3,181 research outputs found

    Remote sensing of floe size distribution and surface topography

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    Floe size can be measured by several properties p- for instance, area or mean caliper diameter. Two definitions of floe size distribution seem particularly useful. F(p), the fraction of area covered by floes no smaller than p; and N(p), the number of floes per unit area no smaller than p. Several summertime distributions measured are a graph, their slopes range from -1.7 to -2.5. The variance of an estimate is also calculated

    Structure in the Epislon Eridani dusty disk caused by mean motion resonances with a 0.3 eccentricity planet at periastron

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    The morphology of the epsilon Eridani dust ring is reproduced by a numerical simulation of dust particles captured into the 5:3 and 3:2 exterior mean-motion resonances with a 0.3 eccentricity 10^-4 solar mass planet at periastron at a semi-major axis of 40 AU. The morphology will differ when the planet is at aphelion, in about 140 years. Moderate eccentricity planets in outer extra-solar systems will cause observable variations in the morphology of associated dusty rings.Comment: accepted to ApJ

    The Concepts of Reliability and Homogeneity

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67956/2/10.1177_001316445001000103.pd

    Turbulence driven by outflow-blown cavities in the molecular cloud of NGC 1333

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    Outflows from young stellar objects have been identified as a possible source of turbulence in molecular clouds. To investigate the relationship between outflows, cloud dynamics and turbulence, we compare the kinematics of the molecular gas associated with NGC 1333, traced in 13CO(1-0), with the distribution of young stellar objects (YSOs) within. We find a velocity dispersion of ~ 1-1.6 km/s in 13CO that does not significantly vary across the cloud, and is uncorrelated with the number of nearby young stellar outflows identified from optical and submillimeter observations. However, from velocity channel maps we identify about 20 cavities or depressions in the 13CO intensity of scales > 0.1-0.2 pc and velocity widths 1-3 km/s. The cavities exhibit limb brightened rims in both individual velocity channel maps and position velocity diagrams, suggesting that they are slowly expanding. We interpret these cavities to be remnants of past YSO outflow activity: If these cavities are presently empty, they would fill in on time scales of a million years. This can exceed the lifetime of a YSO outflow phase, or the transit time of the central star through the cavity, explaining the the absence of any clear correlation between the cavities and YSO outflows. We find that the momentum and energy deposition associated with the expansion of the cavities is sufficient to power the turbulence in the cloud. In this way we conclude that the cavities are an important intermediary step between the conversion of YSO outflow energy and momentum into cloud turbulent motions.Comment: Accepted for publication in ApJ. Check out http://astro.pas.rochester.edu/~aquillen/coolpics.html for channel map and PosVel movies of N133

    Constraints on the R-parity- and Lepton-Flavor-Violating Couplings from B0 Decats to Two Charged Leptons

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    We derive the upper bounds on certain products of R-parity- and lepton-flavor-violating couplings from the decays of the neutral BB meson into two charged leptons. These modes of B0B^0 decays can constrain the product combinations of the couplings with one or more heavy generation indices. We find that most of these bounds are stronger than the previous ones.Comment: Table is changed; version to appear in Phys. Rev.

    Analysis of Charge Asymmetry in Rare Dilepton BB Decays

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    We analyze forward-backward charge asymmetry of the lepton production in rare decays BXsl+lB\rightarrow X_s l^+l^- and BKl+lB\rightarrow K^* l^+l^-, including vector-resonance effects. Certain regions of phase space, in which the asymmetry is sensitive to individual short-distance coefficients, are pointed out. In particular, we suggest a method to test the coupling of the leptonic axial vector current to the left-handed quark current experimentally.Comment: 27 pages, 4 figures available up to requiremen

    Isospin-mixing corrections for fp-shell Fermi transitions

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    Isospin-mixing corrections for superallowed Fermi transitions in {\it fp}-shell nuclei are computed within the framework of the shell model. The study includes three nuclei that are part of the set of nine accurately measured transitions as well as five cases that are expected to be measured in the future at radioactive-beam facilities. We also include some new calculations for 10^{10}C. With the isospin-mixing corrections applied to the nine accurately measured ftft values, the conserved-vector-current hypothesis and the unitarity condition of the Cabbibo-Kobayashi-Maskawa (CKM) matrix are tested.Comment: 13 pages plus five tables. revtex macro

    Using bsγb \to s\gamma to Probe Top Quark Couplings

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    Possible anomalous couplings of the top-quark to on-shell photons and gluons are constrained by the recent results of the CLEO Collaboration on both inclusive and exclusive radiative BB decays. We find that the process \bsg\ can lead to reasonable bounds on both the anomalous electric and magnetic dipole moments of the top-quark, while essentially no limits are obtained on the corresponding chromoelectric and chromomagnetic moments, which enter the expression for the decay rate only through operator mixing.Comment: 10 pages plus 6 figures (available by request), LaTex, ANL-HEP-PR-93-3
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