Effect of continuous magnetic field on the growth mechanism of nanoporous anodic alumina films on different substrates

The effects induced by an external homogeneous magnetic field on the oxide film growth on aluminum in aqueous solutions of oxalic and sulfuric acid and on surface morphology of the alumina films were studied. Aluminum films of 100 nm thickness were prepared by thermal evaporation on SiO₂/Si and glass-ceramic substrates. The pore diameter for oxalic acid alumina films on the SiO₂/Si substrate decreased by 0.8 nm, the interpore distance by 5.9 nm, and cell diameter by 6.9 nm if a magnetic field of 0.5 T was applied. When aluminum was anodized in sulfuric acid on the same substrate, the significant changes in parameters of porous structure of alumina, which were similar to the ones in oxalic acid, are firstly observed in stronger magnetic fields (of 0.7 T). On the basis of data obtained in this study and of previous investigation on the negative space charge and thermally activated defects in anodic alumina, we concluded that the intensity of the magnetic field is associated with energy of electron traps and that the changes of cell diameter characterize the trap concentration. The energy of electron traps in oxalic acid alumina films was proved to be smaller than the one in films formed in sulfuric acid, but the concentration of traps was of the same order of magnitude. When the substrate was replaced with the glass-ceramic one, the pore diameter in oxalic acid alumina films increased to ca. 17.6 nm.     

Study of cobalt ferrite nanosuspensions for low-frequency ferromagnetic hyperthermia

High-coercive cobalt ferrite nanoparticles were synthesized and studied for magnetic hyperthermia by direct injection of their suspension into a tumor and application of a strong audio-frequency magnetic field for heating. Physical （dynamic magnetic hysteresis and heat generation in both liquid and solid dispersions）, biological （toxicity and penetration of particles in therapeutic quantities into mouse tumor tissue） as well as other properties of the particles were studied. A model was developed to describe the magnetodynamics in suspensions of magnetic nanoclusters with an account for both Brownian and regular rotations, to provide understanding of observed phenomena. The experimental and theoretical techniques developed have formed a basis for controllable synthesis of the magnetic nanoparticles for low-frequency heat generation in medical and other applications.     

An inverse problem for a hyperbolic system on a vector bundle and energy measurements

A uniqueness result in the inverse problem for an inhomogeneous hyperbolic system on a real vector bundle over a smooth compact manifold, based on energy measurements for improperly known sources, is established.     

Overdetermined Elliptic Systems

We consider linear overdetermined systems of partial differential equations. We show that the introduction of weights classically used for the definition of ellipticity is not necessary, as any system that is elliptic with respect to some weights becomes elliptic without weights during its completion to involution. Furthermore, it turns out that there are systems which are not elliptic for any choice of weights but whose involutive form is nevertheless elliptic. We also show that reducing the given system to lower order or to an equivalent system with only one unknown function preserves ellipticity.