NiFe2O4 and ZnFe2O4 ferrites have been prepared by soft mechanochemical synthesis. The formation of spinel phase and crystal structure of sintered powders were analyzed by X-ray diffraction, Raman spectroscopy, and transmission microscopy. In order to confirm phase formation and cation arrangement, Mössbauer measurements were done. Investigation of the magnetization as a function of magnetic field confirms an expected change of the degree of inversion in the spinel structure with the sintering. The electrical DC/resistivity/conductivity was measured in the temperature range of 298-423 K. Impedance spectroscopy was performed in the wide frequency range (100 Hz-10 MHz) at different temperatures.

Microtubules are cylindrically shaped cytoskeletal biopolymers that are essential for cell motility, cell division and intracellular trafficking. Here, we investigate their polyelectrolyte character that plays a very important role in ionic transport throughout the intra-cellular environment. The model we propose demonstrates an essentially nonlinear behavior of ionic currents which are guided by microtubules. These features are primarily due to the dynamics of tubulin C-terminal tails which are extended out of the surface of the microtubule cylinder. We also demonstrate that the origin of nonlinearity stems from the nonlinear capacitance of each tubulin dimer. This brings about conditions required for the creation and propagation of solitonic ionic waves along the microtubule axis. We conclude that a microtubule plays the role of a biological nonlinear transmission line for ionic currents. These currents might be of particular significance in cell division and possibly also in cognitive processes taking place in nerve cells.

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In recent years, the use of biological molecules has offered exciting alternatives to conventional synthetic methods. Specific methods use various biological templates to direct the deposition and patterning of inorganic materials. Here we have established a new electrical model of microtubules as a biological nanoscale circuit based on polyelectrolyte features of cylindrical biopolymers. Our working hypothesis is that microtubules play an active role in sub-cellular computation and signaling via electronic and protonic conductivity and can thus be made useful in hybrid materials that offer novel electronic characteristics. We verify these hypotheses both computationally and analytically through a quantitative model based on the atomic resolution structures of the key functional proteins

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Powdery nickel ferrite, NiFe2O4 has been obtained by soft mechanochemical synthesis in a planetary ball mill. Ni(OH)2 and Fe(OH)3 are used as initial compounds. This mixture was mechanically activated for 25h, uniaxial pressed and sintered at 1100°C for 2h. The phase composition of the sintered sample was analyzed by X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and Raman spectroscopy. Morphologies were examined by scanning electron microscopy (SEM). The electrical DC/resistivity/conductivity at different temperatures was measured using a Source Meter Keithley 2410. An Impedance/Gain-Phase Analyzer (HP-4194) was used to measure the impedance spectra (100Hz - 10MHz) at different temperatures. [Projekat Ministarstva nauke Republike Srbije, br. III 45003 i br. III 45015