Browsing by Issue Date, starting with "2004-09"
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- An iterative frequency-domain decision feedback receiver for CDMA systemsPublication . Silva, Paulo; Dinis, RuiUnless high-complexity receiver structures are employed, conventional DS-CDMA (direct sequence code division multiple access) schemes can have a poor performance in severe time-dispersive channels, since the orthogonality between the users is lost. In this paper, we propose an iterative frequency-domain decision feedback equalizer for the downlink transmission within DS-CDMA systems employing block-transmission techniques, with an appropriate cyclic extension appended to each block. Our performance results show that the proposed receiver structure has excellent performance, close to the single-user MFB (matched filter bound), even for severe time-dispersive scenarios and/or in the presence of strong interfering channels.
- Dynamical studies and product analysis of the reaction between O(1D) and H2/D2Publication . Rio, Carolina; Brandão, J.In this work we study the dynamics of the O (1D) + H2/D2 reactions at fixed collision energies [4,5] using quasiclassical trajectories calculations on a double-valued potential energy surface for H2O [2].
- Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACEPublication . Riviere, G.; Michaud, A.; Deloffre, L.; Vandenbulcke, F.; Levoye, A.; Breton, C.; Corvol, P.; Salzet, M.; Vieau, D.Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood homoeostasis and reproduction in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two homologous active sites, have been characterized. So far, several ACEs from invertebrates have been cloned, but only in insects. They are soluble and display a single active site. Using biochemical procedures, an ACE-like activity was detected in our model, the leech, Theromyzon tessulatum. Annelida is the most distant phylum in which an ACE activity has been observed. To gain more insight into the leech enzyme, we have developed a PCR approach to characterize its mRNA. The approx. 2 kb cDNA has been predicted to encode a 616-amino-acid soluble enzyme containing a single active site, named TtACE (T tessulatum ACE). Surprisingly, its primary sequence shows greater similarity to vertebrates than to invertebrates. Stable in vitro expression of TtACE in transfected Chinese-hamster ovary cells revealed that the leech enzyme is a functional metalloprotease. As in mammals, this 79 kDa glycosylated enzyme functions as a dipeptidyl carboxypeptidase capable of hydrolysing angiotensin I to angiotensin II. However, a weak chloride inhibitory effect and acetylated N-acetyl-SDKP (Ac SDAcKP) hydrolysis reveal that TtACE activity resembles that of the N-domain of mammalian ACE. In situ hybridization shows that its cellular distribution is restricted to epithelial midgut cells. Although the precise roles and endogenous substrates of TtACE remain to be identified, characterization of this ancestral peptidase will help to clarify its physiological roles in non-insect invertebrate species.
- Com uma perna na serra e outra no Litoral: um estudo de caso sobre os jovens de Cachopo (Serra do Caldeirão)Publication . Sousa, Vanessa Duarte de; Custódio, TeresaEste texto constitui-se como uma abordagem introdutória a um trabalho de investigação-ação desenvolvido em Cachopo entre 2003-2004. O estudo visava a criação de estímulos à fixação da população jovem no território.
- Staging of Atlantic halibut (Hippoglossus hippoglossus L.) from first feeding through metamorphosis, including cranial ossification independent of eye migrationPublication . Sæle, Ø.; Solbakken, J. S.; Watanabe, K.; Hamre, K.; Power, Deborah; Pittman, K.To determine developmental stages independent of eye migration, a highly plastic feature in Atlantic halibut, 180 sibling halibut larvae reared at an average temperature of 11.9 jC from first feeding and for a further 46 days were examined, cleared and stained for ossification and the cranial development was recorded. Morphological development and cranial ossification generally coincided. The order of ossification of cranial structures was: jaw structures, hyoid arch, opercular bones and structures of the neurocranium. The Frontale exhibited torsion correlated with eye migration, but calcification began earlier and full calcification was independent of ocular displacement. The appearance of ossified elements was used to group larvae into Stages 5–9, comprising premetamorphosis to climax metamorphosis, with significant morphometric differences between stages. The trajectory of juvenile development appears fixed by Stage 8. There was a linear relationship between stage and myotome height (R2 = 0.86) and stage and standard length (R2 = 0.80). The stage definitions were validated on two groups (n = 23, n = 101) of commercially produced larvae. Because metamorphosis is protracted in halibut, use of these stages and especially myotome height should help standardize sampling and analysis between experiments and between producers.