The design and development of a compact square-wave pulse generator for the electroporation of biological cells is presented. This electroporator can generate square-wave pulses with durations from 3 μs up to 10 ms, voltage amplitudes up to 3500 V, and currents up to 250 A. The quantity of the accumulated energy is optimized by means of a variable capacitor bank. The pulse forming unit design uses a crowbar circuit, which gives better control of the pulse form and its duration, independent of the load impedance. In such cases, the square-wave pulse form ensures better control of electroporation efficiency by choosing parameters determined in advance. The device has an integrated graphic LCD screen and measurement modules for the visualization of the current pulse, allowing for express control of the electroporation quality and does not require an external oscilloscope for current pulse recording. This electroporator was tested on suspensions of Saccharomyces cerevisiae yeast cells, during which, it was demonstrated that the application of such square-wave pulses ensured better control of the electroporation efficiency and cell viability after treatment using the pulsed electric field (PEF).

SARS-CoV-2 vaccines provide strong protection against COVID-19. However, the emergence of SARS-CoV-2 variants has raised concerns about the efficacy of vaccines. In this study, we investigated the interactions of specific polyclonal human antibodies (pAb-SCoV2-S) produced after vaccination with the Vaxzevria vaccine with the spike proteins of three SARS-CoV-2 variants of concern: wild-type, B.1.1.7, and B.1.351. Highly sensitive, label-free, and real-time monitoring of these interactions was accomplished using the total internal reflection ellipsometry method. Thermodynamic parameters such as association and dissociation rate constants, the stable immune complex formation rate constant (k_r), the equilibrium association and dissociation (K_D) constants and steric factors (P_s) were calculated using a two-step irreversible binding mathematical model. The results obtained show that the K_D values for the specific antibody interactions with all three types of spike protein are in the same nanomolar range. The K_D values for B.1.1.7 and B.1.351 suggest that the antibody produced after vaccination can successfully protect the population from the alpha (B.1.1.7) and beta (B.1.351) SARS-CoV-2 mutations. The steric factors (P_s) obtained for all three types of spike proteins showed a 100-fold lower requirement for the formation of an immune complex when compared with nucleocapsid protein.

Previous investigations have shown that an array of novel CMR-B-scalar sensors based on the colossal magnetoresistance effect can be used to measure the magnetic field distribution in the vicinity of the rails of a railgun. However, the data obtained suffered from electromagnetic interference. Therefore, the measurement system was considerably improved to obtain better signal quality. In this paper, the results obtained during the dynamic operation of the ISL railgun RAFIRA are presented. The magnetic field distribution in the vicinity of the rails was measured at different armature velocities. Additional information was obtained using high-speed camera snapshots. The experimental results are compared with simulations performed with the finite element code COMSOL Multiphysics. In particular, the influence of the armature current on the measurements is discussed. It is concluded that the magnetic field distribution in the vicinity of the rails clearly indicates an increased current concentration in the rear part of the armature-rail contact interface. Moreover, the current concentration depends on the speed of the armature. Velocity-dependent skin depths at the surface of aluminum (Dural) rails for projectile velocities ranging between 750 and 1500 m/s are investigated.

The bore of a railgun is a harsh environment with high transient magnetic fields, temperature gradients, and forces. Most common payloads in railgun launch are made from conductive materials. In this article, we consider the effects of the transient magnetic field on a conducting payload during an electromagnetic launch by a serial augmented hexagonal railgun. The magnetic field distribution in the proximity of a solid aluminum payload was investigated by numerical calculations and experimentally by using a CMR-B-scalar sensor array.

The use of brush armatures for accelerating railgun projectiles allows muzzle velocities in excess of 2.5 km/s and contact transition velocities of at least 1.8 km/s in middle-caliber launchers to be obtained. The technology developed at ISL is based on the use of multiple brush armatures. Asymmetric wear has been observed in dynamic launch experiments when the brushes were separated in shot direction. This indicates the presence of asymmetric current distribution. In this paper, mechanisms determining the current distribution of multiple brush armatures are investigated using a static approach. Experiments were performed using a section of the ISL EMA3 railgun with 270-mm-long rails. It had a caliber of 15 mm x 30 mm and was connected to a 150-kJ capacitor bank. Three series of experiments focusing on specific parameter variations are presented. The current distributions were recorded using small Rogowski coils placed around the brushes. Magnetoresistive sensors were used for highly local measurements of magnetic fields in the vicinity of the brushes. Results reveal insight into the contact behavior of multiple brush armatures. More specifically, phase transitions at the brush-rail interfaces can be observed. This is typical in dynamic experiments when the current commutates from one brush to another. The experiments are discussed with the help of PSPICE simulations.

The profound understanding and detailed evaluation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (SCoV2-S) protein and specific antibody interaction mechanism is of high importance in the development of immunosensors for COVID-19. In the present work, we studied a model system of immobilized SCoV2-S protein and specific monoclonal antibodies by molecular dynamics of immune complex formation in real time. We simultaneously applied spectroscopic ellipsometry and quartz crystal microbalance with dissipation to reveal the features and steps of the immune complex formation. We showed direct experimental evidence based on acoustic and optical measurements that the immune complex between covalently immobilized SCoV2-S and specific monoclonal antibodies is formed in two stages. Based on these findings it was demonstrated that applying a two-step binding mathematical model for kinetics analysis leads to a more precise determination of interaction rate constants than that determined by the 1:1 Langmuir binding model. Our investigation showed that the equilibrium dissociation constants (K_D) determined by a two-step binding model and the 1:1 Langmuir model could differ significantly. The reported findings can facilitate a deeper understanding of antigen–antibody immune complex formation steps and can open a new way for the evaluation of antibody affinity towards corresponding antigens.