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Cylindrical Nanotube (cylindrical + nanotube)

Distribution by Scientific Domains

Polymers and Materials Science	60%
Chemistry	40%

Selected Abstracts

Monte Carlo Simulation of ABA Triblock Copolymer Melts Confined in a Cylindrical Nanotube

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2007
Xingqing Xiao
Abstract Monte Carlo simulations were used to identify the microphase morphologies of ABA triblock copolymer melts confined in a cylindrical nanotube. The influences of the volume fraction of mid-block B (fB), the radius of nanotube (R) and the asymmetry of ABA triblock copolymer chain were discussed in detail. When fB varies, a series of double-continuous, three-layer concentric cylinder barrel, porous net, double helixes and the new multiplex structures were observed under different conditions. In addition, the stacked disk, catenoid-cylinder and multi-layer concentric cylinder barrel structures occur in turns at changing R. The relation between circular lamellae period L and layer number Nlayer of concentric cylinder barrel with the increase of R was investigated to further explain the put-off phenomenon of microphase transition of the multi-layer concentric cylinder barrel structures. As for the increase of the asymmetry of ABA triblock copolymer chain, it was concluded that the short AI segments tend to site at the interface between rich A and B circular lamellae. [source]

Simulation of DNA electrophoresis in systems of large number of solvent particles by coarse-grained hybrid molecular dynamics approach

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2009
Rong Wang
Abstract Simulation of DNA electrophoresis facilitates the design of DNA separation devices. Various methods have been explored for simulating DNA electrophoresis and other processes using implicit and explicit solvent models. Explicit solvent models are highly desired but their applications may be limited by high computing cost in simulating large number of solvent particles. In this work, a coarse-grained hybrid molecular dynamics (CGH-MD) approach was introduced for simulating DNA electrophoresis in explicit solvent of large number of solvent particles. CGH-MD was tested in the simulation of a polymer solution and computation of nonuniform charge distribution in a cylindrical nanotube, which shows good agreement with observations and those of more rigorous computational methods at a significantly lower computing cost than other explicit-solvent methods. CGH-MD was further applied to the simulation of DNA electrophoresis in a polymer solution and in a well-studied nanofluidic device. Simulation results are consistent with observations and reported simulation results, suggesting that CGH-MD is potentially useful for studying electrophoresis of macromolecules and assemblies in nanofluidic, microfluidic, and microstructure array systems that involve extremely large number of solvent particles, nonuniformly distributed electrostatic interactions, bound and sequestered water molecules. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 [source]

Monte Carlo Simulation of ABA Triblock Copolymer Melts Confined in a Cylindrical Nanotube

Double-helix structure in multiwall boron nitride nanotubes

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2005
Ayten Celik-Aktas
A new nanotube structural form is reported that resembles a double helix in multiwall boron nitride nanotubes (MW-BNNT) grown by a carbon-free chemical-vapor-deposition process as documented by evidence obtained by transmission electron diffraction and microscopy. The double-helix structure is found in MW-BNNTs exhibiting the same chirality in its different walls. The MW-BNNTs deviate from the structure of ideal nested coaxial cylindrical tubes. Most significantly, bright- and dark-field electron imaging reveals regular zigzag dark and bright spots on the side walls of the nanotubes. The repeating distance between the bright, or dark, spots is related to the chiral angle of the nanotube. Electron diffraction patterns recorded from individual nanotubes show additional diffraction spots belonging to the ,201, zone axes, which are not allowed in a perfectly cylindrical nanotube. These additional diffraction spots become asymmetrical as smaller sections of the nanotube are probed. A series of diffraction patterns recorded along the tube axis showed that the imperfections giving rise to these spots move in a regular fashion around the circumference of the tube. It is shown that all experimental evidence supports the structure model of two helices; one is polygonal in cross section and highly crystalline and the other is circular and less ordered. It is further suggested that the double-helix structure is a result of stronger wall,wall interactions associated with the ionic bonding in boron nitride. [source]

Monodisperse Bile-Salt Nanotubes in Water: Kinetics of Formation,

ADVANCED MATERIALS, Issue 6 2005
B. Jean
Sodium lithocholate forms stabilized cylindrical nanotubes with thin monomolecular walls (see Figure) through fast and complex morphological evolutions. The kinetics of formation can be followed by small-angle X-ray scattering using a brilliant synchrotron source, and are corroborated by cryo-transmission electron microscopy. Coaxial cylinders, helical ribbons, fibrils, and single-walled tubes are found to coexist in the first few minutes of the supramolecular organization process. [source]