| 1. |
- Ackermann, M., et al.
(author)
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MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE
- 2012
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In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 751:2
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Journal article (peer-reviewed)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. |
- Jonoobi, Mehdi, et al.
(author)
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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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In: 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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Journal article (peer-reviewed)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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| 3. |
- Fadel, Shaimaa M, et al.
(author)
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Improving tensile strength and moisture barrier properties of gelatin using microfibrillated cellulose
- 2013
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In: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 47:16, s. 1977-1985
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Journal article (peer-reviewed)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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| 4. |
- Goetz, Lee, et al.
(author)
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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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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:10, s. 2660-2666
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Journal article (peer-reviewed)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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| 5. |
- Hassan, Mohammad L., et al.
(author)
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Chitosan/rice straw nanofibers nanocomposites: Preparation, mechanical, and dynamic thermomechanical properties
- 2012
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In: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 125:Suppl. 2, s. E216-E222
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Journal article (peer-reviewed)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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| 6. |
- Hassan, Mohammad L., et al.
(author)
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Improving cellulose/polypropylene nanocomposites properties with chemical modified bagasse nanofibers and maleated polypropylene
- 2014
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In: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 33:1, s. 26-36
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Journal article (peer-reviewed)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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| 7. |
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| 8. |
- Mikkonen, K. S., et al.
(author)
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Glucomannan composite films with cellulose nanowhiskers
- 2010
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In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 17:1, s. 69-81
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Journal article (peer-reviewed)abstract
- Spruce galactoglucomannans (GGM) and konjac glucomannan (KGM) were mixed with cellulose nanowhiskers (CNW) to form composite films. Remarkable effects of CNW on the appearance of the films were detected when viewed with regular and polarizing optical microscopes and with a scanning electron microscope. Addition of CNW to KGM-based films induced the formation of fiberlike structures with lengths of several millimeters. In GGM-based films, rodlike structures with lengths of several tens of micrometers were formed. The degree of crystallinity of mannan in the plasticized KGM-based films increased slightly when CNW were added, from 25 to 30%. The tensile strength of the KGM-based films not containing glycerol increased with increasing CNW content from 57 to 74 MPa, but that of glycerol-plasticized KGM and GGM films was not affected. Interestingly, the notable differences in the film structure did not appear to be related to the thermal properties of the films.
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| 9. |
- Oksman, M., et al.
(author)
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Transduced Wild-Type but Not P301S Mutated Human Tau Shows Hyperphosphorylation in Transgenic Mice Overexpressing A30P Mutated Human Alpha-Synuclein
- 2013
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In: Neurodegenerative Diseases. - : S. Karger AG. - 1660-2862 .- 1660-2854. ; 12:2, s. 91-102
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Journal article (peer-reviewed)abstract
- Neuropathological and cell culture studies suggest that tau and alpha-synuclein pathologies may promote each other. To study the relevance and functional implications of these findings in vivo, we transduced hippocampal neurons of wild-type or human A30P alpha-synuclein transgenic mice with wild-type or P301S mutated human tau using an adeno-associated virus vector. Green fluorescent protein transduction was used as a control. We assessed spontaneous exploratory activity, anxiety and spatial learning and memory 11 weeks after the transduction and perfused the mice for histology. The transduced tau was mainly found in axon terminals and largely restricted within the hippocampi. In addition, neurons around the injection site showed cytoplasmic staining for human tau in both wild-type and A30P mice. Of these tau-positive neurons, 44% in A30P mice but only 3% in wild-type mice receiving human wild-type tau transduction formed paired helical filament-1 (PHF-1)-positive cytoplasmic densities. In contrast, only 1% of tau-positive neurons were also PHF-1 positive after transduction with P301S tau in mice of either genotype. Transduction of P301S tau reduced swimming speed but otherwise tau transduction had no significant behavioral consequences. Cytoplasmic PHF-1 densities were associated with poor spatial memory in wild-type mice but slightly improved memory in A30P mice, indicating that also tau hyperphosphorylation does not necessarily compromise neural functions. These data demonstrate that alpha-synuclein promotes tau hyperphosphorylation depending on the amino acids on the 301 site. Copyright (C) 2012 S. Karger AG, Basel
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| 10. |
- Sundar, Smith T., et al.
(author)
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Characterization of microcrystalline cellulose and cellulose long fiber modified by iron salt
- 2010
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 80:1, s. 35-43
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Journal article (peer-reviewed)abstract
- Microcrystalline cellulose (MCC) and cellulose long fiber (CLF) were treated with iron (Fe) based salt and the samples were characterized to study the coordination complexes formed between cellulose and iron. The Fe-modified MCC and CLF were characterized by spectroscopic, thermal and morphological methods. MCC and CLF were oxidized and further treated with iron (Fe) based salt in a high pH medium to form coordination complexes. Both MCC and CLF were then analyzed using Scanning electron microscopy (SEM) to examine their surface morphology. The results have shown that there was no major change in morphology for MCC and CLF upon modification. The functional groups formed by modifying cellulose by iron salt were investigated using FTIR-ATR spectroscopy and the nature of the coordination bonds formed between cellulose and Fe ions were examined by X-ray photo electron spectroscopy (XPS). The results agree that coordination bonds were formed between de-protonated and or oxidized hydroxyl group and Fe ions. Powder XRD (PXRD) was resourceful to compare the crystallinity of unmodified and Fe-modified samples of MCC and CLF. Thermal stability of modified cellulose was studied using thermo gravimetric analysis (TGA). The results showed that there was an increase in percentage of residual mass and higher thermal stability for the Fe-modified MCC and CLF compared to unmodified samples due to the presence of iron.
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