Convective Motion in a Vibrated Granular Layer

Experimental results are presented for a vertically shaken granular layer. In the range of accelerations explored, the layer develops a convective motion in the form of one or more rolls. The velocity of the grains near the wall has been measured. It grows linearly with the acceleration, then the growing rate slows down. A rescaling with the amplitude of the wall velocity and the height of the granular layer makes all data collapse in a single curve. This can provide insights on the mechanism driving the motion.Comment: 10 pages, 5 figures submitted to Phys. Rev. Let

Cross-Newell equations for hexagons and triangles

The Cross-Newell equations for hexagons and triangles are derived for general real gradient systems, and are found to be in flux-divergence form. Specific examples of complex governing equations that give rise to hexagons and triangles and which have Lyapunov functionals are also considered, and explicit forms of the Cross-Newell equations are found in these cases. The general nongradient case is also discussed; in contrast with the gradient case, the equations are not flux-divergent. In all cases, the phase stability boundaries and modes of instability for general distorted hexagons and triangles can be recovered from the Cross-Newell equations.Comment: 24 pages, 1 figur

Projecting the Bethe-Salpeter Equation onto the Light-Front and back: A Short Review

The technique of projecting the four-dimensional two-body Bethe-Salpeter equation onto the three-dimensional Light-Front hypersurface, combined with the quasi-potential approach, is briefly illustrated, by placing a particular emphasis on the relation between the projection method and the effective dynamics of the valence component of the Light-Front wave function. Some details on how to construct the Fock expansion of both i) the Light-Front effective interaction and ii) the electromagnetic current operator, satisfying the proper Ward-Takahashi identity, will be presented, addressing the relevance of the Fock content in the operators living onto the Light-Front hypersurface. Finally, the generalization of the formalism to the three-particle case will be outlined.Comment: 16 pages, macros included. Mini-review to be printed in a regular issue of Few-Body Systems devoted to the Workshop on "Relativistic Description of Two- and Three-body Systems in Nuclear Physics" ECT* Trento, 19 - 23 October 200

Antimicrobial Activity of the Extract of Stem Bark of Diplotropis Ferruginea Benth

This is the first report about the antibacterial activity of Diplotropis ferruginea Benth. In this study, the ethanol extract of D. ferruginea was tested for its antimicrobial activity against strains gram-positive and gram-negative. In order to determine the minimal inhibitory concentration, assays were carried out by micro dilution method. The extract was screened for antimicrobial activity, and it showed antibacterial activity against Escherichia coli and Pseudomonas aeruginosa

Genera Euastrum Ehrenberg ex Ralfs and Micrasterias C.Agardh (Conjugatophyceae-Desmidiaceae) from two Amazon black water environments (Manaus,Amazonas-Brazil)

An investigation of genera Euastrum Ehrenberg ex Ralfs and Micrasterias C.Agardh from an Amazon floodplain lake of the Negro river Basin was undertaken. The samples were collected using a plankton net in four stations on the Tupe Lake and one station near a lake on the Negro river. The species were identified and described on the basis of morphological and morphometrical characteristics. A total of 12 species were identified, five species of Euastrum genus (E. evolutum var. perornatum; E. gemmatum var. monocyclum; E. ornans; E. sinuosum; E. spinulosum), and seven of Micrasterias genus (M. borgei; M. radiata var. brasiliensis; M. torreyi; M. laticeps var. acuminata; M. mahabuleshwarensis var. amazonensis; M. rotata var. rotata; M. siolii). All species, except M. radiata Hassal var. brasiliensis Grönblad, were found in the Negro river; on the other hand, only seven species were found in the Tupé lake, three of Euastrum and four of Micrasterias.Foi realizado um inventário das espécies dos gêneros Euastrum Ehrenberg ex Ralfs e Micrasterias C.Agardh de dois ambientes de águas pretas do município de Manaus, um lago de inundação (lago Tupé), e o rio Negro. As coletas foram realizadas com rede de plâncton em quatro estações no lago e uma no rio Negro, situada próxima ao lago. Um total de 93 amostras foi analisado, coletadas em escala mensal no período de março de 2002 a outubro de 2003. As espécies foram descritas e ilustradas com base na sua morfologia e morfometria. Um total de 12 espécies foi identificado, sendo cinco do gênero Euastrum (E. evolutum var. perornatum; E. gemmatum var. monocyclum; E. ornans; E. sinuosum e E. spinulosum), e sete do gênero Micrasterias (M. borgei; M. radiata var. brasiliensis; M. torreyi; M. laticeps var. acuminata; M. mahabuleshwarensis var. amazonensis; M. rotata var. rotata; M. siolii). Todas as espécies, exceto M. radiata Hassal var. brasiliensis Grönblad, foram registradas no rio Negro, enquanto no lago Tupé foi registrado, no geral, apenas sete espécies, três de Euastrum e quatro de Micrasterias