Relativistically rotating dust

Dust configurations play an important role in astrophysics and are the simplest models for rotating bodies. The physical properties of the general--relativistic global solution for the rigidly rotating disk of dust, which has been found recently as the solution of a boundary value problem, are discussed.Comment: 18 pages, 11 figure

Genetic variation in growth, hormonal and seminal traits of young tropically adapted bulls

Except for scrotal circumference there is little published information on the genetic variation of traits measured on young tropical breed bulls. The current study assesses growth, hormonal and seminal traits measured in Brahman and tropical Composite bulls (n=2212) from weaning through to 2 years. Heritability of scrotal size (39 to 75%), prepubertal serum concentration of inhibin (40 to 71%) and semen quality traits (19 to 27%) indicated potential to genetically improve these traits in both Brahman and tropical Composite populations. Genetic correlations between male traits varied (-46 to 78%), some suggesting antagonism between traits while others indicated that some traits measured in bulls early in life could potentially be indicators of post-pubertal semen quality

Spawning areas, dispersion and microhabitats of fish larvae in the Anavilhanas Ecological Station, rio Negro, Amazonas State, Brazil

The abundance and distribution of ichthyoplankton and their relationships to current velocity, temperature, dissolved oxygen, pH and electrical conductivity of the water in the Anavilhanas Ecological Station, Negro River, Amazonas State, Brazil, were analyzed. Preferred microhabitats for spawning, dispersion and nursery were also verified. Sampling was undertaken during the falling water period of 2001 and the rising water period of 2002, in a section of 100 km subdivided into 5 subsections, with a total of 20 stations (5 beaches, 5 ravines, 5 channels, and 5 lake channels) at night and during the day at the surface and at the bottom. 647 eggs and 4,187 larvae were captured, belonging to 10 families and four orders: Characiformes (6), Siluriformes (2), Perciformes (1), and Clupeiformes (1). Engraulidae (55.39%), Pimelodidae (30.45%), Auchenipteridae (5.23%) and Sciaenidae (5.13%) were the dominant families. The hierarchical statistical model (ANOVA) with three factors (microhabitat, depth and period) was applied to the environmental variables and the larval abundance, showing greater abundances of sciaenids in the ravines and lower abundances of engraulids in the channels. The highest captures were obtained at lower temperature values, at the bottom during the day and at the surface at night, suggesting an active larval behavior. The presence of the four larval development stages in all subsection for pimelodids and sciaenids, and in three subsections for engraulids, indicates that the Anavilhanas Ecological Station is an important spawning and nursery area for species of these groups in the Negro River. Larvae abundance of all characiform families was extremely low (from 0.1 to 1.17%), suggesting that they do not spawn in this system