Spin and angular momentum in the nucleon

Using the covariant spectator theory (CST), we present the results of a valence quark-diquark model calculation of the nucleon structure function f(x) measured in unpolarized deep inelastic scattering (DIS), and the structure functions g1(x) and g2(x) measured in DIS using polarized beams and targets. Parameters of the wave functions are adjusted to fit all the data. The fit fixes both the shape of the wave functions and the relative strength of each component. Two solutions are found that fit f(x) and g1(x), but only one of these gives a good description of g2(x). This fit requires the nucleon CST wave functions contain a large D-wave component (about 35%) and a small P-wave component (about 0.6%). The significance of these results is discussed.Comment: 27 pages; 13 figure

Timelike gamma* N -> Delta form factors and Delta Dalitz decay

We extend a covariant model, tested before in the spacelike region for the physical and lattice QCD regimes, to a calculation of the gamma* N -> Delta reaction in the timelike region, where the square of the transfered momentum, q^2, is positive (q^2>0). We estimate the Dalitz decay Delta -> Ne+e- and the Delta distribution mass distribution function. The results presented here can be used to simulate the NN -> NNe+e- reactions at moderate beam kinetic energies.Comment: 14 pages, 11 figure

Variabilidade genética em acessos de mandioca amarela coletadas na Amazônia.

A Amazônia brasileira é conhecida como fonte de variabilidade genética da mandioca. Além disso, costumes locais privilegiaram a conservação de materiais com raiz amarela, rico em carotenóides. O objetivo deste trabalho foi caracterizar uma amostra dos acessos de raiz amarela presentes no BAG da Embrapa Amazônia Oriental. Foram selecionados 18 acessos de mandioca pertencentes ao BAG, sendo 14 materiais com raiz amarela e quatro com raiz branca, por meio de sete locos microssatélites. Todos os locos foram polimórficos, sendo obtido um total de 42 alelos, com média de seis alelos por loco. Quando se avaliou somente as mandiocas amarelas, foram amplificados 36 alelos, com média de 5,12 alelos por loco. A diversidade genética, medida pela heterozigosidade esperada para o grupo das mandiocas amarelas foi de 0,62. O dendrograma não mostrou separação de grupos para as mandiocas, de raiz amarela e raiz branca. No geral, observou-se que é grande a variabilidade genética existente para os materiais de raiz amarela mantidos no BAG da instituição.PIBIC-2011

Emprego de índice de seleção para escolha de populações segregantes de feijoeiro.

Foi realizado o presente trabalho com o objetivo de selecionar populações segregantes do feijoeiro, provenientes de um dialelo, envolvendo pais contrastantes para a arquitetura da planta por meio da padronização das variáveis

Progresso genético após oito ciclos de seleção recorrente para produtividade de grãos do feijoeiro.

O objetivo deste trabalho foi estimar o progresso genético após oito ciclos de seleção recorrente visando à obtenção de linhagens de feijão com alta produtividade

Phenotypic recurrent selection in the common bean ( Phaseolus vulgaris L) with carioca-type grains for resistance to the fungi Phaeoisariopsis griseola.

The efficiency of recurrent selection was assessed in obtaining common bean (Phaseolus vulgaris L) plant lines resistant to the phytopathogenic fungi Phaeoisariopsis griseola. The base bean population was obtained from the partial diallel between seven lines with carioca-type grains and 10 sources of resistance to P. griseola. The plants most resistant to the pathogen were selected in the F2 (S0) generation of the populations (C-0). The best S0:1 plants that presented carioca-type grains were intercrossed to obtain cycle I (C-I). The same procedure was adopted to obtain cycles C-II to C-V. In each recurrent selection cycle, S0:1 progenies selected were also assessed in experiments carried out in Lavras, Brazil, always using as check the Carioca MG (susceptible to P. griseola) and Pérola (tolerant) cultivars. The response to selection for resistance to the pathogen was estimated from the general mean of the S0:1 progenies from each selective cycle compared to the susceptible check Carioca MG. The estimated gain was 6.4% per cycle and the indirect response in grain yield by selection for resistance to the pathogen was 8.9% per cycle. The variability detected among the progenies in the last selective cycles enabled the prediction of additional responses to recurrent selection

Diferenciação genética entre possíveis duplicatas no banco de germoplasma de mandioca da Embrapa Amazônia Oriental por meio de marcadores microssatélites.

PIBIC 2010

Nematode communities from a natural oil seep off Svalbard

Cold-seep sediments, where active fluid seepage rich is observed, have been associated with the presence of endemic nematode communities. Under the scope of the AKMA project, a seep site located offshore Svalbard was sampled for the first time to investigate the Nematoda assemblages associated with methane and crude oil seepage. Replicated samples were collected by means of the blade- and push-cores, on a bacterial mat where active gas and oil seepage was observed, as well as in sediments nearby without evident seepage activity, as reference. Sediments collected were used to characterize the community structure and diversity of the meiofauna taxa, particularly the nematode assemblages, as well as key environmental parameters (i.e, sediment and pore-water geochemistry, organic content, grain size). Preliminary observations showed no major differences in total meiofauna density between microhabitats, with a predominance of nematodes (>90%), followed by harpacticoid copepods and nauplii larvae, as typically seen in other deep-sea environments. However, an in-depth investigation into the nematode assemblages, revealed a low nematode diversity in the bacterial mats sediments, by comparison, to the reference. Bacterial mat-associated assemblages were predominantly composed of Halomonhystera sp.1 (39%), followed by a single Chromadoridae species (32%). Evidence of morphological and reproductive adaptations were observed in several of the species present and could be indicative of how these organisms are able to survive the toxic environmental conditions at this seep site, namely high concentrations of hydrogen sulphide and crude oil. These observations contribute to a large gap in the understanding of how infauna thrive in extreme environments in the Arctic

Excess Thermodynamics of Mixtures Involving Xenon and Light Linear Alkanes by Computer Simulation

Excess molar enthalpies and excess molar volumes as a function of composition for liquid mixtures of xenon + ethane (at 161.40 K), xenon + propane (at 161.40 K) and xenon + n-butane (at 182.34 K) have been obtained by Monte Carlo computer simulations and compared with available experimental data. Simulation conditions were chosen to closely match those of the corresponding experimental results. The TraPPE-UA force field was selected among other force fields to model all the alkanes studied, whereas the one-center Lennard−Jones potential from Bohn et al. was used for xenon. The calculated and for all systems are negative, increasing in magnitude as the alkane chain length increases. The results for these systems were compared with experimental data and with other theoretical calculations using the SAFT approach. An excellent agreement between simulation and experimental results was found for xenon + ethane system, whereas for the remaining two systems, some deviations that become progressively more significant as the alkane chain length increases were observed