Comment on "Existence of Internal Modes of Sine-Gordon Kinks"

In Ref.[1] [Phys. Rev. B. {\bf 42}, 2290 (1990)] we used a rigorous projection operator collective variable formalism for nonlinear Klein-Gordon equations to prove the continuum Sine-Gordon (SG) equation has a long lived quasimode whose frequency $\omega_s$= 1.004 $\Gamma_0$ is in the continuum just above the lower phonon band edge with a lifetime ($1/\tau_s$) = 0.0017 $\Gamma_0$. We confirmed the analytic calculations by simulations which agreed very closely with the analytic results. In Ref.[3] [Phys. Rev. E. {\bf 62}, R60 (2000)] the authors performed two numerical investigations which they asserted ``show that neither intrinsic internal modes nor quasimodes exist in contrast to previous results.'' In this paper we prove their first numerical investigation could not possibly observe the quasimode in principle and their second numerical investigation actually demonstrates the existence of the SG quasimode. Our analytic calculations and verifying simulations were performed for a stationary Sine-Gordon soliton fixed at the origin. Yet the authors in Ref.[3] state the explanation of our analytic simulations and confirming simulations are due to the Doppler shift of the phonons emitted by our stationary Sine-Gordon soliton which thus has a zero Doppler shift.Comment: 5 pages, submitted to Phys. Rev.

Coherent structures in localised and global pipe turbulence

The recent discovery of unstable travelling waves (TWs) in pipe flow has been hailed as a significant breakthrough with the hope that they populate the turbulent attractor. We confirm the existence of coherent states with internal fast and slow streaks commensurate in both structure and energy with known TWs using numerical simulations in a long pipe. These only occur, however, within less energetic regions of (localized) `puff' turbulence at low Reynolds numbers (Re=2000-2400), and not at all in (homogeneous) `slug' turbulence at Re=2800. This strongly suggests that all currently known TWs sit in an intermediate region of phase space between the laminar and turbulent states rather than being embedded within the turbulent attractor itself. New coherent fast streak states with strongly decelerated cores appear to populate the turbulent attractor instead.Comment: As accepted for PRL. 4 pages, 6 figures. Alterations to figs. 4,5. Significant changes to tex

A subsonic probe for the measurement of d-region charged particle densities

Subsonic probe for measurement of charged particle densities in D layer of ionospher

The American species of the annulatipes group of the subgenus Lepidohelea, genus Forcipomyia (Diptera: Ceratopogonidae)

The annulatipes group of the genus Forcipomyia Meigen, subgenus Lepidohelea Kieffer, is represented in the Western Hemisphere by 12 species. Keys are presented for their identification, and to distinguish them from other groups of the subgenus Lepidohelea. The three previously known species, annulatipes Macfie, brasiliensis Macfie, and kuanoskeles Macfie, from southern Brazil, as well as the following nine new species, are described and illustrated: bahiensis, basifemoralis, bifida, convexipenis, euthystyla, gravesi, herediae, hobbsi, and weemsi