298 research outputs found
Short-reach MCF-based systems employing KK Receivers and feedforward neural networks for ICXT mitigation
This paper proposes and evaluates the use of machine learning (ML) techniques for mitigating the effect of the random inter-core crosstalk (ICXT) on 256 Gb/s short-reach systems employing weakly coupled multicore fiber (MCF) and Kramers–Kronig (KK) receivers. The performance improvement provided by the k-means clustering, k nearest neighbor (KNN) and feedforward neural network (FNN) techniques are assessed and compared with the system performance obtained without employing ML. The FNN proves to significantly improve the system performance by mitigating the impact of the ICXT on the received signal. This is achieved by employing only 10 neurons in the hidden layer and four input features for the training phase. It has been shown that k-means or KNN techniques do not provide performance improvement compared to the system without using ML. These conclusions are valid for direct detection MCF-based short-reach systems with the product between the skew (relative time delay between cores) and the symbol rate much lower than one (skew×symbol rate≪1). By employing the proposed FNN, the bit error rate (BER) always stood below 10−1.8 on all the time fractions under analysis (compared with 100 out of 626 occurrences above the BER threshold when ML was not used). For the BER threshold of 10−1.8 and compared with the standard system operating without employing ML techniques, the system operating with the proposed FNN shows a received optical power improvement of almost 3 dB.info:eu-repo/semantics/publishedVersio
Population structure of Pentaclethra macroloba (Willd.) Kuntze in high and low floodplains of the Amazonian estuary.
The flood cycle of floodplain forests and topographic variations are important factors of diversification and morphological and ecophysiological adaptations of the plant community. Pentaclethra macroloba is a hyperdominant species adapted to flood variations. The objective of this study was to characterize the P. macroloba population structure between environments with high topography, flooded only during the rainy season and peak flood of the river, (high várzea-HV) and low topography with daily flood (low várzea-LV). The study was carried in the Mazagão Experimental Field, Brazil. Four plots of 1 ha were installed in each environment. All individuals with DBH ≥ 5 cm were measured and georeferenced. ANOVA test, 0.05% probability, was applied to verify the structural differences between two environments. The HV had higher population density (51.2 individuals.ha-1) compared to the LV (36.7 individuals.ha-1), although without significance. Basal area was higher in the HV (10.42 m²) in comparison with LV (5.90 m²), with significant difference (F = 7.13, p = 0.00795). The maximum DAP of HV was 67 cm with mean of 24 cm. The LV presented maximum DBH of 42 cm with mean of 21 cm, showing structural difference between the two environments (F = 6.22, p = 0.0131). The aggregation index showed high aggregation in the LV (R = 0.89) than in the HV (R = 0.79), differing significantly between the two environments (F = 11.31, p = 0.0008). Frequency and time of flooding are ecological drives that structure the population of pracaxizeiro causing morphological and ecophysiological adaptations to the individual
Electron microprobe analysis of cryolite
Comunicação apresentada em: EMAS 2013 : 13th European
Workshop on Modern Developments and Applications in Microbeam Analysis, Centro de Congressos da Alfândega do Porto, Portugal, 12 to 16 May 2013A sample of cryolite was studied with a JEOL JXA 8500-F electron microprobe under several operating conditions. A TAP crystal was used to analyse Na and Al
and a LDE1 crystal to analyse F. As F and Na are both highly "volatile" elements, special care must be taken during analysis. The measurement order of Na, F
and Al is not irrelevant and optimum conditions may also result in different combinations of accelerating voltage, beam current, beam size or counting times.
Relevant X-ray signals were recorded in order to investigate the behaviour of the Na Ka and F Ka counts with elapsed time. The incident beam current was
also recorded at the same time. In a clear contrast to what has normally been reported in the EPMA analysis of aluminosilicates and silicate glasses, we found
that the Na X-ray counts increase with time. This increment of X-rays intensities for sodium in cryolite depends on the operating conditions and is
accompanied by a strong migration of fluorine from the beam excitation volume, leading to a decrease in F X-ray counting rates. It was also observed that
higher incident beam currents induce higher radiation damage in the mineral. The current instability is consistent with possible electron induced dissociation in
the cryolite structure. An analytical protocol was achieved for 6 kV and 15kV accelerating voltage for the correct EPMA analysis of cryolite
The effect of flooding on the exchange of the volatile C<sub>2</sub>-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere
International audienceThe effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid was investigated with 2?3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited significant emissions of any of the compounds. A slight deposition of acetaldehyde and acetic acid was mainly observed, instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid occurred only by the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning confirmed that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (3?200 nmol m?2 min?1 for ethanol and 5?500 nmol m?2 min?1 for acetaldehyde). Acetic acid emissions reached 12 nmol m?2 min?1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere
River damming affects seedling communities of a floodplain forest in the Central Amazon
The flood pulse of black water rivers in the Amazon basin determines the composition of species along the flood gradient in igapó forests. The Balbina dam, built on the Uatumã River, has altered the flood pulse and caused changes in the floristic composition of adult trees throughout the downstream area. There is a lack of studies on how communities of seedlings in igapó forests respond to changes in the flood pulse. This study investigates the response of seedling communities in the igapó forest downstream the Balbina dam and compares it with two pristine areas. The areas were sampled with transects of 1x25 m within 36 plots (25x25 m) along the flood gradient. Richness and dominance were calculated by simple regression and ordination analyses. The pristine areas had the same pattern of richness, dominance and genera distribution along the flood gradient. However, the affected Uatumã area formed different groups of genera by NMDS analysis, which divided them along the flood gradient with significantly increased dominance of three genera. The insertion of the Balbina dam resulted a loss of lateral and longitudinal connectivity for the Uatumã River, and the alteration to seedling communities may alter the future landscape of downstream igapó forests
Using assistive robots to promote inclusive education
Purpose: This paper describes the development and test of physical and virtual integrated augmentative manipulation and communication assistive technologies (IAMCATs) that enable children with motor and speech impairments to manipulate educational items by controlling a robot with a gripper, while communicating through a speech generating device. Method: Nine children with disabilities, nine regular and nine special education teachers participated in the study. Teachers adapted academic activities so they could also be performed by the children with disabilities using the IAMCAT. An inductive content analysis of the teachers’ interviews before and after the intervention was performed. Results: Teachers considered the IAMCAT to be a useful resource that can be integrated into the regular class dynamics respecting their curricular planning. It had a positive impact on children with disabilities and on the educational community. However, teachers pointed out the difficulties in managing the class, even with another adult present, due to the extra time required by children with disabilities to complete the activities. Conclusions: The developed assistive technologies enable children with disabilities to participate in academic activities but full inclusion would require another adult in class and strategies to deal with the additional time required by children to complete the activities. Implications for Rehabilitation Integrated augmentative manipulation and communication assistive technologies are useful resources to promote the participation of children with motor and speech impairments in classroom activities. Virtual tools, running on a computer screen, may be easier to use but further research is needed in order to evaluate its effectiveness when compared to physical tools. Full participation of children with motor and speech impairments in academic activities using these technologies requires another adult in class and adequate strategies to manage the extra time the child with disabilities may require to complete the activities.info:eu-repo/semantics/acceptedVersio
Variabilidade de isolados de Xanthomonas axonopodis pv. passiflorae no estado do Pará.
Edição dos resumos do 44º Congresso Brasileiro de Fitopatologia, 2011, Bento Gonçalves. Resumo 797
Extratos aquosos de Artocarpus heterophyllus Lam. e Morinda citrifolia Linn no controle da mancha bacteriana do maracujazeiro.
Edição dos resumos do 44º Congresso Brasileiro de Fitopatologia, 2011, Bento Gonçalves. Resumo 1244
Phenological behavior and foral visitors of Pentaclethra macroloba, a hyperdominant tree in the Brazilian Amazon River estuary.
Natural history of hyperdominant tree populations in the Brazilian Amazon Region is still unknown in plant science. Pentaclethra macroloba (Willd.) Kuntze (Fabaceae) is a hyperdominant tree species which has multiple uses and its seeds are extensively explored to extract medicinal oil. We evaluated the phenological cycles and floral visitors of P. macroloba and the effect of the daily tide of the Amazon River on the phenophases. Phenophases of flower bud, anthesis flowers, immature fruit, ripe fruit, seed dispersal, new leaf, mature leaf, and leaf fall of 29 trees in the Northeast of the Brazilian Amazon were monitored during 28 months. Hydrometeorological data of rainfall, maximum temperature and flood height on the tree trunk were obtained. Generalized Linear Models were used to explain the relationship between phenophases and hydrometeorological parameters. Flowering was synchronized in the dry season (flower buds: βtemperature = 1.30, p < 0.01 and flowers in anthesis: βtemperature = 1.84; p < 0.001). Immature fruits appeared during the dry season (βtemperature = 0.67; p < 0.01) and ripe fruits in the rainy season. Seeds were dispersed during the rainfall (βrainfall = 0.0051; p < 0.01) and flooding of the river (βwater = 0.12; p < 0.001). There was no relationship between leaf change and hydrometeorological variables. The main floral visitors were wasps, bees and ants. The rainfall seasonality is a key factor that stimulates reproductive events of P. macroloba. Daily river flooding can be considered a driver that stimulates the tree to disperse its seeds at the peak of the river flood, where they can be transported the long distances
Seasonal shifts in isoprenoid emission composition from three hyperdominant tree species in central Amazonia
Volatile isoprenoids regulate plant performance and atmospheric processes, and Amazon forests comprise the dominant source to the global atmosphere. Still, there is a poor understanding of how isoprenoid emission capacities vary in response to ecophysiological and environmental controls in Amazonian ecosystems. We measured isoprenoid emission capacities of three Amazonian hyperdominant tree species – Protium hebetatum, Eschweilera grandiflora, Eschweilera coriacea – across seasons and along a topographic and edaphic environmental gradient in the central Amazon. From wet to dry season, both photosynthesis and isoprene emission capacities strongly declined, while emissions increased among the heavier isoprenoids: monoterpenes and sesquiterpenes. Plasticity across habitats was most evident in P. hebetatum, which emitted sesquiterpenes only in the dry season, at rates that significantly increased along the hydro-topographic gradient from white sands (shallow root water access) to uplands (deep water table). We suggest that emission composition shifts are part of a plastic response to increasing abiotic stress (e.g. heat and drought) and reduced photosynthetic supply of substrates for isoprenoid synthesis. Our comprehensive measurements suggest that more emphasis should be placed on other isoprenoids, besides isoprene, in the context of abiotic stress responses. Shifting emission compositions have implications for atmospheric responses because of the strong variation in reactivity among isoprenoid compounds
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