Mechanistic differences in the selective reduction of NO by propene over cobalt- and silver-promoted alumina catalysts: kinetic and in situ DRIFTS study

The distribution of gaseous products and the nature of the surface species generated during the selective catalytic reduction of NO with C₃H₆ in the presence of excess O₂ (i.e. C₃H₆-SCR) were studied over both a 0.4% Co/γ-Al₂O₃ catalyst and a sulphated 1.2% Ag/γ-Al₂O₃ catalyst. The results were compared with those previously reported for the C₃H₆-SCR over 1.2% Ag/γ-Al₂O₃ and γ-Al₂O₃. High concentrations of NO₂ were observed in the product stream of the SCR reaction over the 0.4% Co/γ-Al₂O₃ and sulphated 1.2% Ag/γ-Al₂O₃ materials. The results show that (as in the case of the γ-Al₂O₃ and also probably that of the 1.2% Ag/γ-Al₂O₃) the NO₂ was formed via an alternative route to the direct oxidation of NO with O₂. The yields of NO₂ were higher over the Co/γ-Al₂O₃ than over the other materials and in contrast to the other materials, no NH₃ was produced over the Co/γ-Al₂O₃ catalyst. Based on these results and those of in situ DRIFTS experiments, a global reaction scheme incorporating organo-nitrogen species as key intermediates is proposed. In this scheme, NO, propene and oxygen react to form organo-nitro and/or organo-nitrito adsorbed species, the reaction products of which combine to yield N₂. The results reported here suggest that Co preferentially promotes the formation of nitrito-compounds which can readily decompose to NO₂, whereas Ag preferentially promotes the formation of nitro-compounds (from reaction of strongly bound ad-NO_x species) which can decompose to isocyanates and ammonia. The sulphation of the 1.2% Ag/γ-Al₂O₃ reduced the surface concentration of strongly bound ad-NO_x species which were thought to react with the reductant or derived species to yield the organo-nitrogen species.     

Synthetic Inhibitors of Extended Helix–Protein Interactions Based on a Biphenyl 4,4′‐Dicarboxamide Scaffold

Turn Bak : We present rationally designed scaffolds that mimic the spatial projection of the i, i+4, i+7, and i+11 residues of an α‐helix. A library of biphenyl derivatives was shown by competition fluorescence polarization and ITC to mimic Bak and disrupt the Bak/Bcl‐x_L protein–protein interaction. ¹⁵N HSQC experiments confirmed that the surface of Bcl‐x_L normally occupied by Bak was the target area of our new synthetic inhibitors.

     

Porous Nanocomposites 2: Pore-Structure Stability of Pure ZrO2, ZrO2(matrix)-Al2O3 and Al2O3(matrix)-ZrO2 Nanocomposites

Porous nanocomposites in the Al2O3-ZrO2 system were studied with a view to understand the selection rules for developing high temperature stable porous oxide systems. The results were also compared with TiO2-Al2O3 nanocomposite systems. The pore structure and phase evolution of these composites were studied using TG/DTA, XRD and nitrogen adsorption/desorption techniques. Al2O3 was found to be a good second phase stabiliser for stabilising ZrO2 and TiO2 matrix phases.     

Development of a hydrogen purifier with Pd-based composite membrane

A hydrogen purifier equipped with Pd-Cu-Ni/PNS membranes has been developed to purify low-grade hydrogen and supply it to processes requiring high-purity hydrogen. The purifier does not include any purge system to flush out hydrogen from the membrane module to prevent membrane embrittlement because there is no α-β phase transition below the critical point of the Pd-H system, making the purifier simple. The hydrogen purifier was tested with three different grades of hydrogen, 90, 99 and 99.9%, to determine the effects of the grade of feed hydrogen on the hydrogen permeation behavior. A lower grade required a lower recovery ratio of the purifier to obtain a given relative hydrogen permeation flux. It was confirmed that the purifier can provide high-purity hydrogen to a gas chromatograph (GC) for carrier and make-up gases. A 75-day durability test provided evidence that the hydrogen purifier could be useful for extended periods as needed for commercial processes.     

Impact of Administered <Emphasis Type="Italic">Bifidobacterium</Emphasis> on Murine Host Fatty Acid Composition

Recently, we reported that administration of Bifidobacteria resulted in increased concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in murine adipose tissue [1]. The objective of this study was to assess the impact of co-administration of Bifidobacterium breve NCIMB 702258 and the substrate for EPA, α-linolenic acid, on host fatty acid composition. α-Linolenic acid-supplemented diets (1%, wt/wt) were fed to mice (n = 8), with or without B. breve NCIMB 702258 (daily dose of 10⁹ microorganisms) for 8 weeks. Two further groups received either supplement of B. breve alone or unsupplemented diet. Tissue fatty acid composition was assessed by gas liquid chromatography. Dietary supplementation of α-linolenic acid resulted in higher (P < 0.05) α-linolenic acid and EPA concentrations in liver and adipose tissue and lower (P < 0.05) arachidonic acid in liver, adipose tissue and brain compared with mice that did not receive α-linolenic acid. Supplementation with B. breve NCIMB 702258 in combination with α-linolenic acid resulted in elevated (P < 0.05) liver EPA concentrations compared with α-linolenic acid supplementation alone. Furthermore, the former group had higher (P < 0.05) DHA in brain compared with the latter group. These results suggest a role for interactions between fatty acids and commensals in the gastrointestinal tract. This interaction between administered microbes and fatty acids could result in a highly effective nutritional approach to the therapy of a variety of inflammatory and neurodegenerative conditions.     

One‐dimensional model of vacuum filtration of compressible flocculated suspensions

This work details the one‐dimensional modeling of the different processes that may occur during the vacuum filtration of compressible flocculated suspensions. Depending on the operating conditions of the applied pressure and the initial solids concentration relative to the material properties of the compressive yield stress and the effective capillary pressure at the air–liquid interface, the dewatering process undergoes a combination of cake formation, consolidation, and/or desaturation. Mathematical models for these processes based on the compressional rheology approach are presented and appropriate solution methods outlined. Results using customary material properties are given for different operating conditions to illustrate the three dewatering processes. This approach lays the theoretical basis for further work understanding two‐ and three‐dimensional effects during desaturation, such as cracking and wall detachment. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Studies on the Electrodeposition of Ternary Copper-Zinc-Tin Alloys

The colour of Cu-Zn-Sn alloy coatings obtained by electrodeposition may differ-white, gold, dark gold, pink, and so on—depending on the specific combination of deposition conditions such as electrolyte composition, temperature, pH value and current density. Effects of pH and current density on the colour of the deposits and the associated electrode processes at the cathode and anode during deposition have been investigated. It was found that increasing either pH or current density causes an increase in the Zn content of the deposit and results in a colour trend away from pink and towards yellow. It was also found that cathodic deposition takes place in the sequence Sn, Cu, Zn, followed by Cu-Zn-Sn alloy. Anodic dissolution occurs at—1.0 V. From this study a reproducible gold-coloured coating was achieved, which could be of considerable practical importance.     

Evaluation of strain gage lengths for testing limestone and granite aggregate concretes

An experimental program was conducted to determine an appropriate length of strain gage for use in testing limestone and granite aggregate concretes. Variables in the test program included type and size of aggregate, and length of strain gage. Test specimens consisted of concrete cylinders fitted with a mechanical dial gage, and with multiple electrical resistance strain gages ranging from 120 mm (4.7 in.) to 5 mm (0.2 in.) in length. Cylinders were subjected to compression loading. Strains reported by the strain gages were compared to the strains calculated using dial gage readings. Recommendations are given for appropriate length of strain gages to be used with limestone aggregate and granite aggregate concretes.     

A model framework to assess the effect of dairy farms and wild fowl on microbial water quality during base-flow conditions

There is concern regarding microbial water quality in many pastoral catchments in New Zealand which are home to numerous livestock and wild animals. Information on microbial impacts on water quality from these animals is scarce. A framework is needed to summarise our current knowledge and identify gaps at the scale of an individual farm. We applied a Monte Carlo modelling approach to a hypothetical dairy farm based on the extensive data sets available for the Toenepi Catchment, Waikato, New Zealand. The model focused on quantifiable direct inputs to the stream from ducks, cows and farm dairy effluent (FDE) during base-flow conditions. Most of the inputs of Escherichia coli from dairy farms occur sporadically and, therefore, have little effect on the expected median stream concentrations. These sporadic inputs do however, have a strong influence on extrema such as 95th percentile values. Current farm mitigations of fencing streams and using improved management practices for applying FDE to land, such as low application rate deferred FDE irrigation systems, would appreciably reduce faecal microbial inputs to the stream. However, the concentrations of E. coli in rural streams may not reduce as much as expected as wild fowl living in streams would have a larger effect on water quality than a farm in which environmental mitigations are widely implemented.