Self-Interacting Electromagnetic Fields and a Classical Discussion on the Stability of the Electric Charge

The present work proposes a discussion on the self-energy of charged particles in the framework of nonlinear electrodynamics. We seek magnet- ically stable solutions generated by purely electric charges whose electric and magnetic fields are computed as solutions to the Born-Infeld equa- tions. The approach yields rich internal structures that can be described in terms of the physical fields with explicit analytic solutions. This suggests that the anomalous field probably originates from a magnetic excitation in the vacuum due to the presence of the very intense electric field. In addition, the magnetic contribution has been found to exert a negative pressure on the charge. This, in turn, balances the electric repulsion, in such a way that the self-interaction of the field appears as a simple and natural classical mechanism that is able to account for the stability of the electron charge.Comment: 8 pages, 1 figur

Aspects of Magnetic Field Configurations in Planar Nonlinear Electrodynamics

In the framework of three-dimensional Born-Infeld Electrodynamics, we pursue an investigation of the consequences of the space-time dimensionality on the existence of magnetostatic fields generated by electric charges at rest in an inertial frame, which are present in its four-dimensional version. Our analysis reveals interesting features of the model. In fact, a magnetostatic field associated with an electric charge at rest does not appear in this case. Interestingly, the addition of the topological term (Chern-Simons) to Born-Infeld Electrodynamics yields the appearance of the magnetostatic field. We also contemplate the fields associated to the would-be-magnetic monopole in three dimensions.Comment: 8 page

Standstill Electric Charge Generates Magnetostatic Field Under Born-Infeld Electrodynamics

The Abelian Born-Infeld classical non-linear electrodynamic has been used to investigate the electric and magnetostatic fields generated by a point-like electrical charge at rest in an inertial frame. The results show a rich internal structure for the charge. Analytical solutions have also been found. Such findings have been interpreted in terms of vacuum polarization and magnetic-like charges produced by the very high strengths of the electric field considered. Apparently non-linearity is to be accounted for the emergence of an anomalous magnetostatic field suggesting a possible connection to that created by a magnetic dipole composed of two mognetic charges with opposite signals. Consistently in situations where the Born-Infeld field strength parameter is free to become infinite, Maxwell`s regime takes over, the magnetic sector vanishes and the electric field assumes a Coulomb behavior with no trace of a magnetic component. The connection to other monopole solutions, like Dirac`s, t' Hooft`s or Poliakov`s types, are also discussed. Finally some speculative remarks are presented in an attempt to explain such fields.Comment: 11 pages, 3 figures. In this version is update a permanent address of the author L.P.G. De Assis and information on submission publication. Submetted to International Journal of Theoretical Physic

Genome Sequence of the Pea Aphid Acyrthosiphon pisum

Aphids are important agricultural pests and also biological models for studies of insect-plant interactions, symbiosis, virus vectoring, and the developmental causes of extreme phenotypic plasticity. Here we present the 464 Mb draft genome assembly of the pea aphid Acyrthosiphon pisum. This first published whole genome sequence of a basal hemimetabolous insect provides an outgroup to the multiple published genomes of holometabolous insects. Pea aphids are host-plant specialists, they can reproduce both sexually and asexually, and they have coevolved with an obligate bacterial symbiont. Here we highlight findings from whole genome analysis that may be related to these unusual biological features. These findings include discovery of extensive gene duplication in more than 2000 gene families as well as loss of evolutionarily conserved genes. Gene family expansions relative to other published genomes include genes involved in chromatin modification, miRNA synthesis, and sugar transport. Gene losses include genes central to the IMD immune pathway, selenoprotein utilization, purine salvage, and the entire urea cycle. The pea aphid genome reveals that only a limited number of genes have been acquired from bacteria; thus the reduced gene count of Buchnera does not reflect gene transfer to the host genome. The inventory of metabolic genes in the pea aphid genome suggests that there is extensive metabolite exchange between the aphid and Buchnera, including sharing of amino acid biosynthesis between the aphid and Buchnera. The pea aphid genome provides a foundation for post-genomic studies of fundamental biological questions and applied agricultural problems

Typification of plant names published by Giovanni Casaretto based on specimens collected in Brazil and Uruguay

International audienceGiovanni Casaretto (1810-1879) was appointed by King Charles Albert of Savoy-Carignano, Kingdom of Sardinia, as the botanist and mineralogist of a planned circumnavigation of the globe. After collecting in a few localities in southern Brazil and Uruguay, Casaretto collected for almost nine months, from April to December 1839, in Rio de Janeiro and its vicinity. While in Rio, he also bought about 100 collections from Riedel and about 500 collections from Clausen, which were made in the states of Rio de Janeiro, Sao Paulo, and Minas Gerais, which he re-numbered and integrated into his collections. He also made significant collections in the state of Bahia, and a few collections in and around Recife (Pernambuco). Based on the preceding collections, Casaretto published a total of 101 names (in 36 plant families, delimited according to APG III), of which, according to the present study, 27 names are currently accepted, 12 serve as basionyms for currently accepted names, 7 are illegitimate due to superfluity, and 55 are heterotypic synonyms of previously published names. All the 101 names of Casaretto are hereby typified, and Eugenia casarettoana Delprete is here proposed as a substitute name for an illegitimate later homonym. In addition, a lectotype and an epitype for Couratari estrellensis Raddi are here designated

Floristic and phytosociological description of a riparian forest and the relationship with the edaphic environment in Caiuá Ecological Station - Paraná - Brazil

Relationship in soil physical and chemical properties of soil, floristic and phytosociological association of semi-deciduous riparian forest of the Paranapanema River (R) and Rosana Reservoir (Re) in the Caiuá Ecological Station were evaluated. Aerial photography and satellite image were used to determine the forest cover and to locate 15 transects 50 x 30m (1500m²),which were used to sample trees with diameters at breast height (DBH)>15 cm. R contained 1487 individuals from 33 families, 64 genders and 73 species. The Shannon-weaver index (H') was 3.318. Re contained 1146 individuals from 35 families, 72 genders and 85 species and the H' was 3.755. There was a statistically significant difference (P<0.05) between R and Re environments and statistically significant correlations (p<0.05) were detected between soil physical attributes and Importance Values (IV) using the Detrended Correspondence Analysis (DCA).<br>Das análises das propriedades física e química dos solos, da florística e da fítossociológica da vegetação arbórea de fragmentos da floresta estacional semidecidual localizados às margens do Rio Paranapanema (R) e do Reservatório de Rosana (Re) na Estação Ecológica do Caiuá (22&deg;41'S e 52&deg;55'W), verificou-se as correlações vegetação x solo. Utilizou-se fotografias aéreas e imagens de satélite para determinar a similaridade da cobertura florestal e alocar 15 transectos de 50m x 30m (1500m²) cada, amostrou-se os indivíduos com perímetro a altura do peito (PAP) 15 cm. No R amostrou-se 1487 indivíduos, de 33 famílias, 64 gêneros e 73 espécies e índice de Shannon-weaver (H') de 3,318. No Re registrou-se 1146 indivíduos de 35 famílias, 72 gêneros e 85 espécies e H' de 3,755. Os resultados mostraram ambientes estatisticamente diferentes e efetiva correlação entre os atributos físicos do solo e os Valores de Importância (VI) ordenados pela Detrended Correspondence Analysis (DCA)