Nucleon and gamma N -> Delta lattice form factors in a constituent quark model

A covariant quark model, based both on the spectator formalism and on vector meson dominance, and previously calibrated by the physical data, is here extended to the unphysical region of the lattice data by means of one single extra adjustable parameter - the constituent quark mass in the chiral limit. We calculated the Nucleon (N) and the gamma N -> Delta form factors in the universe of values for that parameter described by quenched lattice QCD. A qualitative description of the Nucleon and gamma N -> Delta form factors lattice data is achieved for light pions.Comment: To appear in J.Phys.

A pure S-wave covariant model for the nucleon

Using the manifestly covariant spectator theory, and modeling the nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four nucleon electromagnetic form factors can be very well described by a manifestly covariant nucleon wave function with zero orbital angular momentum. Since the concept of wave function depends on the formalism, the conclusions of light-cone theory requiring nonzero angular momentum components are not inconsistent with our results. We also show that our model gives a qualitatively correct description of deep inelastic scattering, unifying the phenomenology at high and low momentum transfer. Finally we review two different definitions of nuclear shape and show that the nucleon is spherical in this model, regardless of how shape is defined.Comment: 20 pages and 10 figures; greatly expanded version with new fits and discussion of DIS; similar to published versio

Occurrence of 15 haplotypes of linepithema micans (Hymenoptera: Formicidae) in southern Brazil.

The ant genus Linepithema is widely known, thanks to the pest species Linepithema humile (Mayr), which is easily mistaken for Linepithema micans (Forel) due to their morphological similarity. Like L. humile , L. micans is associated to the main grapevine pest in Brazil, Eurhizococcus brasiliensis (Wille), also known as ground pearl. Therefore, the present study uses mtDNA fragments to expand the knowledge of haplotype diversity and distri- bution of L. micans in the state of Rio Grande do Sul Brazil), to understand the genetic differences of the popu- lations identified in this study. We identified 15 haplotypes of L. micans spread across different localities. Twelve of these haplotypes were new for the species. The high haplotype diversity uncovered in Rio Grande do Sul (Brazil) for this species was predictable, as L. micans is in its native environment. Additional studies that take gene flow into account may reveal interesting aspects of diversity in these populations. Keywords: mitotype, ground pearl, Rio Grande do Su

Megafauna communities from abyssal sites along the Gloria Fracture Zone (NE Atlantic)

Fracture zones are areas of poorly known abyssal landscapes and benthic faunal communities. During the R/V Meteor M162 cruise several imagery surveys were performed using a TV-CTD guided camera system along four main areas of the Gloria fault system, between the Terceira ridge and the Madeira Tore Rise. Based on these records, we were able to characterize - for the first time - the megafaunal composition, their abundance and diversity along the sub-basin of the Gloria fault at depths between 3500 and 4500m. Quantitative annotations of the observed fauna, as well as evidence of animal traces on the seafloor were explored in relation to topography, substrate type, and geochemical data acquired during surveys. Preliminary observations revealed a total of 121 morphospecies, of which Holothuroidea is the most diverse group, with 12 morphospecies. Deepest transects carried out along the main trace of Gloria Fault system showed the highest similarity among dives, predominantly characterised by soft sediment areas with Elpidiidae holothurians frequently observed. In contrast, the survey carried out at the Terceira ridge showed more diverse communities, which is likely due to a larger variability in substrate and topography. Specifically, soft-sediment sections showed a higher proportion of holothurians, ophiuroids and acorn worms, while unique Anthozoan and Porifera morphospecies were observed in areas with presence of hard substrates. The findings of this study provide unique knowledge of abyssal fauna associated with the Gloria Fault System, including areas inside of national jurisdiction and of relevance for management and conservation actions

Occurrence of marine litter along abyssal areas of the Gloria Fracture Zone (NE Atlantic).

Marine litter pollution is a recognized form of anthropogenic disturbance that affects widely the marine environment, particularly near the continental margins, although also present at abyssal and bathyal depths. This study reports the occurrence of marine litter distribution and abundance in four abyssal basins along the Gloria fracture zone in the NE Atlantic. Litter items occurrences were analysed using TV-CTD video surveys carried out during the multidisciplinary activities of the R/V Meteor M162 cruise. The surveys reached depths between 3500-4500m and covered 16 km of seafloor, between the Terceira ridge and the Madeira-Tore Rise. Litter items were annotated and categorized by type (i.e., plastic, fishing gear, metal, glass, other unknown items). Results revealed that litter was exclusively found on soft sediment habitats across all areas, i.e. depositional areas, with the overwhelming dominance of plastics items (71%), such as plastic containers, cups and bag fragments. Although less common (6-8%), metal, glass and lost fishing gear were also observed. Litter density was on average 9 times higher in the easternmost area near the Madeira-Tore ridge, when compared to the other areas. Higher litter densities are likely explained due to the proximity to the Madeira-Tore seamount complex targeted by the fishing industry and nearimportant corridors of marine traffic between various Atlantic and Mediterranean locations

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

Role of a Transbilayer pH Gradient in the Membrane Fusion Activity of the Influenza Virus Hemagglutinin: Use of the R18 Assay to Monitor Membrane Merging

It had been suggested that influenza virus-mediated membrane fusion might be dependent on a pH gradient across a target membrane. We have designed experiments in which this issue could be addressed. Two populations of liposomes were prepared, both simulating the plasma membrane of target cells, but with the pH of the internal aqueous medium buffered either at pH 7.4 (physiological cytosol pH) or at pH 5.0 (endosomal pH at which influenza virus displays maximal fusion activity). By monitoring fusion using the R18 assay, we found that the internal pH of the target liposomes did not influence membrane merging as mediated by the influenza virus hemagglutinin, thus demonstrating that a transmembrane pH gradient is not required in this fusion process