The Experts below are selected from a list of 4281 Experts worldwide ranked by ideXlab platform
Gregor Eugen Morfill - One of the best experts on this subject based on the ideXlab platform.
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Dust-acoustic waves in collisional dusty plasmas of planetary Rings
Astronomy and Astrophysics, 2006Co-Authors: V. V. Yaroshenko, Frank Verheest, Gregor Eugen MorfillAbstract:Aims. The effects of ion and neutral drag forces on stability of low-frequency wave modes is investigated from the point of view of parameters relevant to the plasma environment in the vicinity of the main Saturn Rings. The electrons and ions are considered to be magnetized and corotate with the planet, while the dust grains are not magnetized and move around the planet on Keplerian orbits. Methods. The wave modes of low-frequencies in such dusty plasma, propagating along the ring in the azimuthal direction are analyzed based on the susceptibilities derived from the standard fluid approach and model presentation of the drag forces valid in the parameter regime of the dusty plasma of planetary Rings. Results. It is found that the ion drag force can crucially change the stability of dust-acoustic perturbations. Inside the co-rotation distance the ion drag force can be responsible for the excitation of dust-acoustic waves, while for the region outside the synchronous orbit this mode can hardy be excited (at radial distances corresponding to the main Rings). The instability due to the ion drag force could be also of some importance for perturbations in remote Rings, where the relative ion-dust velocities exceed their thermal speed.
V. V. Yaroshenko - One of the best experts on this subject based on the ideXlab platform.
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Dust-acoustic waves in collisional dusty plasmas of planetary Rings
Astronomy and Astrophysics, 2006Co-Authors: V. V. Yaroshenko, Frank Verheest, Gregor Eugen MorfillAbstract:Aims. The effects of ion and neutral drag forces on stability of low-frequency wave modes is investigated from the point of view of parameters relevant to the plasma environment in the vicinity of the main Saturn Rings. The electrons and ions are considered to be magnetized and corotate with the planet, while the dust grains are not magnetized and move around the planet on Keplerian orbits. Methods. The wave modes of low-frequencies in such dusty plasma, propagating along the ring in the azimuthal direction are analyzed based on the susceptibilities derived from the standard fluid approach and model presentation of the drag forces valid in the parameter regime of the dusty plasma of planetary Rings. Results. It is found that the ion drag force can crucially change the stability of dust-acoustic perturbations. Inside the co-rotation distance the ion drag force can be responsible for the excitation of dust-acoustic waves, while for the region outside the synchronous orbit this mode can hardy be excited (at radial distances corresponding to the main Rings). The instability due to the ion drag force could be also of some importance for perturbations in remote Rings, where the relative ion-dust velocities exceed their thermal speed.
Benjamin B Yellen - One of the best experts on this subject based on the ideXlab platform.
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magnetic assembly of colloidal superstructures with multipole symmetry
Nature, 2009Co-Authors: Randall M Erb, Hui S Son, Bappaditya Samanta, Vincent M Rotello, Benjamin B YellenAbstract:The assembly of complex structures out of simple colloidal building blocks is of practical interest for building materials with unique optical properties (for example photonic crystals and DNA biosensors) and is of fundamental importance in improving our understanding of self-assembly processes occurring on molecular to macroscopic length scales. Here we demonstrate a self-assembly principle that is capable of organizing a diverse set of colloidal particles into highly reproducible, rotationally symmetric arrangements. The structures are assembled using the magnetostatic interaction between effectively diamagnetic and paramagnetic particles within a magnetized ferrofluid. The resulting multipolar geometries resemble electrostatic charge configurations such as axial quadrupoles ('Saturn Rings'), axial octupoles ('flowers'), linear quadrupoles (poles) and mixed multipole arrangements ('two tone'), which represent just a few examples of the type of structure that can be built using this technique.
Juan J De Pablo - One of the best experts on this subject based on the ideXlab platform.
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homeotropic nano particle assembly on degenerate planar nematic interfaces films and droplets
Soft Matter, 2015Co-Authors: Alejandro Londonohurtado, Julio C Armasperez, Juan P Hernandezortiz, Juan J De PabloAbstract:A continuum theory is used to study the effects of homeotropic nano-particles on degenerate planar liquid crystal interfaces. Particle self-assembly mechanisms are obtained from careful examination of particle configurations on a planar film and on a spherical droplet. The free energy functional that describes the system is minimized according to Ginzburg–Landau and stochastic relaxations. The interplay between elastic and surface distortions and the desire to minimize defect volumes (boojums and half-Saturn Rings) is shown to be responsible for the formation of intriguing ordered structures. As a general trend, the particles prefer to localize at defects to minimize the overall free energy. However, multiple metastable configurations corresponding to local minima can be easily observed due to the high energy barriers that separate distinct particle arrangements. We also show that by controlling anchoring strength and temperature one can direct liquid-crystal mediated nanoparticle self-assembly along well defined pathways.
Juan P Hernandezortiz - One of the best experts on this subject based on the ideXlab platform.
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homeotropic nano particle assembly on degenerate planar nematic interfaces films and droplets
Soft Matter, 2015Co-Authors: Alejandro Londonohurtado, Julio C Armasperez, Juan P Hernandezortiz, Juan J De PabloAbstract:A continuum theory is used to study the effects of homeotropic nano-particles on degenerate planar liquid crystal interfaces. Particle self-assembly mechanisms are obtained from careful examination of particle configurations on a planar film and on a spherical droplet. The free energy functional that describes the system is minimized according to Ginzburg–Landau and stochastic relaxations. The interplay between elastic and surface distortions and the desire to minimize defect volumes (boojums and half-Saturn Rings) is shown to be responsible for the formation of intriguing ordered structures. As a general trend, the particles prefer to localize at defects to minimize the overall free energy. However, multiple metastable configurations corresponding to local minima can be easily observed due to the high energy barriers that separate distinct particle arrangements. We also show that by controlling anchoring strength and temperature one can direct liquid-crystal mediated nanoparticle self-assembly along well defined pathways.
