Soundness and Completeness Proofs by Coinductive Methods

We show how codatatypes can be employed to produce compact, high-level proofs of key results in logic: the soundness and completeness of proof systems for variations of first-order logic. For the classical completeness result, we first establish an abstract property of possibly infinite derivation trees. The abstract proof can be instantiated for a wide range of Gentzen and tableau systems for various flavors of first-order logic. Soundness becomes interesting as soon as one allows infinite proofs of first-order formulas. This forms the subject of several cyclic proof systems for first-order logic augmented with inductive predicate definitions studied in the literature. All the discussed results are formalized using Isabelle/HOL’s recently introduced support for codatatypes and corecursion. The development illustrates some unique features of Isabelle/HOL’s new coinductive specification language such as nesting through non-free types and mixed recursion–corecursion.     

Relational analysis of (co)inductive predicates, (co)algebraic datatypes, and (co)recursive functions

We present techniques for applying a finite relational model finder to logical specifications that involve high-level definitional principles such as (co)inductive predicates, (co)algebraic datatypes, and (co)recursive functions. In contrast to previous work, which focused on algebraic datatypes and restricted occurrences of unbounded quantifiers in formulas, we can handle arbitrary formulas by means of a three-valued Kleene logic. The techniques form the basis of the counterexample generator Nitpick for Isabelle/HOL. As case studies, we consider formulas about an inductively defined context-free grammar, a functional implementation of AA trees, and a coalgebraic list datatype.     

Microstructure and Composition of Primary and Recycled Single Grains of YBCO,GdBCO‐Ag,and SmBCO‐Ag Bulk Superconductors

The widespread use of single grain RE‐Ba‐Cu‐O [(RE)BCO] bulk superconductors, where RE is typically Sm, Gd, or Y, is, in part, limited by the relatively high costs of precursor powders and the low success rate of the manufacturing process. Both these problems can be addressed by recycling primary‐processed grains in which the initial growth process has failed in some way. Key to the use of recycled grains in practical applications is an assurance that their properties and performance are not inferior to those of primary grown grains. In this work, we describe the differences between the growth process, microstructure, and properties of primary and recycled (RE)BCO single grains. We observe that the mechanism of growth is the same for both primary and recycled single grain samples in all three RE‐based systems investigated. In the recycling process additional liquid‐rich phase powder is provided beneath a failed sample, whereby this liquid phase infiltrates upwards and contributes a sufficient concentration of additional RE species at the growth front to enable samples to grow relatively easily in the form of single grains by producing a more uniform composition at the growth front, which leads directly to an increased tolerance to the presence of Ag and Ce‐rich agglomerates. Importantly, we observe that the recycled samples have a much more uniform composition, and therefore exhibit more uniform superconducting properties, than single grain samples fabricated by a primary grown process.     

Deficits in complex motor functions, despite no evidence of procedural learning deficits, among HIV+ individuals with history of substance dependence.

Human immunodeficiency virus (HIV) and drugs of abuse affect common neural systems underlying procedural memory, including the striatum. The authors compared performance of 48 HIV seropositive (HIV+) and 48 HIV seronegative (HIV-) participants with history of cocaine and/or heroin dependence across multiple Trial Blocks of three procedural learning (PL) tasks: Rotary Pursuit (RP), Mirror Star Tracing (MST), and Weather Prediction (WP). Groups were well matched on demographic, psychiatric, and substance use parameters, and all participants were verified abstinent from drugs. Mixed model analyses of variance revealed that the individuals in the HIV+ group performed more poorly across all tasks, with a significant main effect of HIV serostatus observed on the Mirror Star Tracing and a trend toward significance obtained for the Rotary Pursuit task. No significant differences were observed on the Weather Prediction task. Both groups demonstrated significant improvements in performance across all three procedural learning tasks. It is important to note that no significant Serostatus × Trial Block interactions were observed on any task. Thus, the individuals in the HIV+ group tended to perform worse than those in the HIV- group across all trial blocks of procedural learning tasks with motor demands, but showed no differences in their rate of improvement across all tasks. These findings are consistent with HIV--associated deficits in complex motor skills, but not in procedural learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Thermodynamic Investigation of the Redox Properties of VPO Catalysts

Abstract  

The redox properties of a vanadium phosphorus oxide (VPO) catalyst with a V:P ratio of one were investigated using Coulometric Titration at 873 K. Equilibrium between (VO)₂P₂O₇ and VOPO₄ exists at a P(O₂) of 3 × 10⁻⁴ atm, corresponding to ΔG of −60 kJ/mol O₂. This value for VPO is significantly lower than that measured with other vanadium-containing catalysts that have been studied. Furthermore, compared to other vanadium catalysts, V⁺⁴ was stabilized against further reduction at lower P(O₂). These redox thermodynamics may help to explain the unique catalytic properties of VPO catalysts for partial oxidation of butane to maleic anhydride.     

Steam reforming of liquid hydrocarbons over a nickel-alumina spinel catalyst

Interest in steam reforming of liquid hydrocarbons is growing due to the necessity of developing reliable alternatives for their use in fuel cells. In particular, solid oxide fuel cells, which can operate with mixtures of H₂ and CO, are excellent candidates for being fed with liquid fuels coming from both fossil and renewable sources. Fossil-derived, synthetic diesel is an interesting option.In this work, an Al₂O₃-ZrO₂-supported nickel-alumina spinel was tested in a lab-scale isothermal packed-bed reactor as a catalyst of steam reforming of propane, hexadecane and tetralin as surrogates of constitutive families of all commercially available diesel fuels.The results show that the reaction reaches equilibrium at reaction severities lower than those reported in the literature. When operated at steam excess of 250%, carbon formation is not higher than expected by theoretical thermodynamic equilibrium calculations, and no significant catalyst deactivation is observed over the test durations. Scanning electron microscopy of the fresh and used catalyst surfaces shows no significant quantities of carbon.     

KnowVolution of a Fungal Laccase toward Alkaline pH

To date, commercial laccase preparations are used in the food, textile, and paper and pulp industries (mild pH). Laccases are attractive in the synthesis of dye molecules or oxidative lignin treatment, which take place at high pH (≥8.0). So far, one fungal laccase has been reported to be active at alkaline pH. Herein, engineering of the fungal laccase from Melanocarpus albomyces (MaL) for increased activity toward the substrate 2,6-dimethoxyphenol at pH (≥9.0) is reported. Through a knowledge-gaining directed evolution (KnowVolution) campaign, the key positions Leu365 and Leu513 were identified to increase alkaline tolerance. Both positions are located in close proximity of the T1Cu site. Molecular docking and simulations studies reveal that both substitutions act in a synergic way to stabilize and improve laccase activity at higher pH. Kinetic characterization of the final variant MaL-M1 (L365E/L513M) revealed at pH 9.8 a threefold improved k_cat (k_cat=(6.0±0.2) s⁻¹) compared with that of wild-type M. albomyces laccase (k_cat=(2.11±0.07) s⁻¹).     

45S5 Bioglass®-derived scaffolds coated with organic–inorganic hybrids containing graphene

Highly porous 45S5 Bioglass®-based scaffolds fabricated by a foam replication technique were coated with electrically conductive organic–inorganic hybrid layers containing graphene by a solution method. α,ω-Triethoxysilane terminated poly (ethylene glycol) and tetraethoxysilane were used as the precursors of the organic–inorganic hybrid coatings, that contained 1.5 wt.% of homogeneously dispersed graphene nanoplatelets. The resulting coated scaffolds retained their original high porosity and interconnected pore structure after coating. The presence of graphene did not impair the bioactivity of the scaffolds in simulated body fluid.Initial tests carried out using MG-63 cells demonstrated that both uncoated scaffolds and scaffolds coated with organic/inorganic hybrids containing graphene offered the cultured cells an adequate surface for cell attachment, spreading and expression of extracellular matrix. The results showed that scaffolds coated with graphene are biocompatible and they can support cellular activity. The electrical conductivity introduced by the coating might have the potential to increase tissue growth when cell culture is carried out under an applied electric field.     

Preparation and characterization of uniform molecularly imprinted polymer beads for separation of triazine herbicides

Uniform molecularly imprinted polymer beads were synthesized by precipitation polymerization for separation of triazine herbicides. A series of imprinted polymers were prepared using ametryn as template and divinylbenzene as crosslinking monomer, in combination with three different functional monomers under different solvent conditions. Under optimized reaction conditions, we obtained uniform molecularly imprinted polymer microspheres that display favorable molecular binding selectivity for triazine herbicides. The imprinted polymer beads synthesized using methacrylic acid as functional monomer in a mixture of methyl ethyl ketone and heptane showed the best results in terms of particle size distribution and molecular selectivity. Compared with nonimprinted polymer microspheres, the imprinted microspheres displayed significantly higher binding for a group of triazine herbicides including atrazine, simazine, propazine, ametryn, prometryn, and terbutryn. For the first time, precipitation polymerization has been used to produce highly uniform imprinted microspheres suitable for affinity separation of triazine herbicides. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012