Deformation of geometry and bifurcation of vortex rings

We construct a smooth family of Hamiltonian systems, together with a family of group symmetries and momentum maps, for the dynamics of point vortices on surfaces parametrized by the curvature of the surface. Equivariant bifurcations in this family are characterized, whence the stability of the Thomson heptagon is deduced without recourse to the Birkhoff normal form, which has hitherto been a necessary tool.Comment: 26 page

Foreign language learning in the third age: A pilot feasibility study on cognitive, socio-affective and linguistic drivers and benefits in relation to previous bilingualism of the learner

While there is a growing body of research on second language acquisition in children and prime-of-life learners, much remains to be explored about how older adults learn a new language and how good additional language learning is for them (see e.g. Mackey & Sachs, 2012). In this study we present the findings of a longitudinal pilot study in which 12 German-speaking subjects, half of them German-Slovenian bilinguals, between 63 and 90 years of age attended a four-week intensive English course for beginners, and were tested in a pre-/post-test design on a range of linguistic, cognitive, and socio-affective parameters. The results of non-parametric statistical tests and qualitative analyses suggest that: (1) the learning of an additional language in the third age can contribute to healthy and active aging, as it has a positive effect on executive function, (linguistic) self-confidence, autonomy, communicative skills and overall well-being, irrespective of age and prior language knowledge (bilingualism); and (2) age-related social, psychological and contextual factors seem to play as significant a role as strictly maturational factors. Such research promises in due course to inform adult educators about the establishment of relevant third-age learner profiles as well as the design of individualized third-age language training

Microbial taxonomy in the post-genomic era: Rebuilding from scratch?

Microbial taxonomy should provide adequate descriptions of bacterial, archaeal, and eukaryotic microbial diversity in ecological, clinical, and industrial environments. Its cornerstone, the prokaryote species has been re-evaluated twice. It is time to revisit polyphasic taxonomy, its principles, and its practice, including its underlying pragmatic species concept. Ultimately, we will be able to realize an old dream of our predecessor taxonomists and build a genomic-based microbial taxonomy, using standardized and automated curation of high-quality complete genome sequences as the new gold standard.National Science Foundation (U.S.) (NSF Grant DEB-1046413)National Science Foundation (U.S.) (NSF Grant CNS-1305112)National Science Foundation (U.S.) (NSF Grant DEB 0918333)National Science Foundation (U.S.) (NSF grant OCE 1441943)Gordon and Betty Moore FoundationUnited States. Dept. of Energy. Office of ScienceUnited States. Dept. of Energy. Office of Biological and Environmental ResearchOak Ridge National LaboratoryCarlos Chagas Filho Foundation for Research Support of the State of Rio de JaneiroBrazil. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (grant)Conselho Nacional de Pesquisas (Brazil

Polyphyly of non-bioluminescent Vibrio fischeri sharing a lux-locus deletion

available in PMC 2013 May 16This study reports the first description and molecular characterization of naturally occurring, non-bioluminescent strains of Vibrio fischeri. These ‘dark’V. fischeri strains remained non-bioluminescent even after treatment with both autoinducer and aldehyde, substrate additions that typically maximize light production in dim strains of luminous bacteria. Surprisingly, the entire lux locus (eight genes) was absent in over 97% of these dark V. fischeri strains. Although these strains were all collected from a Massachusetts (USA) estuary in 2007, phylogenetic reconstructions allowed us to reject the hypothesis that these newly described non-bioluminescent strains exhibit monophyly within the V. fischeri clade. These dark strains exhibited a competitive disadvantage against native bioluminescent strains when colonizing the light organ of the model V. fischeri host, the Hawaiian bobtail squid Euprymna scolopes. Significantly, we believe that the data collected in this study may suggest the first observation of a functional, parallel locus-deletion event among independent lineages of a non-pathogenic bacterial species.National Institutes of Health (U.S.) (NIH Molecular Biosciences (5T32GM007215-35))National Institutes of Health (U.S.) (NIH Microbes in Health and Disease, training grant (2T32AI055397-07))Gordon and Betty Moore FoundationBroad Institute of MIT and Harvard (SPARC programme)National Science Foundation (U.S.) (NSF IOS 0841507)National Institutes of Health (U.S.) (NIH R01 RR12294)National Science Foundation (U.S.) (NSF Microbial Systems in the Biosphere programme)Woods Hole Center for Oceans & Human Healt

Genotypic diversity within a natural coastal bacterioplankton population

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 307 (2005): 1311-1313, doi:10.1126/science.1106028.The genomic diversity and relative importance of unique genotypes within natural bacterial populations has remained largely unknown. Here, we analyze the diversity and annual dynamics of a group of coastal bacterioplankton (>99% 16S rRNA identity to Vibrio splendidus). We show that this group consists of at least a thousand distinct genotypes, each occurring at extremely low environmental concentrations (on average <1 cell/ml). Overall, the genomes show extensive allelic diversity and size variation. Individual genotypes rarely recurred in samples and allelic distribution did not show spatial or temporal substructure. Ecological considerations suggest that much genotypic and possibly phenotypic variation within natural populations should be considered neutral.This work was supported by grants from the Department of Energy Genomes to Life program and the National Science Foundation. Sequences have been submitted to Genbank under accession numbers AY836800-AY837464

Социальная ответственность бизнеса: опыт внедрения, характерные черты и особенности

Целью написания данной статьи является изучения опыта украинских предприятий (компаний) с наилучшими показателями в сфере социальной политики, выявление и анализ особенностей их реализации для разработки концептуального подхода к формированию модели внедрения принципов социальной ответственности в других компаниях (на предприятиях).Изучен опыт лучших компаний Украины в сфере корпоративной социальной ответственности; выявлены характерные черты и особенности разработки социальной политики в компании. Предложен концептуальный подход к формированию модели внедрения принципов социальной ответственности бизнеса.Вивчений досвід кращих компаній України в сфері соціальної відповідальності; виявлені характерні риси та особливості розробки соціальної політики в компанії. Запропонований концептуальний підхід до формування моделі впровадження принципів соціальної відповідальності бізнесу.The experience of the best Ukrainian companies in the sphere of the corporate social responsibility is studied; the personal traits and features of the development of social policy in a company are exposed. The conceptual approach is proposed to the formation of model of business social responsibility principles introduction

Compact Cryogenic Source of Periodic Hydrogen and Argon Droplet Beams for Relativistic Laser-Plasma Generation

We present a cryogenic source of periodic streams of micrometer-sized hydrogen and argon droplets as ideal mass-limited target systems for fundamental intense laser-driven plasma applications. The highly compact design combined with a high temporal and spatial droplet stability makes our injector ideally suited for experiments using state-of-the-art high-power lasers in which a precise synchronization between the laser pulses and the droplets is mandatory. We show this by irradiating argon droplets with multi-Terawatt pulses.Comment: To be published in Review of Scientific Instrument

Point vortices on the sphere: a case with opposite vorticities

We study systems formed of 2N point vortices on a sphere with N vortices of strength +1 and N vortices of strength -1. In this case, the Hamiltonian is conserved by the symmetry which exchanges the positive vortices with the negative vortices. We prove the existence of some fixed and relative equilibria, and then study their stability with the ``Energy Momentum Method''. Most of the results obtained are nonlinear stability results. To end, some bifurcations are described.Comment: 35 pages, 9 figure

The implications of a Silurian and other thylacocephalan crustaceans for the functional morphology and systematic affinities of the group

Background: Thylacocephala is a group of enigmatic extinct arthropods. Here we provide a full description of the oldest unequivocal thylacocephalan, a new genus and species Thylacares brandonensis, which is present in the Silurian Waukesha fauna from Wisconsin, USA. We also present details of younger, Jurassic specimens, from the Solnhofen lithographic limestones, which are crucial to our interpretation of the systematic position of Thylacocephala. In the past, Thylacocephala has been interpreted as a crustacean ingroup and as closely related to various groups such as cirripeds, decapods or remipeds. Results: The Waukesha thylacocephalan, Thylacares brandonensis n. gen. n. sp., bears compound eyes and raptorial appendages that are relatively small compared to those of other representatives of the group. As in other thylacocephalans the large bivalved shield encloses much of the entire body. The shield lacks a marked optical notch. The eyes, which project just beyond the shield margin, appear to be stalked. Head appendages, which may represent antennulae, antennae and mandibles, appear to be present. The trunk is comprised of up to 22 segments. New details observed on thylacocephalans from the Jurassic Solnhofen lithographic limestones include antennulae and antennae of Mayrocaris bucculata, and endites on the raptorial appendages and an elongate last trunk appendage in Clausocaris lithographica. Preserved features of the internal morphology in C. lithographica include the muscles of the raptorial appendage and trunk. Conclusions: Our results indicate that some `typical' thylacocephalan characters are unique to the group; these autapomorphies contribute to the difficulty of determining thylacocephalan affinities. While the new features reported here are consistent with a eucrustacean affinity, most previous hypotheses for the position of Thylacocephala within Eucrustacea (as Stomatopoda, Thecostraca or Decapoda) are shown to be unlikely. A sister group relationship to Remipedia appears compatible with the observed features of Thylacocephala but more fossil evidence is required to test this assertion. The raptorial appendages of Thylacocephala most likely projected 45 degrees abaxially instead of directly forward as previously reconstructed. The overall morphology of thylacocephalans supports a predatory mode of life