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One Position (one + position)
Selected AbstractsThe evolution of black plumage from blue in Australian fairy-wrens (Maluridae): genetic and structural evidenceJOURNAL OF AVIAN BIOLOGY, Issue 5 2010Amy C. Driskell Genetic variation in the melanocortin-1 receptor (MC1R) locus is responsible for color variation, particularly melanism, in many groups of vertebrates. Fairy-wrens, Maluridae, are a family of Australian and New Guinean passerines with several instances of dramatic shifts in plumage coloration, both intra- and inter-specifically. A number of these color changes are from bright blue to black plumage. In this study, we examined sequence variation at the MC1R locus in most genera and species of fairy-wrens. Our primary focus was subspecies of the white-winged fairy-wren Malurus leucopterus in which two subspecies, each endemic to islands off the western Australian coast, are black while the mainland subspecies is blue. We found fourteen variable amino acid residues within M. leucopterus, but at only one position were alleles perfectly correlated with plumage color. Comparison with other fairy-wren species showed that the blue mainland subspecies, not the black island subspecies, had a unique genotype. Examination of MC1R protein sequence variation across our sample of fairy-wrens revealed no correlation between plumage color and sequence in this group. We thus conclude that amino acid changes in the MC1R locus are not directly responsible for the black plumage of the island subspecies of M. leucopterus. Our examination of the nanostructure of feathers from both black and blue subspecies of M. leucopterus and other black and blue fairy-wren species clarifies the evolution of black plumage in this family. Our data indicate that the black white-winged fairy-wrens evolved from blue ancestors because vestiges of the nanostructure required for the production of blue coloration exist within their black feathers. Based on our phylogeographic analysis of M. leucopterus, in which the two black subspecies do not appear to be each other's closest relatives, we infer that there have been two independent evolutionary transitions from blue to black plumage. A third potential transition from blue to black appears to have occurred in a sister clade. [source] GERT ON UNRESOLVABLE MORAL DEBATESMETAPHILOSOPHY, Issue 4 2007TIMM TRIPLETT Abstract: Bernard Gert argues that, while the moral system contains a procedure for resolving most moral disagreements, it does not allow for such resolution in all cases. For example, it does not allow for the resolution of disputes about whether animals and human fetuses should be included within the scope of those to whom the moral rules apply. I agree with Gert that not all moral debates can be resolved, but I believe that Gert does not use all the argumentative resources available to philosophers to resolve them. I argue that considerations outside the moral system proper can be used to provide argumentative support favoring some positions over their rivals in moral controversies that Gert regards as intractable. I illustrate this with reference to the abortion debate. I also argue that reaching such conclusions about the superiority of one position over rivals need not result in moral arrogance. [source] Diagnostic cross-linking of paired cysteine pairs demonstrates homologous structures for two chemoreceptor domains with low sequence identityPROTEIN SCIENCE, Issue 1 2006Wing-Cheung Lai Abstract Hundreds of bacterial chemoreceptors from many species have periplasmic, ligand-recognition domains of approximately the same size, but little or no sequence identity. The only structure determined is for the periplasmic domain of chemoreceptor Tar from Salmonella and Escherichia coli. Do sequence-divergent but similarly sized chemoreceptor periplasmic domains have related structures? We addressed this issue for the periplasmic domain of chemoreceptor TrgE from E. coli, which has a low level of sequence similarity to Tar, by combining homology modeling and diagnostic cross-linking between pairs of introduced cysteines. A homology model of the TrgE domain was created using the homodimeric, four-helix bundle structure of the TarS domain from Salmonella. In this model, we chose four pairs of positions at which introduced cysteines would be sufficiently close to form disulfides across each of four different helical interfaces. For each pair we chose a second pair, in which one cysteine of the original pair was shifted by one position around the helix and thus would be less favorably placed for disulfide formation. We created genes coding for proteins containing four such pairs of cysteine pairs and investigated disulfide formation in vivo as well as functional consequences of the substitutions and disulfides between neighboring helices. Results of the experimental tests provided strong support for the accuracy of the model, indicating that the TrgE periplasmic domain is very similar to the TarS domain. Diagnostic cross-linking of paired pairs of introduced cysteines could be applied generally as a stringent test of homology models. [source] Intuitions and introspections about imagery: the role of imagery experience in shaping an investigator's theoretical viewsAPPLIED COGNITIVE PSYCHOLOGY, Issue 2 2003Daniel Reisberg Early in a scientific debate, before much evidence has accumulated, why are some scientists inclined toward one position and other scientists toward the opposite position? We explore this issue with a focus on scientists' views of the ,imagery debate' that unfolded in Cognitive Science during the late 1970s and early 1980s. We examine the possibility that, during the early years of this debate, researchers' views were shaped by their own conscious experiences with imagery. Consistent with this suggestion, a survey of 150 psychologists, philosophers, and neuroscientists showed that those who experienced their own visual imagery as vivid and picture-like recall being more sympathetic in 1980 to the view that, in general, images are picture-like. Similarly, those who have vivid images and who regularly use their images in cognition were more inclined to believe that issues of image vividness deserve more research. Copyright © 2002 John Wiley & Sons, Ltd. [source] Drought, Domestic Budgeting and Wealth Distribution in Sahelian HouseholdsDEVELOPMENT AND CHANGE, Issue 5 2000Matthew Turner Over the past twenty-five years, Sahelian households have experienced recurrent harvest failure and greater reliance on remittances from migratory wage labour. Household subsistence has become less dependent on household grain stores and more on the liquidation of individual wealth stores. This study investigates how these broader changes have affected struggles between household members over obligations to support the household in the Zarmaganda region of western Niger. As the land-derived leverage of male patriarchs has declined and household dependence on individual wealth stores has increased, domestic budgeting has become more contested. Household heads make case-by-case moral claims on other household members during times of grain shortage. Women and subordinate males invoke Islamic law, which accords primary provisioning responsibility to the household head, to protect their individual wealth in times of grain deficit. This article investigates the nature of these budgetary struggles, showing how individuals' decisions to contribute individual wealth to support the household are best understood as highly situated, affected not only by the specific material conditions of the household but also the interplay of the moral, structural, and individualistic imperatives that derive from one's position within the household. Using reconstructed livestock wealth histories for the members of fifty-four households in western Niger, this study investigates the material consequences of these struggles. Male heads of corporate households, the historic managers of the household's land and agricultural labour, have lost wealth relative to their wives and married male subordinates since the drought of 1984. [source] Using the Theory of Reasoned Action to Model Retention in Rural Primary Care PhysiciansTHE JOURNAL OF RURAL HEALTH, Issue 3 2003Thomas Hugh Feeley PhD Purpose: The current review uses Fishbein and Ajzen's Theory of Reasoned Action (TRA) to organize the literature on the predictors and correlates of retention of rural practicing physicians. TRA suggests turnover behavior is directly predicted by one's turnover intentions, which are, in turn, predicted by one's attitudes about rural practice and perceptions of salient others' (eg, spouse's) attitudes about rural practice and rural living. Methods:Narrative literature review of scholarship in predicting and understanding predictors and correlates of rural physician retention. Findings: The TRA model provides a useful conceptual model to organize the literature on rural physician retention. Physicians' subjective norms regarding rural practice are an important source of influence in the decision to remain or leave one's position, and this relation should be more fully examined in future research [source] | ||||||||||