1,340 research outputs found
Linear Invariant Systems Theory for Signal Enhancement
This paper discusses a linear time invariant (LTI) systems approach to signal enhancement via projective subspace techniques. It provides closed form expressions for the frequency response of data adaptive finite impulse response eigenfilters. An illustrative example using speech enhancement is also presented.Este artigo apresenta a aplicação da teoria de sistemas lineares invariantes no tempo (LTI) na anĂĄlise de tĂ©cnicas de sub-espaço. A resposta em frequĂȘncia dos filtros resultantes da decomposição em valores singulares Ă© obtida aplicando as propriedades dos sistemas LTI
SSA of biomedical signals: A linear invariant systems approach
Singular spectrum analysis (SSA) is considered from a linear invariant systems perspective. In this terminology, the extracted components are considered as outputs of a linear invariant system which corresponds to finite impulse response (FIR) filters. The number of filters is determined by the embedding dimension.We propose to explicitly define the frequency response of each filter responsible for the selection of informative components. We also introduce a subspace distance measure for clustering subspace models. We illustrate the methodology by analyzing lectroencephalograms (EEG).FCT - PhD scholarship (SFRH/BD/28404/2006)FCT - PhD scholarship (SFRH/BD/48775/2008
Identifying evoked potential response patterns using independent component analysis and unsupervised learning
Independent Component Analysis(ICA) is a pre-processing step widely used in brain studies. One of
the most common problems in artifact elimination or brain activity related studies is the ordering and
identification of the independent components(ICs). In this work, a novel procedure is proposed
which combines ICA decomposition at trial level with an unsupervised learning algorithm (K-means)
at participant level in order to enhance the related signal patterns which might represent interesting
brain waves. The feasibility of this methodology is evaluated with EEG data acquired with participants
performing on the Halstead Category Test. The analysis shows that it is possible to find the Feedback
Error Negativity (FRN) Potential at single-trial level and relate its characteristics with the performance
of the participant based on their knowledge of the abstract principle underlying the task.info:eu-repo/semantics/publishedVersio
CoexistĂȘncia de duas espĂ©cies exĂłticas de lagostins (Pacifastacus leniusculus e Procambarus clarkii) na bacia hidrogrĂĄfica do rio Sabor (NE Portugal)
Em Portugal existia uma Ășnica espĂ©cie europeia de lagostim de ĂĄgua doce, Austropotamobius pallipes, o lagostim-de-patas-brancas, que se considera actualmente extinta no paĂs. No nordeste de Portugal continental onde anteriormente ocorria esta espĂ©cie, os cursos de ĂĄgua estĂŁo actualmente a ser colonizados por duas espĂ©cies de lagostins norte americanos. Na dĂ©cada de 70, proveniente de Espanha onde foi intencionalmente introduzido, o lagostim-vermelho-da-Luisiana, Procambarus clarkii, colonizou rapidamente os rios do sul de Portugal, propagando-se depois por todas as massas hĂdricas do paĂs. Em 1994, as autoridades espanholas introduziram uma outra espĂ©cie, o lagostim sinal, Pacifastacus leniusculus, na provĂncia de Zamora, que foi detectada em Portugal, no rio Maçãs (Bacia do Sabor) trĂȘs anos depois. A propagação e evolução das populaçÔes destas espĂ©cies no rio Maçãs tĂȘm sido seguidas anualmente desde 2000. P. clarkii, espĂ©cie sub-tropical, nunca atingiu neste curso abundĂąncias muito elevados. Pelo contrĂĄrio, P. leniusculus, espĂ©cie de ĂĄguas mais frias, apresenta valores mais elevados, cerca de seis vezes superiores aos de P.clarkii. O lagostim sinal encontra-se bem adaptado, continuando a sua expansĂŁo neste rio e prevendo-se que venha a colonizar outras massas hĂdricas adjacentes. A expansĂŁo do lagostim vermelho de jusante para montante parece ser menos efectiva, nĂŁo tendo, desde 2005, sido observado em novos locais deste rio. A coexistĂȘncia das duas espĂ©cies verifica-se actualmente num troço fluvial de cerca de 45 km de extensĂŁo, apesar das diferenças notĂłrias ao nĂvel das caracterĂsticas dos seus habitats
Dispersal and coexistence of two non-native crayfish species (Pacifastacus leniusculus and Procambarus clarkii ) in NE Portugal over a 10-year period
NE Portugal is one of the most isolated and low populated regions of Western Europe. Recently, two American crayfish species reached this area: signal crayfish Pacifastacus leniusculus coming from Spain and red swamp crayfish Procambarus clarkii in its northward expansion. The dispersion of both species was followed throughout the last decade in river Maçãs (Douro catchment). Our results support the hypothesis of faster downstream colonisation. The mean spread rate of signal crayfish was faster for the downstream expansion, 2.8 km·yr-1, while the upstream rate was 1.7 km·yr-1. Exceptionally, in one period, the rate of spread reached 6.7 km·yr-1, which was apparently caused by downstream washing in extreme conditions of flow. The mean rate of spread is higher than the observed in other studies which may also be related to the low current velocity of late spring and summer that provides favourable conditions for a fast upstream colonisation. Coexistence of signal and red swamp crayfish was detected in a large river sector. Signal crayfish strongly dominates in the upper and intermediate sectors which are the colder part of the river and in the lower sectors, species abundances are not significantly different. Winter temperature in the higher altitude reaches seems to moderate the competitive abilities of P. clarkii
Colonization and dispersal rates of two non-native crayfish species (Pacifastacus leniusculus and Procambarus clarkii) in NE Portugal
In Europe, a generalized regression of the native crayfish was observed during the past decades. Simultaneously, several non-native species spread in most countries. In Portugal, the red swamp crayfish, Procambarus clarkii, is now occurring in most inland waters. The NE Portugal is one of the most isolated and low populated regions of Western Europe. Most rivers in these region present low levels of human impact and some are actually pristine. Recently, two American crayfish species reached the area: signal crayfish (Pacfastacus leniusculus) coming from Spain and red swamp crayfish. The isolation and the natural conditions of these rivers make them particularly valuable for the study of crayfish colonization and spreading. The colonization by both species was followed throughout the last decade in the Maçãs river (Douro catchment). Sampling was undertaken every year with baited traps. The average dispersal rate of signal crayfish was approximately 2 km/year, although a great variability among sectors was observed. Coexistence of signal and red swamp crayfish was detected in a large part of the river system. Signal crayfish developed well adapted and persistent populations. The lower abundance of red swamp crayfish is apparently caused by the low winter temperatures
Movement and interaction of two exotic crayfish (Pacifastacus leniusculus and Procambarus clarkii) using PIT telemetry in experimental conditions
The coexistence of two exotic crayfish species (Procambarus clarkii and Pacifastacus leniusculus) was observed in a stretch of Rio Maçãs (Douro basin, Northeast of Portugal). The red swamp crayfish, P. clarkii, a sub-tropical species, was first detected in 1979 in Rio Caia (Alentejo) and from there rapidly spread through most freshwater bodies. This species is extremely resistant to severe climatic conditions, living in such contrasting environments as South or Northeast streams of Portugal. The signal crayfish, Pacifastacus leniusculus, a cold-water crayfish recently reached Portuguese waters and is now spreading in Rio Maçãs. To characterise movements, activity patterns and interactions of both species an experiment was developed in a confined area using PIT telemetry equipment with a multi-point decoder unit connected to eight circular panel antennae. Data were collected from sympatric tagged populations monitored during several days, to detect interactions between individuals during night and day
ASSESSMENT OF ECOLOGICAL CONDITIONS OF PERMANENT MEADOWS IN THE ITALIAN ALPS: LOSS, BIODIVERSITY AND REMOTE SENSING CHANGE DETECTION
The monitoring of ecological condition of grasslands ecosystems in the
European Alps is a main issue for mountain regions, since the abandonment of
traditional and sustainable management practices has exposed grassland habitat
to significant impacts in a context of global environmental change.
The present research project was focused in assessment of the state of
permanent meadows in the lowlands of Valtellina Valley (80 km2), Italian Alps,
during the timeframe 1980-2000. In specific, it quantified the land use/land
cover changes and identified main drivers behind permanent meadows loss;
characterized the relationship between biodiversity in the meadows and the
spatial-environmental conditions in the landscape and by last evaluated the use
of satellite remote sensing data for fast change detection in landscape. To
achieve such aims, the research project was organized in three different
approaches presented in the four chapters of this thesis.
Concerning the quantification of the land use/land cover and identification of
main drivers behind permanent meadows loss, the results show a strong
decrease in meadows (-18.5%) in a context of agricultural land decrease and
human settlements increase. This was the land cover type with highest loss and
conversion rate during the study period. Meadows were converted to human
settlements (urban, industrial and roads), other agriculture uses (cultivation,
orchard, vineyard), bushland and uncultivated land. Meadows loss occurred
mainly in soils with good land capability, low slope, exposed to south and in
proximity of roads, urban settlements and bushland. Densities of urban,
industrial and bushland and land capability were the only significant drivers for
meadows loss, while distance to meadow edge, meadows density, distance to
roads and soil degradation were the only significant drivers for meadows
preservation.
Concerning the characterization of the relationship between biodiversity in the
meadows and the spatial-environmental conditions in the landscape, the results
evidenced that species richness and Shannon indices were best explained by
regressive models including changes occurred in spatial environmental
heterogeneity from 1980 to 2000. Species richness was negatively related to
strong decrease in meadows habitat area and recent urban area, while Shannon
index was positively related to the increase in landscape diversity. In contrast,
species evenness was better explained by regressive model including recent
spatial environmental heterogeneity and positively related to increase ineastness in the study area, and negatively affected both by the area of woody
and soil pH (KCl).
Concerning the evaluation of the use of satellite remotely sensing data for land
cover mapping and change detection in landscape, the results show that the
hybrid approach for land cover classification based of Landsat imagery was
highly accurate. Image differencing is the technique which best detect changes
in landscape as well as in urban, meadow and bush land. The accuracy of
change detection was moderate.
This thesis concludes that the conflict by land in locations densely occupied by
other land cover types with good land capability is the major threat to
meadows and avoidance of fragmentation may be a good strategy for its
preservation. The meadows habitat needs a well-designed landscape and
farming planning, which should account the economic value of the ecosystem
services provided by this habitat. In addition, to conserve plant diversity in
meadows it is necessary to avoid loss of meadows habitat, maintain landscape
diversity and execute a sustainable meadow management.
Remotely sensed imagery can be a reliable source of information for alps,
although particular attention should be made to the image pre-processing and
classification, as well as, to minimize topography effects in spectral
information
The effects of 6-month multi-component exercise intervention on body composition in aged women: a single-arm experimental with follow-up study
Multicomponent exercise programs, which combine multiple modalities such as aerobic
exercises, strength training exercises, flexibility exercises, and balance exercises, can help to promote
healthy aging and prevent chronic diseases in aged women. Thus, the goal of this study is to
examine if a multicomponent exercise program could improve body composition in community-
dwelling aged women. A 6-month single-arm quasi-experimental research was conducted using
a multicomponent exercise program for older adults. The sample included 38 women with a mean
age of 63.50 years (SD = 6.47 years). Body composition and anthropometric measurement was
conducted from baseline (T1), after intervention (T2), and follow-Up (T3). In addition, after exercise
intervention, a significant difference with moderate to large effects was reported for fat mass [η2p =
0.374, p < 0.001)], bone density [η2p = 0.374, p < 0.05)], percentage of water [η2p = 0.374, p < 0.001)],
and a metabolic equivalent task [η2p = 0.374, p < 0.05]. Additionally, a significant large effect size
between T1 and T2 was verified. However, body composition indicators seem to decrease below
baseline levels after concluding exercise intervention (T3). Muscle mass decreased significantly
after exercise intervention and mean scores were lower compared to baseline data (T1). Thus, a
positive effect of the multicomponent exercise program on body composition was established in
this group of community-dwelling aged women. However, the relative improvement in body fat
and muscle mass were lost after the exercise programâs conclusion for values below the baselines.
Avoiding detraining periods is, therefore, fundamental to maintaining the normal relative body
composition.This research was funded by national funds through the Portuguese Foundation for
Science and Technology, I.P., grant number UIDB/04748/2020info:eu-repo/semantics/publishedVersio
Injury risks for fitness instructors: a review of key factors
The labour risks control is an occupational health concern. Fitness participants have been increasing in the last years (Lindwall, 2004). Clientsâ demand and the increase in classes number take the fitness instructors (FI) to a higher injuries exposure due to high workload. It is possible to observe several variations in aerobic dance, cycling, pilates, strength training, flexibility and balance. The main differences are in the cardiovascular intensities and the low to high impact dance (Van Mechelen, Hlobil & Kemper, 1992). The FI are exposed to high volumes of classes and injuries risks due to the high number of students and classes (Couto et al., 2016). As far as our understanding goes, FI are 50% more prone to injuries incidence in comparison to students. Thus, the aim of this study was to assess by a bibliographic research the health and injuries risk in FI. This is a bibliographic review made in PUBMED, Google Scholar, SCIELO and Web of Science. The used keywords were âfitness instructors injuriesâ, âfitness professorâs injuriesâ, and âfitness instructorâs risksâ. From an analysis of 23 papers, ten were chosen considering title and abstract. After a full integral analysis, only five papers were selected for revision. The others did not aimed to analyse the injuries and the health risks for FI. The selected papers approached the injuries and health risk factors for FI. There is a positive and significant correlation between the formation levels and injuries incidence prevention in FI and students (Malek, Nalbone, Berger & Coburn, 2002). FI with higher classification prevent higher frequency of injuries events. The injuries prevalence was superior in FI than in students (72.4 â 75.9% and 22.8 â 43.3% respectively) (Mutoh, Sawai, Takanashi & Skurko, 1998; Francis, Francis & Welshons-Smith, 1985). The injuries were general inflammations, muscle strains or sprains and stress fractures by overuse (Rothenberger, Chang & Cable, 1988). The FI are more exposed to injuries than students are (0.17 injuries/100h vs 0.15/100h of practice, respectively) and about 77% of the injuries were in the lower limbs (Garrick, Gillien & Whiteside, 1986). There is a lack of research in FI injuries risk of factors. However, FI seem to have a higher exposure to injuries in comparison to students. The high workload seem to be determinant to the incidence of overuse injuries.info:eu-repo/semantics/publishedVersio
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