4,224 research outputs found
Crescimento de raízes e sanidade de cipó-titica (Heteropsis flexuosa) submetido à exploração no Estado do Amapá.
Editado por Lúcia Helena de Oliveira Wadt
Estrutura e distribuição espacial de andirobeiras (Carapa spp.) em floresta de várzea do Estuário Amazônico.
O objetivo geral deste trabalho foi avaliar se a densidade de ocorrência de andirobeiras é dependente da distância do rio Amazonas, analisando sua distribuição espacial e a estrutura diamétrica da população em um trecho de floreta de várzea no Estado do Amapá. Esse trabalho faz parte do projeto Florestam (Ecologia e manejo florestal para uso múltiplo de várzeas do estuário amazônico) e foi desenvolvido em uma área de proteção ambiental (APA) de 136,59 ha, localizada no Distrito da Fazendinha, município de Macapá - AP (00°03’04,24”S e 51º07’42,72”W). Foram lançados 3 transectos perpendiculares à margem do rio Amazonas, distanciados entre si a cada 500 m, para orientar no direcionamento e localização das árvores
Optimal configuration of microstructure in ferroelectric materials by stochastic optimization
An optimization procedure determining the ideal configuration at the
microstructural level of ferroelectric (FE) materials is applied to maximize
piezoelectricity. Piezoelectricity in ceramic FEs differ significantly from
that of single crystals because of the presence of crystallites (grains)
possessing crystallographic axes aligned imperfectly. The piezoelectric
properties of a polycrystalline (ceramic) FE is inextricably related to the
grain orientation distribution (texture). The set of combination of variables,
known as solution space, which dictates the texture of a ceramic is unlimited
and hence the choice of the optimal solution which maximizes the
piezoelectricity is complicated. Thus a stochastic global optimization combined
with homogenization is employed for the identification of the optimal granular
configuration of the FE ceramic microstructure with optimum piezoelectric
properties. The macroscopic equilibrium piezoelectric properties of
polycrystalline FE is calculated using mathematical homogenization at each
iteration step. The configuration of grains characterised by its orientations
at each iteration is generated using a randomly selected set of orientation
distribution parameters. Apparent enhancement of piezoelectric coefficient
is observed in an optimally oriented BaTiO single crystal. A
configuration of crystallites, simultaneously constraining the orientation
distribution of the c-axis (polar axis) while incorporating ab-plane
randomness, which would multiply the overall piezoelectricity in ceramic
BaTiO is also identified. The orientation distribution of the c-axes is
found to be a narrow Gaussian distribution centred around . The
piezoelectric coefficient in such a ceramic is found to be nearly three times
as that of the single crystal.Comment: 11 pages, 7 figure
Large and small-scale structures and the dust energy balance problem in spiral galaxies
The interstellar dust content in galaxies can be traced in extinction at
optical wavelengths, or in emission in the far-infrared. Several studies have
found that radiative transfer models that successfully explain the optical
extinction in edge-on spiral galaxies generally underestimate the observed
FIR/submm fluxes by a factor of about three. In order to investigate this
so-called dust energy balance problem, we use two Milky Way-like galaxies
produced by high-resolution hydrodynamical simulations. We create mock optical
edge-on views of these simulated galaxies (using the radiative transfer code
SKIRT), and we then fit the parameters of a basic spiral galaxy model to these
images (using the fitting code FitSKIRT). The basic model includes smooth
axisymmetric distributions along a S\'ersic bulge and exponential disc for the
stars, and a second exponential disc for the dust. We find that the dust mass
recovered by the fitted models is about three times smaller than the known dust
mass of the hydrodynamical input models. This factor is in agreement with
previous energy balance studies of real edge-on spiral galaxies. On the other
hand, fitting the same basic model to less complex input models (e.g. a smooth
exponential disc with a spiral perturbation or with random clumps), does
recover the dust mass of the input model almost perfectly. Thus it seems that
the complex asymmetries and the inhomogeneous structure of real and
hydrodynamically simulated galaxies are a lot more efficient at hiding dust
than the rather contrived geometries in typical quasi-analytical models. This
effect may help explain the discrepancy between the dust emission predicted by
radiative transfer models and the observed emission in energy balance studies
for edge-on spiral galaxies.Comment: 9 pages, 5 figures, accepted for publication in A&
Mating behaviour and reproductive output in insecticide-resistant and -susceptible strains of the maize weevil (\u3ci\u3eSitophilus zeamais\u3c/i\u3e)
Insecticide resistance is a broadly recognised and well-studied management problem resulting from intensive insecticide use, which also provides useful evolutionary models of newly adapted phenotypes to changing environments. Two common assumptions in such models are the existence of fitness costs associated with insecticide resistance, which will place the resistant individuals at a disadvantage in insecticide-free environments, and the prevalence of random mating among insecticide-resistant and -susceptible individuals. However, cases of insecticide resistance lacking apparent fitness disadvantages do exist impacting the evolution and management of insecticide resistance. Assortative mating, although rarely considered, may also favour the evolution and spread of insecticide resistance. Thus, the possible existence of both conditions in the maize weevil (Sitophilus zeamais), a key pest of stored cereals, led to the assessment of the mating behaviour and reproductive fitness of insecticide-resistant and -susceptible weevil strains and their reciprocal crosses. The patterns of female and male mating choice also were assessed. Although mating behaviour within and between weevil strains was similar without mate choice, mating within the resistant strain led to higher reproductive output than within the susceptible strain; inter-strain matings led to even higher fertility. Thus, no apparent fitness cost associated with resistance seems to exist in these weevils, favouring the evolution of this phenotype that is further aided by the higher fertility of inter-strain matings. Mate choice reduced latency to mate and no inter-strain preference was detected, but female weevils were consistent in their mate selection between 1st and 2nd matings indicating existence of female mating preference among maize weevils. Therefore, if female mate selection comes to favour trait(s) associated with insecticide resistance, higher reproductive fitness will be the outcome of such matings favouring the evolution and spread of insecticide resistance among maize weevil populations reverting into a management concern
Germinação e morfologia de plântulas de Licania macrophylla (Crhysobalanaceae), nativa da floresta de várzea do Estuário, Amapá, Brasil.
A Amazônia possui muitas espécies arbóreas com fins econômicos e de estudos científicos, dentre estas encontra-se Licania macrophylla Benth., conhecida popularmente por ?anoerá?. Possui uma grande distribuição na América do Sul, podendo ser encontrada principalmente em áreas de várzea das regiões do Baixo Amazonas [1]. As comunidades amazônicas a utilizam no tratamento de doenças como parasitoses amebianas e distúrbios diarreicos e para alimentação preparam o macerado das sementes [2]. Apesar de sua importância, pouco se sabe sobre o desenvolvimento inicial dessa espécie e como identificá-la em campo. Estudos sobre germinação e morfologia de plântulas são fundamentais para subsidiar a produção de mudas em viveiros e avaliar a regeneração natural, ações importantes para a manutenção de espécies florestais com interesse econômico. Portanto, o objetivo foi avaliar a germinação e a morfologia de plântulas dessa espécie
Frutos e sementes de Mora Paraensis (Ducke) Ducke (Fabaceae) em uma floresta de várzea do Estuário Amazônico, Amapá.
Florística e fitossociologia em áreas de manejo de açaizais no estuário amazônico.
Este estudo teve como objetivo analisar a composição florística e a fitossociologia em três regiões do estuário amazônico em que é praticado o manejo de açaizais nativos. Nas regiões foram instaladas 30 parcelas de 0,5 ha e amostradas todas as espécies arbóreas e palmeiras com DAP ? 5 cm, mediu-se também a circunferência a altura do peito (CAP) com fita métrica de precisão de 1mm. Foram inventariados 10821 indivíduos, representados por 114 espécies, 96 gêneros e 33 famílias. As famílias mais representativas foram Arecaceae (9 espécies e 8007 indivíduos), seguida por Rubiaceae (2 espécies e 522 indivíduos),Myristicaceae (1 espécie e 268 indivíduos), Malvaceae (10 espécies e 264 indivíduos) e Euphorbiaceae (4 espécies e 247 indivíduos). Constatou-se que a riqueza nas áreas de manejo inventariadas permaneceu alta apesar da pressão antrópica que essas áreas sofrem
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