Telesonography In Emergency Medicine : A Systematic Review

Funding: No specific funding was received for this work; however LE’s salary was paid from funding for the SatCare trial into remotely supported prehospital ultrasound, provided by the European Space Agency in collaboration with ViaSat (contract SC16005). The specific roles of this author are articulated in the ‘author contributions’ section. These funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Experimental and numerical validation of active flaps for wind turbine blades

An industrial active flap concept for wind turbine rotor blades is validated numerically by means of CFD, as well as experimentally in a wind tunnel environment. This paper presents the numerical and experimental results, as well as a discussion regarding the testing of airfoils equipped with active flaps with a highly loaded aft portion. A conceptual implementation for an offshore wind turbine and the potential for load reduction is shown by means of aeroelastic calculations. The work presented herein is conducted within the frame of the Induflap2 project and is partially funded by the Danish funding board EUDP

Quantum Hall Effects in Graphene-Based Two-Dimensional Electron Systems

In this article we review the quantum Hall physics of graphene based two-dimensional electron systems, with a special focus on recent experimental and theoretical developments. We explain why graphene and bilayer graphene can be viewed respectively as J=1 and J=2 chiral two-dimensional electron gases (C2DEGs), and why this property frames their quantum Hall physics. The current status of experimental and theoretical work on the role of electron-electron interactions is reviewed at length with an emphasis on unresolved issues in the field, including assessing the role of disorder in current experimental results. Special attention is given to the interesting low magnetic field limit and to the relationship between quantum Hall effects and the spontaneous anomalous Hall effects that might occur in bilayer graphene systems in the absence of a magnetic field

Energy gaps at neutrality point in bilayer graphene in a magnetic field

Utilizing the Baym-Kadanoff formalism with the polarization function calculated in the random phase approximation, the dynamics of the $\nu=0$ quantum Hall state in bilayer graphene is analyzed. Two phases with nonzero energy gap, the ferromagnetic and layer asymmetric ones, are found. The phase diagram in the plane $(\tilde{\Delta}_0,B)$, where $\tilde{\Delta}_0$ is a top-bottom gates voltage imbalance, is described. It is shown that the energy gap scales linearly, $\Delta E\sim 14 B[T]K, with magnetic field.Comment: 5 pages, 3 figures, title changed, references added, JETP Letters versio

Phase diagram of insulating crystal and quantum Hall states in ABC-stacked trilayer graphene

In the presence of a perpendicular magnetic field, ABC-stacked trilayer graphene's chiral band structure supports a 12-fold degenerate N=0 Landau level (LL). Along with the valley and spin degrees of freedom, the zeroth LL contains additional quantum numbers associated with the LL orbital index $$. Remote inter-layer hopping terms and external potential difference $\Delta_{B}$ between the layers lead to LL splitting by introducing a gap $$ between the degenerate zero-energy triplet LL orbitals. Assuming that the spin and valley degrees of freedom are frozen, we study the phase diagram of this system resulting from competition of the single particle LL splitting and Coulomb interactions within the Hartree-Fock approximation at integer filling factors. Above a critical value $\Delta_{LL}^{c}$ of the external potential difference i,e, for $|\Delta_{LL}| >\Delta_{LL}^{c}$, the ground state is a uniform quantum Hall state where the electrons occupy the lowest unoccupied LL orbital index. For $|\Delta_{LL}| <\Delta_{LL}^{c}$ (which corresponds to large positive or negative values of $\Delta_{B}$) the uniform QH state is unstable to the formation of a crystal state at integer filling factors. This phase transition should be characterized by a Hall plateau transition as a function of $\Delta_{LL}$ at a fixed filling factor. We also study the properties of this crystal state and discuss its experimental detection.Comment: 16 pages with 13 figure

Coulomb impurity under magnetic field in graphene: a semiclassical approach

We address the problem of a Coulomb impurity in graphene in the presence of a perpendicular uniform magnetic field. We show that the problem can be solved below the supercritical impurity magnitude within the WKB approximation. Without impurity the semiclassical energies correctly reproduce the Landau level spectrum. For a given Landau level the WKB energy depends on the absolute value of angular momentum in a way which is consistent with the exact diagonalization result. Below the supercritical impurity magnitude, the WKB solution can be expanded as a convergent series in powers of the effective fine structure constant. Relevance of our results to validity of the widely used Landau level projection approximation is discussed.Comment: 10 pages, 5 figure

The effective fine structure constant of freestanding graphene measured in graphite

Electrons in graphene behave like Dirac fermions, permitting phenomena from high energy physics to be studied in a solid state setting. A key question is whether or not these Fermions are critically influenced by Coulomb correlations. We performed inelastic x-ray scattering experiments on crystals of graphite, and applied reconstruction algorithms to image the dynamical screening of charge in a freestanding, graphene sheet. We found that the polarizability of the Dirac fermions is amplified by excitonic effects, improving screening of interactions between quasiparticles. The strength of interactions is characterized by a scale-dependent, effective fine structure constant, \alpha *(k,\omega), whose value approaches \alpha * ~ 1/7 at low energy and large distances. This value is substantially smaller than the nominal \alpha = 2.2, suggesting that, on the whole, graphene is more weakly interacting than previously believed.Comment: 28 pages, 10 figures, 2 animation

Evaluating acupuncture and standard care for pregnant women with back pain:the EASE Back pilot randomised controlled trial (ISRCTN49955124)

Background Low back pain (LBP) and pelvic girdle pain (PGP) during pregnancy are common and often accepted as a ‘normal’ part of pregnancy. Many women receive little in the way of treatment, and yet pain interferes with sleep, daily activities and work and leads to increasing requests for induction of labour or elective caesarean section. The aim of this study was to assess the feasibility of a full RCT evaluating the benefit of acupuncture for pregnancy-related back pain. Methods This study is a single-centre, three-arm pilot RCT in one large maternity unit and associated antenatal and physiotherapy clinics. Women were eligible if they had pregnancy-related LBP with or without PGP. Exclusions included a history of miscarriage, high risk of early labour or pre-eclampsia, PGP only and previous acupuncture. Interventions were standard care (SC): a self-management booklet with physiotherapy if needed. SC+TA: the booklet and physiotherapy comprising true (penetrating) acupuncture, advice and exercise. SC+NPA: the booklet and physiotherapy comprising non-penetrating acupuncture, advice and exercise. Remote telephone randomisation used a 1:1:1 allocation ratio stratified by gestational weeks. Three measures of pain/function were compared to inform the primary outcome measure in a full RCT: the Pelvic Girdle Questionnaire (PGQ), Oswestry Disability Index (ODI) and 11-point 0–10 numerical rating scale for pain. Analysis focused on process evaluation of recruitment, retention, descriptive information on outcomes, adherence to treatment, occurrence of adverse events and impact of physiotherapist training. Results One hundred twenty-five women were randomised (45% of those eligible) between April and October 2013; 73% (n = 91) provided 8-week follow-up data. Three of six recruitment methods accounted for 82% of total uptake: screening questionnaire at the 20-week scan, community midwives issuing study cards, and self-referral following local awareness initiatives. Physiotherapists’ self-confidence on managing pregnancy-related LBP improved post training. The PGQ is suitable as the primary outcome in a full trial. The average number of treatment sessions in both SC+TA and SC+NPA was six (in line with treatment protocols). No serious adverse events attributable to the trial treatments were reported. Conclusions A full RCT is feasible and would provide evidence about the effectiveness of acupuncture and inform treatment choices for women with pregnancy-related LBP

Spin and valley quantum Hall ferromagnetism in graphene

In a graphene Landau level (LL), strong Coulomb interactions and the fourfold spin/valley degeneracy lead to an approximate SU(4) isospin symmetry. At partial filling, exchange interactions can spontaneously break this symmetry, manifesting as additional integer quantum Hall plateaus outside the normal sequence. Here we report the observation of a large number of these quantum Hall isospin ferromagnetic (QHIFM) states, which we classify according to their real spin structure using temperature-dependent tilted field magnetotransport. The large measured activation gaps confirm the Coulomb origin of the broken symmetry states, but the order is strongly dependent on LL index. In the high energy LLs, the Zeeman effect is the dominant aligning field, leading to real spin ferromagnets with Skyrmionic excitations at half filling, whereas in the `relativistic' zero energy LL, lattice scale anisotropies drive the system to a spin unpolarized state, likely a charge- or spin-density wave.Comment: Supplementary information available at http://pico.phys.columbia.ed