Suchergebnisse

"PEGylated PEIs are intensely studied non-viral vectors for gene delivery, having high transfection efficiencies. Using all-atom molecular dynamics simulations, the interaction of hyperbranched polyethylenimine polyethylene glycol (HPEI-PEG) with DNA was investigated for different number of PEG chains per HPEI core, and, to this end, a new CHARMM Force Field for PEG was developed. The obtained force field parameters are validated by the good agreement of structural measures, such as the radius of gyration, with experimental evidence. The reported investigations reveal an upper bound for the PEG fraction in the modelled HPEI-PEG polymers. The addition of PEG reduces cytotoxicity, increases solubility, while still ensuring a high efficiency of forming polyplexes with DNA. Useful correlations between the copolymer structure and polyplex properties are observed, along with insights on the dynamics of the formation of hydrogen bonds between the HPEI core and DNA."

"The current work shows the generation methods of atmospheric pressure plasma in liquids or on liquids. The optical diagnosis proves the nonthermal character of generated plasmas. They were tested for dyes degradation, nanostructures synthesis and for obtaining of plasma activated water. The activated water preserves its new characteristics for at least three weeks and is a promising agent for bacterial inhibition. Keywords: in/on-liquid plasma, dye degradation, nanoparticles synthesis, plasma activated water, bacterial inhibition. "

"Theoretical investigations on the electronic and magnetic properties (magnetic moments, magneto-crystalline anisotropy, exchange-coupling parameters) of the PrFe11-xCoxTi (x = 0 – 3) and Pr0.8Zr0.2Fe11Ti alloys are presented. Our calculations show that Co for Fe doping in PrFe11-xCoxTi maximize the calculated total magnetic moment and magnetocrystalline anisotropy energy (MAE) for x = 1. The calculated exchange-coupling parameters for the first neighbours of each Fe site (8i, 8j and 8f) show an increase by increasing the Co content suggesting higher Curie temperatures for Co doped PrFe11Ti-based alloys. On the other hand, the Zr for Y substitution in Pr1-yZryFe11Ti (y = 0 - 0.2) decreases MAE without a noticeable decrease of the calculated total magnetic moment. Zr doping has opposite effects on the exchange coupling parameters Jij for different spin pairs. As consequence, any significant changes of the Curie temperatures are predicted for Zr doped PrFe11Ti based alloys in the investigated doping range. Keywords: A. ab-initio calculations; B. magneto-crystalline anisotropy; C. magnetization; D. rare earth magnets. "

"The anatomy of the Perpendicular Magnetic Anisotropy (PMA) in magnetic multilayered thin film heterostructures and the possibility to efficiently manipulate it by external electric fields represent major issues for technological applications in magnetic data storage devices. Solving a standard quantum model based on a Stoner-Rashba Hamiltonian, we illustrate that the magnetic properties in ultrathin magnetic films arise from the competing components identified in the magnetic energy: the Rashba correction to the Stoner splitting, a pseudo-dipolar contribution to the anisotropy energy proportional to the electric field at the interface that would favor in-plane magnetization configuration and a uniaxial-like perpendicular anisotropy term. This last term is responsible on the perpendicular magnetization configuration in ultrathin films and depends on the square of the electric field at the surface of the film. Investigating the time evolution of the magnetic system, we described the macrospin magnetization dynamics in terms of a Rashba field induced magnetization precession. Despite its simplicity, the quantum approach underlines the basic issues related to the physical origin and the mechanisms of the perpendicular magnetization in ultrathin magnetic films and illustrates the capability of manipulation by external gating electric field, in experiments similarly to Nuclear Magnetic Resonance. Keywords: perpendicular magnetic anisotropy, electric field control of anisotropy, magnetic tunnel junctions, magnetic multilayer heterostructures. "

"Understanding of underlying physics related to the Perpendicular Magnetic Anisotropy (PMA) in magnetic heterostructures represents a major issue for its exploit in random-access memory (MRAM) devices. Using ab-initio analysis, we reveal some basic aspects related to the anatomy of PMA and its variation with electric field in various X/Fe/MgO(001) multilayer configurations (X=Cr, Au, V, Ag, Pt, Pd,…) compatible with standard experimental architectures of magnetic tunnel junction devices. Our study quantifies and underlines the significant role of the Rashba interfacial field on PMA. We explain and correlate the sign, the magnitude, and the electric field dependence of the PMA, the Rashba coefficient R and the Dzyaloshinskii–Moriya (DMI) asymmetric exchange interaction parameter. Moreover, when varying the Fe thickness in X/Fe/MgO(001) systems, we observe oscillations of PMA with the number of Fe monolayers, explained within the framework of quantum wells of the 1 Bloch symmetry electrons in Fe. Further atomistic micromagnetic simulations including different Fe layer thicknesses and the corresponding PMA predict macroscopic magnetization characteristics in realistic experimental systems. Keywords: perpendicular magnetic anisotropy, electric field control of PMA, magnetic tunnel junctions, magnetic multilayer heterostructures, atomistic magnetic simulations. "

"We show in this work that exposing thin films of conjugated poly[9,9-bis(2-ethylhexyl)-9H-fluorene-2,7-diyl] to light under nitrogen atmosphere led to an increase of their emission up to 2.2 folds. This enhancement was due to the appearance of structural changes in the glassy and β-phase conformations induced upon thin film illumination, as revealed by the Franck-Condon analysis of the photoluminescence spectra. Interestingly, the photoluminescence of thin films remained at the enhanced value for 75 days after stopping the illumination, most probably due to the permanent structural changes induced upon illumination. Keywords: conjugated polymers, illumination, photoluminescence, β-phase conformations. "

"Electrostatic painting is the fastest and most efficient technology through industrial paints due to its impact on the environment, and also for its very easy application on different surfaces. The first and most important stage of the electrostatic painting is to clean the surface to be painted by removing the dirt, lubricants, oils, metal oxides or welding residues. In order to increase the efficiency of carbon steel surface cleaning, the influence of alkali and surfactant concentrations, temperature and stirring was investigated. To produce a uniform surface required for the electrostatic painting, some degreased samples were subjected to pickling operation using aqueous HCl solution. Keywords: carbon-steel, degreasing, pickling, ultrasonication "