Preferential CO oxidation over Pt/3A zeolite catalysts in H2-rich gas for fuel cell application

Even traces of CO in the hydrogen-rich gas fed to proton exchange membrane fuel cells (PEMFC) poison the platinum anode electrode and dramatically decrease the cell power output. In this work, several 1%Pt catalysts, all on 3A-type zeolite support, were prepared starting from different precursors and employing different methods: cation exchange (CE), wet impregnation (WI) and incipient wetness impregnation (IWI). The catalysts were characterised in terms of platinum dispersion and tested under realistic conditions in the quest of a catalyst for the removal of CO via the CO preferential oxidation (CO-PROX) reaction. The best catalytic performance was shown by the 1%Pt–3A catalyst prepared by IWI starting from Pt(NH₃)₄Cl₂ as a precursor, thanks to its highest platinum dispersion.     

Propagation of electroacoustic axial shear waves in a piezoelectric medium reinforced by continuous fibers

The propagation of electroacoustic axial shear waves in a fiber reinforced piezocomposites is studied in which matrix and fibers consist of piezoelectric transversely isotropic materials with symmetry axes parallel to the fiber axes. The effective medium method self-consistent variant as developed by Sabina and Willis is used to obtain explicit equations for the complex wave vector and it is solved numerically. Its real part determines the effective wave velocity and the imaginary part the attenuation factor. Integral equations expressed via dynamic Green’s function kernels are set up. The central problem of the method is the axial shear electroacoustic wave scattering on one isolated fiber in the medium having the effective piezoelectric properties. It is solved approximately by the Galerkin type method. The obtained expressions for the effective wave velocity and attenuation factor cover not only the long-wave region but the intermediate wave and it is valid for long wavelenghts up to the diameter of the inclusion. Wave velocity and attenuation coefficient coincide with ones obtained earlier in some other way. Some numerical examples are presented for real materials.     

Hybrid Solar Cells from a Blend of Poly(3‐hexylthiophene) and Ligand‐Capped TiO2 Nanorods

Hybrid bulk heterojunction solar cells based on nanocrystalline TiO₂ (nc‐TiO₂) nanorods capped with trioctylphosphine oxide (TOPO) and regioregular poly(3‐hexylthiophene) (P3HT) are processed from solution and characterized in order to relate the device function (optical absorption, charge separation, and transport and photovoltaic properties) to active‐layer properties and device parameters. Annealing the blend films is found to greatly improve the polymer–metal oxide interaction at the nc‐TiO₂/P3HT interface, resulting in a six‐fold increase of the charge separation yield and improved photovoltaic device performance under simulated solar illumination. In addition, the influence of the organic ligand at the nc‐TiO₂ particle surface is found to be crucial for charge separation. Ligand‐exchange procedures applied on the TOPO‐capped nc‐TiO₂ nanorods with an amphiphilic ruthenium‐based dye are found to further improve the charge‐separation yield at the polymer–nanocrystal interface. However, the poor photocurrents generated in the hybrid blend devices, before and after ligand exchange, suggest that transport within or between nanoparticles limits performance. By comparison with other donor–acceptor bulk heterojunction systems, we conclude that charge transport in the nc‐TiO₂:P3HT blend films is limited by the presence of an intrinsic trap distribution mainly associated with the nc‐TiO₂ particles.     

Fusion of mass spectrometry-based metabolomics data

A general method is presented for combining mass spectrometry-based metabolomics data. Such data are becoming more and more abundant, and proper tools for fusing these types of data sets are needed. Fusion of metabolomics data leads to a comprehensive view on the metabolome of an organism or biological system. The ideas presented draw upon established techniques in data analysis. Hence, they are also widely applicable to other types of X-omics data provided there is a proper pretreatment of the data. These issues are discussed using a real-life metabolomics data set from a microbial fermentation process.     

New Urbanism in the Inner City: A Case Study of Pittsburgh

This article argues that community development efforts can be significantly improved through careful attention to urban design. One potential design application is New Urbanism, which offers promising principles for integrating affordable housing into inner-city neighborhoods. These points are illustrated through a case study of four New Urbanist projects in Pittsburgh, Pennsylvania. Here, New Urbanists have been involved in community-based, inner-city revitalization efforts for more than two decades. This is often overlooked in a critical literature that focuses only on New Urbanist communities in the suburbs. While it is too early to pronounce final, comprehensive judgments on these Pittsburgh projects, they illustrate an important new direction that is worthy of close study by urban planners, community development officials, scholars of urban affairs, and urban designers.

Like the best-selling first edition, this report offers specific design guidance to planners, developers, and others involved in laying out, regulating, and reviewing proposals for “traditional neighborhoods.” For this edition, Arendt revised the model ordinance and subdivision regulations to make them easier to implement. Illustrations on the CD-ROM are directly tied to the provisions of the regulations. The CD-ROM also includes the author's running commentary on the regulations.     

Factors affecting the mechanical and viscoelastic properties of acrylic bone cement

The aim of this paper is to report a series of experiments investigating the factors that influence the viscoelastic properties of acrylic bone cement. The effects of the brand of cement, the length of time since mixing, temperature, the hydration of the cement, and the influence of fat and or blood in the environment on the creep and stress relaxation behavior of the cement have been studied in laboratory-prepared specimens in tension, compression and four point bending. Although there are significant differences in the viscoelastic behavior of some of the different brands of polymethylmethacrylate based cements, these differences are small by comparison with the major effects that can be exerted by the length of time since mixing and some environmental factors. These effects have important practical consequences, especially with regard to the ability of bench top and theoretical studies to predict reliably the mechanical and viscoelastic behavior of acrylic cement in vivo.     

Dietary intakes in infertile women a pilot study

Background  

The reproductive axis is closely linked to nutritional status. The purpose of this study was to compare the nutritional status in two groups of young infertile women, without clinically overt eating disorders: hypothalamic amenorrhea (HA) and polycystic ovary syndrome (PCOS).     

Osmium tetroxide, 2,2'-bipyridine: electroactive marker for probing accessibility of tryptophan residues in proteins

A complex of osmium tetroxide with 2,2'-bipyridine (Os,bipy) has been applied as a chemical probe of DNA structure as well as an electroactive DNA label. The Os,bipy has been known to form covalent adducts with pyrimidine DNA bases. Besides the pyrimidines, electrochemically active covalent adducts with Os,bipy are formed also by tryptophan (W) residues in peptides and proteins. In this paper we show that Os,bipy-treated proteins possessing W residues (such as avidin, streptavidin, or lysozyme) yield at the pyrolytic graphite electrode (PGE) a specific signal (peak alphaW) the potential of which differs from the potentials of signals produced by free Os,bipy or by Os,bipy-modified DNA. No such signal is observed with proteins lacking W (such as ribonuclease A or alpha-synuclein). Subpicomole amounts of W-containing proteins modified with Os,bipy can easily be detected using adsorptive transfer stripping voltammetry with the PGE. Binding of biotin to avidin interferes with Os,bipy modification of the protein, in agreement with the location of W residues within the biotin-binding site of avidin. These Ws are accessible for modification in the absence of biotin but hidden (protected from modification) in the avidin-biotin complex. The Os,bipy-modified avidin is unable to bind biotin, and its quarternary structure is disrupted. Analogous effects were observed with another biotin-binding protein, streptavidin. Our results demonstrate that modification of proteins with Os,bipy under conditions close to physiological, followed by a simple electrochemical analysis, can be applied in the microanalysis of protein structure and interactions.     

Taking Time Seriously? Theorizing and Researching Change in Communication and Media Studies

This article argues that in order to adequately comprehend and explain change, the field needs to engage more completely with the challenges of researching change over time, and ground the theorizing of change more firmly in empirical research. The goal of this article is to foster a more concerted discussion on these issues that will hopefully move research forward. The first part of the article reviews the breadth and diversity of existing empirical approaches to comprehending change over time across the field. The article then identifies some of the problems and oversights of current approaches and discusses possible solutions, drawing both on proposals developed by communication and media scholars and those developed in other disciplines.