Functionalization of two-component molecular networks: recognition of Fe³⁺

Two-component supramolecular networks have been constructed with a symmetric triphenylene derivative with three carboxyl groups (sym-TTT) and melamine. Two kinds of hydrogen bonds with different strength are involved in the multi-component self-assembly, one is H-bond between carboxyl group of sym-TTT and melamine, the other is intermolecular H-bond between melamine molecules. These interactions drive a structural transformation from close-packed network to hexagonal network with active amino groups inside of the cavity. Scanning tunneling microscopy (STM) measurements reveal that the functionalized network of sym-TTT/melamine could recognise Fe(3+). These results could be helpful for designing functionalized molecular networks by multi-component self-assembling strategy.     

Antioxidant Activity of γ-Oryzanol: A Complex Network of Interactions

γ-oryzanol (Orz), a steryl ferulate extracted from rice bran layer, exerts a wide spectrum of biological activities. In addition to its antioxidant activity, Orz is often associated with cholesterol-lowering, anti-inflammatory, anti-cancer and anti-diabetic effects. In recent years, the usefulness of Orz has been studied for the treatment of metabolic diseases, as it acts to ameliorate insulin activity, cholesterol metabolism, and associated chronic inflammation. Previous studies have shown the direct action of Orz when downregulating the expression of genes that encode proteins related to adiposity (CCAAT/enhancer binding proteins (C/EBPs)), inflammatory responses (nuclear factor kappa-B (NF-κB)), and metabolic syndrome (peroxisome proliferator-activated receptors (PPARs)). It is likely that this wide range of beneficial activities results from a complex network of interactions and signals triggered, and/or inhibited by its antioxidant properties. This review focuses on the significance of Orz in metabolic disorders, which feature remarkable oxidative imbalance, such as impaired glucose metabolism, obesity, and inflammation.     

Nanoindentation of Soda Lime–Silica Glass: Effect of Loading Rate

Structural and mechanical reliability of glass for both conventional and advanced applications is determined by the rate at which it can deform and sustain externally applied static or dynamic strain at the microstructural length scale. Hence, a large number of nanoindentation experiments were conducted on a thin (∼300 μm) commercial soda lime–silica glass with a 150 nm radius Berkovich tip at a constant load of 10,000 μN as a function of variations in the loading rates in the range of 10–20,000 μN/s. The results showed that the nanohardness of the soda lime–silica glass increased by as much as 74% as the loading rate was increased from 10 to 20,000 μN/s. Further, the presence of serrations in load–depth plots and deformation band formations inside the nanoindentaion cavities were more vividly observed in the nanoindentation experiments conducted at lower loading rates rather than those conducted at higher loading rates. These results are explained in terms of shear stress acting underneath the indenter as well as the time scale of interaction between the nanoindenter and the weak links at local microstructural length scale, which owe their origin to the subtle variations in the composition of the given glass.     

Hydrogenation of (–)-Carvone in Presence of Gold Catalysts: Role of the Support

The liquid phase hydrogenation of biomass derived (–)-carvone into industrially valuable dihydrocarvone was studied over monometallic Au catalysts supported on alumina, titania and zirconia, as well as on the mesoporous carbon support Sibunit in methanol as a solvent (100°C, hydrogen pressure 9 bar). It was shown that among the three types of functional groups present in carvone, which can be hydrogenated, namely C=O, conjugated and isolated C=C groups, hydrogenation of the latter was predominant. The catalytic activity was found to depend on the catalyst support type. Under comparative reaction conditions, the carvone conversion increased in the following sequence: Au/C ?Au/ZrO₂ < Au/Al₂O₃ ?Au/TiO₂. A higher activity of Au catalysts over metal oxides as compared to Au/C can be caused by the presence of acid sites as well as oxygen vacancies in their structure allowing strong adsorption of carvone through its carbonyl moiety. All catalysts supported on oxides showed similar selectivity towards trans- and cis-dihydrocarvone with the ratio between isomers (trans-/cis-isomer) being about 1.8, while this value for Au/C was close to 3.9, which can be related to a much lower carvone conversion in the latter case.     

Mechanisms of Solid–Gas Reactions: Reduction of Air Pollutants on Carbons

Topics in Catalysis - Ozone is a strong oxidizer and sulfur dioxide is a precursor to acid rain, both are air pollutants that can damage the respiratory tissues of animals and plants making them...     

CO Oxidation of Au–Pt Nanostructures: Enhancement of Catalytic Activity of Pt Nanoparticles by Au

The CO oxidation activity of Pt deposited on Ta₂O₅/Ta was studied with various amounts of Au post-deposited on Pt/Ta₂O₅/Ta. For Pt nanoparticles with a mean size of 2–4 nm, an enhancement in the CO oxidation activity with increasing amount of post-deposited Au was found. The mixed Au–Pt nanoparticles with sizes in the range of 2–4 nm exhibited higher stability than the bare Au nanoparticles with a similar size range. In contrast to the results obtained with the Pt nanoparticles, the catalytic activity of a thicker Pt film gradually decreased with increasing amount of Au deposited. Based on the CO desorption experiments, it is suggested that the surface of the catalytically active Au–Pt bimetallic structures consists of both Au and Pt sites.     

High shear granulation of dolomite – II: Effect of amount of binder liquid on process kinetics

This paper, the second of a series, analyzes the effect of binder amount on the kinetics of wet granulation process. Granulation experiments were conducted in batch, lab-scale high shear mixer with formulation system that was initially studied in first part of a series. First, we identify the effect of binder content on the net granulation behaviour during early stage of the process. Single entity property (its size) was accounted only within this research. The results indicate that binder content strongly promotes growth of dolomite entities. Secondly, 1-D discretized population balance equation (PBE) and Equi-Partition of Kinetic Energy (EKE) theory were used to simulate the net granulation process. Tested “coalescence-only” models provide good prediction of real dolomite granule size distributions (GSDs) during early stage of the process for each binder content value. By using modelling procedure granule growth rates were quantified. Ultimate goal of relating the coalescence rates of dolomite entities with binder amount variable is provided. This will result in a better perspective of the meso-scale of the dolomite granulation process.     

Characterization of DSA®-type oxygen evolving electrodes: Choice of a coating

In the search for a DSA^®-type electrode for oxygen evolution in acidic solutions, nine binary coatings with IrO₂, RuO₂, Pt as conducting component, and TiO₂, ZrO₂, Ta₂O₅ as inert oxides, have been deposited on titanium, examined for their microstructural properties and tested for their electrocatalytic activity and anodic stability. Electrochemical true surfaces of the coatings were found to be dependent on structure and morphology: the mixtures that form a solid solution (RuO₂–TiO₂), or allow limited miscibility (IrO₂–TiO₂), show the lowest dispersion of active material. Differences in service lives, were attributed to differences in wear mechanism of the electrodes. It was found that Ti/IrO₂ (70 mol%)-Ta₂O₅ (30 mol%) is by far the best electrode.     

Appendix:Abstracts of Journal of Chemical Industry and Engineering(China)

A new plate-to-plate method for performanceprediction of azeotropic distillation processes isdeveloped.Azeotropic distillation is character-ized by the strong interaction among componentsand by a samll number of components involved.By plate-to-plate method,the number of intera-rive variables depends only on the number ofcomponents,therefore a combination of theplate-to-plate approach and the Newton-     

Young’s Modulus of Dry-pressed Ceramics: The Effect of the Binder

Measurements of Young’s modulus of green compacts prepared from spray-dried alumina powders containing two binders: polyvinyl alcohol or polyethylene glycol are reported. The variations of Young’s modulus with forming pressure are compared to those of mechanical strength and discussed in terms of glass transition temperature (T_g). When the T_g of the polymer is lower than the pressing temperature (case of PEG and moisture-plasticized PVA), the variation of the Young’s modulus is related to the evolution of the binder film covering the surface of primary particles inside the granules. Microcracking of the brittle external polymer-rich layer of granules seems to be responsible for a different evolution of Young’s modulus of green compact in the case of a binder with a T_g higher than the forming temperature (dry PVA).     

Electrochemical properties of oligothienylene–oligosilanylene block copolymers: Influences of block sizes

The fundamental electrochemical properties of oligothienylene–oligosilanylene block copolymers, especially the influences of the block sizes, were studied in acetonitrile. In electrochemical oxidation, films of the polymers containing Si–Si bonds suffer more or less from decomposition and dissolution due to partial cleavage of the Si–Si bonds in the oligosilanylene units. Decomposition decreases as the oligosilanylene block size decreases, and is not observed with copolymers containing no Si–Si bond, that is, oligothienylene–monosilanylene copolymers. The copolymer films can also be electrochemically anion doped. Cyclic voltammograms obtained at high scan rates generally exhibit a two-step oxidative doping process, though the second-step oxidation is hardly seen for polymers with smaller oligothienylene blocks. The potentials of the oxidative doping peaks show a cathodic shift as the oligosilanylene block size increases because of the –-interaction in the polymer chains and the action of the oligosilanylene block as a spacer, both of which are favourable to the stabilization of the cations and dications generated in the polymer chain.     

Synthesis and characterization of an isocyanurate–oxazolidone polymer: Effect of stoichiometry

Isocyanurate–oxazolidone polymers were synthesized by using various reactant stoichiometry of a diglycidyl ether of bisphenol-A (DGEBA) and a polymeric diphenyl methane diisocyanate (pMDI). The reaction was catalyzed by tris-2,4,6-dimethylaminoethylphenol (Ancamine K54). The effects of stoichiometry that the reaction had on the molecular structure and mechanical and thermomechanical properties were evaluated. Two main structures obtained from the reaction of DGEBA with pMDI, namely isocyanurate and oxazolidone, were clearly shown by Fourier transformed infrared spectroscopy (FTIR) analyses. It was found that the amount of DGEBA present determines the amount of oxazolidone formed. Where excess DGEBA was used, structural transformation reaction from isocyanurate to oxazolidone was observed. The amount of pMDI, on the other hand, influenced the amount of isocyanurate structure formed. As the relative amounts of isocyanurate and oxazolidone contents changed with stoichiometry of the reactants, the effects on the crosslink density in the samples were clearly shown by both mechanical and thermomechanical measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 879–888, 2001     

Physicochemical properties of electrodepositedβ-lead dioxide: Effect of deposition current density

The influence of current density on the coulometric efficiency of -PbO₂ deposition in 0.5 M cM lead nitrate, the nonstoichiometry, impurity of -PbO₂ and voltammetric double layer capacitance have been studied. While the coulometric efficiency is about 95% at current densities less than 30 mA cm^–2, it decreases at higher current densities. The oxygen deficiency, , in -PbO_2- has been found to be invariant with the current density. X-ray diffraction studies provide a linear decrease in the weight percent of -PbO₂ as an impurity in the -PbO₂ with increase in current density, and the -PbO₂ is found to be absent at 100mA cm^–2 or higher. The estimated double layer capacitance from the cyclic voltammograms recorded in the potential range 0.70–1.10V, increases with deposition current density, indicating enhanced surface area.     

Coagulation behavior of polyaluminum chloride:Effects of pH and coagulant dosage☆

Coagulation mechanisms of polyaluminum chloride (PACl) at various dosages were studied using a conventional jar test at different final and initial pH values during treating kaolin suspension. The optimal final pH and dosages for PACl were obtained based on residual turbidity and zeta potential of flocs. The coagulation zones at various PACl dosages and solution pH values were developed and compared with those of alum. It is found that the optimal mechanism under acidic condition is charge neutralization, while alkaline condition wil facilitate the coagulation of PACl. Both charge neutralization coagulation and sweep coagulation can achieve high coagulation efficiency under the alkaline condition ranging from final pH 7.0 to 10.0. Stabilization, charge neutralization destabilization, restabilization and sweep zones occur successively with increasing PACl dosages with the final pH values fixed at 7.0 and 8.0, but restabilization zone disappears at final pH 10.0. When the final pH is not controlled and consequently decreases with increasing PACl dosage, no typical sweep zone can be observed and the coagulant efficiency decreases at high PACl dosage. It seems that the final pH is more meaningful than the initial pH for coagulation. Charge neutralization coagulation efficiency is dominated by zeta potential of flocs and PACl precipitates. The charge neutralization and sweep coagulation zones of PACl are broader in the ranges of coagulant dosage and pH than those of alum. The results are helpful for us to treat water and wastewa-ter using PACl and to understand the coagulation process of PACl.     

Anchored Wilkinson Catalyst: Hydrogenation of β Pinene

The hydrogenation of β pinene over homogeneous and anchored Wilkinson’s catalysts was studied. Phosphotungstic acid was used to anchor the Wilkinson catalyst to an alumina support by an interaction between the heteropoly acid and the rhodium atom of the complex. The hydrogenation of β pinene over the anchored catalyst was accompanied by some isomerization to α-pinene which was subsequently hydrogenated along with the β pinene to the pinanes with selectivities to the cis (endo) pinane in the 85–88 % range at near 100 % conversion. With the homogeneous Wilkinson catalyst an 88 % selectivity to cis pinane was also observed but only at 82 % conversion. The use of a 1 % Rh/Al₂O₃ catalyst for this hydrogenation gave some unexpected results. There was a facile isomerization to α pinene which was not hydrogenated further. The reaction stopped at about 30 % conversion at which time the cis and trans pinanes were present in near equal amounts in about 16–18 % yields.

     

Synthesis of β-SiAlON whiskers: dependence of uniform morphology upon preparation conditions

Abstract

Abstract

β-SiAlON whiskers with uniform morphology were prepared using reaction sintering method under different conditions. The effect of preparing conditions on the morphology of β-SiAlON whiskers was systematically studied by SEM, XRD, TEM and HRTEM. The results showed that single crystalline β-SiAlON whiskers with uniform morphology were successfully fabricated at 1773 K for 6 h under flowing nitrogen atmosphere. The well synthesised whiskers were of several hundreds of nanometres in diameter and a few hundreds of micrometres in length. Although the morphology and its size distribution are mainly determined by the reaction temperature and holding time, they can also be tailored by controlling the reaction atmosphere. The ratio of staring materials has no significant influence on the morphology of β-SiAlON whiskers. The growth of β-SiAlON whiskers follows a vapour–solid mechanism, and the formation of the belt-like whiskers is attributed to an anisotropic growth at the early nucleation/growth stage.     

Active centres from the point of view of kinetics: Analysis and revision of Constable’s interpretation

Constable used the first title for a review in 1957. But he did not regard the influence of kinetics. The ignorance of kinetics is still a problem of immediate interest. Constable introduced the concept of “active site distribution model” to explain the variation of the “experimental” activation energy caused by thermal deactivation. He used true kinetic terms for the interpretation although he observed apparent kinetic terms. This inconsistency can be resolved with an “apparent” particle size effect, due to the variation of the number of sites.     

CFD-PBM simulation of the column flotation unit of FCMC: Importance of gas–liquid interphase forces models

The cyclonic micro-bubble flotation column (FCMC) is an efficient flotation device for the separation of fine minerals, but its mechanisms are rarely studied using computational fluid dynamics (CFD). This paper reports the air–water two-phase computational fluid dynamics-population balance model (CFD-PBM) simulations for the column flotation unit of an FCMC. The shear stress transport (SST) k-ω model with curvature correction (CC) is used to simulate turbulence effects. Then, the interphase forces models considering bubble size distribution are selected according to the experimental data in a bubble column, which is in analogy to the column flotation unit of the FCMC. Finally, the optimal combination of interphase forces models (i.e., the Ishii–Zuber drag force model, the Hosokawa–Frank wall lubrication force model, and the Lopez de Bertodano turbulent dispersion force model) is applied to simulate an FCMC with a superficial gas velocity of 0.0144 m/s. The results show that the CFD-PBM simulation can achieve a relative error of 9.09% for gas volume fraction and −5.45% for bubble rising velocity, indicating the reliability of the selected combination of interphase forces models.