The nature of mobile hydrogen in a-Si:H—Electrochemical studies

Electrochemical studies of both the a-Si:H based metal/oxide/semiconductor structures and a-Si:H modified Pt electrode as a part of two-electrode cell compartment with electrolyte were performed to obtain information on the nature of mobile hydrogen in a-Si:H. We assume, that the complex formed by a hydrogen molecule and a silicon dangling bond (the origin of D_h states) provides for mobile hydrogen. Information on the process of electron selfexchange (hopping) in a-Si:H driven by diffusion in the presence of a concentration gradient of redox centers is obtained. The capability of the electrochemical methods for studying the role of hydrogen in degradation of a-Si:H caused by bias annealing and/or illumination is demonstrated. Also, it was shown that because of the unique electrocatalytic features of the a-Si:H modified Pt electrode, the latter can act as a “programmable” and selective sensor of heavy metal ions and/or metal complexes.     

Changes in Metallothionein Level in Rat Hepatic Tissue after Administration of Natural Mouldy Wheat

Mycotoxins are secondary metabolites produced by microfungi that are capable of causing disease and death in humans and other animals. This work was aimed at investigation of influence of mouldy wheat contaminated by pathogenic fungi producing mycotoxins on metallothionein levels in hepatic tissue of rats. The rats were administrating feed mixtures with different contents of vitamins or naturally mouldy wheat for 28 days. It was found that the wheat contained deoxynivalenol (80 ± 5 μg per kg of mouldy wheat), zearalenone (56 ± 3 μg/kg), T2-toxin (20 ± 2 μg/kg) and aflatoxins as a sum of B1, B2, G1 and G2 (3.9 ± 0.2 μg/kg). Rats were fed diets containing 0, 33, 66 and 100% naturally moulded wheat. Control group 0, 33, 66 and 100% contained vitamins according to Nutrient Requirements of Rats (NRC). Other four groups (control group with vitamins, vit33, vit66 and vit100%) were fed on the same levels of mouldy wheat, also vitamins at levels 100% higher than the previous mixtures. We determined weight, feed conversion and performed dissection to observe pathological processes. Changes between control group and experimental groups exposed to influence of mouldy wheat and experimental groups supplemented by higher concentration of vitamins and mouldy wheat were not observed. Livers were sampled and did not demonstrate significant changes in morphology compared to control either. In the following experiments the levels of metallothionein as a marker of oxidative stress was determined. We observed a quite surprising trend in metallothionein levels in animals supplemented with increased concentration of vitamins. Its level enhanced with increasing content of mouldy wheat. It was possible to determine a statistically significant decline (p<0.05) between control group and groups of animals fed with 33, 66 and 100% mouldy wheat. It is likely that some mycotoxins presented in mouldy wheat are able to block the mechanism of metallothionein synthesis.     

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

Structuring of polymer nanocomposites (PNCs) with an aid of relatively weak external magnetic fields has been studied as a method for control of the nano- and microstructure. Magnetic nanoparticles (NPs) were assembled into high aspect ratio one-dimensional strings and unidirectionally oriented with the magnetic field (B = 0–50 mT) within the photopolymer matrix. The effect of the anisotropic MNPs assemblies on the mechanical properties was studied over a wide temperature range for the first time. The impact of various reinforcing mechanisms was distinguished with respect to the position of the glass transition temperature (T_g). The reinforcing effect exhibits temperature dependency with a maximum ~65°C above the glass transition and only negligible effect below the T_g. In addition, significant directional anisotropy of stiffness was observed. Composite micromechanics was applied to interpret the orientation and size-dependent reinforcement of PNCs, and temperature-dependent stiffness of the polymer-MNP structures was quantified. The presence of polymer chains with altered dynamics surrounding the MNPs inside the anisotropic assemblies was proposed to be an essential nanoscale mechanism mediating the stress transfer and contributing to mechanical robustness of the hybrid structures and PNCs. POLYM. ENG. SCI., 60:587–596, 2020. © 2019 Society of Plastics Engineers     

Evolutionary approximation and neural architecture search

Genetic Programming and Evolvable Machines - Automated neural architecture search (NAS) methods are now employed to routinely deliver high-quality neural network architectures for various...     

Staphylococcus aureus and MRSA Growth and Biofilm Formation after Treatment with Antibiotics and SeNPs

Methicillin-resistant Staphylococcus aureus (MRSA) is a dangerous pathogen resistant to β-lactam antibiotics. Due to its resistance, it is difficult to manage the infections caused by this strain. We examined this issue in terms of observation of the growth properties and ability to form biofilms in sensitive S. aureus and MRSA after the application of antibiotics (ATBs)—ampicillin, oxacillin and penicillin—and complexes of selenium nanoparticles (SeNPs) with these ATBs. The results suggest the strong inhibition effect of SeNPs in complexes with conventional ATBs. Using the impedance method, a higher disruption of biofilms was observed after the application of ATB complexes with SeNPs compared to the group exposed to ATBs without SeNPs. The biofilm formation was intensely inhibited (up to 99% ± 7% for S. aureus and up to 94% ± 4% for MRSA) after application of SeNPs in comparison with bacteria without antibacterial compounds whereas ATBs without SeNPs inhibited S. aureus up to 79% ± 5% and MRSA up to 16% ± 2% only. The obtained results provide a basis for the use of SeNPs as a tool for the treatment of bacterial infections, which can be complicated because of increasing resistance of bacteria to conventional ATB drugs.     

Capacity and power fading mechanism identification from a commercial cell evaluation

An 18650 lithium ion cell was evaluated using dynamic stress test (DST) protocol for cycle life study. Reference performance tests were applied every 60 DST cycles to quantify capacity fade and peak power capability (PPC) degradation with cycles to the end of life. A quantitative incremental capacity analysis (ICA) was applied to identify extrinsic and intrinsic contributions to capacity fading, whereas the open circuit voltage (OCV) measurements were utilized to determine the correct state of charge (SOC) in order to accurately correlate the capacity fade with SOC. The analysis also helps us identify that cell polarization resistance change in the cycles is the primary culprit that bifurcates to both extrinsic and intrinsic origins in capacity fade and PPC degradation. This analysis allows us to develop better understanding in predicting battery performance and life in the rechargeable lithium batteries.