1,548 research outputs found
Conservation status of the dwarf Caiman Paleosuchus Palpebrosus in the region of the Araguaia-Tocantins basin, Brazil.
Seleção de variedades de cana-de-açúcar com capacidade de penetração de raízes em horizontes coesos de agrissolos de Tabuleiros Costeiros.
Finite Temperature Phase Diagram of Quasi-Two-Dimensional Imbalanced Fermi Gases Beyond Mean-Field
We investigate the superfluid transition temperature of quasi-two-dimensional
imbalanced Fermi gases beyond the mean-field approximation, through the
second-order (or induced) interaction effects. For a balanced Fermi system the
transition temperature is suppressed by a factor . For imbalanced
Fermi systems, the polarization and transition temperature of the tricritical
point are significantly reduced as the two-body binding energy
increases.Comment: 6 pages, 3 figure
Yukawa particles confined in a channel and subject to a periodic potential: ground state and normal modes
We consider a classical system of two-dimensional (2D) charged particles,
which interact through a repulsive Yukawa potential ,
confined in a parabolic channel which limits the motion of the particles in the
-direction. Along the -direction, the particles are also subject to a
periodic potential substrate. The ground state configurations and the normal
mode spectra of the system are obtained as function of the periodicity and
strength of the periodic potential (), and density. An interesting set of
tunable ground state configurations are found, with first and second order
structural transitions between them. A magic configuration with particles
aligned in each minimum of the periodic potential is obtained for V_0 larger
than some critical value which has a power law dependence on the density. The
phonon spectrum of different configurations were also calculated. A
localization of the modes into a small frequency interval is observed for a
sufficient strength of the periodic potential. A tunable band-gap is found as a
function of . This model system can be viewed as a generalization of the
Frenkel and Kontorova model.Comment: Submmited to PR
Mapping the Hidden Diversity of the \u3cem\u3eGeophagus sensu stricto\u3c/em\u3e Species Group (Cichlidae: Geophagini) From the Amazon Basin
South American freshwater ichthyofauna is taxonomically the most diverse on the planet, yet its diversity is still vastly underestimated. The Amazon basin alone holds more than half of this diversity. The evidence of this underestimation comes from the backlog of morphologically distinct, yet undescribed forms deposited in museum collections, and from DNA-based inventories which consistently identify large numbers of divergent lineages within even well-studied species groups. In the present study, we investigated lineage diversity within the Geophagus sensu stricto species group. To achieve these objectives, we analyzed 337 individuals sampled from 77 locations within and outside the Amazon basin representing 10 nominal and six morphologically distinct but undescribed species. We sequenced the mitochondrial cytochrome c oxidase subunit I (COI) and delimited lineages using four different single-locus species discovery methods (mPTP-15 lineages; LocMin-14 lineages; bGMYC-18 lineages; and GMYC-30 lineages). The six morphologically distinct but undescribed species were also delimited by the majority of the species discovery methods. Five of these lineages are restricted to a single collection site or a watershed and their habitats are threatened by human activities such as deforestation, agricultural activities and construction of hydroelectric plants. Our results also highlight the importance of combining DNA and morphological data in biodiversity assessment studies especially in taxonomically diverse tropical biotas
Selection of cotton lines for high oil content.
The objective of this work was to evaluate the oil content and characters related to fiber quality and yield in cotton lines (Gossypium hirsutum), in order to select genotypes with high oil content and acceptable levels of the other characters. Twenty-two F6 lines and three checks were cultivated in three field trials ? two in the municipality of Apodi, in the state of Rio Grande do Norte, and one in the municipality of Barbalha, in the state of Ceará, both in Brazil. The genetic parameters and the genetic gain from selecting 20% of the lines were estimated according to their means in each environment and in the group of environments. Regarding oil content, there is genetic variability, and the selection based on the overall mean is indicated, since this character showed high heritability, with 4.58% expected gain. The lines selected with this criterion have oil contents between 23.52 and 24.51%, which are higher than those of the Brazilian cultivar BRS Aroeira with the highest grain oil content (22.04%).Título em português: Seleção de linhagens de algodão para alto teor de óleo
Efeito de um retrocruzamento na média e na variância de uma população de soja.
O objetivo desse trabalho foi avaliar a eficiência de um retrocruzamento para o genitor mais produtivo para a obtenção de linhagens superiores para a produção de grãos (PG) em soja, a partir de um cruzamento biparental. Foram avaliadas experimentalmente 100 progênies de cada um dos dois tipos: progênies F2:4 e progênies RC1F3, em diferentes anos e locais, utilizando o delineamento em látice simples duplicado 10x10 (quatro repetições) e parcelas lineares de 2 m espaçadas de 0,5 m, contendo 30 plantas após o desbaste
Modelagem da cor e dureza do feijão em função das condições de armazenamento.
Stored carioca beans usually tend to darken and harden and therefore lose quality and commercial value and are rejected by the consumer. The objective of this study was to evaluate the behavior of four contrasting light tegument genotypes for the aging process (darkening and hardening) for six months. We adopted a mathematical data modeling, based on polynomial regression analyzes of the variables, color and texture, in the different storage conditions, to describe the effects of the treatment and the storage time, in all bean samples and to select the model which best describes the interaction between variables. All genotypes tended to harden, with increasing storage temperature and time, regardless of the degree of browning. The lowest values of hardness, after six months, were verified in both slow and fast darkening beans. The genotype most resistant to darkening was which showed significant hardening over time. In conclusion, the color itself is not the best parameter to be considered to determine the degree of aging of stored beans, which is controlled by complex mechanisms, physicochemical, genetic, biochemical, among others, which in turn are influenced by environmental storage conditions and genotype
Resistência mecânica à penetração de um argissolo amarelo de tabuleiros costeiros e desenvolvimento radicular de variedades de cana-de-açúcar.
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