550 research outputs found
Comment on Mie Scattering from a Sonoluminescing Bubble with High Spatial and Temporal Resolution [Physical Review E 61, 5253 (2000)]
A key parameter underlying the existence of sonoluminescence (SL)is the time
relative to SL at which acoustic energy is radiated from the collapsed bubble.
Light scattering is one route to this quantity. We disagree with the statement
of Gompf and Pecha that -highly compressed water causes the minimum in
scattered light to occur 700ps before SL- and that this effect leads to an
overestimate of the bubble wall velocity. We discuss potential artifacts in
their experimental arrangement and correct their description of previous
experiments on Mie scattering.Comment: 10 pages, 2 figure
Force Detection Using a Fiber-Optic Cantilever
A force measurement technique has been developed that utilizes a clamped
fiber optic element both as a cantilever and as a highly sensitive probe of the
static and dynamic displacement of a sample that is mounted near its free end.
Light from a 1.5 mW superluminescent diode coupled into the fiber is used to
detect displacement with 6*10/sup -13 m*Hz/sup -1/2 sensitivity for frequencies
above 40 kHz. This technique has been used to study the interaction between
macroscopic bodies with atomic sensitivity. Here, we report measurements of
stiffness of junctions that form when two gold surfaces are brought into
contact.Comment: 16 pages, 4 figure
Resolving High Amplitude Surface Motion with Diffusing Light
A new technique has been developed for the purpose of imaging high amplitude surface motion. With this method one can quantitatively measure the transition to ripple wave turbulence. In addition, one can measure the phase of the turbulent state. These experiments reveal strong coherent structures in turbulent range of motion
Damping of sound waves in superfluid nucleon-hyperon matter of neutron stars
We consider sound waves in superfluid nucleon-hyperon matter of massive
neutron-star cores. We calculate and analyze the speeds of sound modes and
their damping times due to the shear viscosity and non-equilibrium weak
processes of particle transformations. For that, we employ the dissipative
relativistic hydrodynamics of a superfluid nucleon-hyperon mixture, formulated
recently [M.E. Gusakov and E.M. Kantor, Phys. Rev. D78, 083006 (2008)]. We
demonstrate that the damping times of sound modes calculated using this
hydrodynamics and the ordinary (nonsuperfluid) one, can differ from each other
by several orders of magnitude.Comment: 15 pages, 5 figures, Phys. Rev. D accepte
Transport coefficients from the Boson Uehling-Uhlenbeck Equation
We derive microscopic expressions for the bulk viscosity, shear viscosity and
thermal conductivity of a quantum degenerate Bose gas above , the critical
temperature for Bose-Einstein condensation. The gas interacts via a contact
potential and is described by the Uehling-Uhlenbeck equation. To derive the
transport coefficients, we use Rayleigh-Schrodinger perturbation theory rather
than the Chapman-Enskog approach. This approach illuminates the link between
transport coefficients and eigenvalues of the collision operator. We find that
a method of summing the second order contributions using the fact that the
relaxation rates have a known limit improves the accuracy of the computations.
We numerically compute the shear viscosity and thermal conductivity for any
boson gas that interacts via a contact potential. We find that the bulk
viscosity remains identically zero as it is for the classical case.Comment: 10 pages, 2 figures, submitted to Phys. Rev.
Overconfidence and gender gaps in redistributive preferences:Cross-Country experimental evidence
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