Multicomponent kinetic simulation of Bernstein-Greene-Kruskal modes associated with ion acoustic and dust-ion acoustic excitations in electron-ion and dusty plasmas

A series of numerical simulations based on a recurrence-free Vlasov kinetic algorithm presented earlier [Abbasi et al., Phys. Rev. E 84, 036702 (2011)] are reported. Electron-ion plasmas and three-component (electron-ion-dust) dusty, or complex, plasmas are considered, via independent simulations. Considering all plasma components modeled through a kinetic approach, the nonlinear behavior of ionic scale acoustic excitations is investigated. The focus is on Bernstein-Greene-Kruskal (BGK) modes generated during the simulations. In particular, we aim at investigating the parametric dependence of the characteristics of BGK structures, namely of their time periodicity (τ trap) and their amplitude, on the electron-to-ion temperature ratio and on the dust concentration. In electron-ion plasma, an exponential relation between τ trap and the amplitude of BGK modes and the electron-to-ion temperature ratio is observed. It is argued that both characteristics, namely, the periodicity τ trap and amplitude, are also related to the size of the phase-space vortex which is associated with BGK mode creation. In dusty plasmas, BGK modes characteristics appear to depend on the dust particle density linearly

‘Reason’ and ‘tickle’ as pragmatic constructs in the discourse of advertising

This paper explores certain pragmatic features of advertising discourse. It focuses on and expands upon a binary distinction between types of advertising discourse which was proposed initially by Bernstein (1974) and which has been touched upon more recently by other commentators such as Cook (1992). This is the distinction between reason advertisements (those which suggest a motive or reason for purchase) and tickle advertisements (those which appeal to humour, emotion and mood). It will be argued that Bernstein's distinction can be accommodated relatively systematically within contemporary frameworks of language and discourse. Drawing on a range of work in pragmatics and in systemic-functional linguistics, this paper takes some tentative steps towards the development of a theoretical model with accounts for this particular communicative-cognitive dimension of advertising discourse.

Salt-bridge dynamics control substrate-induced conformational change in the membrane transporter GlpT.

Active transport of substrates across cytoplasmic membranes is of great physiological, medical and pharmaceutical importance. The glycerol-3-phosphate (G3P) transporter (GlpT) of the E. coli inner membrane is a secondary active antiporter from the ubiquitous major facilitator superfamily that couples the import of G3P to the efflux of inorganic phosphate (Pi) down its concentration gradient. Integrating information from a novel combination of structural, molecular dynamics simulations and biochemical studies, we identify the residues involved directly in binding of substrate to the inward-facing conformation of GlpT, thus defining the structural basis for the substrate-specificity of this transporter. The substrate binding mechanism involves protonation of a histidine residue at the binding site. Furthermore, our data suggest that the formation and breaking of inter- and intradomain salt bridges control the conformational change of the transporter that accompanies substrate translocation across the membrane. The mechanism we propose may be a paradigm for organophosphate:phosphate antiporters.

CROSS-SECTIONS FOR RESONANT TRANSFER AND EXCITATION IN FEQ++H-2 COLLISIONS

Resonant transfer and excitation (RTE) is investigated for Fe(q+) ions (q=23, 24, and 25) colliding with H2. For each charge state, cross sections for RTE were obtained from measurements of K x rays, emitted from the doubly excited intermediate state, coincident with single-electron capture by the incident ion. Additionally, for Fe25+ cross sections were obtained from measurements of coincidences between the two K x rays emitted from the intermediate state. These latter measurements Provide information on the lifetimes of intermediate metastable states formed in the RTE process. In all cases, measured cross sections are in good agreement with calculations based on theoretical cross sections for dielectronic recombination (DR). Since RTE closely approximates DR, the results indicate that dielectronic-recombination cross sections involving K-shell excitation can be accurately predicted for highly charged iron ions. The results for Fe25+ show that metastable states are sufficiently short lived to be observable in the RTE (or DR) process for these hydrogenlike ions.