ZnO is a CO2-selective steam reforming catalyst

AbstractZnO was tested as possible methanol and – since formaldehyde is one of the key intermediates in methanol conversion reactions – also as formaldehyde steam reforming catalyst. Catalytic experiments in a batch as well as a flow reactor resulted in highly selective steam reforming, though at low specific activities, of formaldehyde and methanol over ZnO toward CO2 (selectivity of 95–99.6%). Comparison of the behavior of ZnPd near-surface intermetallic phases, unsupported intermetallic ZnPd and supported ZnPd/ZnO catalysts reveals that formaldehyde is formed from methanol in parallel with CO2 on the former, while on unsupported intermetallic ZnPd and ZnO-supported ZnPd, it is efficiently reacted toward CO2, thus, a beneficial role of ZnO in oxidizing formaldehyde-derived intermediates toward CO2 is evident

Summability of Superstring Theory

Several arguments are given for the summability of the superstring perturbation series. Whereas the Schottky group coordinatization of moduli space may be used to provide refined estimates of large-order bosonic string amplitudes, the super-Schottky group variables define a measure for the supermoduli space integral which leads to upper bounds on superstring scattering amplitudes.Comment: 11 pages, TeX. A remark about C-cycles and dividing cycles and two references have been added to the pape

A quantitative microscopic view on the gas-phase-dependent phase transformation from tetragonal to monoclinic ZrO2

ZrO2 is a versatile material with diverse applications, including structural ceramics, sensors, and catalysts. The properties of ZrO2 are largely determined by its crystal structure, which is temperature- and atmosphere dependent. Thus, this work focuses on a quantitative analysis of the temperature- and gas atmosphere-dependent phase transformation of tetragonal t-ZrO2 into monoclinic m-ZrO2 during heating–cooling cycles from room temperature to 1273 K. Synchrotron-based in situ X-ray diffraction (XRD) studies in gas atmospheres of different reduction strengths, namely, 5 vol% H2/Ar, He, CO2, and air, revealed a stabilizing effect of inert and reductive environments, directly yielding different temperature onsets in the phase transformation during cooling (i.e., 435, 510, 710, and 793 K for 5 vol% H2/Ar, He, CO2, and air, respectively). Rietveld refinement shows a direct influence of the atmosphere on grain size, unit cell, and weight fraction of both polymorphs in the product composite matrix. The tetragonal-to-monoclinic (t–m) phase transformation is suppressed in the sample heated only up to ∼850 K, independent of the gas atmosphere. The results of ex situ XRD, transmission electron microscopic, electron paramagnetic resonance, and oxygen titration experiments confirmed that the phase transformation is accompanied by a change in the crystallite/particle size and the amount of lattice defects (i.e., oxygen vacancy). Due to the different onset temperatures, a complex interplay between kinetic limitations of phase transformation and grain sintering yields different pathways of the phase transformation and, eventually, very different final crystallite sizes of both t-ZrO2 and m-ZrO2

Surface chemistry and stability of metastable corundum-type In2O3

To account for the explanation of an eventual sensing and catalytic behavior of rhombohedral In2O3 (rh-In2O3) and the dependence of the metastability of the latter on gas atmospheres, in situ electrochemical impedance spectroscopic (EIS), Fourier-transform infrared spectroscopic (FT-IR), in situ X-ray diffraction and in situ thermogravimetric analyses in inert (helium) and reactive gases (hydrogen, carbon monoxide and carbon dioxide) have been conducted to link the gas-dependent electrical conductivity features and the surface chemical properties to its metastability towards cubic In2O3. In particular, for highly reducible oxides such as In2O3, for which not only the formation of oxygen vacancies, but deep reduction to the metallic state (i.e. metallic indium) also has to be taken into account, this approach is imperative. Temperature-dependent impedance features are strongly dependent on the respective gas composition and are assigned to distinct changes in either surface adsorbates or free charge carrier absorbance, allowing for differentiating and distinguishing between bulk reduction-related features from those directly arising from surface chemical alterations. For the measurements in an inert gas atmosphere, this analysis specifically also included monitoring the fate of differently bonded, and hence, differently reactive, hydroxyl groups. Reduction of rh-In2O3 proceeds to a large extent indirectly via rh-In2O3 → c-In2O3 → In metal. As deduced from the CO and CO2 adsorption experiments, rhombohedral In2O3 exhibits predominantly Lewis acidic surface sites. The basic character is less pronounced, directly explaining the previously observed high (inverse) water–gas shift activity and the low CO2 selectivity in methanol steam reforming.DFG, SPP 1415, Kristalline Nichtgleichgewichtsphasen - Präparation, Charakterisierung und in situ-Untersuchung der Bildungsmechanisme

Do Patients and Oncologists Discuss the Cost of Cancer Treatment? An Observational Study of Clinical Interactions Between African American Patients and Their Oncologists

PURPOSE: Financial toxicity negatively affects patients with cancer, especially racial/ethnic minorities. Patient-oncologist discussions about treatment-related costs may reduce financial toxicity by factoring costs into treatment decisions. This study investigated the frequency and nature of cost discussions during clinical interactions between African American patients and oncologists and examined whether cost discussions were affected by patient sociodemographic characteristics and social support, a known buffer to perceived financial stress. Methods Video recorded patient-oncologist clinical interactions (n = 103) from outpatient clinics of two urban cancer hospitals (including a National Cancer Institute-designated comprehensive cancer center) were analyzed. Coders studied the videos for the presence and duration of cost discussions and then determined the initiator, topic, oncologist response to the patient\u27s concerns, and the patient\u27s reaction to the oncologist\u27s response. RESULTS: Cost discussions occurred in 45% of clinical interactions. Patients initiated 63% of discussions; oncologists initiated 36%. The most frequent topics were concern about time off from work for treatment (initiated by patients) and insurance (initiated by oncologists). Younger patients and patients with more perceived social support satisfaction were more likely to discuss cost. Patient age interacted with amount of social support to affect frequency of cost discussions within interactions. Younger patients with more social support had more cost discussions; older patients with more social support had fewer cost discussions. CONCLUSION: Cost discussions occurred in fewer than one half of the interactions and most commonly focused on the impact of the diagnosis on patients\u27 opportunity costs rather than treatment costs. Implications for ASCO\u27s Value Framework and design of interventions to improve cost discussions are discussed

O- vs. N-protonation of 1-dimethylaminonaphthalene-8-ketones: formation of a peri N–C bond or a hydrogen bond to the pi-electron density of a carbonyl group

X-ray crystallography and solid-state NMR measurements show that protonation of a series of 1-dimethylaminonaphthalene-8-ketones leads either to O protonation with formation of a long N–C bond (1.637–1.669 Å) between peri groups, or to N protonation and formation of a hydrogen bond to the π surface of the carbonyl group, the latter occurring for the larger ketone groups (C(O)R, R = t-butyl and phenyl). Solid state 15N MAS NMR studies clearly differentiate the two series, with the former yielding significantly more deshielded resonances. This is accurately corroborated by DFT calculation of the relevant chemical shift parameters. In the parent ketones X-ray crystallography shows that the nitrogen lone pair is directed towards the carbonyl group in all cases

Formation and Stability of small well-defined Cu- and Ni oxide particles

Well-defined and -structured Cu/Cu2O and Ni/NiO composite nanoparticles have been prepared by physical-vapor deposition on vacuum-cleaved NaCl(001) single crystal facets. Epitaxial growth has been observed due to the close crystallographic matching of the respective cubic crystal lattices. Distinct particle morphologies have only been obtained for the Ni/NiO particles, comprising truncated half-octahedral, rhombohedral- and pentagonal-shaped outlines. Oxidation of the particles in the temperature range 473-673 K in both cases led to the formation of well-defined CuO and NiO particles with distinct morphologies. Whereas CuO possibly adopts its thermodynamical equilibrium shape, NiO formation is accompanied by entering a Kirkendall-like state, that is, a hollow core-shell structure is obtained. The difference in the formation of the oxides is also reflected by their stability under reducing conditions. CuO transforms back to a polycrystalline mixture of Cu metal, Cu2O and CuO after reduction in hydrogen at 673 K. In contrast, as expected from theoretical stability considerations, the formation of the hollow NiO structure is reversed upon annealing in hydrogen at 673 K and moreover results in the formation of a Ni-rich silicide structure Ni3Si2. The discussed systems present a convenient way to tackle and investigate various problems in nanotechnology or catalysis, including phase transformations, establishing structure/activity relationships or monitoring intermetallic particles, starting from well-defined and simple models.(VLID)2852386Accepted versio

Electron microscopy investigations of metal-support interaction effects in M/Y2O3 and M/ZrO2 thin films (M=Cu, Ni)

Model systems of the clean and pure oxides Y2O3 and ZrO2, as well as Cu/Cu2O and Ni/NiO particles embedded in the respective oxides have been used to study the reduction behavior of the oxides and the eventually associated metal-support interaction effects in oxide-supported systems. Particular emphasis has also been given to the influence of the phase transformation in ZrO2-containing systems on metal-support interaction. Whereas Y2O3 has been found to be an outstandingly structurally and thermally stable oxide even upon reduction in hydrogen up to 1073 K, ZrO2 was found to undergo a series of phase transformations from amorphous ZrO2 to polycrystalline tetragonal ZrO2 (673 K) and subsequently to monoclinic ZrO2 (above 873 K). Both phase transformations were found to be basically dependent on gas partial pressure and annealing rate. However, substantial reduction of the oxides did not take place during the phase transformations. In turn, both Cu- and Ni-containing systems were not observed to be substantially affected by any (strong) metal-support interaction effects such as encapsulation by sub-stoichiometric oxides or reductive formation of intermetallic phases, at least up to temperatures of 1073 K. Equally, for the ZrO2-containing systems, also the phase transformations occurring at elevated temperatures did not cause structural or thermo-chemical alterations of the Cu or Ni-particles. Differences in the metal-support interaction between Cu- and Ni-particles have only been obtained in the structural “reference” systems, that is, if supported on SiO2. Whereas Cu/Cu2O particles on SiO2 are basically unaffected by the reductive treatment at elevated temperatures, a Ni3Si2 intermetallic phase is formed if SiO2-supported Ni/NiO particles are treated in hydrogen at 673 K and above.(VLID)2852394Accepted versio