On the problem of Dirac cones in fullerenes on gold.

Artificial graphene based on molecular networks enables the creation of novel 2D materials with unique electronic and topological properties. Landau quantization has been demonstrated by CO molecules arranged on the two-dimensional electron gas on Cu(111) and the observation of electron quantization may succeed based on the created gauge fields. Recently, it was reported that instead of individual manipulation of CO molecules, simple deposition of nonpolar C60 molecules on Cu(111) and Au(111) produces artificial graphene as evidenced by Dirac cones in photoemission spectroscopy. Here, we show that C60-induced Dirac cones on Au(111) have a different origin. We argue that those are related to umklapp diffraction of surface electronic bands of Au on the molecular grid of C60 in the final state of photoemission. We test this alternative explanation by precisely probing the dimensionality of the observed conical features in the photoemission spectra, by varying both the incident photon energy and the degree of charge doping via alkali adatoms. Using density functional theory calculations and spin-resolved photoemission we reveal the origin of the replicating Au(111) bands and resolve them as deep leaky surface resonances derived from the bulk Au sp-band residing at the boundary of its surface projection. We also discuss the manifold nature of these resonances which gives rise to an onion-like Fermi surface of Au(111).

Calculation of the ovule number in the genus Salix: A method for taxa differentiation.

PREMISE: Recent investigations have demonstrated that the number of ovules present in the ovaries of the willow flower (Salix spp., Salicaceae) can be used to confirm the identification of species and hybrids. We present the method to calculate the ovule number, along with examples demonstrating its use for both species and hybrid verification. METHODS AND RESULTS: The best time to obtain a reliable ovule count is at the beginning of anthesis before numerous hairs develop in the ovary or after seed dispersal when the funiculi on the placenta can be counted. The ovules in all of the ovaries of one catkin should be counted, and the ovule index is recorded as their minimum-maximum range. The ovule number of a hybrid is the statistical mean of the ovule number of its parents. CONCLUSIONS: Ovule quantification is a useful tool that, in conjunction with traditional morphological and modern molecular techniques, presents additional evidence to support taxonomic decisions. The ovule number can also assist in species identification, classification, and in hybridization studies to verify the parentage of willow hybrids.

Extremely flat band in bilayer graphene.

We propose a novel mechanism of flat band formation based on the relative biasing of only one sublattice against other sublattices in a honeycomb lattice bilayer. The mechanism allows modification of the band dispersion from parabolic to "Mexican hat"-like through the formation of a flattened band. The mechanism is well applicable for bilayer graphene-both doped and undoped. By angle-resolved photoemission from bilayer graphene on SiC, we demonstrate the possibility of realizing this extremely flattened band (< 2-meV dispersion), which extends two-dimensionally in a k-space area around the K ¯ point and results in a disk-like constant energy cut. We argue that our two-dimensional flat band model and the experimental results have the potential to contribute to achieving superconductivity of graphene- or graphite-based systems at elevated temperatures.

Surface Composition of Free Mixed NaCl/Na2SO4 Nanoscale Aerosols Probed by X-ray Photoelectron Spectroscopy.

The local chemical surface composition of unsupported mixed solid NaCl/Na2SO4 aerosols ( d ∼ 70 nm) is studied by X-ray photoelectron spectroscopy. The solid aerosols are generated by drying aqueous droplets containing mixtures of the two salts in different mole fractions. The mole fraction of these salts is found to deviate at the solid aerosol surface significantly from the initial droplet composition. The minority species in the droplets are found to be enhanced at the surface of the solid mixed aerosols. This surface enhancement is rationalized in terms of the nucleation/crystallization process, where the salts evidently do not cocrystallize, rather than each salt forms pure crystal moieties. Characteristic variations of the surface ion concentration as a function of the mole fraction of the salts in the initial droplet are observed in the nanometer size regime. This is unlike core-shell architectures previously found in mixed micron salt aerosols, indicating that aerosol models derived from micron-sized aerosols are evidently not fully reliable to describe the surface composition of nanosized aerosols. Furthermore, surface enhancement of the minority component in mixed NaCl/Na2SO4 aerosols is also different from previous results on surface segregation of mixed NaCl/NaBr aerosols, where one of the anionic species is surface segregated for all mole fractions, which was explained in terms of the ability of the involved salts to cocrystallize and forming solid solutions. The present results rather indicate that mixed NaCl/Na2SO4 aerosols do not cocrystallize. Electron microscopy of deposited mixed salt aerosols reveals mostly a cubic structure of pure NaCl aerosols, whereas mixed salt aerosols are found to show a grainy structure composed of multiple small crystals which supports the present findings obtained from photoelectron spectroscopy.

PREVENTION OF HEART FAILURE PATIENTS WITH DECREASED EJECTION FRACTION IN NON-CARDIAC SURGERY: LEVOSIMENDAN OR ANESTHETIC CARDIOPROTECTION?.

BACKGROUND: Chronic heart failure (CHF) significantly worsens the prognosis of surgical treatment in noncardiac surgery, doubling mortality in compared with patients with coronary artery disease. Modern anesthesiology has at least two methods that potentially can improve the results in noncardiac surgery: anesthetic cardioprotection and the prevention of CHF decompensation with levosimendan. THE AIM: to study the efficacy of anesthetic cardioprotection andpreoperative preparation with levosimendan for the prevention of CHF decompensation in patients with reduced left ventricular ejectionfraction in noncardiac surgery. ENDPOINTS: the primary endpoint of the trial is the need and the maximum dose of inotropic drugs in the perioperative period; secondary point: the length of stay in the ICU, composite outcome, the dynamics of SI, FI, the content ofNT-proBNP and TnT Materials and methods: A randomized study was performed in three groups of patients during reconstructive operations on infrarenal part of aorta: control (traditional methodfor prevention of decompensation of CHF were used) - 31 patients; the group with the anesthetic cardioprotectivei - 31 patients; the group with a preoperative preparing with levosimendan - 30 patients. RESULTS: The incidence of heart failure (estimated by need to use inotropic drugs - IS) was 83% of control group patients and 75% of the patients of the group "VIMA" (p = 0,65). The number ofpatients needing the use of dobutamine in LS-group was significantly below, 50% (p = 0,02 relative to control group and p = 0,08 compared to the group VIMA). IS in the control group was 8 [6, 9] µg xkg⁻¹ - xmin⁻¹ ; group VIMA 8 [3; 9] mg xkg ⁻¹ xmin⁻¹ , whereas in the LS group only 2 [0; 7] mg ⁻¹ xkg⁻¹ xmin⁻¹ . Differences between groups credible, given the Bonferroni correction (p = 0,0015). In our study, was not identified significant differences in 30-day mortality: in the control group it was 3,4%; in the group VIMA of 3,1%; in the group of LS - 0% (p > 0,017); however, a composite outcome (number of adverse events (heart attack+stroke+mortality) were slightly better in the LS group - 17%, against 34% in the control group (p = 0,043). CONCLUSION: Preoperative preparation with levosimendan in patients with reduced fraction left ventricle ejection when performing reconstructive operations on the descending aorta reduces the incidence of episodes of decompensation of heart failure compared with the control group to 39,8% (p < 0,05). The use of this technique improves the composite outcome of operations on the infrarenal aorta. The study has not shown the influence of anesthetic cardioprotection in terms of hospitalization and composite outcome of surgical treatment.

Transport Gap Opening and High On-Off Current Ratio in Trilayer Graphene with Self-Aligned Nanodomain Boundaries.

Trilayer graphene exhibits exceptional electronic properties that are of interest both for fundamental science and for technological applications. The ability to achieve a high on-off current ratio is the central question in this field. Here, we propose a simple method to achieve a current on-off ratio of 10(4) by opening a transport gap in Bernal-stacked trilayer graphene. We synthesized Bernal-stacked trilayer graphene with self-aligned periodic nanodomain boundaries (NBs) on the technologically relevant vicinal cubic-SiC(001) substrate and performed electrical measurements. Our low-temperature transport measurements clearly demonstrate that the self-aligned periodic NBs can induce a charge transport gap greater than 1.3 eV. More remarkably, the transport gap of ∼0.4 eV persists even at 100 K. Our results show the feasibility of creating new electronic nanostructures with high on-off current ratios using graphene on cubic-SiC.

Tunable Fermi level and hedgehog spin texture in gapped graphene.

Spin and pseudospin in graphene are known to interact under enhanced spin-orbit interaction giving rise to an in-plane Rashba spin texture. Here we show that Au-intercalated graphene on Fe(110) displays a large (∼230 meV) bandgap with out-of-plane hedgehog-type spin reorientation around the gapped Dirac point. We identify two causes responsible. First, a giant Rashba effect (∼70 meV splitting) away from the Dirac point and, second, the breaking of the six-fold graphene symmetry at the interface. This is demonstrated by a strong one-dimensional anisotropy of the graphene dispersion imposed by the two-fold-symmetric (110) substrate. Surprisingly, the graphene Fermi level is systematically tuned by the Au concentration and can be moved into the bandgap. We conclude that the out-of-plane spin texture is not only of fundamental interest but can be tuned at the Fermi level as a model for electrical gating of spin in a spintronic device.

Reversal of the circular dichroism in angle-resolved photoemission from Bi2Te3.

The helical Dirac fermions at the surface of topological insulators show a strong circular dichroism which has been explained as being due to either the initial-state spin angular momentum, the initial-state orbital angular momentum, or the handedness of the experimental setup. All of these interpretations conflict with our data from Bi(2)Te(3) which depend on the photon energy and show several sign changes. Our one-step photoemission calculations coupled to ab initio theory confirm the sign change and assign the dichroism to a final-state effect. Instead, the spin polarization of the photoelectrons excited with linearly polarized light remains a reliable probe for the spin in the initial state.

The graphene/Au/Ni interface and its application in the construction of a graphene spin filter.

A modification of the contact of graphene with ferromagnetic electrodes in a model of the graphene spin filter allowing restoration of the graphene electronic structure is proposed. It is suggested for this aim to intercalate into the interface between the graphene and the ferromagnetic (Ni or Co) electrode a Au monolayer to block the strong interaction between the graphene and Ni (Co) and, thus, prevent destruction of the graphene electronic structure which evolves in direct contact of graphene with Ni (Co). It is also suggested to insert an additional buffer graphene monolayer with the size limited by that of the electrode between the main graphene sheet providing spin current transport and the Au/Ni electrode injecting the spin current. This will prevent the spin transport properties of graphene from influencing contact phenomena and eliminate pinning of the graphene electronic structure relative to the Fermi level of the metal, thus ensuring efficient outflow of injected electrons into the graphene. The role of the spin structure of the graphene/Au/Ni interface with enhanced spin-orbit splitting of graphene π states is also discussed, and its use is proposed for additional spin selection in the process of the electron excitation.

Giant Rashba splitting in graphene due to hybridization with gold.

Graphene in spintronics is predominantly considered for spin current leads of high performance due to weak intrinsic spin-orbit coupling of the graphene π electrons. Externally induced large spin-orbit coupling opens the possibility of using graphene in active elements of spintronic devices such as the Das-Datta spin field-effect transistor. Here we show that Au intercalation at the graphene-Ni interface creates a giant spin-orbit splitting (~100 meV) of the graphene Dirac cone up to the Fermi energy. Photoelectron spectroscopy reveals the hybridization with Au 5d states as the source for this giant splitting. An ab initio model of the system shows a Rashba-split spectrum around the Dirac point of graphene. A sharp graphene-Au interface at the equilibrium distance accounts for only ~10 meV spin-orbit splitting and enhancement is due to the Au atoms in the hollow position that get closer to graphene and do not break the sublattice symmetry.

Tolerance of topological surface states towards magnetic moments: Fe on Bi2Se3.

We study the effect of Fe impurities deposited on the surface of the topological insulator Bi(2)Se(3) by means of core-level and angle-resolved photoelectron spectroscopy. The topological surface state reveals surface electron doping when the Fe is deposited at room temperature and hole doping with increased linearity when deposited at low temperature (~8 K). We show that in both cases the surface state remains intact and gapless, in contradiction to current belief. Our results suggest that the surface state can very well exist at functional interfaces with ferromagnets in future devices.

Ir(111) surface state with giant Rashba splitting persists under graphene in air.

We reveal a giant Rashba effect (α(R)≈1.3 eV Å) on a surface state of Ir(111) by angle-resolved photoemission and by density functional theory. It is demonstrated that the existence of the surface state, its spin polarization, and the size of its Rashba-type spin-orbit splitting remain unaffected when Ir is covered with graphene. The graphene protection is, in turn, sufficient for the spin-split surface state to survive in ambient atmosphere. We discuss this result along with indications for a topological protection of the surface state.

Tunable band gap in hydrogenated quasi-free-standing graphene.

We show by angle-resolved photoemission spectroscopy that a tunable gap in quasi-free-standing monolayer graphene on Au can be induced by hydrogenation. The size of the gap can be controlled via hydrogen loading and reaches approximately 1.0 eV for a hydrogen coverage of 8%. The local rehybridization from sp(2) to sp(3) in the chemical bonding is observed by X-ray photoelectron spectroscopy and X-ray absorption and allows for a determination of the amount of chemisorbed hydrogen. The hydrogen induced gap formation is completely reversible by annealing without damaging the graphene. Calculations of the hydrogen loading dependent core level binding energies and the spectral function of graphene are in excellent agreement with photoemission experiments. Hydrogenation of graphene gives access to tunable electronic and optical properties and thereby provides a model system to study hydrogen storage in carbon materials.

Is there a rashba effect in graphene on 3d ferromagnets?

Graphene is considered a candidate material for spintronics. Recently, graphene grown on Ni(111) has been reported to show a Rashba effect which depends on the magnetization. By spin- and angle-resolved photoelectron spectroscopy, we investigate the preconditions for such an effect for graphene on Ni as well as on Co which has a approximately 3x larger 3d magnetic moment: (i) spin polarization or (ii) exchange splitting of graphene pi states in normal emission geometry, and (iii) Rashba-type spin-orbit splitting off normal. As none of these are found to be of considerable size, the reported effect is neither Rashba-type, nor due to the spin-orbit coupling, nor involving the electron spin.

Electronic and magnetic properties of quasifreestanding graphene on Ni.

For the purpose of recovering the intriguing electronic properties of freestanding graphene at a solid surface, graphene self-organized on a Au monolayer on Ni(111) is prepared and characterized by scanning tunneling microscopy. Angle-resolved photoemission reveals a gapless linear pi-band dispersion near K[over] as a fingerprint of strictly monolayer graphene and a Dirac crossing energy equal to the Fermi energy (EF) within 25 meV meaning charge neutrality. Spin resolution shows a Rashba effect on the pi states with a large (approximately 13 meV) spin-orbit splitting up to EF which is independent of k.

[Mathematical model for study the reliability of organism function in extreme conditions of high altitude]. / Matematychni metody doslidzhennia problemy nadiinosti funktsionuvannia orhanizmu za ekstremal'nykh umov vysokohir'ia.

The health of a person and his capacity for work under conditions of high mountains in many respects is determined by the reliability of the function of physiological systems. Mathematical methods of both the reliability theory and mathematical simulation of basic functional systems are proposed to be used for investigating the reliability. It is shown that the most suitable reliability model for living systems is a chain model-a successive connection of links representing separate functional systems of organism. Besides, the weakest links determining the reliability of functioning of the whole organism under the extreme conditions of high mountains even for a healthy person are-respiration, blood circulation, thermoregulation and psychophysiological systems. Quantitative characteristics of the reliability of these systems are determined through the main indicators. The influence of non-sufficient contents of oxygen in respiration mixture, low atmospheric pressure, low temperatures of the environment are simulated by computer models of organism. An analyses of modeling data shows that moderate physical loading improves indicators of organisms adaptively to external conditions of high mountains and promotes the increasing of persons capacity for work and the reliability of his functioning.

[Dynamics of the process of gas transport into the body using a mathematical model]. / Issledovanie dinamiki protsessa perenosa gazov v organizme s pomoshch'iu matematicheskoi modeli

Dynamics of mass-transport of oxygen, carbon dioxide, and inert gases in lungs, blood, and tissues, as well as gas transport through alveolar capillary and erythrocyte membranes at rest and during exercise under normal and increased ambient pressures, were studied on a mathematical model. The model consists of 34 differential and 58 algebraic equations and makes it possible to estimate the dynamics of changes of over 90 parameters. The effect of various factors: duration of the respiratory cycle, tidal volume, airways resistance, the surface of diffusion, the resistance of alveolar-capillary wall, erythrocyte membrane, ventilation-perfusion relations, pulmonary blood shunts, blood supply to the tissues, Haldane and Verigo-Bohr effect, buffer capacity of the blood, and others) on the mass-transport of gases were quantitatively estimated.