10,000 publications from this institution
PdII/PdIV or PdII/Pd0? The unusual PdII catalyst 1 was reduced to a Pd0 complex by reaction with an amine and a base. β-Hydrogen elimination and subsequent CH bond-forming reductive elmination generate a coordinated tris(o-tolyl)phosphane. The same palladium(II) metallacycle was reduced to Pd0 in a cross-coupling reaction by CC bond-forming reductive elimination to form coordinated P(oTol)2-(C6H4CH2Ar). Thus, these compounds can react by a PdII/Pd0-containing catalytic cycle.
Conversion of CO<sub>2</sub> to reduced products is a promising route to alleviate irreversible climate change. Here we report the synthesis of a Co-based phthalocyanine with pyridine moieties (CoPc-Pyr), which is supported on a carbon electrode and shows Faradaic efficiency ∼90% for CO at 490 mV of overpotential (-0.6 V vs reversible hydrogen electrode (RHE)). In addition, its catalytic activity at -0.7 V versus RHE surpasses other Co-based molecular and metal-organic framework catalysts for CO<sub>2</sub> reduction at this bias. Density functional theory calculations show that pyridine moieties enhance CO<sub>2</sub> adsorption and electron affinity of the Co center by an inductive effect, thus lowering the overpotential necessary for CO<sub>2</sub> conversion. Our study shows that CoPc-Pyr reduces CO<sub>2</sub> at lower overpotential and with higher activity than noble metal electrodes, such as silver.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
A new measure of earthquake demand, the drift spectrum has been developed as an adjunct to the response spectrum, a central concept in earthquake engineering, in calculating the internal deformations of a structure due to near-fault ground motions with pronounced coherent pulses in the velocity and displacement histories. Compared in this paper are certain aspects of the elastic structural response to near-fault and far-fault ground motions. It is demonstrated that (1) the difference between drift and response spectra are not unique to near-fault ground motions; these differences simply reflect higher-mode response, which is larger due to near-fault ground motions; (2) response spectrum analysis (RSA) using existing modal combination rules can provide an estimate of structural response that is accurate to a useful degree; (3) these modal combination rules are similarly accurate for near-fault and far-fault ground motions although the underlying assumptions are not satisfied by near-fault excitations; and (4) RSA is preferable over the drift spectrum in computing structural response because it represents standard engineering practice and is applicable to a wide variety of structures.
Continuous piecewise-linear functions from R/sup n/ to R/sup m/ are analyzed in terms of the dimensions of their domain space and of degenerate kth-order intersections of region boundaries. The theory developed demonstrates how these two quantities are connected. Moreover, the exact number of independent parameters is demonstrated for boundary configurations containing degenerate intersections of arbitrary orders.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
We compare the nature of the band bending under GaAs surfaces prepared by alkaline sulfides [Na2S⋅9H2O, (NH4)2S] with that under oxidized GaAs surfaces. We make the point that Fermi level pinning implies band bending, but band bending does not necessarily imply ‘‘pinning.’’ In either case, even weak light illumination substantially flattens the bands. On ammonium sulfide treated surfaces the fixed and trapped charge density in the dark is only ∼5×1011 electrons/cm2, but these few states are mostly neutralized at low-level forward injection. This behavior should not be confused with Fermi level pinning.
Abstract The pit-to-crack transition of AISI 316LN stainless steel reinforcement exposed to stress corrosion cracking (SCC) in chlorides contaminated alkaline environment, was studied by a combination of slow strain rate testing (SSRT) and electrochemical impedance spectroscopy (EIS). The phase angle shift (Δφ) obtained by EIS at low frequencies was utilized to determine the pit-to-crack transition, differentiating from crack nucleation and propagation as identified by shifts in the frequency range of phase angle ( θ ) peaks. The pit-to-crack transition was developed once the maximum θ value shifted from the low to high frequencies. EIS analysis was corroborated by assessment of repassivation rates and pit growth, in addition to calculating $${\Delta G}^{{\rm{\gamma }}\to {\rm{\alpha }}{\rm{\mbox{'}}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:mi>G</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>γ</mml:mi> <mml:mo>→</mml:mo> <mml:mi>α</mml:mi> <mml:mi>’</mml:mi> </mml:mrow> </mml:msup> </mml:math> . Crack nucleation at lath martensite developed transgranular SCC. Strain-induced martensitic transformation was associated with the brittle failure of AISI 316LN stainless steel, where α’–martensite phase preferentially incubated the pit, and favored crack nucleation, thus promoting pit-to-crack transition.
As measured by these scales, integration seems to be related to the presence of practice systems components of the chronic care model, although simply having the potential for integration (structure and finance) is much less strongly related than evidence of functional integration.
Rational curves and splines are one of the building blocks of computer graphics and geometric modeling. Although a rational curve is more flexible than its polynomial counterpart, many properties of polynomial curves are not applicable to it. For this reason it is very useful to know if a curve presented as a rational space curve has a polynomial parametrization. In this paper, we present an algorithm to decide if a polynomial parametrization exists, and to compute the parametrization. In algebraic geometry it is known that a rational algebraic curve is polynomially parametrizable if it has one place at infinity. This criterion has been used in earlier methods to test polynomial parametrizability of space curves. These methods project the curve into the plane and test parametrizability there. But this gives only a sufficient condition for the original curve. In this paper we give a simple condition which is both necessary and sufficient for polynomial parametrizability. The calculation of the polynomial parametrization is simple, and involves only a rational reparametrization of the curve.
In this work, we study the mechanical behavior of solids with microstructure using the framework of Cosserat elasticity with a single unit director. This formulation captures the coupling between deformation and orientational fields that arises in many structured materials. To compute equilibrium configurations of such media, we develop two complementary computational approaches: a finite element formulation based on variational principles and a neural network-based solver that directly minimizes the total potential energy. The neural architecture is constructed to respect the fundamental kinematic structure of the theory. In particular, it enforces frame invariance of the energy, satisfies the unit-length constraint on the director field, and represents deformation and director fields through separate networks to preserve their kinematic independence in the variational setting. Beyond satisfying balance laws, however, physically admissible solutions must also correspond to stable energy minimizers. To assess this requirement, we derive the quasiconvexity condition, rank-one convexity condition, and the Legendre-Hadamard inequalities for the Cosserat model and formulate them in a manner suitable for evaluating neural network predictions. These necessary stability conditions provide a physics-based validation framework: network outputs that violate these necessary conditions cannot correspond to stable energy minimizers and can therefore be rejected. In this way, we integrate classical variational stability theory with modern machine-learning solvers, establishing a computational workflow in which equilibrium solutions are not only learned but also assessed for energetic consistency.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
