103 research outputs found
Random walks on finite lattice tubes
Exact results are obtained for random walks on finite lattice tubes with a
single source and absorbing lattice sites at the ends. Explicit formulae are
derived for the absorption probabilities at the ends and for the expectations
that a random walk will visit a particular lattice site before being absorbed.
Results are obtained for lattice tubes of arbitrary size and each of the
regular lattice types; square, triangular and honeycomb. The results include an
adjustable parameter to model the effects of strain, such as surface curvature,
on the surface diffusion. Results for the triangular lattice tubes and the
honeycomb lattice tubes model diffusion of adatoms on single walled zig-zag
carbon nano-tubes with open ends.Comment: 22 pages, 4 figure
Three-dimensional recording by tightly focused femtosecond pulses in LiNbOā
The authors report on a three-dimensional single-shot optical recording by 150fs pulses at 800nm wavelength in Fe doped LiNbOā. The rewritable bits (2āĆ2yĆ8zĪ¼mĀ³) are demonstrated. The highest refractive index modulation of ā¼10ā»Ā³ per single pulse has been formed by preferential photovoltaiceffect at close to the dielectric breakdownirradiance of ā¼TW/cmĀ² and was independent of polarization (in respect to the c axis). The achievable refractive index modulation is evaluated and the recording mechanisms are discussed.One of the authors M.S. thanks the Matsumae
International Foundation for the research fellowship. Another
author E.G.G. acknowledges support of the Australian Research
Council through its Center of Excellence
The role of the catalytic particle temperature gradient for SWNT growth from small particles
The Vapour-Liquid-Solid (VLS) model, which often includes a temperature
gradient (TG) across the catalytic metal particle, is often used to describe
the nucleation and growth of carbon nanostructures. Although the TG may be
important for the growth of carbon species from large metal particles,
molecular dynamics simulations show that it is not required for single-walled
carbon nanotube growth from small catalytic particles
Electronic states and quantum transport in double-wall carbon nanotubes
Electronic states and transport properties of double-wall carbon nanotubes
without impurities are studied in a systematic manner. It is revealed that
scattering in the bulk is negligible and the number of channels determines the
average conductance. In the case of general incommensurate tubes, separation of
degenerated energy levels due to intertube transfer is suppressed in the energy
region higher than the Fermi energy but not in the energy region lower than
that. Accordingly, in the former case, there are few effects of intertube
transfer on the conductance, while in the latter case, separation of
degenerated energy levels leads to large reduction of the conductance. It is
also found that in some cases antiresonance with edge states in inner tubes
causes an anomalous conductance quantization, , near the Fermi
energy.Comment: 24 pages, 13 figures, to be published in Physical Review
Coupled laser molecular trapping, cluster assembly, and deposition fed by laser-induced Marangoni convection
A coupled mechanism for molecular aggregation in a thin water solution film by laser-tweezers is suggested based on (i) simulation of light intensity distribution and (ii) order of magnitude analysis of heat and mass transport induced by Marangoni convection. The analysis suggests that the laser induced temperature distribution develops within 1 ms and Marangoni convection flow commences within 0.01-1 s, which increases by 1-2 orders of magnitude the mass transfer of dissolved molecules into the laser focus where they are trapped and aggregate by attractive van der Waals forces. This mechanism, considered for the particular case of polymer assembly, suggests that it can also be successfully applied for assembling other types of clusters and molecular aggregates from solutions
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