Narrow Results

The purpose of this work is to present an analytical description of dynamics of small ferromagnetic particles with uniaxial anisotropy and the slowly varying magnetic field applied at an arbitrary angle to the anisotropy axis. Considerable attention is given to the nonlinear aspects of adiabatic dynamics. Theoretical analysis based on the consideration of the Landau–Lifshitz–Gilbert equation employs an asymptotic expansion similar to the famous semi-classical WKBJ solution of quantum mechanics equations. The small parameter of the expansion is the ratio of characteristic frequency of the applied magnetic field to the precession frequency. The nonlinear equation describing the slow dynamics of small ferromagnetic particles is derived. The applicability conditions of the developed theory are presented. The nonlinear corrections to the precessional frequency are derived. It is shown that in numerical simulation using the Landau–Lifshitz–Gilbert equation it is not possible to neglect precessional terms at long simulation times due to the nonlinear dynamic correction to a position of the orbit center.

Natural ester is currently used as an insulating oil and coolant for medium-power transformers. The biodegradability of insulating natural ester makes it a preferable insulation liquid to mineral oils. In this work, Fe₃O₄ nanoparticles were used along with oleic acid to improve the performance of insulating natural ester. The micro-morphology of Fe₃O₄ nanoparticles before and after surface modification was observed through transmission electron microscopy. Attenuated total reflection-Fourier transform infrared spectroscopy, thermal gravimetric analysis, and differential thermal analysis were employed to investigate functional groups and their thermal stability on the surface-modified Fe₃O₄ nanoparticles. Basic dielectric properties of natural ester-based insulating nanofluid were measured. The electrodynamic process in the natural ester-based insulating nanofluid is also presented.

Insulating vegetable oils are considered environment-friendly and fire-resistant substitutes for insulating mineral oils. This paper presents the lightning impulse breakdown characteristic of insulating vegetable oil and insulating vegetable oil-based nanofluids. It indicates that Fe₃O₄ nanoparticles can increase the negative lightning impulse breakdown voltages of insulating vegetable oil by 11.8% and positive lightning impulse breakdown voltages by 37.4%. The propagation velocity of streamer is reduced by the presence of nanoparticles. The propagation velocities of streamer to positive and negative lightning impulse breakdown in the insulating vegetable oil-based nanofluids are 21.2% and 14.4% lesser than those in insulating vegetable oils, respectively. The higher electrical breakdown strength and lower streamer velocity is explained by the charging dynamics of nanoparticles in insulating vegetable oil. Space charge build-up and space charge distorted filed in point-sphere gap is also described. The field strength is reduced at the streamer tip due to the low mobility of negative nanoparticles.

Sm–Co nanoparticles have promising applications in both scientific and industrial fields. In this paper, Sm–Co single-crystal nanoparticles were prepared using respective metal salts and complexing agents, such as citric acid by Pechini-type sol–gel method. The mixture solution was heated to form a highly viscous gel, and then heated at different temperatures to achieve SmCo-oxide. And then Sm–Co particles were yielded by reductive annealing of the precursors. Phase analysis, microstructural investigation and magnetic properties were performed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared (FT-IR) and VSM. TGA trace analysis of the gel determined the heat treatment temperature. XRD results showed that SmCoO₃ and Co₃O₄ were obtained at 800${}^{\circ }$C, FT-IR spectrometry analysis also verified the results. In the calcium-thermal reduction process, Sm₂O₃ and Co were obtained after reductive annealing at 800${}^{\circ }$C, meanwhile Sm–Co nanoparticles were formed at 850${}^{\circ }$C. FESEM analysis revealed that the Sm–Co nanoparticles were composed in the form of spherical granules and exhibited well distribution with size in the range of 100 nm. The room temperature saturation magnetization and coercivity of the Sm–Co nanoparticles were 49.61 emu/g and 3.53 kOe, respectively.

This work uses the lattice Boltzmann model (LBM) to solve the Pennes bio-heat equation (BHE) to predict the temperature rise behavior occurring in cylindrical biological tissues during magnetic fluid hyperthermia (MFH). Therefore, LBM is extended to solve the bio-heat transfer problem with curved boundary conditions. Effect of magnetic nanoparticles' (MNPs) volume fraction as well as the vastness of heated region on the temperature distribution are shown. The analytical and numerical finite difference solutions reveal the accuracy of the model.

The synthesis of composite magnetic nanomaterials has received increasing attention due to their electronic, magnetic, catalytic, and chemical or biological sensing properties. We have prepared cobalt ferrite–zinc sulfide nanocomposites by a chemical route. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and photoluminescence spectrometer (PL). The fluorescent magnetic nanoparticles (FMNPs) had a typical diameter of 30±5 nm and saturation magnetization of 5.8 emu g^-1 at room temperature. So, these FMNPs may be potentially applied in different fields such as optoelectronic devices, biolabeling, imaging, drug targeting, bioseparation, magnetic fluid hyperthermia, etc.

Fe₃O₄/Au composite nanoparticles were modified with α-thio-ω-carboxy poly (ethylene glycol). Results from XRD, selected area diffraction, high-resolution TEM images, and dynamic lighting scattering illustrate that the particles have a core/shell composite structure and were monodispersed. Surface plasmon resonance measured by UV–Vis indicates that the absorption peak of the modified composite particle characteristic at 532 nm can be stably suspended in a different buffer. The modified composite particles also have good response to external magnetic field. The Fe₃O₄/Au composite nanoparticles are magnetically and optically active, and are useful for simultaneous magnetic and optical detection. Coupled with biomolecules, the advantages of these composite particles make them very promising for biomedical applications in the near future.

The activation of magnetic nanoparticles (mNPs) by an alternating magnetic field (AMF) is currently being explored as technique for targeted therapeutic heating of tumors. Various types of superparamagnetic and ferromagnetic particles, with different coatings and targeting agents, allow for tumor site and type specificity. Magnetic nanoparticle hyperthermia is also being studied as an adjuvant to conventional chemotherapy and radiation therapy. This review provides an introduction to some of the relevant biology and materials science involved in the technical development and current and future use of mNP hyperthermia as clinical cancer therapy.

The ground state of hemispherical permalloy magnetic shell is studied. There exist two magnetic phases: the onion state and the vortex one. The phase diagram is systematically analyzed in a wide range of geometrical parameters. Possible transitions between different phases are analyzed using the combination of analytical calculations and micromagnetic simulations.

Magnetic nanoparticle (MNP) labeling of stem cell has been proved its efficacy for cell trafficking. Most of the labeling technique requires mixture of iron oxide nanoparticles and transfection agent. Stem cells with ionic MNP without the aid of transfection agent were labeled previously. The possibility of high efficiency labeling of cultured cancer cell, HeLa cell, by using ionic MNP is proposed. The labeled cell morphology was observed and the intracellular iron content was determined by spectrophotometry. The cell character change was evaluated by flow cytometry where front scattering count and side scattering count (SSC) were recorded. The imaging ability of the labeling method was determined by T2 weighted magnetic resonance (MR) imaging. Labeled MNPs were accumulated at cytoplasm is observed and the iron content of labeled cell could reach 27 pg/cell. There is no cell diameter change but the cell granularity increased according to SSC data from flow cytometry. Under clinical 1.5T MR imaging, we could detect labeled cells easily were detected at the cell number of 1 × 10⁵. It is concluded that labeling of cancer cell with ionic MNPs without transfection agent is an efficient labeling method which will provide non-invasive imaging method for monitoring cancer behavior.

The activation of magnetic nanoparticles (mNPs) by an alternating magnetic field (AMF) is currently being explored as technique for targeted therapeutic heating of tumors. Various types of superparamagnetic and ferromagnetic particles, with different coatings and targeting agents, allow for tumor site and type specificity. Magnetic nanoparticle hyperthermia is also being studied as an adjuvant to conventional chemotherapy and radiation therapy. This review provides an introduction to some of the relevant biology and materials science involved in the technical development and current and future use of mNP hyperthermia as clinical cancer therapy.