The surface structure of catalysts activated with hydrogen donors as elucidated by multinuclear solid-state NMR

¹H, ²⁷Al and ³¹P MAS, and ¹³C and ²⁹Si CP/MAS NMR spectroscopies, were used to characterize catalysts of Pd supported on various solids including SiO₂, AlPO₄ and Mg₃(PO₄)₂ that were activated with the chiral hydrogen-donor limonene. The above-mentioned techniques were used to check for the formation of an organopalladium complex between Pd²⁺ atoms and the olefin bonds in the limonene molecule on the catalyst surface. The results are compared with those obtained for catalysts activated in a hydrogen stream.     

Error estimates for ππ scattering threshold parameters in Chiral Perturbation Theory to two loops

Using the analysis of ChPT to two loops, we perform an error analysis of the threshold and low-energy parameters, based on the uncertainties for the one-loop low-energy parameters and the resonance saturation mechanism. Different sets of one-loop low-energy constants have been considered. Thus, the predictive power of the effective field theory, is quantified on the basis of the present experimental uncertainties. Communicated by W. Weise     

Fuzzy cross-efficiency evaluation: a possibility approach

Cross-efficiency evaluation is an extension of data envelopment analysis (DEA) aimed at ranking decision making units (DMUs) involved in a production process regarding their efficiency. As has been done with other enhancements and extensions of DEA, in this paper we propose a fuzzy approach to the cross-efficiency evaluation. Specifically, we develop a fuzzy cross-efficiency evaluation based on the possibility approach by Lertworasirikul et al. (Fuzzy Sets Syst 139:379–394, 2003a) to fuzzy DEA. Thus, a methodology for ranking DMUs is presented that may be used when data are imprecise, in particular for fuzzy inputs and outputs being normal and convex. We prove some results that allow us to define “consistent” cross-efficiencies. The ranking of DMUs for a given possibility level results from an ordering of cross-efficiency scores, which are real numbers. As in the crisp case, we also develop benevolent and aggressive fuzzy formulations in order to deal with the alternate optima for the weights.     

An investigation of fatigue and fretting in a dovetail joint

Specimens designed to reproduce the state of stress of the dovetail joint between blade and disk in a typical gas-turbine configuration have been tested in a 250-kN capacity biaxial fatigue machine. The materials tested were Ti-IMI 829 (disk and blade), Inco 901 and steel FV535 (blades only). The investigation highlights the importance of fretting at the disk/blade interface. A design parameter that combines fretting damage and peak stress is proposed as a basis for the life assessment of the joints.     

Açai (Euterpe oleracea Mart.) Seed Extract Induces ROS Production and Cell Death in MCF-7 Breast Cancer Cell Line

Euterpe oleracea Mart. (açai) is a native palm from the Amazon region. There are various chemical constituents of açai with bioactive properties. This study aimed to evaluate the chemical composition and cytotoxic effects of açai seed extract on breast cancer cell line (MCF-7). Global Natural Products Social Molecular Networking (GNPS) was applied to identify chemical compounds present in açai seed extract. LC-MS/MS and molecular networking were employed to detect the phenolic compounds of açai. The antioxidant activity of açai seed extract was measured by DPPH assay. MCF-7 breast cancer cell line viability was evaluated by MTT assay. Cell death was evaluated by flow cytometry and time-lapse microscopy. Autophagy was evaluated by orange acridin immunofluorescence assay. Reactive oxygen species (ROS) production was evaluated by DAF assay. From the molecular networking, fifteen compounds were identified, mainly phenolic compounds. The açai seed extract showed cytotoxic effects against MCF-7, induced morphologic changes in the cell line by autophagy and increased the ROS production pathway. The present study suggests that açai seed extract has a high cytotoxic capacity and may induce autophagy by increasing ROS production in breast cancer. Apart from its antioxidant activity, flavonoids with high radical scavenging activity present in açai also generated NO (nitric oxide), contributing to its cytotoxic effect and autophagy induction.     

Effects of Coke Deposits on the Catalytic Performance of Large Zeolite H‐ZSM‐5 Crystals during Alcohol‐to‐Hydrocarbon Reactions as Investigated by a Combination of Optical Spectroscopy and Microscopy

The catalytic activity of large zeolite H‐ZSM‐5 crystals in methanol (MTO) and ethanol‐to‐olefins (ETO) conversions was investigated and, using operando UV/Vis measurements, the catalytic activity and deactivation was correlated with the formation of coke. These findings were related to in situ single crystal UV/Vis and confocal fluorescence micro‐spectroscopy, allowing the observation of the spatiotemporal formation of intermediates and coke species during the MTO and ETO conversions. It was observed that rapid deactivation at elevated temperatures was due to the fast formation of aromatics at the periphery of the H‐ZSM‐5 crystals, which are transformed into more poly‐aromatic coke species at the external surface, preventing the diffusion of reactants and products into and out of the H‐ZSM‐5 crystal. Furthermore, we were able to correlate the operando UV/Vis spectroscopy results observed during catalytic testing with the single crystal in situ results.     

Application of Visible‐to‐UV Photon Upconversion to Photoredox Catalysis: The Activation of Aryl Bromides

The activation of aryl–Br bonds was achieved by sequential combination of a triplet–triplet annihilation process of the organic dyes, butane‐2,3‐dione and 2,5‐diphenyloxazole, with a single‐electron‐transfer activation of aryl bromides. The photophysical and chemical steps were studied by time‐resolved transient fluorescence and absorption spectroscopy with a pulsed laser, quenching experiments, and DFT calculations.     

Hylleraas–Configuration Interaction calculations on the 11S ground state of helium atom

Hylleraas–Configuration Interaction (Hy–CI) calculations on the ground 1¹S state of helium atom are presented using s-, p-, d-, and f-Slater orbitals of both real and complex form. Techniques of construction of adapted configurations, optimization of the orbital exponents, and structure of the wave function expansion are explored. A new method to evaluate the two-electron kinetic energy integrals occurring in the Hy–CI method has been tested in this work and compared with other methods. The non-relativistic Hy–CI energy values are ≈10 picohartree accurate, about 2.2 × 10^?6 cm^?1. The Hy–CI calculations are compared with Configuration Interaction (CI) and Hylleraas (Hy) calculations employing the same orbital basis set, same computer code, and same computer machines. The computational required times are reported.     

An augmented stress‐based mixed finite element method for the steady state Navier‐Stokes equations with nonlinear viscosity

A new stress‐based mixed variational formulation for the stationary Navier‐Stokes equations with constant density and variable viscosity depending on the magnitude of the strain tensor, is proposed and analyzed in this work. Our approach is a natural extension of a technique applied in a recent paper by some of the authors to the same boundary value problem but with a viscosity that depends nonlinearly on the gradient of velocity instead of the strain tensor. In this case, and besides remarking that the strain‐dependence for the viscosity yields a more physically relevant model, we notice that to handle this nonlinearity we now need to incorporate not only the strain itself but also the vorticity as auxiliary unknowns. Furthermore, similarly as in that previous work, and aiming to deal with a suitable space for the velocity, the variational formulation is augmented with Galerkin‐type terms arising from the constitutive and equilibrium equations, the relations defining the two additional unknowns, and the Dirichlet boundary condition. In this way, and as the resulting augmented scheme can be rewritten as a fixed‐point operator equation, the classical Schauder and Banach theorems together with monotone operators theory are applied to derive the well‐posedness of the continuous and associated discrete schemes. In particular, we show that arbitrary finite element subspaces can be utilized for the latter, and then we derive optimal a priori error estimates along with the corresponding rates of convergence. Next, a reliable and efficient residual‐based a posteriori error estimator on arbitrary polygonal and polyhedral regions is proposed. The main tools used include Raviart‐Thomas and Clément interpolation operators, inverse and discrete inequalities, and the localization technique based on triangle‐bubble and edge‐bubble functions. Finally, several numerical essays illustrating the good performance of the method, confirming the reliability and efficiency of the a posteriori error estimator, and showing the desired behavior of the adaptive algorithm, are reported. © 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 1692–1725, 2017     

The X‐ray photoelectron spectra of Ir,IrO2 and IrCl3 revisited

The X‐ray photoelectron spectra of metallic iridium and the technologically important iridium compounds, IrO₂ and IrCl₃, have been studied. The results not only improve the accuracy of published data but also expand the binding energy database of other iridium core‐levels. The difference between anhydrous and hydrated materials is explored, and the effect on curve‐fitting is discussed, together with the derivation of suitable line shapes for peak fitting of data acquired from a conventional monochromatic Al K_α X‐ray source. Copyright © 2017 John Wiley & Sons, Ltd.