13,605 research outputs found
Particle field holography data reduction by Fourier transform analysis
The size distribution of a particle field hologram is obtained with a Fourier transformation of the Fraunhofer diffraction pattern of the reconstructed hologram. Off-axis absorption holograms of particle fields with known characteristics were obtained and analyzed with a commercially available instrument. The mean particle size of the reconstructed hologram was measured with an error of + or - 5 percent, while the distribution broadening was estimated within + or - 15 percent. Small sections of a pulsed laser hologram of a synthetic fuel spray were analyzed with this method thus yielding a spatially resolved size distribution. The method yields fast and accurate automated analysis of particle field holograms
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Volumetric velocimetry study in a transitional wall jet flow with passive flow control via flaps
Birds are remarkably good flyers and show very special adaptations in their wings for stall delay. The pop-up of some cover feathers during starting and landing gave the idea for the present study to investigate the influence on a wall jet when inserting an array with flaps made of elastomer foil. In a wall jet with Re = 420 a flat plate and two different flap arrays (with a foil thickness of 100 and 200 µm) are measured by a time resolved 3D scanning PIV with 20 laser sheets. 2-dimensional analyses show the forming rolers between the jet flow and the surrounding fluid with a fundamental frequency of 13-14 Hz and the characteristically vortex pairing. By inserting the flap array the jet wallnormal spreading gets intensified and the vortex interaction process results in cooperative formation of larger vortices. The 3-dimensional analyses verify these results and show high 3-dimensional vortical structures which are growing when passing over a flap array. In case of the inserted flap array the vortex pairing process was delayed and accumulation of spanwise vorticity was forced to happen over the first rows of flaps, thus forming the larger structures. Already the used flap array configurations showed a significant impact influence on the jet evolution and the non-linear instabilities. Further investigations will analyze the influence of more parameters as the flap geometry or the distance to the jet flow and nozzle outlet
Star-shaped Local Density of States around Vortices in a Type II Superconductor
The electronic structure of vortices in a type II superconductor is analyzed
within the quasi-classical Eilenberger framework. The possible origin of a
sixfold ``star'' shape of the local density of states, observed by scanning
tunneling microscope experiments on NbSe, is examined in the light of the
three effects; the anisotropic pairing, the vortex lattice, and the anisotropic
density of states at the Fermi surface. Outstanding features of split parallel
rays of this star are well explained in terms of an anisotropic -wave
pairing. This reveals a rich internal electronic structure associated with a
vortex core.Comment: 4 pages, REVTeX, 3 figures available upon reques
Local density of states in the vortex lattice in a type II superconductor
Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical structure around a vortex core. On the other hand, at a
high field where the core regions substantially overlap each other, the LDOS is
sixfold star-shaped structure due to the vortex lattice effect. The orientation
of the star coincides with the experimental data of the scanning tunneling
microscopy. That is, the ray of the star extends toward the nearest-neighbor
(next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure
Superconductivity in SrNi2As2 Single Crystals
The electrical resistivity \rho(T) and heat capacity C(T) on single crystals
of SrNi2As2 and EuNi2As2 are reported. While there is no evidence for a
structural transition in either compound, SrNi2As2 is found to be a bulk
superconductor at T_c=0.62 K with a Sommerfeld coefficient of \gamma= 8.7
mJ/mol K^2 and a small upper critical field H_{c2} \sim 200 Oe. No
superconductivity was found in EuNi2As2 above 0.4 K, but anomalies in \rho and
C reveal that magnetic order associated with the Eu^{2+} magnetic moments
occurs at T_m = 14 K.Comment: 8 pages, 5 figure
Effects of gap anisotropy upon the electronic structure around a superconducting vortex
An isolated single vortex is considered within the framework of the
quasiclassical theory. The local density of states around a vortex is
calculated in a clean type II superconductor with an anisotropy. The anisotropy
of a superconducting energy gap is crucial for bound states around a vortex. A
characteristic structure of the local density of states, observed in the
layered hexagonal superconductor 2H-NbSe2 by scanning tunneling microscopy
(STM), is well reproduced if one assumes an anisotropic s-wave gap in the
hexagonal plane. The local density of states (or the bound states) around the
vortex is interpreted in terms of quasiparticle trajectories to facilitate an
understanding of the rich electronic structure observed in STM experiments. It
is pointed out that further fine structures and extra peaks in the local
density of states should be observed by STM.Comment: 11 pages, REVTeX; 20 PostScript figures; An Animated GIFS file for
the star-shaped vortex bound states is available at
http://mp.okayama-u.ac.jp/~hayashi/vortex.htm
What's wrong with this rebuttal?
A recent rebuttal to criticism of Bell's analysis is shown to be defective by
fault of failure to consider all hypothetical conditions input into the
derivation of Bell Inequalitites.Comment: 2 page
A Coupled Map Lattice Model for Rheological Chaos in Sheared Nematic Liquid Crystals
A variety of complex fluids under shear exhibit complex spatio-temporal
behaviour, including what is now termed rheological chaos, at moderate values
of the shear rate. Such chaos associated with rheological response occurs in
regimes where the Reynolds number is very small. It must thus arise as a
consequence of the coupling of the flow to internal structural variables
describing the local state of the fluid. We propose a coupled map lattice (CML)
model for such complex spatio-temporal behaviour in a passively sheared nematic
liquid crystal, using local maps constructed so as to accurately describe the
spatially homogeneous case. Such local maps are coupled diffusively to nearest
and next nearest neighbours to mimic the effects of spatial gradients in the
underlying equations of motion. We investigate the dynamical steady states
obtained as parameters in the map and the strength of the spatial coupling are
varied, studying local temporal properties at a single site as well as
spatio-temporal features of the extended system. Our methods reproduce the full
range of spatio-temporal behaviour seen in earlier one-dimensional studies
based on partial differential equations. We report results for both the one and
two-dimensional cases, showing that spatial coupling favours uniform or
periodically time-varying states, as intuitively expected. We demonstrate and
characterize regimes of spatio-temporal intermittency out of which chaos
develops. Our work suggests that such simplified lattice representations of the
spatio-temporal dynamics of complex fluids under shear may provide useful
insights as well as fast and numerically tractable alternatives to continuum
representations.Comment: 32 pages, single column, 20 figure
Caveolin-1 interacts with the chaperone complex TCP-1 and modulates its protein folding activity
Abstract.: We report that caveolin-1, one of the major structural protein of caveolae, interacts with TCP-1, a hetero-oligomeric chaperone complex present in all eukaryotic cells that contributes mainly to the folding of actin and tubulin. The caveolin-TCP-1 interaction entails the first 32 amino acids of the N-terminal segment of caveolin. Our data show that caveolin-1 expression is needed for the induction of TCP-1 actin folding function in response to insulin stimulation. Caveolin-1 phosphorylation at tyrosine residue 14 induces the dissociation of caveolin-1 from TCP-1 and activates actin folding. We show that the mechanism by which caveolin-1 modulates TCP-1 activity is indirect and involves the cytoskeleton linker filamin. Filamin is known to bind caveolin-1 and to function as a negative regulator of insulin-mediated signaling. Our data support the notion that the caveolin-filamin interaction contributes to restore insulin-mediated phosphorylation of caveolin, thus allowing the release of active TCP-
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