Comparison of the functional properties of selected multilayer systems

Electrodeposition of multilayers continues to grow and diversify. Research is still underway on the adaptation of multilayer systems to new applications in various industries. Cu/Ni multilayers are still very commonly used for practical purposes. In this work, the functional properties of selected multilayer systems with different layers quantity and thicknesses in nanoscale were investigated. The Cu and Ni layers were electrolytically deposited on a low carbon steel substrate and obtained systems were subjected to structural and anticorrosion properties study. The electrochemical parameters were determined by potentiodynamic method and the surface evaluation of the systems after corrosion tests was also carried out

The population biology and evolutionary significance of Ty elements in Saccharomyces cerevisiae

The basic structure and properties of Ty elements are considered with special reference to their role as agents of evolutionary change. Ty elements may generate genetic variation for fitness by their action as mutagens, as well as by providing regions of portable homology for recombination. The mutational spectra generated by Ty 1 transposition events may, due to their target specificity and gene regulatory capabilities, possess a higher frequency of adaptively favorable mutations than spectra resulting from other types of mutational processes. Laboratory strains contain between 25–35 elements, and in both these and industrial strains the insertions appear quite stable. In contrast, a wide variation in Ty number is seen in wild isolates, with a lower average number/genome. Factors which may determine Ty copy number in populations include transposition rates (dependent on Ty copy number and mating type), and stabilization of Ty elements in the genome as well as selection for and against Ty insertions in the genome. Although the average effect of Ty transpositions are deleterious, populations initiated with a single clone containing a single Ty element steadily accumulated Ty elements over 1,000 generations. Direct evidence that Ty transposition events can be selectively favored is provided by experiments in which populations containing large amounts of variability for Ty1 copy number were maintained for ∼100 generations in a homogeneous environment. At their termination, the frequency of clones containing 0 Ty elements had decreased to ∼0.0, and the populations had became dominated by a small number of clones containing >0 Ty elements. No such reduction in variability was observed in populations maintained in a structured environment, though changes in Ty number were observed. The implications of genetic (mating type and ploidy) changes and environmental fluctuations for the long-term persistence of Ty elements within the S. cerevisiae species group are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42799/1/10709_2004_Article_BF00133718.pd

Molecular mechanism of hydrogen peroxide conversion and activation by Cu(II)-amikacin complexes

The interactions between Cu(II)-amikacin complexes [Cu(Il)-Amil and hydrogen peroxide were studied by spectroscopy (EPR, UV-vis, CD, XAS) and cyclic voltammetry. A monomer-dimer equilibrium was detected at complex concentrations above 5 mM (log K-dim = 1.84 +/- 0.03). The dimeric complex undergoes easy, although irreversible oxidation (ca. 0.5-0.6 V) to a Cu(III) species on platinum electrode. However, the monomeric complexes are able to catalyze hydrogen peroxide disproportionation reaction at pH 7.4 in a multistep process, mediated by hydroxyl radicals and involving both Cu(I)/Cu(II) and Cu(II)/Cu(III) redox pairs