27,711 research outputs found
Coherent caloritronics in Josephson-based nanocircuits
We describe here the first experimental realization of a heat interferometer,
thermal counterpart of the well-known superconducting quantum interference
device (SQUID). These findings demonstrate, on the first place, the existence
of phase-dependent heat transport in Josephson-based superconducting circuits
and, on the second place, open the way to novel ways of mastering heat at the
nanoscale. Combining the use of external magnetic fields for phase biasing and
different Josephson junction architectures we show here that a number of heat
interference patterns can be obtained. The experimental realization of these
architectures, besides being relevant from a fundamental physics point of view,
might find important technological application as building blocks of
phase-coherent quantum thermal circuits. In particular, the performance of two
different heat rectifying devices is analyzed.Comment: 34 pages, 15 figures, review article for Ultra-low temperatures and
nanophysics ULTN2013. Microkelvin Proceeding
Lagrangian Volume Deformations around Simulated Galaxies
We present a detailed analysis of the local evolution of 206 Lagrangian
Volumes (LVs) selected at high redshift around galaxy seeds, identified in a
large-volume cold dark matter (CDM) hydrodynamical
simulation. The LVs have a mass range of . We
follow the dynamical evolution of the density field inside these initially
spherical LVs from up to , witnessing highly
non-linear, anisotropic mass rearrangements within them, leading to the
emergence of the local cosmic web (CW). These mass arrangements have been
analysed in terms of the reduced inertia tensor , focusing on the
evolution of the principal axes of inertia and their corresponding
eigendirections, and paying particular attention to the times when the
evolution of these two structural elements declines. In addition, mass and
component effects along this process have also been investigated. We have found
that deformations are led by dark matter dynamics and they transform most of
the initially spherical LVs into prolate shapes, i.e. filamentary structures.
An analysis of the individual freezing-out time distributions for shapes and
eigendirections shows that first most of the LVs fix their three axes of
symmetry (like a skeleton) early on, while accretion flows towards them still
continue. Very remarkably, we have found that more massive LVs fix their
skeleton earlier on than less massive ones. We briefly discuss the
astrophysical implications our findings could have, including the galaxy
mass-morphology relation and the effects on the galaxy-galaxy merger parameter
space, among others.Comment: 23 pages, 20 figures. Minor editorial improvement
Improved wear performance of ultra high molecular weight polyethylene coated with hydrogenated diamond like carbon
Hydrogenated diamond like carbon (DLCH) thin films were deposited on medical grade ultra high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition. The DLCH coating thicknesses ranged from 250 to 700. nm. The substrates were disks made of UHMWPEs typically used for soft components in artificial joints, namely virgin GUR 1050 and highly crosslinked (gamma irradiated in air to 100. kGy) UHMWPEs. Mechanical and tribological properties under bovine serum lubrication at body temperature were assessed on coated and uncoated polyethylenes by means of nano-hardness and ball-on-disk tests, respectively. Morphological features of the worn surfaces were obtained by confocal microscopy and scanning electron microscopy. This study confirms an increase in surface hardness and good wear resistance for coated materials after 24. h of sliding test compared to uncoated polyethylene. These results point out that to coat UHMWPE with DLCH films could be a potential method to reduce backside wear in total hip and knee arthroplasties.Ministerio de Ciencia y Educación MAT2006-12603- C02-01, CSD2008-0002
Family Dependence in SU(3)_C X SU(3)_L X U(1)_X models
Using experimental results at the Z-pole and atomic parity violation, we
perform a chi-squared fit at 95% CL to obtain family-dependent bounds to Z_2
mass and Z-Z' mixing angle in the framework of SU(3)_C X SU(3)_L X U(1)_X
models. The allowed regions depend on the assignment of the quark families in
mass eigenstates into the three different families in weak eigenstates that
cancel anomaliesComment: 14 pages, 2 figures, LaTeX2e; added references, added equations with
electroweak corrections for section 4. Version to appear in Phys. Rev.
Nongalvanic thermometry for ultracold two-dimensional electron domains
Measuring the temperature of a two-dimensional electron gas at temperatures
of a few mK is a challenging issue, which standard thermometry schemes may fail
to tackle. We propose and analyze a nongalvanic thermometer, based on a quantum
point contact and quantum dot, which delivers virtually no power to the
electron system to be measured.Comment: 5 pages, 3 figure
Fully-Balanced Heat Interferometer
A tunable and balanced heat interferometer is proposed and analyzed. The
device consists of two superconductors linked together to form a double-loop
interrupted by three Josephson junctions coupled in parallel. Both
superconductors are held at different temperatures allowing the heat currents
flowing through the structure to interfere. As we show here, thermal transport
is coherently modulated through the application of a magnetic flux.
Furthermore, such modulation can be tailored at will through the application of
an extra control flux. In addition we show that, provided a proper choice of
the system parameters, a fully balanced interferometer is obtained. The latter
means that the phase-coherent part of heat current can be controlled to the
extent of being fully suppressed. Such a device allows for a versatile
operation appearing, therefore, as an attractive key to the onset of
low-temperature coherent caloritronic circuits
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