765 research outputs found

    The importance of unique populations for conservation: the case of the Great Orme’s Head grayling butterfly Hipparchia semele (Linnaeus, 1758) (Lepidoptera: Satyrinae)

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    Small populations with unusual characteristics subject to extreme conditions provide opportunities for exploring adaptability in the face of environmental changes. Two sets of data have been examined to determine how unusual is the population of Hipparchia semele on the Great Orme’s Head, North Wales, compared with other sites in the UK. The population on the Great Orme is shown to have unique features, including significantly reduced wing expanse and wing ocellation and extreme flight period characteristics. Analyses of flight period data from the UK Butterfly Monitoring Scheme (UKBMS) using over a 100 sites reveals that, although the Great Orme population is one of a number of sites from the Channel Islands to northern Scotland with an early mean flight period, it has by far the earliest flight period and longest flight period of all populations—the latter raising the mean flight period date. Furthermore the unique characteristics of H. semele on the Orme may well be underestimated, inasmuch as sampling of individuals for the phenotype study is incomplete, including only the area along the North Wales coast into Cheshire, while the UKBMS transect is restricted to the south-west portion of the headland. Unique populations are often accorded focused conservation effort; especially potential flagship species in decline as in the case of British H. semele. As the Great Orme population presents a rare opportunity for studying adaptations in an extreme local environment, particularly considering current projections for climate changes, we advocate further research and attention being given to this unusual population

    Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

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    Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years

    Distorted Copulas: Constructions and Tail Dependence

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    Given a copula C, we examine under which conditions on an order isomorphism ψ of [0, 1] the distortion C ψ: [0, 1]2 → [0, 1], C ψ(x, y) = ψ{C[ψ−1(x), ψ−1(y)]} is again a copula. In particular, when the copula C is totally positive of order 2, we give a sufficient condition on ψ that ensures that any distortion of C by means of ψ is again a copula. The presented results allow us to introduce in a more flexible way families of copulas exhibiting different behavior in the tails

    Dosing pole recommendations for lymphatic filariasis elimination: A height-weight quantile regression modeling approach

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    BACKGROUND: The World Health Organization (WHO) currently recommends height or age-based dosing as alternatives to weight-based dosing for mass drug administration lymphatic filariasis (LF) elimination programs. The goals of our study were to compare these alternative dosing strategies to weight-based dosing and to develop and evaluate new height-based dosing pole scenarios. METHODOLOGY/PRINCIPAL FINDINGS: Age, height and weight data were collected from \u3e26,000 individuals in five countries during a cluster randomized LF clinical trial. Weight-based dosing for diethylcarbamazine (DEC; 6 mg/kg) and ivermectin (IVM; 200 ug/kg) with tablet numbers derived from a table of weight intervals was treated as the gold standard for this study. Following WHO recommended age-based dosing of DEC and height-based dosing of IVM would have resulted in 32% and 27% of individuals receiving treatment doses below those recommended by weight-based dosing for DEC and IVM, respectively. Underdosing would have been especially common in adult males, who tend to have the highest LF prevalence in many endemic areas. We used a 3-step modeling approach to develop and evaluate new dosing pole cutoffs. First, we analyzed the clinical trial data using quantile regression to predict weight from height. We then used weight predictions to develop new dosing pole cutoff values. Finally, we compared different dosing pole cutoffs and age and height-based WHO dosing recommendations to weight-based dosing. We considered hundreds of scenarios including country- and sex-specific dosing poles. A simple dosing pole with a 6-tablet maximum for both DEC and IVM reduced the underdosing rate by 30% and 21%, respectively, and was nearly as effective as more complex pole combinations for reducing underdosing. CONCLUSIONS/SIGNIFICANCE: Using a novel modeling approach, we developed a simple dosing pole that would markedly reduce underdosing for DEC and IVM in MDA programs compared to current WHO recommended height or age-based dosing

    Outside-in disk evolution in the LMC

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    From the analysis of the color-magnitude diagrams and color functions of four wide LMC fields located from ~2 to 6 kpc from the kinematic center of the LMC we present evidence that, while the oldest population is coeval in all fields, the age of the youngest component of the dominant stellar population gradually increases with galactocentric distance, from currently active star formation in a field at 2.3 deg, to 100 Myr, 0.8 Gyr, and 1.5 Gyr in fields at 4.0 deg, 5.5 deg, and 7.1 deg, respectively. This outside-in quenching of the star formation in the LMC disk is correlated with the decreasing HI column density (which is < 2x 10^{20} cm^{-2} in the two outermost fields with little or no current star formation. Other work in the literature hints at similar behavior in the stellar populations of irregular galaxies, and in M33. This is observational evidence against the inside-out disk formation scenario in low-mass spirals and irregular galaxies. Alternatively, it could be that the age distribution with radius results from interplay between the evolution with time of the star-forming area of the LMC and the subsequent outward migration of the stars.Comment: 6 pages, 2 figures, ApJ Letters, in pres

    Analysis of Pulmonary Inflammation and Function in the Mouse and Baboon after Exposure to Mycoplasma pneumoniae CARDS Toxin

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    Mycoplasma pneumoniae produces an ADP-ribosylating and vacuolating toxin known as the CARDS (Community Acquired Respiratory Distress Syndrome) toxin that has been shown to be cytotoxic to mammalian cells in tissue and organ culture. In this study we tested the ability of recombinant CARDS (rCARDS) toxin to elicit changes within the pulmonary compartment in both mice and baboons. Animals responded to a respiratory exposure to rCARDS toxin in a dose and activity-dependent manner by increasing the expression of the pro-inflammatory cytokines IL-1α, 1β, 6, 12, 17, TNF-α and IFN-γ. There was also a dose-dependent increase in several growth factors and chemokines following toxin exposure including KC, IL-8, RANTES, and G-CSF. Increased expression of IFN-γ was observed only in the baboon; otherwise, mice and baboons responded to CARDS toxin in a very similar manner. Introduction of rCARDS toxin to the airways of mice or baboons resulted in a cellular inflammatory response characterized by a dose-dependent early vacuolization and cytotoxicity of the bronchiolar epithelium followed by a robust peribronchial and perivascular lymphocytic infiltration. In mice, rCARDS toxin caused airway hyper-reactivity two days after toxin exposure as well as prolonged airway obstruction. The changes in airway function, cytokine expression, and cellular inflammation correlate temporally and are consistent with what has been reported for M. pneumoniae infection. Altogether, these data suggest that the CARDS toxin interacts extensively with the pulmonary compartment and that the CARDS toxin is sufficient to cause prolonged inflammatory responses and airway dysfunction

    APP metabolism regulates tau proteostasis in human cerebral cortex neurons.

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    Accumulation of Aβ peptide fragments of the APP protein and neurofibrillary tangles of the microtubule-associated protein tau are the cellular hallmarks of Alzheimer's disease (AD). To investigate the relationship between APP metabolism and tau protein levels and phosphorylation, we studied human-stem-cell-derived forebrain neurons with genetic forms of AD, all of which increase the release of pathogenic Aβ peptides. We identified marked increases in intracellular tau in genetic forms of AD that either mutated APP or increased its dosage, suggesting that APP metabolism is coupled to changes in tau proteostasis. Manipulating APP metabolism by β-secretase and γ-secretase inhibition, as well as γ-secretase modulation, results in specific increases and decreases in tau protein levels. These data demonstrate that APP metabolism regulates tau proteostasis and suggest that the relationship between APP processing and tau is not mediated solely through extracellular Aβ signaling to neurons.This research was supported by grants from Alzheimer’s Research UK and the Wellcome Trust (to F.J.L.) and core funding to the Gurdon Trust from the Wellcome Trust and Cancer Research UK. N.S. was supported by a Woolf-Fisher Trust (NZ) PhD studentship. H.Z. was supported by the Wolfson Centre at UCL, and the UCLH Dementia BRU provided financial support for the collection of patient materials. F.J.L. is a Wellcome Trust Senior Investigator, K.B. is a Torsten So¨ derberg Academy Professor, and H.Z. is a Wallenberg Academy Fellow.This is the final version. It was first published by Elsevier at http://www.sciencedirect.com/science/article/pii/S2211124715003599

    Microwave Spectroscopy of Thermally Excited Quasiparticles in YBa_2Cu_3O_{6.99}

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    We present here the microwave surface impedance of a high purity crystal of YBa2Cu3O6.99YBa_2Cu_3O_{6.99} measured at 5 frequencies between 1 and 75 GHz. This data set reveals the main features of the conductivity spectrum of the thermally excited quasiparticles in the superconducting state. Below 20 K there is a regime of extremely long quasiparticle lifetimes, due to both the collapse of inelastic scattering below TcT_c and the very weak impurity scattering in the high purity BaZrO3BaZrO_3-grown crystal used in this study. Above 20 K, the scattering increases dramatically, initially at least as fast as T4T^4.Comment: 13 pages with 10 figures. submitted to Phys Rev
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