Development of High Power Square Wave Electroporators

High power microsecond and submicrosecond electric pulse generation and the devices for pulse generation (electroporators) development and application problem is focused in the dissertation. The electric field technologies, pulse forming circuits and circuit transient process compensation methods are investigated. The introduction presents the investigated problem, objects of research, importance of the dissertation, describes research methodology, scientific novelty and the defended statements. In the first chapter the scientific publications in the area of the high power electric pulses generation and application for biological cell permeabilization are overviewed. The influence of the pulse parameters on the biological effects is analysed. The requirements for the electroporators are identified. In the second chapter the prototypes of the high power square wave 5 μs – 10 ms up to 4 kV, 100 A and 200 ns – 5 μs up to 8 kV, 100 A electroporators are developed. The models for investigation of the transient processes in the circuits and the solutions for compensation are overviewed. The adequacy of the proposed models to the experimental results is analysed. The interdigitated microelectrodes structure for planar electroporation is proposed. The resultant electric field distribution and the cell medium temperature rise due to the Joule heating are investigated. The third chapter is focused on the experimental application of the developed high power microsecond and submicrosecond electroporators prototypes in biological experiments. The experimental results with different cell types are presented and conclusions are formed. Research results on the dissertation subject are published in 5 scientific articles: 3 articles – Thomson Reuters ISI Web of Science database journals with impact factor, 2 – publications referenced and abstracted in other international databases, 4 presentations have been made in international conferences in Lithuania, Netherlands, Germany and Japan

On stability in the maximum norm of difference scheme for nonlinear parabolic equation with nonlocal condition

We construct and analyze the backward Euler method for one nonlinear one-dimensional parabolic equation with nonlocal boundary condition. The main objective of this article is to investigate the stability and convergence of the difference scheme in the maximum norm. For this purpose, we use the M-matrices theory. We describe some new approach for the estimation of the error of solution and construct the majorant for it. Some conclusions and discussion of our approach are presented

On the stability of a weighted finite difference scheme for wave equation with nonlocal boundary conditions

We consider the stability of a weighted finite difference scheme for a linear hyperbolic equation with nonlocal integral boundary condition. By studying the spectrum of the transition matrix of the three-layered difference scheme we obtain a sufficient stability condition in a special matrix norm. *The research was partially supported by the Research Council of Lithuania (grant No. MIP-047/2014)

Invasive and non-invasive electrodes for successful drug and gene delivery in electroporation-based treatments

Electroporation is an effective physical method for irreversible or reversible permeabilization of plasma membranes of biological cells and is typically used for tissue ablation or targeted drug/DNA delivery into living cells. In the context of cancer treatment, full recovery from an electroporation-based procedure is frequently dependent on the spatial distribution/homogeneity of the electric field in the tissue; therefore, the structure of electrodes/applicators plays an important role. This review focuses on the analysis of electrodes and in silico models used for electroporation in cancer treatment and gene therapy. We have reviewed various invasive and non-invasive electrodes; analyzed the spatial electric field distribution using finite element method analysis; evaluated parametric compatibility, and the pros and cons of application; and summarized options for improvement. Additionally, this review highlights the importance of tissue bioimpedance for accurate treatment planning using numerical modeling and the effects of pulse frequency on tissue conductivity and relative permittivity values

Computer Adaptive Testing Using Upper-Confidence Bound Algorithm for Formative Assessment

There is strong support for formative assessment inclusion in learning processes, with the main emphasis on corrective feedback for students. However, traditional testing and Computer Adaptive Testing can be problematic to implement in the classroom. Paper based tests are logistically inconvenient and are hard to personalize, and thus must be longer to accurately assess every student in the classroom. Computer Adaptive Testing can mitigate these problems by making use of Multi-Dimensional Item Response Theory at cost of introducing several new problems, most problematic of which are the greater test creation complexity, because of the necessity of question pool calibration, and the debatable premise that different questions measure one common latent trait. In this paper a new approach of modelling formative assessment as a Multi-Armed bandit problem is proposed and solved using Upper-Confidence Bound algorithm. The method in combination with e-learning paradigm has the potential to mitigate such problems as question item calibration and lengthy tests, while providing accurate formative assessment feedback for students. A number of simulation and empirical data experiments (with 104 students) are carried out to explore and measure the potential of this application with positive results.This article belongs to the Special Issue Smart Learnin

The analysis of defects propagation in navigating electronic devices

Defects in the form of microcracks in ??8?12 contacts of passive electronic components of navigating devices operating at different temperatures and pressure were analyzed. Research results have demonstrated the possibility of early prevention of potential accidents. Microscopic studies are systematized depending on various physical and chemical influences on devices. The mathematical model for defects definition in local points of contacts with an error of about 5 – 7.5 % has been applie

Failure analysis of destructive coils

The failure of the destructive pulsed power coils has been investigated. The destructive coil is the key element of the laboratory system which generates half-period abrupt magnetic field pulses with the amplitudes up to 45 T. The transient coupled non-linear magneto-mechanical model has been applied for finite element simulations. The mechanical behavior and operation threshold of the coil have been examined. It has been found that operation threshold of the coil with relatively thin cylindrical reinforcement could be characterized by the opening of the plastic hinge and estimated numerically. Good agreement with experimental results has been observe

Parabolinio tipo lygčių su nelokaliomis kraštinėmis sąlygomis sprendinių kokybinė analizė

The aim of the work is qualitative analysis of solutions of parabolic equations, non–negativity of solutions, investigation and modelling of physical parameters. All tasks were modelled using numerical analysis methods. Differential equations were solved using implicit finite difference method. Derived results could be used solving one–dimensional tasks with parabolic type equations in physics, biochemistry, chemistry and other sciences.Šio straipsnio tikslas – parabolinio tipo lygčių su nelokalia kraštine sąlyga skirtuminio uždavinio sprendinių neneigiamumo ir fizinių parametrų tyrimas. Buvo išnagrinėtos difuzijos ir difuzijos–konvekcijos lygtys. Siekiant optimizuoti tam tikrus fizinius parametrus, buvo parinkti labiausiai tinkami svoriai. Apskaičiuota srovė, maksimalus srovės gradientas, jautrumas ir reakcijos laikas. Nagrinėtų svorių aibėje kiekvienam parametrui rastas optimizuojantis svoris