Strong Spin Dependence of Correlation Effects in Ni Due to Stoner Excitations

Using high-resolution angle-resolved photoemission, we observe a strong spin-dependent renormalization and lifetime broadening of the quasiparticle excitations in the electronic band structure of Ni(111) in an energy window of ∼0.3  eV below the Fermi level. We derive a quantitative result for the spin-dependent lifetime broadening by comparing the scattering rates of majority and minority d states, and further show that spin-dependent electron correlations are instead negligible for sp states. From our analysis we experimentally determine the effective on-site Coulomb interaction U caused by Stoner-like interband transitions between majority and minority d states. The present results demonstrate the remarkable impact of spin-dependent electron correlation effects originating from single-particle excitations in a prototypical 3d transition metal, paving the way for further refinement of current many-body theoretical approaches.

Pyrene Molecular Orbital Shuffle-Controlling Excited State and Redox Properties by Changing the Nature of the Frontier Orbitals

We show that by judicious choice of substituents at the 2- and 7-positions of pyrene, the frontier orbital order of pyrene can be modified, giving enhanced control over the nature and properties of the photoexcited states and the redox potentials. Specifically, we introduced a julolidine-like moiety and Bmes₂ (mes=2,4,6-Me₃ C₆ H₂ ) as very strong donor (D) and acceptor (A), respectively, giving 2,7-D-π-D- and unsymmetric 2,7-D-π-A-pyrene derivatives, in which the donor destabilizes the HOMO-1 and the acceptor stabilizes the LUMO+1 of the pyrene core. Consequently, for 2,7-substituted pyrene derivatives, unusual properties are obtained. For example, very large bathochromic shifts were observed for all of our compounds, and unprecedented green light emission occurs for the D/D system. In addition, very high radiative rate constants in solution and in the solid state were recorded for the D-π-D- and D-π-A-substituted compounds. All compounds show reversible one-electron oxidations, and Jul₂ Pyr exhibits a second oxidation, with the largest potential splitting (ΔE=440 mV) thus far reported for 2,7-substituted pyrenes. Spectroelectrochemical measurements confirm an unexpectedly strong coupling between the 2,7-substituents in our pyrene derivatives.

Unusual Dirac Fermions on the Surface of a Noncentrosymmetric α-BiPd Superconductor

Combining multiple emergent correlated properties such as superconductivity and magnetism within the topological matrix can have exceptional consequences in garnering new and exotic physics. Here, we study the topological surface states from a noncentrosymmetric α-BiPd superconductor by employing angle-resolved photoemission spectroscopy and first-principles calculations. We observe that the Dirac surface states of this system have several interesting and unusual properties, compared to other topological surface states. The surface state is strongly anisotropic and the in-plane Fermi velocity varies rigorously on rotating the crystal about the y axis. Moreover, it acquires an unusual band gap as a function of k_{y}, possibly due to hybridization with bulk bands, detected upon varying the excitation energy. The coexistence of all the functional properties in addition to the unusual surface state characteristics make this an interesting material.

[Internal Hernia Following Laparoscopic Roux-Y Gastric Bypass - a Challenge not only for the General Surgeon]

The frequency of bariatric operations has increased in Germany. Primary operations are usually performed at specialised centres. However, late complications may develop months or even years after the operation, and every general and visceral surgeon may be confronted with them, regardless of the size and specialisation of their clinics. The laparoscopic Roux-Y gastric bypass is the most frequently performed bariatric operation worldwide. During this procedure, the alimentary loop is lifted up in front of the colon to form a pouch, which creates a mesenteric space, also called the Petersen space, dorsal to the alimentary loop and below the transverse colon. Both here and around the mesenteric space of the Roux anastomosis, an internal hernia may develop, i.e. the small intestine can twist on its own axis. Abdominal discomfort due to intestinal obstruction is unspecific, but very pronounced. Clinically, patients either present with an acute abdomen or with intermittent unspecific abdominal pain with nausea, and rarely also with vomiting. Clinical examinations and lab chemistry tests usually do not reveal any indicative findings. In cases of doubt, therefore, contrast-enhanced computed tomography of the abdomen is the diagnostic imaging procedure of choice. A diagnostic laparoscopy should be performed in every patient with a clinical suspicion of an internal hernia, even if the CT scan is unremarkable. This should be done by a surgeon who is well-versed in laparoscopy and experienced in bariatric surgery, since classification of the intestinal loops is very difficult without knowledge of the hernial orifices. First, an inframesocolic view is obtained with the transverse colon being lifted. From here, the open Petersen space offers a direct view of the ligament of Treitz from the right side. If small intestine is found to the right of the ligament, there is a Petersen hernia. After the inframesocolic view, the gastroenterostomy should be located and the alimentary loop should be followed in distal direction towards the jejunojejunostomy, where the second possible space may be found. Once both spaces have been located and a hernia has been reduced as appropriate, the spaces should be closed with non-absorbable suture.

Observation of a universal donor-dependent vibrational mode in graphene

Electron-phonon coupling and the emergence of superconductivity in intercalated graphite have been studied extensively. Yet, phonon-mediated superconductivity has never been observed in the 2D equivalent of these materials, doped monolayer graphene. Here we perform angle-resolved photoemission spectroscopy to try to find an electron donor for graphene that is capable of inducing strong electron-phonon coupling and superconductivity. We examine the electron donor species Cs, Rb, K, Na, Li, Ca and for each we determine the full electronic band structure, the Eliashberg function and the superconducting critical temperature Tc from the spectral function. An unexpected low-energy peak appears for all dopants with an energy and intensity that depend on the dopant atom. We show that this peak is the result of a dopant-related vibration. The low energy and high intensity of this peak are crucially important for achieving superconductivity, with Ca being the most promising candidate for realizing superconductivity in graphene.

High-energy anomaly in the angle-resolved photoemission spectra of Nd(2-x)Ce(x)CuO₄: evidence for a matrix element effect

We use polarization-dependent angle-resolved photoemission spectroscopy (ARPES) to study the high-energy anomaly (HEA) in the dispersion of Nd(2-x)Ce(x)CuO₄, x=0.123. We find that at particular photon energies the anomalous, waterfall-like dispersion gives way to a broad, continuous band. This suggests that the HEA is a matrix element effect: it arises due to a suppression of the intensity of the broadened quasiparticle band in a narrow momentum range. We confirm this interpretation experimentally, by showing that the HEA appears when the matrix element is suppressed deliberately by changing the light polarization. Calculations of the matrix element using atomic wave functions and simulation of the ARPES intensity with one-step model calculations provide further evidence for this scenario. The possibility to detect the full quasiparticle dispersion further allows us to extract the high-energy self-energy function near the center and at the edge of the Brillouin zone.

[Off-label use of recombinant factor VII (rFVIIa) in teaching hospitals in Paris in 2010]

INTRODUCTION

Recombinant activated factor VII (rFVIIa) (Novoseven(®)) was initially developed as a substitutive treatment in haemophiliacs but has then been used in situations of major haemorrhage in non-haemophiliacs (off-label use). The goal of the present study was to assess the practice patterns when rFVIIa is used in off-label indications in major teaching hospitals of Paris in 2010.

METHODS

We retrospectively identified files of patients in whom rFVIIa had been used. Physicians in charge of these patients (or the most proxy physician available) were contacted and files analysed with one of the authors. Quality of rFVIIa used in these off-label situations was determined based on either French or European guidelines or the available literature when no guidelines could be found. Three categories were defined for indication, dosage, timing, associated biological factors and overall use: adequate, acceptable (mainly adequate but lacking some characteristics of an "ideal" prescription) and inadequate (lacking most of the necessary characteristics of an "ideal" prescription).

RESULTS

Among 59 patients who had an off-label prescription of rFVIIa, 49 prescriptions could be analysed. Indication for use and timing of administration were adequate in 100% of multiple trauma cases and 83% of obstetrical cases. Biological criteria associated with an improved efficacy were found in two thirds of prescriptions analysed. Overall, prescriptions were adequate or acceptable in 82% of cases.

CONCLUSION

In the vast majority of patients who received rFVIIa for off-label indications in teaching hospitals of the Paris area in 2010, prescriptions were in line with recommendations.

Resonant elastic soft x-ray scattering

Resonant (elastic) soft x-ray scattering (RSXS) offers a unique element, site and valence specific probe to study spatial modulations of charge, spin and orbital degrees of freedom in solids on the nanoscopic length scale. It is not only used to investigate single-crystalline materials. This method also enables one to examine electronic ordering phenomena in thin films and to zoom into electronic properties emerging at buried interfaces in artificial heterostructures. During the last 20 years, this technique, which combines x-ray scattering with x-ray absorption spectroscopy, has developed into a powerful probe to study electronic ordering phenomena in complex materials and furthermore delivers important information on the electronic structure of condensed matter. This review provides an introduction to the technique, covers the progress in experimental equipment, and gives a survey on recent RSXS studies of ordering in correlated electron systems and at interfaces.

Coherent excitations and electron-phonon coupling in Ba/EuFe2As2 compounds investigated by femtosecond time- and angle-resolved photoemission spectroscopy

We employed femtosecond time- and angle-resolved photoelectron spectroscopy to analyze the response of the electronic structure of the 122 Fe-pnictide parent compounds Ba/EuFe(2)As(2) and optimally doped BaFe(1.85)Co(0.15)As(2) near the Γ point to optical excitation by an infrared femtosecond laser pulse. We identify pronounced changes of the electron population within several 100 meV above and below the Fermi level, which we explain as a combination of (i) coherent lattice vibrations, (ii) a hot electron and hole distribution, and (iii) transient modifications of the chemical potential. The responses of the three different materials are very similar. In the coherent response we identify three modes at 5.6, 3.3, and 2.6 THz. While the highest frequency mode is safely assigned to the A(1g) mode, the other two modes require a discussion in comparison to the literature. Employing a transient three temperature model we deduce from the transient evolution of the electron distribution a rather weak, momentum-averaged electron-phonon coupling quantified by values for λ<ω(2)> between 30 and 70 meV(2). The chemical potential is found to present pronounced transient changes reaching a maximum of 15 meV about 0.6 ps after optical excitation and is modulated by the coherent phonons. This change in the chemical potential is particularly strong in a multiband system like the 122 Fe-pnictide compounds investigated here due to the pronounced variation of the electron density of states close to the equilibrium chemical potential.

Medically refractory neurosarcoidosis treated with infliximab

Neurosarcoidosis can worsen despite standard immunosuppressive therapy, a situation for which there is no established medical management. We present three cases of medically refractory neurosarcoidosis treated with infliximab. All three patients showed a clinical response to this treatment and side effects were limited. A summary of reported cases of neurosarcoidosis treated with infliximab is included. This case series supports a role for infliximab in the treatment of patients with medically refractory neurosarcoidosis.

Ultrafast momentum-dependent response of electrons in antiferromagnetic EuFe2As2 driven by optical excitation

Employing the momentum sensitivity of time- and angle-resolved photoemission spectroscopy we demonstrate the analysis of ultrafast single- and many-particle dynamics in antiferromagnetic EuFe(2)As(2). Their separation is based on a temperature-dependent difference of photoexcited hole and electron relaxation times probing the single-particle band and the spin density wave gap, respectively. Reformation of the magnetic order occurs at 800 fs, which is 4 times slower compared to electron-phonon equilibration due to a smaller spin-dependent relaxation phase space.

Large tunable Rashba spin splitting of a two-dimensional electron gas in Bi2Se3

We report a Rashba spin splitting of a two-dimensional electron gas in the topological insulator Bi(2)Se(3) from angle-resolved photoemission spectroscopy. We further demonstrate its electrostatic control, and show that spin splittings can be achieved which are at least an order-of-magnitude larger than in other semiconductors. Together these results show promise for the miniaturization of spintronic devices to the nanoscale and their operation at room temperature.

Experimental state tomography of itinerant single microwave photons

A wide range of experiments studying microwave photons localized in superconducting cavities have made important contributions to our understanding of the quantum properties of radiation. Propagating microwave photons, however, have so far been studied much less intensely. Here we present measurements in which we reconstruct the quantum state of itinerant single photon Fock states and their superposition with the vacuum by analyzing moments of the measured amplitude distribution up to fourth order. Using linear amplifiers and quadrature amplitude detectors, we have developed efficient methods to separate the detected single photon signal from the noise added by the amplifier. From our measurement data we have also reconstructed the corresponding Wigner function.