Intermittent turbulence and turbulent structures in a linear magnetized plasma

Strongly intermittent turbulence is observed in the shadow of a limiter in the Large Plasma Device (LAPD) at UCLA [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Inst. {\bfseries 62}, 2875 (1991)]. The amplitude probability distribution function (PDF) of the turbulence is strongly skewed, with density depletion events (or ``holes'') dominant in the high density region and density enhancement events (or ``blobs'') dominant in the low density region. Two-dimensional cross-conditional averaging shows that the blobs are detached, outward-propagating filamentary structures with a clear dipolar potential while the holes appear to be part of a more extended turbulent structure. A statistical study of the blobs reveals a typical size of ten times the ion sound gyroradius and a typical velocity of one tenth the sound speed.Comment: 12 pages, 4 figures, to appear in Physics of Plasma

A Shplit Ticket, Half Irish, Half Chinay : Representations of Mixed-Race and Hybridity in the Turn-of-the-Century Theater

Charles Townsend\u27s 1889 adaptation of Harriet Beecher Stowe\u27s Uncle Tom\u27s Cabin features white actors playing light- and dark-skinned African-American characters, changing degrees of make-up as the script, stage business, or number of available players demands. Thomas Denison\u27s stage directions to his 1895 play, Patsy O\u27Wang, an Irish Farce with a Chinese Mix-Up, stipulates that the alternation of the half -Chinese, half-Irish cook between his two ethnic personas is key to this capital farce, and that a comedie use of the Chinese dialect is central to this. The Geezer (c. 1896), Joseph Herbert\u27s spoof of the popular musical, The Geisha, features white actors playing Chinese dignitaries, but also donning German and Irish accents. The white actors in these plays enact different paradigms of hybridity. The actors in Townsend\u27s Uncle Tom\u27s Cabin, a Melodrama in Five Acts embody conceptions of both mixed and unmixed African Americans, freely alternating between each. In Patsy O\u27Wang, the main character\u27s background is central to the story, and the lead actor moves between the two ethnicities by his accent, mannerisms, and politics. Racial mixing is central to the plot of The Geezer through Anglo actors who make themselves hybrid by appearing Chinese and appropriating a third accent, rather than the creation of racially mixed offspring

Valley and spin polarization from graphene line defect scattering

Quantum transport calculations describing electron scattering off an extended line defect in graphene are presented. The calculations include potentials from local magnetic moments recently predicted to exist on sites adjacent to the line defect. The transmission probability is derived and expressed as a function of valley, spin, and angle of incidence of an electron at the Fermi level being scattered. It is shown that the previously predicted valley polarization in a beam of transmitted electrons is not significantly influenced by the presence of the magnetic moments. These moments, however, do introduce some spin polarization, in addition to the valley polarization, albeit no more than about 20%.Comment: 6 pages, 4 figure

Graphene valley filter using a line defect

With its two degenerate valleys at the Fermi level, the band structure of graphene provides the opportunity to develop unconventional electronic applications. Herein, we show that electron and hole quasiparticles in graphene can be filtered according to which valley they occupy without the need to introduce confinement. The proposed valley filter is based on scattering off a recently observed line defect in graphene. Quantum transport calculations show that the line defect is semitransparent and that quasiparticles arriving at the line defect with a high angle of incidence are transmitted with a valley polarization near 100%.Comment: 5 pages, 4 figure

Spectral Graph Forge: Graph Generation Targeting Modularity

Community structure is an important property that captures inhomogeneities common in large networks, and modularity is one of the most widely used metrics for such community structure. In this paper, we introduce a principled methodology, the Spectral Graph Forge, for generating random graphs that preserves community structure from a real network of interest, in terms of modularity. Our approach leverages the fact that the spectral structure of matrix representations of a graph encodes global information about community structure. The Spectral Graph Forge uses a low-rank approximation of the modularity matrix to generate synthetic graphs that match a target modularity within user-selectable degree of accuracy, while allowing other aspects of structure to vary. We show that the Spectral Graph Forge outperforms state-of-the-art techniques in terms of accuracy in targeting the modularity and randomness of the realizations, while also preserving other local structural properties and node attributes. We discuss extensions of the Spectral Graph Forge to target other properties beyond modularity, and its applications to anonymization

Transonic Elastic Model for Wiggly Goto-Nambu String

The hitherto controversial proposition that a ``wiggly" Goto-Nambu cosmic string can be effectively represented by an elastic string model of exactly transonic type (with energy density $U$ inversely proportional to its tension $T$) is shown to have a firm mathematical basis.Comment: 8 pages, plain TeX, no figure