Topics in Born-Infeld Electrodynamics

Classical version of Born-Infeld electrodynamics is recalled and its most important properties discussed. Then we analyze possible abelian and non-abelian generalizations of this theory, and show how certain soliton-like configurations can be obtained. The relationship with the Standard Model of electroweak interactions is also mentioned.Comment: (One new reference added). 15 pages, LaTeX. To be published in the Proceedings of XXXVII Karpacz Winter School edited in the Proceedings Series of American Mathematical Society, editors J. Lukierski and J. Rembielinsk

Mass Generation from Lie Algebra Extensions

Applied to the electroweak interactions, the theory of Lie algebra extensions suggests a mechanism by which the boson masses are generated without resource to spontaneous symmetry breaking. It starts from a gauge theory without any additional scalar field. All the couplings predicted by the Weinberg-Salam theory are present, and a few others which are nevertheless consistent within the model.Comment: 11 pages; revtex; title and PACS have been changed; comments included in the manuscrip

Confronting cold dark matter cosmologies with strong clustering of Lyman break galaxies at z∼3z\sim3

We perform a detailed analysis of the statistical significance of a concentration of Lyman break galaxies at $z \sim 3$ recently discovered by Steidel et al. (1997), using a series of N-body simulations with $N=256^3$ particles in a (100\himpc)^3 comoving box. While the observed number density of Lyman break galaxies at $z\sim3$ implies that they correspond to systems with dark matter halos of \simlt 10^{12}M_\odot, the resulting clustering of such objects on average is not strong enough to be reconciled with the concentration if it is fairly common; we predict one similar concentration approximately per ($6\sim 10$) fields in three representative cold dark matter models. Considering the current observational uncertainty of the frequency of such clustering at $z\sim3$, it would be premature to rule out the models, but the future spectroscopic surveys in a dozen fields could definitely challenge all the existing cosmological models a posteriori fitted to the $z=0$ universe.Comment: the final version which matchs that published in ApJ Letters (Feb 1998); compared with the previous versions, the predictions for the SCDM model are slightly changed; Latex, 11 pages, including 3 ps figure

Experimental analysis of lateral impact on planar brittle material: spatial properties of the cracks

The breakup of glass and alumina plates due to planar impacts on one of their lateral sides is studied. Particular attention is given to investigating the spatial location of the cracks within the plates. Analysis based on a phenomenological model suggests that bifurcations along the cracks' paths are more likely to take place closer to the impact region than far away from it, i. e., the bifurcation probability seems to lower as the perpendicular distance from the impacted lateral in- creases. It is also found that many observables are not sensitive to the plate material used in this work, as long as the fragment multiplicities corresponding to the fragmentation of the plates are similar. This gives support to the universal properties of the fragmentation process reported in for- mer experiments. However, even under the just mentioned circumstances, some spatial observables are capable of distinguishing the material of which the plates are made and, therefore, it suggests that this universality should be carefully investigated

Vapour reactive distillation process for hydrogen production by hi decomposition from hi-i2-h2o solutions

In this contribution, a sequential and hierarchical approach for the feasibility analysis and the preliminary design of reactive distillation columns is extended to systems involving vapour phase chemical reaction and is successfully applied to the HI vapour phase decomposition to produce H2. The complex phase and physico chemical behaviour of the quaternary HI-H2-I2-H2O system is represented by the Neumann’s thermodynamic model and instantaneous vapour phase chemical equilibrium is assumed. Then, from minimal information concerning the physicochemical properties of the system, three successive steps lead to the design of the unit and the specification of its operating conditions: the feasibility analysis, the synthesis and the design step. First, the analysis of reactive condensation curve map method (rCCM), assuming infinite internal liquid and vapour flow rate and infinite reflux ratio, is used to assess the feasibility of the process. It determines the column structure and estimates the attainable compositions. These results are used as inputs data for the synthesis step. Based on the boundary value design method (BVD), considering finite internal liquid and vapour flow rate and finite reflux ratio while neglecting all thermal effects and assuming a constant heat of vaporisation, the synthesis step provides more precise information about the process configuration (minimum reflux ratio, number of theoretical stages, localisation and number of reactive plates, position of the feed plate). Finally, the BVD method results are used to initialise rigorous simulations, based on an equilibrium stage model with energy balance, to estimate the reflux ratio taking into account thermal effect on the process. The resulting design configuration consists in a single feed and entirely reactive distillation column. The column operates under a pressure of 22 bars. The feed of the reactive distillation column, coming from the Bunsen reaction section [xHI=0.10; xI2=0.39 xH2O=0.51], is at its boiling temperature. The residue consists in pure iodine. Water and produced hydrogen are recovered at the distillate. The column operates at a reflux ratio of 5 and is composed of 11 theoretical plates including the reboiler and the partial condenser with the feed at the stage 10 (counted downwards). The obtained HI dissociation yield is 99.6%

The genus M alanea Aubl. (Rubiaceae, Guettardeae) in the Brazilian Amazon - species distribution and collection gaps

The Brazilian Amazon is the largest and richest tropical forest in the world. However, its biodiversity is still underestimated and severely threatened by deforestation. Malanea Aubl. (Rubiaceae, Guettardeae) is a neotropical genus of about 40 species, 15 of which occur in Brazil. This study aims to present species distributions and gaps in collections ofthis genus in the Brazilian Amazon. We collected occurrence records in the online databases Herbário Virtual Reflora (http:// reflora.jbrj.gov.br/reflora/herbarioVirtual/) and Herbário Virtual da Flora e Fungos do Brasil (https://specieslink.net/). After sorting and cleaning, data were plotted in QGIS 3.28 software to visualize the distribution of species and collection sites. 167 records of 11 species (Malanea auyantepuiensis Steyerm .,M duckei Standl.,M egleri Steyerm., M. gabrielensis M üll.Arg.,M hypoleuca Steyerm., M. macrophylla Bartl. ex G riseb.,M microphylla Standl. ex Steyerm., M. obovata H orch.,M panurensis M üll.Arg.,M sarmentosa Aubl., a n d M subtruncata Steyerm.) were found in the Brazilian Amazon, with Malanea auyantepuiensis being a new record. Malanea macrophylla, M. gabrielensis, and M. sarmentosa have more than 30 records well distributed in the región. The other species have two to ten collections. The State o f Amazonas, with seven species registered, can be considered the center o f diversity o f the genus in the Brazilian Amazon. The región bordering the Guiana Shield has six species, M. egleri, M. hypoleuca, M. macrophylla, M. microphylla, M. obovata, and M. panurensis. We highlight a concentration o f collection points in regions cióse to urban centres. The low sampling o f most species limits systematics and biogeographic studies o f the genus. Therefore, we emphasize the need to expand the sampling o f Malanea in the Brazilian Amazon. Understanding the mechanisms that influence the lineage diversification process in the Amazon may allow us to anticipate and/or mitigate the loss of biodiversity in this domain

Concentrações plasmaticas de testosterona e suas relações com características reprodutivas em touros das raças Canchim e Nelore.

Níveis plasmaticos de testosterona foram determinados em 7 touros da raça canchim e 8 touros da raça nelore, aos 27 e 39 meses de idade.Resumo

Comportamento sexual de touros das raças Canchim e Nelore.

O comportamento sexual foi avaliado em sete touros da raça Canchim e oito Nelores aos 27 e 29 meses de idade, através dos testes de libido, capacidade de serviço e tempo de reação

Deficiências minerais em pastagens do Estado do Rio de Janeiro.

bitstream/item/65349/1/CTAA-DOCUMENTOS-8-DEFICIENCIAS-MINERAIS-EM-PASTAGENS-DO-ESTADO-DO-RIO-DE-JANEIRO-FL-02171.pd