Ghislandi M.,TU Hamburg - Harburg |
Ghislandi M.,University of Aveiro |
Ghislandi M.,Center for Strategic Technologies of the Northeast |
De A. Prado L.A.S.,TU Hamburg - Harburg |
And 4 more authors.
Journal of Materials Science | Year: 2013
The effect of carbon nanofiber (CNF) functionalization on the thermo-mechanical properties of polyamide-12/CNF nanocomposites was investigated. Three main different surface treatments were performed to obtain CNF-OH (OH rich), CNF-Silane (C6H5Si-O-), and CNF-peroxide. CNF modified with poly-(tert-butyl acrylate) chains grown from the surface via ATRP (atom transfer radical polymerization) were also prepared and tested. The modified CNFs and neat CNFs were used as fillers in polyamide-12 nanocomposites and the properties of the ensuing materials were characterized and compared. Universal tensile tests demonstrated a substantial increase (up to 20 %) of the yield strength, without reduction of the final elongation, for all functionalized samples tested within 1 wt% filler content. Further evidences of mechanical properties improvement were given by dynamic mechanical thermal analyses. CNFs functionalized with poly-(tert-butyl acrylate) and silane exhibited the best performance with stiffening and strengthening at low (≤1 wt%) filler loadings, via a partial decrease of the intensity of β-transitions attributed to favorable interactions between the functional groups on the surface of functionalized CNFs and polyamide-12. CNFs treated with peroxide proved to be the most simple preparation technique and the ensuing nanocomposites exhibited the highest storage modulus at high (5 wt%) filler content. Theoretical simulations using the micro-mechanics model were used to predict the Young modulus of the composites and compare them with experimental data. The results obtained suggest a synergistic effect between the matrix and the filler enhanced by surface functionalization. © 2013 Springer Science+Business Media.
Biosynthesis of higher alcohol flavour compounds by the yeast Saccharomyces cerevisiae: Impact of oxygen availability and responses to glucose pulse in minimal growth medium with leucine as sole nitrogen source
Espinosa Vidal E.,Center for Strategic Technologies of the Northeast |
Espinosa Vidal E.,Federal University of Pernambuco |
de Morais M.A.,Federal University of Pernambuco |
Francois J.M.,National Polytechnic Institute of Toulouse |
And 5 more authors.
Yeast | Year: 2015
Higher alcohol formation by yeast is of great interest in the field of fermented beverages. Among them, medium-chain alcohols impact greatly the final flavour profile of alcoholic beverages, even at low concentrations. It is widely accepted that amino acid metabolism in yeasts directly influences higher alcohol formation, especially the catabolism of aromatic and branched-chain amino acids. However, it is not clear how the availability of oxygen and glucose metabolism influence the final higher alcohol levels in fermented beverages. Here, using an industrial Brazilian cachaça strain of Saccharomyces cerevisiae, we investigated the effect of oxygen limitation and glucose pulse on the accumulation of higher alcohol compounds in batch cultures, with glucose (20g/l) and leucine (9.8g/l) as the carbon and nitrogen sources, respectively. Fermentative metabolites and CO2/O2 balance were analysed in order to correlate the results with physiological data. Our results show that the accumulation of isoamyl alcohol by yeast is independent of oxygen availability in the medium, depending mainly on leucine, α-keto-acids and/or NADH pools. High-availability leucine experiments showed a novel and unexpected accumulation of isobutanol, active amyl alcohol and 2-phenylethanol, which could be attributed to de novo biosynthesis of valine, isoleucine and phenylalanine and subsequent outflow of these pathways. In carbon-exhausted conditions, our results also describe, for the first time, the metabolization of isoamyl alcohol, isobutanol, active amyl alcohol but not of 2-phenylethanol, by yeast strains in stationary phase, suggesting a role for these higher alcohols as carbon source for cell maintenance and/or redox homeostasis during this physiological phase. © 2014 John Wiley & Sons, Ltd.
Carvallho M.N.,Center for Strategic Technologies of the Northeast |
Carvallho M.N.,University of Pernambuco |
Da Silva K.S.,Center for Strategic Technologies of the Northeast |
Da Silva K.S.,University of Pernambuco |
And 8 more authors.
Water Science and Technology | Year: 2016
The concept of physical adsorption was applied for the removal of direct and reactive blue textile dyes from industrial effluents. Commercial graphite nanoplatelets were used as substrate, and the quality of the material was characterized by atomic force and transmission electron microscopies. Dye/graphite nanoplatelets water solutions were prepared varying their pH and initial dye concentration. Exceptionally high values (beyond 100 mg/L) for adsorptive capacity of graphite nanoplatelets could be achieved without complicated chemical modifications, and equilibrium and kinetic experiments were performed. Our findings were compared with the state of the art, and compared with theoretical models. Agreement between them was satisfactory, and allowed us to propose novel considerations describing the interactions of the dyes and the graphene planar structure. The work highlights the important role of these interactions, which can govern the mobility of the dye molecules and the amount of layers that can be stacked on the graphite nanoplatelets surface. © 2016 WA Publishing.
Barbosa J.P.F.,Center for Strategic Technologies of the Northeast |
Barbosa J.P.F.,Federal University of Pernambuco |
Ferreira A.P.A.,Center for Strategic Technologies of the Northeast |
Ferreira A.P.A.,Federal University of Pernambuco |
And 8 more authors.
Journal of Systems Architecture | Year: 2015
Hardware accelerators such as general-purpose GPUs and FPGAs have been used as an alternative to conventional CPU architectures in scientific computing applications, and have achieved good speed-up results. Within this context, the present study presents a heterogeneous architecture for high-performance computing based on CPUs and FPGAs, which efficiently explores the maximum parallelism degree for processing video segmentation using the concept of dynamic textures. The video segmentation algorithm includes processing the 3-D FFT, calculating the phase spectrum and the 2-D IFFT operation. The performance of the proposed architecture based on CPU and FPGA is compared with the reference implementation of FFTW in CPU and with the cuFFT library in GPU. The performance report of the prototyped architecture in a single Stratix IV FPGA obtained an overall speedup of 37x over the FFTW software library. © 2015 Elsevier Inc. All rights reserved.