Experimental Simulation of the Reactor Section of Fluid Cokers: Comparison of FCC and Fluid Coke Particles

The hydrodynamics of fluid cokers were studied in a pressurized fully cylindrical cold model of diameter 483 mm, geometrically and dynamically scaled down by a factor of ～20 from commercial units. Differential pressure fluctuations, voidage distributions, solids momentum flux distributions and steady state gas mixing behaviour in the reactor section are compared for the same operating conditions with two kinds of particles, FCC and fluid coke. The voidage distributions and core‐annular flow structures in the reactor section were similar enough that either FCC or fluid coke particles can be used for cold modelling of fluid cokers.     

Rubber‐toughened polypropylene nanocomposite: Effect of polyethylene octene copolymer on mechanical properties and phase morphology

Rubber‐toughened polypropylene (PP)/org‐Montmorillonite (org‐MMT) nanocomposite with polyethylene octene (POE) copolymer were compounded in a twin‐screw extruder at 230°C and injection‐molded. The POE used had 25 wt % 1‐octene content and the weight fraction of POE in the blend was varied in the range of 0–20 wt %. X‐ray diffraction analysis (XRD) revealed that an intercalation org‐MMT silicate layer structure was formed in rubber‐toughened polypropylene nanocomposites (RTPPNC). Izod impact measurements indicated that the addition of POE led to a significant improvement in the impact strength of the RTPPNC, from 6.2 kJ/m² in untoughened PP nanocomposites to 17.8 kJ/m² in RTPPNC containing 20 wt % POE. This shows that the POE elastomer was very effective in converting brittle PP nanocomposites into tough nanocomposites. However, the Young's modulus, tensile strength, flexural modulus, and flexural strength of the blends decreased with respect to the PP nanocomposites, as the weight fraction of POE was increased to 20 wt %. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and rubber particles size. SEM study revealed a two‐phase morphology where POE, as droplets was dispersed finely and uniformly in the PP matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3441–3450, 2006     

Preparation of alginate/poly(N‐isopropylacrylamide) semi‐interpenetrating and fully interpenetrating polymer network hydrogels with γ‐ray irradiation and their swelling behaviors

Semi‐interpenetrating polymer network (semi‐IPN) and fully interpenetrating polymer network (full‐IPN) hydrogels composed of alginate and poly(N‐isopropylacrylamide) were prepared with γ‐ray irradiation. The semi‐IPN hydrogels were prepared through the irradiation of a mixed solution composed of alginate and N‐isopropylacrylamide (NIPAAm) monomer to simultaneously achieve the polymerization and self‐crosslinking of NIPAAm. The full‐IPN hydrogels were formed through the immersion of the semi‐IPN film in a calcium‐ion solution. The results for the swelling and deswelling behaviors showed that the swelling ratio of semi‐IPN hydrogels was higher than that of full‐IPN hydrogels. A semi‐IPN hydrogel containing more alginate exhibited relatively rapid swelling and deswelling rates, whereas a full‐IPN hydrogel showed an adverse tendency. All the hydrogels with NIPAAm exhibited a change in the swelling ratio around 30–40°C, and full‐IPN hydrogels showed more sensitive and reversible behavior than semi‐IPN hydrogels under a stepwise stimulus. In addition, the swelling ratio of the hydrogels continuously increased with the pH values, and the swelling processes were proven to be repeatable with pH changes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4439–4446, 2006     

PSA performances and viscoelastic properties of SIS‐based PSA blends with H‐DCPD tackifiers

Hotmelt pressure sensitive adhesives (PSAs) usually contain styrenic block copolymers like styrene–isoprene–styrene (SIS), SBS, SEBS, tackifier, oil, and additives. These block copolymers individually reveal no tack. Therefore, a tackifier is a low molecular weight material with high glass transition temperature (T_g), and imparts the tacky property to PSA. The SIS block copolymer with different diblocks was blended with hydrogenated dicyclopentadiene (H‐DCPD tackifier), which has three kinds of T_g. PSA performance was evaluated by probe tack, peel strength, and shear adhesion failure temperature. PSA is a viscoelastic material, so that its performance is significantly related to the viscoelastic properties of PSAs. We tested the viscoelastic properties by dynamic mechanical analysis and the thermal properties by differential scanning calorimeter to investigate the relation between viscoelastic properties and PSA performance. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2839–2846, 2006     

Isomerization and Decomposition of Chloromethylacetylene

The isomerization and thermal decomposition of chloromethylacetylene (CMA) has been studied with two shock tube techniques. The first experiment (Jerusalem) utilizes single-pulse shock tube methods to measure the isomerization rate of CMA to chloroallene. In addition, equilibrium constants can be estimated at ∼1200 K. The second experiment (Argonne) monitors Cl-atom formation at temperatures above ∼1150 K. Absolute yield measurements have been performed over the 1200–1700 K range and indicate that two decomposition channels contribute to CMA destruction, namely, Cl fission and HCl elimination. The results show that the branching fraction between processes is temperature dependent. Therefore, direct Cl-atom fission is accompanied by molecular elimination, undoubtedly giving HCl and one or more isomers of C₃H₂. MP2 6–31G(d,p) ab initio electronic structure calculations have been used to determine vibration frequencies and moments of inertia for three C₃H₃Cl isomers. Using these quantities, the experimental equilibrium constants required that ΔH⁰₀(CH₂Cl–C≡CH ⇌ CHCl=C=CH₂) = −;0.24 kcal mole⁻¹. A potential energy surface pertinent to the present system has been constructed, and RRKM calculations have been carried out in order to explain the isomerization rates. The isomerization data can be explained with E₀ = 52.3 kcal mole⁻¹ and 〈ΔE_down〉 = 225 cm⁻¹. Subsequent semi-empirical Troe and RRKM-Gorin modeling of the Cl atom rate data require E₀ = (67.5 ± 0.5) kcal mole⁻¹ with a 〈ΔE_down〉 = (365 ± 90) cm⁻¹. This suggests a heat of formation for propargyl radicals of (79.0 ± 2.5) kcal mole⁻¹.     

The binding mode of an E-64 analog to the active site of cathepsin B

Two binding modes of the isobutyl-NH-Eps-Leu-Pro inhibitor tocathepsin B have been proposed. Molecular docking using an empiricalforce field was carried out to distinguish between the two modes.The search began with manual docking, followed by random perturbationsof the docking conformation and cycles of Monte Carlo minimization.Finally, molecular dynamics was carried out for the most favorabledocking conformations. The present calculations predict thatthe isobutyl-NH-Eps-Leu-Pro inhibitor preferentially binds tothe S' rather than the S subsites of cathepsin B. The S' bindingmode prediction is supported by the X-ray crystal structureof cathepsin B bound to a closely related ethyl-O-Eps-Ile-Proinhibitor, which was found to bind in the S' subsite with theC-terminal epoxy ring carbon making a covalent bond to the sulfuratom of Cys29. This agreement, in turn, validates our dockingstrategy. Furthermore, the calculations provide evidence thatthe dominant contribution to the total stabilization energyof the enzyme–inhibitor complex stems from the strongelectrostatic interaction between the negatively charged C-terminalcarboxylate group of the ligand and the positively charged imidazoliumrings of His110 and His111. The latter are stabilized and heldin an optimal orientation for interactions with the C-terminalend of the ligand through a salt bridge between the side chainsof His110 and Asp22. By comparison with the crystal structure,some insight into the specificity of the epoxyldipeptide familytowards cathepsin B inhibition has been extracted. Both thecharacteristics of the enzyme (e.g. subsite size and hydrophobicity)as well as the nature of the inhibitor influence the selectivityof an inhibitor towards an enzyme.     

Erosion behavior of SiC–WC composites

Dense silicon carbide (SiC) ceramics were prepared with 0, 10, 30 or 50 wt% WC particles by hot pressing powder mixtures of SiC, WC and oxide additives at 1800 °C for 1 h under a pressure of 40 MPa in an Ar atmosphere. Effects of alumina or SiC erodent particles and the WC content on the erosion performance of sintered SiC–WC composites were assessed. Microstructures of the sintered composites consisted of WC particles distributed in the equi-axed grain structure of SiC. Fracture surfaces showed a mixed mode of fracture, with a large extent of transgranular fracture observed in SiC ceramics prepared with 30 wt% WC. Crack bridging by WC enhanced toughening of the SiC ceramics. A maximum fracture toughness of 6.7 MPa*m^1/2 was observed for the SiC ceramics with 50 wt% WC, whereas a high hardness of 26 GPa was obtained for the SiC ceramics with 30 wt% WC. When eroded at normal incidence, two orders of magnitude less erosion occurred when SiC–WC composites were eroded by alumina particles than that eroded by SiC particles. The erosion rate of the composites increased with increasing angle of SiC particle impingement from 30° to 90°, and decreased with WC reinforcement up to 30 wt%. A minimum erosion wear rate of 6.6 mm³/kg was obtained for SiC–30 wt% WC composites. Effects of mechanical properties and microstructure on erosion of the sintered SiC–WC composites are discussed, and the dominant wear mechanisms are also elucidated.     

Potentiostatically deposited polypyrrole/graphene decorated nano-manganese oxide ternary film for supercapacitors

A simple method based on potentiostatic polymerization was developed for the preparation of ternary manganese oxide-based nanocomposite films. The ternary nanocomposites, which were characterized using x-ray diffraction spectroscopy and x-ray photoelectron spectroscopy, showed that the manganese oxide within the film consisted of MnO₂ and Mn₂O₃. Electrochemical measurements showed that the ternary nanocomposite electrode exhibited high specific capacitance (up to 320.6 F/g), which was attributed to the morphology of a polypyrrole/graphene/manganese-oxide (PPy/GR/MnO_x) ternary nanocomposite. The experimental approach maximized the pseudocapacitive contribution from redox-active manganese oxide (MnO_x) and polypyrrole (PPy), as well as the electrochemical double layer capacitive (EDLC) characteristic from graphene (GR) sheets. Long cyclic measurements indicated that the specific capacitance of the ternary nanocomposite film could retain 93% of its initial value over 1000 charge/discharge cycles, in the potential range of −0.2 to 0.7 V versus silver/silver chloride electrode (Ag/AgCl).     

Predicted Ligands for the Human Urotensin‐II G Protein‐Coupled Receptor with Some Experimental Validation

Human Urotensin‐II (U‐II) is the most potent mammalian vasoconstrictor known. 1 Thus, a U‐II antagonist would be of therapeutic value in a number of cardiovascular disorders. 2 Here, we describe our work on the prediction of the structure of the human U‐II receptor (hUT₂R) using GEnSeMBLE (GPCR Ensemble of Structures in Membrane BiLayer Environment) complete sampling Monte Carlo method. With the validation of our predicted structures, we designed a series of new potential antagonists predicted to bind more strongly than known ligands. Next, we carried out R‐group screening to suggest a new ligand predicted to bind with 7 kcal mol^?1 better energy than 1‐{2‐[4‐(2‐bromobenzyl)‐4‐hydroxypiperidin‐1‐yl]ethyl}‐3‐(thieno[3,2‐b]pyridin‐7‐yl)urea, the designed antagonist predicted to have the highest affinity for the receptor. Some of these predictions were tested experimentally, validating the computational results. Using the pharmacophore generated from the predicted structure for hUT₂R bound to ACT‐058362, we carried out virtual screening based on this binding site. The most potent hit compounds identified contained 2‐(phenoxymethyl)‐1,3,4‐thiadiazole core, with the best derivative exhibiting an IC₅₀ value of 0.581 μM against hUT₂R when tested in vitro. Our efforts identified a new scaffold as a potential new lead structure for the development of novel hUT₂R antagonists, and the computational methods used could find more general applicability to other GPCRs.     

A study on performance optimization of a toilet by measuring accumulated flow rate of a trapway

When water shortages occur, toilet water-saving becomes an effective way to solve the problem. We developed a new method that utilizes the accumulated flow rate to predict the flushing performance and to obtain design data for the development of high-efficiency toilets. The results showed that the length and shape of the trapway are the most important factors for flushing performance, and additional water saving can be achieved by delaying the opening of the trapway outlet valve. In addition, the tank water level in the water tank needs to be optimized considering siphon intensity as well as siphon duration. In conclusion, the toilet was optimized up to 6.5 kg of water using 60 mm diameter flexible tube by the method of accumulated flow rate measurement. In the future, the development of an ultra high efficiency toilet below 4.5 kg will be tried utilizing the method.