11,909 research outputs found
Anthropogenic Habitats Facilitate Dispersal of an Early Successional Obligate: Implications for Restoration of an Endangered Ecosystem
Landscape modification and habitat fragmentation disrupt the connectivity of natural landscapes, with major consequences for biodiversity. Species that require patchily distributed habitats, such as those that specialize on early successional ecosystems, must disperse through a landscape matrix with unsuitable habitat types. We evaluated landscape effects on dispersal of an early successional obligate, the New England cottontail (Sylvilagus transitionalis). Using a landscape genetics approach, we identified barriers and facilitators of gene flow and connectivity corridors for a population of cottontails in the northeastern United States. We modeled dispersal in relation to landscape structure and composition and tested hypotheses about the influence of habitat fragmentation on gene flow. Anthropogenic and natural shrubland habitats facilitated gene flow, while the remainder of the matrix, particularly development and forest, impeded gene flow. The relative influence of matrix habitats differed between study areas in relation to a fragmentation gradient. Barrier features had higher explanatory power in the more fragmented site, while facilitating features were important in the less fragmented site. Landscape models that included a simultaneous barrier and facilitating effect of roads had higher explanatory power than models that considered either effect separately, supporting the hypothesis that roads act as both barriers and facilitators at all spatial scales. The inclusion of LiDAR-identified shrubland habitat improved the fit of our facilitator models. Corridor analyses using circuit and least cost path approaches revealed the importance of anthropogenic, linear features for restoring connectivity between the study areas. In fragmented landscapes, human-modified habitats may enhance functional connectivity by providing suitable dispersal conduits for early successional specialists
Simulation of Chua's Circuit by Means of Interval Analysis
The Chua's circuit is a paradigm for nonlinear scientific studies. It is
usually simulated by means of numerical methods under IEEE 754-2008 standard.
Although the error propagation problem is well known, little attention has been
given to the relationship between this error and inequalities presented in
Chua's circuit model. Taking the average of round mode towards and
, we showed a qualitative change on the dynamics of Chua's circuit.Comment: 6th International Conference on Nonlinear Science and Complexity -
S\~ao Jos\'e dos Campos, 2016, p. 1-
Effect of three larval diets on the development of the armyworm, Spodoptera latifascia Walker, 1856 (Noctuidae, Lepidoptera)
Some biological effects of feeding larvae of the armyworm Spodoptera latifascia with leaves of three plant species (cotton, soybean and lettuce) have been studied. Some indicative measurements were utilized to determine the host suitability of these three plant species. Cotton leaves (Gossypium hirsutum) were found to be better than soybean (Glycine max) for the development and growth of this insect. Lettuce leaves (Lactuca sativa) were incapable of sustaining this insect. Moreover, the stress of the latter diet was associated with a latent microbial disease, a mixed infection caused by Vairimorpha sp. and a nuclear polyhedrosis virus (NPV). Cotton leaves can be recommended as a suitable diet for mass rearing of this insect species. Due to recent outbreks of S. latifascia observed in the States of São Paulo, Santa Catarina and Paraná and because of the frequent applications of wide spectrum chemical insecticides, it can be expected that this insect will soon become one of the important pests threatening cotton and other economic plantations in Brazil.17718
Orbital Characteristics of the Subdwarf-B and F V Star Binary EC~20117-4014(=V4640 Sgr)
Among the competing evolution theories for subdwarf-B (sdB) stars is the
binary evolution scenario. EC~20117-4014 (=V4640~Sgr) is a spectroscopic binary
system consisting of a pulsating sdB star and a late F main-sequence companion
(O'Donoghue et al. 1997), however the period and the orbit semi-major axes have
not been precisely determined. This paper presents orbital characteristics of
the EC 20117-4014 binary system using 20 years of photometric data. Periodic
Observed minus Calculated (O-C) variations were detected in the two highest
amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating
the binary system's precise orbital period (P = 792.3 days) and the
light-travel time amplitude (A = 468.9 s). This binary shows no significant
orbital eccentricity and the upper limit of the eccentricity is 0.025 (using 3
as an upper limit). This upper limit of the eccentricity is the lowest
among all wide sdB binaries with known orbital parameters. This analysis
indicated that the sdB is likely to have lost its hydrogen envelope through
stable Roche lobe overflow, thus supporting hypotheses for the origin of sdB
stars. In addition to those results, the underlying pulsation period change
obtained from the photometric data was = 5.4 (0.7)
d d, which shows that the sdB is just before the end of the
core helium-burning phase
Aplicações de técnicas de análise de imagem em microbiologia ambiental
São evidenciadas algumas aplicações da análise de imagem em
microbiologia ambiental, nomeadamente: o reconhecimento e identificação automática
de algumas espécies de protozoários presentes em estações de tratamento de águas
residuais; o estudo da influência de três tóxicos na mobilidade do protozoário ciliado
Tetrahymena pyriformis em meio líquido; a correlação entre actividade metanogénica,
velocidade de sedimentação e parâmetros morfológicos de agregados microbianos em
digestores anaeróbios; e finalmente o estudo da correlação entre as actividades
metanogénicas acetoclástica e hidrogenofílica e a fluorescência de um consórcio de
microrganismos de um digestor anaeróbio. Procura-se assim demonstrar a utilidade das
técnicas de análise de imagem na monitorização quer de processos de tratamento de
águas resíduais quer da própria qualidade ambiental.Ministério da Ciência e Tecnologia. Instituto de Cooperação Científica e Tecnológica Internacional (ICCTI).Embaixada de França em Portugal
Photometric stability analysis of the Exoplanet Characterisation Observatory
Photometric stability is a key requirement for time-resolved spectroscopic
observations of transiting extrasolar planets. In the context of the Exoplanet
Characterisation Observatory (EChO) mission design, we here present and
investigate means of translating spacecraft pointing instabilities as well as
temperature fluctuation of its optical chain into an overall error budget of
the exoplanetary spectrum to be retrieved. Given the instrument specifications
as of date, we investigate the magnitudes of these photometric instabilities in
the context of simulated observations of the exoplanet HD189733b secondary
eclipse.Comment: submitted to MNRA
Morphological characterisation of microbial aggregates by image analysis
A program, was accomplished in MATLAB,
that allows the morphological characterisation of
particles with special emphasis to microbial
aggregates. After automatic identification and
isolation of different particles in a real image, the
program determines several fractal dimensions as the
mass dimension, the surface dimension, the area versus
perimeter dimension, and the area vs. Feret diameter.
The values of many other parameters are also
provided, such as: convexity, compactness, roundness,
as well as the 0th, 1st, and 2nd moments, whether the
0th moment is the area or the volume of the particle.
The program also displays the particle size
distribution. The program is easy to operate and all the
steps that need decisions from the user are displayed in
menus and buttons. As an example of application, the
morphological characterisation of different microbial
aggregates present in anaerobic wastewater treatment
systems has been performed
Propagação vegetativa em aceroleira: II - produção da muda em telado.
Considerando essas questões a EMBRAPA/CPATSA desenvolveu um trabalho visando determinar, para as áreas irrigadas do Nordeste semi-árido um método alternativo para a propagação vegetativa da aceroleira
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