6,552 research outputs found
The Biogun: A novel way of eradicating methicillin-resistant Staphylococcus aureus colonization in diabetic foot ulcers
Luby Transform Coding Aided Iterative Detection for Downlink SDMA Systems
A Luby Transform (LT) coded downlink Spatial Division Multiple Access (SDMA) system using iterative detection is proposed, which invokes a low-complexity near-Maximum-Likelihood (ML) Sphere Decoder (SD). The Ethernet-based Internet section of the transmission chain inflicts random packet erasures, which is modelled by the Binary Erasure Channel (BEC), which the wireless downlink imposes both fading and noise. A novel log-Likelihood Ratio based packet reliability metric is used for identifying the channel-decoded packets, which are likely to be error-infested. Packets having residual errors must not be passed on to the KT decoder for the sake of avoiding LT-decoding –induced error propagation. The proposed scheme is capable of maintaining an infinitesimally low packet error ratio in the downlink of the wireless Internet for Eb/n0 values in excess of about 3dB
Defect generation at the Si–SiO₂ interface following corona charging
A combination of capacitance-voltage and lifetime decay measurements is used to show that corona biasing of silicon oxidized samples results in the generation of additional interface defects and an increase in surface recombination. The onset of interface degradation occurs at relatively low electric fields, estimated to be less than ∼+∕−1.2MV∕cm. The majority of the defects generated by corona biasing can be removed by a short annealing at 400°C. The results are consistent with the hypothesis that atomic hydrogen is chiefly responsible for the observed degradation. Corona biasing, even at low electric fields, cannot be relied on as a noninvasive characterization tool.Support from the Australian Research Council for this work
is acknowledged
A smooth introduction to the wavefront set
The wavefront set provides a precise description of the singularities of a
distribution. Because of its ability to control the product of distributions,
the wavefront set was a key element of recent progress in renormalized quantum
field theory in curved spacetime, quantum gravity, the discussion of time
machines or quantum energy inequalitites. However, the wavefront set is a
somewhat subtle concept whose standard definition is not easy to grasp. This
paper is a step by step introduction to the wavefront set, with examples and
motivation. Many different definitions and new interpretations of the wavefront
set are presented. Some of them involve a Radon transform.Comment: 29 pages, 7 figure
Competing magnetic fluctuations in Sr3Ru2O7 probed by Ti doping
We report the effect of nonmagnetic Ti4+ impurities on the electronic and
magnetic properties of Sr3Ru2O7. Small amounts of Ti suppress the
characteristic peak in magnetic susceptibility near 16 K and result in a sharp
upturn in specific heat. The metamagnetic quantum phase transition and related
anomalous features are quickly smeared out by small amounts of Ti. These
results provide strong evidence for the existence of competing magnetic
fluctuations in the ground state of Sr3Ru2O7. Ti doping suppresses the low
temperature antiferromagnetic interactions that arise from Fermi surface
nesting, leaving the system in a state dominated by ferromagnetic fluctuations.Comment: 5 pages, 4 figures, 1 tabl
Quantum magnetism and counterflow supersolidity of up-down bosonic dipoles
We study a gas of dipolar Bosons confined in a two-dimensional optical
lattice. Dipoles are considered to point freely in both up and down directions
perpendicular to the lattice plane. This results in a nearest neighbor
repulsive (attractive) interaction for aligned (anti-aligned) dipoles. We find
regions of parameters where the ground state of the system exhibits insulating
phases with ferromagnetic or anti-ferromagnetic ordering, as well as with
rational values of the average magnetization. Evidence for the existence of a
novel counterflow supersolid quantum phase is also presented.Comment: 8 pages, 6 figure
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Osteocyte dysfunction promotes osteoarthritis through MMP13-dependent suppression of subchondral bone homeostasis.
Osteoarthritis (OA), long considered a primary disorder of articular cartilage, is commonly associated with subchondral bone sclerosis. However, the cellular mechanisms responsible for changes to subchondral bone in OA, and the extent to which these changes are drivers of or a secondary reaction to cartilage degeneration, remain unclear. In knee joints from human patients with end-stage OA, we found evidence of profound defects in osteocyte function. Suppression of osteocyte perilacunar/canalicular remodeling (PLR) was most severe in the medial compartment of OA subchondral bone, with lower protease expression, diminished canalicular networks, and disorganized and hypermineralized extracellular matrix. As a step toward evaluating the causality of PLR suppression in OA, we ablated the PLR enzyme MMP13 in osteocytes while leaving chondrocytic MMP13 intact, using Cre recombinase driven by the 9.6-kb DMP1 promoter. Not only did osteocytic MMP13 deficiency suppress PLR in cortical and subchondral bone, but it also compromised cartilage. Even in the absence of injury, osteocytic MMP13 deficiency was sufficient to reduce cartilage proteoglycan content, change chondrocyte production of collagen II, aggrecan, and MMP13, and increase the incidence of cartilage lesions, consistent with early OA. Thus, in humans and mice, defects in PLR coincide with cartilage defects. Osteocyte-derived MMP13 emerges as a critical regulator of cartilage homeostasis, likely via its effects on PLR. Together, these findings implicate osteocytes in bone-cartilage crosstalk in the joint and suggest a causal role for suppressed perilacunar/canalicular remodeling in osteoarthritis
adiabatic versus nonadiabatic dressed-state dynamics
We discuss how a recent pump-probe study [Kelkensberg et al., Phys. Rev. Lett.
103, 123005 (2009)] of the dissociative ionization of H2, under the combined
effect of a single extreme ultraviolet attosecond pulse and an intense near-
infrared pulse, actually represents a transition-state spectroscopy of the
strong-field dissociation step, i.e., of the (probe-pulse-)dressed H2+
molecular ion. The way the dissociation dynamics is influenced by the duration
of the near-infrared probe pulse, and by the time delay between the two
pulses, is discussed in terms of adiabatic versus nonadiabatic preparation and
transport of time-parametrized Floquet resonances associated with the
dissociating molecular ion. Under a long probe pulse, the field-free
vibrational states of the initial wave packet are transported, in a one-to-one
manner, onto the Floquet resonances defined by the field intensity of the
probe pulse and propagated adiabatically under the pulse. As the probe pulse
duration shortens, nonadiabatic transitions between the Floquet resonances
become important and manifest themselves in two respects: first, as a
vibrational shake-up effect occurring near the peak of the short pulse, and
second, through strong interference patterns in the fragment's kinetic energy
spectrum, viewed as a function of the time delay between the pump and the
probe pulses
Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies
Superconducting nanowires undergoing quantum phase-slips have potential for
impact in electronic devices, with a high-accuracy quantum current standard
among a possible toolbox of novel components. A key element of developing such
technologies is to understand the requirements for, and control the production
of, superconducting nanowires that undergo coherent quantum phase-slips. We
present three fabrication technologies, based on using electron-beam
lithography or neon focussed ion-beam lithography, for defining narrow
superconducting nanowires, and have used these to create nanowires in niobium
nitride with widths in the range of 20-250 nm. We present characterisation of
the nanowires using DC electrical transport at temperatures down to 300 mK. We
demonstrate that a range of different behaviours may be obtained in different
nanowires, including bulk-like superconducting properties with critical-current
features, the observation of phase-slip centres and the observation of zero
conductance below a critical voltage, characteristic of coherent quantum
phase-slips. We observe critical voltages up to 5 mV, an order of magnitude
larger than other reports to date. The different prominence of quantum
phase-slip effects in the various nanowires may be understood as arising from
the differing importance of quantum fluctuations. Control of the nanowire
properties will pave the way for routine fabrication of coherent quantum
phase-slip nanowire devices for technology applications.Comment: 14 pages, 8 figure
A Bogomol`nyi equation for intersecting domain walls
We argue that the Wess-Zumino model with quartic superpotential admits static
solutions in which three domain walls intersect at a junction. We derive an
energy bound for such junctions and show that configurations saturating it
preserve 1/4 supersymmetry.Comment: 4 pages revtex. No figures. Revised version to appear in Physical
Review Letters includes discussion of the supersymmetry algebr
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