Emerging magnetism and electronic phase separation at titanate interfaces

The emergence of magnetism in otherwise nonmagnetic compounds and its underlying mechanisms have become the subject of intense research. Here we demonstrate that the nonmagnetic oxygen vacancies are responsible for an unconventional magnetic state common for titanate interfaces and surfaces. Using an effective multiorbital modelling, we find that the presence of localized vacancies leads to an interplay of ferromagnetic order in the itinerant t2g band and complex magnetic oscillations in the orbitally-reconstructed eg-band, which can be tuned by gate fields at oxide interfaces. The magnetic phase diagram includes highly fragmented regions of stable and phase-separated magnetic states forming beyond nonzero critical defect concentrations.Comment: 5 pages, 4 figure

Electrostatic interface tuning in correlated superconducting heterostructures

An electrostatic field, which is applied to a gated high-temperature superconducting (HTSC) film, is believed to affect the film similar to charge doping. Analyzing the pairing in terms of a t-J model, we show that a coupling to electric dipoles and phonons at the interface of film and dielectric gate localizes the injected charge and leads to a superconductor-insulator transition. This results in a dramatic modification of the doping dependent phase diagram close to and above the optimal doping which is expected to shed light on recent electric field-effect experiments with HTSC cuprates.Comment: 6 pages, 6 figures, to appear in Physical Review

Changing pattern of primary hyperoxaluria in Switzerland

Background The clinical course of primary hyperoxaluria (PH) is greatly variable and diagnosis is often delayed. Little is known about the overall occurrence and current prognosis. Methods We evaluated all known patients with PH residing and observed in Switzerland during the last 15 years with the help of a survey among Swiss nephrologists. Results Of the 25 patients observed between 7/79 and 6/94 in Switzerland, 18 were alive in 1994—14 on conservative therapy and four on renal replacement therapy (RRT). Twenty-two patients had PH type 1; the exact type was not determined in three. The estimated prevalence of PH (type 1) is 2 per million population; the minimal incidence is 1 per 100000 live births. Diagnosis was delayed by 8 years (median) except in infants. Five patients were pyridoxine sensitive. According to life table analysis, 20% of patients were in end-stage renal failure (ESRF) and 10% had died by the age of 15 years, and 50% were in ESRF and 20% dead at 25 years. Prognosis has improved: Five of 13 patients died during the first half of the observation period as opposed to two of 20 in the second part. Conclusions Overall prognosis appears better than hitherto believed considering the large clinical spectrum of PH. Greater awareness of PH is needed to improve further long-term prognosi

A 300 Years Record of Polycyclic Aromatic Hydrocarbons in Lake Botanisk, Copenhagen: A Historical Reconstruction of Combustion Processes in a Scandinavian Urban Lake

Lake Botanisk, a small isolated body of water in Copenhagen, Denmark, has remained relatively undisturbed for four centuries, making its sediments an excellent historical archive of past deposition rates of atmospheric contaminants. The concentrations and composition of polycyclic aromatic hydrocarbons (PAHs) measured in a sediment core of Lake Botanisk assisted in reconstructing the historical combustion activities for that region. Source diagnostic ratios indicate that PAHs were primarily derived from pyrogenic rather than petrogenic sources throughout the entire core. Marked increases in PAH concentrations during the pre-industrial era (1980s). In spite of significant decreases in PAH concentrations since the early-20th century peak, levels still remain 10-fold above preindustrial values in recent decades suggesting an impact from the growth in urban development

Interface hole-doping in cuprate-titanate superlattices

The electronic structure of interfaces between YBa$_2$Cu$_3$O$_6$ and SrTiO$_3$ is studied using local spin density approximation (LSDA) with intra-atomic Coulomb repulsion (LSDA+U). We find a metallic state in cuprate/titanate heterostructures with the hole carriers concentrated substantially in the CuO$_2$-layers and in the first interface TiO$_2$ and SrO planes. This effective interface doping appears due to the polarity of interfaces, caused by the first incomplete copper oxide unit cell. Interface-induced high pre-doping of CuO$_2$-layers is a key mechanism controlling the superconducting properties in engineered field-effect devices realized on the basis of cuprate/titanate superlattices.Comment: 5 pages, 5 figure

Magnetism and superconductivity at LAO/STO-interfaces: the role of Ti 3d interface electrons

Ferromagnetism and superconductivity are in most cases adverse. However, recent experiments reveal that they coexist at interfaces of LaAlO3 and SrTiO3. We analyze the magnetic state within density functional theory and provide evidence that magnetism is not an intrinsic property of the two-dimensional electron liquid at the interface. We demonstrate that the robust ferromagnetic state is induced by the oxygen vacancies in SrTiO3- or in the LaAlO3-layer. This allows for the notion that areas with increased density of oxygen vacancies produce ferromagnetic puddles and account for the previous observation of a superparamagnetic behavior in the superconducting state.Comment: 5 pages, 4 figures, to appear in Physical Review B (Rapid Communications

Comparative study of gp130 cytokine effects on corticotroph AtT-20 cells - Redundancy or specificity of neuroimmunoendocrine modulators?

Objective: This comparative in vitro study examined the effects of all known gp130 cytokines on murine corticotroph AtT-20 cell function. Methods: Cytokines were tested at equimolar concentrations from 0.078 to 10 nM. Tyrosine phosphorylation of the signal transducer and activator of transcription ( STAT) 3 and STAT1, the STAT-dependent suppressor of cytokine signaling (SOCS)-3 promoter activity, SOCS-3 gene expression, STAT-dependent POMC promoter activity and adrenocorticotropic hormone ( ACTH) secretion were determined. Results: Leukemia inhibitory factor (LIF), human oncostatin M (OSM) and cardiotrophin (CT)-1 (LIFR/gp130 ligands), as well as ciliary neurotrophic factor ( CNTF) and novel neurotrophin1/B-cell stimulating factor-3 (CNTFRalpha/LIFR/gp130 ligands) are potent stimuli of corticotroph cells in vitro. In comparison, interleukin (IL)-6 (IL-6R/gp130 ligand) and IL-11 (IL-11R/gp130 ligand) exhibited only modest direct effects on corticotrophs, while murine OSM (OSMR/gp130 ligand) showed no effect. Conclusion: (i) CNTFR complex ligands are potent stimuli of corticotroph function, comparable to LIFR complex ligands; (ii) IL-6 and IL-11 are relatively weak direct stimuli of corticotroph function; (iii) differential effects of human and murine OSM suggest that LIFR/gp130 (OSMR type I) but not OSMR/gp130 (OSMR type II) are involved in corticotroph signaling. (iv) CT-1 has the hitherto unknown ability to stimulate corticotroph function, and (v) despite redundant immuno-neuroendocrine effects of different gp130 cytokines, corticotroph cells are preferably activated through the LIFR and CNTFR complexes. Copyright (C) 2004 S. Karger AG, Basel