5,032 research outputs found
The cathode region of a quasi-steady magnetoplasmadynamic arcjet, supplement 8
Electric and magnetic field measurements in cathode region of quasi-steady magnetoplasmadynamic arcje
NNLO predictions for Z-boson pair production at the LHC
We present a calculation of the NNLO QCD corrections to Z-boson pair
production at hadron colliders, based on the N-jettiness method for the real
radiation parts. We discuss the size and shape of the perturbative corrections
along with their associated scale uncertainties and compare our results to
recent LHC data at TeV.Comment: 19 pages, 2 Tables, 4 figures. Version to appear in JHE
Numerical evaluation of two-loop integrals with pySecDec
We describe the program pySecDec, which factorises endpoint singularities
from multi-dimensional parameter integrals and can serve to calculate integrals
occurring in higher order perturbative calculations numerically. We focus on
the new features and on frequently asked questions about the usage of the
program.Comment: 11 pages, to appear in the proceedings of the HiggsTools Final
Meeting, IPPP, University of Durham, UK, September 201
An exact Riemann solver based solution for regular shock refraction
We study the classical problem of planar shock refraction at an oblique
density discontinuity, separating two gases at rest. When the shock impinges on
the density discontinuity, it refracts and in the hydrodynamical case 3 signals
arise. Regular refraction means that these signals meet at a single point,
called the triple point.
After reflection from the top wall, the contact discontinuity becomes
unstable due to local Kelvin-Helmholtz instability, causing the contact surface
to roll up and develop the Richtmyer-Meshkov instability. We present an exact
Riemann solver based solution strategy to describe the initial self similar
refraction phase, by which we can quantify the vorticity deposited on the
contact interface. We investigate the effect of a perpendicular magnetic field
and quantify how addition of a perpendicular magnetic field increases the
deposition of vorticity on the contact interface slightly under constant Atwood
number. We predict wave pattern transitions, in agreement with experiments, von
Neumann shock refraction theory, and numerical simulations performed with the
grid-adaptive code AMRVAC. These simulations also describe the later phase of
the Richtmyer-Meshkov instability.Comment: 21 pages, 17 figures in 41 ps-files, accepted by J. Fluid Mec
Breeding latitude predicts timing but not rate of spring migration in a widespread migratory bird in South America
Identifying the processes that determine avian migratory strategies in different environmental contexts is imperative to understanding the constraints to survival and reproduction faced by migratory birds across the planet. We compared the spring migration strategies of Fork‐tailed Flycatchers (Tyrannus s. savana) that breed at south‐temperate latitudes (i.e., austral migrants) vs. tropical latitudes (i.e., intratropical migrants) in South America. We hypothesized that austral migrant flycatchers are more time‐selected than intratropical migrants during spring migration. As such, we predicted that austral migrants, which migrate further than intratropical migrants, will migrate at a faster rate and that the rate of migration for austral migrants will be positively correlated with the onset of spring migration. We attached light‐level geolocators to Fork‐tailed Flycatchers at two tropical breeding sites in Brazil and at two south‐temperate breeding sites in Argentina and tracked their movements until the following breeding season. Of 286 geolocators that were deployed, 37 were recovered ~1 year later, of which 28 provided useable data. Rate of spring migration did not differ significantly between the two groups, and only at one site was there a significantly positive relationship between date of initiation of spring migration and arrival date. This represents the first comparison of individual migratory strategies among conspecific passerines breeding at tropical vs. temperate latitudes and suggests that austral migrant Fork‐tailed Flycatchers in South America are not more time‐selected on spring migration than intratropical migrant conspecifics. Low sample sizes could have diminished our power to detect differences (e.g., between sexes), such that further research into the mechanisms underpinning migratory strategies in this poorly understood system is necessary.Fil: Jahn, Alex. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Cereghetti, Joaquín. Universidad Nacional de La Pampa; ArgentinaFil: Cueto, Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; ArgentinaFil: Hallworth, Michael T.. Smithsonian Conservation Biology Institute; Estados UnidosFil: Levey, Douglas J.. National Science Foundation; Estados UnidosFil: Marini, Miguel Â.. Universidade do Brasília; BrasilFil: Masson, Diego. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Pizo, Marco A.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Sarasola, José Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Tuero, Diego Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin
Multicanonical reweighting for the QCD topological susceptibility
We introduce a reweighting technique which allows for a continuous sampling
of temperatures in a single simulation and employ it to compute the temperature
dependence of the QCD topological susceptibility at high temperatures. The
method determines the ratio of susceptibility between any two temperatures
within the explored temperature range. We find that the results from the method
agree with our previous determination and that it is competitive with but not
better than existing methods of determining the temperature derivative of the
susceptibility. The method may also be useful in exploring the temperature
dependence of other thermodynamical observables in QCD in a continuous way.Comment: 8 pages in 2-column format, including 5 figures and 2 table
The Cause of the Red-Green Color Change in Euglena Rubra
Euglena rubra is one of the species of Euglena in which a color change from green to red may be produced in a few minutes by the migration of pigment granules from central to peripheral positions. The purpose of the present study was to determine the color of light most effective for bringing about this change. Light sources used were direct sunlight and a 500 watt lamp. The organisms were placed between a glass slide and coverslip, and the color change was observed macrosopically and microscopically. When the experimental arrangement permitted heating of the slide to occur, the time necessary for the change was an inverse function of energy content as measured with a thermopile, regardless of the color of the light employed. This color change could also be produced by heating to about 40° C. in the dark. However, when heating was minimized by placing the slides on ice, blue light was much more effective than longer wavelengths of the same energy content. At low temperatures the end point of the color change was also much sharper than when heating of the slide was permitted. The green-red color change, therefore, may be affected by either of two factors: (1) an increase in temperature produced by either heat or radiant energy, or (2) by visible light, especially of the shorter wavelengths, in the absence of appreciable heating
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