Soft Spin Wave Near nu=1: Evidence for a Magnetic Instability in Skyrmion Systems

The ground state of the two dimensional electron gas near $\nu$=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from $\nu$=1, the ferromagnetic spin wave collapses and a new low-energy spin wave emerges below the Zeeman gap. The emergent spin wave shows soft behavior as its energy increases with temperature and reaches the Zeeman energy for temperatures above 2 K. The observed softening indicates an instability of the two dimensional electron gas towards a magnetic order that breaks spin rotational symmetry. We discuss our findings in light of the possible existence of a Skyrme crystal.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let

Type-II Bose-Mott insulators

The Mott insulating state formed from bosons is ubiquitous in solid He-4, cold atom systems, Josephson junction networks and perhaps underdoped high-Tc superconductors. We predict that close to the quantum phase transition to the superconducting state the Mott insulator is not at all as featureless as is commonly believed. In three dimensions there is a phase transition to a low temperature state where, under influence of an external current, a superconducting state consisting of a regular array of 'wires' that each carry a quantized flux of supercurrent is realized. This prediction of the "type-II Mott insulator" follows from a field theoretical weak-strong duality, showing that this 'current lattice' is the dual of the famous Abrikosov lattice of magnetic fluxes in normal superconductors. We argue that this can be exploited to investigate experimentally whether preformed Cooper pairs exist in high-Tc superconductors.Comment: RevTeX, 17 pages, 6 figures, published versio

Anomalous dissipation mechanism and Hall quantization limit in polycrystalline graphene grown by chemical vapor deposition

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).-- et al.We report on the observation of strong backscattering of charge carriers in the quantum Hall regime of polycrystalline graphene, grown by chemical vapor deposition, which alters the accuracy of the Hall resistance quantization. The temperature and magnetic field dependence of the longitudinal conductance exhibits unexpectedly smooth power-law behaviors, which are incompatible with a description in terms of variable range hopping or thermal activation but rather suggest the existence of extended or poorly localized states at energies between Landau levels. Such states could be caused by the high density of line defects (grain boundaries and wrinkles) that cross the Hall bars, as revealed by structural characterizations. Numerical calculations confirm that quasi-one-dimensional extended nonchiral states can form along such line defects and short circuit the Hall bar chiral edge states.This research has received funding from the Agence Nationale de la Recherche (ANR), Metrograph project (Grant No. ANR-2011-NANO-004. It has been performed within the EMRP (European Metrology Research Program), project SIB51, Graphohm. The EMRP is jointly funded by the EMRP participating countries within EURAMET (European association of national metrology institutes) and the European Union.Peer Reviewe

Multiple quantum phases in graphene with enhanced spin-orbit coupling: From the quantum spin hall regime to the spin hall effect and a robust metallic state

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).We report an intriguing transition from the quantum spin Hall phase to the spin Hall effect upon segregation of thallium adatoms adsorbed onto a graphene surface. Landauer-Büttiker and Kubo-Greenwood simulations are used to access both edge and bulk transport physics in disordered thallium-functionalized graphene systems of realistic sizes. Our findings not only quantify the detrimental effects of adatom clustering in the formation of the topological state, but also provide evidence for the emergence of spin accumulation at opposite sample edges driven by spin-dependent scattering induced by thallium islands, which eventually results in a minimum bulk conductivity ~4e2/h, insensitive to localization effects.S. R. acknowledges the Spanish Ministry of Economy and Competitiveness for funding (MAT2012-33911), the Severo Ochoa Program (MINECO SEV-2013-0295), and the Secretaria de Universidades e Investigación del Departamento de Economía y Conocimiento de la Generalidad de Cataluña. The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement No. 604391 Graphene Flagship.Peer Reviewe

Endotracheal Tube Dislodgment in a High Risk Pulmonary Hypertensive Patient due to Undiagnosed Tracheomegaly: A Case Report

Introduction Airway enlargement was first described histologically in 1872, but it was not clinically reported until 1932, when Dr. Mounier-Kuhn published his seminal radiographic studies.1 Since then, it is estimated that several hundred case reports have been published on congenital Mounier-Kuhn Syndrome (MKS), acquired tracheomegaly, and tracheobronchomegaly (TBM), yet only a few comprehensive literature reviews exist.2 Case This case report details an elective nasal procedure for a patient with a history of significant pulmonary hypertension ad COPD on 5L home O2 who had a symptomatic facial trauma. He was considered high risk secondary to his pulmonary disease, but he was considered medically optimized for surgery and had undergone a prior uncomplicated general anesthetic. An intraoperative endotracheal tube dislodgement necessitated emergency airway rescue with difficulty in re-establishing adequate ventilation resulting in the patient being brought to the ICU post-operatively. After a second endotracheal dislodgement shortly later, retrospective radiographic airway analysis revealed tracheal dimensions of 32 x 26mm, suggesting a previously undiagnosed tracheomegaly. Written consent and HIPAA authorization was obtained from the patient for the publication of this case report. Conclusion This case highlights the clinical importance for anesthesiologists to be aware of tracheobronchomegaly (TBM) despite limited provider experience with these patients and sparse reporting on the condition. It is underdiagnosed radiographically and may first present in the OR. TBM can manifest in many ways with potentially fatal complications thus it is vital for anesthesiologists to be able to recognize, troubleshoot, and potentially treat issues related to the disease

Testing the Generalized Second Law in 1+1 dimensional Conformal Vacua: An Argument for the Causal Horizon

The anomalous conformal transformation law of the generalized entropy is found for dilaton gravity coupled to a 1+1 conformal matter sector with central charges $c = \tilde{c}$. (When $c \ne \tilde{c}$ the generalized entropy is not invariant under local Lorentz boosts.) It is shown that a certain second null derivative of the entropy, $S_\text{gen}" + (6/c)(S_\text{out}')^2$, is primary, and therefore retains its sign under a general conformal transformation. Consequently all conformal vacua have increasing entropy on causal horizons. Alternative definitions of the horizon, including apparent or dynamical horizons, can have decreasing entropy in any dimension $D \ge 2$. This indicates that the generalized second law should be defined using the causal horizon.Comment: 19 pages, 2 figures, v2 significant additions clarifying sections 3, 5, and 6, v3 fixed typo in Eq. (35

Potential of Water Hyacinth Infestation on Lake Tana, Ethiopia: A Prediction Using a GIS-Based Multi-Criteria Technique

Water hyacinth is a well-known invasive weed in lakes across the world and harms the aquatic environment. Since 2011, the weed has invaded Lake Tana substantially posing a challenge to the ecosystem services of the lake. The major factors which affect the growth of the weed are phosphorus, nitrogen, temperature, pH, salinity, and lake depth. Understanding and investigating the hotspot areas is vital to predict the areas for proper planning of interventions. The main objective of this study is therefore to predict the hotspot areas of the water hyacinth over the surface of the lake using the geographical information system (GIS)-based multi-criteria evaluation (MCE) technique. The main parameters used in the multi-criteria analysis were total phosphorus (\u3e0.08 mg L−1), total nitrogen (\u3e1.1 mg L−1), temperature (\u3c26.2 °C), pH (\u3c8.6), salinity (\u3c0.011%), and depth (\u3c6 m). These parameters were collected from 143 sampling sites on the lake in August, December (2016), and March (2017). Fuzzy overlay spatial analysis was used to overlay the different parameters to obtain the final prediction map of water hyacinth infestation areas. The results indicated that 24,969 ha (8.1%), 21,568.7 ha (7.1%), and 24,036 ha (7.9%) of the lake are susceptible to invasion by the water hyacinth in August, December, and March, respectively. At the maximum historical lake level, 30,728.4 ha will be the potential susceptible area for water hyacinth growth and expansion at the end of the rainy season in August. According to the result of this study, the north and northeastern parts of the lake are highly susceptible for invasion. Hence, water hyacinth management and control plans shall mainly focus on the north and northeastern part of Lake Tana and upstream contributing watersheds