325 research outputs found
Structure formation in electromagnetically driven granular media
We report structure formation in submonolayers of magnetic microparticles
subjected to periodic electrostatic and magnetic excitations. Depending on the
excitation parameters, we observe the formation of a rich variety of
structures: clusters, rings, chains, and networks. The growth dynamics and
shapes of the structures are strongly dependent on the amplitude and frequency
of the external magnetic field. We find that for pure ac magnetic driving at
low densities of particles, the low-frequency magnetic excitation favors
clusters while high frequency excitation favors chains and net-like structures.
An abrupt phase transition from chains to a network phase was observed for a
high density of particles.Comment: 4 pages, 5 figure
Sonochemical Modification of the Superconducting Properties of MgB2
Ultrasonic irradiation of magnesium diboride slurries in decalin produces
material with significant inter-grain fusion. Sonication in the presence of
Fe(CO)5 produces magnetic Fe2O3 nanoparticles embedded in the MgB2 bulk. The
resulting superconductor-ferromagnet composite exhibits considerable
enhancement of the magnetic hysteresis, which implies an increase of vortex
pinning strength due to embedded magnetic nanoparticles
Transport and Assembly of Magnetic Surface Rotors
This minireview focuses on recent advances with surface magnetic rotors, namely field-responsive spherical or anisotropic microparticles that translate close to, or are embedded in a confining surface. The application of external magnetic modulations allows these microscopic wheels to be remotely spun and steered while also tuning their interactions and inducing assembly from a collection of disordered, moving units. With optical microscopy one can observe and characterize the complex collective phenomena that emerge in dissipative colloidal systems driven far from equilibrium by external fields. From a technological point of view, magnetic surface rotors envisage implementation into microfluidic devices, and can be used for drug delivery, mixing as well as a model system for biological active matter
Розвиток ідей А.М. Гродзінського про фітодизайн
The results of many years researches on phytodesign are given in this paper. The modern approaches to phytodesign need as careful sampling of tropical and subtropical plants according to their ornamental character, as considering plant resistance to extreme conditions of cultivation. The data on tropical and subtropical plants reaction on microclimate in interiors of miscellaneous functionality are shown.Викладено результати багаторічних досліджень фітодизайну. Сучасні підходи до фітодизайну вимагають не тільки ретельного відбору тропічних і субтропічних рослин за їх декоративними якостями, а й урахування їх стійкості до екстремальних умов вирощування. Наведено дані щодо реакції тропічних і субтропічних рослин на мікроклімат інтер’єрів різного функціонального призначення
Superconducting Nanocomposites: Enhancement of Bulk Pinning and Improvement of Intergrain Coupling
Heterogeneous sonochemical method was applied for synthesis of novel
superconducting nanocomposites consisting of magnetic (and/or nonmagnetic)
nanoparticles embedded into the bulk of ceramic superconductors. In addition to
in-situ production of the efficient pinning centers, this synthesis method
considerably improves the interbrain coupling. Significant enhancement of the
magnetic irreversibility is reported for Fe2O3 nanoparticles embedded into the
bulk of MgB2 superconductor. Nonmagnetic Mo2O5 nanoparticles also increase
pinning strength, but less than magnetic Fe2O3. Detailed magnetization and
electron microscopy characterization is presented. Theory of bulk magnetic
pinning due to ferromagnetic nanoparticles of finite size embedded into the
superconducting matrix is developed
Magnetic nanoparticles as efficient bulk pinning centers in type-II superconductors
Enhancement of flux pinning by magnetic nanoparticles embedded into the bulk
of type-2 superconductor is studied both theoretically and experimentally.
Magnetic part of the pinning force associated with the interaction between a
spherical magnetic inclusion and an Abrikosov vortex was calculated in the
London approximation. Calculations are supported by the experimental results
obtained on sonochemically modified MgB2 superconductor with embedded magnetic
Fe2O3 nanoparticles and compared to MgB2 with nonmagnetic Mo2O5 pinning centers
of similar concentration and particle size distribution. It is shown that
ferromagnetic nanoparticles result in a considerable enhancement of vortex
pinning in large-kappa type-2 superconductors.Comment: PDF, 14 page
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