowing were evaluated for packaging applications. The nanocomposite masterbatch with 75 wt% polylactic acid (PLA), 5 wt% chitin nanocrystals (ChNCs) and 20 wt% glycerol triacetate plasticizer (GTA) was melt compounded and then diluted to 1 wt% ChNCs with PLA and polybutylene adipate-co-terephthalate (PBAT) prior to film blowing. The morphological, mechanical, optical, thermal and barrier properties of the blown nanocomposite films were studied and compared with the reference material without ChNCs. The addition of 1 wt% ChNCs increased the tear strength by 175% and the puncture strength by 300%. Additionally, the small amount of chitin nanocrystals affected the glass transition temperature (Tg), which increased 4 °C compared with the reference material and slightly enhanced the films degree of crystallinity. The chitin nanocomposite also had lower fungal activity and lower electrostatic attraction between the film surfaces; leading to easy opening of the plastic bags. The barrier and optical properties as well as the thermal degradation of the films were not significantly influenced by the addition of chitin nanocrystals.
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| 5. |
- Semeniuk, M., et al.
(författare)
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Design and fabrication of low-cost renewable carbon electrode materials and their thermo-kinetics for sustainable energy storage applications
- 2022
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Ingår i: Materials Today Sustainability. - : Elsevier. - 2589-2347. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- To date, there have been few studies performed on the kinetics of thermal decomposition of renewable carbon and its use in energy storage devices. Novel renewable graphitic carbon from Acer saccharum, sugar maple (SM) heartwood, and Arachis hypogaea, peanut outer shell (PS), are used as anodes in lithium-ion coin cell batteries, with steady specific capacities of 180 mAh/g and 220 mAh/g, respectively, and both retain 100% columbic efficiency for over 350 cycles. Cyclic voltammetry reveals the different charge storage kinetic mechanisms of the two. The voltammogram of SM contains an oxidation peak indicating Li ion intercalation suitable for battery application, while PS lacks a peak; thus, showing potential for function as a supercapacitor. A kinetic study is undertaken on six carbon sources to improve the understanding of the thermal degradation process leading to renewable graphitic carbon. Consistent results are shown across the various model-free methods, indicating that they can accurately describe the devolatilization process. The renewable graphitic carbons morphological features were studied by SEM, XRD, Raman and nitrogen adsorption isotherms. As SM and PS compare favorably to the electrodes they replace, renewable graphitic carbon has the potential for use in a wide variety of novel applications, such as organic thin film transistors, fuel cells, organic batteries, supercapacitors, and other bioelectronics.
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| 6. |
- Esmaeili, Chakavak, et al.
(författare)
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Synergy Effect of Nanocrystalline Cellulose for the Biosensing Detection of Glucose
- 2015
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 15:10, s. 24681-24697
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Tidskriftsartikel (refereegranskat)abstract
- Integrating polypyrrole-cellulose nanocrystal-based composites with glucose oxidase (GOx) as a new sensing regime was investigated. Polypyrrole-cellulose nanocrystal (PPy-CNC)-based composite as a novel immobilization membrane with unique physicochemical properties was found to enhance biosensor performance. Field emission scanning electron microscopy (FESEM) images showed that fibers were nanosized and porous, which is appropriate for accommodating enzymes and increasing electron transfer kinetics. The voltammetric results showed that the native structure and biocatalytic activity of GOx immobilized on the PPy-CNC nanocomposite remained and exhibited a high sensitivity (ca. 0.73 μA·mM(-1)), with a high dynamic response ranging from 1.0 to 20 mM glucose. The modified glucose biosensor exhibits a limit of detection (LOD) of (50 ± 10) µM and also excludes interfering species, such as ascorbic acid, uric acid, and cholesterol, which makes this sensor suitable for glucose determination in real samples. This sensor displays an acceptable reproducibility and stability over time. The current response was maintained over 95% of the initial value after 17 days, and the current difference measurement obtained using different electrodes provided a relative standard deviation (RSD) of 4.47%.
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| 7. |
- Fadel, Shaimaa M, et al.
(författare)
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Improving tensile strength and moisture barrier properties of gelatin using microfibrillated cellulose
- 2013
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Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 47:16, s. 1977-1985
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Tidskriftsartikel (refereegranskat)abstract
- Microfibrillated cellulose isolated from bagasse was used to prepare novel nanocomposites using cross-linked gelatin as a biodegradable polymer matrix. Microfibrillated cellulose loadings up to 25% (weight percent) were used. The prepared nanocomposites were characterized regarding their wet and dry tensile strength, water sorption, and water vapor permeability. Nanocomposites’ surfaces were examined by scanning electron microscopy; the scanning electron microscopy images indicated homogeneous distribution of microfibrillated cellulose in the gelatin matrix. Microfibrillated cellulose improved wet and dry maximum tensile stress and modulus of cross-linked gelatin but resulted in a decrease of its strain at break. Microfibrillated cellulose did not affect the water absorption of cross-linked gelatin but significantly improved its moisture barrier property.
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| 8. |
- Goetz, Lee, et al.
(författare)
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Poly(methyl vinyl ether-co-maleic acid)-Polyethylene Glycol Nanocomposites Cross-Linked In Situ with Cellulose Nanowhiskers
- 2010
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:10, s. 2660-2666
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites were developed by cross-linking cellulose nanowhiskers with poly(methyl vinyl ether-co-maleic acid) and polyethylene glycol. Nuclear Magnetic resonance (NMR) studies showed cross-linking occurs between the matrix and cellulose nanowhiskers via an esterification reaction. Proton NMR 12 relaxation experiments provided information on the mobility of the polymer chains within the matrix, which can be related to the structure of the cross-linked nanocomposite: The nanocomposite was found to consist of mobile chitin portions between crosslinked junction points and immobilized chain segments near or at those junction points, whose relative fraction increased upon further incorporation of cellulose nanowhiskers. Atomic force microscopy images showed homogeneous dispersion of nanowhiskers in the matrix even at high nanowhisker content, which can he attributed to cross-linking of the nanowhiskers in the matrix. Relative humidity conditions were found to affect the mechanical properties of the composites negatively while the nanowhiskers content had a positive effect. It is expected that the cross-links between the matrix and the cellulose nanowhiskers trap the nanowhiskers in the cross-linked network, preventing nanowhisker aggregation subsequently producing cellulose nanocomposites with unique mechanical behaviors. The results show that in situ cross-linking of cellulose nanowhiskers with a matrix polymer is a promising route to obtain nanocomposites with well dispersed nanowhiskers, tailored nanostructure, and mechanical performance.
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| 9. |
- Hassan, Mohammad L., et al.
(författare)
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Chitosan/rice straw nanofibers nanocomposites: Preparation, mechanical, and dynamic thermomechanical properties
- 2012
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 125:Suppl. 2, s. E216-E222
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Tidskriftsartikel (refereegranskat)abstract
- Nanofibers were isolated from rice straw pulp using ultrahigh friction grinding and high-pressure homogenization. Chitosan nanocomposites were prepared using the isolated nanofibers at fiber loading from 2.5 to 20% by solution casting and evaporation technique. The effect of nanofiber loading on dry and wet tensile strength, dynamic mechanical thermal properties, and cyrstallinity of chitosan were studied using tensile testing, thermogravimetric analysis, dynamic mechanical thermal analysis, and X-ray diffraction. Addition of rice straw nanofibers (RSNF) to chitosan resulted in significant improvement in wet and dry tensile strength, and shift of glass transition temperature (Tg) of chitosan matrix to higher values. Chitosan nanocomposites prepared using RSNF (CRSNF) had remarkable wet and dry tensile strength, which could be attributed to presence of both nanofibers and nanosilica particles originally present in rice straw fibers. Addition of RSNF to chitosan did not affect its onset thermal degradation temperature.
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| 10. |
- Hassan, Mohammad L., et al.
(författare)
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Improving cellulose/polypropylene nanocomposites properties with chemical modified bagasse nanofibers and maleated polypropylene
- 2014
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 33:1, s. 26-36
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Tidskriftsartikel (refereegranskat)abstract
- The properties of cellulose/polypropylene (PP) nanocomposites with n-octadecyl-modified bagasse nanofibers (MBNF) were compared to those with maleated polypropylene (MAPP) coupling agent. The nanocomposites were prepared by twin-screw extrusion with bagasse nanofiber (BNF) content varying from 2.5 to 10 wt%. The compression molded nanocomposites sheets were characterized regarding their tensile strength properties, dynamic mechanical thermal properties, crystallinity, water absorption, transparency and loss of strength due to composting in soil. As a compatibilizer to improve the tensile strength properties and transparency of PP/cellulose nanofibers nanocomposites, MAPP was more effective than n-octadecyl-modified cellulose nanofibers. The crystallinity of the nanocomposites was lower than that of neat PP except for those prepared using high loading of MBNF. Dynamic mechanical thermal analysis (DMTA) of the prepared materials showed that adding the different nanofibers (treated or untreated) resulted in better mechanical thermal properties above glass transition temperature (Tg) of PP. Water absorption capability in all nanocomposites was weakened while that in PP/MBNF was the lowest. No significant differences were found between the nanocomposites with different kinds of nanofibers regarding the loss of their tensile strength after compositing in soil up to six months.
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