Measurements of 18 O-Pi uptake indicate fast metabolism of phosphate in tree roots.

Phosphorus (P) nutrition of beech ecosystems depends on soil processes, plant internal P cycling and P acquisition. P uptake of trees in the field is currently not validated due to the lack of an experimental approach applicable in natural forests. Application of radiolabelled tracers such as 33 P and 32 P is limited to special research sites and not allowed in natural environments. Moreover, only one stable isotope of P, namely 31 P, exists. One alternative tool to measure P acquisition in the field could be the use of 18 O-labelled 31 P-phosphate (31 P18 O4 3- ). Phosphate (Pi ) uptake rates calculated from the 18 O enrichment of dried root material after application of 31 Pi 18 O4 3- via nutrient solution was always lower compared to 33 P incorporation, did not show increasing rates of Pi uptake at P deficiency under controlled conditions, and did not reveal seasonal fluctuations in the field. Consequently, a clear correlation between 33 P-based and 18 O-based Pi uptake by roots could not be established. Comparison of Pi  uptake rates achieved from 33 P-Pi and 18 O-Pi application led to the conclusion of high Pi metabolism in roots after Pi uptake. The replacement of 18 O by 16 O from water in 18 O-Pi during root influx, but most probably after Pi uptake into roots, due to metabolic activities, indicates high and fast turnover of Pi . Hence, the use of 18 O-Pi as an alternative tool to estimate Pi acquisition of trees in the field must consider the increase of 18 O abundance in root water that was disregarded in dried root material.

Decomposition of Methanol on Mixed CuO-CuWO4 Surfaces.

Mixed CuO(2 × 1)-CuWO4 layers on a Cu(110) surface have been prepared by the on-surface reaction of the CuO(2 × 1) surface oxide with adsorbed (WO3)3 clusters. The adsorption and decomposition of methanol on these well-defined CuO-CuWO4 surfaces has been followed by high-resolution X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), and temperature-programmed desorption (TPD) to assess the molecular surface species and their concentration, while the state of the surface oxide phases before and after methanol decomposition has been characterized by scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and XPS. Surface methoxy species form the primary methanol decomposition products, which desorb partly by recombination as methanol at 200-300 K or decompose into CHx and possibly CO. The most reactive surfaces are mixed CuO-CuWO4 phase, with CuWO4 coverages 0.5-0.8 monolayer, thus pointing at the importance of oxide phase boundary sites. In a minority reaction channel, a small amount of formaldehyde is detected on the CuWO4 surface. The CuWO4 oxide phase becomes modified as a result of reduction and a morphology transition triggered by the methanol decomposition, but the pristine surface state can be recovered by a postoxidation treatment with oxygen.

Phase behaviour of 2D MnWO x and FeWO x ternary oxide layers on Pd(1 0 0).

The structure and properties of ternary oxide materials at the nanoscale are poorly explored both on experimental and theoretical levels. With this work we demonstrate the successful on-surface synthesis of two-dimensional (2D) ternary oxide, MnWO x and FeWO x , nanolayers on a Pd(1 0 0) surface and the understanding of their new structure and phase behaviour with the help of state-of-art surface structure and spectroscopy techniques. We find that the 2D MnWO x and FeWO x phases, prepared under identical thermodynamic conditions, exhibit similar structural properties, reflecting the similarity of the bulk MnWO4 and FeWO4 phases with the wolframite structure. Structure models of prototypical 2D ternary oxide phases are proposed and discussed in the light of new structure architecture concepts which have no analogues in the bulk.

Two-Dimensional Iron Tungstate: A Ternary Oxide Layer With Honeycomb Geometry.

The exceptional physical properties of graphene have sparked tremendous interests toward two-dimensional (2D) materials with honeycomb structure. We report here the successful fabrication of 2D iron tungstate (FeWO x ) layers with honeycomb geometry on a Pt(111) surface, using the solid-state reaction of (WO3)3 clusters with a FeO(111) monolayer on Pt(111). The formation process and the atomic structure of two commensurate FeWO x phases, with (2 × 2) and (6 × 6) periodicities, have been characterized experimentally by combination of scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD) and understood theoretically by density functional theory (DFT) modeling. The thermodynamically most stable (2 × 2) phase has a formal FeWO3 stoichiometry and corresponds to a buckled Fe2+/W4+ layer arranged in a honeycomb lattice, terminated by oxygen atoms in Fe-W bridging positions. This 2D FeWO3 layer has a novel structure and stoichiometry and has no analogues to known bulk iron tungstate phases. It is theoretically predicted to exhibit a ferromagnetic electronic ground state with a Curie temperature of 95 K, as opposed to the antiferromagnetic behavior of bulk FeWO4 materials.

Factors influencing posaconazole plasmatic concentrations in patients presenting with acute myeloid leukemia.

PURPOSE: The effectiveness of posaconazole (PSZ) prophylaxis on invasive fungal infections, in patients presenting with acute myeloid leukemia (AML), seems to be correlated to its blood plasma concentration. Our goal was to identify the risk factors for underdosing. PATIENTS AND METHODS: We retrospectively reviewed the records of patients treated for AML treated with PSZ, during a 2-year period. Assays<500ng/mL were considered as under dosed. RESULTS: Fifty-nine assays (43 patients) were performed during induction (n=22) or consolidation (n=37) chemotherapy. PSZ treatment was initiated within a median of 3 days before neutropenia with a first assay performed at 8 days (3-28). The median PSZ blood plasma concentration was 375ng/mL (<200-1900). Forty-one (69%) treatment were maintained until the end of neutropenia. One patient presented with candidemia, 9 with possible invasive aspergillosis, without any significant association with underdosing. The univariate analysis showed that co-administration of proton pump inhibitors (PPIs) (P=0.01) and cause of hospitalization (induction chemotherapy vs consolidation, P=0.008) were associated with underdosing, contrary to feeding difficulties (P=0.07) and digestive disorders (P=0.5). The multivariate analysis confirmed the impact of PPI use (P=0.01) and the cause of hospitalization (P=0.003). CONCLUSION: This study highlights the major impact of PPI administration on PSZ blood plasma levels and stresses the risk of non-effective prophylaxis during induction treatment of AML.

Discontinuation of empirical antibiotic therapy in neutropenic acute myeloid leukaemia patients with fever of unknown origin: is it ethical?

Based on recommendations of the ECIL-4, we prospectively evaluated discontinuation of empirical antibiotic therapy in high-risk neutropenic acute myeloid leukaemia patients with fever of unknown origin. Seven patients (median neutropenia duration 30 days) were included. Four of them remained afebrile but quickly recovered from neutropenia. The other three had rapid recurrent fever. Two of these three patients had bacteraemia with susceptible strains and one of them was transferred to the ICU for septic shock. Median duration of sparing of antibiotics for the seven patients was 3 days (2-4). Because of these limited results the study was stopped.

Nanostripe pattern of NaCl layers on Cu(110).

A sodium chloride monolayer on a Cu(110) surface gives rise to a highly corrugated periodic nanostripe pattern of the (100) lattice as observed by scanning tunneling microscopy and low-energy electron diffraction. As revealed by density-functional calculations, this pattern is a consequence of the frustration of the overlayer-substrate chemical bonding produced by epitaxial mismatch. The coexistence of regions of strong Cu-Cl covalent and weak nonbonding interactions leads to a chemically induced topographic modulation here realized in a two-dimensional dielectric. The carpetlike growth of the NaCl layer across Cu step edges induces a distinct contrast inversion in the stripe pattern as a result of the change in epitaxial relationship due to the stacking sequence of the (110) Cu layers. It is demonstrated that the competition between local substrate-overlayer and intraoverlayer interactions can support a well-defined heteroepitaxial relationship of a ionic dielectric film and a metal surface, with important consequences for the nanoscale morphology and related properties.

Tailor-made ultrathin manganese oxide nanostripes: 'magic widths' on Pd(1 1 N) terraces.

The growth of ultrathin two-dimensional manganese oxide nanostripes on vicinal Pd(1 1 N) surfaces leads to particular stable configurations for certain combinations of oxide stripe and substrate terrace widths. Scanning tunneling microscopy and high-resolution low-energy electron diffraction measurements reveal highly ordered nanostructured surfaces with excellent local and long-range order. Density functional theory calculations provide the physical origin of the stabilization mechanism of 'magic width' stripes in terms of a finite-size effect, caused by the significant relaxations observed at the stripe boundaries.

The two-dimensional cobalt oxide (9 × 2) phase on Pd(100).

The two-dimensional (2D) Co oxide monolayer phase with (9 × 2) structure on Pd(100) has been investigated experimentally by scanning tunneling microscopy (STM) and theoretically by density functional theory (DFT). The high-resolution STM images reveal a complex pattern which on the basis of DFT calculations is interpreted in terms of a coincidence lattice, consisting of a CoO(111)-type bilayer with significant symmetry relaxation and height modulations to reduce the polarity in the overlayer. The most stable structure displays an unusual zig-zag type of antiferromagnetic ordering. The (9 × 2) Co oxide monolayer is energetically almost degenerate with the c(4 × 2) monolayer phase, which is derived from a single CoO(100)-type layer with a Co(3)O(4) vacancy structure. Under specific preparation conditions, the (9 × 2) and c(4 × 2) structures can be observed in coexistence on the Pd(100) surface and the two phases are separated by a smooth interfacial boundary line, which has been analyzed at the atomic level by STM and DFT. The here described 2D Co oxide nanolayer systems are characterized by a delicate interplay of chemical, electronic, and interfacial strain interactions and the associated complexities in the theoretical description are emphasized and discussed.

Interplay between magnetic, electronic, and vibrational effects in monolayer Mn3O4 grown on Pd(100).

The surface stabilized MnO(100)-like monolayer, characterized by a regular c(4 x 2) distribution of Mn vacancies, is studied by hybrid functionals and discussed in the light of available scanning tunneling microscopy and high-resolution electron energy loss spectroscopy data. We show that the use of hybrid functionals is crucial to account for the intermingled nature of magnetic interactions, electron localization, structural distortions, and surface phonons. The proposed Pd(100) supported Mn(3)O(4) structure is excellently compatible with the experiments previously reported in literature.

Two-dimensional manganese oxide nanolayers on Pd(100): the surface phase diagram.

Two-dimensional manganese oxide layers have been grown on Pd(100) and have been characterized by means of scanning tunnelling microscopy, low energy electron diffraction and x-ray photoelectron spectroscopy (XPS). The complex surface phase diagram of MnO(x) on Pd(100) is reported, where nine different novel Mn oxide phases have been detected as a function of the chemical potential of oxygen µ(O). Three regions of the chemical potential of oxygen can be identified, in which structurally related oxide phases are formed, often in coexistence at the surface. The different regions of µ(O) are reflected in the oxidation states of the respective Mn oxide nanolayers as revealed by the Mn 2p and O 1s XPS binding energies. The MnO(x) nanolayers form two-dimensional wetting layers and it is speculated that they mediate the epitaxial growth of MnO on Pd(100) by providing structurally graded interfaces.

Nucleation and 3D growth of para-sexiphenyl nanostructures from an oriented 2D liquid layer investigated by photoemission electron microscopy.

The deposition in an ultrahigh vacuum of prototypical linear para-sexiphenyl (6P) molecules onto the anisotropic reconstructed surface of Cu(110)2 × 1-O presents an ideal system with reduced symmetry for investigation. A dynamic photoemission electron microscopy (PEEM) study of the nucleation and growth of 6P, combined with data obtained from static techniques, is shown to facilitate our understanding of the requirements for 6P nuclei formation and self-assembly into long anisotropic needles. High-rate image acquisitions in PEEM are shown to reveal dynamic phenomena, such as meta-stable layer de-wetting and nanostructure growth in real time, that are the result of nucleation and self-assembly processes. Furthermore, time dependent studies of the relaxation of the meta-stable layer give insights into the molecular diffusion kinetics, whereas temperature dependent studies allow nucleation energies and molecular binding energies to be quantitatively measured. The deposition of the first monolayer of material is found to assemble without the formation of islands until full coverage (1 ML) is achieved. The second layer fills homogeneously and remains in a liquid smectic phase until a total deposition of 1.95 ± 0.07 ML is reached, whereupon critical nuclei of 6P crystallize out of the 2D liquid layer. The maximum of the diffusion coefficient is estimated to be 2 × 10(-9) cm(2) s(-1). The resulting de-wetting of the meta-stable second layer rapidly increases the size of the nuclei while maintaining the anisotropic needle nanostructure shape. Probing the de-wetting layer reveals that 6P diffusion is 1D up to 100 °C. The nucleation energy and intermolecular binding energy are measured to be 675 meV and 2.1 eV, respectively.

Intra- and intermolecular band dispersion in an organic crystal.

The high crystallinity of many inorganic materials allows their band structures to be determined through angle-resolved photoemission spectroscopy (ARPES). Similar studies of conjugated organic molecules of interest in optoelectronics are often hampered by difficulties in growing well-ordered and well-oriented crystals or films. We have grown crystalline films of uniaxially oriented sexiphenyl molecules and obtained ARPES data. Supported by density-functional calculations, we show that, in the direction parallel to the principal molecular axis, a quasi-one-dimensional band structure of a system of well-defined finite size develops out of individual molecular orbitals. In contrast, perpendicular to the molecules, the band structure reflects the periodicity of the molecular crystal, and continuous bands with a large dispersion were observed.

Chemical reactivity of Ni-Rh nanowires.

The properties of bimetallic Ni-Rh nanowires, fabricated by decorating the steps of vicinal Rh(111) surfaces by stripes of self-assembled Ni adatoms, have been probed by STM, photoemission, and ab initio density functional theory calculations. These Ni-Rh nanowires have specific electronic properties that lead to a significantly enhanced chemical reactivity towards oxygen. As a result, the Ni-Rh nanowires can be oxidized exclusively, generating novel quasi-one-dimensional oxide structures.

Model reaction studies on vanadium oxide nanostructures on Pd(111).

Deuterium desorption and reaction between deuterium and oxygen to water has been studied on ultrathin vanadium oxide structures prepared on Pd(111). The palladium sample was part of a permeation source, thus enabling the supply of atomic deuterium to the sample surface via the bulk. Different vanadium oxide films have been prepared by e-beam evaporation in UHV under oxygen atmosphere. The structure of these films was determined using low energy electron diffraction and scanning tunneling microscopy. The mean translational energy of the desorption and reaction products has been measured with a time-of-flight spectrometer. The most stable phases for monolayer and submonolayer VOx are particular surface-V2O3 and VO phases at 523 and 700 K, respectively. Thicker films grow in the form of bulk V2O3. The mean translational energy of the desorbing deuterium species corresponds in all cases to the thermalized value. Apparent deviations from this energy distribution could be attributed to different adsorption/desorption and/or accommodation behaviors of molecular deuterium from the gas phase on the individual vanadium oxide films. The water reaction product shows a slightly hyperthermal mean translational energy, suggesting that higher energetic permeating deuterium contributes with higher probability to the water formation.

Reactivity of V2O3(0001) surfaces: molecular vs dissociative adsorption of water.

The adsorption of water on V2O3(0001) surfaces has been investigated by thermal desorption spectroscopy, high-resolution electron energy loss spectroscopy, and X-ray photoelectron spectroscopy with use of synchrotron radiation. The V2O3(0001) surfaces have been generated in epitaxial thin film form on a Rh(111) substrate with three different surface terminations according to the particular preparation conditions. The stable surface in thermodynamic equilibrium with the bulk is formed by a vanadyl (VO) (1x1) surface layer, but an oxygen-rich (radical3xradical3)R30 degrees reconstruction can be prepared under a higher chemical potential of oxygen (microO), whereas a V-terminated surface consisting of a vanadium surface layer requires a low microO, which can be achieved experimentally by the deposition of V atoms onto the (1x1) VO surface. The latter two surfaces have been used to model, in a controlled way, oxygen and vanadium containing defect centres on V2O3. On the (1x1) V=O and (radical3xradical3)R30 degrees surfaces, which expose only oxygen surface sites, the experimental results indicate consistently that the molecular adsorption of water provides the predominant adsorption channel. In contrast, on the V-terminated (1/radical3x1/radical3)R30 degrees surface the dissociation of water and the formation of surface hydroxyl species at 100 K is readily observed. Besides the dissociative adsorption a molecular adsorption channel exists also on the V-terminated V2O3(0001) surface, so that the water monolayer consists of both OH and molecular H2O species. The V surface layer on V2O3 is very reactive and is reoxidised by adsorbed water at 250 K, yielding surface vanadyl species. The results of this study indicate that V surface centres are necessary for the dissociation of water on V2O3 surfaces.

Glycine-ice nanolayers: morphology and surface energetics.

Ultrathin glycine-ice films (nanolayers) have been prepared in ultrahigh vacuum by condensation of H(2)O and glycine at 110 K and 150 K on single crystalline Al(2)O(3) surfaces and have been investigated by temperature programed thermal desorption, x-ray photoelectron spectroscopy, and work function measurements. Various layer architectures have been considered, including glycine-on-ice, ice-on-glycine, and mixed glycine-ice nanolayers. Low coverages of adsorbed glycine molecules on amorphous ice surfaces suppress the amorphous-to-crystalline phase transition in the temperature range 140-160 K in near-surface regions and consequently lead to a lower desorption temperature of H(2)O molecules than from pure ice layers. Thicker glycine overlayers on ice provide a kinetic restriction to H(2)O desorption from the underlying ice layers until the glycine molecules become mobile and develop pathways for water desorption at higher temperature (>170 K). Ice overlayers do not wet glycine film surfaces, but the glycine molecules on ice are sufficiently immobile at 110 K, so that continuous glycine overlayers form. In mixed glycine-ice nanolayers the glycine phase displays hydrophobic behavior and a phase separation takes place, with the accumulation of glycine near the surfaces of the films.

Experimental and theoretical study of a surface stabilized monolayer phase of nickel oxide on Pd(100).

A surface stabilized monolayer phase of nickel oxide, c(4 x 2)-Ni(3)O(4), has been found to grow epitaxially under reactive deposition conditions on Pd(100), in the presence of other adsorbed phases and in competition with them. High-quality scanning tunneling microscopy data are reported and discussed, including a detailed analysis of the defects and of the border morphology of this new phase. The data are discussed in the light of ab initio simulations of the electronic, energetic, and geometric properties of such a phase. A hybrid-exchange density functional theory approach has been used, and a slab model is adopted where palladium is simulated by a thin film covered on both sides by regular epilayers. A growth model has been developed that explains both the unusual stoichiometry of the phase and the observed defects.

Bonding and structure of glycine on ordered Al2O3 film surfaces.

The interaction between glycine (NH2CH2COOH) layers and an ultrathin Al2O3 film grown epitaxially onto NiAl(110) was studied by temperature-programmed desorption, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, work function measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. At monolayer coverages at 110 K, there are two coexisting molecular forms: the anionic (NH2CH2COO-) and the zwitterionic form (NH3+CH2COO-) of glycine. As deduced from the photoemission data, the buildup of multilayers at 110 K leads to a condensed phase predominantly in the zwitterionic state. In contrast to the monolayer at 110 K, the monolayer formed at 300 K consists primarily of glycine molecules in the anionic state. The latter species is adsorbed with the oxygen atoms of the carboxylic group pointing toward the substrate. The polarization-dependent C K- and O K-edge NEXAFS spectra indicate that the glycinate species in the monolayer at 300 K is oriented nearly perpendicular to the surface, with the amino group pointing away from the surface.