Wang-Landau sampling in three-dimensional polymers

Monte Carlo simulations using Wang-Landau sampling are performed to study three-dimensional chains of homopolymers on a lattice. We confirm the accuracy of the method by calculating the thermodynamic properties of this system. Our results are in good agreement with those obtained using Metropolis importance sampling. This algorithm enables one to accurately simulate the usually hardly accessible low-temperature regions since it determines the density of states in a single simulation.Comment: 5 pages, 9 figures arch-ive/Brazilian Journal of Physic

Germinação de sementes de pau-de-balsa (Ochroma pyramidale (Cav.) Urb.) - Bombacaceae.

O teste de germinação de sementes de Ochrma pyramidale (Cav.) Urb. foirealizado a temperaturas 20°, 25°, 30°, 20°_ 30° e 25°_ 35°C e substratos papel de filtro, areia, venniculita e rolo de papel com seis repetições de 50 sementes. Para a superação de dormência das sementes utilizou-se escarificação mecânica, embebição em água oxigenada e água fervente. Recomenda-se a germinação de sementes de pau-de-balsa em papel de filtro a temperatura de 30°C após imersão em água fervente por 4 minutos

Demandas de serviços no Laboratório de Análises de Sementes da Embrapa Milho e Sorgo (CNPMS) Sete Lagoas, MG.

Edição dos resumos do 18º Congresso Brasileiro de Sementes, 2013, Florianópolis

A cultura do milheto.

bitstream/item/58830/1/ct-11-1.pd

Exchange Narrowing Effects in the EPR Linewidth of Gd Diluted in Ce Compounds

Anomalous thermal behavior on the EPR linewidths of Gd impurities diluted in Ce compounds has been observed. In metals, the local magnetic moment EPR linewidth, \Delta H, is expected to increase linearly with the temperature. In contrast, in Ce_{x}La_{1-x}Os_{2} the Gd EPR spectra show a nonlinear increase. In this work, the mechanisms that are responsible for the thermal behavior of the EPR lines in Ce_{x}La_{1-x}Os_{2} are examined. We show that the exchange interaction between the local magnetic moments and the conduction electrons are responsible for the narrowing of the spectra at low temperatures. At high temperatures, the contribution to the linewidth of the exchange interaction between the local magnetic moments and the $Ce$ ions has an exponential dependence on the excitation energy of the intermediate valent ions. A complete fitting of the EPR spectra for powdered samples is obtained.Comment: 11 pages, 1 figur

Seasonal dynamics of benthic communities in a shallow sublitoral site of Laguna estuarine system (South, Brazil)

The seasonal variability of the benthic community in a shallow sublittoral site was analyzed at the Laguna Estuarine System, a chocked lagoon in South Brazil. Seasonal replicate samples for the microphytobenthos, meiofauna and macrofauna were undertaken from October 2003 to October 2004. The analysis of the different component of the benthos permitted to show a clear temporal asynchrony in the microphytobenthos biomass, meiofauna and macrofauna univariate measures increase and decline. Sediment chlorophyll a and phaeopigments followed a similar seasonal trend, with low biomass in the winter, higher in the summer and intermediate values in spring and autumn. The benthic fauna components of the Laguna Estuarine System also showed a clear seasonal oscillation, but with an opposite pattern of variation. Whilst the number of species and abundance of the macrofauna were significantly higher in the spring and summer, for the meiofauna, both the number of taxa and abundances were significantly higher during the winter and autumn. The results of this study suggested that the divergent seasonal variations of the meiofauna and macrofauna may be linked to their different life strategies, and that biological interactions between meiofauna and macrofauna may also play a significant role in structuring these communites.The seasonal variability of the benthic community in a shallow sublittoral site was analyzed at the Laguna Estuarine System, a chocked lagoon in South Brazil. Seasonal replicate samples for the microphytobenthos, meiofauna and macrofauna were undertaken from October 2003 to October 2004. The analysis of the different component of the benthos permitted to show a clear temporal asynchrony in the microphytobenthos biomass, meiofauna and macrofauna univariate measures increase and decline. Sediment chlorophyll a and phaeopigments followed a similar seasonal trend, with low biomass in the winter, higher in the summer and intermediate values in spring and autumn. The benthic fauna components of the Laguna Estuarine System also showed a clear seasonal oscillation, but with an opposite pattern of variation. Whilst the number of species and abundance of the macrofauna were significantly higher in the spring and summer, for the meiofauna, both the number of taxa and abundances were significantly higher during the winter and autumn. The results of this study suggested that the divergent seasonal variations of the meiofauna and macrofauna may be linked to their different life strategies, and that biological interactions between meiofauna and macrofauna may also play a significant role in structuring these communites

Shallow sublittoral benthic communities of the Laguna Estuarine System, South Brazil

Propriedades do sedimento, biomassa microfitobêntica (clorofila a e feopigmentos), e a estrutura das comunidades bênticas das três principais lagoas (Mirim, Imaruí e Santo Antonio) do Sistema Estuarino de Laguna, sul do Brasil, foram analisadas durante o verão e inverno. A biomassa microfitobêntica não diferiu significativamente entre as lagoas, mas seus valores foram maiores no verão. A macrofauna foi caracterizada pela baixa riqueza específica e a dominância do gastrópode Heleobia australis, do tanaidáceo Kalliapseudes schubartti e do bivalve Erodona mactroides. A meiofauna foi composta por 20 grupos taxonômicos e os nemátodas dominaram todas as lagoas e períodos. Desmodora (Desmodora) sp.1, Terschllingia sp. e Microlaimus sp. foram numericamente as mais importantes entre as 74 espécies de nemátodas registradas. Este estudo mostrou que, no Sistema Estuarino de Laguna, as diferenças no bentos entre as lagoas e períodos foram dependentes do componente faunístico analisado. Enquanto macrofauna e nemátodas foram significativamente mais diversos nas áreas interiores, na Lagoa Mirim, o número de taxa da meiofauna não diferiu significativamente entre as lagoas e a diversidade e equitatividade foram maiores em Santo Antonio. Estes resultados foram uma resposta da fauna às variações de salinidade e da heterogeneidade do sedimento das lagoas. A variabilidade temporal da fauna, sendo a macrofauna mais abundante no verão e a meiofauna no inverno, pode estar relacionada as diferentes estratégias de vida destes grupos.Sediment properties, microphytobenthos biomass (chlorophyll a and phaeopigments), and the structure of the benthic communities of the three main lagoons (Mirim, Imaruí and Santo Antonio) of the Laguna Estuarine System, South Brazil, were analyzed during summer and winter. Microphytobenthos biomass did not differ significantly among the lagoons, but showed higher values in the summer. The macrofauna was characterized by low species richness and the dominance of the gastropod Heleobia australis, the tanaidean Kalliapseudes schubartti and the bivalve Erodona mactroides. The meiofauna was composed of 20 higher taxa and the nematodes dominated in all the lagoons and periods. Desmodora (Desmodora) sp.1, Terschllingia sp. and Microlaimus sp. were numerically the most important among the 74 nematode species registered. This study showed that, in the Laguna Estuarine System, differences in the benthos among lagoons and periods were dependent on the fauna component analyzed. Whilst macrofauna and nematodes were significantly more diverse in the inner stations, in the Mirim Lagoon, the number of meiofauna taxa did not differ significantly among the lagoons and the diversity and evenness were highest in Santo Antonio. These results were a response of the fauna to the salinity oscillations coupled with the heterogeneity of the sediment in the lagoons. The temporal variability of the fauna, macrofauna being more abundant in the summer and meiofauna in the winter, could be related to the different life strategies of these groups