243 research outputs found

    A molecular phylogeny of Southeast Asian Cyrtandra (Gesneriaceae) supports an emerging paradigm for Malesian plant biogeography

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    The islands of Southeast Asia comprise one of the most geologically and biogeographically complex areas in the world and are a centre of exceptional floristic diversity, harbouring 45,000 species of flowering plants. Cyrtandra, with over 800 species of herbs and shrubs, is the largest genus in the family Gesneriaceae and is one of the most emblematic and species-rich genera of the Malesian rainforest understorey. The high number of species and tendency to narrow endemism make Cyrtandra an ideal genus for examining biogeographic patterns. We sampled 128 Cyrtandra taxa from key localities across Southeast Asia to evaluate the geo-temporal patterns and evolutionary dynamics of this clade. One nuclear and four chloroplast regions were used for phylogenetic reconstruction, molecular dating, and ancestral range estimation. Results from the dating analysis suggest that the great diversity of Cyrtandra seen in the Malesian region results from a recent radiation, with most speciation taking place in the last five million years. Borneo was recovered as the most likely ancestral range of the genus, with the current distribution of species resulting from a west to east migration across Malesia that corresponds with island emergence and mountain building. Lastly, our investigation into the biogeographic history of the genus indicates high levels of floristic exchange between the islands on the Sunda shelf and the important role of the Philippines as a stepping stone to Wallacea and New Guinea. These patterns underlie much of the plant diversity in the region and form an emerging paradigm in Southeast Asian plant biogeography

    Characterization of the Positivity of the Density Matrix in Terms of the Coherence Vector Representation

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    A parameterization of the density operator, a coherence vector representation, which uses a basis of orthogonal, traceless, Hermitian matrices is discussed. Using this parameterization we find the region of permissible vectors which represent a density operator. The inequalities which specify the region are shown to involve the Casimir invariants of the group. In particular cases, this allows the determination of degeneracies in the spectrum of the operator. The identification of the Casimir invariants also provides a method of constructing quantities which are invariant under {\it local} unitary operations. Several examples are given which illustrate the constraints provided by the positivity requirements and the utility of the coherence vector parameterization.Comment: significantly rewritten and submitted for publicatio

    Southern Foresters\u27 Perceptions of Climate Change: Implications for Educational Program Development

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    An understanding of foresters\u27 perceptions of climate change is important for developing effective educational programs on adaptive forest management. We surveyed 1,398 foresters in the southern United States regarding their perceptions of climate change, observations and concerns about climatic and forest conditions, and knowledge of and interest in resilient forest management techniques and climate science. A majority (61%) agreed that climate change is occurring, and 14% agreed that it is caused by humans. Most respondents were interested in learning more about forest resilience and related concepts. Development of programming focused on managing for forest resilience in a changing climate is a prudent educational approach that builds on familiar risk-management strategies

    Beneficial Inner-City Quay Walls?

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    Inner-city quay walls in public urban areas: expense or added value? These civil structures approach, reach or exceed the end of their life span. This threatens the quality of the public urban area. Many municipalities are still willing to invest in the management of inner-city quay walls, despite the costs. Apparently, the quay walls generate more benefits than that are initially expected based on their original functions. Until now, municipalities have failed to determine the added value of inner-city quay walls. Theoretical and practical research suggests that adequate asset management is indispensable. Nevertheless, no research focuses on valuable management of inner-city quays, in terms of performance, costs, benefits and risks. How to decide on a management strategy that adds the most value to the public area? A new framework should identify and incorporate the value of inner-city quay walls in the management process

    On the Classification of Diagonal Coset Modular Invariants

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    We relate in a novel way the modular matrices of GKO diagonal cosets without fixed points to those of WZNW tensor products. Using this we classify all modular invariant partition functions of su(3)k⊕su(3)1/su(3)k+1su(3)_k\oplus su(3)_1/su(3)_{k+1} for all positive integer level kk, and su(2)k⊕su(2)ℓ/su(2)k+ℓsu(2)_k\oplus su(2)_\ell/su(2)_{k+\ell} for all kk and infinitely many ℓ\ell (in fact, for each kk a positive density of ℓ\ell). Of all these classifications, only that for su(2)k⊕su(2)1/su(2)k+1su(2)_k\oplus su(2)_1/su(2)_{k+1} had been known. Our lists include many new invariants.Comment: 24 pp (plain tex

    A framework for the detection of de novo mutations in family-based sequencing data

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    Germline mutation detection from human DNA sequence data is challenging due to the rarity of such events relative to the intrinsic error rates of sequencing technologies and the uneven coverage across the genome. We developed PhaseByTransmission (PBT) to identify de novo single nucleotide variants and short insertions and deletions (indels) from sequence data collected in parent-offspring trios. We compute the joint probability of the data given the genotype likelihoods in the individual family members, the known familial relationships and a prior probability for the mutation rate. Candidate de novo mutations (DNMs) are reported along with their posterior probability, providing a systematic way to prioritize them for validation. Our tool is integrated in the Genome Analysis Toolkit and can be used together with the ReadBackedPhasing module to infer the parental origin of DNMs based on phase-informative reads. Using simulated data, we show that PBT outperforms existing tools, especially in low coverage data and on the X chromosome. We further show that PBT displays high validation rates on empirical parent-offspring sequencing data for whole-exome data from 104 trios and X-chromosome data from 249 parent-offspring families. Finally, we demonstrate an association between father's age at conception and the number of DNMs in female offspring's X chromosome, consistent with previous literature reports

    Level Set Method for the Evolution of Defect and Brane Networks

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    A theory for studying the dynamic scaling properties of branes and relativistic topological defect networks is presented. The theory, based on a relativistic version of the level set method, well-known in other contexts, possesses self-similar ``scaling'' solutions, for which one can calculate many quantities of interest. Here, the length and area densities of cosmic strings and domain walls are calculated in Minkowski space, and radiation, matter, and curvature-dominated FRW cosmologies with 2 and 3 space dimensions. The scaling exponents agree the naive ones based on dimensional analysis, except for cosmic strings in 3-dimensional Minkowski space, which are predicted to have a logarithmic correction to the naive scaling form. The scaling amplitudes of the length and area densities are a factor of approximately 2 lower than results from numerical simulations of classical field theories. An expression for the length density of strings in the condensed matter literature is corrected.Comment: 46pp LaTeX, revtex4(preprint), 1 eps figure, revised for publication. Note title chang

    Growth and retreat of the last British–Irish Ice Sheet, 31 000 to 15 000 years ago: the BRITICE-CHRONO reconstruction

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    The BRITICE-CHRONO consortium of researchers undertook a dating programme to constrain the timing of advance, maximum extent and retreat of the British–Irish Ice Sheet between 31 000 and 15 000 years before present. The dating campaign across Ireland and Britain and their continental shelves, and across the North Sea included 1500 days of field investigation yielding 18 000 km of marine geophysical data, 377 cores of sea floor sediments, and geomorphological and stratigraphical information at 121 sites on land; generating 690 new geochronometric ages. These findings are reported in 28 publications including synthesis into eight transect reconstructions. Here we build ice sheet-wide reconstructions consistent with these findings and using retreat patterns and dates for the inter-transect areas. Two reconstructions are presented, a wholly empirical version and a version that combines modelling with the new empirical evidence. Palaeoglaciological maps of ice extent, thickness, velocity, and flow geometry at thousand-year timesteps are presented. The maximum ice volume of 1.8 m sea level equivalent occurred at 23 ka. A larger extent than previously defined is found and widespread advance of ice to the continental shelf break is confirmed during the last glacial. Asynchrony occurred in the timing of maximum extent and onset of retreat, ranging from 30 to 22 ka. The tipping point of deglaciation at 22 ka was triggered by ice stream retreat and saddle collapses. Analysis of retreat rates leads us to accept our hypothesis that the marine-influenced sectors collapsed rapidly. First order controls on ice-sheet demise were glacio-isostatic loading triggering retreat of marine sectors, aided by glaciological instabilities and then climate warming finished off the smaller, terrestrial ice sheet. Overprinted on this signal were second order controls arising from variations in trough topographies and with sector-scale ice geometric readjustments arising from dispositions in the geography of the landscape. These second order controls produced a stepped deglaciation. The retreat of the British–Irish Ice Sheet is now the world’s most well-constrained and a valuable data-rich environment for improving ice-sheet modelling.publishedVersio

    Practical steps needed to achieve impact of the WHO 2019 movement behaviour guidelines for children under the age of 5 : the SUNRISE Study Europe Group evaluation

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    The World Health Organisation (WHO) guidelines for the ‘24-h movement behaviours’1 (physical activity (PA), sedentary behaviour (SB) including screen time, and sleep) in the under-5s were published in April 2019 (Supplementary Figure S1).2 The guidelines were developed as a response to the childhood obesity pandemic,2 to help ensure that under-5s have healthy levels of PA, screen time, and sleep. Evidence review and synthesis showed that these behaviours influenced a wide range of other outcomes, with substantial short-term and long-term consequences (e.g., cognitive, social and emotional development; language development; cardiometabolic health; bone and skeletal health; motor development; physical fitness; growth; and wellbeing).2 Five years later, it is now appropriate to test whether key actions in response to these guidelines were taken across Europe, and to consider ways of increasing the impact of the WHO Guidelines across Europe in the next 5 years. Therefore, the SUNRISE Study Europe Group considered three tests to examine if European public health policy and clinical practice were sufficiently responsive to the WHO Guidelines: (1) Do European nations have national guidelines for the movement behaviours in the under-5s or have they adopted/adapted the WHO Guidelines? (2) Do they have adequate surveillance of the movement behaviours in these age groups? (3) Do they have specific movement behaviour policies for children under-5

    On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

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    Abstract The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ′ volume fraction and a finer tertiary γ′ distribution. In addition, an increase in the anti-phase-boundary energy of the γ′ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ′ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.This work was supported by the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1, EP/H500375/1 and EP/ M005607/1
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