(pi, pi) electronic order in iron arsenide superconductors.

The distribution of valence electrons in metals usually follows the symmetry of the underlying ionic lattice. Modulations of this distribution often occur when those electrons are not stable with respect to a new electronic order, such as spin or charge density waves. Electron density waves have been observed in many families of superconductors, and are often considered to be essential for superconductivity to exist. Recent measurements seem to show that the properties of the iron pnictides are in good agreement with band structure calculations that do not include additional ordering, implying no relation between density waves and superconductivity in these materials. Here we report that the electronic structure of Ba(1-x)K(x)Fe(2)As(2) is in sharp disagreement with those band structure calculations, and instead reveals a reconstruction characterized by a (pi, pi) wavevector. This electronic order coexists with superconductivity and persists up to room temperature (300 K).

Injurious pecking in organic turkey fattening-effects of husbandry and feeding on injuries and plumage damage of a slow- (Auburn) and a fast-growing (B.U.T.6) genotype.

Injuries and plumage damage (PD) are important indicators of welfare. First priority in turkey fattening is to reduce injurious pecking, which includes aggressive pecking (agonistic behavior) and additionally severe feather pecking (SFP) and cannibalism with their multifactorial reasons. Still, there are few studies available evaluating different genotypes for their welfare status under organic conditions. The aim of this study was to investigate the effects of genotype and husbandry with 100% organic feeding (2 variants with different riboflavin content: V1 and V2) on injuries and PD. During rearing nonbeaktrimmed male turkeys of a slow- (Auburn, n = 256) and fast-growing (B.U.T.6, n = 128) genotype were kept in 2 indoor housing systems (without environmental enrichment (EE) = H1-, n = 144 and with EE = H2+, n = 240). During fattening 13 animals per pen of H2+ were relocated to a free-range system (H3 MS, n = 104). EE included pecking stones, elevated seating platforms and silage feeding. The study included five 4-wk feeding phases. At the end of each phase, injuries and PD were scored to assess animal welfare. Injury scores ranged from 0 (=no damage) to 3 (=severe damage) and PD from 0 to 4. Injurious pecking was observed from the 8th week onward (injuries: 16.5% and PD: 31.4%). Binary logistic regression models showed that both indicators were affected by genotype (each P < 0.001), husbandry (each P < 0.001), feeding (injuries P = 0.004; PD P = 0.003), and age (each P < 0.001). Auburn showed less injuries and PD than B.U.T.6. H1- had the fewest injuries and PD for Auburn animals compared to H2+ or H3 MS. In summary, the use of alternative genotypes (Auburn) in organic fattening improved welfare, but keeping them in free-range systems or in husbandry with EE, does not lead to a reduction of injurious pecking. Therefore, further studies are needed with more and changing enrichment materials, further management measures, changes in housing structure, and even more intensive animal care.

Evidence of a precursor superconducting phase at temperatures as high as 180 K in RBa2Cu3O(7-δ) (R=Y, Gd, Eu) superconducting crystals from infrared spectroscopy.

We show that a multilayer analysis of the infrared c-axis response of RBa2Cu3O(7-δ) (R=Y, Gd, Eu) provides important new information about the anomalous normal-state properties of underdoped cuprate high temperature superconductors. In addition to competing correlations which give rise to a pseudogap that depletes the low-energy electronic states below T*≫T(c), it enables us to identify the onset of a precursor superconducting state below T(ons)>T(c). We map out the doping phase diagram of T(ons) which reaches a maximum of 180 K at strong underdoping and present magnetic field dependent data which confirm our conclusions.

Incommensurate magnetic order and dynamics induced by spinless impurities in YBa(2)Cu(3)O(6.6).

We report an inelastic-neutron-scattering and muon-spin-relaxation study of the effect of 2% spinless (Zn) impurities on the magnetic order and dynamics of YBa(2)Cu(3)O(6.6), an underdoped high-temperature superconductor that exhibits a prominent spin pseudogap in its normal state. Zn substitution induces static magnetic order at low temperatures and triggers a large-scale spectral-weight redistribution from the magnetic resonant mode at 38 meV into uniaxial, incommensurate spin excitations with energies well below the spin pseudogap. These observations indicate a competition between incommensurate magnetic order and superconductivity close to a quantum critical point. Comparison to prior data on La(2-x)Sr(x)CuO(4) suggests that this behavior is universal for the layered copper oxides and analogous to impurity-induced magnetic order in one-dimensional quantum magnets.

Magnetic-field-enhanced incommensurate magnetic order in the underdoped high-temperature superconductor YBa2Cu3O6.45.

We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift in the magnetic-excitation spectrum. A reconstruction of the Fermi surface driven by the field-enhanced magnetic superstructure may thus be responsible for the unusual Fermi surface topology revealed by recent quantum-oscillation experiments.

Electronic phase separation in the slightly underdoped iron pnictide superconductor Ba1-xKxFe2As2.

Here we present a combined study of the slightly underdoped novel pnictide superconductor Ba1-xKxFe2As2 by means of x-ray powder diffraction, neutron scattering, muon-spin rotation (microSR), and magnetic force microscopy (MFM). Static antiferromagnetic order sets in below T{m} approximately 70 K as inferred from the neutron scattering and zero-field-microSR data. Transverse-field microSR below Tc shows a coexistence of magnetically ordered and nonmagnetic states, which is also confirmed by MFM imaging. We explain such coexistence by electronic phase separation into antiferromagnetic and superconducting- or normal-state regions on a lateral scale of several tens of nanometers. Our findings indicate that such mesoscopic phase separation can be considered an intrinsic property of some iron pnictide superconductors.

Electronic liquid crystal state in the high-temperature superconductor YBa2Cu3O6.45.

Electronic phases with symmetry properties matching those of conventional liquid crystals have recently been discovered in transport experiments on semiconductor heterostructures and metal oxides at millikelvin temperatures. We report the spontaneous onset of a one-dimensional, incommensurate modulation of the spin system in the high-transition-temperature superconductor YBa2Cu3O6.45 upon cooling below approximately 150 kelvin, whereas static magnetic order is absent above 2 kelvin. The evolution of this modulation with temperature and doping parallels that of the in-plane anisotropy of the resistivity, indicating an electronic nematic phase that is stable over a wide temperature range. The results suggest that soft spin fluctuations are a microscopic route toward electronic liquid crystals and that nematic order can coexist with high-temperature superconductivity in underdoped cuprates.

Effects of semisynthetic diets on xenobiotic metabolizing enzyme activity and morphology of small intestinal mucosa in humans.

We studied the effects of semisynthetic (elemental) diets on the function and morphology of the human small intestine. The enzymatic capacity of the intestinal mucosa to metabolize lipophilic xenobiotics was investigated using jejunal biopsy specimens from 15 normal subjects who were on an isocaloric, nutritionally balanced semisynthetic diet for 7 days and thereafter on a normal home diet. Each subject underwent biopsy twice: on day 7 of semisynthetic diet and again on home diet 2-6 wk later. The jejunal mucosal tissue was examined by histologic morphometry and stereomicroscopy. Moreover, 25-50 mg of the biopsy material was homogenized and the following enzyme activities were determined in 20,000 g supernatant: for cytochrome P450-dependent monooxygenase activity with 7-ethoxycoumarin O-deethylase (EOD) and with nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome c reductase and for conjugation activity with 1-naphthol glucuronyltransferase (NGT). The NGT and reductase activities were unchanged by the dietary alterations. However, the EOD activity was significantly depressed on semisynthetic diet and rose to control range on home diet (from 5.3 +/- 2.5 to 12.4 +/- 8.6 pmol/min X 10 mg wet wt). Male subjects had significantly higher EOD activities than female subjects on semisynthetic diet (6.6 +/- 2.3 vs. 3.2 +/- 0.9) as well as on home diet (16.3 +/- 9.0 vs. 6.4 +/- 3.0). Semisynthetic diet also reduced the jejunal villous height significantly when compared with home diet (408 +/- 49 vs. 373 +/- 44 micron). Therefore, on semisynthetic diet the toxicity of dietary xenobiotics that are inactivated by the intestinal mucosa may be increased.