13,576 research outputs found
Motion of nanodroplets near edges and wedges
Nanodroplets residing near wedges or edges of solid substrates exhibit a
disjoining pressure induced dynamics. Our nanoscale hydrodynamic calculations
reveal that non-volatile droplets are attracted or repelled from edges or
wedges depending on details of the corresponding laterally varying disjoining
pressure generated, e.g., by a possible surface coating.Comment: 12 pages, 7 figure
Aerodynamic performance of flared fan nozzles used as inlets
Tests were conducted in a low speed wind tunnel to determine the aerodynamic performance of several flared fan nozzles. Each of the flared nozzles was a downstream-facing inlet to a model fan that was used to simulate a variable pitch fan during reverse thrust operation. The total pressure recovery of each of the flared nozzles as well as that of an unflared nozzle and a serrated flare nozzle was obtained for comparison. The aerodynamic performance of a selected flared nozzle was considered in further detail. The nozzle surface pressures for a flared nozzle were also determined. Results indicated that the differences in aerodynamic performance among the nozzles were most apparent at the wind-tunnel-off condition. A nonzero free stream velocity significantly reduced the perforamnce of all the nozzles, and crosswind flow (free stream flow perpendicular to the model axis) further reduced the performance of the nozzles. The unflared nozzle and the serrated flare nozzle had reduced aerodynamic performance compared to a solid surface flared nozzle
Current-mediated synchronization of a pair of beating non-identical flagella
The basic phenomenology of experimentally observed synchronization (i.e., a
stochastic phase locking) of identical, beating flagella of a biflagellate alga
is known to be captured well by a minimal model describing the dynamics of
coupled, limit-cycle, noisy oscillators (known as the noisy Kuramoto model). As
demonstrated experimentally, the amplitudes of the noise terms therein, which
stem from fluctuations of the rotary motors, depend on the flagella length.
Here we address the conceptually important question which kind of synchrony
occurs if the two flagella have different lengths such that the noises acting
on each of them have different amplitudes. On the basis of a minimal model,
too, we show that a different kind of synchrony emerges, and here it is
mediated by a current carrying, steady-state; it manifests itself via
correlated "drifts" of phases. We quantify such a synchronization mechanism in
terms of appropriate order parameters and - for an ensemble of
trajectories and for a single realization of noises of duration ,
respectively. Via numerical simulations we show that both approaches become
identical for long observation times . This reveals an ergodic
behavior and implies that a single-realization order parameter is
suitable for experimental analysis for which ensemble averaging is not always
possible.Comment: 10 pages, 2 figure
Precursor films in wetting phenomena
The spontaneous spreading of non-volatile liquid droplets on solid substrates
poses a classic problem in the context of wetting phenomena. It is well known
that the spreading of a macroscopic droplet is in many cases accompanied by a
thin film of macroscopic lateral extent, the so-called precursor film, which
emanates from the three-phase contact line region and spreads ahead of the
latter with a much higher speed. Such films have been usually associated with
liquid-on-solid systems, but in the last decade similar films have been
reported to occur in solid-on-solid systems. While the situations in which the
thickness of such films is of mesoscopic size are rather well understood, an
intriguing and yet to be fully understood aspect is the spreading of
microscopic, i.e., molecularly thin films. Here we review the available
experimental observations of such films in various liquid-on-solid and
solid-on-solid systems, as well as the corresponding theoretical models and
studies aimed at understanding their formation and spreading dynamics. Recent
developments and perspectives for future research are discussed.Comment: 51 pages, 10 figures; small typos correcte
Hyperfine and Optical Barium Ion Qubits
State preparation, qubit rotation, and high fidelity readout are demonstrated
for two separate \baseven qubit types. First, an optical qubit on the narrow
6S to 5D transition at 1.76 m is implemented. Then,
leveraging the techniques developed there for readout, a ground state hyperfine
qubit using the magnetically insensitive transition at 8 GHz is accomplished
Towards an optical potential for rare-earths through coupled channels
The coupled-channel theory is a natural way of treating nonelastic channels,
in particular those arising from collective excitations, defined by nuclear
deformations. Proper treatment of such excitations is often essential to the
accurate description of reaction experimental data. Previous works have applied
different models to specific nuclei with the purpose of determining
angular-integrated cross sections. In this work, we present an extensive study
of the effects of collective couplings and nuclear deformations on integrated
cross sections as well as on angular distributions in a consistent manner for
neutron-induced reactions on nuclei in the rare-earth region. This specific
subset of the nuclide chart was chosen precisely because of a clear static
deformation pattern. We analyze the convergence of the coupled-channel
calculations regarding the number of states being explicitly coupled. Inspired
by the work done by Dietrich \emph{et al.}, a model for deforming the spherical
Koning-Delaroche optical potential as function of quadrupole and hexadecupole
deformations is also proposed. We demonstrate that the obtained results of
calculations for total, elastic and inelastic cross sections, as well as
elastic and inelastic angular distributions correspond to a remarkably good
agreement with experimental data for scattering energies above around a few
MeV.Comment: 7 pages, 6 figures. Submitted to the proceedings of the XXXVI
Reuni\~ao de Trabalho de F\'{\i}sica Nuclear no Brasil (XXXVI Brazilian
Workshop on Nuclear Physics), held in Maresias, S\~ao Paulo, Brazil in
September 2013, which should be published on AIP Conference Proceeding
Series. arXiv admin note: substantial text overlap with arXiv:1311.1115,
arXiv:1311.042
Renormalization Flow of Axion Electrodynamics
We study the renormalization flow of axion electrodynamics, concentrating on
the non-perturbative running of the axion-photon coupling and the mass of the
axion (like) particle. Due to a non-renormalization property of the
axion-photon vertex, the renormalization flow is controlled by photon and axion
anomalous dimensions. As a consequence, momentum-independent axion
self-interactions are not induced by photon fluctuations. The non-perturbative
flow towards the ultraviolet exhibits a Landau-pole-type behavior, implying
that the system has a scale of maximum UV extension and that the renormalized
axion-photon coupling in the deep infrared is bounded from above. Even though
gauge invariance guarantees that photon fluctuations do not decouple in the
infrared, the renormalized couplings remain finite even in the deep infrared
and even for massless axions. Within our truncation, we also observe the
existence of an exceptional RG trajectory, which is extendable to arbitrarily
high scales, without being governed by a UV fixed point.Comment: 12 pages, 4 figure
Transition from van-der-Waals to H Bonds dominated Interaction in n-Propanol physisorbed on Graphite
Multilayer sorption isotherms of 1-propanol on graphite have been measured by
means of high-resolution ellipsometry within the liquid regime of the adsorbed
film for temperatures ranging from 180 to 260 K. In the first three monolayers
the molecules are oriented parallel to the substrate and the growth is roughly
consistent with the Frenkel-Halsey-Hill-model (FHH) that is obeyed in
van-der-Waals systems on strong substrates. The condensation of the fourth and
higher layers is delayed with respect to the FHH-model. The fourth layer is
actually a bilayer. Furthermore there is indication of a wetting transition.
The results are interpreted in terms of hydrogen-bridge bonding within and
between the layers.Comment: 4 pages, 3 figure
The Adsorption of Atomic Nitrogen on Ru(0001): Geometry and Energetics
The local adsorption geometries of the (2x2)-N and the (sqrt(3)x
sqrt(3))R30^o -N phases on the Ru(0001) surface are determined by analyzing
low-energy electron diffraction (LEED) intensity data. For both phases,
nitrogen occupies the threefold hcp site. The nitrogen sinks deeply into the
top Ru layer resulting in a N-Ru interlayer distance of 1.05 AA and 1.10 AA in
the (2x2) and the (sqrt(3)x sqrt(3))R30^o unit cell, respectively. This result
is attributed to a strong N binding to the Ru surface (Ru--N bond length = 1.93
AA) in both phases as also evidenced by ab-initio calculations which revealed
binding energies of 5.82 eV and 5.59 eV, respectively.Comment: 17 pages, 5 figures. Submitted to Chem. Phys. Lett. (October 10,
1996
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