544 research outputs found

    Sequence of the OXA2 β-lactamase: comparison with other penicillin-reactive enzymes

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    AbstractThe nucleotide sequence of the unusual plasmid-mediated OXA2 β-lactamase is presented, and compared with other β-lactamases. The OXA2 enzyme has similar features at the presumed active site, but no other significant regions ofhomology with other penicillin-reactive enzymes. The active site homology may therefore represent convergent evolution of otherwise dissimilar genes

    Population Monte Carlo algorithms

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    We give a cross-disciplinary survey on ``population'' Monte Carlo algorithms. In these algorithms, a set of ``walkers'' or ``particles'' is used as a representation of a high-dimensional vector. The computation is carried out by a random walk and split/deletion of these objects. The algorithms are developed in various fields in physics and statistical sciences and called by lots of different terms -- ``quantum Monte Carlo'', ``transfer-matrix Monte Carlo'', ``Monte Carlo filter (particle filter)'',``sequential Monte Carlo'' and ``PERM'' etc. Here we discuss them in a coherent framework. We also touch on related algorithms -- genetic algorithms and annealed importance sampling.Comment: Title is changed (Population-based Monte Carlo -> Population Monte Carlo). A number of small but important corrections and additions. References are also added. Original Version is read at 2000 Workshop on Information-Based Induction Sciences (July 17-18, 2000, Syuzenji, Shizuoka, Japan). No figure

    A classification of smooth embeddings of 3-manifolds in 6-space

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    We work in the smooth category. If there are knotted embeddings S^n\to R^m, which often happens for 2m<3n+4, then no concrete complete description of embeddings of n-manifolds into R^m up to isotopy was known, except for disjoint unions of spheres. Let N be a closed connected orientable 3-manifold. Our main result is the following description of the set Emb^6(N) of embeddings N\to R^6 up to isotopy. The Whitney invariant W : Emb^6(N) \to H_1(N;Z) is surjective. For each u \in H_1(N;Z) the Kreck invariant \eta_u : W^{-1}u \to Z_{d(u)} is bijective, where d(u) is the divisibility of the projection of u to the free part of H_1(N;Z). The group Emb^6(S^3) is isomorphic to Z (Haefliger). This group acts on Emb^6(N) by embedded connected sum. It was proved that the orbit space of this action maps under W bijectively to H_1(N;Z) (by Vrabec and Haefliger's smoothing theory). The new part of our classification result is determination of the orbits of the action. E. g. for N=RP^3 the action is free, while for N=S^1\times S^2 we construct explicitly an embedding f : N \to R^6 such that for each knot l:S^3\to R^6 the embedding f#l is isotopic to f. Our proof uses new approaches involving the Kreck modified surgery theory or the Boechat-Haefliger formula for smoothing obstruction.Comment: 32 pages, a link to http://www.springerlink.com added, to appear in Math. Zei

    On complex surfaces diffeomorphic to rational surfaces

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    In this paper we prove that no complex surface of general type is diffeomorphic to a rational surface, thereby completing the smooth classification of rational surfaces and the proof of the Van de Ven conjecture on the smooth invariance of Kodaira dimension.Comment: 34 pages, AMS-Te

    Towards a global platform for linking soil biodiversity data

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    Soil biodiversity is immense, with an estimated 10–100 million organisms belonging to over 5000 taxa in a handful of soil. In spite of the importance of soil biodiversity for ecosystem functions and services, information on soil species, from taxonomy to biogeographical patterns, is incomplete and there is no infrastructure to connect pre-existing or future data. Here, we propose a global platform to allow for greater access to soil biodiversity information by linking databases and repositories through a single open portal. The proposed platform would for the first time, link data on soil organisms from different global sites and biomes, and will be inclusive of all data types, from molecular sequences to morphology measurements and other supporting information. Access to soil biodiversity species records and information will be instrumental to progressing scientific research and education. Further, as demonstrated by previous biodiversity synthesis efforts, data availability is key for adapting to, and creating mitigation plans in response to global changes. With the rapid influx of soil biodiversity data, now is the time to take the first steps forward in establishing a global soil biodiversity information platform

    The influence of the political environment and destination governance on sustainable tourism development: a study of Bled, Slovenia

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    In the context of sustainable tourism development, there are many studies about the exchange process between residents and tourism, yet this issue is practically unexplored with respect to the political environment of tourism. Therefore, this paper introduces and posits that the political environment is a necessary enabler for implementing sustainable tourism. The authors extend the established three-pillar sustainability concept by adding in the political dimension. Then they surveyed how residents' positive and negative perceptions of tourism impacts determine their satisfaction with life in the tourism destination and thus their support for tourism in their community. The model was empirically tested within the context of the long-established Alpine destination of Bled in Slovenia. The findings confirm the importance of the political environment and question the sustainability of Bled's tourism development. It is suggested that the community has relatively weak destination governance due to the underdeveloped political environment. The survey expands and deepens the tourism sustainability debate by adding in the political environment and how it relates to the emerging growth of research on destination governance. The proposed model can be adapted and applied to any destination in order to improve its governance, including the implementation of sustainable tourism development

    Continuously improving the practice of cardiology

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    Guidelines for the management of patients with cardiovascular disease are designed to assist cardiologists and other physicans in their practice. Surveys are conducted to assess whether guidelines are followed in practice. The results of surveys on acute coronary syndromes, coronary revascularisation, secondary prevention, valvular heart disease and heart failure are presented. Comparing surveys conducted between 1995 and 2002, a gradual improvement in use ofsecondary preventive therapy is observed. Nevertheless, important deviations from established guidelines are noted, with a significant variation among different hospitals in the Netherlands and in other European countries. Measures for fiuther improvement of clinical practice indude more rapid treatment of patients with evolving myocardial infarction, more frequent use of clopidogrel and glycoprotein IIb/IIIa receptor blockers in patients with acute coronary syndromes, more frequent use of 5-blockers in patients with heart failure and more intense measures to encourage patients to stop smoking. Targets for the proportion ofpatients who might receive specific therapies are presented
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