Multicomponent adsorption on activated carbons under supercritical conditions

Adsorption of binary mixtures onto activated carbon Norit R1 for the system nitrogen-methane-carbon dioxide was investigated over the pressure range up to 15 MPa. A new model is proposed to describe the experimental data. It is based on the assumption that an activated carbon can be characterized by the distribution function of elements of adsorption volume (EAV) over the solid-fluid potential. This function may be evaluated from pure component isotherms using the equality of the chemical potentials in the adsorbed phase and in the bulk phase for each EAV. In the case of mixture adsorption a simple combining rule is proposed, which allows determining the adsorbed phase density and its composition in the EAV at given pressure and compositions of the bulk phase. The adsorbed concentration of each adsorbate is the integral of its density over the set of EAV. The comparison with experimental data on binary mixtures has shown that the approach works reasonably well. In the case of high-pressure binary mixture adsorption, when only total amount adsorbed was measured, the proposed model allows reliably determining partial amounts of the adsorbed components. (C) 2004 Elsevier Inc. All rights reserved.

Fast accumulation of few polyhedra mutants during passage of a Spodoptera frugiperda multicapsid nucleopolyhedrovirus (Baculoviridae) in Sf9 cell cultures

Baculoviruses are a group of viruses that infect invertebrates and that have been used worldwide as a biopesticide against several insect pests of the Order Lepidoptera. In Brazil, the baculovirus Spodoptera frugiperda multicapsid nucleopolyhedrovirus (SfMNPV, Baculoviridae) has been used experimentally to control S. frugiperda (Lepidoptera: Noctuidae), an important insect pest of corn (maize) fields and other crops. Baculoviruses can be produced either in insect larvae or in cell culture bioreactors. A major limitation to the in vitro production of baculoviruses is the rapid generation of mutants when the virus undergoes passages in cell culture. In order to evaluate the potential of in vitro methods of producing SfMNPV on a large-scale, we have multiplied a Brazilian isolate of this virus in cell culture. Extensive formation of few polyhedra mutants was observed after only two passages in Sf9 cells.

Parallel evolution of sexual isolation in sticklebacks

Mechanisms of speciation are not well understood, despite decades of study. Recent work has focused on how natural and sexual selection cause sexual isolation. Here, we investigate the roles of divergent natural and sexual selection in the evolution of sexual isolation between sympatric species of threespine sticklebacks. We test the importance of morphological and behavioral traits in conferring sexual isolation and examine to what extent these traits have diverged in parallel between multiple, independently evolved species pairs. We use the patterns of evolution in ecological and mating traits to infer the likely nature of selection on sexual isolation. Strong parallel evolution implicates ecologically based divergent natural and/or sexual selection, whereas arbitrary directionality implicates nonecological sexual selection or drift. In multiple pairs we find that sexual isolation arises in the same way: assortative mating on body size and asymmetric isolation due to male nuptial color. Body size and color have diverged in a strongly parallel manner, similar to ecological traits. The data implicate ecologically based divergent natural and sexual selection as engines of speciation in this group.

Ecological speciation

Ecological processes are central to the formation of new species when barriers to gene flow (reproductive isolation) evolve between populations as a result of ecologically-based divergent selection. Although laboratory and field studies provide evidence that 'ecological speciation' can occur, our understanding of the details of the process is incomplete. Here we review ecological speciation by considering its constituent components: an ecological source of divergent selection, a form of reproductive isolation, and a genetic mechanism linking the two. Sources of divergent selection include differences in environment or niche, certain forms of sexual selection, and the ecological interaction of populations. We explore the evidence for the contribution of each to ecological speciation. Forms of reproductive isolation are diverse and we discuss the likelihood that each may be involved in ecological speciation. Divergent selection on genes affecting ecological traits can be transmitted directly (via pleiotropy) or indirectly (via linkage disequilibrium) to genes causing reproductive isolation and we explore the consequences of both. Along with these components, we also discuss the geography and the genetic basis of ecological speciation. Throughout, we provide examples from nature, critically evaluate their quality, and highlight areas where more work is required.

Experimental evidence for multivariate stabilizing sexual selection

Stabilizing selection is a fundamental concept in evolutionary biology. In the presence of a single intermediate optimum phenotype (fitness peak) on the fitness surface, stabilizing selection should cause the population to evolve toward such a peak. This prediction has seldom been tested, particularly for suites of correlated traits. The lack of tests for an evolutionary match between population means and adaptive peaks may be due, at least in part, to problems associated with empirically detecting multivariate stabilizing selection and with testing whether population means are at the peak of multivariate fitness surfaces. Here we show how canonical analysis of the fitness surface, combined with the estimation of confidence regions for stationary points on quadratic response surfaces, may be used to define multivariate stabilizing selection on a suite of traits and to establish whether natural populations reside on the multivariate peak. We manufactured artificial advertisement calls of the male cricket Teleogryllus commodus and played them back to females in laboratory phonotaxis trials to estimate the linear and nonlinear sexual selection that female phonotactic choice imposes on male call structure. Significant nonlinear selection on the major axes of the fitness surface was convex in nature and displayed an intermediate optimum, indicating multivariate stabilizing selection. The mean phenotypes of four independent samples of males, from the same population as the females used in phonotaxis trials, were within the 95% confidence region for the fitness peak. These experiments indicate that stabilizing sexual selection may play an important role in the evolution of male call properties in natural populations of T. commodus.

Histological structure of the cancellous bone layer in Bothriolepis canadensis (Antiarchi, Placodermi)

The Placodermi are extinct basal gnathostomes which had extensive dermal and perichondral bone, but which lacked the endochondral bone which characterizes the more derived bony fishes. Thin sections of bone from a specimen of the antiarch placoderm Bothriolepis canadensis, from the Escuminac Formation ( Frasnian, Upper Devonian), Quebec, Canada, reveal that part of the cancellous layer in its dermal and endoskeletal bone formed from perichondral bone trabeculae growing around cartilage spheres. The resultant structure mimics that of osteichthyan endochondral bone. The layout and dimensions of this polygonal mosaic patterning of the bone trabeculae and flattened cartilage spheres resemble those of the prismatic layers of calcified cartilage in chondrichthyans. If the lack of endoskeletal bone in chondrichthyans is a derived character, then the structure identified in B. canadensis could represent a 'template' for the formation of prismatic calcified cartilage in the absence of bone.

Reinforcement drives rapid allopatric speciation

Allopatric speciation results from geographic isolation between populations. In the absence of gene flow, reproductive isolation arises gradually and incidentally as a result of mutation, genetic drift and the indirect effects of natural selection driving local adaptation(1-3). In contrast, speciation by reinforcement is driven directly by natural selection against maladaptive hybridization(1,4). This gives individuals that choose the traits of their own lineage greater fitness, potentially leading to rapid speciation between the lineages(1,4). Reinforcing natural selection on a population of one of the lineages in a mosaic contact zone could also result in divergence of the population from the allopatric range of its own lineage outside the zone(4-6). Here we test this with molecular data, experimental crosses, field measurements and mate choice experiments in a mosaic contact zone between two lineages of a rainforest frog. We show that reinforcing natural selection has resulted in significant premating isolation of a population in the contact zone not only from the other lineage but also, incidentally, from the closely related main range of its own lineage. Thus we show the potential for reinforcement to drive rapid allopatric speciation.

A cross-cultural investigation of the use of teaching styles

Teacher beliefs are a major influence on teacher actions. Because context influences beliefs, it was the purpose of this study to explore teachers' beliefs about Mosston's Spectrum of Teaching Styles from an international perspective. Over 1,400 teachers from 7 countries completed a survey related to their self-reported use of and beliefs about various teaching styles. Data suggested a shared core of reproduction teaching style use. The use of and beliefs about the production styles of teaching were more varied. Teachers' use of styles was significantly related to their beliefs about the styles. [PUBLICATION ABSTRACT]

Decreased relatedness between male prickly forest skinks (Gnypetoscincus queenslandiae) in habitat fragments

In species with low levels of dispersal the chance of closely related individuals breeding may be a potential problem; sex-biased dispersal is a mechanism that may decrease the possibility of cosanguineous mating. Fragmentation of the habitat in which a species lives may affect mechanisms such as sex-biased dispersal, which may in turn exacerbate more direct effects of fragmentation such as decreasing population size that may lead to inbreeding depression. Relatedness statistics calculated using microsatellite DNA data showed that rainforest fragmentation has had an effect on the patterns of dispersal in the prickly forest skink (Gnypetoscincus queenslandiae), a rainforest endemic of the Wet Tropics of north eastern Australia. A lower level of relatedness was found in fragments compared to continuous forest sites due to a significantly lower level of pairwise relatedness between males in rainforest fragments. The pattern of genetic relatedness between sexes indicates the presence of male-biased dispersal in this species, with a stronger pattern detected in populations in rainforest fragments. Male prickly forest skinks may have to move further in fragmented habitat in order to find mates or suitable habitat logs.