19,120 research outputs found

    Viscous dark fluid universe

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    We investigate the cosmological perturbation dynamics for a universe consisting of pressureless baryonic matter and a viscous fluid, the latter representing a unified model of the dark sector. In the homogeneous and isotropic background the \textit{total} energy density of this mixture behaves as a generalized Chaplygin gas. The perturbations of this energy density are intrinsically non-adiabatic and source relative entropy perturbations. The resulting baryonic matter power spectrum is shown to be compatible with the 2dFGRS and SDSS (DR7) data. A joint statistical analysis, using also Hubble-function and supernovae Ia data, shows that, different from other studies, there exists a maximum in the probability distribution for a negative present value q0≈−0.53q_0 \approx - 0.53 of the deceleration parameter. Moreover, while previous descriptions on the basis of generalized Chaplygin gas models were incompatible with the matter power spectrum data since they required a much too large amount of pressureless matter, the unified model presented here favors a matter content that is of the order of the baryonic matter abundance suggested by big-bang nucleosynthesis.Comment: 19 pages, 6 figure

    Measuring the Higgs Branching Fraction into two Photons at Future Linear \ee Colliders

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    We examine the prospects for measuring the \gaga branching fraction of a Standard Model-like Higgs boson with a mass of 120 GeV at the future TESLA linear \ee collider, assuming an integrated luminosity of 1 ab−1^{-1} and center-of-mass energies of 350 GeV and 500 GeV. The Higgs boson is produced in association with a fermion pair via the Higgsstrahlung process \ee →ZH\to ZH, with Z→Z \to \qq or \nn, or the WW fusion reaction e+e−→νeνeˉHe^+e^- \to \nu_e \bar{\nu_e} H. A relative uncertainty on BF(\hgg) of~16% can be achieved in unpolarized \ee collisions at s\sqrt{s}=~500 GeV, while for s\sqrt{s}=~350 GeV the expected precision is slightly poorer. With appropriate initial state polarizations Δ\DeltaBF(\hgg)/BF(\hgg) can be improved to 10%. If this measurement is combined with the expected error for the total Higgs width, a precision of 10% on the \gaga Higgs boson partial width appears feasible.Comment: 14 pages, 5 figure

    Coal-shale interface detection system

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    A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through

    The freezing properties, stability, and physical qualities of chocolate ice cream

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    Publication authorized February 14, 1933."The data presented in this bulletin were taken from a thesis submitted by the junior author in fulfillment of the thesis requirement for the degree of Master of Arts in the Graduate School of the University of Missouri"--P. [3].Digitized 2007 AES.Includes bibliographical references (page 24)

    Constraining the History of the Sagittarius Dwarf Galaxy Using Observations of its Tidal Debris

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    We present a comparison of semi-analytic models of the phase-space structure of tidal debris with observations of stars associated with the Sagittarius dwarf galaxy (Sgr). We find that many features in the data can be explained by these models. The properties of stars 10-15 degrees away from the center of Sgr --- in particular, the orientation of material perpendicular to Sgr's orbit (c.f. Alard 1996) and the kink in the velocity gradient (Ibata et al 1997) --- are consistent with those expected for unbound material stripped during the most recent pericentric passage ~50 Myrs ago. The break in the slope of the surface density seen by Mateo, Olszewski & Morrison (1998) at ~ b=-35 can be understood as marking the end of this material. However, the detections beyond this point are unlikely to represent debris in a trailing streamer, torn from Sgr during the immediately preceding passage ~0.7 Gyrs ago, but are more plausibly explained by a leading streamer of material that was lost more that 1 Gyr ago and has wrapped all the way around the Galaxy. The observations reported in Majewski et al (1999) also support this hypothesis. We determine debris models with these properties on orbits that are consistent with the currently known positions and velocities of Sgr in Galactic potentials with halo components that have circular velocities v_circ=140-200 km/s. The best match to the data is obtained in models where Sgr currently has a mass of ~10^9 M_sun and has orbited the Galaxy for at least the last 1 Gyr, during which time it has reduced its mass by a factor of 2-3, or luminosity by an amount equivalent to ~10% of the total luminosity of the Galactic halo. These numbers suggest that Sgr is rapidly disrupting and unlikely to survive beyond a few more pericentric passages.Comment: 19 pages, 5 figures, accepted to Astronomical Journa

    The relation of different ingredients of ice cream to its freezing and supercooling points

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    Publication authorized February 14, 1938.Digitized 2007 AES.Includes bibliographical references

    The effect of the sugar content in the manufacture of commercial ice cream

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    Publication authorized August 23, 1924.Digitized 2007 AES.Includes bibliographical references

    The effect of different pasteurization temperatures on several of the physical properties of milk

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    Publication authorized September 3, 1929

    The deleterious effect of freezing on several of the physical properties of milk

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    Publication authorized January 7, 1927.Digitized 2007 AES.Includes bibliographical references (page 14)

    The relation of several ingredients to the manufacture of commercial ice cream

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    Caption title.Digitized 2006 AES MoU
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