2,179 research outputs found
A supercritical series analysis for the generalized contact process with diffusion
We study a model that generalizes the CP with diffusion. An additional
transition is included in the model so that at a particular point of its phase
diagram a crossover from the directed percolation to the compact directed
percolation class will happen. We are particularly interested in the effect of
diffusion on the properties of the crossover between the universality classes.
To address this point, we develop a supercritical series expansion for the
ultimate survival probability and analyse this series using d-log Pad\'e and
partial differential approximants. We also obtain approximate solutions in the
one- and two-site dynamical mean-field approximations. We find evidences that,
at variance to what happens in mean-field approximations, the crossover
exponent remains close to even for quite high diffusion rates, and
therefore the critical line in the neighborhood of the multicritical point
apparently does not reproduce the mean-field result (which leads to )
as the diffusion rate grows without bound
Germinação e vigor de sementes de melancia com diferentes ploidias submetidas a tratamentos pré-germinativos.
Sementes triplóides e tetraplóides de melancia apresentam problemas de germinação, havendo a necessidade do emprego de tratamentos visando minimizar este problema. Técnicas para melhorar a germinação são importantes para aumentar o potencial de desempenho das sementes e, por conseguinte, a uniformidade das plantas em condições de campo. O presente trabalho teve como objetivo verificar o efeito de tratamentos pré-germinativos em sementes diplóides, triplóides e tetraplóides de melancia. As sementes foram submetidas à maceração; escarificação mecânica + ácido giberélico (GA3); escarificação; ácido giberélico (GA3). Após a aplicação dos tratamentos, as sementes foram colocadas para germinar em rolos de papel germitest embebido com água destilada na proporção de 2,5 vezes seu peso e mantidas em germinador à temperatura de 25°C. Foram realizadas avaliações de porcentagem de germinação e crescimento de plântulas aos 5 e 12 dias. A avaliação da emergência de plântulas foi realizada no interior de uma casa-de-vegetação coberta com sombrite 50%, em bandejas plásticas com solo. Foram realizadas contagens diárias do número de plântulas emergidas até a estabilização da emergência das mesmas, considerando-se emergidas aquelas que apresentavam os cotilédones expostos. Foram determinadas as porcentagens de emergência e o índice de velocidade de emergência de plântulas. Apesar dos tratamentos prégerminativos empregados nos três tipos de sementes não serem eficientes no aumento da germinação e emergência de plântulas de melancia, observou-se que o GA3 e a escarificação, empregados separadamente e em associação, promoveram maior crescimento de plântulas oriundas de sementes diplóides e tetraplóides e que a maceração também contribuiu para maior crescimento de plântulas tetraplóides
Surface Effects on the Mechanical Elongation of AuCu Nanowires: De-alloying and the Formation of Mixed Suspended Atomic Chains
We report here an atomistic study of the mechanical deformation of AuxCu(1-x)
atomic-size wires (NWs) by means of high resolution transmission electron
microscopy (HRTEM) experiments. Molecular dynamics simulations were also
carried out in order to obtain deeper insights on the dynamical properties of
stretched NWs. The mechanical properties are significantly dependent on the
chemical composition that evolves in time at the junction; some structures
exhibit a remarkable de-alloying behavior. Also, our results represent the
first experimental realization of mixed linear atomic chains (LACs) among
transition and noble metals; in particular, surface energies induce chemical
gradients on NW surfaces that can be exploited to control the relative LAC
compositions (different number of gold and copper atoms). The implications of
these results for nanocatalysis and spin transport of one-atom-thick metal
wires are addressed.Comment: Accepted to Journal of Applied Physics (JAP
Qualidade de mudas de melão produzidas em diferentes substratos.
The aim of this paper was to evaluate the development of melon seedlings grown in different substrates. The experiment was carried out in a greenhouse covered with 25% screen, at the Department of Technology and Social Sciences -DTCS of the University of the State of Bahia / UNEB, Juazeiro-BA, from July to August 2005. It was used a completely randomized experimental design with six treatments and four replications, each one consisted of 50 seedlings. The treatments composed of the substrates: Plantmax HT©; soil; sterilized soil; sugarcane residue; sugarcane residue + soil (1:1) and sugarcane residue + urea. Polystyrene trays of 200 cells were used as containers, where seeds of the AF882 melon cultivar. We sowed at 1 cm depth, using one seed per cell. The emergence percentage, average emergence time and average emergence velocity were determined. Fourteen days after sowing were evaluated seedling height, shoot and toot fresh and dry masses leaf area and chlorophyll content. The results allow one to conclude that the commercial substrate Plantmax HT© and the sterilized soil were those that provided the best melon seedlings formation
Germinação de acessos de araçá em diferentes fases de maturação fisiológica e tempo de secagem.
O objetivo deste trabalho foi avaliar o potencial germinativo de sementes de araçá nas fases de maturação fisiológica de frutos imaturos e maduros após 0 e 24h de secagem de sementesEdição dos Anais do 1 Simpósio da Rede de Recursos Genéticos Vegetais do Nordeste, Cruz das Almas, nov. 2013
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
Germinação de sementes de pimenta-rosa (Schinus terebinthifolius raddi) submetidas a diferentes temperaturas.
O presente trabalho tem como objetivo, avaliar o comportamento germinativo de sementes de pimenta-rosa quando submetidas a diferentes temperaturas. As sementes utilizadas foram coletadas no mês de setembro de 2009 de uma população existente próximo à Universidade de Brasília, Brasilia-DF. A semeadura foi feita separadamente em caixas tipo gerbox sob papel mata-borrão umedecido com 15mL de água, posteriormente as caixas foram incubadas em uma BOD sob diferentes temperaturas (20, 25, 30, 25/30°C) durante 15 dias onde foi avaliado diariamente a porcentagem de germinação, ao final do experimento foram calculados, o tempo médio de germinação, velocidade de germinação, indice de velocidade de germinação (IVG)
- …