Modeling of glycolysis of flexible polyurethane foam wastes by artificial neural network methodology

The glycolysis process as a useful approach to recycling flexible polyurethane foam wastes is modeled in this work. To obtain high quality recycled polyol, the effects of influential processing and material parameters, i.e. process time, process temperature, catalyst‐to‐solvent (Cat/Sol) and solvent‐to‐foam (Sol/Foam) ratios, on the efficiency of the glycolysis reaction were investigated individually and simultaneously. For the continuous prediction of process behavior and interactive effects of parameters, an artificial neural network (ANN) model as an efficient statistical‐mathematical method has been developed. The results of modeling for the criteria that determine the glycolysis process efficiency including the hydroxyl value of the recycled polyol and isocyanate functional group conversion prove that the adopted ANN model successfully anticipates the recycling process responses over the whole range of experimental conditions. The Cat/Sol ratio showed the strongest influence on the quality of the recycled polyol among the studied parameters, where the minimum hydroxyl value was obtained at a medium amount of the assigned ratio. For the consumed polyurethane foam, a higher value of this ratio led to an increase in the hydroxyl value and isocyanate conversion. © 2015 Society of Chemical Industry     

Photoelectrochemical properties of butane reduced flame-treated Zr-doped hematite thin films

In this research, Zr-doped hematite thin films were prepared by a simple and highly scalable liquid phase deposition method, and their photoelectrochemical (PEC) properties were investigated. The samples were post-heat treated using a butane reduced flame. PEC studies revealed that both Zr-doping and flame-treatment enhanced the performance of the hematite photoanodes. The photocurrent densities of the samples were considerably increased upon flame-treatment, that is, about 3.5 times for a 4% Zr-doped sample. The highest photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) was obtained, about 0.50 mA cm⁻² for the 4% Zr-doped sample, about five times higher than the undoped sample. The Mott–Schottky measurements revealed that the donor charge carrier density for the 4% Zr-doped sample was increased fivefold upon flame-treatment from 2.49 × 10¹⁹ to 1.38 × 10²⁰ cm⁻³. The optical investigations showed that the optical band gap energy values depend on the level of Zr-doping, and the sample with 4% Zr-doping showed the lowest band gap energy value, about 1.82 eV. The mechanism behind the effectiveness of the flame-treatment was investigated and attributed to the oxygen vacancy formation upon flame-treatment. The formation of oxygen vacancies activates the donor doping, and as a result, the charge carrier density increases. In general, butane reduced flame-treatment as a simple and effective strategy can be used as a post-heat treatment to boost the PEC properties of hematite thin films.     

Investigation on dynamic behaviour of a full-scale reinforced concrete bridge subjected to strong earthquakes using an automated analysis platform

In this paper, the condition of a full-scale concrete bridge subjected to strong earthquakes is evaluated using vibration-based analyses. A new computational toolkit is developed in MATLAB environment for damage identification and long-term monitoring. Two types of parametric and non-parametric analysis methods are carried out on monitoring data. Moreover, a dynamic performance index is proposed based on an AutoRegressive Moving Average with eXogenous excitation (ARMAX) model. This index utilises the response predicted from an ARMAX model to evaluate bridge behaviour during strong earthquakes. Based on the results, a minor but permanent drop of 0.05?Hz in natural frequency of the first transverse and vertical modes is observed after the first strong earthquake. Also, a significant drop in frequency of the first transverse mode is observed during the two strong earthquakes. The results of the index show that the bridge did not follow linear behaviour during the two strong earthquakes as expected from a linear system. A close to flag-shaped force-displacement relationship is also observed during the first strong earthquake that can be an indication of nonlinearity in bridge behaviour. The analysis results illustrate the efficiency of the new monitoring platform for long-term monitoring and management of large datasets.     

A model‐based development approach for the verification of real‐time Java code

Many real‐time systems are safety‐and security‐critical systems and, as a result, tools and techniques for verifying them are extremely important. Simulation and testing such systems can be exceedingly time‐consuming and these techniques provide only probabilistic measures of correctness. There are a number of model‐checking tools for real‐time systems. Although they provide formal verification for models, we still need to implement these models. To increase the confidence in real‐time programs written in real‐time Java, this paper proposes a model‐based approach to the development of such programs. First, models can be mechanically verified, to check whether they satisfy particular properties, by using current real‐time model‐checking tools. Then, programs can be derived from the model by following a systematic approach. We introduce a timed automata to RTSJ Tool (TART), a prototype tool to automatically generate real‐time Java code from the model. Finally, we show the applicability of our approach by means of four examples: a gear controller, an audio/video protocol, a producer/consumer and the Fischer protocol. Copyright © 2011 John Wiley & Sons, Ltd.     

Potential Rearrangements in the Reaction Catalyzed by the Indole Prenyltransferase FtmPT1

The indole prenyltransferase FtmPT1 catalyzes the C‐2 normal prenylation of brevianamide F (cyclo‐L ‐Trp‐L ‐Pro) to give tryprostatin B. A previous structural analysis and studies with alternate substrates suggest that the reaction might not proceed through a direct C‐2 attack, but could involve a C‐3 prenylation followed by a rearrangement. In this work we investigated the reactivity of FtmPT1 with tryptophan, 5‐hydroxybrevianamide, and 2‐methylbrevianamide, and isolated products that had been reverse prenylated at C‐3 and normal prenylated at N‐1, C‐3, or C‐4. The formation of these products can be rationalized through mechanisms involving either an initial C‐3 normal or C‐3 reverse prenylation. In addition, we demonstrate that a C‐3 reverse prenylated indole can undergo a nonenzymatic aza‐Cope rearrangement at 37 °C to give an N‐1 normal prenylated product. Together, these studies broaden the known product scope of this interesting catalyst and suggest that alternative mechanisms might be operating.     

Aldehyde-Based Inhibitors of the Peptidoglycan O-Acetylesterase Ape

The O-acetylation of the muramic acid residues in peptidoglycan (PG) is a modification that protects the bacteria from lysis due to the action of lysozyme. In Gram-negative bacteria, deacetylation is required to allow lytic transglycosylases to promote PG cleavage during cell growth and division. This deacetylation is catalyzed by O-acetylpeptidoglycan esterase (Ape) which is a serine esterase and employs covalent catalysis via a serine-linked acyl enzyme intermediate. Loss of Ape activity affects the size and shape of bacteria and dramatically reduces virulence. In this work, we report the first rationally designed aldehyde-based inhibitors of Ape from Campylobacter jejuni. The most potent of these acts as a competitive inhibitor with a K_i value of 13 μM. We suspect that the inhibitors are forming adducts with the active site serine that closely mimic the tetrahedral intermediate of the normal catalytic cycle. Support for this notion is found in the observation that reduction of the aldehyde to an alcohol effectively abolishes the inhibition.