Browsing by Issue Date, starting with "2007-09"
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- A modified DMBE IV Potential with spectroscopic accuracy: vibrational levels and rotational constantsPublication . Rio, CarolinaThe hydroxyl radical, HO2, is the intermediate of the H + O2 O + OH reaction of overwhelming importance in atmospheric and reaction chemistry. As a consequence we can found many studies of the potential energy surface of the X 2A'' HO2 ground state.
- Turbo equalization with cancellation of nonlinear distortion effects for CP-Assisted and Zero-Padded MC-CDMA signalsPublication . Dinis, Rui; Silva, Paulo; Araújo, TeresaWe consider MC-CDMA schemes, with reduced envelope fluctuations. Both CP-assisted (cyclic prefix) and ZP (zero-padded) MC-CDMA schemes are addressed. We develop turbo FDE (frequency-domain equalization) schemes, combined with cancelation of nonlinear distortion effects. The proposed turbo receivers allow significant performance improvements at low and moderate SNR, even when the transmitted signals have reduced envelope fluctuations.
- Interactions between shorebirds and benthic invertebrates at Culbin Sands lagoon, NE Scotland: effects of avian predation on their prey community density and structurePublication . Mendonca, Vanda Mariyam; Raffaelli, David George; Boyle, Peter R.In the North Sea, during autumn-winter, intertidal flats often receive a massive influx of migratory shorebirds (wildfowl, waders and seabirds), which utilise the high prey densities that are available. The present study was conducted at Culbin Sands lagoon, NE Scotland, in 1994-1996, to investigate benthic invertebrate standing stock, and the energy flow from benthic invertebrates to shorebirds. Benthic invertebrate standing stock was estimated to be 500 kJ m(-2) yr(-1), and shorebird consumption efficiency to be 18% of the available standing stock. A series of manipulative field experiments were then conducted to test the effects of shorebirds on benthic invertebrate densities and community structure. Birds were excluded from caged areas (exclosures), and benthic invertebrate densities (total and by class size) in caged and uncaged areas were compared for each season separately. During autumn-winter, especially the gastropod Hydrobia ulvae and larger-sized (> 15 mm) clams Macoma balthica were observed to be the roost impacted species, being significantly more abundant in bird-exclosures than in bird-accessed areas.
- Química: "Os átomos juntos são outra coisa"Publication . Rio, CarolinaPara estimular o interesse nas ciências exactas dos alunos do ensino secundário, a Faculdade de Ciências e Tecnologia da Universidade do Algarve organiza esta escola de verão cujo tema é "O Mundo Quântico".
- On sense and reference: examining the functional neuroanatomy of referential processingPublication . Nieuwland, Mante S.; Petersson, Karl Magnus; Van Berkum, Jos J. A.In an event-related fMRI study, we examined the cortical networks involved in establishing. reference during language comprehension. We compared BOLD responses to sentences containing referentially ambiguous pronouns (e.g., "Ronald told Frank that he..."), referentially failing pronouns (e.g., "Rose told Emily that he...") or coherent pronouns. Referential ambiguity selectively recruited media[ prefrontal regions, suggesting that readers engaged in problemsolving to select a unique referent from the discourse model. Referential failure elicited activation increases in brain regions associated with mo rp ho -syntactic processing, and, for those readers who took failing pronouns to refer to unmentioned entities, additional regions associated with elaborative inferencing were observed. The networks activated by these two referential problems did not overlap with the network activated by a standard semantic anomaly. Instead, we observed a double dissociation, in that the systems activated by semantic anomaly are deactivated by referential ambiguity, and vice versa. This inverse coupling may reflect the dynamic recruitment of semantic and episodic processing to resolve semantically or referentially problematic situations. More generally, our findings suggest that neurocognitive accounts of language comprehension need to address not just how we parse a sentence and combine individual word meanings, but also how we determine who's who and what's what during language COmprehension. (c) 2007 Elsevier Inc. All rights reserved.
- Are we overestimating the number of cell-cycling genes? The impact of background models for time series data.Publication . Futschik, Matthias; Herzel, H.Periodic processes play fundamental roles in organisms. Prominent examples are the cell cycle and the circadian clock. Microarray array technology has enabled us to screen complete sets of transcripts for possible association with such fundamental periodic processes on a system-wide level. Frequently, quite a large number of genes has been detected as periodically expressed. However, the small overlap of identified genes between different studies has shaded considerable doubts about the reliability of the detected periodic expression. In this study, we show that a major reason for the lacking agreement is the use of an inadequate background model for the determination of significance. We demonstrate that the choice of background model has considerable impact on the statistical significance of periodic expression. For illustration, we reanalyzed two microarray studies of the yeast cell cycle. Our evaluation strongly indicates that the results of previous analyses might have been overoptimistic and that the use of more suitable background model promises to give more realistic results
- Aplicação de métodos estatísticos na avaliação da satisfação dos utentes com o internamento hospitalarPublication . Pedro, Sílvia Maria Dias; Mendes, Júlio; Ferreira, Pedro LopesIt is well-established that important indicators for the improvement of quality care strategies can be drawn from the evaluation of patients' satisfaction levels. This study adds to the literature by exploring a unique database maintained by the Centro de Estudos e Investigação em Saúde da Universidade de Coimbra, which results from the IAQH-IA questionnaire. The data accounts for a total of 6.363 patients, representing a three-year period (2000-2004) and as many as 20 different hospitals.