7,229 research outputs found

    Two-Sided Derivatives for Regular Expressions and for Hairpin Expressions

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    The aim of this paper is to design the polynomial construction of a finite recognizer for hairpin completions of regular languages. This is achieved by considering completions as new expression operators and by applying derivation techniques to the associated extended expressions called hairpin expressions. More precisely, we extend partial derivation of regular expressions to two-sided partial derivation of hairpin expressions and we show how to deduce a recognizer for a hairpin expression from its two-sided derived term automaton, providing an alternative proof of the fact that hairpin completions of regular languages are linear context-free.Comment: 28 page

    To the practical design of the optical lever intracavity topology of gravitational-wave detectors

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    The QND intracavity topologies of gravitational-wave detectors proposed several years ago allow, in principle, to obtain sensitivity significantly better than the Standard Quantum Limit using relatively small anount of optical pumping power. In this article we consider an improved more ``practical'' version of the optical lever intracavity scheme. It differs from the original version by the symmetry which allows to suppress influence of the input light amplitude fluctuation. In addition, it provides the means to inject optical pumping inside the scheme without increase of optical losses. We consider also sensitivity limitations imposed by the local meter which is the key element of the intracavity topologies. Two variants of the local meter are analyzed, which are based on the spectral variation measurement and on the Discrete Sampling Variation Measurement, correspondingly. The former one, while can not be considered as a candidate for a practical implementation, allows, in principle, to obtain the best sensitivity and thus can be considered as an ideal ``asymptotic case'' for all other schemes. The DSVM-based local meter can be considered as a realistic scheme but its sensitivity, unfortunately, is by far not so good just due to a couple of peculiar numeric factors specific for this scheme. From our point of view search of new methods of mechanical QND measurements probably based on improved DSVM scheme or which combine the local meter with the pondermotive squeezing technique, is necessary.Comment: 27 pages, 6 figure

    The religious switching of immigrants in Canada

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    Although the contribution of immigration and religious switching to the changing religious landscape in Canada seems well established, we lack knowledge on the religious switching of immigrants. In this study, we address if and to what extent immigrants to Canada change religion after their arrival. We use data on religious affiliation and other demographic characteristics from the 1981, 1991 and 2001 censuses, as well as from the 2011 National Household Survey and the 2002 Ethnic Diversity Survey to study, in a demographic perspective, the magnitude of religious switching among the immigrant population in Canada across the 30 years of observation. We compare it with the religious switching of the Canadian-born population and look for characteristics associated with religious switching among the population of immigrants. The results show that the patterns of religious switching of immigrants present similarities with that of the Canadian-born even if, in relative terms, net population change associated with religious switching is of a lower magnitude among the immigrant population in the most recent period. Religious background and place of birth appear to be related to religious change among immigrants in Canada

    Iron Displacements and Magnetoelastic Coupling in the Spin-Ladder Compound BaFe2Se3

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    We report long-range ordered antiferromagnetism concomitant with local iron displacements in the spin-ladder compound BaFe2_2Se3_3. Short-range magnetic correlations, present at room temperature, develop into long-range antiferromagnetic order below TN_N = 256 K, with no superconductivity down to 1.8 K. Built of ferromagnetic Fe4_4 plaquettes, the magnetic ground state correlates with local displacements of the Fe atoms. These iron displacements imply significant magnetoelastic coupling in FeX4_4-based materials, an ingredient hypothesized to be important in the emergence of superconductivity. This result also suggests that knowledge of these local displacements is essential for properly understanding the electronic structure of these systems. As with the copper oxide superconductors two decades ago, our results highlight the importance of reduced dimensionality spin ladder compounds in the study of the coupling of spin, charge, and atom positions in superconducting materials

    Genetic heterogeneity of hepatitis E virus in Darfur, Sudan, and neighboring Chad.

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    The within-outbreak diversity of hepatitis E virus (HEV) was studied during the outbreak of hepatitis E that occurred in Sudan in 2004. Specimens were collected from internally displaced persons living in a Sudanese refugee camp and two camps implanted in Chad. A comparison of the sequences in the ORF2 region of 23 Sudanese isolates and five HEV samples from the two Chadian camps displayed a high similarity (>99.7%) to strains belonging to Genotype 1. But four isolates collected in one of the Chadian camps were close to Genotype 2. Circulation of divergent strains argues for possible multiple sources of infection

    Diochus cleidecostae, a new species from the Brazilian Amazon and a discussion of the sexual dimorphism on sternum VIII (Coleoptera: Staphylinidae: Staphylininae: Diochini)

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    Diochus Erichson is a worldwide rove beetle genus with species found in forest floor litter. Three species of Diochus were recently collected in northern Brazil, one of them considered as new and herein described. Within Diochus nanus-group, D. cleidecostae sp. nov. differs from D. apicipennis Cameron, D. nanus Erichson and D. perplexus Cameron by the aedeagus with clearing trifurcate apex of parameres; and differs from D. parvulus Kraatz by the three apical long setae of parameres distributed on ventral and dorsal lobes. A previous key to the D. nanus-group is updated to include the new species. Here we also report for the first time D. santacatarinae Irmler and D. parvulus from Pará state, Brazil. Finally, a discussion about the sexual dimorphism on sternum VIII is also provided for the genus

    Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand

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    Pliocene limestone formations in central Hawke's Bay (eastern North Island, New Zealand) accumulated on and near the margins of a narrow forearc basin seaway within the convergent Australia/Pacific plate boundary zone. The active tectonic setting and varied paleogeographic features of the limestone units investigated, in association with probable glacioeustatic sea-level fluctuations, resulted in complex stratigraphic architectures and contrasting types of carbonate accumulation on either side of the seaway. Here, we recognise recurring patterns of sedimentary facies, and sequences and systems tracts bounded by key physical surfaces within the limestone sheets. The facies types range from Bioclastic (B) to Siliciclastic (S) end-members via Mixed (M) carbonate-siliciclastic deposits. Skeletal components are typical cool-water associations dominated by epifaunal calcitic bivalves, bryozoans, and especially barnacles. Siliciclastic contents vary from one formation to another, and highlight siliciclastic-rich limestone units in the western ranges versus siliciclastic-poor limestone units in the eastern coastal hills. Heterogeneities in facies types, stratal patterns, and also in diagenetic pathways between eastern and western limestone units are considered to originate in the coeval occurrence in different parts of the forearc basin of two main morphodynamic carbonate systems over time

    Novel microsatellite DNA markers indicate strict parthenogenesis and few genotypes in the invasive willow sawfly Nematus oligospilus

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    Invasive organisms can have major impacts on the environment. Some invasive organisms are parthenogenetic in their invasive range and, therefore, exist as a number of asexual lineages (=clones). Determining the reproductive mode of invasive species has important implications for understanding the evolutionary genetics of such species, more especially, for management-relevant traits. The willow sawfly Nematus oligospilus Förster (Hymenoptera: Tenthredinidae) has been introduced unintentionally into several countries in the Southern Hemisphere where it has subsequently become invasive. To assess the population expansion, reproductive mode and host-plant relationships of this insect, microsatellite markers were developed and applied to natural populations sampled from the native and expanded range, along with sequencing of the cytochrome-oxidase I mitochondrial DNA (mtDNA) region. Other tenthredinids across a spectrum of taxonomic similarity to N. oligospilus and having a range of life strategies were also tested. Strict parthenogenesis was apparent within invasive N. oligospilus populations throughout the Southern Hemisphere, which comprised only a small number of genotypes. Sequences of mtDNA were identical for all individuals tested in the invasive range. The microsatellite markers were used successfully in several sawfly species, especially Nematus spp. and other genera of the Nematini tribe, with the degree of success inversely related to genetic divergence as estimated from COI sequences. The confirmation of parthenogenetic reproduction in N. oligospilus and the fact that it has a very limited pool of genotypes have important implications for understanding and managing this species and its biology, including in terms of phenotypic diversity, host relationships, implications for spread and future adaptive change. It would appear to be an excellent model study system for understanding evolution of invasive parthenogens that diverge without sexual reproduction and genetic recombinatio
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