Linear and nonlinear properties of Rao-dust-Alfv\'en waves in magnetized plasmas

The linear and nonlinear properties of the Rao-dust-magnetohydrodynamic (R-D-MHD) waves in a dusty magnetoplasma are studied. By employing the inertialess electron equation of motion, inertial ion equation of motion, Amp\`ere's law, Faraday's law, and the continuity equation in a plasma with immobile charged dust grains, the linear and nonlinear propagation of two-dimensional R-D-MHD waves are investigated. In the linear regime, the existence of immobile dust grains produces the Rao cutoff frequency, which is proportional to the dust charge density and the ion gyrofrequency. On the other hand, the dynamics of an amplitude modulated R-D-MHD waves is governed by the cubic nonlinear Schroedinger equation. The latter has been derived by using the reductive perturbation technique and the two-timescale analysis which accounts for the harmonic generation nonlinearity in plasmas. The stability of the modulated wave envelope against non-resonant perturbations is studied. Finally, the possibility of localized envelope excitations is discussed.Comment: 30 pages, 8 figures, to appear in Physics of Plasma

Equilibrium configuration of self-gravitating charged dust clouds: Particle approach

A three dimensional Molecular Dynamics (MD) simulation is carried out to explore the equilibrium configurations of charged dust particles. These equilibrium configuration are of astrophysical significance for the conditions of molecular clouds and the interstellar medium. The interaction among the dust grains is modeled by Yukawa repulsion and gravitational attraction. The spherically symmetric equilibria are constructed which are characterized characterized by three parameters: (i) the number of particles in the cloud, (ii) $\Gamma_g$ (defined in the text) where $\Gamma_g^{-1}$ is the short range cutoff of the interparticle potential, and (iii) the temperature of the grains. The effects of these parameters on dust cloud are investigated using radial density profile. The problem of equilibrium is also formulated in the mean field limit where total dust pressure which is the sum of kinetic pressure and electrostatic pressure, balances the self-gravity. The mean field solutions agree well with the results of MD simulations. Astrophysical significance of the results is briefly discussed.Comment: 10 page

A prelude report on molecular docking of HER2 protein towards comprehending anti-cancer properties of saponins from Solanum tuberosum

Saponins are extensively known for many biological activities e.g. antimicrobial, anti-palatability, anti-cancer and hemolytic. As cancer cells have a more cholesterol-like compound in their membrane structure the saponins bind cholesterol due to their natural affinity to bind cancer cell membrane. This prevents them from entering the body through the intestinal tract, where they have the ability to attach themselves to vital organs and grow. This study reports the effective use of lower dose saponins like immunotoxin so that they can inhibit the proliferation of cancerous pancreatic cells. The investigation of pancreatic cancer metabolic pathway it was found that proteins 3H3B produced by genes HER-2 are involved in the enhancement of this type of cancer. Further docking studies showed that there is an effective interaction between saponins and cancer cells. The glide score of the saponin analogue compound with CID 21573770 (Pubchem) was -6.30 followed by score of -6.05 and -5.29 for 5-Florouracil and gemcitabine respectively. The interaction was observed in the GLU and GLN rich region, saponins made H-bonds with GLU-188, GLN-119, VAL-72 and GLN-71. This study indicates an effective way towards leading newer prospects for developing saponin analogue based cancer-fighting drugs with improved cancer cell inhibition property without killing normal cells

Dust acoustic wave in a strongly magnetized pair-dust plasma

The existence of the dust acoustic wave (DAW) in a strongly magnetized electron-positron (pair)-dust plasma is demonstrated. In the DAW, the restoring force comes from the pressure of inertialess electrons and positrons, and the dust mass provides the inertia. The waves could be of interest in astrophysical settings such as the supernovae and pulsars, as well as in cluster explosions by intense laser beams in laboratory plasmas.Comment: 6 pages, revtex

Modulated dust-acoustic wave packets in a plasma with non-isothermal electrons and ions

Nonlinear self-modulation of the dust acoustic waves is studied, in the presence of non-thermal (non-Maxwellian) ion and electron populations. By employing a multiple scale technique, a nonlinear Schrodinger-type equation (NLSE) is derived for the wave amplitude. The influence of non-thermality, in addition to obliqueness (between the propagation and modulation directions), on the conditions for modulational instability to occur is discussed. Different types of localized solutions (envelope excitations) which may possibly occur are discussed, and the dependence of their characteristics on physical parameters is traced. The ion deviation from a Maxwellian distribution comes out to be more important than the electron analogous deviation alone. Both yield a de-stabilizing effect on (the amplitude of) DAWs propagating in a dusty plasma with negative dust grains. The opposite effect, namely a tendency towards amplitude stabilization, is found for the case of positively charged dust presence in the plasma.Comment: To appear in Journal of Plasma Physics (2004

Nonlinear aspects of quantum plasma physics

Dense quantum plasmas are ubiquitous in planetary interiors and in compact astrophysical objects, in semiconductors and micro-mechanical systems, as well as in the next generation intense laser-solid density plasma interaction experiments and in quantum x-ray free-electron lasers. In contrast to classical plasmas, one encounters extremely high plasma number density and low temperature in quantum plasmas. The latter are composed of electrons, positrons and holes, which are degenerate. Positrons (holes) have the same (slightly different) mass as electrons, but opposite charge. The degenerate charged particles (electrons, positrons, holes) follow the Fermi-Dirac statistics. In quantum plasmas, there are new forces associated with i) quantum statistical electron and positron pressures, ii) electron and positron tunneling through the Bohm potential, and iii) electron and positron angular momentum spin. Inclusion of these quantum forces provides possibility of very high-frequency dispersive electrostatic and electromagnetic waves (e.g. in the hard x-ray and gamma rays regimes) having extremely short wavelengths. In this review paper, we present theoretical backgrounds for some important nonlinear aspects of wave-wave and wave-electron interactions in dense quantum plasmas. Specifically, we shall focus on nonlinear electrostatic electron and ion plasma waves, novel aspects of 3D quantum electron fluid turbulence, as well as nonlinearly coupled intense electromagnetic waves and localized plasma wave structures. Also discussed are the phase space kinetic structures and mechanisms that can generate quasi-stationary magnetic fields in dense quantum plasmas. The influence of the external magnetic field and the electron angular momentum spin on the electromagnetic wave dynamics is discussed.Comment: 42 pages, 20 figures, accepted for publication in Physics-Uspekh

Modulational instability in asymmetric coupled wave functions

The evolution of the amplitude of two nonlinearly interacting waves is considered, via a set of coupled nonlinear Schroedinger-type equations. The dynamical profile is determined by the wave dispersion laws (i.e. the group velocities and the GVD terms) and the nonlinearity and coupling coefficients, on which no assumption is made. A generalized dispersion relation is obtained, relating the frequency and wave-number of a small perturbation around a coupled monochromatic (Stokes') wave solution. Explicitly stability criteria are obtained. The analysis reveals a number of possibilities. Two (individually) stable systems may be destabilized due to coupling. Unstable systems may, when coupled, present an enhanced instability growth rate, for an extended wave number range of values. Distinct unstable wavenumber windows may arise simultaneously.Comment: NEXT Sigma-Phi Statistical Physics Conference (2005, Kolymbari, Greece) Proceedings, submitted; v.2 is a shorter version of the text in v.1 (more detailed and somehow more explanatory, yet abbreviated due to submission regulations); some typos corrected as wel