Adaptation and speciation: what can F-st tell us?

A useful way of summarizing genetic variability among different populations is through estimates of the inbreeding coefficient, F-st. Several recent studies have tried to use the distribution of estimates of F-st from individual genetic loci to detect the effects of natural selection. However, the promise of this approach has yet to be fully realized owing to the pervasive dogma that this distribution is highly dependent on demographic history. Here, I review recent theoretical results that indicate that the distribution of estimates of F-st is generally expected to be robust to the vagaries of demographic history. I suggest that analyses based on it provide a useful first step for identifying candidate genes that might be under selection, and explore the ways in which this information can be used in ecological and evolutionary studies.

Recent developments in genetic data analysis: what can they tell us about human demographic history?

Over the last decade, a number of new methods of population genetic analysis based on likelihood have been introduced. This review describes and explains the general statistical techniques that have recently been used, and discusses the underlying population genetic models. Experimental papers that use these methods to infer human demographic and phylogeographic history are reviewed. It appears that the use of likelihood has hitherto had little impact in the field of human population genetics, which is still primarily driven by more traditional approaches. However, with the current uncertainty about the effects of natural selection, population structure and ascertainment of single-nucleotide polymorphism markers, it is suggested that likelihood-based methods may have a greater impact in the future.

Syntheses and spectroscopy of diamine complexes of Zn(II) and Cd(II) ethylxanthates and the molecular structures of [M(S2COEt)(2)TMEDA]: formation of US nanoparticles from [Cd(S2COEt)(2)] and [Cd(S2COEt)(2)TMEDA]

The zinc and cadmium ethylxanthate complexes of N,N,N',N'-tetramethylethylenediamine (TMEDA), [M(S2COEt)(2)TMEDA], were synthesized and characterized with infrared, H-1 and C-13 NMR spectroscopy, mass spectrometry and X-ray crystallography. Whereas the cadmium complex has a six-coordinate {CdS4N2} centre with bidentate xanthate ligands, the zinc complex contains four coordinate {ZnS2N2} zinc with two monodentate xanthate groups. The cadmium species [Cd(S2COEt)(2)(diamine)] (where diamine = N,N-dimethylethylenediamine or N,N'-diisopropylethylenediamine) were also synthesized. The surfactant-assisted formation of nanoparticles from [Cd(S2COEt)(2)] and [Cd(S2COEt)(2)TMEDA] was studied with TEM, XRD and XRF techniques. From [Cd(S2COEt)(2)], spherical nanoparticle aggregates 140-200 nm in diameter were obtained but from [Cd(S2COEt)(2)TMEDA], single nanoparticles were produced with estimated diameters in the range of 4-7 nm and almost no aggregation. (C) 2004 Elsevier Ltd. All rights reserved.

Language support for immigrant children: a study of state schools in the UK and US

In recent decades, immigrants, refugees and asylum seekers have sought a new way of life in large numbers, often leaving their countries of origin behind in search of places that offer a better way of life. The purpose of this study was to investigate how elementary and middle school students in state schools in Reading, England (primarily speakers of Asian languages), and Richmond, Virginia (primarily speakers of Spanish), were supported academically, when most children's first language was not English. The authors were interested in exploring whether or not there were cultural or structural differences in the way each country helped or hindered these students as they progressed through the school systems. Three UK schools in a district of approximately 100,000 and three US schools in a district of approximately 250,000 were the focus of this exploration from 2000 to 2003. Findings indicated that there were cultural and legislative differences and similarities. Teachers and administrators in both countries attempted to provide services with limited and sometimes diminishing resources. Community support varied based on resources, attitudes toward various ethnic groups, and the coping strategies adopted by these groups in their new environments. Marked differences appeared with regard to the manner in which assessments took place and how the results were made available to the public.

Weight of evidence needed to substantiate a health effect for probiotics and prebiotics: regulatory considerations in Canada, EU, and US

Successful and responsible introduction of probiotic and prebiotic products into the worldwide marketplace requires labelling for health benefits that meets consumer needs, adheres to regulatory standards and does not overextend scientific evidence. Regulations differ among countries, but underlying all is an emphasis on scientific credibility of any statements of health benefits. This paper considers the value of different types of evidence offered in substantiation of efficacy and reviews different regulatory approaches to labelling for health claims. Limitations of in vitro, animal and different types of human studies used for efficacy substantiation for probiotics and prebiotics are discussed.

The integration of figurative language and static depictions: an eye movement study of fictive motion

Do we view the world differently if it is described to us in figurative rather than literal terms? An answer to this question would reveal something about both the conceptual representation of figurative language and the scope of top-down influences oil scene perception. Previous work has shown that participants will look longer at a path region of a picture when it is described with a type of figurative language called fictive motion (The road goes through the desert) rather than without (The road is in the desert). The current experiment provided evidence that such fictive motion descriptions affect eye movements by evoking mental representations of motion. If participants heard contextual information that would hinder actual motion, it influenced how they viewed a picture when it was described with fictive motion. Inspection times and eye movements scanning along the path increased during fictive motion descriptions when the terrain was first described as difficult (The desert is hilly) as compared to easy (The desert is flat); there were no such effects for descriptions without fictive motion. It is argued that fictive motion evokes a mental simulation of motion that is immediately integrated with visual processing, and hence figurative language can have a distinct effect on perception. (c) 2005 Elsevier B.V. All rights reserved.

What neuroimaging and perceptions of self-other similarity can tell us about the mechanism underlying mentalizing

Carruthers' "mindreading is prior" model postulates one unitary mindreading mechanism working identically for self and other. While we agree about shared mindreading mechanisms, there is also evidence from neuroimaging and mentalizing about dissimilar others that suggest factors that differentially affect self-versus-other mentalizing. Such dissociations suggest greater complexity than the mindreading is prior model allows.

When does ignorance make us smart? Additional factors guiding heuristic inference

“Fast & frugal” heuristics represent an appealing way of implementing bounded rationality and decision-making under pressure. The recognition heuristic is the simplest and most fundamental of these heuristics. Simulation and experimental studies have shown that this ignorance-driven heuristic inference can prove superior to knowledge based inference (Borges, Goldstein, Ortman & Gigerenzer, 1999; Goldstein & Gigerenzer, 2002) and have shown how the heuristic could develop from ACT-R’s forgetting function (Schooler & Hertwig, 2005). Mathematical analyses also demonstrate that, under certain conditions, a “less-is-more effect” will always occur (Goldstein & Gigerenzer, 2002). The further analyses presented in this paper show, however, that these conditions may constitute a special case and that the less-is-more effect in decision-making is subject to the moderating influence of the number of options to be considered and the framing of the question.

U.K. HiGEM: Simulations of desert dust and biomass burning aerosols with a high-resolution atmospheric GCM

The atmospheric component of the United Kingdom’s new High-resolution Global Environmental Model (HiGEM) has been run with interactive aerosol schemes that include biomass burning and mineral dust. Dust emission, transport, and deposition are parameterized within the model using six particle size divisions, which are treated independently. The biomass is modeled in three nonindependent modes, and emissions are prescribed from an external dataset. The model is shown to produce realistic horizontal and vertical distributions of these aerosols for each season when compared with available satellite- and ground-based observations and with other models. Combined aerosol optical depths off the coast of North Africa exceed 0.5 both in boreal winter, when biomass is the main contributor, and also in summer, when the dust dominates. The model is capable of resolving smaller-scale features, such as dust storms emanating from the Bode´ le´ and Saharan regions of North Africa and the wintertime Bode´ le´ low-level jet. This is illustrated by February and July case studies, in which the diurnal cycles of model variables in relation to dust emission and transport are examined. The top-of-atmosphere annual mean radiative forcing of the dust is calculated and found to be globally quite small but locally very large, exceeding 20 W m22 over the Sahara, where inclusion of dust aerosol is shown to improve the model radiative balance. This work extends previous aerosol studies by combining complexity with increased global resolution and represents a step toward the next generation of models to investigate aerosol–climate interactions. 1. Introduction Accurate modeling of mineral dust is known to be important because of its radiative impact in both numerical weather prediction models (Milton et al. 2008; Haywood et

Kinetic studies of reactions of organosilylenes: what have they taught us?

Rate constants for bimolecular reactions, obtained through time-resolved kinetic studies both in the gas and liquid phases are reviewed. Data for reactions of MeSiH, PhSiH, ClSiH, SiCl2, SiMe2, MeSiPh, SiPh2 and SiMes(2) are covered. Where possible, substituent effects relative to SiH2 have been obtained. These demonstrate widely varying effects between different types of reaction, which aids mechanistic understanding. Reactivities are high for all silylenes, but substituents can reduce them by both electronic and steric effects. The gas and liquid phase data (mainly for SiMe2) are compared and appear to be reasonably consistent. This review, although detailed, is not comprehensive.

Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal “out of Africa” is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals. This system was last active in the early Holocene when many species appear to have occupied the entire Sahara. However, species that require deep water did not reach northern regions because of weak hydrological connections. Human dispersals were influenced by this distribution; Nilo-Saharan speakers hunting aquatic fauna with barbed bone points occupied the southern Sahara, while people hunting Savannah fauna with the bow and arrow spread southward. The dating of lacustrine sediments show that the “green Sahara” also existed during the last interglacial (∼125 ka) and provided green corridors that could have formed dispersal routes at a likely time for the migration of modern humans out of Africa.