Dynamic modeling of gas phase propylene homopolymerization in fluidized bed reactors

A new model with comprehensive kinetics for propylene homopolymerization in fluidized bed reactors was developed to investigate the effect of mixing, operating conditions, kinetic and hydrodynamic parameters on the reactor performance as well as polymer properties. Presence of the particles in the bubbles and the excess gas in the emulsion phase was considered to improve the two-phase model, thus, considering the polymerization reaction to take place in both the bubble and emulsion phases. It was shown that in the practical range of superficial gas velocity and catalyst feed rate, the ratio of produced polymer in the bubble phase to the total production rate is roughly between 10% and 13%, which is a substantial amount and cannot be ignored. Simulation studies were carried out to compare the results of the improved two-phase, conventional well-mixed and constant bubble size models. The improved two-phase and well mixed models predicted a narrower and safer window at the same running conditions compared with the constant bubble size model. The improved two-phase model showed close dynamic behavior to the conventional models at the beginning of polymerization, but starts to diverge with the evolution of time.     

Computational Fluid Dynamics Modeling for Urea Hydrolysis in a Batch Reactor for Flue Gas Conditioning

A computational fluid dynamics (CFD) model is proposed to simulate urea hydrolysis for ammonia synthesis as a safe feed stock to flue gas conditioning in thermal power plants. A series of parametric studies to investigate flow rates, thermal boundary conditions, and reactor geometry was performed and operating conditions and reactor geometry were optimized. Detailed 3D flow, heat, and chemistry simulations of ammonia were carried out with predicted conversions comparable to measurements and the dependence of the experiments on the reaction parameters was evaluated. Through simulation under the same conditions the output was generated and compared to the experimental plot. Profiles of temperature and flow patterns were successfully achieved through simulation.     

Effect of chemical modification of oil fly ash and compatibilization on the rheological and morphological properties of low‐density polyethylene composites

In this study, the effect of oil fly ash (OFA), a by‐product of oil fuel power plants, on the rheological and morphological behavior of low‐density polyethylene (LDPE) is investigated. As received and acid‐functionalized OFA (COOH‐OFA) are used to examine the effect of surface modification of OFA on polymer–filler composites. LDPE/OFA composites were prepared by melt mixing with filler loading in the range 1–10 wt %. The results are compared with pure LDPE. The effect of polyethylene‐grafted‐maleic anhydride (PE‐g‐MA) as a compatibilizer was also studied. Both viscous and elastic properties of composites increased with OFA loading especially at low frequency. The surface modification of OFA has influenced the properties of OFA. As‐received OFA showed some agglomeration at high loading that resulted in two‐phase system as described by scanning electron microscopy (SEM) and Cole–Cole plot. Field emission‐SEM (FE‐SEM) images showed improvement in the dispersion of COOH‐LDPE/OFA composites. In addition, the surface modification reduced the size of agglomeration. In general, the COOH modification of OFA improved both the dispersion and rheological properties of OFA. With chemical modification, the concentration of the filler can be increased to 10% without compromising the properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Composite polymeric microsponge-based long-acting gel formulation for topical delivery of mupirocin

Topical delivery of medicaments in a controlled manner is still a promising area of research. Drug-containing dammar gum-ethyl cellulose composite microsponge loaded gel formulation (D-MSPG) was developed for controlled topical delivery of mupirocin. The drug-loaded microsponges (D-MSPs) were formulated by the quasi-emulsion solvent diffusion method and were evaluated for morphology, particle size distribution, entrapment efficiency, thermal properties, and crystallinity. The optimized D-MSPs (entrapment efficiency 91.5 ± 4.0% and particle size of 55.15 ± 2.9 μm) were dispersed in carbopol 934 gel (D-MSPG). The final product was characterized for pH, viscosity, texture, spreadability, consistency, syneresis, in vitro drug release, and ex vivo skin penetration study. A comparative study with marketed formulation was performed. For optimized gel formulation (G4), drug content was 104.19 ± 1.68%, and drug release was 84.19% after 24 h. The pH of the optimized gel was observed to be 6.05 ± 0.04. Viscosity of the optimized gel formulation was found to be 1212.15 ± 434.85 mPa-s at 50 s⁻¹. The steady-state flux (J) in ex vivo skin permeation was observed to be 53.96 μg cm⁻² h⁻¹ and the permeability coefficient was 2.69 cm/h for the optimized gel formulation. According to the findings, the D-MSPG-based formulation strategy can act well to prolong the topical delivery of mupirocin or similar drug molecules.     

Hydrolysis of SnCl2 on polyaniline: Formation of conducting PAni‐SnO2 composite with enhanced electrochemical properties

First time in the literature, we report that polyaniline‐EB can be doped by SnCl₂ to give conducting SnO₂ doped polyaniline novel material. The composite is characterized by Fourier transform infrared, ultraviolet‐visible, X‐ray diffraction, scanning electron micrograph, transmission electron microscopy, and electrochemical methods. The new composite exhibited improved electrochemical properties compared with the virgin polymer. The composite is also expected for its high sensitivity for recognizing volatile organic compounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Impact of frying on key fatty acid ratios of canola oil

The study was carried out to investigate the changes in saturated (SFA), monoene (MUFA), trans (TFA), and polyunsaturated (PUFA) fatty acids and the key fatty acid ratios (SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0) during potato chips frying in canola oil using single bounce attenuated total reflectance FTIR (SB‐ATR‐FTIR) spectroscopy. The data obtained from GC‐FID were used as reference. The calibration of main fat groups and their key fatty acid ratios were developed by partial least square (PLS) regression coefficients using 4000 to 650 cm^?1 spectral range. FTIR PLS regression for the predicted SFA, MUFA, TFA, and PUFA were found 0.999, 0.998, 0.998, and 0.999, respectively, whereas for SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0 the regression coefficients were 0.991, 0.997, 0.996, and 0.994, respectively. We conclude that FTIR‐PLS could be used for rapid and accurate assessment of changes in the main fat groups and their key fatty acid ratios ratio during the frying process. Practical applications: FTIR‐ATR method is very simple, rapid, and environmentally friendly. No sample preparation is required and one drop of oil is enough for FTIR analysis. The proposed method could be applied for quick determination of key fatty acid ratios in the food processing industry.     

添加异辛醇对水与金属表面接触角的影响

向溴化锂水溶液中添加微量异辛醇表面活性剂,能显著增强溴化锂吸收式制冷机的吸收作用,提高制冷能力。但添加了异辛醇后,吸收式制冷机中的降膜蒸发器的换热效果却不能保证得到强化,有时出现降膜蒸发器的换热效果变差的现象。为探究导致换热变差的原因,本研究通过测量异辛醇水溶液和金属板表面的接触角,发现水中加入微量异辛醇后接触角普遍增大,湿润性变差,使降膜蒸发器的传热变差。通过测量并比较同浓度异辛醇水溶液在不同金属表面的接触角,得出40 mg·L^-1时异辛醇水溶液在镀锌钢板表面的湿润性最好,其次是不锈钢板,在紫铜表面的湿润性最差。异辛醇水溶液的浓度变化对每种金属板接触角没有明显影响。     

Ubiquitin C-Terminal Hydrolase L1: Biochemical and Cellular Characterization of a Covalent Cyanopyrrolidine-Based Inhibitor

The deubiquitinase (DUB) ubiquitin C-terminal hydrolase L1 (UCHL1) is expressed primarily in the central nervous system under normal physiological conditions. However, UCHL1 is overexpressed in various aggressive forms of cancer with strong evidence supporting UCHL1 as an oncogene in lung, glioma, and blood cancers. In particular, the level of UCHL1 expression in these cancers correlates with increased invasiveness and metastatic behavior, as well as poor patient prognosis. Although UCHL1 is considered an oncogene with potential as a therapeutic target, there remains a significant lack of useful small-molecule probes to pharmacologically validate in vivo targeting of the enzyme. Herein, we describe the characterization of a new covalent cyanopyrrolidine-based UCHL1 inhibitory scaffold in biochemical and cellular studies to better understand the utility of this inhibitor in elucidating the role of UCHL1 in cancer biology.     

Influence of Chemical Reaction on Mass Transport in Yield Stress Exhibiting Flow Regime

Theoretical Foundations of Chemical Engineering - In this study, the simulations for first-order chemical reactions (constructive and destructive) in the flow of the Casson fluid with...     

Thermal conductivity prediction of foods by Neural Network and Fuzzy (ANFIS) modeling techniques

A neuro-fuzzy modeling technique was used to predict the effective of thermal conductivity of various fruits and vegetables. A total of 676 data point was used to develop the neuro-fuzzy model considering the inputs as the fraction of water content, temperature and apparent porosity of food materials. The complexity of the data set which incorporates wide ranges of temperature (including those below freezing points) made it difficult for the data to be predicted by normal analytical and conventional models. However the adaptive neuro-fuzzy model (ANFIS) was able to predict conductivity values which closely matched the experimental values by providing lowest mean square error compared to multivariable regression and conventional artificial neural network (ANN) models. This method also alleviates the problem of determining the hidden structure of the neural network layer by trial and error.