13,901 research outputs found

    The Doctrines of Sin and Atonement in Reinhold Niebuhr\u27s Theology: An Analysis and a Proposed Corrective

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    Lecture presented at Lutheran Theological Seminary, Saskatoon, Fall 1995

    Metaphase Configurations in Drosophila: A Comparison of Endemic Hawaiian Species and Non-Endemic Species

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    The metaphase configurations of 400 strains from 63 species of Hawaiian Drosophila were determined from squash preparations of larval brain tissue or spermatogenic cells from adult testes. These karyotypes include configurations from seven species not previously described. Metaphases of 148 Hawaiian species have been recorded, including species of the picture-wing group, the modified mouthpart group, and the bristle-foot group. A comparison between Hawaiian species and non-endemic species was made on the basis of chromosome numbers and configurations. Among the Hawaiian species, 85.8% have retained the primitive haploid configuration of five rods and one dot compared with only 34.8% of species from the rest of the world. In only 4.7% of Hawaiian species is the chromosome number reduced from the basic haploid number of six, whereas it is reduced in 47.6% of the species from other areas. Most of the changes in chromosome size and shape among the Hawaiian species seem to be the result of added heterochromatin or chromosome fusions; no evidence of pericentric inversions has been found in modified karyotypes

    On Questions of Decay and Existence for the Viscous Camassa-Holm Equations

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    We consider the viscous nn-dimensional Camassa-Holm equations, with n=2,3,4n=2,3,4 in the whole space. We establish existence and regularity of the solutions and study the large time behavior of the solutions in several Sobolev spaces. We first show that if the data is only in L2L^2 then the solution decays without a rate and that this is the best that can be expected for data in L2L^2. For solutions with data in Hm∩L1H^m\cap L^1 we obtain decay at an algebraic rate which is optimal in the sense that it coincides with the rate of the underlying linear part.Comment: 36 pages, to appear. This version contains corrected typo

    Field operations with cesium clocks in HF navigation systems

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    Networks of HF phase comparison marine navigation stations employing cesium clocks are discussed. The largest permanent network is in the Gulf of Mexico where some fourteen base stations are continuously active and others are activated as needed. These HF phase comparison systems, which operate on a single transmission path, require a clock on the mobile unit as well. Inventory consists of upwards of 70 clocks from two different manufacturers. The maintenance of this network as an operating system requires a coordinated effort involving clock preparation, clock environment control, station performance monitoring and field service

    Detecting adaptive evolution in phylogenetic comparative analysis using the Ornstein-Uhlenbeck model

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    Phylogenetic comparative analysis is an approach to inferring evolutionary process from a combination of phylogenetic and phenotypic data. The last few years have seen increasingly sophisticated models employed in the evaluation of more and more detailed evolutionary hypotheses, including adaptive hypotheses with multiple selective optima and hypotheses with rate variation within and across lineages. The statistical performance of these sophisticated models has received relatively little systematic attention, however. We conducted an extensive simulation study to quantify the statistical properties of a class of models toward the simpler end of the spectrum that model phenotypic evolution using Ornstein-Uhlenbeck processes. We focused on identifying where, how, and why these methods break down so that users can apply them with greater understanding of their strengths and weaknesses. Our analysis identifies three key determinants of performance: a discriminability ratio, a signal-to-noise ratio, and the number of taxa sampled. Interestingly, we find that model-selection power can be high even in regions that were previously thought to be difficult, such as when tree size is small. On the other hand, we find that model parameters are in many circumstances difficult to estimate accurately, indicating a relative paucity of information in the data relative to these parameters. Nevertheless, we note that accurate model selection is often possible when parameters are only weakly identified. Our results have implications for more sophisticated methods inasmuch as the latter are generalizations of the case we study.Comment: 38 pages, in press at Systematic Biolog
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