Toroids

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G Spiazzi - One of the best experts on this subject based on the ideXlab platform.

  • optimization of shielded pcb air core Toroids for high efficiency dc dc converters
    IEEE Transactions on Power Electronics, 2011
    Co-Authors: S Orlandi, B Allongue, G Blanchot, S Buso, F Faccio, C Fuentes, Maher Kayal, S Michelis, G Spiazzi
    Abstract:

    The paper describes the design of optimized printed circuit board (PCB) air-core Toroids for high-frequency dc-dc converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on dc and ac winding resistance, and on the radiated noise will be investigated. PCB Toroids are compared to standard air-core solenoids and other state-of-the-art air-core Toroids both theoretically and experimentally: at first, using ANSOFT Maxwell and ANSOFT Q3D simulation tools, and subsequently, with laboratory measurements (irradiated noise, efficiency, and frequency response) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high-frequency dc-dc converters where high efficiency, low volume, and low noise are of primary concern.

  • optimization of shielded pcb air core Toroids for high efficiency dc dc converters
    Energy Conversion Congress and Exposition, 2009
    Co-Authors: S Orlandi, B Allongue, G Blanchot, S Buso, F Faccio, C Fuentes, Maher Kayal, S Michelis, G Spiazzi
    Abstract:

    The paper describes the design of optimized PCB air-core Toroids for high frequency DC-DC converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on DC and AC winding resistance, and on the radiated noise will be investigated. PCB Toroids are compared to standard air-core solenoids and other state-of-the-art air-core Toroids both theoretically and experimentally: at first using ANSOFT Maxwell and ANSOFT Q3D simulation tools, subsequently with laboratory measurements (irradiated noise and efficiency) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high frequency DC-DC converters where high efficiency, low volume and low noise are of primary concern.

Nicholas V Hud - One of the best experts on this subject based on the ideXlab platform.

  • evidence that both kinetic and thermodynamic factors govern dna toroid dimensions effects of magnesium ii on dna condensation by hexammine cobalt iii
    Biochemistry, 2004
    Co-Authors: Christine C Conwell, Nicholas V Hud
    Abstract:

    Millimolar concentrations of divalent cations are shown to affect the size of Toroids formed when DNA is condensed by multivalent cations. The origins of this effect were explored by varying the order in which MgCl(2) was added to a series of DNA condensation reactions with hexammine cobalt chloride. The interplay between Mg(II), temperature, and absolute cation concentration on DNA condensation was also investigated. These studies reveal that DNA condensation is extremely sensitive to whether Mg(II) is associated with DNA prior to condensation or Mg(II) is added concurrently with hexammine cobalt(III) at the time of condensation. It was also found that, in the presence of Mg(II), temperature and dilution can have opposite effects on the degree of DNA condensation. A systematic comparison of DNA condensates observed in this study clearly illustrates that, under our low-salt conditions, toroid size is determined by the kinetics of toroid nucleation and growth. However, when Mg(II) is present during condensation, toroid size can also be limited by a thermodynamic parameter (e.g., undercharging). The path dependence of DNA condensation presented here illustrates that regardless of which particular factors limit toroid growth, Toroids formed under the various conditions of this study are largely nonequilibrium structures.

  • controlling the size of nanoscale toroidal dna condensates with static curvature and ionic strength
    Proceedings of the National Academy of Sciences of the United States of America, 2003
    Co-Authors: Christine C Conwell, Igor D Vilfan, Nicholas V Hud
    Abstract:

    The process of DNA condensation into nanometer-scale particles has direct relevance to several fields, including cell biology, virology, and gene delivery for therapeutic purposes. DNA condensation has also attracted the attention of polymer physicists, as the collapse of DNA molecules from solution into well defined particles represents an exquisite example of a polymer phase transition. Here we present a quantitative study of DNA Toroids formed by condensation of 3 kb DNA with hexammine cobalt (III). The presence or absence of static loops within this DNA molecule demonstrates the effect of nucleation loop size on toroid dimensions and that nucleation is principally decoupled from toroid growth. A comparison of DNA condensates formed at low ionic strength with those formed in the presence of additional salts (NaCl or MgCl2) shows that toroid thickness is a salt-dependant phenomenon. Together, these results have allowed the development of models for DNA toroid formation in which the size of the nucleation loop directly influences the diameter of the fully formed toroid, whereas solution conditions govern toroid thickness. The data presented illustrate the potential that exists for controlling DNA toroid dimensions. Furthermore, this study provides a set of data that should prove useful as a test for theoretical models of DNA condensation.

  • cryoelectron microscopy of lambda phage dna condensates in vitreous ice the fine structure of dna Toroids
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: Nicholas V Hud, Kenneth H Downing
    Abstract:

    Abstract DNA Toroids produced by the condensation of λ phage DNA with hexammine cobalt (III) have been investigated by cryoelectron microscopy. Image resolution obtained by this technique has allowed unprecedented views of DNA packing within toroidal condensates. Toroids oriented coplanar with the microscope image plane exhibit circular fringes with a repeat spacing of 2.4 nm. For some Toroids these fringes are observed around almost the entire circumference of the toroid. However, for most Toroids well-defined fringes are limited to less than one-third of the total toroid circumference. Some Toroids oriented perpendicular to the image plane reveal DNA polymers organized in a hexagonal close-packed lattice; however, for other Toroids alternative packing arrangements are observed. To aid interpretation of electron micrographs, three-dimensional model Toroids were generated with perfect hexagonal DNA packing throughout, as well as more physically realistic models that contain crossover points between DNA loops. Simulated transmission electron microscopy images of these model Toroids in different orientations faithfully reproduce most features observed in cryoelectron micrographs of actual Toroids.

  • a constant radius of curvature model for the organization of dna in toroidal condensates
    Proceedings of the National Academy of Sciences of the United States of America, 1995
    Co-Authors: Nicholas V Hud, K H Downing, Rod Balhorn
    Abstract:

    Abstract Toroidal DNA condensates have received considerable attention for their possible relationship to the packaging of DNA in viruses and in general as a model of ordered DNA condensation. A spool-like model has primarily been supported for DNA organization within Toroids. However, our observations suggest that the actual organization may be considerably different. We present an alternate model in which DNA for a given toroid is organized within a series of equally sized contiguous loops that precess about the toroid axis. A related model for the toroid formation process is also presented. This kinetic model predicts a distribution of toroid sizes for DNA condensed from solution that is in good agreement with experimental data.

S Orlandi - One of the best experts on this subject based on the ideXlab platform.

  • optimization of shielded pcb air core Toroids for high efficiency dc dc converters
    IEEE Transactions on Power Electronics, 2011
    Co-Authors: S Orlandi, B Allongue, G Blanchot, S Buso, F Faccio, C Fuentes, Maher Kayal, S Michelis, G Spiazzi
    Abstract:

    The paper describes the design of optimized printed circuit board (PCB) air-core Toroids for high-frequency dc-dc converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on dc and ac winding resistance, and on the radiated noise will be investigated. PCB Toroids are compared to standard air-core solenoids and other state-of-the-art air-core Toroids both theoretically and experimentally: at first, using ANSOFT Maxwell and ANSOFT Q3D simulation tools, and subsequently, with laboratory measurements (irradiated noise, efficiency, and frequency response) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high-frequency dc-dc converters where high efficiency, low volume, and low noise are of primary concern.

  • optimization of shielded pcb air core Toroids for high efficiency dc dc converters
    Energy Conversion Congress and Exposition, 2009
    Co-Authors: S Orlandi, B Allongue, G Blanchot, S Buso, F Faccio, C Fuentes, Maher Kayal, S Michelis, G Spiazzi
    Abstract:

    The paper describes the design of optimized PCB air-core Toroids for high frequency DC-DC converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on DC and AC winding resistance, and on the radiated noise will be investigated. PCB Toroids are compared to standard air-core solenoids and other state-of-the-art air-core Toroids both theoretically and experimentally: at first using ANSOFT Maxwell and ANSOFT Q3D simulation tools, subsequently with laboratory measurements (irradiated noise and efficiency) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high frequency DC-DC converters where high efficiency, low volume and low noise are of primary concern.

M G Boshier - One of the best experts on this subject based on the ideXlab platform.

  • experimental demonstration of painting arbitrary and dynamic potentials for bose einstein condensates
    New Journal of Physics, 2009
    Co-Authors: Kevin Henderson, Changhyun Ryu, C Maccormick, M G Boshier
    Abstract:

    There is a pressing need for robust and straightforward methods to create potentials for trapping Bose?Einstein condensates (BECs) that are simultaneously dynamic, fully arbitrary and sufficiently stable to not heat the ultracold gas. We show here how to accomplish these goals, using a rapidly moving laser beam that 'paints' a time-averaged optical dipole potential in which we create BECs in a variety of geometries, including Toroids, ring lattices and square lattices. Matter wave interference patterns confirm that the trapped gas is a condensate. As a simple illustration of dynamics, we show that the technique can transform a toroidal condensate into a ring lattice and back into a toroid. The technique is general and should work with any sufficiently polarizable low-energy particles.

  • experimental demonstration of painting arbitrary and dynamic potentials for bose einstein condensates
    arXiv: Other Condensed Matter, 2009
    Co-Authors: Kevin Henderson, Changhyun Ryu, C Maccormick, M G Boshier
    Abstract:

    There is a pressing need for robust and straightforward methods to create potentials for trapping Bose-Einstein condensates which are simultaneously dynamic, fully arbitrary, and sufficiently stable to not heat the ultracold gas. We show here how to accomplish these goals, using a rapidly-moving laser beam that "paints" a time-averaged optical dipole potential in which we create BECs in a variety of geometries, including Toroids, ring lattices, and square lattices. Matter wave interference patterns confirm that the trapped gas is a condensate. As a simple illustration of dynamics, we show that the technique can transform a toroidal condensate into a ring lattice and back into a toroid. The technique is general and should work with any sufficiently polarizable low-energy particles.

Myongsoo Lee - One of the best experts on this subject based on the ideXlab platform.

  • switching between stacked Toroids and helical supramolecular polymers in aqueous nanotubules
    Macromolecular Rapid Communications, 2020
    Co-Authors: Huaxin Wang, Myongsoo Lee
    Abstract:

    Although significant advances have been made in supramolecular tubules, reversible polymerization in the tubular walls while maintaining their intact structure remains a great challenge. Here, reversible helical supramolecular polymerization of stacked Toroids is reported, while maintaining tubular structures in aqueous solution. At room temperature, the tubules consist of discrete toroid stackings with hydrophobic interior. Upon heating, the tubules based on toroid stackings undergo a reversible helical supramolecular polymerization to transform into helical tubules by interconnecting between spirally open Toroids. The helical polymerization arises from a tilting transition of the closed Toroids that transform into spirally open Toroids driven by the thermal dehydration of a hydrophilic oligoether dendron surrounding the toroid frameworks.

  • autonomous helical propagation of active Toroids with mechanical action
    Nature Communications, 2019
    Co-Authors: Bowen Shen, Yongju Kim, Youliang Zhu, Xiaobin Zhou, Haonan Sun, Myongsoo Lee
    Abstract:

    Self-assembly in nature is fundamentally dynamic, existing in out-of-equilibrium state in which the systems have the ability to autonomously respond to environmental changes. However, artificial systems exist in a global minimum state, which are incapable of conducting such complex functions. Here we report that input of thermal energy can trigger fixed, artificial Toroids to spontaneously nucleate helical growth. The helical polymerization undergoes reversible and repeatable cycles with subsequent energy input. When the Toroids are located inside lipid vesicles, the polymerization-depolymerization cycle is accompanied by reversible elongation of spherical vesicles. Such liberation from a global minimum state will pave the way to create emergent structures with functions as complex as those of living systems. Self-assembly in nature is dynamic and exists in out-of-equilibrium state and thus systems have the ability to autonomously respond to environmental changes. Here the authors report that input of thermal energy can trigger fixed, artificial Toroids to spontaneously nucleate helical growth.

  • from self assembled Toroids to dynamic nanotubules
    Polymer Chemistry, 2013
    Co-Authors: Yongju Kim, Taehoon Kim, Myongsoo Lee
    Abstract:

    Supramolecular nanostructures based on self-assembly processes have received considerable attention because these structures can lead to dynamic nanomaterials. Among the diverse self-assembled nanostructures, Toroids are interesting nanostructures with the potential for many applications such as channel formation because of their unique symmetrical and annular shape. Notably, a further stacking of the Toroids can produce well-defined one dimensional nanotubules with responsive properties triggered by external stimuli such as temperature, ionic strength, and guest molecules. This review introduces recent research in the area of self-assembled nanostructures from Toroids to dynamic nanotubules.

  • tubular stacking of water soluble Toroids triggered by guest encapsulation
    Journal of the American Chemical Society, 2009
    Co-Authors: Eunji Lee, Jungkeun Kim, Myongsoo Lee
    Abstract:

    Coassembly of laterally grafted rod amphiphiles gives rise to the formation of water-soluble Toroids with a hydrophobic interior. The Toroids stack on top of each other to form a tubular container upon triggering by fullerene encapsulation.