1,490 research outputs found
Velocity Fluctuations in Electrostatically Driven Granular Media
We study experimentally the particle velocity fluctuations in an
electrostatically driven dilute granular gas. The experimentally obtained
velocity distribution functions have strong deviations from Maxwellian form in
a wide range of parameters. We have found that the tails of the distribution
functions are consistent with a stretched exponential law with typical
exponents of the order 3/2. Molecular dynamic simulations shows qualitative
agreement with experimental data. Our results suggest that this non-Gaussian
behavior is typical for most inelastic gases with both short and long range
interactions.Comment: 4 pages, 4 figure
Correlations, compressibility, and capacitance in double-quantum-well systems in the quantum Hall regime
In the quantum Hall regime, electronic correlations in double-layer
two-dimensional electron systems are strong because the kinetic energy is
quenched by Landau quantization. In this article we point out that these
correlations are reflected in the way the partitioning of charge between the
two-layers responds to a bias potential. We report on illustrative calculations
based on an unrestricted Hartree-Fock approximation which allows for
spontaneous inter-layer phase coherence. The possibility of studying
inter-layer correlations by capacitive coupling to separately contacted
two-dimensional layers is discussed in detail.Comment: RevTex style, 21 pages, 6 postscript figures in a separate file;
Phys. Rev. B (in press
Liquid antiferromagnets in two dimensions
It is shown that, for proper symmetry of the parent lattice,
antiferromagnetic order can survive in two-dimensional liquid crystals and even
isotropic liquids of point-like particles, in contradiction to what common
sense might suggest. We discuss the requirements for antiferromagnetic order in
the absence of translational and/or orientational lattice order. One example is
the honeycomb lattice, which upon melting can form a liquid crystal with
quasi-long-range orientational and antiferromagnetic order but short-range
translational order. The critical properties of such systems are discussed.
Finally, we draw conjectures for the three-dimensional case.Comment: 4 pages RevTeX, 4 figures include
The risk of cardiac failure following metal-on-metal hip arthroplasty
Aims
The aim of this study was to determine whether patients with metal-on-metal (MoM)
arthroplasties of the hip have an increased risk of cardiac failure compared with those with
alternative types of arthroplasties (non-MoM).
Patients and Methods
A linkage study between the National Joint Registry, Hospital Episodes Statistics and records
of the Office for National Statistics on deaths was undertaken. Patients who underwent
elective total hip arthroplasty between January 2003 and December 2014 with no past history
of cardiac failure were included and stratified as having either a MoM (n = 53 529) or a nonMoM
(n = 482 247) arthroplasty. The primary outcome measure was the time to an
admission to hospital for cardiac failure or death. Analysis was carried out using data from
all patients and from those matched by propensity score.
Results
The risk of cardiac failure was lower in the MoM cohort compared with the non-MoM cohort
(adjusted hazard ratio (aHR) 0.901; 95% confidence interval (CI) 0.853 to 0.953). The risk of
cardiac failure was similar following matching (aHR 0.909; 95% CI 0.838 to 0.987) and the
findings were consistent in subgroup analysis.
Conclusion
The risk of cardiac failure following total hip arthroplasty was not increased in those in
whom MoM implants were used, compared with those in whom other types of prostheses
were used, in the first seven years after surgery.
Cite this article: Bone Joint J 2018;100-B:20–
Magnetic Order in YBaCuO Superconductors
Polarized and unpolarized neutron diffraction has been used to search for
magnetic order in YBaCuO superconductors. Most of the
measurements were made on a high quality crystal of YBaCuO. It
is shown that this crystal has highly ordered ortho-II chain order, and a sharp
superconducting transition. Inelastic scattering measurements display a very
clean spin-gap and pseudogap with any intensity at 10 meV being 50 times
smaller than the resonance intensity. The crystal shows a complicated magnetic
order that appears to have three components. A magnetic phase is found at high
temperatures that seems to stem from an impurity with a moment that is in the
- plane, but disordered on the crystal lattice. A second ordering occurs
near the pseudogap temperature that has a shorter correlation length than the
high temperature phase and a moment direction that is at least partly along the
c-axis of the crystal. Its moment direction, temperature dependence, and Bragg
intensities suggest that it may stem from orbital ordering of the -density
wave (DDW) type. An additional intensity increase occurs below the
superconducting transition. The magnetic intensity in these phases does not
change noticeably in a 7 Tesla magnetic field aligned approximately along the
c-axis. Searches for magnetic order in YBaCuO show no signal
while a small magnetic intensity is found in YBaCuO that is
consistent with c-axis directed magnetic order. The results are contrasted with
other recent neutron measurements.Comment: 11 pages with 10 figure
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Development of superior asphalt recycling agents: Phase 1, Technical feasibility. Technical progress report
About every 12 years, asphalt roads must be reworked, and this is usually done by placing thick layers (hot-mix overlays) of new material on top of failed material, resulting in considerable waste of material and use of new asphalt binder. A good recycling agent is needed, not only to reduce the viscosity of the aged material but also to restore compatibility. Objective is to establish the technical feasibility (Phase I) of determining the specifications and operating parameters for producing high quality recycling agents which will allow most/all the old asphalt-based road material to be recycled. It is expected that supercritical fractionation can be used. The advanced road aging simulation procedure will be used to study aging of blends of old asphalt and recycling agents
Persistent Spin Currents in Helimagnets
We demonstrate that weak external magnetic fields generate dissipationless
spin currents in the ground state of systems with spiral magnetic order. Our
conclusions are based on phenomenological considerations and on microscopic
mean-field theory calculations for an illustrative toy model. We speculate on
possible applications of this effect in spintronic devices.Comment: 9 pages, 6 figures, updated version as published, Journal referenc
Determinants of disease penetrance in PRPF31-associated retinopathy
Retinitis pigmentosa 11 (RP11) is caused by dominant mutations in PRPF31, however a significant proportion of mutation carriers do not develop retinopathy. Here, we investigated the relationship between CNOT3 polymorphism, MSR1 repeat copy number and disease penetrance in RP11 patients and non-penetrant carriers (NPCs). We further characterized PRPF31 and CNOT3 expression in fibroblasts from eight RP11 patients and one NPC from a family carrying the c.1205C>T variant. Retinal organoids (ROs) and retinal pigment epithelium (RPE) were differentiated from induced pluripotent stem cells derived from RP11 patients, an NPC and a control subject. All RP11 patients were homozygous for the 3-copy MSR1 repeat in the PRPF31 promoter, while 3/5 NPCs carried a 4-copy MSR1 repeat. The CNOT3 rs4806718 genotype did not correlate with disease penetrance. PRFP31 expression declined with age in adult cadaveric retina. PRPF31 and CNOT3 expression was reduced in RP11 fibroblasts, RO and RPE compared with controls. Both RP11 and NPC RPE displayed shortened primary cilia compared with controls, however a subpopulation of cells with normal cilia lengths was present in NPC RPE monolayers. Our results indicate that RP11 non-penetrance is associated with the inheritance of a 4-copy MSR1 repeat, but not with CNOT3 polymorphisms
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