On Self Organization: Model for ionization wave propagation with targets of varying electrical properties

This work presents a model for an atmospheric Helium plasma interacting with normal and cancer cells. This interaction is simulated through the expansion and impingement of a gaseous jet onto targets with varying electrical permittivity. Simulation results show that for a plasma jet impinging onto two targets with different permittivity placed axis-symmetrically relative to the stagnation point of impingement, the jet is biased toward the target with lower permittivity when the target acts as a floating potential. This trend is reversed when the back surface of the target is grounded. In the case of a floating target, higher target permittivity yields a higher positive surface potential as the material experiences higher polarization in response to the net flux of electrons from the plasma onto the surface. Because of this higher surface potential, targets with higher permittivity generate a smaller electric field in the discharge column relative to materials with lower permittivity. When the back surface of the target is ground, the trend is reversed, with polarization occurring primarily on the back surface due to the response to the reservoir of positive charges introduced by ground. In the ground case, the material experiences more negative charging the front surface which induces a lower electric potential. As a result, the material with higher permittivity and a grounded back surface attracts plasma organization at the interface because of the higher local electric field. These numerical findings support experimental results presented by other researchers, which demonstrate selectivity of plasma jets towards some cancer cells more than others. The mechanism introduced here may help inform targeted treatment of specific cells, including those reported to be more resistant to plasma jets.

Interannual Influences of the Surface Potential Vorticity Forcing over the Tibetan Plateau on East Asian Summer Rainfall

The influences of interannual surface potential vorticity forcing over the Tibetan Plateau (TP) on East Asian summer rainfall (EASR) and upper-level circulation are explored in this study. The results show that the interannual EASR and associated circulations are closely related to the surface potential vorticity negative uniform leading mode (PVNUM) over the TP. When the PVNUM is in the positive phase, more rainfall occurs in the Yangtze River valley, South Korea, Japan, and part of northern China, less rainfall occurs in southern China, and vice versa. A possible mechanism by which PVNUM affects EASR is proposed. Unstable air induced by the positive phase of PVNUM could stimulate significant upward motion and a lower-level anomalous cyclone over the TP. As a result, a dipole heating mode with anomalous cooling over the southwestern TP and anomalous heating over the southeastern TP is generated. Sensitivity experiment results regarding this dipole heating mode indicate that anomalous cooling over the southwestern TP leads to local and northeastern Asian negative height anomalies, while anomalous heating over the southeastern TP leads to local positive height anomalies. These results greatly resemble the realistic circulation pattern associated with EASR. Further analysis indicates that the anomalous water vapor transport associated with this anomalous circulation pattern is responsible for the anomalous EASR. Consequently, changes in surface potential vorticity forcing over the TP can induce changes in EASR.

Imaging the electrostatic landscape of unstrained self-assemble GaAs quantum dots

Unstrained GaAs quantum dots are promising candidates for quantum information devices due to their optical properties, but their electronic properties have remained relatively unexplored until now. In this work, we systematically investigate the electronic structure and natural charging of GaAs quantum dots at room temperature using Kelvin probe force microscopy (KPFM). We observe a clear electrical signal from structures demonstrating a lower surface potential in the middle of the dot. We ascribe this to charge accumulation and confinement inside these structures. Our systematical investigation reveals that the change in surface potential is larger for a nominal dot filling of 2 nm and then starts to decrease for thicker GaAs layers. Using k . p calculation, we show that the confinement comes from the band banding due to the surface Fermi level pinning. Our results indicate that these self-assembled structures could be used to study physical phenomena connected to charged quantum dots like Coulomb blockade or Kondo effect.