7 research outputs found
Soft Magnetorotons and Broken-Symmetry States in Bilayer Quantum Hall Ferromagnets
The recent report on the observation of soft magnetorotons in the dispersion
of charge-density excitations across the tunneling gap in coupled bilayers at
total Landau level filling factor is reviewed. The inelastic light
scattering experiments take advantage of the breakdown of wave-vector
conservation that occurs under resonant excitation. The results offer evidence
that in the quantum Hall state there is a roton that softens and sharpens
markedly when the phase boundary for transitions to highly-correlated
compressible states is approached. These findings are interpreted with
Hartree-Fock evaluations of the dynamic structure factor. The model includes
the effect of disorder in the breakdown of wave-vector conservation and
resonance enhancement profiles within a phenomenological approach. These
results link the softening of magnetorotons to enhanced excitonic Coulomb
interactions in the ferromagnetic bilayers.Comment: 6 pages, 5 figures; conference: EP2DS-1
Metamorphosis of a Quantum Hall Bilayer State into a Composite Fermion Metal
Composite fermion metal states emerge in quantum Hall bilayers at total
Landau level filling factor =1 when the tunneling gap collapses by
application of in-plane components of the external magnetic field. Evidence of
this transformation is found in the continua of spin excitations observed by
inelastic light scattering below the spin-wave mode at the Zeeman energy. The
low-lying spin modes are interpreted as quasiparticle excitations with
simultaneous changes in spin orientation and composite fermion Landau level
index.Comment: 4 pages 4 figure
Effect of surgical experience and spine subspecialty on the reliability of the {AO} Spine Upper Cervical Injury Classification System
OBJECTIVE
The objective of this paper was to determine the interobserver reliability and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeon experience (< 5 years, 5â10 years, 10â20 years, and > 20 years) and surgical subspecialty (orthopedic spine surgery, neurosurgery, and "other" surgery).
METHODS
A total of 11,601 assessments of upper cervical spine injuries were evaluated based on the AO Spine Upper Cervical Injury Classification System. Reliability and reproducibility scores were obtained twice, with a 3-week time interval. Descriptive statistics were utilized to examine the percentage of accurately classified injuries, and Pearsonâs chi-square or Fisherâs exact test was used to screen for potentially relevant differences between study participants. Kappa coefficients (Îș) determined the interobserver reliability and intraobserver reproducibility.
RESULTS
The intraobserver reproducibility was substantial for surgeon experience level (< 5 years: 0.74 vs 5â10 years: 0.69 vs 10â20 years: 0.69 vs > 20 years: 0.70) and surgical subspecialty (orthopedic spine: 0.71 vs neurosurgery: 0.69 vs other: 0.68). Furthermore, the interobserver reliability was substantial for all surgical experience groups on assessment 1 (< 5 years: 0.67 vs 5â10 years: 0.62 vs 10â20 years: 0.61 vs > 20 years: 0.62), and only surgeons with > 20 years of experience did not have substantial reliability on assessment 2 (< 5 years: 0.62 vs 5â10 years: 0.61 vs 10â20 years: 0.61 vs > 20 years: 0.59). Orthopedic spine surgeons and neurosurgeons had substantial intraobserver reproducibility on both assessment 1 (0.64 vs 0.63) and assessment 2 (0.62 vs 0.63), while other surgeons had moderate reliability on assessment 1 (0.43) and fair reliability on assessment 2 (0.36).
CONCLUSIONS
The international reliability and reproducibility scores for the AO Spine Upper Cervical Injury Classification System demonstrated substantial intraobserver reproducibility and interobserver reliability regardless of surgical experience and spine subspecialty. These results support the global application of this classification system
An Interdisciplinary Methodology for the Characterization and Visualization of the Heritage of Roadway Corridors
Roads, particularly since the advent of motorized traffic, have hugely impacted contemporary landscapes. Although their significance was noted in the 1980s, specific roadway-heritage studies are scarce. Research in different disciplines has identified certain features of roads, but an integrated approach to roadway heritage or a consensus on what this constitutes are lacking. This article proposes an interdisciplinary methodology to assess roadway heritage. Roadways are interpreted within the framework of semantic openness that currently characterizes heritage studies, territory being the basic element of interpretation. Rather than a fragmented approach to conservation, the research defines integrated heritage configurations where natural, cultural, and historical features combine to produce a cohesive form of heritage. GIS (Geographical information systems) technology is used with an online database to assess the complexity of roadway heritage. ICT (Information and communications technology) strategies to raise public awareness are outlined. The methodology is applied to assess the historical N-340 Mediterranean roadway corridor in Spain