Propagation of cosh Gaussian laser beam in plasma with density ripple in relativistic – ponderomotive regime

Self-focusing of cosh Gaussian laser beam in plasma with periodic density ripple has been investigated. The pondermotive force on electron and the relativistic oscillation of the electron mass causes periodic self-focusing/defocusing of the cosh Gaussian laser beam. The beam converges in the region of high plasma density due to dominance of self-focusing effect over diffraction effect and diverges in the low density region. Non-linear partial differential equation governing the evolution of complex envelope in slowly varying approximation is solved using paraxial ray approximation. The variation of beam-width parameter is studied with distance of propagation for different values of ripple wave number d and decentred parameter b. In order to get strong self-focusing, wavelength and intensity parameters of cosh Gaussian laser beam are optimized.     

Enhanced bacoside production in shoot cultures of Bacopa monnieri under the influence of abiotic elicitors

The effect of different abiotic elicitors [jasmonic acid, copper sulphate (CuSO₄) and salicyclic acid] at varying concentrations on the stimulation of biomass and bacoside production in in vitro Bacopa monnieri shoot culture was studied. A systematic study conducted over a period of 35 days indicated that the maximum bacoside production (6.74 mg g^? 1 dry weight (DW)) was obtained after a lag of 7 days and thereafter, the content decreased gradually to again increase at 28 days (5.91 mg g^? 1 DW). Therefore, elicitation experiments were carried out over a period of 3, 6 and 9 days. The shoot cultures treated with 45 mg L^? 1 of CuSO₄ exhibited the highest bacoside content of 8.73 mg g^? 1 DW (～1.42-fold higher) than in control cultures (6.14 mg g^? 1 DW). This study indicates the effectiveness of abiotic elicitation on bacoside production in in vitro shoot cultures of this medicinally important herb known for its memory-enhancing properties.     

Dependence of peak height of glow curves on heating rate in thermoluminescence

The area under the glow curve (no thermal quenching and same dose) is conserved only in TL-time plots and is not conserved (scales by a factor by which heating rate is increased) in TL-temperature plots. This increase in area under TL-temperature glow curves with increase in heating rate at a constant dose should not be interpreted as increase in sensitivity of the dosimeter and is the consequence of transformation of time to temperature scale (temperature scale obtained from time scale by multiplying with β, T=T₀+βt). This is further supported by the fact that the light output or integrated counts seen by the PMT do not change (ignoring statistical fluctuations) with increase in heating rate at a constant dose. Further for a given heating rate, the glow peak height is similar in time and temperature plots and the glow peak height increases with increase in heating rate. However to conserve area in TL-temperature plots, the TL intensity should be divided by the respective heating rate, which will lead to the decrease of glow peak height in I/β-temperature plots and is the artifact of the normalization process. However for normalized glow curves (I/β-temperature), the glow peak height decreases with increase in heating rate, which is actually true for I/β or TL/β versus temperature plots. Hence it is recommended that in such cases where normalized glow curves (I/β versus temperature) are presented, the obtained peak height must be multiplied by β. By doing so, glow peak height increases with increase in heating rate. In addition to the above, studies are also carried out by considering thermal quenching effect and it is found that a logical way to measure thermal quenching quantitatively is to record the decrease of integrated counts (PMT current) with increase in heating rate at a constant dose, i.e. the integrated peak area (PMT current or TL-time or TL/β-temperature) must be plotted against the heating rate and the same should be used for interpretation of thermal quenching effect. Only this proves the fact whether the decrease of TL intensity (TL/β-temperature) is due to thermal quenching or not.     

Quadruple Gaussian Laser Beam Profile Dynamics in Collisionless Magnetized Plasma

This paper presents an investigation of self-focusing of a quadruple Gaussian laser beam in collisionless magnetized plasma. The nonlinearity due to ponderomotive force which arises on account of nonuniform intensity distribution of the laser beam is considered. The nonlinear partial differential equation governing the evaluation of complex envelope in the slowly varying envelope approximation is solved using a paraxial formalism. The self-focusing mechanism in magnetized plasma, in the presence of self-compression mechanism will be analyzed in contrast to the case in which it is absent. It can be observed that, in case of ponderomotive nonlinearity, the self-compression mechanism obstructs the pulse self-focusing above a certain intensity value. The effect of an external magnetic field is to generate pulses with smaller spot size and shorter compression length. The lateral separation parameter and the initial intensity of the laser beam play a crucial role on focusing and compression parameters. Also, the three-dimensional analysis of pulse propagation is presented by coupling the self-focusing equation with the self-compression one.     

New fourth- and sixth-order classes of iterative methods for solving systems of nonlinear equations and their stability analysis

Numerical Algorithms - In this paper, a two-step class of fourth-order iterative methods for solving systems of nonlinear equations is presented. We further extend the two-step class to establish a...     

Machinability improvement in Inconel-718 by enhanced tribological and thermal environment using textured tool

Journal of Thermal Analysis and Calorimetry - Machinability of Inconel-718 superalloy in conventional approach is poor—this fact necessitates advanced technological adoption such as improved...     

A stable class of improved second-derivative free Chebyshev-Halley type methods with optimal eighth order convergence

In this paper, we present a uniparametric family of modified Chebyshev-Halley type methods with optimal eighth-order of convergence. In terms of computational cost, each member of the family requires only four functional evaluations per step, and hence is optimal in the sense of Kung-Traub conjecture. Moreover, in order to have additional information to choose some elements of the class, in particular some stable enough, we use complex dynamics tools to analyze their stability. Then, some ranges of values of the parameter are found to be avoided but we show that the region of stable members of this family is vast. It is found by way of illustration that these proposed methods are very useful in high precision computations.     

Nonplanar Electron - Acoustic Shock Waves with Superthermal Hot Electrons

Nonplanar electron-acoustic shock waves having superthermal hot electrons are investigated with two temperature electrons model in unmagnetized plasma. Using reductive perturbation method, Korteweg-de Vries-Burgers (KdVB) equation is obtained in the cylindrical/spherical coordinates. Dissipation effect is introduced in the model by means of kinematic viscosity term. On the basis of the solutions of KdVB equation, variation of shock waves features (amplitude, velocity and width) with different plasma parameters are analysed. KdV-Burgers equation always leads to monotonic solitons and no oscillatory peak may appear. The combined effect of particle density (α), superthermal parameter (κ), electron temperature ratio (??) and kinetic viscosity (η₀) is numerically studied, and it is observed that these parameters significantly change the properties of the shock waves in nonplanar geometry especially in spherical coordinates. Results could be helpful to analyse the soliton features in laboratory as well as in the space environments.