Dynamics of the wet-end section in paper mills

A model representing the wet-end section of a paper mill has been developed to characterize its dynamic behavior during the grade change. The model is based on the mass balance relationships written for the simplified wetend white water network. From the linearization of the dynamic model, higher-order Laplace transfer functions were obtained followed by the reduction procedure to give simple lower-order models in the form of 1^st-order or 2^nd-order plus dead times. The dynamic response of the wet-end is influenced both by the white water volume and by the level of wire retention. Effects of key manipulated variables such as the thick stock flow rate, the ash flow rate and the retention aid flow rate on the major controlled variables were analyzed by numerical simulations. The simple dynamic model developed in the present study can be effectively used in the operation and control. This paper is dedicated to Professor Se Ki Moon on the occasion of his retirement from Hanyang University.     

Laccase‐catalyzed synthesis of polypyrrole‐multiwalled carbon nanotube composites as energy storage materials for capacitors

Multiwalled carbon nanotubes (MWNTs) were coated with polypyrrole (PPy) using in situ enzymatic polymerization of pyrrole catalyzed by a laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) from Trametes versicolor. Transmission electron microscopy revealed that the MWNTs were uniformly coated with very thin layers of PPy without any indication of globular polymer aggregate formations. The enzymatic synthesis of the MWNTs/PPy composites was quite simple being performed in a one‐pot aqueous solution (pH 4.0) under mild reaction conditions. The potential of the composites with respect to the development of energy storage devices was demonstrated by fabricating a two‐electrode coin cell capacitor (diameter 20 mm, thickness 1.6 mm) utilizing the composites as electrode materials. The capacitance of the cell was 28.0 F g^?1 for the electrode material as measured by a galvanostatic charge–discharge method. The energy density and power density were 2.55 and 805 W kg^?1, respectively, which were close to those of the capacitors classified as ultracapacitors. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43307.     

Novel CFTR Activator Cact-3 Ameliorates Ocular Surface Dysfunctions in Scopolamine-Induced Dry Eye Mice

Cystic fibrosis transmembrane conductance regulator (CFTR) is highly expressed on the ocular epithelium and plays a pivotal role in the fluid secretion driven by chloride transport. Dry eye disease is one of the most common diseases with limited therapeutic options. In this study, a high-throughput screening was performed to identify novel CFTR activators capable of inducing chloride secretion on the ocular surface. The screening of 50,000 small molecules revealed three novel CFTR activators. Among them, the most potent CFTR activator, Cact-3 (7-(3,4-dimethoxyphenyl)-N-(4-ethoxyphenyl)pyrazolo [1,5-α]pyrimidine-2-carboxamide), produced large and sustained Cl⁻ currents in WT-CFTR-expressing FRT cells with no alterations of ANO1 and hERG channel activity. The application of Cact-3 strongly activated CFTR in the ocular epithelia of mice and it also significantly increased CFTR-mediated Cl⁻ transport in a primary cultured human conjunctival epithelium. Cact-3 strongly stimulated tear secretion in normal mice. In addition, Cact-3 significantly reduced ocular surface damage and the expression of proinflammatory factors, including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ in an experimental mouse model of dry eye disease. These results suggest that Cact-3, a novel CFTR activator, may be a potential development candidate for the treatment of dry eye disease.     

Saccharification of alginate by using exolytic oligoalginate lyase from marine bacterium Sphingomonas sp. MJ-3

Alginate is a linear polysaccharide that is abundant in algal biomass. A novel recombinant exolytic oligoalginate lyase from a marine bacterium, Sphingomonas sp. MJ-3, was used for the saccharification of alginate into alginate monosaccharides in order to use alginate monosaccharides as renewable carbon source. The optimal heterologous expression condition for the MJ-3 oligoalginate lyase was determined, and the effects of saccharification reaction conditions were evaluated. Unsaturated monosaccharides up to 3.3 mg/ml were successfully prepared from 1% (w/v) alginate by using the recombinant oligoalginate lyase of Sphingomonas sp. MJ-3.     

Chemical-looping combustion of syngas by means of spray-dried NiO oxygen carrier

Chemical-looping combustion (CLC) of syngas has a potential to generate power economically with achieving the inherent carbon dioxide capture. An oxygen carrier with high reactivity and excellent physical properties would make CLC technology more competitive. In this work, oxygen carrier with 70 wt% NiO was prepared by spray drying technique. The prepared oxygen carrier had excellent physical properties for fluidized-bed application of CLC process. The reactivity of the oxygen carrier in repeated reduction-oxidation was measured by thermogravimetric analyzer with simulated syngas. Oxygen carrier calcined at 1,100 °C showed high oxygen transfer capacity of 14.7 wt%, utilizing 98% of the transferable oxygen. Oxygen transfer capacity and oxygen transfer rate was increased with the increase of reaction temperature, and the highest oxygen transfer rate was observed when about half of the transferable oxygen reacted with syngas. The reduction rate of the syngas (mixture of H₂ and CO) appeared to be approximately the sum of the reaction rate of each fuel gas. The experimental results indicated that the spray-dried NiO oxygen carrier prepared in this work could be a good quality oxygen carrier for the CLC of syngas.     

ZSM-5 Supported Cobalt Catalyst for the Direct Production of Gasoline Range Hydrocarbons by Fischer–Tropsch Synthesis

Abstract  

Fischer–Tropsch synthesis (FTS) reaction for the direct production of gasoline range hydrocarbons (C₅–C₉) from syngas was investigated on cobalt-based FTS catalyst supported on the ZSM-5 possessing a four different Si/Al ratio. The FTS catalysts were prepared by impregnation method using cobalt nitrate precursor in a slurry of ZSM-5, and they were characterized by surface area, XRD, H₂-TPR and NH₃-TPD. Cobalt supported catalyst on ZSM-5 having a low Si/Al ratio of 15 was found to be superior to the other catalysts in terms of better C₅–C₉ selectivity due to the formation of small cobalt particle and the presence of larger number of weak acidic sites. It also exhibited the highest catalytic activity because of the higher reducibility and the small cobalt particle size.     

Physical properties of phenol-anchored multiwall carbon nanotube/epoxy nanocomposite

Surface functionalization of multiwall carbon nanotubes (MWCNTs) was carried out by introducing a ylide group containing anchored phenol structures. Epoxy nanocomposites filled with modified and pristine carbon nanotubes were prepared, and their mechanical, electrical, and thermal properties were evaluated. Mechanical properties such as tensile strengths and Young’s moduli of the epoxy nanocomposites increased significantly with the addition of the modified MWCNTs compared to the pristine MWCNTs, due to the strong interaction between the modified MWCNTs and the epoxy matrix. Scanning electron microscopy of the fractured epoxy systems revealed that the functionalized MWCNTs were finely dispersed in the matrix, as opposed to the pristine carbon nanotubes. The epoxy/functionalized MWCNT nanocomposite had a lower surface electrical resistance than the epoxy/pristine MWCNT nanocomposite, confirming the effect of functionalization.     

Purification and enzymatic properties of the extracellular and constitutive chitosanase produced by Bacillus subtilis RKY3

BACKGROUND: Purification and enzymatic properties of a chitosanase from Bacillus subtilis RKY3 have been investigated to produce a chitooligosaccharide. The enzyme reported was extracellular and constitutive, which was purified by two sequential steps including ammonium sulfate precipitation and ion exchange chromatography. RESULTS: Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of the purified chitosanase revealed one single band corresponding to a molecular weight of around 24 kDa. The highest chitosanase activity was found to be at pH 6.0 and at 60 °C. Although the mercaptide forming agents such as Hg²⁺ (10 mmol L^?1) and p‐hydroxymercuribenzoic acid (1 mmol L^?1, 10 mmol L^?1) significantly or totally inhibited the enzyme activity, its activity was enhanced by the presence of 10 mmol L^?1 Mn²⁺. The enzyme showed activity for hydrolysis of soluble chitosan and glycol chitosan, but colloidal chitin, carboxymethyl cellulose, crystalline cellulose, and soluble starch were not hydrolyzed. The analysis of chitosan hydrolysis by thin‐layer chromatography and viscosity variation revealed that the purified enzyme should be endosplitting‐type chitosanase. CONCLUSION: The chitosanase produced by Bacillus subtilis RKY3 was a novel chitosanlytic enzyme with relatively low molecular weight, which is a versatile enzyme for chitosan hydrolysis because it could hydrolyze soluble chitosan into a biofunctional oligosaccharide at a high level. Copyright © 2011 Society of Chemical Industry     

Characterization of poly(vinylidenefluoride-co-hexafluoropropylene)-based polymer electrolyte filled with TiO2 nanoparticles

Nanoscale TiO₂ particle filled poly(vinylidenefluoride-co-hexafluoropropylene) film is characterized by investigating some properties such as surface morphology, thermal and crystalline properties, swelling behavior after absorbing electrolyte solution, chemical and electrochemical stabilities, ionic conductivity, and compatibility with lithium electrode. Decent self-supporting polymer electrolyte film can be obtained at the range of <50 wt% TiO₂. Different optimal TiO₂ contents showing maximum liquid uptake may exist by adopting other electrolyte solution. Room temperature ionic conductivity of the polymer electrolyte placed surely on the region of >10⁻³ S/cm, and thus the film is very applicable to rechargeable lithium batteries. An emphasis is also be paid on that much lower interfacial resistance between the polymer electrolyte and lithium metal electrode can be obtained by the solid-solvent role of nanoscale TiO₂ filler.     

Preparation and properties of EPDM/organomontmorillonite hybrid nanocomposites

Hybrid nanocomposites based on organophillic montmorillonite (MMT) and ethylene–propylene–diene rubber (EPDM) have been prepared by a melt compounding process. From analysis by X‐ray diffraction and transmission electron microscopy, the rubber molecules were found to be intercalated into the galleries of organoMMT and the silicate layers of organoMMT are uniformly dispersed as platelets of 50–80 nm thickness in the EPDM matrix. Dynamic mechanical studies reveal a strong rubber–filler interaction in the hybrid nanocomposite which is manifested in the lowering of tan δ at the glass transition temperature. The hybrid nanocomposites exhibit great improvement in tensile and tear strength, and modulus, as well as elongation‐at‐break. Moreover, the permeability of oxygen for the hybrid nanocomposite was reduced remarkably. © 2002 Society of Chemical Industry