| 531. |
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| 532. |
- Rives-Quinto, Noemi, et al.
(författare)
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Sequential activation of transcriptional repressors promotes progenitor commitment by silencing stem cell identity genes
- 2020
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Ingår i: eLIFE. - 2050-084X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Stem cells that indirectly generate differentiated cells through intermediate progenitors drives vertebrate brain evolution. Due to a lack of lineage information, how stem cell functionality, including the competency to generate intermediate progenitors, becomes extinguished during progenitor commitment remains unclear. Type II neuroblasts in fly larval brains divide asymmetrically to generate a neuroblast and a progeny that commits to an intermediate progenitor (INP) identity. We identified Tailless (Tll) as a master regulator of type II neuroblast functional identity, including the competency to generate INPs. Successive expression of transcriptional repressors functions through Hdac3 to silence tll during INP commitment. Reducing repressor activity allows re-activation of Notch in INPs to ectopically induce tll expression driving supernumerary neuroblast formation. Knocking-down hdac3 function prevents downregulation of tll during INP commitment. We propose that continual inactivation of stem cell identity genes allows intermediate progenitors to stably commit to generating diverse differentiated cells during indirect neurogenesis.
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| 533. |
- Rueda, L., et al.
(författare)
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Cellulose nanocrystals/polyurethane nanocomposites. Study from the viewpoint of microphase separated structure
- 2013
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 92:1, s. 751-757
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals (CNC) successfully obtained from microcrystalline cellulose (MCC) were dispersed in a thermoplastic polyurethane as matrix. Nanocomposites containing 1.5.5. 10 and 30 wt% CNC were prepared by solvent casting procedure and properties of the resulting films were evaluated from the viewpoint of polyurethane microphase separated structure, soft and hard domains. CNC were effectively dispersed in the segmented thermoplastic elastomeric polyurethane (STPUE) matrix due to the favorable matrix-nanocrystals interactions through hydrogen bonding. Cellulose nanocrystals interacted with both soft and hard segments, enhancing stiffness and stability versus temperature of the nanocomposites. Thermal and mechanical properties of STPUE/CNC nanocomposites have been associated to the generated morphologies investigated by AFM images.
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| 534. |
- Rueda, L., et al.
(författare)
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In situ polymerization and characterization of elastomeric polyurethane-cellulose nanocrystal nanocomposites. Cell response evaluation
- 2013
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 20:4, s. 1819-1828
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Tidskriftsartikel (refereegranskat)abstract
- Polyurethane/Cellulose nanocrystal (CNC) nanocomposites have been prepared by means of in situ polymerization using CNCs as precursors of polyurethane chains. Thermal, mechanical and morphological characterization has been analyzed to study the effect of CNC on the micro/nanostructure, which consisted of individualized nanocellulose crystallites covalently bonded to hard and soft segments of polyurethane. The incorporation of low CNC content led to a tough material whereas higher amount of CNC provoked an increase in soft and hard segments crystallization phenomenon. Moreover, from the viewpoint of polyurethane and polyurethane nanocomposites applications focused on biomedical devices, biocompatibility studies can be considered necessary to evaluate the influence of CNC on the biological behaviour. SEM micrographs obtained from cells seeded on top of the materials showed that L-929 fibroblasts massively colonized the materials surface giving rise to good substrates for cell adhesion and proliferation and useful as potential materials for biomedical applications.
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| 535. |
- Rueda, L., et al.
(författare)
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Isocyanate-rich cellulose nanocrystals and their selective insertion in elastomeric polyurethane
- 2011
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 71:16, s. 1953-1960
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals (CNC) were successfully obtained and modified with 1,6-hexamethylene diisocyanate (HE)!) by means of in situ polymerization varying the CNC/HDI molar ratio to evaluate the number of anchored chains to the CNC. The modification was examined by elemental analysis, nuclear magnetic resonance ((13)C NMR) and attenuated total reflection Fourier transform infrared spectroscopy (IR-ATR). Nanocomposites containing 1.5 wt% CNC, modified and unmodified, were prepared by solvent casting. Thermal and mechanical properties of the resulting films were evaluated from the viewpoint of polyurethane microphase separated structure, soft and hard domains. CNC were effectively dispersed in the polyurethane matrix and depending on surface chemistry, the nanoreinforcement interacts selectively with matrix nanodomains. This interpretation is supported by differences in thermal and mechanical properties of the nanocomposites and also confirmed by AFM images. Isocyanate rich cellulose nanocrystals interacted with matrix hard phase, promoting physical association with hard segments, enhancing stiffness and dimensional stability versus temperature of the nanocomposite.
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| 536. |
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| 537. |
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| 538. |
- Santana, Jordy, et al.
(författare)
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Temperature Impact on the Internal Resistance of a Polymer Electrolyte Fuel Cell Considering the Electrochemical Impedance Spectroscopy Diagnosis
- 2020. - 1
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Ingår i: Fuel Cell Seminar and Energy Exposition 2019. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607685395 ; 96:1, s. 183-190
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Konferensbidrag (refereegranskat)abstract
- A polymer electrolyte fuel cell (PEFC) is an electrochemical device that converts the chemical energy presents in the hydrogen into electricity and heat having as by product only water. The energy conversion process is carried out in a clean and noiseless manner. Depending on the applications, a PEFC works at different operating temperature. In this study, the internal resistance of a PEFC is evaluated by using Electrochemical Impedance Spectroscopy (EIS) at moderate low current density, i.e., 0.5 A/cm2, in the temperature range of 40-80°C. The evaluation is carried out considering frequencies between 3.1kHz and 1Hz. An equivalent Randle circuit is considered as adjusted model and the Nyquist and Bode diagram were obtained to analyze the internal resistance. Results show that the ohmic resistance and charge transport increase when the operating temperature is low, decreasing the cell performance. A voltage drop of 42 mV was obtained for the evaluated temperature sweep. At the same time, it was demonstrated that the double layer capacitance increases at high temperatures, increasing its operating performance.
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| 539. |
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| 540. |
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