A van der Waals force-based adhesion study of stem cells exposed to cold atmospheric plasma jets.

Cold atmospheric plasma has established its effect on cell adhesion. Given the importance of cell adhesion in stem cells, the current study investigates the effect of plasma treatment on Human Bone Marrow Mesenchymal Stem Cells (HBMMSCs) adhesion by which the differentiation and fate of cells are determined. In this paper, adhesion modification is considered not only for cell- ECM (Extra cellular Matrix), but also between suspended cells, and enhanced adhesions were found in both circumstances. Regarding the previous works, the increase of the cell-ECM adhesion during the plasma therapy was mostly attributed to the enhancement of the production and activity of integrin proteins. Nevertheless, considering the importance of van der Waals forces at the cellular level, the effect of cold plasma on VDWFs and so its effect on adhesion is investigated in this work for the first time, to the best of our knowledge. For this purpose, employing the semi-empirical methods, the role of the plasma therapy on the VDWF between the cells has been studied at three levels; (a) plasma-induced dipole formation, (b) Hammaker coefficient modification of culture medium, and c) cell roughness modification. For suspended cell condition, we conclude and support that van der Waals forces (VDWFs) enhancement has a key role in cell adhesion processes. We believe that, the present work gives a new physical insight in studying the plasma therapy method at the cellular level.

How a relativistic electron beam-ion channel system can act as a polarizer.

The polarization evolution of electromagnetic radiation propagating through an electron beam-ion channel system is studied in the presence of the coupling instability. Employing the system's dielectric tensor and the full four-component Stokes vector description, the obtained differential Mueller matrix is used to determine the polarization state of the initially polarized radiated wave at any arbitrary point in the system. It is shown that an unpolarized EM wave propagating through the electron beam-ion channel system will achieve a linearly polarization state aligned to the perpendicular self-magnetic field vector and propagation direction.

Gain equation for a free-electron laser with a helical wiggler and ion-channel guiding.

The theory of ion-channel guiding in a helical wiggler is presented. Electron motion in the combined ion electrostatic and wiggler magnetostatic fields is analyzed in the absence of the radiation field. The Phi function that determines the rate of change of axial velocity with energy is derived and studied numerically. A detailed analysis of the pendulum equation and the gain equation in the low-gain-per-pass limit are presented. It is shown that the gain for stable group I orbits is positive, while for group II orbits the gain is negative in the negative mass regime and positive in the positive mass regime.