Sonata Tolvaisiene

Compact Electro-Permeabilization System for Controlled Treatment of Biological Cells and Cell Medium Conductivity Change Measurement

Abstract Subjection of biological cells to high intensity pulsed electric field results in the permeabilization of the cell membrane. Measurement of the electrical conductivity change allows an analysis of the dynamics of the process, determination of the permeabilization thresholds, and ion efflux influence. In this work a compact electro-permeabilization system for controlled treatment of biological cells is presented. The system is capable of delivering 5 μs - 5 ms repetitive square wave electric field pulses with amplitude up to 1 kV. Evaluation of the cell medium conductivity change is implemented in the setup, allowing indirect measurement of the ion concentration changes occurring due to the cell membrane permeabilization. The simulation model using SPICE and the experimental data of the proposed system are presented in this work. Experimental data with biological cells is also overviewed

Nanostructured Manganite Films as Protectors Against Fast Electromagnetic Pulses

The effects of strong electric fields on the resistivity of thin nanostructured La-Ca(Sr)-Mn-O films, deposited on lucalox substrates by the metal-organic chemical vapor deposition technique, are investigated using electrical pulses with a pulselength of 5 ns and an amplitude of up to 500 V. The influence of the chemical composition of these films is analyzed to determine the optimal conditions for their use as protectors against fast electromagnetic pulses (EMPs) when operating at the temperature of liquid nitrogen as well as at room temperatures. It is shown that by changing the doping material (using Ca instead of Sr), it is possible to reduce the threshold voltage in these films and to obtain better limiting characteristics at lower amplitudes of such pulsed electric fields.

Multistep Accelerated Aging of Magnetic Field Sensors Based on Nanostructured La–Sr–Mn–O Thin Films

We present results of investigation of accelerated aging influence on electrical resistivity and magnetoresistance (MR) of nanostructured La–Sr–Mn–O films used for magnetic field sensors, which could be applied in advanced scientific and industrial devices. The 400-nm-thick manganite films were grown by metal organic chemical vapor deposition technique. To investigate the effectiveness of accelerated aging, the three methods were tested: 1) thermal treatment of the sensor samples at 100 °C temperature in Ar atmosphere when film surface was uncoated; 2) thermal treatment of the samples coated prior to treatment by polymer; and 3) multistep aging including both previous methods: thermal treatment of the samples with uncoated surface in Ar atmosphere and additional thermal treatment of the coated samples. The sensor samples were studied without and in pulsed magnetic field up to 20 T. To describe the underlying processes, the kinetics of resistivity change during accelerated aging was analyzed using a stretched exponent relaxation function. It was found that the best long-term stability of resistivity in time demonstrated samples treated by a multistep accelerated aging method. All three aging methods resulted in minor influence (<1%) on MR of the films in magnetic fields up to 20 T.