569 research outputs found

    Stationary shapes of deformable particles moving at low Reynolds numbers

    Full text link
    Lecture Notes of the Summer School ``Microswimmers -- From Single Particle Motion to Collective Behaviour'', organised by the DFG Priority Programme SPP 1726 (Forschungszentrum J{\"{u}}lich, 2015).Comment: Pages C7.1-16 of G. Gompper et al. (ed.), Microswimmers - From Single Particle Motion to Collective Behaviour, Lecture Notes of the DFG SPP 1726 Summer School 2015, Forschungszentrum J\"ulich GmbH, Schriften des Forschungszentrums J\"ulich, Reihe Key Technologies, Vol 110, ISBN 978-3-95806-083-

    Visual or spatial isolation in ruminants.

    Get PDF
    Livestock production in intensive systems has expanded the world, always agreeing to raise production levels and economic returns, respectively. This vertical integration of livestock has led to some adjustments in management and also on the premises, which has changed the behavior of animals, coming from both visual and spatial constraints of the individual. In dairy farming, the creation of calves in individual stalls is an example of vertical integration, thus making a common practice in many countries. Knowing that the cattle are social animals that show high willingness to form social bonds with other individuals of the same species, some agencies have implemented laws to ensure a minimum of comfort for these animals. A systematic study of social preferences of animals and the calming effects of different animal companion familiarity are needed to document the response to separation. The objective of this review, present and discuss the effect of spatial isolation and/or visual on the productive and behavioral responses of ruminant animals.A produção animal em sistemas intensivos tem se ampliado no mundo, sempre visando à elevação de índices produtivos e retorno econômico, respectivamente. Essa verticalização da pecuária tem provocado algumas adaptações de manejo e também nas instalações, que tem alterado o comportamento dos animais, oriundo das restrições tanto visual como espacial do indivíduo. Na pecuária leiteira, a criação de bezerros em baias individuais é um exemplo dessa verticalização, tornando então uma prática comum em muitos países. Sabendo que os bovinos são animais sociais que mostram alta disponibilidade para formar vínculo social com outros indivíduos da mesma espécie, alguns órgãos têm implantado legislações para garantir um mínimo de conforto para esses animais. Um estudo sistemático das preferências sociais dos animais e os efeitos calmantes do animal companheiro de familiaridade diferente são necessários para documentar a resposta à separação. Objetivou-se com esta revisão, apresentar e discutir o efeito do isolamento espacial e/ou visual sobre as respostas produtivas e comportamentais de animais ruminantes

    Genuine Correlations of Like-Sign Particles in Hadronic Z0 Decays

    Get PDF
    Correlations among hadrons with the same electric charge produced in Z0 decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized factorial cumulants up to fourth order are used to measure genuine particle correlations as a function of the size of phase space domains in rapidity, azimuthal angle and transverse momentum. Both all-charge and like-sign particle combinations show strong positive genuine correlations. One-dimensional cumulants initially increase rapidly with decreasing size of the phase space cells but saturate quickly. In contrast, cumulants in two- and three-dimensional domains continue to increase. The strong rise of the cumulants for all-charge multiplets is increasingly driven by that of like-sign multiplets. This points to the likely influence of Bose-Einstein correlations. Some of the recently proposed algorithms to simulate Bose-Einstein effects, implemented in the Monte Carlo model PYTHIA, are found to reproduce reasonably well the measured second- and higher-order correlations between particles with the same charge as well as those in all-charge particle multiplets.Comment: 26 pages, 6 figures, Submitted to Phys. Lett.

    Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays

    Full text link
    The lifetime and oscillation frequency of the B0 meson has been measured using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP. The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the production flavour of the B0 mesons was determined using a combination of tags from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d = 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.

    Measurement of the partial widths of the Z into up- and down-type quarks

    Full text link
    Using the entire OPAL LEP1 on-peak Z hadronic decay sample, Z -> qbarq gamma decays were selected by tagging hadronic final states with isolated photon candidates in the electromagnetic calorimeter. Combining the measured rates of Z -> qbarq gamma decays with the total rate of hadronic Z decays permits the simultaneous determination of the widths of the Z into up- and down-type quarks. The values obtained, with total errors, were Gamma u = 300 ^{+19}_{-18} MeV and Gamma d = 381 ^{+12}_{-12} MeV. The results are in good agreement with the Standard Model expectation.Comment: 22 pages, 5 figures, Submitted to Phys. Letts.

    Measurement of Rb in e+e- Collisions at 182 - 209 GeV

    Full text link
    Measurements of Rb, the ratio of the bbbar cross-section to the qqbar cross- section in e+e- collisions, are presented. The data were collected by the OPAL experiment at LEP at centre-of-mass energies between 182 GeV and 209 GeV. Lepton, lifetime and event shape information is used to tag events containing b quarks with high efficiency. The data are compatible with the Standard Model expectation. The mean ratio of the eight measurements reported here to the Standard Model prediction is 1.055+-0.031+-0.037, where the first error is statistical and the second systematic.Comment: 21 pages, 5 figures, Submitted to Phys. Letts

    WW Production Cross Section and W Branching Fractions in e+e- Collisions at 189 GeV

    Get PDF
    From a data sample of 183 pb^-1 recorded at a center-of-mass energy of roots = 189 GeV with the OPAL detector at LEP, 3068 W-pair candidate events are selected. Assuming Standard Model W boson decay branching fractions, the W-pair production cross section is measured to be sigmaWW = 16.30 +- 0.34(stat.) +- 0.18(syst.) pb. When combined with previous OPAL measurements, the W boson branching fraction to hadrons is determined to be 68.32 +- 0.61(stat.) +- 0.28(syst.) % assuming lepton universality. These results are consistent with Standard Model expectations.Comment: 22 pages, 5 figures, submitted to Phys. Lett.
    corecore