4,655 research outputs found

    Flow field prediction and analysis study for project RAM B3 Final report

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    Flow field properties in shock layer surrounding Ram B3 vehicl

    An Asymmetric Cone Model for Halo Coronal Mass Ejections

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    Due to projection effects, coronagraphic observations cannot uniquely determine parameters relevant to the geoeffectiveness of CMEs, such as the true propagation speed, width, or source location. The Cone Model for Coronal Mass Ejections (CMEs) has been studied in this respect and it could be used to obtain these parameters. There are evidences that some CMEs initiate from a flux-rope topology. It seems that these CMEs should be elongated along the flux-rope axis and the cross section of the cone base should be rather elliptical than circular. In the present paper we applied an asymmetric cone model to get the real space parameters of frontsided halo CMEs (HCMEs) recorded by SOHO/LASCO coronagraphs in 2002. The cone model parameters are generated through a fitting procedure to the projected speeds measured at different position angles on the plane of the sky. We consider models with the apex of the cone located at the center and surface of the Sun. The results are compared to the standard symmetric cone model

    Fundamental Physical Constants: Looking from Different Angles

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    We consider fundamental physical constants which are among a few of the most important pieces of information we have learned about Nature after its intensive centuries-long studies. We discuss their multifunctional role in modern physics including problems related to the art of measurement, natural and practical units, origin of the constants, their possible calculability and variability etc

    Understanding and Challenging Populist Negativity towards Politics: The Perspectives of British Citizens

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    This article adapts and develops the idea of a cynical or ‘stealth’ understanding of politics to explore how citizens’ estrangement from formal politics is processed cognitively through a populist lens. Earlier work has shown the widespread presence of stealth attitudes in the United States and Finland. We show that stealth attitudes are also well established in Britain, demonstrate their populist character and reveal that age, newspaper readership and concerns about governing practices help predict their adoption by individuals. Yet our survey findings also reveal a larger body of positive attitudes towards the practice of democracy suggesting that there is scope for challenging populist cynicism. We explore these so-called ‘sunshine’ attitudes and connect them to the reform options favoured by British citizens. If we are to challenge populist negativity towards politics, we conclude that improving the operation of representative politics is more important than offering citizens new forms of more deliberative participation

    The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens

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    The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised. Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges. Trans-isthmian land mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies

    Isolation of Flow and Nonflow Correlations by Two- and Four-Particle Cumulant Measurements of Azimuthal Harmonics in sNN=\sqrt{s_{_{\rm NN}}} = 200 GeV Au+Au Collisions

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    A data-driven method was applied to measurements of Au+Au collisions at sNN=\sqrt{s_{_{\rm NN}}} = 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance Δη\Delta\eta-dependent and Δη\Delta\eta-independent correlations by using two- and four-particle azimuthal cumulant measurements. We identified a component of the correlation that is Δη\Delta\eta-independent, which is likely dominated by anisotropic flow and flow fluctuations. It was also found to be independent of η\eta within the measured range of pseudorapidity η<1|\eta|<1. The relative flow fluctuation was found to be 34%±2%(stat.)±3%(sys.)34\% \pm 2\% (stat.) \pm 3\% (sys.) for particles of transverse momentum pTp_{T} less than 22 GeV/cc. The Δη\Delta\eta-dependent part may be attributed to nonflow correlations, and is found to be 5%±2%(sys.)5\% \pm 2\% (sys.) relative to the flow of the measured second harmonic cumulant at Δη>0.7|\Delta\eta| > 0.7

    Studies of di-jet survival and surface emission bias in Au+Au collisions via angular correlations with respect to back-to-back leading hadrons

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    We report first results from an analysis based on a new multi-hadron correlation technique, exploring jet-medium interactions and di-jet surface emission bias at RHIC. Pairs of back-to-back high transverse momentum hadrons are used for triggers to study associated hadron distributions. In contrast with two- and three-particle correlations with a single trigger with similar kinematic selections, the associated hadron distribution of both trigger sides reveals no modification in either relative pseudo-rapidity or relative azimuthal angle from d+Au to central Au+Au collisions. We determine associated hadron yields and spectra as well as production rates for such correlated back-to-back triggers to gain additional insights on medium properties.Comment: By the STAR Collaboration. 6 pages, 2 figure

    Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at sNN=200\sqrt{s_{NN}}=200 GeV

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    Dihadron azimuthal correlations containing a high transverse momentum (\pt) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to \pp\ and \dAu\ collisions. The modification increases with the collision centrality, suggesting a path-length dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20-60\%) Au+Au collisions at \snn=200~GeV as a function of the trigger particle's azimuthal angle relative to the event plane, \phis=|\phit-\psiEP|. The azimuthal correlation is studied as a function of both the trigger and associated particle \pt. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (\zyam), are described. The away-side correlation is strongly modified, and the modification varies with \phis, which is expected to be related to the path-length that the away-side parton traverses. The pseudo-rapidity (\deta) dependence of the near-side correlation, sensitive to long range \deta correlations (the ridge), is also investigated. The ridge and jet-like components of the near-side correlation are studied as a function of \phis. The ridge appears to drop with increasing \phis while the jet-like component remains approximately constant. ...Comment: 50 pages, 39 figures, 6 table
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