Electronic structure investigation of CeB6 by means of soft X-ray scattering

The electronic structure of the heavy fermion compound CeB6 is probed by resonant inelastic soft X-ray scattering using photon energies across the Ce 3d and 4d absorption edges. The hybridization between the localized 4f orbitals and the delocalized valence-band states is studied by identifying the different spectral contributions from inelastic Raman scattering and normal fluorescence. Pronounced energy-loss structures are observed below the elastic peak at both the 3d and 4d thresholds. The origin and character of the inelastic scattering structures are discussed in terms of charge-transfer excitations in connection to the dipole allowed transitions with 4f character. Calculations within the single impurity Anderson model with full multiplet effects are found to yield consistent spectral functions to the experimental data.Comment: 9 pages, 4 figures, 1 table, http://link.aps.org/doi/10.1103/PhysRevB.63.07510

Local fluctuations in quantum critical metals

We show that spatially local, yet low-energy, fluctuations can play an essential role in the physics of strongly correlated electron systems tuned to a quantum critical point. A detailed microscopic analysis of the Kondo lattice model is carried out within an extended dynamical mean-field approach. The correlation functions for the lattice model are calculated through a self-consistent Bose-Fermi Kondo problem, in which a local moment is coupled both to a fermionic bath and to a bosonic bath (a fluctuating magnetic field). A renormalization-group treatment of this impurity problem--perturbative in $\epsilon=1-\gamma$, where $\gamma$ is an exponent characterizing the spectrum of the bosonic bath--shows that competition between the two couplings can drive the local-moment fluctuations critical. As a result, two distinct types of quantum critical point emerge in the Kondo lattice, one being of the usual spin-density-wave type, the other ``locally critical.'' Near the locally critical point, the dynamical spin susceptibility exhibits $\omega/T$ scaling with a fractional exponent. While the spin-density-wave critical point is Gaussian, the locally critical point is an interacting fixed point at which long-wavelength and spatially local critical modes coexist. A Ginzburg-Landau description for the locally critical point is discussed. It is argued that these results are robust, that local criticality provides a natural description of the quantum critical behavior seen in a number of heavy-fermion metals, and that this picture may also be relevant to other strongly correlated metals.Comment: 20 pages, 12 figures; typos in figure 3 and in the main text corrected, version as publishe

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Predicting respiratory failure and outcome in pediatric Guillain-Barré syndrome

Background: Guillain-Barré syndrome (GBS) has a highly variable clinical course and outcome as indicated by the risk of developing respiratory failure and residual inability to walk. Prognostic models as Erasmus GBS Respiratory Insufficiency Score (EGRIS) developed in adult patients are inaccurate in children. Our aim was to determine the prognostic factors of respiratory failure and inability to walk in children with GBS and to develop a new clinical prognostic model for individual patients (EGRIS-Kids). Methods: A multicenter retrospective cohort study was performed using the data of children (younger than 18 years) fulfilling the diagnostic criteria for GBS from the NINDS. This study was performed in two independent cohorts from centers in Germany, Switzerland, Austria (N = 265, collected 1989–2002) and The Netherlands (N = 156, collected 1987–2016). The predicted main outcomes were occurrence of respiratory failure during the disease course and inability to walk independent at one year after diagnosis. Results: In the combined cohort of 421 children, 79 (19%) required mechanical ventilation and one patient died. The EGRIS-kids was developed including: age, cranial nerve involvement and GBS disability score at admission, resulting in a 9 point score predicting risks of respiratory failure ranging from 4 to 50% (AUC = 0.71). A lower GBS disability score at nadir was the strongest predictor of recovery to independent walking (at one month: OR 0.43 95%CI 0.25–0.74). Conclusions: EGRIS-Kids and GBS disability score at admission accurately predict the risk of respiratory failure and inability to walk respectively in children with GBS, as tools to personalize the monitoring and treatment