Repositório Institucional da Universidade de Aveiro
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Synthesis and assembly of SiO2-coated Bi2S3 nanofibers
No full textThe SiO2 coating of Bi2S3 nanofibers using the alkaline hydrolysis of Si(OEt)4 is reported. A comparative study on the optical and
morphological properties of the starting Bi2S3 nanofibers and the final SiO2 coated nanomaterials are presented and discussed. A SiO2 cap
covering homogeneously single Bi2S3 nanofibers was obtained when the hydrolysis of Si(OEt)4 was performed under sonication treatment to
maintain the fibers well separated during the coating process. These coated nanofibers were then used in a layer-by-layer deposition process
to produce multilayered nanostructured films.FCT - POCTI/35458/CTM/2000SMCT - BQU2001-3799Xunta de Galicia - PGIDT01PXI30106P
Synthesis of PbSe nanocrystallites using a single-source method. The X-ray crystal structure of lead (II) diethyldiselenocarbamate
No full textThe compounds PbhSe CN(C H ) j and PbhSe CN(CH )(C H )j were synthesised and characterised. The X-ray crystal structure 2 2 5 2 2 2 3 6 13 2
of PbhSe CN(C H ) j is reported. The use of these compounds as single-molecule precursors to produce PbSe by thermolysis in 2 2 5 2 2
tri-n-octylphosphine oxide was investigated. The optical and morphological properties of the PbSe particulates were analysed; strong
quantum confinement effects were observed in the optical spectra of nanodispersed PbSe in organic solvents
Comparative Myoanatomy of Cycliophoran Life Cycle Stages
No full textThe metazoan phylum Cycliophora includes small cryptic epibionts that live attached to the mouthparts of clawed lobsters. The life cycle is complex, with alternating sexual and asexual generations, and involves several sessile and free-living stages. So far, the morphological and genetic characterization of cycliophorans has been unable to clarify the phylogenetic position of the phylum. In this study, we add new details on the muscular anatomy of the feeding stage, the attached Prometheus larva, the dwarf male, and the female of one of the two hitherto described species, Symbion pandora. The musculature of the feeding stage is composed of myofibers that run longitudinally in the buccal funnel (two fibers) and in the trunk (variable number of fibers). The mouth opening is lined by a myoepithelial ring musculature. A complex myoepithelial sphincter is situated proximal to the anus. In the attached Prometheus larva, three longitudinal sets of myofilaments run dorsally, laterally, and ventrally along the entire anterior-posterior body axis. The muscular architecture of the dwarf male is complex, especially close to the penis, in the posterior part of the body. An X-shaped muscle structure is found on the dorsal side, whereas on the ventral side, longitudinal muscles and a V-shaped muscle structure are present. These muscles are complemented by additional dorsoventral muscles. The mesodermal muscle fibers attach to the cuticle via the epidermis in all life cycle stages studied herein. The musculature of the female is similar to that of the Pandora larva of Symbion antericanus and includes dorsoventral muscles and longitudinal muscles that run in the dorsal and ventral body region. Overall, our results reveal striking similarities in the muscular arrangement of the life cycle stages of both Symbion species. J. Morphol. 271:596-611, 2010. (C) 2009 Wiley-Liss, Inc.EC FP6 MEST-CT-2005-020542 MOLMORPHDanish Research Council (FNU-272-08-056).Danish Natural Science Research Council - SNF 21-04-0047US National Science Foundation (AToL-Tree of Life EF #0531757FCT - SFRH/BD/24436/2005EU Research Exchange Programme Synthesys DK-TAF-198
Expression of synapsin and co-localization with serotonin and RFamide-like immunoreactivity in the nervous system of the chordoid larva of Symbion pandora (Cycliophora)
No full textCycliophora is one of the most recently described metazoan phyla and hitherto includes only two species: Symbion pandora and Symbion americanus. With a very complex life cycle, cycliophorans are regarded as an enigmatic group with an uncertain phylogenetic position, although they are commonly considered lophotrochozoan protostomes. In order to extend the database concerning the distribution of immunoreactive substances in the free-swimming chordoid larva of S. pandora, we investigated synapsin immunoreactivity using fluorescence-coupled antibodies in combination with confocal laserscanning microscopy. Moreover, we analyzed the co-localization patterns of synapsin, serotonin, and RFamide-like immunoreactivity in the chordoid larva by 3D imaging technology based on the confocal microscopy image stacks. Synapsin is expressed in large parts of the bilobed anterior cerebral ganglion including anterior and dorsal projections. Two pairs of ventral neurites run longitudinally into the larval body of which the inner pair shows only weak, scattered synapsin immunoreactivity. In addition, a lateral synapsin immunoreactive projection emerges posteriorly from each ventral longitudinal axon. Double immunostaining shows co-localization of synapsin and serotonin in the cerebral ganglion, the outer and the inner ventral neurites, and the anterior projections. Synapsin and RFamide-like immunoreactivity co-occur in the cerebral ganglion, the outer ventral neurites, and the dorsal projections. Accordingly, the cerebral ganglion and the outer ventral neurites are the only neural structures that co-express the two neurotransmitters and synapsin. The overall neuroanatomical condition of the cycliophoran chordoid larva resembles much more the situation of adult rather than larval life cycle stages of a number of spiralian taxa
A new deep-sea genus of nannastacidae (Crustacea, cumacea) from the lucky strike hydrothermal vent field (Azores triple junction, mid-atlantic ridge)
No full textA new cumacean genus and species, Thalycrocuma sarradini gen. et sp. nov., belonging to the family Nannastacidae is described from several sites of the Lucky Strike hydrothermal vent field (Mid-Atlantic Ridge, 37N, 1700 m depth). The new genus differs from others in the family by males lacking exopods on the pereopods 3 and 4 and having an antenna with a five-articulate peduncle and a short flagellum. This is the first cumacean species that could be considered, at the moment, as endemic from hydrothermal vent areas. Data on the accompanying fauna including other cumacean species (Cyclaspis longicaudata, Bathycuma brevirostre, Procampylaspis sp. and Makrokylindrus sp.) and some ecological remarks are included. A key for the currently known genera of the family Nannastacidae is provided and the taxonomic position of some genera is discussed
DNA barcoding reveals cryptic diversity in marine hydroids (Cnidaria, Hydrozoa) from coastal and deep-sea environments
No full textFifty-six sequences of the mitochondrial 16S RNA gene were generated for hydroids, belonging to six nominal families - Eudendriidae, Lafoeidae, Haleciidae, Sertulariidae, Plumulariidae and Aglaopheniidae - collected from bathyal environments of the Gulf of Cadiz (22 haplotypes), Greenland (1 haplotype), Azores (1 haplotype), the shallow waters of the UK (17 haplotypes) and Portugal (2 haplotypes). When combined and analysed with 68 additional sequences published in GenBank, corresponding to 63 nominal species of these families (nine species in common between the GenBank sequences and those presented by the authors), cryptic species were detected (e.g. two species of Nemertesia and other of Lafoea), as well as apparent cases of conspecificity (e.g. Nemertesia antennina and N. perrieri and Aglaophenia octodonta, A. pluma and A. tubiformis). Other taxonomic inconsistencies were found in the data including cases where species from different genera clustered together (e.g. Sertularia cupressina, Thuiaria thuja, Abietinaria abietina and Ab. filicula). The mitochondrial 16S rRNA proved to be a useful DNA 'barcode' gene for hydroids, not only allowing discrimination of species, but also in some cases of populations, genera and families, and their intra- or interphylogenetic associations. Although still under-represented in public data bases, the 16S rRNA gene is starting to be used frequently in the study of hydroids. These data provide powerful complementary evidence for advancing our understanding of hydrozoan systematics.Training Through Research Programme IOC-UNESCOCRUP - Acções Integradas 2005 (E82-05)EC FP6 GOCE-CT-2005–511234 HERMESFCT - SFRH/BD/31155/200
A new Volterra series based orthogonal behavioral model for power amplifiers
No full textIn this paper a new Volterra Series based behavioral model for active nonlinear RF power amplifiers is presented. The proposed model's main advantage is the possibility of extraction of it's parameters orthogonally. Some validation results are presented both in the time and frequency domains, using an IS-95 CDMA signal. © 2005 IEEE
Processing and characterization of thin-films of the 2-layer superconducting phase in the bi-sr-ca-cu-o system: evidence for solid-solution
No full textThin films in the Bi-Sr-Ca-Cu-O system have been synthesized from liquid ethylhexanoate precursors by spin pyrolysis. An extensive solid-solution range was found for the two-Cu-layer phase through the study of c-axis-oriented, single-phase thin films fabricated on single-crystal, (100)-oriented, MgO substrates. All two-layer compositions were excess in Bi and deficient in Sr + Ca relative to the ideal 2212 composition and showed an overall cation deficiency. The solidus temperature and c lattice parameter were found to vary systematically with composition. Sharp superconductive transitions were obtained in the case of a number of different compositions with T(c) varying between 72 and 84 K. Evidence for significant compositional heterogeneities within single-phase two-layer thin films was found and the implications for superconductivity are discussed. Compositions within the solid-solution range gave single-phase, c-axis-oriented films over a wide temperature range extending from 730-degrees-C to an upper, solidus (or peritectic) temperature (780-degrees to 840-degrees-C) which is dependent on the initial starting composition. A model has been developed that describes the formation of the two-layer phase from a fugitive liquid.DARPA - Contract N.º N00014-88-C-071
Synthesis of flavonoid-type compounds from methyl dehydroabietates
No full textThe synthesis of new flavone-type compounds bearing several chiral centres, 12- and 14-(2'-chromonyl)dehydroabietates, are reported. This synthesis started from the aldol condensation of methyl 12- and 14-formyldehydroabietates with 2'-hydroxyacetophenones in order to prepare the corresponding chalcone-type compounds, which were then transformed in the expected flavone-type compounds by cyclodehydrogenation with DMSO and a catalytic amount of iodine. All compounds were exhaustively characterised by NMR and MS techniques.FCT/FEDER - Organic Chemistry Research UnitFCT/FEDER - PRAXIS XXI/BD/15786/9
Degree theory for operators of monotone type and nonlinear elliptic equations with inequality constraints
No full textUniversidade de AveiroFCTPOCI/MAT/55524/200