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

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

Procedimentos para Recuperação Edáfica de Margens de Corpos d'Água em Zonas Urbanas.

bitstream/CNPDIA/10473/1/CT64_2005.pd

Structural Evidence for a Copper-Bound Carbonate Intermediate in the Peroxidase and Dismutase Activities of Superoxide Dismutase

Copper-zinc superoxide dismutase (SOD) is of fundamental importance to our understanding of oxidative damage. Its primary function is catalysing the dismutation of superoxide to O2 and H2O2. SOD also reacts with H2O2, leading to the formation of a strong copper-bound oxidant species that can either inactivate the enzyme or oxidise other substrates. In the presence of bicarbonate (or CO2) and H2O2, this peroxidase activity is enhanced and produces the carbonate radical. This freely diffusible reactive oxygen species is proposed as the agent for oxidation of large substrates that are too bulky to enter the active site. Here, we provide direct structural evidence, from a 2.15 Å resolution crystal structure, of (bi)carbonate captured at the active site of reduced SOD, consistent with the view that a bound carbonate intermediate could be formed, producing a diffusible carbonate radical upon reoxidation of copper. The bound carbonate blocks direct access of substrates to Cu(I), suggesting that an adjunct to the accepted mechanism of SOD catalysed dismutation of superoxide operates, with Cu(I) oxidation by superoxide being driven via a proton-coupled electron transfer mechanism involving the bound carbonate rather than the solvent. Carbonate is captured in a different site when SOD is oxidised, being located in the active site channel adjacent to the catalytically important Arg143. This is the probable route of diffusion from the active site following reoxidation of the copper. In this position, the carbonate is poised for re-entry into the active site and binding to the reduced copper. © 2012 Strange et al

HPC Cloud for Scientific and Business Applications: Taxonomy, Vision, and Research Challenges

High Performance Computing (HPC) clouds are becoming an alternative to on-premise clusters for executing scientific applications and business analytics services. Most research efforts in HPC cloud aim to understand the cost-benefit of moving resource-intensive applications from on-premise environments to public cloud platforms. Industry trends show hybrid environments are the natural path to get the best of the on-premise and cloud resources---steady (and sensitive) workloads can run on on-premise resources and peak demand can leverage remote resources in a pay-as-you-go manner. Nevertheless, there are plenty of questions to be answered in HPC cloud, which range from how to extract the best performance of an unknown underlying platform to what services are essential to make its usage easier. Moreover, the discussion on the right pricing and contractual models to fit small and large users is relevant for the sustainability of HPC clouds. This paper brings a survey and taxonomy of efforts in HPC cloud and a vision on what we believe is ahead of us, including a set of research challenges that, once tackled, can help advance businesses and scientific discoveries. This becomes particularly relevant due to the fast increasing wave of new HPC applications coming from big data and artificial intelligence.Comment: 29 pages, 5 figures, Published in ACM Computing Surveys (CSUR

Efeito da temperatura de condicionamento sobre a digestibilidade da proteina bruta e metabolizabilidade de dietas para frangos de corte.

Sabe-se que o tratamento térmico do alimento pode melhorar seu aproveitamento, sendo a influência do processamento sobre a digestibilidade o principal modo de ação (4). A peletização da ração aumenta a digestibilidade das frações da dieta pela ação mecânica e pela temperatura do processo. Os processos térmicos também promovem alterações das estruturas terciárias naturais das proteínas, facilitando sua digestão (2). A peletização proporciona um aumento do valor energético dos nutrientes, sendo uma alternativa viável para dietas de frangos de corte em termos de aumento da energia metabolizável da dieta. Com isso, objetivou-se avaliar o efeito de diferentes temperaturas de condicionamento sobre o coeficiente de metabolizabilidade aparente da matéria seca (CMAMS) e o coeficiente de digestibilidade aparente da proteína bruta (CDPBap)