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A dynamic model of a creeping discharge over a dielectric surface is presented. A discharge area (above a dielectric sheet separating a metal needle from a ground plain electrode) is presented as a system of gas sphere cells covering the dielectric. A discharge tree (conducting cluster) is represented by a nonlinear circuit consisting of capacitances, nonlinear conductances, and controlled sources. The sources simulate the potential caused by the needle electrode and free charge located in the neighboring cells. The coefficients for the controlled sources and cell capacitances are determined from the results of static field calculation. The effects of electron drift, impact ionization, and photoionization are involved into the conductance model. Physical parameters of the latter two processes are deduced from the experimental data available in the literature. The criteria for cell initiation are obtained for different applied voltages such that dynamic characteristics of the model correspond to the experimental ones. The experimental results for the nanosecond discharges are used here considering the streamer phase of discharge development. Further improvement of the conductance model is discussed with respect to plasma heating up to the temperatures enough for the streamer-to-leader transition. In addition to discharge patterns which were created to be similar to experimental Lichtenberg figures, the model allows us to determine such local properties of the discharge as current, voltage drop, loss, field, and charge distribution. [ABSTRACT FROM AUTHOR]

The need for radical change in the economy, or more broadly, in the socioeconomic system, is acknowledged today. The implementation of a large number of major reforms, radical decisions, and capital projects is planned. The complexity of the interrelations between economic and social relations is so great that the speculative evaluation of socioeconomic decisions does not guarantee the logical correctness of the reforms under discussion. Even the most talented humanistic economists, who traditionally draw upon their limited experience and "common sense," are unable to analyze, compare, and evaluate avenues of perestroika. History shows what insufficiently substantiated decisions not reinforced by a reliable forecast of their consequences can cost a country. [ABSTRACT FROM AUTHOR]

In the past decade, stimuli-responsive hydrogels are increasingly studied as biomaterials for tissue engineering and regenerative medicine purposes. Smart hydrogels can not only replicate the physicochemical properties of the extracellular matrix but also mimic dynamic processes that are crucial for the regulation of cell behavior. Dynamic changes can be influenced by the hydrogel itself (isotropic vs anisotropic) or guided by applying localized triggers. The resulting swelling-shrinking, shape-morphing, as well as patterns have been shown to influence cell function in a spatiotemporally controlled manner. Furthermore, the use of stimuli-responsive hydrogels as bioinks in 4D bioprinting is very promising as they allow the biofabrication of complex microstructures. This perspective discusses recent cutting-edge advances as well as current challenges in the field of smart biomaterials for tissue engineering. Additionally, emerging trends and potential future directions are addressed., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The growing number of drug-resistant pathogenic bacteria poses a global threat to human health. For this reason, the search for ways to enhance the antibacterial activity of existing antibiotics is now an urgent medical task. The aim of this study was to develop novel delivery systems for polymyxins to improve their antimicrobial properties against various infections. For this, hybrid core-shell nanoparticles, consisting of silver core and a poly(glutamic acid) shell capable of polymyxin binding, were developed and carefully investigated. Characterization of the hybrid nanoparticles revealed a hydrodynamic diameter of approximately 100 nm and a negative electrokinetic potential. The nanoparticles demonstrated a lack of cytotoxicity, a low uptake by macrophages, and their own antimicrobial activity. Drug loading and loading efficacy were determined for both polymyxin B and E, and the maximal loaded value with an appropriate size of the delivery systems was 450 µg/mg of nanoparticles. Composite materials based on agarose hydrogel were prepared, containing both the loaded hybrid systems and free antibiotics. The features of polymyxin release from the hybrid nanoparticles and the composite materials were studied, and the mechanisms of release were analyzed using different theoretical models. The antibacterial activity against Pseudomonas aeruginosa was evaluated for both the polymyxin hybrid and the composite delivery systems. All tested samples inhibited bacterial growth. The minimal inhibitory concentrations of the polymyxin B hybrid delivery system demonstrated a synergistic effect when compared with either the antibiotic or the silver nanoparticles alone.

Polymyxins are peptide antibiotics that are highly efficient against many multidrug resistant pathogens. However, the poor stability of polymyxins in the bloodstream requires the administration of high drug doses that, in turn, can lead to polymyxin toxicity. Consequently, different delivery systems have been considered for polymyxins to overcome these obstacles. In this work, we report the development of polymyxin delivery systems based on nanoparticles obtained from the self-assembly of amphiphilic random poly(l-glutamic acid- co -d-phenylalanine). These P(Glu- co -dPhe) nanoparticles were characterized in terms of their size, surface charge, stability, cytotoxicity, and uptake by macrophages. The encapsulation efficiency and drug loading into P(Glu- co -dPhe) nanoparticles were determined for both polymyxin B and E. The release kinetics of polymyxins B and E from nanoformulations was studied and compared in buffer solution and human blood plasma. The release mechanisms were analyzed using a number of mathematical models. The minimal inhibitory concentrations of the nanoformulations were established and compared with those determined for the free antibiotics.