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Crucial Distinction (crucial + distinction)
Selected AbstractsPERSPECTIVE: GENE DIVERGENCE, POPULATION DIVERGENCE, AND THE VARIANCE IN COALESCENCE TIME IN PHYLOGEOGRAPHIC STUDIESEVOLUTION, Issue 6 2000ScottV. Abstract Molecular methods as applied to the biogeography of single species (phylogeography) or multiple codistributed species (comparative phylogeography) have been productively and extensively used to elucidate common historical features in the diversification of the Earth's biota. However, only recently have methods for estimating population divergence times or their confidence limits while taking into account the critical effects of genetic polymorphism in ancestral species become available, and earlier methods for doing so are underutilized. We review models that address the crucial distinction between the gene divergence, the parameter that is typically recovered in molecular phylogeographic studies, and the population divergence, which is in most cases the parameter of interest and will almost always postdate the gene divergence. Assuming that population sizes of ancestral species are distributed similarly to those of extant species, we show that phylogeographic studies in vertebrates suggest that divergence of alleles in ancestral species can comprise from less than 10% to over 50% of the total divergence between sister species, suggesting that the problem of ancestral polymorphism in dating population divergence can be substantial. The variance in the number of substitutions (among loci for a given species or among species for a given gene) resulting from the stochastic nature of DNA change is generally smaller than the variance due to substitutions along allelic lines whose coalescence times vary due to genetic drift in the ancestral population. Whereas the former variance can be reduced by further DNA sequencing at a single locus, the latter cannot. Contrary to phylogeographic intuition, dating population divergence times when allelic lines have achieved reciprocal monophyly is in some ways more challenging than when allelic lines have not achieved monophyly, because in the former case critical data on ancestral population size provided by residual ancestral polymorphism is lost. In the former case differences in coalescence time between species pairs can in principle be explained entirely by differences in ancestral population size without resorting to explanations involving differences in divergence time. Furthermore, the confidence limits on population divergence times are severely underestimated when those for number of substitutions per site in the DNA sequences examined are used as a proxy. This uncertainty highlights the importance of multilocus data in estimating population divergence times; multilocus data can in principle distinguish differences in coalescence time (T) resulting from differences in population divergence time and differences in T due to differences in ancestral population sizes and will reduce the confidence limits on the estimates. We analyze the contribution of ancestral population size (,) to T and the effect of uncertainty in , on estimates of population divergence (,) for single loci under reciprocal monophyly using a simple Bayesian extension of Takahata and Satta's and Yang's recent coalescent methods. The confidence limits on , decrease when the range over which ancestral population size , is assumed to be distributed decreases and when increases; they generally exclude zero when /(4Ne) > 1. We also apply a maximum-likelihood method to several single and multilocus data sets. With multilocus data, the criterion for excluding = 0 is roughly that l/(4Ne)> 1, where l is the number of loci. Our analyses corroborate recent suggestions that increasing the number of loci is critical to decreasing the uncertainty in estimates of population divergence time. [source] Effective Efficiency as a Tool for Sustainable Water Resources Management,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2008Naim Haie Abstract:, The sufficiency and usefulness of Effective Efficiency (EE) as a water resources index is shown through conceptual formulation of a generalized EE and practical applications. Two EE models are proposed: one is based on water quantity and the other on quantity and quality, with the possibility of considering water reuse (recycling) in both. These models were developed for two scales: the first is called Project EE and the second Basin EE. The latter gives the influence of the project on the water resources systems of the basin while the former does not make such connection to the whole basin. Such considerations give proper signals as to the adequacy of any intervention to increase efficiency. A crucial distinction is made between depletion and diversion water savings. Classical Efficiency (CE) models are analyzed and compared with the various EE models. CE results in values that are less than EE because of not considering water reuse and water quality in its calculation. Some authors, pointing to these problems , particularly the first problem , have advocated the use of hydrological "fractions" instead of efficiency concepts. This paper defends the use of a proper efficiency model such as EE and suggests putting an end to the use of the CE indicators. To test the models, they are applied to five cases of irrigation and city water use in the United States and Egypt. The analysis of the results demonstrates all the points mentioned above and the potential of the EE models to adequately describe the water resources efficiency and sustainability at a location. [source] Exodus as Travelling Theory: Excavating the Promised Land in the African American ImaginationLITERATURE COMPASS (ELECTRONIC), Issue 3 2007Anna Hartnell This essay won the 2006 Literature Compass Graduate Essay Prize, American Section. Exodus, this article suggests, is one of the defining texts through which Americans have imaginatively re-mapped the nation's relationship to the spectre of ,Egyptian' oppression. This article proposes to consider the evolution of the Exodus text from its pivotal place in an often imperialist presidential rhetoric to its central position in African American elaborations of resistance. I suggest that the story of Exodus issuing from the lips of W. E. B. Du Bois, Martin Luther King or Toni Morrison crucially unsettles the ,innocent' position assumed by America's political establishment in relation to the enigmatic question of ,freedom'. This article reviews the interruptive possibilities of African American re-tellings of the Exodus narrative in the context of Edward Said's notion of ,travelling theory'. In his examination of theories devolved from their point of origin, Said poses a crucial distinction between theories that lose their critical power via domestication to the status quo and those which ,flame out' from this path by reaffirming and even furthering their radical potential. I argue here that it is these destablizing currents that largely animate the African American counter-cultural tradition that excavates the promised land in order to tell of a fundamentally ,unhomely' exodus. Where mainstream invocations of Exodus present America's rendition as an epochal overcoming of Hegel's seemingly inexorable master/slave dialectic, the appropriation of this story by America's internal ,others' is a standing reminder that America is not , contra Hegel's memorable suggestion , the destination of ,History's' end. [source] Relationship between formation of the femoral bicondylar angle and trochlear shape: Independence of diaphyseal and epiphyseal growthAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2006C. Tardieu Abstract During hominin evolution, an increase in the femoral bicondylar angle was the initial change that led to selection for protuberance of the lateral trochlear lip and the elliptical profile of the lateral condyle. No correlation is found during ontogeny between the degree of femoral obliquity and of the prominence of the lateral trochlear lip. Might there be a relationship with the elliptical profile of the lateral condyle? On intact femoral diaphyses of juvenile humans and great apes, we compared the anteroposterior length of the lateral and medial sides of the distal metaphysis. The two diaphyseal pillars remain equal during postnatal growth in great apes, while the growth of the lateral pillar far exceeds that of the medial pillar in humans. Increase in bicondylar angle is correlated with disproportionate anteroposterior lengthening of the lateral pillar. The increased anteroposterior length of the lateral side of the metaphysis would contribute to increasing the radius of the curvature of the lateral condyle, but not to the projection of the lateral trochlear lip. The similar neonatal and adult femoro-patellar joint shape in humans prompted an assessment of the similarity during growth of the entire neonatal and adult epiphyses. We showed that the entire epiphysis undergoes drastic changes in proportions during postnatal growth. Finally, we emphasize the need to distinguish the cartilaginous phenotype and the ossified phenotype of the distal femoral epiphysis (and of any epiphysis) during postnatal growth. This crucial distinction applies to most postcranial bones, for they almost all develop following the process of endochondral ossification. Am J Phys Anthropol, 2006. © 2006 Wiley-Liss, Inc. [source] Alternative Forms of Mixing Banking with Commerce: Evidence from American HistoryFINANCIAL MARKETS, INSTITUTIONS & INSTRUMENTS, Issue 2 2003Joseph G. Haubrich Much of the discussion about banking and commerce in America has failed to make several crucial distinctions and has not accounted for many arrangements that have promoted the mixing of these activities. We investigate the history of banking and commerce in the United States, looking both at bank control of commercial firms and commercial firms' control of banks. We trace how these controls have changed with shifting definitions of "bank" and changing methods of "control." Despite the regulations prohibiting some arrangements that promote financial control, we find evidence of extensive linkages between banking and commerce in the United States. These linkages usually build on devices that are very close substitutes to the arrangements prohibited by law. Altogether, our findings question the often made claim that traditionally banking in the United States has been separated from commerce. Furthermore, given that research on Japan and Germany has shown that the mixing of banking and commerce matters for a variety of issues, our evidence also raises some questions on similar research in the United States which makes the simplifying assumption that these industries are separated. [source] | ||||||||||