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

Luis Gustavo Martinez ◽  
Akash Dhruv ◽  
Elias Balaras ◽  
Michael Keidar

Abstract 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.

2015 ◽  
Vol 6 (6) ◽  
pp. 714-724 ◽  
Naoya Tada ◽  
Manabu Nohara

Purpose – Local wall thinning is one of serious problems in aged power generating plants. As the thinning grows inside the pipes, it is difficult to detect and evaluate it from the outer surface of pipe. The purpose of this paper is to evaluate the method of semi-ellipsoidal wall thinning geometry on the back surface of flat plate by direct-current potential difference method (DC-PDM) was proposed as a preliminary research for the pipe wall thinning evaluation. The evaluation was performed for the potential difference numerically obtained by finite element method and the results were discussed. Design/methodology/approach – A number of electric field analyses are necessary to evaluate the geometry of local wall thinning. In this study, defect-current modification method (DCMM), which is very fast analysis method based on the formulated solution for the similar thinning geometry, was used. The DCMM enabled the repeated electric field analyses necessary for the evaluation. Findings – The potential difference on the front surface of plate was higher than the other part because of the electric current disturbance by a wall thinning on the back surface. In addition, the distribution depended on the geometry of the wall thinning. In this study, the shape of the thinning was assumed to be ellipsoid, and the width, depth, and length of the thinning were successfully evaluated based on the potential difference distribution on the front surface. Originality/value – Evaluation of local wall thinning geometry was carried out by repeated analyses using DCMM, and the results were successful. This fact suggests that the evaluation of local wall thinning is possible by DC-PDM. The proposed method is going to be extended to the local wall thinning on the inner surface of pipe by geometrical conversion.

2018 ◽  
Vol 8 (8) ◽  
pp. 1233 ◽  
Zhe Wang ◽  
Ximing Cui ◽  
Hongbao Ma ◽  
Yihua Kang ◽  
Zhiyang Deng

Surface roughness is one of the main factors that affect the ultrasonic testing of micro-cracks. This article theoretically analyzes the relationship between the changes in the energy intensity of crack echo waves and roughness-modified transmission coefficients. A series of simulations are carried out using two-dimensional sinusoidal curves as rough surface. Then, parallel experiments are performed on sample surfaces with different arithmetic average heights (Ra). The signal amplitude ratio factor (SARF) is defined to assess the ultrasonic detection capacity for micro-cracks. Both finite element analysis and experimental results show that signal amplitude decreases with an increase in Ra, resulting in signal-to-noise ratio loss. Amplitude attenuation caused by the rough back surface is less than that caused by the rough front surface. It is difficult to identify the signal of micro-cracks with a depth less than 400 μm when the Ra of the front surface is larger than 15 μm. Cracks with depths of more than 200 μm can be distinguished when the back-surface roughness is less than 24 μm. Furthermore, the amplitude of the micro-crack signal increases slightly with variation in the horizontal parameter (Rsm). This study provides a valuable reference for the precision evaluation of micro-cracks using ultrasonic inspection.

2018 ◽  
Vol 60 (10) ◽  
pp. 104002 ◽  
J M García-Regaña ◽  
T Estrada ◽  
I Calvo ◽  
J L Velasco ◽  
J A Alonso ◽  

2007 ◽  
Vol 1 (1) ◽  
pp. 60-63
Svetlana A Tatarkova ◽  
Satvinder Khaira

We have characterized a broad range of liposome formulations with varying DcChol:DOPE ratio. Subsequent addition of DcChol to liposomes increases its positive surface charge. However, loading the nuclear acids did not neutralize the overall negative surface potential to a similar extent. The liposomes were tested by transfection of DNA in living cancer cells.

2020 ◽  
L. Martinez ◽  
A. Dhruv ◽  
L. Lin ◽  
E. Balaras ◽  
M. Keidar

AbstractThis paper presents a numerical model to investigate the deformation of biological cells by applying external electric fields operating at or near cell resonant frequencies. Cells are represented as pseudo solids with high viscosity suspended in liquid media. The electric field source is an atmospheric plasma jet developed inhouse, for which the emitted energy distribution has been measured.Viscoelastic response is resolved in the entire cell structure by solving a deformation matrix assuming an isotropic material with a prescribed modulus of elasticity. To investigate cell deformation at resonant frequencies, one mode of natural cell oscillation is considered in which the cell membrane is made to radially move about its eigenfrequency. An electromagnetic wave source interacts with the cell and induces oscillation and viscoelastic response. The source carries energy in the form of a distribution function which couples a range of oscillating frequencies with electric field amplitude.Results show that cell response may be increased by the external electric field operating at or near resonance. In the elastic regime, response increases until a steady threshold value, and the structure moves as a damped oscillator. Generally, this response is a function of both frequency and magnitude of the source, with a maximum effect found at resonance. To understand the full effect of the source energy spectrum, the system is solved by considering five frequency-amplitude couplings. Results show that the total solution is a nonlinear combination of the individual solutions. Additionally, sources with different signal phases are simulated to determine the effect of initial conditions on the evolution of the system, and the result suggests that there may be multiple solutions within the same order of magnitude for elastic response and velocity. Cell rupture from electric stress may occur during application given a high energy source.SignificanceCold atmospheric plasma jets (CAPJs) have been widely researched for their potential applications in cancer therapy. Existing research has focused mainly on the ability of CAPJs to deliver a mixture of reactive species which can be absorbed by cancer cells and induce cell death. The objective of our study is to investigate the mechanical effect of CAPJ electromagnetic (EM) waves on interacting cells. By coupling the EM waves associated with plasma frequency and cell viscoelastic response, we have developed a numerical tool to investigate cell damage either by mechanical or thermal loads. This work is motivated by the promise of EM waves to function as a sensitizing agent for cancer cells in preparation for chemotherapy.

2020 ◽  
Vol 53 (12) ◽  
pp. 125201
P Seyfi ◽  
A Khademi ◽  
S Ghasemi ◽  
A Farhadizadeh ◽  
H Ghomi

2019 ◽  
Vol 799 ◽  
pp. 20-25
Harri Lille ◽  
Alexander Ryabchikov ◽  
Jakub Kõo ◽  
Valdek Mikli ◽  
Eron Adoberg ◽  

In this study we determined average residual stresses in hard nitride PVD AlCrN, TiAlN and TiCN coatings through simultaneous measurement of length variation in thin-walled tubular substrates and of the curvature of plate substrates. A device for measurement of the length of the tube was developed. Inside the depositing chamber the tube and the plate were fixed parallel in the relation to the axis of the rotating cathode. One batch of plate samples was produced by deposition on front surface (facing the cathode) and the other batch, by deposition on back surface (with back to the cathode). The cross-sectional microstructure and thickness of the coatings were investigated by means of scanning electron microscopy (SEM). The thicknesses of the coatings deposited on front and back surfaces of the plates and on the tube were significantly different. The values of average compressive residual stresses, determined by both methods, were very high irrespective of coating thickness. It was found that the values of compressive residual stresses in the coating were dependent on the shape of the substrate and on its position in the relation to the axis of the rotating cathode.

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