TY  - JOUR
A1  - Jones, Geraint H.
A1  - Arridge, Christopher S.
A1  - Coates, Andrew J.
A1  - Lewis, Gethyn R.
A1  - Kanani, Sheila
A1  - Wellbrock, Anne
A1  - Young, David T.
A1  - Crary, Frank J.
A1  - Tokar, Robert L.
A1  - Wilson, R. J.
A1  - Hill, Thomas W.
A1  - Johnson, Robert E.
A1  - Mitchell, Donald G.
A1  - Schmidt, Jürgen
A1  - Kempf, Sascha
A1  - Beckmann, Uwe
A1  - Russell, Christopher T.
A1  - Jia, Y. D.
A1  - Dougherty, Michele K.
A1  - Waite, J. Hunter
A1  - Magee, Brian A.
T1  - Fine jet structure of electrically charged grains in Enceladus' plume
N2  - By traversing the plume erupting from high southern latitudes on Saturn's moon Enceladus, Cassini orbiter instruments can directly sample the material therein. Cassini Plasma Spectrometer, CAPS, data show that a major plume component comprises previously-undetected particles of nanometer scales and larger that bridge the mass gap between previously observed gaseous species and solid icy grains. This population is electrically charged both negative and positive, indicating that subsurface triboelectric charging, i.e., contact electrification of condensed plume material may occur through mutual collisions within vents. The electric field of Saturn's magnetosphere controls the jets' morphologies, separating particles according to mass and charge. Fine-scale structuring of these particles' spatial distribution correlates with discrete plume jets' sources, and reveals locations of other possible active regions. The observed plume population likely forms a major component of high velocity nanometer particle streams detected outside Saturn's magnetosphere.
Y1  - 2009
UR  - http://www.agu.org/journals/gl/
U6  - https://doi.org/10.1029/2009gl038284
SN  - 0094-8276
ER  - 
TY  - JOUR
A1  - Houlahan, Jeff E.
A1  - Currie, David J.
A1  - Cottenie, Karl
A1  - Cumming, Graeme S.
A1  - Ernest, S. K. Morgan
A1  - Findlay, C. Scott
A1  - Fuhlendorf, Samuel D.
A1  - Gaedke, Ursula
A1  - Legendre, Pierre
A1  - Magnuson, John J.
A1  - McArdle, Brian H.
A1  - Muldavin, Esteban H.
A1  - Noble, David
A1  - Russell, Robert
A1  - Stevens, Richard D.
A1  - Willis, Trevor J.
A1  - Woiwod, Ian P.
A1  - Wondzell, Steve M.
T1  - Compensatory dynamics are rare in natural ecological communities
N2  - In population ecology, there has been a fundamental controversy about the relative importance of competition- driven (density-dependent) population regulation vs. abiotic influences such as temperature and precipitation. The same issue arises at the community level; are population sizes driven primarily by changes in the abundances of cooccurring competitors (i.e., compensatory dynamics), or do most species have a common response to environmental factors? Competitive interactions have had a central place in ecological theory, dating back to Gleason, Volterra, Hutchison and MacArthur, and, more recently, Hubbell's influential unified neutral theory of biodiversity and biogeography. If competitive interactions are important in driving year-to-year fluctuations in abundance, then changes in the abundance of one species should generally be accompanied by compensatory changes in the abundances of others. Thus, one necessary consequence of strong compensatory forces is that, on average, species within communities will covary negatively. Here we use measures of community covariance to assess the prevalence of negative covariance in 41 natural communities comprising different taxa at a range of spatial scales. We found that species in natural communities tended to covary positively rather than negatively, the opposite of what would be expected if compensatory dynamics were important. These findings suggest that abiotic factors such as temperature and precipitation are more important than competitive interactions in driving year-to-year fluctuations in species abundance within communities.
Y1  - 2007
UR  - http://www.pnas.org/
U6  - https://doi.org/10.1073/pnas.0603798104
SN  - 0027-8424
ER  -