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In polytrauma patients, the impact of splenectomy is equivocal, ranging from negative to protective. We investigated the impact of splenectomy on immune responses in the 1st-hit polytrauma alone and on survival in the post-traumatic sepsis (2nd hit). Female BALB/c mice underwent polytrauma (1st hit) consisting of either a) TH: femur fracture, hemorrhagic shock or b) TSH: splenectomy, femur fracture, hemorrhagic shock. Additionally, the polytrauma hit was followed by cecal ligation and puncture (CLP) 48 h later and compared to CLP alone. Splenectomy improved the 28-day survival in secondary sepsis to 92% (from 62%), while TH lowered it to 46% (p < 0.05). The improved survival was concurrent with lower release of inflammatory cytokines (IL-6, CXCL-1, MCP-1) and increase of C5a post-CLP. In the polytrauma hit alone, TSH induced stronger neutrophilia (1.9 fold) and lymphocytosis (1.7 fold) when compared to TH mice. Moreover, TSH resulted in a 41% rise of regulatory T-cells and reduced the median fluorescence intensity of MHC-2 on monocytes by 55% within 48 h (p < 0.05). Conversely, leukocyte phagocytic capacity was significantly increased by 4-fold after TSH despite a similar M1/M2 macrophage profile in both groups. Summarizing, splenectomy provoked both immuno-suppressive and immuno-stimulatory responses but was life-saving in secondary sepsis. Additionally, the polytrauma components in 2-hit models should be tested for their effects on outcome; the presumed end-effect of the 1st hit solely based on the common immuno-inflammatory parameters could be misleading.

In polytrauma patients, the impact of splenectomy is equivocal, ranging from negative to protective. We investigated the impact of splenectomy on immune responses in the 1st-hit polytrauma alone and on survival in the post-traumatic sepsis (2nd hit). Female BALB/c mice underwent polytrauma (1st hit) consisting of either a) TH: femur fracture, hemorrhagic shock or b) TSH: splenectomy, femur fracture, hemorrhagic shock. Additionally, the polytrauma hit was followed by cecal ligation and puncture (CLP) 48 h later and compared to CLP alone. Splenectomy improved the 28-day survival in secondary sepsis to 92% (from 62%), while TH lowered it to 46% (p < 0.05). The improved survival was concurrent with lower release of inflammatory cytokines (IL-6, CXCL-1, MCP-1) and increase of C5a post-CLP. In the polytrauma hit alone, TSH induced stronger neutrophilia (1.9 fold) and lymphocytosis (1.7 fold) when compared to TH mice. Moreover, TSH resulted in a 41% rise of regulatory T-cells and reduced the median fluorescence intensity of MHC-2 on monocytes by 55% within 48 h (p < 0.05). Conversely, leukocyte phagocytic capacity was significantly increased by 4-fold after TSH despite a similar M1/M2 macrophage profile in both groups. Summarizing, splenectomy provoked both immuno-suppressive and immuno-stimulatory responses but was life-saving in secondary sepsis. Additionally, the polytrauma components in 2-hit models should be tested for their effects on outcome; the presumed end-effect of the 1st hit solely based on the common immuno-inflammatory parameters could be misleading.

Over the last years a lot of theoretical and experimental efforts have been made to find states with broken time reversal symmetry (BTRS) in multi-band superconductors. In particular, it was theoretically proposed that in the Ba1−xKxFe2As2 system either an s + is or an s + id BTRS state may exist at high doping levels in a narrow region of the phase diagram. Here we report the observation of an enhanced zero field muon spin relaxation rate below the superconducting transition temperature for a high quality crystalline sample with x ≈ 0.73. This indicates that indeed the time reversal symmetry is broken in superconducting Ba1−xKxFe2As2 at this doping level.

A quantum critical point (QCP) is currently being conjectured for the BaFe2(As1−xPx)2 system at the critical value xc ≈ 0.3. In the proximity of a QCP, all thermodynamic and transport properties are expected to scale with a single characteristic energy, given by the quantum fluctuations. Such a universal behavior has not, however, been found in the superconducting upper critical field Hc2. Here we report Hc2 data for epitaxial thin films extracted from the electrical resistance measured in very high magnetic fields up to 67 Tesla. Using a multi-band analysis we find that Hc2 is sensitive to the QCP, implying a significant charge carrier effective mass enhancement at the doping-induced QCP that is essentially band-dependent. Our results point to two qualitatively different groups of electrons in BaFe2(As1−xPx)2. The first one (possibly associated to hot spots or whole Fermi sheets) has a strong mass enhancement at the QCP, and the second one is insensitive to the QCP. The observed duality could also be present in many other quantum critical systems.

We report an experimental and theoretical study of the low temperature 7Li nuclear magnetic resonance (NMR) spectra of oriented powder samples of γ-Li2ZrCuO4 (≡Li2CuZrO4) which comprises interpenetrating sublattices of frustrated quasi-one- dimensional s=1/2 quantum Heisenberg magnetic Cu2+ chains and frustrated quantum Ising electric sublattice of LiI ions. Incommensurate spin order occurring in this compound at TNâ6 K gives rise to a drastic change of the 7Li NMR spectrum. We show that the peculiar NMR line shapes are determined by the specific, sample dependent, distribution of the LiI ions in the glassy ordered electric sublattice. The analysis of the NMR data in the framework of a spin-spiral model gives evidence for a remarkable interaction between magnetic and electric degrees of freedom in γ-Li2ZrCuO4, which suggests it as a promising model compound for fundamental studies of complex magnetoelectric phenomena and illustrates well their richness. © 2013 American Physical Society.

We present a comprehensive macroscopic thermodynamic study of the quasi-one-dimensional (1D) s =½ frustrated spin-chain system linarite. Susceptibility, magnetization, specific heat, magnetocaloric effect, magnetostriction, and thermal-expansion measurements were performed to characterize the magnetic phase diagram. In particular, for magnetic fields along the b axis five different magnetic regions have been detected, some of them exhibiting short-range-order effects. The experimental magnetic entropy and magnetization are compared to a theoretical modeling of these quantities using density matrix renormalization group (DMRG) and transfer matrix renormalization group (TMRG) approaches.Within the framework of a purely 1D isotropic model Hamiltonian, only a qualitative agreement between theory and the experimental data can be achieved. Instead, it is demonstrated that a significant symmetric anisotropic exchange of about 10% is necessary to account for the basic experimental observations, including the three-dimensional (3D) saturation field, and which in turn might stabilize a triatic (three-magnon) multipolar phase.

We present de Haas-van Alphen (dHvA) measurements in the normal and in the superconducting state of LuNi2B2C. Inside the superconducting state, we observe quantum oscillations of a spherical Fermi-surface sheet in all crystallographic directions. Apart from the field region close to the phase transition where a strong peak effect hampers the analysis of the dHvA signal, the additional damping of the quantum oscillations inside the superconducting state is much smaller than expected from theory. For the magnetic field aligned along the [100] direction, three different dHvA frequencies are visible in the superconducting state. In particular, the orbit related to a cushion-like Fermi surface does not show any additional damping at and below the upper critical field contrary to theoretical expectations of simple effective one-band theories. Consequently, the superconducting gap on this Fermi-surface sheet can only evolve at lower fields than the observed bulk critical field, Bc2 ≈ 8 T, which clearly points to a Fermi-surface-sheet-dependent gap opening in LuNi2B2C.

We present an experimental and theoretical study of the quasi-onedimensional S = 1/2 Heisenberg magnet linarite PbCuSO4(OH)2, with competing ferromagnetic nearest-neighbor and antiferromagnetic nextnearest- neighbor exchange interactions. It includes magnetization and NMR studies as well as theoretical simulations for the determination of the leading exchange couplings, which are about an order of magnitude higher as determined previously [1]. Furthermore, a manifold of field-induced phases are probed, from which we draw a preliminary phase diagram. Notably, spin-lattice relaxation investigations indicate that linarite might undergo a magnetic quadrupolar spin liquid phase transition as recently predicted for such materials.

A thermodynamic method to extract the interchain coupling (IC) of spatially anisotropic 2D or 3D spin-1/2 systems from their empirical saturation field Hs(T = 0) is proposed. Using modern theoretical methods we study how Hs is affected by an antiferromagnetic (AFM) IC between frustrated chains described in the J1-J2-spin model with ferromagnetic 1st and AFM 2nd neighbor in-chain exchange. A complex 3D-phase diagram has been found. For Li2CuO2 and Ca2Y2Cu5O10, we show that Hs is solely determined by the IC and predict Hs \apprx 61 T for the latter. With Hs \approx 55 T from magnetization data one reads out a weak IC for Li2CuO2 close to that obtained from inelastic neutron scattering.

We present an experimental and theoretical study of the quasi-onedimensional S = 1/2 Heisenberg magnet linarite PbCuSO4(OH)2, with competing ferromagnetic nearest-neighbor and antiferromagnetic nextnearest- neighbor exchange interactions. It includes magnetization and NMR studies as well as theoretical simulations for the determination of the leading exchange couplings, which are about an order of magnitude higher as determined previously [1]. Furthermore, a manifold of field-induced phases are probed, from which we draw a preliminary phase diagram. Notably, spin-lattice relaxation investigations indicate that linarite might undergo a magnetic quadrupolar spin liquid phase transition as recently predicted for such materials.

By measuring 7Li nuclear magnetic resonance, Cu2+ electron spin resonance and a complex dielectric constant in the frustrated spin-1/2 chain compound γ-Li2ZrCuO4 we find that the electric sublattice of mobile Li+ ions orders glass-like at T g ∼ 100 K. This yields the emergence of non-equivalent spin sites in the spin-1/2 CuO2 chains. We suggest that such a remarkable interplay between electrical and spin degrees of freedom may influence the properties of the spiral spin state in Li2ZrCuO4 which develops in this material at low temperatures. © 2010 IOP Publishing Ltd.

We report resistivity and upper critical field Bc2 (T) data for disordered (As-deficient) LaO0.9F0.1 FeAs1-delta in a wide temperature and high field range up to 60 T. These samples exhibit a slightly enhanced superconducting transition at Tc = 28.5 K and a significantly enlarged slope dBc2/dT = -5.4 T/K near Tc which contrasts with a flattening of Bc2(T) starting near 23 K above 30 T. The latter evidences Pauli-limiting behaviour (PLB) with Bc2(0) approximate to 63 T. We compare our results with Bc2(T)-data from the literature for clean and disordered samples. Whereas clean samples show almost no PLB for fields below 60-70 T, the hitherto unexplained pronounced flattening of Bc2(T) for applied fields H vertical bar ab observed for several disordered closely related systems is interpreted also as a manifestation of PLB. Consequences are discussed in terms of disorder effects within the frames of (un)conventional superconductivity, respectively.

We present a short critical overview of different microscopic models for nonrelativistic and relativistic magnetoelectric coupling including the so-called "spin current scenario", ab-initio calculations, and several recent microscopic approaches to a spin-dependent electric polarization in 3d oxides. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2009.

Puzzling multiferroic behavior observed recently in spin-1/2 one-dimensional chain cuprate LiCu2 O2 with edge-shared arrangement of CuO4 plaquettes and incommensurate spiral spin ordering is consistently explained to be a result of the nonrelativistic exchange-induced electric polarization on the Cu2+ centers substituting for the positions native for the Cu1+ ions. These substituent centers are proven to be an effective probe of the spin incommensurability and magnetic field effects. © 2009 The American Physical Society.

We present de Haas–van Alphen measurements of the nonmagnetic borocarbide superconductor LuNi2B2C. The electronic band structure is extracted from the magnetic quantum oscillations in the normal state. In accordance with previous investigations we find a complex band structure with different open and closed Fermi-surface sheets. From the temperature dependence of the oscillations amplitude the effective mass of the single bands can be determined. Due to many-body interactions we observe enhancements of the effective masses compared to the results by full-potential-density-functional calculations. Therefore, we are able to determine the angular dependence of the interaction strength for the different bands separately.

The recently observed multiferroic behavior in the s=1/2 chain cuprate LiVCuO4 (≡LiCuVO4) with edge-shared CuO4 plaquettes and helical spin ordering does not agree with the existing theories such as a spin-current scenario. We argue that the effect can be consistently explained, if the exchange-induced electric polarization on the out-of-chain Cu2+ centers substituting for Li ions in LiVCuO4 is taken into account. These substituent centers are proved to be an effective probe of the spin incommensurability and the magnetic-field effects. © Europhysics Letters Association.

The incommensurate (IC) spin ordering in quasi-one-dimensional edge-shared cuprate Na Cu2 O2 has been studied by Na23 nuclear magnetic resonance spectroscopy in an external magnetic field near 6 T applied along the main crystallographic axes. The NMR line shape evolution above and below TN ≈12 K yields a clear signature of an IC static modulation of the local magnetic field consistent with a Cu2+ spin spiral polarized in the bc plane rather than in the ab plane, as reported from earlier neutron diffraction data. © 2008 The American Physical Society.

We present de Haas{van Alphen measurements of the nonmagnetic borocarbide superconductors LuNi2B2C and YNi2B2C. The measurements have been performed by use of the torque method in high magnetic fields up to 32 T and at temperatures down to 50 mK. The Fermi-surface cross sections are extracted from the magnetic quantum oscillations in the normal state. In accordance with previous investigations we find a complex band structure with dfferent open and closed Fermi-surface sheets. From the temperature dependence of the oscillations amplitude the effective mass of the single bands can be determined. We observe sizeable and anisotropic enhancements of the effective masses compared to full-potential-localorbital calculations which is due to anisotropic many-body interactions.

For a systematic investigation of the heat- and charge-transport properties of YNi2B2C and HoNi2B2C, single-crystal measurements of the electrical resistivity, the thermal conductivity, and the thermoelectric power were performed on the same samples. For HoNi2B2C, a local maximum of the Lorenz number at 20 K is evidently connected with the occurrence of magnetic fluctuations well above the ordering temperature. For the in-plane thermal conductivity, a kink near the superconducting transition was observed, consistent with an anisotropic gap or a multiband description. For both investigated borocarbides, the electrical resistance is isotropic. In contrast, the thermal conductivity shows a pronounced anisotropy. The thermoelectric power exhibits a minor anisotropy and can be well described by electron-diffusion and phonon-drag contributions over a wide temperature range. Based on an analysis of full-potential local-orbital calculations, a strong influence of the boron z position on the thermoelectric power has been revealed.

We present de Haas{van Alphen measurements of the nonmagnetic borocarbide superconductors LuNi2B2C and YNi2B2C. The measurements have been performed by use of the torque method in high magnetic fields up to 32 T and at temperatures down to 50 mK. The Fermi-surface cross sections are extracted from the magnetic quantum oscillations in the normal state. In accordance with previous investigations we find a complex band structure with dfferent open and closed Fermi-surface sheets. From the temperature dependence of the oscillations amplitude the effective mass of the single bands can be determined. We observe sizeable and anisotropic enhancements of the effective masses compared to full-potential-localorbital calculations which is due to anisotropic many-body interactions.

We report on Li nuclear magnetic resonance measurements of the spin-chain compound LiCu2O2 in the paramagnetic and magnetically ordered states. Below 24 K the NMR line shape shows a clear signature of incommensurate (IC) static modulation of the local magnetic field consistent with an IC spiral modulation of the magnetic moments. Li NMR reveals strong phason-like dynamical fluctuations extending well below 24 K. A series of phase transitions at 24.2, 22.5, and 9 K is observed. Local density approximation based calculations of exchange integrals reveal a large in-chain frustration leading to a magnetical spiral.