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[en] The steady state equations of magnetohydrodynamic (MHD) flows for an inviscid fluid of high electrical conductivity are considered for an axisymmetric case, in which the physical quantities are independent of the coordinate φ of a cylindrical coordinate system (r,φ,z). The magnetic field is taken to be aligned to the plasma velocity, i.e., the magnetic lines of force and the streamlines of the velocity field coincide. Two classes of exact solutions are obtained. The obtained solutions are smooth everywhere and satisfy all necessary physical conditions, in which they have applications in astrophysics as well as plasma confinement devices, e.g., tokamak and reversed field pinch.

[en] The equilibrium and stability properties of ideal compressible magnetohydrodynamic (MHD) flows are investigated. The domain is taken to be cylindrical with arbitrary cross-section. Variational principles for plasma equilibria with mass flow are formulated, where we associate the cylindrical MHD equilibrium states to critical points of a conserved Lyapunov functional. This functional consists of the sum of the total energy, the mass, the circulation along field lines (cross-helicity), the momentum and the magnetic helicity. Lyapunov stability conditions for compressible cylindrical ideal MHD flows with arbitrary cross-section are determined

[en] Full text.A brief review is presented for the recent development of the theory of the particle transition matrix elements, basic to the cross section for Helium and inert particle scattering at thermal energies in solid surfaces. the Jackson and Mott matrix elements are presented and discussed for surface scattering processes, habitually classified as elastic and inelastic. Modified transition matrix elements, introduced originally to account for the cut-off effects, are presented in a direct and simple manner. the Debye-Waller factor is introduced and discussed. A recent calculation for the particle transition matrix elements is presented for the specular and inelastic transition matrix elements and the corresponding inelastic scattering cross section is compared in detail to experimental data. the specular and inelastic transition matrix elements are found to be intrinsically similar owing to the intermediate role of a proposed virtual particle squeezed state near the surface

[en] Translational symmetric ideal magnetohydrodynamic plasma with steady incompressible flow is considered. The domain then is of cylindrical shape with arbitrary cross section. Several exact solution classes for nonlinear cases are obtained. The obtained solutions are bounded at infinity, in which they are physically acceptable and have applications in astrophysics as well as solar magnetic fields. Some of the solutions are examined to describe low and high β-plasma equilibria in terms of elementary functions. They can be employed to describe plasma in the solar corona, the photosphere, and the upper corona.

[en] The use¹⁵ N- balance techniques has already identified N-loss as a major problem in lowland rice management. Ammonium sulphate labelled with 5% N-15 atom ex. as a basal fertilized through special column in order to study the effect of flooding and saturation condition on the potential loss of nitrogen fertilizer. Rice straw at a rate of 1% was incorporated with the soil in order to study the role of rice straw (as a source of organic matter) on N-loss. Results show that the application of rice straw under flooding condition resulted in an increase of the biomass. It was observed that flooding circumstances may reduce the loss of nitrogen. Since N-recovery under flood and saturation rhizosphere (with plant) conditions were about 75% and 56%, respectively. The effect of rice root (rhizosphere) on nitrification has been observed. Results of flood and non flood rhizossphere show that the nitrogen recovery were about 75% and 86%, respectively. Results show an indirect evidence that the process of rhizosphere nitrification denitrification resulted in a significant amount of N-loss.It is evident that deep placement and flooded condition proved to be an effective means of reducing the potential of N-loss. 1 fig., 3 tabs

[en] An Ising model is presented for a simple cubic-type structure, to determine the magnetic properties for superlattices of periodic A_k(A_pB_1-p)₁B_h formula consisting of k layers of spin-1/2 A ions, h layers of spin-1/2 B ions and single layer disordered alloy interfaces between them. The interface layers are characterized by random arrangements of A and B ions so that (A_pB_1-p)₁ is a two-dimensional thermodynamically stable alloy. The magnetic properties studied concern notably the phase diagrams and the sublattice magnetizations of these systems. The model is general and can be used for ferro- or anti-ferromagnetic A-B exchange couplings. In this paper the A-A and B-B exchange couplings are considered ferromagnetic with no loss of generality. An effective field theory is employed to calculate the properties of these systems. We apply the method to various Fe_k(Fe_p Tb_1-p)₁Tb_h superlattices. The needed exchange constants for the two-dimensional alloy interface are calculated in the framework of this model, and used to calculate these properties for different concentrations 0≤p≤1, for these superlattices. The architecture and concentration dependence of the magnetic properties is an important feature of this paper, allowing a useful experimental analysis of similar systems. (author)

[en] Applying the function transformation method, an n-dimensional nonlinear Schroedinger (NDNLS) equation is transformed into a sinh-Gordon equation and other equations, which depend only on one function ζ leads to a general soliton solution of the NDNLS equation. It contains some interesting specific solutions such as the N multiple solitons, the propagation al breathers and the quadric solitons. Their properties are simply discussed

[en] Full text.Simulations for the joint probability distribution functions PDF (ξ, θ) have been constructed as a function of their centre of mass from a solid surface boundary, ξ, and of their average orientations, θ, for a macromolecular rod like particles in a dilute solution under hydrodynamic flow. These simulations are constructed for a wide range of the quantity ξ □□ which depicts the ratio of the hydrodynamic shear rate to the rotational Brownian diffusion coefficient. The notion of restitution is introduced to develop an algorithm for the consequences of the Brownian and hydrodynamic collisions of the macromolecules with the impenetrable solid surface boundaries. This restitution applies for a wide range of solid surfaces and macromolecules. In particular, simulation results are presented for these distributions in the neighbourhood of a solid surface boundary, and for a confined space between two such boundaries. The distributions are given for typically low and high hydrodynamic flow conditions and their properties are discussed. In Fig.1 we present the normalized PDF P(θ) for a high value of the shear to rotational diffusion ratio, α=γ/D_rot=100. This ratio characterizes the coupling of the stochastic thermal diffusion of the macromolecular particles in their motion in teh hydrodynamic flow. The exact numerical solution of the Boeder differential equation (BDE), is the continuous curve in Fig. 1, whereas the Brownian simulations are presented in comparison, for the same value of α, and for typically N = 10⁸ events per simulation, as the dots with error bars. Faced with little information in the literature concerning the detailed Brownian 'collision' mechanisms between macromolecules and an impenetrable solid surface, we have introduced the notion opf geometrical restitution per collision event to develop a novel algorithm. Our approach is shown to render intelligible some previous simulation results, where one is often led to making unverifiable assumptions concerning the molecule-surface collisions. In Fig. 2, we present results for the folded P(ξ), summing over θ, for the case of macromolecular rod particles in a static liquid and for high values of α. Our simulation model is seemingly the best available at present to explain the decrease of the macromolecular PDF in the depletion layer with increasing hydrodynamic flux. Using optical experimental techniques we have been able to show for non-Brownian microscopic rod like particles present in flowing dilute solutions, their behaviour when colliding with solid surface boundaries. This is in quantitative agreement with our simulation model

[en] Magnetohydrodynamic equilibria for a plasma in a gravitational field are investigated analytically. For equilibria with one ignorable spatial coordinate, the equations reduce to a single nonlinear elliptic equation for the magnetic potential A, known as the Grad-Shafranov equation. Specifying the arbitrary functions in the latter equation, one obtains three types of nonlinear elliptic equations (a Liouville equation, a sinh Poisson equation, and a generalization of those with a sum of exponentials). Analytical solutions are obtained using the tanh method; this is elaborated in the Appendix. The solutions are adequate to describe an isothermal atmosphere in a uniform gravitational field showing parallel filaments of diffuse, magnetized plasma suspended horizontally in equilibrium.