Low-frequency wave excitation by weak nonlinear interaction of two high-frequency pump waves: part II-experiments
This paper presents an experimental study of the characteristics of the LF wave excited in a hot magnetized plasma column by weak nonlinear interaction of two HF pump waves. These experimental features are systematically compared with theoretical ones which have been established in a previous theoretical paper.
Nonlinear scattering from a warm plasma column
When a plane electromagnetic wave impinges normally on a plasma column, with its magnetic field vector parallel to the axis of the column, a series of (Tonks‐Dattner) resonances are excited which have been described previously in the linear regime, by a warm plasma analysis using a scalar electron pressure and an inhomogeneous radial electron density profile. In this paper, the theory is extended to the weakly nonlinear regime, assuming a parabolic electron density profile. The nonlinear scattered power is obtained. The excitation of dipole resonances at two different frequencies produces a predominantly quadrupolar radiation pattern with minima in the direction of the incident wave vectors and approximately at right angles to it. In general, there is no nonlinear power radiated in the forward and backward directions. Numerical results for the nonlinear scattering coefficients are obtained in the special case of second‐harmonic generation at dipole resonance.
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.