5,665 research outputs found
Motion of magnetotactic bacteria swarms in an external field
Magnetotactic bacteria moving on circular orbits form hydrodynamically bound
states. When close to a surface and with the tilting of the field in a
direction close to the perpendicular to this surface these swarms move
perpendicularly to the tilting angle. We describe quantitatively this motion by
a continuum model with couple stress arising from the torques produced by the
rotary motors of the amphitrichous magnetotactic bacteria. The model not only
correctly describes the change of direction of swarm motion while inverting the
tangential field but also predicts reasonable value of the torque produced by
the rotary motors
Swinging of red blood cells under shear flow
We reveal that under moderate shear stress (of the order of 0.1 Pa) red blood
cells present an oscillation of their inclination (swinging) superimposed to
the long-observed steady tanktreading (TT) motion. A model based on a fluid
ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape
memory) predicts all observed features of the motion: an increase of both
swinging amplitude and period (1/2 the TT period) upon decreasing the shear
stress, a shear stress-triggered transition towards a narrow shear stress-range
intermittent regime of successive swinging and tumbling, and a pure tumbling
motion at lower shear stress-values.Comment: 4 pages 5 figures submitted to Physical Review Letter
PMD67 The Cost-Effectiveness of Transcatheter Aortic Valve Implantation in Elderly Patients with Severe Aortic Stenosis Who are Contraindicated for Conventional Surgical Aortic Valve replacement in the United Kingdom
Characterization of the glass transition in vitreous silica by temperature scanning small-angle X-ray scattering
The temperature dependence of the x-ray scattering in the region below the
first sharp diffraction peak was measured for silica glasses with low and high
OH content (GE-124 and Corning 7980). Data were obtained upon scanning the
temperature at 10, 40 and 80 K/min between 400 K and 1820 K. The measurements
resolve, for the first time, the hysteresis between heating and cooling through
the glass transition for silica glass, and the data have a better signal to
noise ratio than previous light scattering and differential thermal analysis
data. For the glass with the higher hydroxyl concentration the glass transition
is broader and at a lower temperature. Fits of the data to the
Adam-Gibbs-Fulcher equation provide updated kinetic parameters for this very
strong glass. The temperature derivative of the observed X-ray scattering
matches that of light scattering to within 14%.Comment: EurophysicsLetters, in pres
Curative radiotherapy for non-small cell lung cancer : practice changing and changing practice?
Pattern Stability and Trijunction Motion in Eutectic Solidification
We demonstrate by both experiments and phase-field simulations that lamellar
eutectic growth can be stable for a wide range of spacings below the point of
minimum undercooling at low velocity, contrary to what is predicted by existing
stability analyses. This overstabilization can be explained by relaxing Cahn's
assumption that lamellae grow locally normal to the eutectic interface.Comment: 4 pages, 5 eps figure
Sources and sinks separating domains of left- and right-traveling waves: Experiment versus amplitude equations
In many pattern forming systems that exhibit traveling waves, sources and
sinks occur which separate patches of oppositely traveling waves. We show that
simple qualitative features of their dynamics can be compared to predictions
from coupled amplitude equations. In heated wire convection experiments, we
find a discrepancy between the observed multiplicity of sources and theoretical
predictions. The expression for the observed motion of sinks is incompatible
with any amplitude equation description.Comment: 4 pages, RevTeX, 3 figur
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