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In this paper, we introduce the notion of distributional chaos and the measure of chaos for random dynamical systems generated by two interval maps. We give some sufficient conditions for a zero measure of chaos and examples of chaotic systems. We demonstrate that the chaoticity of the functions that generate a system does not, in general, affect the chaoticity of the system, i.e., a chaotic system can arise from two nonchaotic functions and vice versa. Finally, we show that distributional chaos for random dynamical system is, in some sense, unstable., Comment: 25 pages, 8 figures

In this paper, we study random dynamical systems generated by two Allee maps. Two models are considered - with and without small random perturbations. It is shown that the behavior of the systems is very similar to the behavior of the deterministic system if we use strictly increasing Allee maps. However, in the case of unimodal Allee maps, the behavior can dramatically change irrespective of the initial conditions.

The physicochemical characterization of the magnetoferritin biomacromolecule in terms of morphology, structural and magnetic properties shows that iron oxides can be efficiently loaded into apoferritin molecules, preserving their native biocompatible structure and affecting the morphology of the protein shell.

Magnetic properties of a ferronematic, i.e., nematic liquid crystal doped with magnetic nanoparticles in low volume concentration are studied, with the focus on the ac magnetic susceptibility. A weak dc bias magnetic field (units of Oe) applied to the ferronematic in its isotropic phase increases the ac magnetic susceptibility considerably. Passage of the isotropic-to-nematic phase transition resets this enhancement irreversibly (unless the dc bias field is applied again in the isotropic phase). These experimental findings pave a way to application possibilities, such as low magnetic field sensors, or basic logical elements for information storage., Comment: 7 pages, 6 figures, revised version appeared in Soft Matter

We have studied the magnetotransport of conical and disk-shaped nanocarbon particles in magnetic fields $\left|B\right|\leq9\:\mathrm{T}$ at temperatures $2\leq T\leq300\:\mathrm{K}$ to characterize electron scattering in a three dimensional disordered material of multilayered quasi 2D and 3D carbon nanoparticles. The microstructure of the particles was modified by graphitization at temperatures $1600^{\circ}\mathrm{C}$ and $2700^{\circ}\mathrm{C}$. We find clear correlations between the microstructure as seen in transmission electron microscopy and the magnetotransport properties of the particles. The magnetoresistance measurements showed a metallic nature of samples and positive magnetoconductance which is a signature of weak localization in disordered systems. We find that the magnetoconductance at low temperatures resembles quantum transport in single-layer graphene despite the fact that the samples are macroscopic and three dimensional, consisting of stacked and layered particles, which are randomly oriented in the bulk sample. This graphene-like behaviour is attributed to the very weak interlayer coupling between the graphene layers., Comment: accepted for publication in Journal of Physics D: Applied Physics

Using microemulsion methods, CoO-Pt core-shell nanoparticles (NPs), with diameters of nominally 4 nm, were synthesized and characterized by high-resolution transmission electron microscopy (HRTEM) and a suite of x-ray spectroscopies, including diffraction (XRD), absorption (XAS), absorption near-edge structure (XANES), and extended absorption fine structure (EXAFS), which confirmed the existence of CoO cores and pure Pt surface layers. Using a commercial magnetometer, the ac and dc magnetic properties were investigated over a range of temperature (2 K $\leq$ T $\leq$ 300 K), magnetic field ($\leq$ 50 kOe), and frequency ($\leq$ 1 kHz). The data indicate the presence of two different magnetic regimes whose onsets are identified by two maxima in the magnetic signals, with a narrow maximum centered at 6 K and a large one centered at 37 K. The magnetic responses in these two regimes exhibit different frequency dependences, where the maximum at high temperature follows a Vogel-Fulcher law, indicating a superparamagnetic (SPM) blocking of interacting nanoparticle moments and the maximum at low temperature possesses a power law response characteristic of a collective freezing of the nanoparticle moments in a superspin glass (SSG) state. This co-existence of blocking and freezing behaviors is consistent with the nanoparticles possessing an antiferromagnetically ordered core, with an uncompensated magnetic moment, and a magnetically disordered interlayer between CoO core and Pt shell., Comment: 11 pages, 11 figures

We have investigated the magnetic properties of carbon powders which consist of nanodisks, nanocones, and a small fraction of carbon-black particles. Magnetization measurements were carried out using a superconducting quantum interference device in magnetic fields $-5<\mu_{0}H<5\:\mathrm{T}$ for temperatures in the range $2\leq T<350\:\mathrm{K}$. Measurements of the magnetization $M$ versus temperature $T$ and magnetic field $\mu_{0}H$ for these carbon samples show diamagnetism and paramagetism with an additional ferromagnetic contribution. The ferromagnetic magnetization is in agreement with the calculated magnetization from Fe impurities as determined by the particle-induced x-ray emission method ($<75\:\mu\mathrm{g/g}$). Magnetization measurements in weak magnetic fields show thermal hysteresis, and for strong fields the magnetization $M$ decreases as $M\sim aT^{-\alpha}$ with $\alpha<1$, which is slower than the Curie law ($\alpha=1$), when the temperature increases. The magnetization $M$ versus magnetic field $\mu_{0}H$ shows paramagnetic free-spin $S=\frac{1}{2}$ and $\frac{3}{2}$ behaviors for temperatures $T=2\:\mathrm{K}$ and $15\leq T\leq50\:\mathrm{K}$, respectively. A tendency for localization of electrons was found by electron spin resonance when the temperature $T$ decreases ($2

We have synthesized the intermetallic YPrFe17 compound by arc-melting. X-ray and neutron powder diffraction show that the crystal structure is rhombohedral with View the MathML source space group (Th2Zn17-type). The investigated compound exhibits a broad isothermal magnetic entropy change {\Delta}SM(T) associated with the ferro-to-paramagnetic phase transition (TC \approx 290 K). The |{\Delta}SM| (\approx 2.3 J kg-1 K-1) and the relative cooling power (\approx 100 J kg-1) have been calculated for applied magnetic field changes up to 1.5 T. A single master curve for {\Delta}SM under different values of the magnetic field change can be obtained by a rescaling of the temperature axis. The results are compared and discussed in terms of the magneto-caloric effect in the isostructural R2Fe17 (R = Y, Pr and Nd) binary intermetallic alloys., Comment: Preprint, 5 pages (postprint), 4 figures, regular paper

The radiation stability of biocompatibile magnetic fluid used in nanomedicine after electron irradiation was studied. Two types of the water-based magnetic fluids were prepared. The first one was based on the magnetite nanoparticles stabilized by one surfactant natrium oleate. The second one was biocompatibile magnetic fluid stabilized with two surfactants, natrium oleate as a first surfactant and Poly(ethylene glycol) (PEG) as a second surfactant. The magnetization measurements showed that electron irradiation up to 1000Gy caused 50% reduction of saturation magnetization in the case of the first sample with only one surfactant while in the case of the second biocompatibile magnetic fluid, only 25% reduction of saturation magnetization was observed. In the first magnetic fluid the radiation caused the higher sedimentation of the magnetic particles than in the second case, when magnetic particles are covered also with PEG. The obtained results show that PEG behave as a protective element., Comment: 15 pages, 8 figures