3,664 research outputs found

    A Phylogenetic Analysis of the African Plant Genus Palisota (family Commelinaceae) based on Chloroplast DNA Sequences

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    The plant genus Palisota (family Commelinaceae, or spiderwort family) consists of approximately 20 species and is distributed throughout the forests of tropical Africa. The genus exhibits several unusual morphological characteristics, and as a result has been difficult to classify based on morphology. Molecular phylogenetic studies have placed it near the base of Commelinaceae, but the exact placement of Palisota within the family is not clear. As the African continent has become more arid in recent geological times, the forests have receded, reducing the habitat for Palisota species and potentially impacting speciation and extinction rates within the genus. The goal of this study is to sequence the chloroplast-encoded gene rbcL in several additional species of Palisota and its relatives in order to: 1) determine the phylogenetic relationship of the genus with respect to other members of Commelinaceae; 2) evaluate phylogenentic relationships among species of Palisota; and 3) infer relative speciation/extinction rates within the genus. Additionally, we are exploring the use of other molecular regions for phylogenetic analysis with the genus

    Subtribal Relationships in Tribe Tradescantieae (Commelinaceae)Based on Molecular and Morphological Data

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    Tribe Tradescantieae (Commelinaceae) consists of seven subtribes and 25 genera. Previous attempts to evaluate phylogenetic relationships within the group using morphology or the chloroplast-encoded rbcL have either been highly homoplasious (morphology) or provided only weak support for subtribal relationships due to insufficient variability (rbcL). In this study, phylogenetic analysis of nucleotide sequence data from the chloroplast-encoded ndhF and rbcL genes, as well as 47 morphological and anatomical characters, were used to evaluate relationships within and among the subtribes of Tradescantieae. The addition of ndhF resulted in a more highly resolved phylogeny and greater bootstrap and decay values than were obtained by rbcL alone or rbcL and morphology. The analyses suggest the following: (1) subtribes Coleotrypinae, Cyanotinae, and Tradescantiinae (with the addition of Elasis) are monophyletic; (2) subtribe Thyrsantheminae is polyphyletic; and (3) subtribe Dichorisandrinae is polyphyletic. Members of Dichorisandrinae are united into two clades (Dichorisandra and Siderasis; Cochliostema, Geogenanthus, and Plowmanianthus) whose relationships are more clearly resolved. The position of Old World subtribes Cyanotinae and Coleotrypinae, nested within New World taxa suggested by rbcL studies, are supported by the addition of ndhF data

    D-Tool

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    The data on which the tool has its origins in PhD research (awarded in 2015) that included the analysis of 64 products; a survey of 34; interviews with 19 product designers working for leading charities; a case study with a social enterprise in Myanmar; and evaluation during a live project in a leading design school. The data generated was thematically analysed during post-doctoral research to create the tool which supports designers and NGOs during the product development process by providing information on Contextualisation (with which some may be unfamiliar); analysis (via a series of Indicators); successful Case Studies; and guidance on how to generate a spiderweb diagram for Concept Selection, Product Re-design and Product Assessment.D-Tool has been created to help support decision making during the design of products. The tool employs a product assessment spider web with eight indicators that draw attention to key considerations for the evaluation of concepts and re-design of existing products. D-Tool is a card based toolkit which highlights factors required for appropriate product design. This will be used in parallel with Human Centred Design and Design Thinking methods

    Exact Scattering in the SU(n) Supersymmetric Principal Chiral Model

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    The complete spectrum of states in the supersymmetric principal chiral model based on SU(n) is conjectured, and an exact factorizable S-matrix is proposed to describe scattering amongst these states. The SU(n)_L*SU(n)_R symmetry of the lagrangian is manifest in the S-matrix construction. The supersymmetries, on the other hand, are incorporated in the guise of spin-1/2 charges acting on a set of RSOS kinks associated with su(n) at level n. To test the proposed S-matrix, calculations of the change in the ground-state energy in the presence of a coupling to a background charge are carried out. The results derived from the lagrangian using perturbation theory and from the S-matrix using the TBA are found to be in complete agreement for a variety of background charges which pick out, in turn, the highest weight states in each of the fundamental representations of SU(n). In particular, these methods rule out the possibility of additional CDD factors in the S-matrix. Comparison of the expressions found for the free-energy also yields an exact result for the mass-gap in these models: m/Lambda_{MS-bar}=(n/pi)sin(pi/n).Comment: 24 pages, plain tex with macro include

    The silence of self-knowledge

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    Gareth Evans famously affirmed an explanatory connection between answering the question whether p and knowing whether one believes that p. This is commonly interpreted in terms of the idea that judging that p constitutes an adequate basis for the belief that one believes that p. This paper formulates and defends an alternative, more modest interpretation, which develops from the suggestion that one can know that one believes that p in judging that p

    Diagnosis of Elder Abuse in U.S. Emergency Departments

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    To estimate the proportion of visits to United States emergency departments (EDs) receiving a diagnosis of elder abuse using two nationally representative datasets

    Molecular phylogeny of Subtribe Artemisiinae (Asteraceae), including Artemisia and its allied and segregate genera

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    BACKGROUND: Subtribe Artemisiinae of Tribe Anthemideae (Asteraceae) is composed of 18 largely Asian genera that include the sagebrushes and mugworts. The subtribe includes the large cosmopolitan, wind-pollinated genus Artemisia, as well as several smaller genera and Seriphidium, that altogether comprise the Artemisia-group. Circumscription and taxonomic boundaries of Artemisia and the placements of these small segregate genera is currently unresolved. RESULTS: We constructed a molecular phylogeny for the subtribe using the internal transcribed spacers (ITS) of nuclear ribosomal DNA analyzed with parsimony, likelihood, and Bayesian criteria. The resulting tree is comprised of three major clades that correspond to the radiate genera (e.g., Arctanthemum and Dendranthema), and two clades of Artemisia species. All three clades have allied and segregate genera embedded within each. CONCLUSIONS: The data support a broad concept of Artemisia s.l. that includes Neopallasia, Crossostephium, Filifolium, Seriphidium, and Sphaeromeria. However, the phylogeny excludes Elachanthemum, Kaschgaria, and Stilnolepis from the Artemisia-group. Additionally, the monophyly of the four subgenera of Artemisia is also not supported, with the exception of subg. Dracunculus. Homogamous, discoid capitula appear to have arisen in parallel four to seven times, with the loss of ray florets. Thus capitular morphology is not a reliable taxonomic character, which traditionally has been one of the defining characters

    Population adaptation for genetic algorithm-based cognitive radios

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    Abstract — Genetic algorithms are best suited for optimization problems involving large search spaces. The problem space encountered when optimizing the transmission parameters of an agile or cognitive radio for a given wireless environment and set of performance objectives can become prohibitively large due to the high number of parameters and their many possible values. Recent research has demonstrated that genetic algorithms are a viable implementation technique for cognitive radio engines. However, the time required for the genetic algorithms to come to a solution substantionally increases as the system complexity grows. In this paper, we present a population adaptation technique for genetic algorithms that takes advantage of the information from previous cognition cycles in order to reduce the time required to reach an optimal decision. Our simulation results demonstrate that the amount of information from the previous cognition cycle can be determined from the environmental variation factor (EVF), which represents the amount of change in the environment parameters since the previous cognition cycle. I

    The Exact Mass-Gap of the Supersymmetric CP^{n-1} Sigam Model

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    A formula for the mass-gap of the supersymmetric \CP^{n-1} sigma model (n>1n > 1) in two dimensions is derived: m/ΛMS‟=sin⁥(πΔ)/(πΔ)m/\Lambda_{\overline{\rm MS}}=\sin(\pi\Delta)/(\pi\Delta) where Δ=1/n\Delta=1/n and mm is the mass of the fundamental particle multiplet. This result is obtained by comparing two expressions for the free-energy density in the presence of a coupling to a conserved charge; one expression is computed from the exact S-matrix of K\"oberle and Kurak via the thermodynamic Bethe ansatz and the other is computed using conventional perturbation theory. These calculations provide a stringent test of the S-matrix, showing that it correctly reproduces the universal part of the beta-function and resolving the problem of CDD ambiguities.Comment: Plain TeX (macro included), CERN-TH.7426/94, SWAT/93-94/4
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