Understanding the preferential oxidation of carbon monoxide (PrOx) using size‐controlled Au nanocrystal catalyst

Removing CO from hydrogen streams is an important industrial process. The catalytic preferential oxidation of CO (PrOx) is a promising method for CO removal, leaving the hydrogen concentration unchanged. Here, the effect of size and support on the gold‐catalyzed PrOx reaction using size‐controlled Au nanocrystals (NCs) is investigated. For all supports, Au NC sizes of 2–5 nm show the highest rates, whereas for larger sizes rates drop. Ceria‐supported Au shows by far the best performance. By analyzing the dependency of the reaction rate on the NC diameter, the most active centers for CO oxidation on Au/CeO₂ are Au⁺ corner atoms at the interface with the support, resulting in 2.1 nm Au NCs supported on ceria reaching full O₂ conversion and CO selectivity of about 50%. Therefore, it is suggested that increasing the fraction of Au‐ceria interface sites would lead to the best performing materials for this reaction. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3159–3167, 2018     

Crystal Structure and Computational Analysis of a Two-Dimensional Coordination Polymer,BiI<Subscript>3</Subscript>(DppeO<Subscript>2</Subscript>)<Subscript>3/2</Subscript>

Catena-poly[fac-triiodobismuth(III)-tris-(µ-ethane-1,2-diylbis(diphenylphosphane oxide-κ²O,O′))], a 2-D sheet network of BiI₃ was synthesized from BiI₃ and ethane-1,2-diylbis(diphenylphosphane oxide) (DppeO₂) in tetrahydrofuran. The crystal structure revealed a trigonal structure with three-fold symmetry at Bi. Bismuth centers show fac-BiI₃O₃ coordination, with Bi–I?=?2.9416(2) Å and Bi–O?=?2.4583(17) Å. The I–Bi–I and O–Bi–O angles (95.520(7)° and 79.04(6)°, respectively) indicate trigonal distortion in the Bi octahedron. Bridging DppeO₂ ligands centered on inversion centers give rise to a 2-D sheet polymer. The 8.3 Å thick sheets consist of three layers in a sandwich structure. The outer layers are composed of phenyl rings and BiI₃ groups with the iodide atoms pointing outward. The central layer consists of the O=PCH₂CH₂P=O bridging groups. Computational results suggest that semi-conducting behavior arises from Bi(III) centers. A halide to DppeO₂ π* transition is suggested by theoretical results.     

Preparation and Characterization of Conducting Systems based on EPDM/PE/PS‐co‐DVB/HSb

Summary: Blends of different compositions were prepared from: a thermoplastic elastomer (EPDM), a low density polyethylene (PE), a polystyrene crosslinked with a small amount of divinylbenzene (PS‐co‐DVB) and an inorganic proton conductor: antimonic acid (HSb). The blends obtained were sulfonated heterogeneously with chlorosulfonic acid and were then structurally and electrically characterized by means of the following techniques: differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), crystallization kinetics under non‐isothermal conditions and complex impedance spectroscopy.

Dynamic mechanical analysis for EPDM and EP‐3 blends series.     

The Short Message Service: Standards,infrastructure and innovation

The Short Message Service (SMS) is a teleservice developed by the Global System for Mobile Communication in the mid-1980s for second-generation mobile networks. SMS is made up of standards, protocols and infrastructure that make text messaging the most popular data service on mobile networks. The teleservice has been used in all subsequent generations of mobile telephony. This article discusses the development of the SMS teleservice standards (GSM 03.40), how it has influenced mobile telephony infrastructure, and how it remains a lasting communication innovation today. It historicizes text messaging standards and their technical realization by describing the network architecture and elements required for SMS transmission. This article illustrates how SMS standards and infrastructure represent a significant innovation to mobile telephony in the late twentieth century.     

Brewster's angle attenuator for terahertz pulses

A variable attenuator for terahertz (THz) pulses is developed on the basis of the change in reflectivity of lithium niobate wafers with incident angle in a Brewster configuration. We can vary the THz field transmission from 22% to 54%, a change of a factor of 2.5, while preserving the shape of the THz pulse spectrum. Changes in the THz spectrum are shown to be much smaller when the Brewster attenuator is used than when either the near-infrared pump power or the bias voltage on a THz photoconductive antenna is varied. The Brewster attenuator should prove especially useful for varying THz field strength in nonlinear optical studies that use broadband THz pulses.     

The use of intensity-dependent weight functions to “Weberize” $$L^2$$ L 2 -based methods of signal and image approximation

Optimization and Engineering - We consider the problem of modifying $$L^2$$ -based approximations so that they “conform” in a better way to Weber’s model of perception: Given a...     

A surrogate-based multiobjective metaheuristic and network degradation simulation model for robust toll pricing

Robust transportation network design problems generally rely on systems engineering methods that share common research gaps. First, problem sizes are constrained due to the use of multi-objective solution algorithms that are notoriously inefficient due to computationally expensive function evaluations. Second, link disruptions at a network level are difficult to model realistically. In this paper, a stochastic search metaheuristic based on radial basis functions is proposed for constrained multiobjective problems. It is proven to converge, and compared with conventional metaheuristics for four representative test problems. A scenario simulation method based on multivariate Bernoulli random variables that accounts for correlations between link failures is proposed to sample scenarios for a mean-variance toll pricing problem. Four tests are conducted on the classical Sioux Falls network to gain some insights into the algorithm, the simulation model, and to the robust toll pricing problem. The first test empirically measures the efficiency of the simulation algorithm and approximate Pareto set by obtaining a standard error in the ε-indicator measure for a given number of scenarios and iterations. The second test compares the dominance of the proposed heuristic’s solutions with a conventional multiobjective genetic algorithm by comparing the average ε-indicator. The third test quantifies the gap due to falsely assuming that link failures are independent of each other when they are not. The last test quantifies the value of having the flexibility to adapt a Pareto set of toll pricing solutions to changing probability regimes such as peak and off-peak hurricane or snow seasons.     

Lattice expansion in seamless bilayer graphene constrictions at high bias

Our understanding of sp(2) carbon nanostructures is still emerging and is important for the development of high performance all carbon devices. For example, in terms of the structural behavior of graphene or bilayer graphene at high bias, little to nothing is known. To this end, we investigated bilayer graphene constrictions with closed edges (seamless) at high bias using in situ atomic resolution transmission electron microscopy. We directly observe a highly localized anomalously large lattice expansion inside the constriction. Both the current density and lattice expansion increase as the bilayer graphene constriction narrows. As the constriction width decreases below 10 nm, shortly before failure, the current density rises to 4 × 10(9) A cm(-2) and the constriction exhibits a lattice expansion with a uniaxial component showing an expansion approaching 5% and an isotropic component showing an expansion exceeding 1%. The origin of the lattice expansion is hard to fully ascribe to thermal expansion. Impact ionization is a process in which charge carriers transfer from bonding states to antibonding states, thus weakening bonds. The altered character of C-C bonds by impact ionization could explain the anomalously large lattice expansion we observe in seamless bilayer graphene constrictions. Moreover, impact ionization might also contribute to the observed anisotropy in the lattice expansion, although strain is probably the predominant factor.     

NaCl Nanoparticles as a Cancer Therapeutic

Many inorganic nanoparticles are prepared and their behaviors in living systems are investigated. Yet, common electrolytes such as NaCl are left out of this campaign. The underlying assumption is that electrolyte nanoparticles will quickly dissolve in water and behave similarly as their constituent salts. Herein, this preconception is challenged. The study shows that NaCl nanoparticles (SCNPs) but not salts are highly toxic to cancer cells. This is because SCNPs enter cells through endocytosis, bypassing cell regulations on ion transport. When dissolved inside cancer cells, SCNPs cause a surge of osmolarity and rapid cell lysis. Interestingly, normal cells are much more resistant to the treatment due to their relatively low sodium levels. Unlike conventional chemotherapeutics, SCNPs cause immunogenic cell death or ICD. In vivo studies show that SCNPs not only kill cancer cells, but also boost an anticancer immunity. The discovery opens up a new perspective on nanoparticle‐based therapeutics.