Repositório Institucional da Universidade de Aveiro
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The use of the DNA barcode gene 16S mRNA for the clarification of taxonomic problems within the family Sertulariidae (Cnidaria, Hydrozoa)
No full textMoura, C. J., Cunha, M. R., Porteiro, F. M. & Rogers, A. D. (2011). The use of the DNA barcode gene 16S mRNA for the clarification of taxonomic problems within the family Sertulariidae (Cnidaria, Hydrozoa). - Zoologica Scripta, 40, 520-537. The Sertulariidae are the most speciose family of the Hydrozoa, and their systematics are problematic. Here, 77 new 16S mtDNA sequence 'barcodes' of Atlantic and Mediterranean sertulariids were subject to phylogenetic analyses along with another 29 already deposited in Genbank. Amongst the 12 nominal genera and around 40 putative species analysed, several taxonomic inconsistencies and corroborations were highlighted by the genetic data. Patterns of morphological characters between the specimens analysed genetically were extremely congruent with molecular estimates. The genera Sertularia, Dynamena and Symplectoscyphus were found to be polyphyletic, and the genus Sertularella paraphyletic. The validity of Sertularella robusta at a species level was confirmed, along with the exclusion of Sertularelloides cylindritheca from the genus Sertularella. Potential cryptic species were detected within Sertularella fusiformis, Sertularella mediterranea, Sertularella ellisii, Sertularia distans, Dynamena disticha, Thuiaria articulata and Diphasia margareta. Conversely, probable cases of synonomy were revealed for the species pairs: Sertularia cupressina and Sertularia argentea, Amphisbetia minima and Amphisbetia operculata, and Thuiaria thuja and T. articulata. 16S haplotype data also revealed probable phylogeographic structure across localities of the NE Atlantic and Mediterranean. As an alternative 'DNA barcode', the 16S gene has the great advantage of being easily amplified and sequenced across hydrozoan taxa. Furthermore, the marked increase in deposited 16S sequences in public databases facilitates the identification of hydrozoan samples to the level of family, genus, and especially species or even populations, in a manner that is coherent with phenotypic and geographic/environmental differences.Training Through Research Programme, IOC UNESCOFCT - PTDC⁄MAR⁄ 69892 ⁄ 2006 LUSOMARBOLEC FP6 GOCE-CT-2005–511234 HERMESEC FP7 no. 226354 HERMIONEFCT - SFRH⁄BD⁄ 31155 ⁄ 200
Tanaidacean (Crustacea : Peracarida) fauna from chemically reduced habitats - the lucky strike hydrothermal vent system, mid-atlantic ridge
No full textThe tanaidacean fauna from the hydrothermal vents in the Lucky Strike Field on the Mid-Atlantic Ridge is examined. The material reveals species belonging to the genera Agathotanais, Apseudes, Leviapseudes, Sphyrapus, Armaturatanais, Leptognathiella, Mesotanais, Pseudotanais and Typhlotanais. One new typhlotanaid genus, Obesutanais, and five new species, Armaturatanais atlanticus, Obesutanais sigridae, Mesotanais styxis, Leptognathiella fragilis, and Typhlotanais incognitus, are described.KBN-000000/PO4/2005Training Through Research Program, IOC-UNESC
The linearity-efficiency compromise
No full textThe demand on telecom operators for new services and increased data rates has created difficult requirements for the signal-to-noise-and-distortion ratio of wireless systems. Furthermore, wireless spectrum has become a scarce and expensive commodity, which has led to the elimination of guard bands in the spectrum allocation. Nonlinear distortion generates both in-band and side-band distortion, which degrades the signal-to-distortion ratio of the channel and its adjacent channels. This results in the expectation of high levels of linearity from wireless circuits. On the other hand, transceiver portability, infrastructure operating costs, and global environmental issues impose a need for power management awareness for a more efficient use of supplied power.F.C.T. - PTDC/EEA-TEL/65988/2006 Digital_PAsInstituto de Telecomunicações - SWIPA Ref. Nr.: P42
A frequency domain extraction procedure of low-pass equivalent behavioural models of microwave PAs
No full textThis paper reports on a novel extraction procedure of low-pass equivalent behavioral models of microwave power amplifiers. The proposed approach is based on the use of the discrete-time Volterra Series model and on the complex envelope of a multisine as stimulus. The model extraction procedure is formulated using an alternative orthogonal model representation in the frequency domain, providing a methodology which successfully leads to an optimal model identification not affected by the ill-conditioning of typical learning methods. © 2006 EuMA.IST-1-507893-NOE - TARGE
Thermal behaviour of aluminium titanate combustion powders with MgO additions
No full textSubmicron Al2TiO5 powders produced by combustion synthesis might provide a possible solution to the known material's fabrication difficulties (microcracking and decomposition). The synthesis technique is very straightforward and the peculiar morphological characteristics of these powders suggest the possibility of producing an in-situ reinforced microstructure with improved mechanical properties. In this work, a systematic sintering/densification study carried out with pure and MgO doped Al2TiO5 powders, prepared by combustion from the corresponding metal precursor-urea mixtures, is described (MgO is a common additive used in reaction-sintered titanate ceramics to counteract the compound thermal instability). The MgO was introduced in the synthesis step and incorporated as a solid solution. The results obtained show the effects of heating rate, sintering temperature and added MgO on the thermal instability, sintering behaviour and microstructure development.FAPESP, Brazil - project 98/10017-
Microstructure, permeability and mechanical behaviour of ceramic foams
No full textThis work is part of a model study aimed at upgrading the technique of creating porosity via the incorporation of organic particles used in traditional ceramics, exploring at the same time colloidal processing from coagulated slurries. The method described in another work, based on the manipulation of short-range repulsive (lubricating) hydration force and long-range attractive van der Waals force, was used to pack to a high density a bimodal mixture of submicron ceramic particles (matrix) and much larger organic particles (inclusions) during consolidation by pressure filtration of dispersed suspensions coagulated by added electrolyte. Investigations carried out to produce strong porous ceramic bodies, with a tailored pore structure, are described. The liquid-like rheology of the saturated consolidated body produced from the coagulated suspension explains the characteristic features observed after burn-up of the organic inclusions and sintering. The porous ceramic body reflects its processing history, which can be observed in its microstructure, mechanical behavior and gas permeability.Ph.D. grant - JNICT-PortugalPost-doctoral fellowship - CNPq-Brazi
Automated high-throughput screening of carbon nanotube-based bio-nanocomposites for bone cement applications
No full textIn this work we demonstrate the potential of using an automated cell viability analyzer
for developing high-throughput screening of orthopedic bioactive materials. We used a
biomaterial of carbon nanotubes (CNTs)-based composite integrated with hydroxyapatite/
polymethyl methacrylate (HA/PMMA) with controlled physical and chemical properties to
evaluate the usefulness of morphometric analysis in conjunction with trypan blue dye exclusion
assays in MG63 cell cultures. The MG63 cell line, derived from human bone osteo -
sarcoma, is often used as a model for studying osteoblast-like cellular response to bioactive
materials for orthopedic surgery. The viability analyzer, Vi-CELLTM XR, Beckman Coulter,
was used with trypan blue dye exclusion method in cell suspensions obtained after
trypsinization along with determining the distribution plots of cell diameter and circularity,
which are critical cellular characteristics. In addition, the activity of alkaline phosphatase
(ALP), a typical representation of osteogenic activity of osteoblasts, was also measured
spectrophotometrically using p-nitrophenol phosphate as the substrate. Comparative analysis
of the frequency histogram of average cell diameter and circularity allowed for the analyses
of significant alterations in cell morphology not only over time in control cultures (spherical
vs. a flat morphology) but also with respect to PMMA and HA nanocomposites. After cell
exposure to HA/PMMA/CNTs, a shift toward loss of cell circularity was observed. The
appearances of more differentiated morphologic features were well correlated with the
increase of secreted ALP activity. In conclusion, the evaluation of material-induced changes
of cell morphology could represent a valuable prescreening test for bioactive properties.International Iberian Laboratory of Nanotechnology - NANO/NMed- AT/0115/2007FCT - Program Compromise with Science (to M.K.S. and P.M.)SFRH/BPD/14677/2003 (to V.S.S.
A Double Click Strategy Applied to the Reversible Polymerization of Furan/Vegetable Oil Monomers
No full textThis investigation describes preliminary results related to the preparation of monomers based on vegetable oil derivatives bearing furan heterocycles appended through thiol-ene click chemistry, and their subsequent polymerization via the Diels-Alder (DA) polycondensation between furan and maleimide complementary moieties, i.e. a second type of click chemistry. Following the optimization of these interactions with model compounds, two basic approaches were considered for these DA polymerizations, namely (i) the use of monomers with two terminal furan rings in conjunction with bismaleimides (AA+BB systems) and (ii) the use of AB monomers incorporating both furan and maleimide end-groups. This ongoing study clearly showed that both approaches were successful, albeit with different outcomes, in terms of the nature of the products. The application of the retro-DA reaction confirmed their thermoreversible character, i.e. the clean-cut return to their respective starting monomers.FCTPOCI 2010REEQ/515/CTM/2005SFRH/BD/44884/200
Review of kinetic models for supercritical fluid extraction
No full textThe supercritical fluid extraction (SFE) of liquids and solid materials is gaining increasing interest and commercial application in last decades, most particularly under the recent concept of green chemistry and biorefinery. Hence, it is fundamental to provide adequate modeling of the SFE, in order to optimize operating conditions and simulate the global process. This work intends to review the most significant and physically sound models published in the literature for countercurrent liquid-supercritical fluid extraction and SFE of solid matrices, such as the linear driving force, shrinking core, broken and intact cells, and the combination of BIC and shrinking core models. The main assumptions and mass transfer expressions are presented and discussed. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.FP7/2007-2013CP-IP 228589-2 AFOR
Novel bacterial cellulose-acrylic resin nanocomposites
No full textThe preparation and characterization of new nanocomposite films based on two acrylic emulsions, composed of random copolymers of butyl acrylate and methyl methacrylate, and bacterial cellulose is reported. The new composite materials were obtained through a simple and green approach by casting water-based suspensions of the acrylic emulsions and bacterial cellulose nanofibrils. The excellent compatibility between these matrices and the natural reinforcing fibers, observed by scanning electron microscopy (SEM), was reflected in the enhanced thermal and mechanical properties of the ensuing composites. Thus, an increase of around 30 degrees C in the maximum degradation temperature was observed for a 10% content of bacterial cellulose. The new composites showed glass-rubber transition temperature profiles comparable to those of the pristine matrices, as shown by DMA, and increasing elastic moduli with increasing the bacterial cellulose content. The tensile tests revealed a substantial increase in Young's modulus and tensile strength and a corresponding decrease in elongation at break with increasing bacterial cellulose load. (C) 2010 Elsevier Ltd. All rights reserved.FCTSFRH/BPD/38515/2007National Program for Scientific re-equipmentRede/1509/RME/2005REEQ/515/CTM/200