414 research outputs found

    All the Conditions of Effective Foreign Aid

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    The conclusion that foreign aid will promote economic growth only when allocated towards good policy regimes has been the subject of considerable debate. Aid effectiveness researchers have variously sought to falsify this result or to find other individual conditions of aid effectiveness. However, economic theory suggests that any factor which influences the expected returns to investment may influence the effect of aid on growth even when aid is partly diverted to consumption. To investigate this hypothesis, �all� of the hypothesized conditions of aid effectiveness are individually tested in a cross-country growth specification. From these tests the most significant and robust individual interactions are simultaneously modeled, thereby deriving multiple conditions of aid effectiveness. The paper concludes that aid is more effective in economies experiencing economic shocks or recovering from war, and less effective in countries which are geographically disadvantaged or at war. We also find a previously unidentified condition of aid ineffectiveness: the inflow of foreign direct investment. This finding renews a justified interest in the policy-aid-growth nexus, insofar as domestic policy determines the distribution of aid and FDI flows, which appear to act as substitutes in the growth process.

    Epistemic and social scripts in computer-supported collaborative learning

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    Collaborative learning in computer-supported learning environments typically means that learners work on tasks together, discussing their individual perspectives via text-based media or videoconferencing, and consequently acquire knowledge. Collaborative learning, however, is often sub-optimal with respect to how learners work on the concepts that are supposed to be learned and how learners interact with each other. One possibility to improve collaborative learning environments is to conceptualize epistemic scripts, which specify how learners work on a given task, and social scripts, which structure how learners interact with each other. In this contribution, two studies will be reported that investigated the effects of epistemic and social scripts in a text-based computer-supported learning environment and in a videoconferencing learning environment in order to foster the individual acquisition of knowledge. In each study the factors ‘epistemic script’ and ‘social script’ have been independently varied in a 2×2-factorial design. 182 university students of Educational Science participated in these two studies. Results of both studies show that social scripts can be substantially beneficial with respect to the individual acquisition of knowledge, whereas epistemic scripts apparently do not to lead to the expected effects

    Telegram from O. D. Donnell to Amon G. Carter, Jr.

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    Telegram from O. D. Donnell to Amon G. Carter, Jr. upon the death of Amon Giles Carter. The telegram expresses condolences and sympathy about his death.https://mavmatrix.uta.edu/specialcollections_meachamcarterpapers/1267/thumbnail.jp

    Can competition with pasture be used to manipulate bellyache bush (Jatropha gossypiifolia L.) population biology?

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    Bellyache bush (Jatropha gossypiifolia L.) is an invasive weed that poses economic and environmental problems in northern Australia. Competition between pasture and bellyache bush was examined in North Queensland using combinations of five pasture treatments (uncut (control); cut as low, medium, and high pasture; and no pasture) and four bellyache bush densities (0, 2, 6 and 12plantsm(-2)) in a buffel grass (Cenchrus ciliaris L.) dominated pasture. The pasture treatments were applied approximately once per year but no treatments were applied directly to the bellyache bush plants. Measurements of bellyache bush flowering, seed formation, and mortality were undertaken over a 9-year period, along with monitoring the pasture basal cover and plant species diversity. Maximum flowering rates of bellyache bush occurred after 9 years (97%) in plots containing no pasture, with the lowest rates of 9% in uncut control plots. Earliest flowering (322 days after planting) and seed formation (411 days) also occurred in plots with no pasture compared with all other pasture treatments (range 1314-1393 days for seed formation to occur). No seeds were produced in uncut plots. At the end of 9 years, mortality rates of bellyache bush plants initially planted averaged 73% for treatments with some pasture compared with 55% under the no-pasture treatment. The percentage of herbaceous plant basal cover in uncut plots was increased 5-fold after 9 years, much greater than the average 2% increase recorded across the low, medium, and high pasture treatments. The number of herbaceous species in uncut plots remained largely unchanged, whereas there was an average reduction of 46% in the cut pasture treatments. Buffel grass remained the species with the greatest basal cover across all cut pasture treatments, followed by sabi grass (Urochloa mosambicensis (Hack.) Dandy) and then red Natal grass (Melinis repens (Willd.) Ziska). These results suggest that grazing strategies that maintain a healthy and competitive pasture layer may contribute to reducing the rate of spread of bellyache bush and complement traditional control techniques such as the use of herbicides

    QCD Sum Rule Analysis of the Decays BK+B \to K \ell^+ \ell^- and BK+B \to K^* \ell^+ \ell^-

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    We use QCD sum rules to calculate the hadronic matrix elements governing the rare decays BK+B \to K \ell^+ \ell^- and BK+B \to K^* \ell^+ \ell^- induced by the flavour changing neutral current bsb \to s transition. We also study relations among semileptonic and rare BK()B \to K^{(*)} decay form factors. The analysis of the invariant mass distribution of the lepton pair in BK()+B \to K^{(*)} \ell^+ \ell^- and of the angular asymmetry in BK+B \to K^* \ell^+ \ell^- provides us with interesting tests of the Standard Model and its extensions.Comment: 26 pages REVTEX + 7 figures. Some typos corrected, figure 5 and 7 modified. This version will appear on Physical Review

    Can the Mechanism for π1ηπ,ηπ\pi_1\to \eta\pi,\eta'\pi Hybrid Decays be Detected?

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    Two mechanisms for the π1\pi_1 (JPC=1+J^{PC}=1^{-+}) hybrid meson decay processes π1ηπ,ηπ\pi_1\to\eta\pi,\eta'\pi are investigated. These mechanisms are applied to ϕηγ,ηγ\phi\to\eta\gamma,\eta'\gamma and J/ψηγ,ηγJ/\psi\to\eta\gamma,\eta'\gamma decays to illustrate the validity of the decay mechanisms and to obtain independent information on the coupling of η,η\eta,\eta' to quark and gluonic operators. From this information, we find that Γ(π1ηπ)/Γ(π1ηπ)\Gamma(\pi_1\to\eta\pi)/\Gamma(\pi_1\to\eta'\pi) is substantially different in the two decay mechanisms, and hence future experimental measurements of this ratio will provide valuable information for substantiating the hybrid nature of these states and for determining the mechanism for these hybrid decays.Comment: 5 pages, revtex, 1 eps figure embedded in manuscript. Analysis and references extended in v

    Small molecules, big targets: drug discovery faces the protein-protein interaction challenge.

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    Protein-protein interactions (PPIs) are of pivotal importance in the regulation of biological systems and are consequently implicated in the development of disease states. Recent work has begun to show that, with the right tools, certain classes of PPI can yield to the efforts of medicinal chemists to develop inhibitors, and the first PPI inhibitors have reached clinical development. In this Review, we describe the research leading to these breakthroughs and highlight the existence of groups of structurally related PPIs within the PPI target class. For each of these groups, we use examples of successful discovery efforts to illustrate the research strategies that have proved most useful.JS, DES and ARB thank the Wellcome Trust for funding.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nrd.2016.2

    Sympatric woodland Myotis bats form tight-knit social groups with exclusive roost home ranges

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    Background: The structuring of wild animal populations can influence population dynamics, disease spread, and information transfer. Social network analysis potentially offers insights into these processes but is rarely, if ever, used to investigate more than one species in a community. We therefore compared the social, temporal and spatial networks of sympatric Myotis bats (M. nattereri (Natterer's bats) and M. daubentonii (Daubenton's bats)), and asked: (1) are there long-lasting social associations within species? (2) do the ranges occupied by roosting social groups overlap within or between species? (3) are M. daubentonii bachelor colonies excluded from roosting in areas used by maternity groups? Results: Using data on 490 ringed M. nattereri and 978 M. daubentonii from 379 colonies, we found that both species formed stable social groups encompassing multiple colonies. M. nattereri formed 11 mixed-sex social groups with few (4.3%) inter-group associations. Approximately half of all M. nattereri were associated with the same individuals when recaptured, with many associations being long-term (>100 days). In contrast, M. daubentonii were sexually segregated; only a quarter of pairs were associated at recapture after a few days, and inter-sex associations were not long-lasting. Social groups of M. nattereri and female M. daubentonii had small roost home ranges (mean 0.2 km2 in each case). Intra-specific overlap was low, but inter-specific overlap was high, suggesting territoriality within but not between species. M. daubentonii bachelor colonies did not appear to be excluded from roosting areas used by females. Conclusions: Our data suggest marked species- and sex-specific patterns of disease and information transmission are likely between bats of the same genus despite sharing a common habitat. The clear partitioning of the woodland amongst social groups, and their apparent reliance on small patches of habitat for roosting, means that localised woodland management may be more important to bat conservation than previously recognised
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