Importance of Metal-Support Interactions for CO2 Hydrogenation: An Operando Near-Ambient Pressure X-ray Photoelectron Spectroscopy Study on Gold-Loaded In2O3 and CeO2 Catalysts

Metal-support interactions, which are essential for the design of supported metal catalysts, used, e.g., for CO2 activation, are still only partially understood. In this study of gold-loaded In2O3 and CeO2 catalysts during CO2 hydrogenation using near-ambient pressure X-ray photoelectron spectroscopy, supported by near edge X-ray absorption fine structure, we demonstrate that the role of the noble metal strongly depends upon the choice of the support material. Temperature-dependent analyses of X-ray photoelectron spectra under reaction conditions reveal that gold is reduced on CeO2, enabling direct H2 activation, but oxidized on In2O3, leading to decreased activity of Au/In2O3 compared to bare In2O3. At elevated temperatures, the catalytic activity of the In2O3 catalysts strongly increases as a result of facilitated CO2 and (In2O3-based) H2 activation, while the catalytic activity of Au/CeO2 is limited by reoxidation by CO2. Our results underline the importance of operando studies for understanding metal-support interactions to enable a rational support selection in the future.

Versatile procedure for the correction of non-isochromatism in XPEEM spectroscopic imaging

Non-isochromatism in X-ray PhotoEmission Electron Microscopy (XPEEM) may result in unwanted artifacts especially when working with large field of views. The lack of isochromatism of XPEEM images may result from multiple factors, for instance the energy dispersion of the X-rays on the sample or the effect of one or more dispersive elements in the electron optics of the microscope, or the combination of both. In practice, the photon energy or the electron kinetic energy may vary across the image, complicating image interpretation and analysis. The effect becomes severe when imaging at low magnification upon irradiation with high energy photons. Such imaging demands for a large X-ray illuminating spot size usually achieved by opening the exit slit of the X-ray monochromator while reducing the monochromaticity of the irradiating light. However, we show that the effect is linear and can be fully removed. A versatile correction procedure is presented which leads to true monochromatic photoelectron images at improved signal-to-noise ratio. XPEEM data recorded at the nanospectroscopy beamline of the Elettra synchrotron radiation facility illustrate the working principle of the procedure. Also, reciprocal space XPEEM data such as angle-resolved photoelectron spectroscopy (ARPES) momentum plots suffer from linear energy dispersion artifacts which can be corrected in a similar way. Representative data acquired from graphene synthesized on copper by chemical vapor deposition prove the benefits of the correction procedure.

Real-Time Investigation of Sulfur Vacancy Generation and Passivation in Monolayer Molybdenum Disulfide via in situ X-ray Photoelectron Spectromicroscopy

Understanding the chemical and electronic properties of point defects in two-dimensional materials, as well as their generation and passivation, is essential for the development of functional systems, spanning from next-generation optoelectronic devices to advanced catalysis. Here, we use synchrotron-based X-ray photoelectron spectroscopy (XPS) with submicron spatial resolution to create sulfur vacancies (SVs) in monolayer MoS₂ and monitor their chemical and electronic properties in situ during the defect creation process. X-ray irradiation leads to the emergence of a distinct Mo 3d spectral feature associated with undercoordinated Mo atoms. Real-time analysis of the evolution of this feature, along with the decrease of S content, reveals predominant monosulfur vacancy generation at low doses and preferential disulfur vacancy generation at high doses. Formation of these defects leads to a shift of the Fermi level toward the valence band (VB) edge, introduction of electronic states within the VB, and formation of lateral pn junctions. These findings are consistent with theoretical predictions that SVs serve as deep acceptors and are not responsible for the ubiquitous n-type conductivity of MoS₂. In addition, we find that these defects are metastable upon short-term exposure to ambient air. By contrast, in situ oxygen exposure during XPS measurements enables passivation of SVs, resulting in partial elimination of undercoordinated Mo sites and reduction of SV-related states near the VB edge. Correlative Raman spectroscopy and photoluminescence measurements confirm our findings of localized SV generation and passivation, thereby demonstrating the connection between chemical, structural, and optoelectronic properties of SVs in MoS₂.

Formation of a two-dimensional oxide via oxidation of a layered material

We investigate the oxidation mechanism of the layered model system GeAs. In situ X-ray photoelectron spectroscopy experiments performed by irradiating an individual flake with synchrotron radiation in the presence of oxygen show that while As leaves the GeAs surface upon oxidation, a Ge-rich ultrathin oxide film is being formed in the topmost layer of the flake. We develop a theoretical model that supports the layer-by-layer oxidation of GeAs, with a logarithmic kinetics. Finally, assuming that the activation energy for the oxidation process changes linearly with coverage, we estimate that the activation energy for As oxidation is almost twice that for Ge at room temperature.

The rise of the electrochemical NAPXPS operated in the soft X-ray regime exemplified in the oxygen evolution reaction on IrOx electrocatalysts

Photoelectron spectroscopy offers detailed information about of the electronic structure and chemical composition of surfaces owing to the short distance that the photoelectrons can escape from a dense medium. Unfortunately,...

The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe1- Cox O3 Perovskites

Perovskites are interesting oxidation catalysts due to their chemical flexibility enabling the tuning of several properties. In this work, we synthesized LaFe_1−xCo_xO₃ catalysts by co‐precipitation and thermal decomposition, characterized them thoroughly and studied their 2‐propanol oxidation activity under dry and wet conditions to bridge the knowledge gap between gas and liquid phase reactions. Transient tests showed a highly active, unstable low‐temperature (LT) reaction channel in conversion profiles and a stable, less‐active high‐temperature (HT) channel. Cobalt incorporation had a positive effect on the activity. The effect of water was negative on the LT channel, whereas the HT channel activity was boosted for x>0.15. The boost may originate from a slower deactivation rate of the Co³⁺ sites under wet conditions and a higher amount of hydroxide species on the surface comparing wet to dry feeds. Water addition resulted in a slower deactivation for Co‐rich catalysts and higher activity in the HT channel state.

Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon

Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.

Method for the Manual Analysis of Moiré Structures in STM images

A method is presented to manually determine the lattice parameters of commensurate hexagonal moiré structures resolved by STM. It solves the problem that lattice parameters of moiré structures usually cannot be determined by inspection of an STM image, so that computer-based analyses are required. The lattice vector of a commensurate moiré structure is a sum of integer multiples both of the two basis vectors of the substrate and of the adsorbed layer. The method extracts the two factors with respect to the adsorbed layer from an analysis of the Fourier transform of an STM image. These two factors are related to the two factors with respect to the substrate layer. Using the cell augmentation method, six possible moiré structures are identified by algebra. When the orientation and lattice constant of the substrate are roughly known, this information is usually sufficient to determine a unique moiré structure and its lattice parameters.

Electron and X-ray Focused Beam-Induced Cross-Linking in Liquids: Toward Rapid Continuous 3D Nanoprinting and Interfacing using Soft Materials

Multiphoton polymer cross-linking evolves as the core process behind high-resolution additive microfabrication with soft materials for implantable/wearable electronics, tissue engineering, microrobotics, biosensing, drug delivery, etc. Electrons and soft X-rays, in principle, can offer even higher resolution and printing rates. However, these powerful lithographic tools are difficult to apply to vacuum incompatible liquid precursor solutions used in continuous additive fabrication. In this work, using biocompatible hydrogel as a model soft material, we demonstrate high-resolution in-liquid polymer cross-linking using scanning electron and X-ray microscopes. The approach augments the existing solid-state electron/X-ray lithography and beam-induced deposition techniques with a wider class of possible chemical reactions, precursors, and functionalities. We discuss the focused beam cross-linking mechanism, the factors affecting the ultimate feature size, and layer-by-layer printing possibilities. The potential of this technology is demonstrated on a few practically important applications such as in-liquid encapsulation of nanoparticles for plasmonic sensing and interfacing of viable cells with hydrogel electrodes.

Crystal Orientation Dependent Oxidation Modes at the Buried Graphene-Cu Interface

We combine spatially resolved scanning photoelectron spectroscopy with confocal Raman and optical microscopy to reveal how the oxidation of the buried graphene-Cu interface relates to the Cu crystallographic orientation. We analyze over 100 different graphene covered Cu (high and low index) orientations exposed to air for 2 years. Four general oxidation modes are observed that can be mapped as regions onto the polar plot of Cu surface orientations. These modes are (1) complete, (2) irregular, (3) inhibited, and (4) enhanced wrinkle interface oxidation. We present a comprehensive characterization of these modes, consider the underlying mechanisms, compare air and water mediated oxidation, and discuss this in the context of the diverse prior literature in this area. This understanding incorporates effects from across the wide parameter space of 2D material interface engineering, relevant to key challenges in their emerging applications, ranging from scalable transfer to electronic contacts, encapsulation, and corrosion protection.

Highlighting the Dynamics of Graphene Protection toward the Oxidation of Copper Under Operando Conditions

We performed spatially resolved near-ambient-pressure photoemission spectromicroscopy on graphene-coated copper in operando under oxidation conditions in an oxygen atmosphere (0.1 mbar). We investigated regions with bare copper and areas covered with mono- and bi-layer graphene flakes, in isobaric and isothermal experiments. The key method in this work is the combination of spatial and chemical resolution of the scanning photoemission microscope operating in a near-ambient-pressure environment, thus allowing us to overcome both the material and pressure gap typical of standard ultrahigh-vacuum X-ray photoelectron spectroscopy (XPS) and to observe in operando the protection mechanism of graphene toward copper oxidation. The ability to perform spatially resolved XPS and imaging at high pressure allows for the first time a unique characterization of the oxidation phenomenon by means of photoelectron spectromicroscopy, pushing the limits of this technique from fundamental studies to real materials under working conditions. Although bare Cu oxidizes naturally at room temperature, our results demonstrate that such a graphene coating acts as an effective barrier to prevent copper oxidation at high temperatures (over 300 °C), until oxygen intercalation beneath graphene starts from boundaries and defects. We also show that bilayer flakes can protect at even higher temperatures. The protected metallic substrate, therefore, does not suffer corrosion, preserving its metallic characteristic, making this coating appealing for any application in an aggressive atmospheric environment at high temperatures.

Fluorescence in situ hybridization of Microcystis strains producing microcystin using specific mRNA probes

Cyanobacteria are ubiquitous micro-organisms that can produce toxic compounds, the cyanotoxins. The monitoring of such producers in the environment is of prime importance for human health. An attractive technology for such monitoring is fluorescence in situ hybridization (FISH), which allows the detection and enumeration of environmental micro-organisms. We present here the application of tyramide signal amplification fluorescence in situ hybridization (TSA-FISH) to the detection of microcystin-producing Microcystis strains. We used a 16S rRNA-specific probe, MICR3, to specifically label and observe by epifluorescence microscopy Microcystis aeruginosa strains. Using confocal laser scanning microscopy and a specific probe, MCYA, targeting the mcyA mRNA we have labelled M. aeruginosa PCC 7806, which produces microcystins. Microcystis aeruginosa PCC 7005 which does not produce microcystins is not labelled by this probe. Furthermore, we show here that this specific mRNA labelling in M. aeruginosa PCC 7806 is enhanced in cells illuminated for 1 h just after a dark period of cultivation of 24 h, conditions in which the mcyA gene is up regulated. The data presented here might be applicable to the monitoring of toxic Microcystis strains in the environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cyanobacteria producing toxic compounds (cyanotoxins) are present in the environment and in water bodies. Their presence poses a threat on human and animal health. It is thus important to detect, identify and enumerate these toxic Cyanobacteria. Using tyramide signal amplification fluorescence in situ hybridization (TSA-FISH) and specific probes, with confocal laser scanning microscopy, we have specifically detected Microcystis strains producing microcystin toxins. The data presented here might be applied to the monitoring of water bodies at early stages and all along the formation of Microcystis blooms.

Congenital Hypothyroidism Long-Term Follow-up Project: Navigating the Rough Waters of a Multi-Center, Multi-State Public Health Project

The Region 4 Midwest Genetics Collaborative, made up of seven regional states (Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio, and Wisconsin), brought together pediatric endocrinologists, state laboratory experts, public health follow-up specialists, and parents of children with congenital hypothyroidism (CH) to identify the three-year follow-up management and education patterns of primary care clinicians and pediatric endocrinologists in the care of children diagnosed with CH by state newborn screening (NBS) programs. Among a number of challenges, each state had different NBS methods, data systems, public health laws, and institutional review board (IRB) requirements. Furthermore, the diagnosis of CH was complicated by the timing of the NBS sample, the gestational age, weight, and co-morbidities at delivery. There were 409 children with CH identified through NBS in 2007 in the seven state region. The clinician of record and the parents of these children were invited to participate in a voluntary survey. Approximately 64 % of clinician surveys were collected with responses to questions relating to treatment, monitoring practices, educational resources, genetic counseling, and services provided to children with confirmed CH and their families. Nearly one-quarter (24 %) of parents surveyed responded to questions relating to treatment, education, genetic counseling, resources, and services they received or would like to receive. De-identified data from six of the seven states were compiled for analysis, with one state being unable to obtain IRB approval within the study timeline. The data from this collaborative effort will improve state follow-up programs and aid in developing three-year follow-up guidelines for children diagnosed with CH. To aid in the facilitation of similar public health studies, this manuscript highlights the challenges faced, and focuses on the pathway to a successful multi-state public health endeavor.

High-temperature scanning tunneling microscopy study of the ordering transition of an amorphous carbon layer into graphene on ruthenium(0001)

The ordering transition of an amorphous carbon layer into graphene was investigated by high-temperature scanning tunneling microscopy. A disordered C layer was prepared on a Ru(0001) surface by chemical vapor deposition of ethylene molecules at ~660 K. The carbon layer grows in the form of dendritic islands that have almost the same density as graphene. Upon annealing of the fully covered surface, residual hydrogen desorbs and a coherent but still disordered carbon layer forms, with almost the same carbon coverage as in graphene. The ordering of this layer into graphene at 920 to 950 K was monitored as a function of time. A unique mechanism was observed that involves small topographic holes in the carbon layer. The holes are mobile, and on the trajectories of the holes the disordered carbon layer is transformed into graphene. The transport of C atoms across the holes or along the hole edges provides a low-energy pathway for the ordering transition. This mechanism is prohibited in a dense graphene layer, which offers an explanation for the difficulty of removing defects from graphene synthesized by chemical methods.

Poly[[μ-1,4-anhydro-erythritolato-di-μ-aqua-sodium(I)] monohydrate]

In the title compound, {[Na(C(4)H(7)O(3))(H(2)O)(2)]·H(2)O}(n), the sodium ion is octa-hedrally coordinated by two bridging 1,4-anhydro-erythritolate ligands, unexpectedly coordinated by the ring oxygen and four water ligands. This bonding pattern leads to one-dimensional anti-tactical polymeric chains along [010]. One of the exocyclic O atoms of the anhydro-erythritolate group is an acceptor in four hydrogen bonds, giving further evidence that it is deprotonated.

Ab initio study of the uranyl oxide hydrates: a proton transfer mediated by water

We present a first-principles study of the UO(3)·n(H(2)O) uranyl oxide hydrates, namely, schoepite (n = 2.25), metaschoepite (n = 2) and dehydrated metaschoepite (n = 1.75), which appear as the alteration U(VI) products of aqueous corrosion of nuclear fuel. For these compounds, the calculated enthalpy of formation is in good agreement with calorimetry and solubility measurements. We discuss the key electronic state factors behind the phase stability of uranyl oxide hydrates. An unexplored proton-transfer mechanism, which produces the H(3)O hydronium ions in UO(3)·nH(2)O, has been studied using ab initio molecular dynamics simulations at room temperature. For the hydronium ion, a very short lifetime of around 20 fs has been suggested.

High-power, longitudinally fiber-pumped, passively Q-switched Nd:YAG oscillator-amplifier

A longitudinally fiber-pumped, passively Q-switched Nd:YAG laser oscillator-power amplifier system is reported with which a maximum pulse energy of 68 mJ was achieved at high pulse stability, beam quality, and efficiency. Therefore, a compact fiber-coupling interface was developed for stacked arrays of quasi-cw diode lasers, providing a pump power of 1 kW at the fiber end.

Autologe Chondrozytentransplantation zur Behandlung von Knorpeldefekten des Kniegelenks

BACKGROUND

Currently the use of autologous chondrocytes as a cartilage-repair procedure for the repair of injured articular cartilage of the knee joint, is recommended.

METHODS

This review presents the technique of autologous chondrocyte transplantation (ACT) and their modifications as matrix-associated autologous chondrocyte transplantation (MACT). Beside the surgical procedure the experimental and clinical results are discussed. Furthermore the major complications and the indication guidelines are presented.

RESULTS

Articular cartilage in adults has a poor ability to self-repair after a substantial injury. Surgical therapeutic efforts in treating cartilage defects have focused on bringing new cells capable of chondrogenesis into the lesions. With ACT good to excellent clinical results are seen in isolated posttraumatic lesions of the knee joint in the younger patient with the formation of hyaline-like repair tissue. The major complications are periosteal hypertrophy, delamination of the transplant, arthrofibrosis and transplant failure. The current limitations include osteoarthritic defects and higher patient age.

CONCLUSION

With the right indication and operative technique ACT is an effective and save option for the treatment of large full thickness cartilage defect of the knee joint.

Efficient, multiwatt, continuous-wave laser operation on the (4)F((3/2))-(4)I((9/2)) transitions of Nd:YVO(4) and Nd:YAG

We report multiwatt, diode-pumped cw operation on the (4)F(3/2)-(4)I(9/2) laser transition at 914.5 nm in Nd:YVO(4), for which an output power of 3.0 W and a slope of efficiency of 22.8% were achieved. For the corresponding laser transition of Nd:YAG at 946 nm an output power of 5.35 W and a slope efficiency of 40.2% were measured. By intracavity frequency doubling, an output power of 1.5 W at 473 nm was generated.

Patients report positive nutrition counseling outcomes

OBJECTIVE

Assess outcomes of patient nutrition counseling.

DESIGN

A descriptive study based on the results of a telephone interview performed 2 to 8 weeks after counseling.

SUBJECTS/SETTING

Subjects were 400 adult patients referred for nutrition counseling at 2 academic health centers. Of these, 274 patients received nutrition counseling during hospitalization and 126 as outpatients.

STATISTICAL ANALYSIS

Descriptive statistics were used to summarize data and the Mann-Whitney U statistic and logistic regressions were used to test significant differences (P < .05) between inpatient and outpatient counseling outcomes.

RESULTS

Most patients (83%) gave a partial or full description of their diet modifications and 79% had a moderate or good understanding of their diet. Most patients reported that the dietitian's advice was suited to their special needs (88%) and that they knew what to eat (83%). A majority (62%) had made dietary changes, but 17% said they had had trouble changing their diets as suggested. After talking with a dietitian, 57% felt better emotionally, 37% felt better physically, 64% felt in control of their condition, and 43% noticed improved health indicators. Initial analysis indicated that outpatients reported better outcomes than inpatients; further analysis showed that these differences could be attributed to younger ages among the outpatient sample.

APPLICATIONS/CONCLUSIONS

Patient nutrition counseling has positive outcomes. Therefore, key counseling points should be introduced or reinforced in inpatient settings, in conjunction with multiple-session protocols during the pre- and/or posthospitalization continuum of care. Dietitians, managers, administrators, and credentialing agencies should work together to secure and promote the necessary physical, personnel, and financial resources to make this happen.

Direct monitoring of capillary perfusion following normovolemic hemodilution in an experimental skin-flap model

The effects of normovolemic hemodilution on skin flap survival are studied in a recently developed skin-flap model (homozygous hairless mouse ear) in which nutritional capillary flow is monitored directly by means of intravital microscopy from the time of flap creation throughout the establishment of necrosis. Two diluting agents (dextran 60 and hydroxyethyl starch 200) are utilized. Our quantitative findings demonstrate that the amount of nonperfused tissue following flap creation in both the dextran (n = 23) and starch (n = 13) groups was significantly decreased as compared with controls (n = 19). Our qualitative observations suggest that improved hemorrheologic properties at the microcirculatory level are responsible for the observed decreased necrosis. Various mechanisms by which hemodilution may act to prevent necrosis are discussed.

Pseudocolor display of regional organ blood flow determined by means of the radioactive microsphere technique

The measurement of regional blood flow (RBF) by means of the radioactive microsphere method yields large sets of raw data. In order to display this large volume of data, we have developed a program which provides the user with a graphical illustration of RBF in different organs (e.g., heart, kidney, brain) using various projections and sections. RBF is visualized by a pseudocolor representation. This set-up enables the user to perform a semiquantitative analysis of RBF and provides a tool for the compact representation of the spatial distribution of RBF values in different parts and layers of the organs being studied. The program runs on a standard microcomputer.

Analogues and derivatives of tenoxicam. 1. Synthesis and antiinflammatory activity of analogues with different residues on the ring nitrogen and the amide nitrogen

The synthesis of tenoxicam, 4-hydroxy-2-methyl-N-2-pyridyl-2H-thieno[2,3-e]-1,2-thiazine-3-carboxami de 1,1-dioxide (1e), and of the analogues with various residues on the ring nitrogen and the amide nitrogen is described. This new class of "oxicams" has pronounced antiinflammatory and analgesic properties. The very specific structure-activity relationship of isomeric and isosteric groups at the amide nitrogen has been evaluated. The substituent in position 2 also has a great influence on the pharmacological properties. Tenoxicam is presently undergoing clinical trials.

Magnetic resonance imaging compared with computed tomography in adrenoleukodystrophy

Adrenoleukodystrophy was diagnosed in two siblings and confirmed by analysis of very-long-chain fatty acids in skin fibroblasts. Both boys had computed tomograms (CTs) and magnetic resonance imaging (MRI) of the brain. In the most severely affected child, the CT and MRI examinations were both abnormal, but in the other child, the CT was mildly abnormal but the MRI was unequivocally abnormal. This suggests that MRI is more sensitive than CT in detecting the acute demyelinating changes of adrenoleukodystrophy and, in conjunction with very-long-chain fatty acid analysis, should be useful in screening unaffected or mildly affected siblings of patients with this disease.

[Disintegration of enzymatically pretreated cartilage after subcutaneous implantation]

The influence of previous digestion of cartilage proteoglycans and collagen on cartilage resorption in implants was studied. After implantation for 1, 2, 3, and 4 weeks the morphology of the implants was studied by light microscopy. It was found that enzymatic treatment of cartilage with hyaluronidase, collagenase as well as the combination of both enzymes slightly increased the resorption by granulation tissue. From these studies it can be concluded, that cartilage depletion of proteoglycans facilitates cartilage degradation, however it is not the only reason for the severe cartilage destruction seen in arthritic joints.