Comparação de dois métodos em espectrometria de raios gama para análise de radioatividade de baixo nível

A atividade dos elementos determinada pela espectrometria de raios gama depende do número de contagens no pico de energia da linha gama de interesse. O método convencional, que considera a área sob o pico, é comparado com uma técnica alternativa que considera o número de contagens na altura máxima do canal central do pico. A radioatividade de baixo nível deve ter precisão suficiente de acordo com as normas nacionais e internacionais, por isso métodos gráficos são utilizados na estimativa da resolução e da ordenada máxima com baixos valores de erros sistemáticos. Ambas as técnicas foram empregadas e comparadas na análise da linha gama de 1460,8keV do 40K em leite em pó usando um detector de GeHP

estudo de cerâmica arqueologica do parana por tecnicas nucleares nao destrutivas

Fragmentos de cerâmica indígena da região de Londrina, norte do estado do Paraná, sul do Brasil, pertencentes à coleção arqueológica do Museu "Padre Carlos Weiss" foram estudados por EDXRF, RBS e Transmissão de Raios Gama. Além da composição química da pasta cerâmica, também foi possível detectar alguns elementos dos vestígios da decoração plástica. Foram obtidas as composições quantitativas das pastas cerâmicas e comparadas com os resultados de análise química por espectroscopia de emissão atômica. Os fragmentos também foram analisados por transmissão de raios gama para inspecionar sua estrutura interna e homogeneidade. A análise densitométrica mostra claramente pastas cerâmicas bastante diferenciadas, tanto em homogeneidade como em densidade, sendo posssível a caracterização de algumas técnicas de manufatura da pasta, como a inclusão de pequenos fragmentos cerâmicos como antiplástic

Study o f archaeological pottery from Paraná State em ploying nuclear non destructive techniques

Fragmentos de cerâmica indígena da região de Londrina, norte do estado do Paraná, sul do Brasil, pertencentes à coleção arqueológica do Museu “Padre Carlos Weiss” foram estudados por EDXRF, RBS e Transmissão de Raios Gama. Além da composição química da pasta cerâmica, também foi possível detectar alguns elementos dos vestígios da decoração plástica. Foram obtidas as composições quantitativas das pastas cerâmicas e comparadas com os resultados de análise química por espectroscopia de emissão atômica. Os fragmentos também foram analisados por transmissão de raios gama para inspecionar sua estrutura interna e homogeneidade. A análise densitométrica mostra claramente pastas cerâmicas bastante diferenciadas, tanto em homogeneidade como em densidade, sendo posssível a caracterização de algumas técnicas de manufatura da pasta, como a inclusão de pequenos fragmentos cerâmicos como antiplásticoIndian ceramic fragments from the region of Londrina, at the north of Paraná state, south of Brazil, belonging to the “Padre Carlos Weiss” Museum archaeological collection, were studied by EDXRF, RBS and Gamma Ray Transmission.Besides ceramic pastes’ elements, it was also possible to detect some elements of the plastic decoration remains. Quantitative determination of the pastes composition was obtained and compared with chemical analysis by atomic emission spectroscopy. The fragments were also analyzed by gamma ray transmission in order to inspect their internal structure and homogeneity. The densitometric analysis clearly showed very differentiated ceramic pastes, both in homogeneity and density, being possible the characterization of some ceramic paste manufacture techniques, as the inclusion of small ceramic fragments as antiplasti

Impacto ambiental da recuperação de áreas degradadas com utilização de leguminosas arbóreas na região de Mata Atlântica no estado do Rio de Janeiro.

Made available in DSpace on 2011-04-09T14:12:21Z (GMT). No. of bitstreams: 1 27Impactoambientaldarecuperacaodeareasdegradadascomutilizacaodeleguminosas.pdf: 71498 bytes, checksum: a5cdabe6b1a8ed2704bdfdfef629f7eb (MD5) Previous issue date: 2011-02-04201

Stressed out symbiotes:hypotheses for the influence of abiotic stress on arbuscular mycorrhizal fungi

Abiotic stress is a widespread threat to both plant and soil communities. Arbuscular mycorrhizal (AM) fungi can alleviate effects of abiotic stress by improving host plant stress tolerance, but the direct effects of abiotic stress on AM fungi are less well understood. We propose two hypotheses predicting how AM fungi will respond to abiotic stress. The stress exclusion hypothesis predicts that AM fungal abundance and diversity will decrease with persistent abiotic stress. The mycorrhizal stress adaptation hypothesis predicts that AM fungi will evolve in response to abiotic stress to maintain their fitness. We conclude that abiotic stress can have effects on AM fungi independent of the effects on the host plant. AM fungal communities will change in composition in response to abiotic stress, which may mean the loss of important individual species. This could alter feedbacks to the plant community and beyond. AM fungi will adapt to abiotic stress independent of their host plant. The adaptation of AM fungi to abiotic stress should allow the maintenance of the plant-AM fungal mutualism in the face of changing climates. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00442-016-3673-7) contains supplementary material, which is available to authorized users

Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia