Imaging the Spatial Distribution of Electronic States in Graphene Using Electron Energy-Loss Spectroscopy: Prospect of Orbital Mapping.

The spatial distributions of antibonding π^{*} and σ^{*} states in epitaxial graphene multilayers are mapped using electron energy-loss spectroscopy in a scanning transmission electron microscope. Inelastic channeling simulations validate the interpretation of the spatially resolved signals in terms of electronic orbitals, and demonstrate the crucial effect of the material thickness on the experimental capability to resolve the distribution of unoccupied states. This work illustrates the current potential of core-level electron energy-loss spectroscopy towards the direct visualization of electronic orbitals in a wide range of materials, of huge interest to better understand chemical bonding among many other properties at interfaces and defects in solids.

Clinical and functional consequences of anti-properdin autoantibodies in patients with lupus nephritis.

Properdin is the only positive regulator of the complement system. In this study, we characterize the prevalence, functional consequences and disease associations of autoantibodies against properdin in a cohort of patients with autoimmune disease systemic lupus erythematosus (SLE) suffering from lupus nephritis (LN). We detected autoantibodies against properdin in plasma of 22·5% of the LN patients (16 of 71) by enzyme-linked immunosorbent assay (ELISA). The binding of these autoantibodies to properdin was dose-dependent and was validated by surface plasmon resonance. Higher levels of anti-properdin were related to high levels of anti-dsDNA and anti-nuclear antibodies and low concentrations of C3 and C4 in patients, and also with histological signs of LN activity and chronicity. The high negative predictive value (NPV) of anti-properdin and anti-dsDNA combination suggested that patients who are negative for both anti-properdin and anti-dsDNA will not have severe nephritis. Immunoglobulin G from anti-properdin-positive patients' plasma increased the C3b deposition on late apoptotic cells by flow cytometry. Nevertheless, these IgGs did not modify substantially the binding of properdin to C3b, the C3 convertase C3bBb and the pro-convertase C3bB, evaluated by surface plasmon resonance. In conclusion, anti-properdin autoantibodies exist in LN patients. They have weak but relevant functional consequences, which could have pathological significance.

Spontaneous exchange bias formation driven by a structural phase transition in the antiferromagnetic material.

Most of the magnetic devices in advanced electronics rely on the exchange bias effect, a magnetic interaction that couples a ferromagnetic and an antiferromagnetic material, resulting in a unidirectional displacement of the ferromagnetic hysteresis loop by an amount called the 'exchange bias field'. Setting and optimizing exchange bias involves cooling through the Néel temperature of the antiferromagnetic material in the presence of a magnetic field. Here we demonstrate an alternative process for the generation of exchange bias. In IrMn/FeCo bilayers, a structural phase transition in the IrMn layer develops at room temperature, exchange biasing the FeCo layer as it propagates. Once the process is completed, the IrMn layer contains very large single-crystal grains, with a large density of structural defects within each grain, which are promoted by the FeCo layer. The magnetic characterization indicates that these structural defects in the antiferromagnetic layer are behind the resulting large value of the exchange bias field and its good thermal stability. This mechanism for establishing the exchange bias in such a system can contribute towards the clarification of fundamental aspects of this exchange interaction.

HAADF-STEM Image Resolution Enhancement Using High-Quality Image Reconstruction Techniques: Case of the Fe3O4(111) Surface.

From simple averaging to more sophisticated registration and restoration strategies, such as super-resolution (SR), there exist different computational techniques that use a series of images of the same object to generate enhanced images where noise and other distortions have been reduced. In this work, we provide qualitative and quantitative measurements of this enhancement for high-angle annular dark-field scanning transmission electron microscopy imaging. These images are compared in two ways, qualitatively through visual inspection in real and reciprocal space, and quantitatively, through the calculation of objective measurements, such as signal-to-noise ratio and atom column roundness. Results show that these techniques improve the quality of the images. In this paper, we use an SR methodology that allows us to take advantage of the information present in the image frames and to reliably facilitate the analysis of more difficult regions of interest in experimental images, such as surfaces and interfaces. By acquiring a series of cross-sectional experimental images of magnetite (Fe3O4) thin films (111), we have generated interpolated images using averaging and SR, and reconstructed the atomic structure of the very top surface layer that consists of a full monolayer of Fe, with topmost Fe atoms in tetrahedrally coordinated sites.

[Antibodies Against Immunologically Sequestered Antigens in Patients with Polycystic Ovary Syndrome (PCOS).]

Polycystic ovary syndrome (PCOS) is a leading cause of anovulatory infertility. In recent times, autoimmune processes are supposed to play a role in a number of conditions with unexplained etiology. This includes some cases of human infertility. The attempts to detect antiovarian antibodies in patients with PCOS generally produced negative results. Presence of non-organ specific autoantibodies in patients with polycytosis has been reported, but the data are till inconsistent. Meanwhile, a number of recent sludies reveal a correlation between PCOS, hypothyroidism (manifested or subclinical) and autoimmunity. In this respect, many authors recommend thyroid function to be regularly checked in patients with PCOS. There are data that certain categories of women with polycystosis show an elevated concentration of antisperm antibodies. The problem is an interesting example how a pathological process can elucidate the complex interactions between the immune system and various compartments of the endocrine system that include immunologically isolated antigens.

Charging Dirac states at antiphase domain boundaries in the three-dimensional topological insulator Bi2Se3.

Using scanning tunneling microscopy and transmission electron microscopy, we demonstrate the existence of antiphase boundaries between neighboring grains shifted by a fraction of a quintuple layer in epitaxial (0001) films of the three-dimensional topological insulator Bi(2)Se(3). Scanning tunneling spectroscopy and first-principles calculations reveal that these antiphase boundaries provide electrostatic fields on the order of 10(8) V/m that locally charge the Dirac states, modulating the carrier density, and shift the Dirac point by up to 120 meV. This intrinsic electric field effect, demonstrated here near interfaces between Bi(2)Se(3) grains, provides direct experimental evidence at the atomic scale that the Dirac states are indeed robust against extended structural defects and tunable by electric field. These results also shed light on the recent observation of coexistence of Dirac states and two-dimensional electron gas on Bi(2)Se(3) (0001) after adsorption of metal atoms and gas molecules.

Effective modelling of the Seebeck coefficient of Fe2VAl.

Previous first-principles calculations have failed to reproduce many of the key thermoelectric features of Fe2VAl, e.g. the maximum values of the Seebeck coefficient S and its asymmetry with respect to the chemical potential. Also, previous theoretical predictions suggested that the pseudo band gap of Fe2VAl switches from indirect to direct upon doping. In this work, we report first-principles calculations that correctly reproduce the experimentally measured thermoelectric properties of Fe2VAl. This is achieved by adding a larger Hubbard U term to V atoms than to Fe atoms and including a scissors operator afterwards. As a result, bulk Fe2VAl is modelled as a gapless semiconductor with maximum S values of 76 and -158 [Formula: see text]V K-1 for p - and n-type, respectively, which agree well with the experimental measurements.

Atomic-level structural and chemical analysis of Cr-doped Bi2Se3 thin films.

We present a study of the structure and chemical composition of the Cr-doped 3D topological insulator Bi2Se3. Single-crystalline thin films were grown by molecular beam epitaxy on Al2O3 (0001), and their structural and chemical properties determined on an atomic level by aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy. A regular quintuple layer stacking of the Bi2Se3 film is found, with the exception of the first several atomic layers in the initial growth. The spectroscopy data gives direct evidence that Cr is preferentially substituting for Bi in the Bi2Se3 host. We also show that Cr has a tendency to segregate at internal grain boundaries of the Bi2Se3 film.

Spin pumping in magnetic trilayer structures with an MgO barrier.

We present a study of the interaction mechanisms in magnetic trilayer structures with an MgO barrier grown by molecular beam epitaxy. The interlayer exchange coupling, Aex, is determined using SQUID magnetometry and ferromagnetic resonance (FMR), displaying an unexpected oscillatory behaviour as the thickness, tMgO, is increased from 1 to 4 nm. Transmission electron microscopy confirms the continuity and quality of the tunnelling barrier, eliminating the prospect of exchange arising from direct contact between the two ferromagnetic layers. The Gilbert damping is found to be almost independent of the MgO thickness, suggesting the suppression of spin pumping. The element-specific technique of x-ray detected FMR reveals a small dynamic exchange interaction, acting in concert with the static interaction to induce coupled precession across the multilayer stack. These results highlight the potential of spin pumping and spin transfer torque for device applications in magnetic tunnel junctions relying on commonly used MgO barriers.

Origin of anomalous magnetite properties in crystallographic matched heterostructures: Fe3O4(111)/MgAl2O4(111).

Magnetite films grown on crystallographically matched substrates such as MgAl2O4 are not expected to show anomalous properties such as negative magnetoresistance and high saturation fields. By atomic resolution imaging using scanning transmission electron microscopy we show direct evidence of anti-phase domain boundaries (APB) present in these heterostructures. Experimentally identified 1/4<101> shifts determine the atomic structure of the observed APBs. The dominant non-bulk superexchange interactions are between 180° octahedral-Fe/O/octahedral-Fe sites which provide strong antiferromagnetic coupling across the defect interface resulting in non-bulk magnetic and magnetotransport properties.

Thickness dependence of the strain, band gap and transport properties of epitaxial In2O3 thin films grown on Y-stabilised ZrO2(111).

Epitaxial films of In(2)O(3) have been grown on Y-stabilised ZrO(2)(111) substrates by molecular beam epitaxy over a range of thicknesses between 35 and 420 nm. The thinnest films are strained, but display a 'cross-hatch' morphology associated with a network of misfit dislocations which allow partial accommodation of the lattice mismatch. With increasing thickness a 'dewetting' process occurs and the films break up into micron sized mesas, which coalesce into continuous films at the highest coverages. The changes in morphology are accompanied by a progressive release of strain and an increase in carrier mobility to a maximum value of 73 cm(2) V(-1) s(-1). The optical band gap in strained ultrathin films is found to be smaller than for thicker films. Modelling of the system, using a combination of classical pair-wise potentials and ab initio density functional theory, provides a microscopic description of the elastic contributions to the strained epitaxial growth, as well as the electronic effects that give rise to the observed band gap changes. The band gap increase induced by the uniaxial compression is offset by the band gap reduction associated with the epitaxial tensile strain.

Selected growth of cubic and hexagonal GaN epitaxial films on polar MgO(111).

Selected molecular beam epitaxy of zinc blende (111) or wurtzite (0001) GaN films on polar MgO(111) is achieved depending on whether N or Ga is deposited first. The cubic stacking is enabled by nitrogen-induced polar surface stabilization, which yields a metallic MgO(111)-(1 x 1)-ON surface. High-resolution transmission electron microscopy and density functional theory studies indicate that the atomically abrupt semiconducting GaN(111)/MgO(111) interface has a Mg-O-N-Ga stacking, where the N atom is bonded to O at a top site. This specific atomic arrangement at the interface allows the cubic stacking to more effectively screen the substrate and film electric dipole moment than the hexagonal stacking, thus stabilizing the zinc blende phase even though the wurtzite phase is the ground state in the bulk.

[Effect of trichlorfon on the blood resorption and elimination of radioactive vitamin B1 in cocks]. / Vliianie na trikhlorfona vurkhu rezorbtsiiata i eliminiraneto na radioaktiven vitamin B1 ot kruvta na petli.

Experimental studies on the effect of trichlorphon (neguvon) on the rate of vitamin B1 resorption in the alimentary tract and elimination by the blood in 12 cocks were carried out. Oral or intravenous application of 35S thiamin in the form of hypotonic and physiological solution was used for the previously treated per os with a neguvon water solution (40 mg/kg weight) cocks. As check the same cocks were treated three weeks before trichlorphon application by the radioindicator only. The birds' blood plasma was radiometrically studied (imp/min) after the "thin layer" method. It was established that as a result of trichlorphon solution treatment the radioactive vitamin B1 was immediately resorbed by the alimentary tract and its elimination by cock blood was reduced. The factors taking part in the mechanism of the observed phenomena are discussed.

[Changes of laboratory hematologic indices in patients with chronic glomerulopathies following treatment with superhigh doses of cyclophosphamide]. / Promeni v niakoi khematologichni laboratorni pokazetali pri bolni s khronichni glomerulopatii sled lechenie sus svrukhvisoki dozi tsiklofosfamid.

41 patients with active glomerulopathies treated with super high doses of Cyclophosphamide were studied. The following indices were followed up dynamically: hemoglobin concentration, number and morphology of erythrocytes, number and morphology of leucocytes and differential count. Hemoglobin concentration and erythrocyte count remain in the reference ranges in most of the patients. They fall more considerably compared to the initial values between the 90-120 day after the treatment. This fall improves spontaneously and does not require discontinuance of the treatment. The single application of super high dose of Cyclophosphamide does not influence significantly the leucopoiesis. Because of the parallel application of glucocorticosteroids no fall of the leucocyte count is observed and they remain in their reference ranges.