bluuebunny/crossref_metadata_2025 huggingface dataset:
Jan Patočka: fenomenología asubjetiva y filosofía herética de la Historia
Authors: Ortega Rodríguez Iván
Published: March 2009

Nuestro objetivo es presentar el pensamiento de Jan Patočka y los debates filosóficos que suscitan sus posiciones. El núcleo de su pensamiento, a nuestro juicio, es la existencia humana como esencialmente trascendiendo lo dado y descubriendo en ello su esencial libertad. La investigación fenomenológica de Patočka busca una fenomenología “asubjetiva” y conceptuar la existencia como movimiento (diversificado en los tres movimientos de la existencia humana). La filosofía de la historia apunta a los orígenes de Europa, así como a las transformaciones esenciales que han llevado a un dominio absoluto de la razón técnica. En esta situación, sólo el sacrificio parece poder contrarrestar la civilización técnica. Finalmente, confrontamos a Patočka con Levinas, mostrando cómo se suscita un debate fundamental entre el monismo y el pluralismo ontológico. Este debate tiene una importancia crucial la Ética y la Política El pensamiento de Patočka es, así, una muestra de cómo la fenomenología sigue vigente.
El cerebro como máquina para aprender, recordar y olvidar
Authors: Gruart i Massó Agnès
Published: March 2009

El cerebro es el órgano responsable de dos grandes habilidades, pensar y actuar, las cuales requieren de la capacidad de aprender y de recordar la información adquirida. El gran avance de las Neurociencias en los últimos años ha permitido conocer algunos de los mecanismos que subyacen a estos procesos, pero quedan aún muchos aspectos por descubrir. Se conoce la estructura neuronal y muchos de los mecanismos de comunicación entre neuronas y se han identificado algunas estructuras relacionadas con la elaboración y almacenamiento de los diferentes tipos de memoria. Esto ha animado al desarrollo de fármacos que puedan incidir positivamente sobre estos procesos. La ciencia ficción por un lado, y la presión mediática por el otro, han hecho que perduren algunas leyendas acerca de las extraordinarias capacidades del sistema nervioso: desde aceptar que el cerebro es como un ordenador a pensar que es de una estructura plástica con capacidades prácticamente ilimitadas.
Thermal, optical, and water sorption properties in composite films of poly(ether imide) and bismaleimides: Effect of chemical structure
Authors: Seo Jongchul , Jang Wonbong , Han Haksoo
Published: March 2009

Two series of semi‐interpenetrating polymer network (semi‐IPN) composite films, PEI/bismaleimide (UTBM) and PEI/fluorinated BMI (UTFBM) were prepared using a thermoplastic PEI and two different crosslinkable imide moieties. The effects of chemical structure and content of crosslinkable imide moieties on thermal stability, dielectric properties, and water sorption have been investigated. Glass transition temperature and weight loss temperatures increased with increase in the content of crosslinkable imide moieties, indicating the enhanced thermal stability of the semi‐IPN composite films. The refractive indices of the semi‐IPN composite systems increased with increasing crosslinkable imide moieties due to the higher polarizabilities of atoms. The water sorption of the semi‐IPN composite films was significantly decreased by the incorporation of crosslinkable imide moieties, which are interpreted by morphological structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Formulation and curing characteristics of EPDM/NR and EPDM/SBR polyblends used in metallic surfaces rubber lining
Authors: Rezaeian Iraj , Zahedi Payam , Loghmani Motahareh Sadat
Published: March 2009

In this work, a new elastomeric liner was introduced to protect the metal surfaces of storage tanks against corroding materials in petrochemical industries. This new liner was prepared on the basis of EPDM/NR and EPDM/SBR compounds. The elastomeric compounds were cured by using super‐heated water vapor at atmospheric pressure. To increase the rate of curing in these rubber samples, the optimum curing system contained 15 phr sulfur and 1.5 phr mercaptobenzothiazole, 1.5 phr zinc diethyl dithiocarbamate, and 1.8 phr tetramethylthiuram disulfide accelerators. Mechanical tests showed that ultimate tensile strength, elongation at break, and hardness of both polyblend samples were comparable to the SBR/NR blend, which is widely used in the rubber lining of metallic surfaces. In the next step, the chemical resistance of the samples was measured by placing them in a 30 wt % HCl solution. The tensile strength, elongation at break, and weight loss of the samples were measured before and after immersion in HCl. Also, the chemical resistances for EPDM/NR, EPDM/SBR, and SBR/NR samples were qualitatively measured in caustic solution. The cracking, blistering, permeability, and adhesion of the rubber samples to steel surface were observed. Finally, the results showed that EPDM/SBR (70/30) polyblend can be a suitable substitute for conventionally used SBR/NR (50/50) for a successful rubber used to line metallic surfaces. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Polyurethane elastomers based on 1,3 and 1,4‐bis(isocyanatomethyl)cyclohexane
Authors: Xie Rui , Bhattacharjee Debkumar , Argyropoulos John
Published: March 2009

Most polyurethane elastomers in the market place are based on aromatic isocyanates. This is partially due to the higher cost of aliphatic isocyanates compared with aromatic isocyanates which are commonly used by the industry. However, more importantly, it has been the performance deficiency of polyurethane elastomers based on commercial aliphatic isocyanates that has significantly limited their use. Though aliphatic‐based polyurethane elastomers possess increased resistance to hydrolysis and thermal degradation in addition to greater light stability, these elastomers often experience a decrease in physical–mechanical properties when compared with aromatic isocyanate‐based materials. In this study, we investigated elastomers based on 1,3 and 1,4‐bis(isocyanatomethyl)cyclohexane, an experimental diisocyanate recently developed by The Dow Chemical Company. The physical properties of the elastomers are reported and discussed in comparison to similar elastomers prepared from commercially available aliphatic and aromatic isocyanates. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Fabrication of pH‐responsive molecularly imprinted polyethersulfone particles for bisphenol‐A uptake
Authors: Zhao W. F. , Fang B. H. , Li N. , Nie S. Q. , Wei Q. , Zhao C. S.
Published: March 2009

pH‐responsive molecularly imprinted particles were successfully fabricated by pore‐filling poly (acrylic acid) (PAA) gels into bisphenol‐A (BPA)‐imprinted polyethersulfone particles. The adsorbed BPA amount (or rate) decreased after filling the PAA gels both for the imprinted and nonimprinted particles. However, it was confirmed that changing the acidity of the solution reversibly controls the rebinding ability toward BPA and that the BPA uptake of the pore‐filled particles exhibited chemical valve behavior at a pH between 3 and 6. This finding can be attributed to the swelling of the PAA gels in the particles. The present methodology provides a simple way to prepare pH‐responsive molecularly imprinted materials and is expandable to the imprinting of other hydrophobic molecules, such as dibenzofuran. Also, the results of this work demonstrate the potential of stimuli‐responsive molecularly imprinted polymer materials as smart chemicals and as drug‐delivery systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Quantitative evaluation of His‐tag purification and immunoprecipitation of tristetraprolin and its mutant proteins from transfected human cells
Authors: Cao Heping , Lin Rui
Published: March 2009

Histidine (His)‐tag is widely used for affinity purification of recombinant proteins, but the yield and purity of expressed proteins are quite different. Little information is available about quantitative evaluation of this procedure. The objective of this study was to evaluate His‐tag procedure quantitatively and to compare it with immunoprecipitation using radiolabeled tristetraprolin (TTP), a zinc finger protein with anti‐inflammatory property. Human embryonic kidney 293 cells were transfected with wild‐type and nine mutant plasmids with single or multiple phosphorylation site mutation(s) in His‐TTP. These proteins were expressed and mainly localized in the cytosol of transfected cells by immunocytochemistry and confocal microscopy. His‐TTP proteins were purified by Ni‐NTA beads with imidazole elution or precipitated by TTP antibodies from transfected cells after being labeled with [32P]‐orthophosphate. The results showed that (1) His‐tag purification was more effective than immunoprecipitation for TTP purification; (2) mutations in TTP increased the yield of His‐TTP by both purification procedures; and (3) mutations in TTP increased the binding affinity of mutant proteins for Ni‐NTA beads. These findings suggest that bioengineering phosphorylation sites in proteins can increase the production of recombinant proteins. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Enzyme immobilization via silaffin‐mediated autoencapsulation in a biosilica support
Authors: Marner Wesley D. , Shaikh Afshan S. , Muller Susan J. , Keasling Jay D.
Published: March 2009

Enzymes and other biomolecules are often immobilized in a matrix to improve their stability or to improve their ability to be reused. Performing a polycondensation reaction in the presence of a biomolecule of interest relies on random entrapment events during polymerization and may not ensure efficient, homogeneous, or complete biomolecule encapsulation. To overcome these limitations, we have developed a method of incorporating autosilification activity into proteins without affecting enzymatic functionality. The unmodified R5 silaffin peptide from Cylindrotheca fusiformis is capable of initiating silica polycondensation in vitro at ambient temperatures and pressures in aqueous solution. In this study, translational fusion proteins between R5 and various functional proteins (phosphodiesterase, organophosphate hydrolase, and green fluorescent protein) were produced in Escherichia coli. Each of the fusion proteins initiated silica polycondensation, and enzymatic activity (or fluorescence) was retained in the resulting silica spheres. Under certain circumstances, the enzymatically‐active biosilica displayed improved stability relative to free enzyme at elevated temperatures. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Aerosol infectivity of a Baculovirus to Trichoplusia ni larvae: An alternative larval inoculation strategy for recombinant protein production
Authors: Jinn Tzyy‐Rong , Kao Suey‐Sheng , Tseng Yin‐Chin , Chen Ying‐Ju , Wu Tzong‐Yuan
Published: March 2009

The baculovirus–insect expression system is a popular tool for recombinant protein production. The standard method for infecting insect larvae with recombinant baculovirus for protein production involves either feeding occlusion bodies or injecting budded virus into the cuticle. In this study, we showed that the recombinant Autographa californica multiple nucleopolyhedrovirus (AcMNPV) at titers >108 pfu/mL efficiently infected Trichoplusia ni (T. ni) larvae through aerosol inoculation of budded virus at a pressure of 5.5 × 104 Pa. The dipping T. ni larvae in virus‐containing solution efficiently infected them. These results indicate that surface contamination, either by aerosol or dipping, lead to infection via spiracles. The aerosol infection route for AcMNPV was restricted to T. ni and Plutella xylostella larvae, whereas Spodoptera litura and Helicoverpa armigera larvae were resistant to this inoculation process. The yields of the reporter proteins DsRed and EGFP from T. ni larvae following aerosol infection were nearly identical to those following oral feeding or injection. This alternative baculovirus infection strategy facilitates recombinant protein and virus production by insect larvae. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Erdosteine modulates radiocontrast‐induced hepatotoxicity in rat
Authors: Yesildağ Ahmet , Özden Ahmet , Yılmaz H. Ramazan , Uz Efkan , Ağackıran Yetkin , Yesildağ Mihrican , Yılmaz Nigar , Sırmalı Rana , Vural Hüseyin , Nazıroğlu Mustafa
Published: March 2009

It has been suggested that reactive oxygen species (ROS) plays an important role in radio contrast media (RCM)‐induced ischemia reperfusion tissue injury although antioxidants may have protective effects on the injury. We investigated the effects of erdosteine as an antioxidant agent on RCM‐induced liver toxicity in rats by evaluation of lipid peroxidation (as TBARS), catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH) and glutathione peroxidase (GSH‐Px) values and histological evaluation. Twenty‐one rats were equally divided into three groups as follows: control, RCM, and RCM plus erdosteine. RCM was intraperitoneally administered for 1 day. Erdosteine was administered orally for 2 days after RCM administration. Liver samples were taken from the rats and they homogenized in a motor‐driven tissue homogenizer. TBARS levels were significantly (p < 0.005) higher in RCM group than in control although SOD activities significantly (p < 0.05) decreased in RCM group. TBARS levels were lower in RCM plus erdosteine group than in control although SOD activity and GSH level increased (p < 0.05) in liver as compared to RCM alone. Erdosteine showed also histopathological protection (p < 0.0001) against RCM induced hepatotoxicity. GSH‐Px and CAT activities were not statistically changed by the erdosteine. According to our results, it can be concluded that radiocontrast media can induce oxidative stress in liver as suggested by previous studies. Erdosteine seems to be protective agent on the radiocontrast media‐induced liver toxicity by inhibiting the production of ROS via the enzymatic antioxidant system. Copyright © 2009 John Wiley & Sons, Ltd.
Appraisal of catalysts for the hydrolysis of carbon disulfide
Authors: Tong S. , Dalla Lana I. G. , Chuang K. T.
Published: March 2009

Industrial alumina‐ and titania‐based catalysts were tested for CS2 hydrolysis in a Berty reactor. Activated bauxite is the most active catalyst below 290°C and titanium oxide above 290°C. TGA experiments examining water desorption from 50°C to 550°C showed complete desorption from titania by 300°C and continuous desorption even beyond 550°C for alumina and bauxite. Using the Kelvin equation to predict capillary condensation over the range of pore sizes of these catalysts, condensation of water vapour should be negligible but for sulfur vapour considerable blocking of pores is predicted for alumina. Much of the internal area of aluminas may thus become inaccessible to vapor molecules. These observations suggest why alumina‐based catalysts exhibit lower activity for CS2 and COS hydrolysis in modified Claus plant reactors.
Extractive fermentation systems for organic acids production
Authors: Hatzinikolaou Dimitrios G. , Wang Henry Y.
Published: March 2009

Basic characteristics of on‐line extractive fermentation of organic acids were examined using a general model for the integrated process in order to illustrate the effects of various process parameters and operational modes on system performance. The strong pH dependence of both the fermentation kinetics and the extraction efficiency has been outlined and taken into account by inclusion of a model equation which predicts the pH profile. Simulation results using data from butyric acid fermentations show that our complete model system is adequate to evaluate different operational modes of the process, including simple batch fermentation, batch or fed‐batch fermentation with extractive recycle, and continuous fermentation with extractive recycle. In the case where a second undesired acidic byproduct is also produced, our model predictions suggest that on‐line extractive fermentation using a suitable solvent results in an effective gross separation of the two acids.
The effects of arsenic and lead impurities on the current efficiency and deposit composition in alkaline zinc electrowinning
Authors: Hu Mao Pu , Piron Dominique L.
Published: March 2009

The influence of lead and arsenic impurities on zinc deposition, current efficiency and deposit composition was examined in the alkaline zinc electrowinning system. It was observed that lead slightly decreases the current efficiency of zinc deposition, and that the detrimental effect on zinc current efficiency which was observed with arsenic was largely suppressed in the presence of lead. This beneficial effect is related to the fact that the arsenic content of the deposit decreased when lead was present in the electrolyte. It was also found that arsenic promotes the deposition of lead. Tin has no effect on the current efficiency of zinc deposition in alkaline solutions, with or without arsenic. The addition of salicylaldehyde to the solution alleviates the deleterious influence of arsenic on zinc current efficiency, but it somewhat increases the cell voltage.
Effect of alumina content on surface area and micropore distribution of porous glass prepared from borosilicate glass
Authors: Takahashi Takeshige , Go‐Fua Cai , Ogura Yoshikazh , Kai Takami
Published: March 2009

The surface area and micropore distribution of porous glass prepared from borosilicate glass were controlled by the addition of alumina up to 8 wt%. The surface area increased with increased alumina content in the range from 0 to 3 wt%, but it suddenly decreased when the percent alumina exceeded 4 wt%. The mean pore diameter and micropore volume also decreased with increased alumina content. When nickel ion was supported into the porous glass, the surface area decreased to about one‐half that of the original glass. Since the amount of nickel supported on the porous glass increased directly with surface area, the silanol group was considered to be uniformly distributed on the glass.
Analyse par traitement d'images du dépôt de particules projetées par un jet gazeux sur une surface plane
Authors: Lédé J. , Cifuentes C. , Pons M. N. , Villermaux J. , Marcant S.
Published: March 2009

Le présent article a pour objet l'étude expérimentale du dépǒt de particules projetées par un jet gazeux sur une surface plane horizontale. La répartition granulométrique locale des particules déposées est analysée par une technique d'analyse d'images. Les mesures sont effectuées avec différents lots de particules et sous diverses conditions expérimentales. Les valeurs des distances d'arrět sont regroupées dans une représentation adimensionelle en fonction d'un nombre de Stokes St0 défini en sortie de buse. La finesse de la séparation granulométrique observée dans le dépǒt est enfin évaluée en fonction d'un paramètre de dispersion J.
The catalytic oxidative coupling of methane: I. Comparison of experimental performance data from various types of reactor
Authors: Do K. T. , Edwards J. H. , Tyler R. J.
Published: March 2009

The methane oxidative coupling performance of a fixed‐bed reactor was successfully translated to a bubbling fluidised‐bed reactor and this reaction mode was superior to spouted‐bed, inclined and mechanically‐agitated fluidised‐bed units. Also, a two‐stage bubbling fluidised‐bed reactor with inter‐stage addition of oxygen had the same performance as the single‐stage unit, for the same total oxygen input, over a wide range of operating conditions. Overall the bubbling fluidised‐bed is preferred, catalytic reactions dominate over non‐catalytic gas phase reactions in determining the reactor performance, the gas phase exhibited plug‐flow behaviour and the performance was independent of the gas phase oxygen partial pressure for a given oxygen input. The best hydrocarbon yield achieved in this study was 19.4%.
Diffusion coefficient of hydrogen in a Pd‐Ag membrane: Effect of hydrogen solubility
Authors: Jemaa N. , Grandjean B. P. A. , Kaliaguine S.
Published: March 2009

The permeabilities of hydrogen through a Pd75‐Ag25membrane have been measured at temperatures ranging from 423 to 573 K and under hydrogen pressure differences ranging from 69 to 256 kPa. From the available literature solubility data a neural network model has been developed in order to simulate the variation of the hydrogen content in the alloy as a function of pressure and temperature. Then, from steady state permeability measurements and calculated solubilities, the diffusion coefficients of hydrogen have been computed. At a given temperature, the diffusion coefficient has been found to decrease with the hydrogen content (0.1 ≤n= H/M ≤ 0.37). A simple relation is then suggested to predict the variation of the diffusion coefficient on both temperature and hydrogen content. To account for the variation of the diffusion coefficient with n, the integration of Fick's law of diffusion has been performed numerically, resulting in non‐linear profile of hydrogen content through the membrane under steady state permeation.
Hydrodynamics of a gas‐liquid‐solid three phase circulating fluidized bed
Authors: Liang W. , Wu Q. , Yu Z. , Jin Y. , Wang Z.
Published: March 2009

The hydrodynamics of a gas‐liquid‐solid circulating fluidized bed was investigated. A new regime, the three phase circulating fluidization regime, was discovered for the first time. The characteristics of this regime were compared with that of the conventional fluidization regime and the transport regime. The particle circulation rate and the gas and solids holdups in circulating fluidization regime were studied.
Atmospheric spouted bed combustion: The role of hydrodynamics in emissions generation and control
Authors: Konduri Ravi K. , Altwicker Elmar R. , Morgan M. H.
Published: March 2009

Recent studies have reaffirmed the utility of spouted beds as potential combustion devices for a variety of fuels: solid, liquid and gaseous fuels (Arbib and Levy, 1982; Weinberg et al., 1988; Zhao et al., 1987; Altwicker et al., 1989; Altwicker and Lin, 1991; Altwicker et al., 1993; Konduri et al., 1994). In this study, the role of annulus residence time on the performance of such a spouted bed combustor is investigated. The experiments presented here show that fluid hydrodynamics in the annulus of a spouted bed combustor can significantly influence the overall performance; changing the residence time in the annulus significantly affects the concentrations of products due to incomplete combustion at the exit of the combustor. The annular residence time is varied by changing the shape of the bottom of the reactor, by introducing a draft tube and by changing the bed heighn. Propane is used as the fuel and sand as the bed medium. Inferences from the combustion results are supported by pressure and temperature profiles. A streamtube model (Lim and Mathur, 1976) was used to obtain an estimate of the residence time in the annulus. It is concluded that the flame processes taking place at the top of the annulus play a critical role in the emission generation and that more information is needed to understand the annulus‐flame.
Isobaric vapour‐liquid equilibrium for the binary mixtures of 1‐bromobutane with isomeric butanols at 40.0 and 101.3 kpa
Authors: Artigas Hector , Cea Pilar , Dominguez Magdalena , Royo Felix M. , Urieta Jose S.
Published: March 2009

A dynamic recirculating still was employed to measure isobaric vapour‐liquid equilibrium at 40.0 and 101.3 kPa for the binary systems 1‐bromobutane and each of the isomers of butanol. All mixtures show azeotropes at both pressures. The experimental VLE data are thermodynamically consistent and were correlated using Margules, Van Laar, Wilson, NRTL and UNIQUAC equations.
Operations optimization and control design for a petroleum distillation process
Authors: Mizoguchi Atsushi , Marlin Thomas E. , Hrymak Andrew N.
Published: March 2009

Process automation involves both steady‐state optimization and feedback control. In this paper, the economic optimum steady‐state operating conditions for a petroleum crude distillation process are determined using a tray‐to‐tray model. This model is used to evaluate the steady‐state operation achieved with several multivariable process control designs. Only one controller design was found to result in essentially optimum steady‐state operation; others deviated significantly. The method applied in this paper relies on a knowledge of the key disturbances occurring in the process; good economic performance may not be obtained should other disturbance types occur. The results demonstrate the importance of implementing the operations optimization through a control strategy which will respond properly to disturbances.
The effect of geometrical parameters on the flow field of an opposed jet rim mix head: Equal flow and matched fluids
Authors: Johnson David A. , Wood Philip E. , Hrymak Andrew N.
Published: March 2009

The effect of geometrical parameters on the flow field present in the mix head used in reaction injection molding (RIM) are presented for Red (Red = 4Q/πdv, nozzle diameter d, fluid kinematic viscosity v and the volumetric flow rate Q through the nozzle) representative of commercial practice. Quantitative velocity measurements of the flow field in a mix head have not been reported in the literature despite the extensive use of the mix head for reaction injection molding. Flow visualization and velocity measurements using a laser Doppler anemometer have been obtained for different values of geometrical parameters such as mix chamber diameter (D), distance from the nozzle inlet to the closed end of the chamber (H), and nozzle needle position (N). The ratio of the mix chamber to nozzle diameter (d) (D* = D/d) was a significant parameter affecting the flow field. The distance from the impingement point to the closed end of the chamber was found to have little effect on the observed flow field beyond the impingement area. A nozzle needle position that partially constricted the nozzle opening was found to decrease the axial distance to unidirectional flow within the mix chamber.
Axial dispersion in a reciprocating plate column
Authors: Lounes Mustapha , Thibault Jules
Published: March 2009

Axial mixing in a reciprocating plate column with different amplitudes has been investigated for single‐phase and two‐phase (air‐water) systems. Experiments were performed in water in a semi‐batch scheme (no water flow) in a 1.26 m high and 101.6 mm internal diameter column.

It was found that the axial dispersion coefficient is a strong function of reciprocation speed and amplitude. The presence of gas considerably affects the axial dispersion coefficient but its contribution appears to saturate at low gas flow rates and then, over a large range of gas flow rates, the axial dispersion coefficient was almost constant. Models are proposed based on experimental data to account for the effects of gas superficial velocity, amplitude and reciprocating frequency. The models predictions are compared with experimental data, obtained over a wide range of operating conditions, and the agreement between them was found to be good. A new class of nonlinear models, for which it is not necessary to have a constant dependency on each operating variable, was also used to correlate the axial dispersion coefficient. This new model allows to carry out sensitivity analysis on each operating variable.
A new investigation of the metzner‐otto concept for anchor mixing impellers
Authors: Tanguy P. A. , Thibault F. , De La Fuente E. Brito
Published: March 2009

Anchor impellers are commonly used for the homogenization of non‐Newtonian fluids, often in association with a set of coaxial turbines. The optimal design of such mixers relies on the knowledge of power drawn by the individual impellers. In non‐Newtonian mixing, this can be readily obtained using the Metzner‐Otto (1957) concept. In this article, the Metzner‐Otto concept and the determination of the constant Ks for anchor impellers have been revisited using numerical and experimental techniques for the case of shear‐thinning and shear‐thickening fluids. Contrary to literature findings, it is shown that the constant Ks does not vary strongly with the power law index and that, for mixer design purposes, the use of a constant value of Ks for each of the rheological behaviors considered is adequate.
A study of autoxidation reaction fouling in heat exchangers
Authors: Wilson D. Ian , Watkinson A. Paul
Published: March 2009

The mechanism of autoxidation reaction fouling in single phase liquid heat transfer under turbulent flow conditions was studied using model solutions of indene in lube oil recirculated through a tubular fouling probe which permitted both thermal and mass deposition measurements. The fouling rate was initially constant, and then accelerated as polyperoxide gums reached their solubility limit. Deposit composition and morphology in the tubular device are compared with results obtained in an annular probe with a short heated length. The initial fouling data collected over surface temperatures of 180−255°C and flow velocities of 0.5–2.6 m/s (Re = 3000 − 16000) gave reasonable agreement with a boundary layer reaction model.
Impurity effects on crystallization of KCL from aqueous solutions in a MSMPR crystallizer
Authors: Dash S. R. , Rohani S. , Sokhansanj S.
Published: March 2009

Extensive experimental investigations into the effect of magnesium and sulfate ionic impurities on cooling crystallization of KCl were carried out in a steady‐state Mixed Suspension Mixed Product Removal (MSMPR) crystallizer. The impurities selected for investigation were chosen from those naturally associated with KCl in potash industry. Eighty one experiments were performed in a factorial experimental design scheme. The results exhibited that magnesium ion did not have any significant influence upon crystallizations of KCl, while the sulfate ion enhanced the aggregation rate. The nucleation rate was only slightly affected by the presence of impurities. The size enlargement in presence of sulfate ion was ascribed to an increase in aggregation rate. It was demonstrated that the role of the impurities studied upon KCl crystallization is consistent and predictable and is a function of the chemical character of the impurity species. Based on these results two mechanisms for size enlargement were identified, first due to crystal growth by solid deposition and second due to aggregation. Aggregation was found to be the governing mechanism for producing large crystals.
Mechanical behaviour of highly filled lignin/polyethylene composites made by catalytic grafting
Authors: Casenave S. , Aït‐Kadi A. , Riedl B.
Published: March 2009

Highly filled lignin/polyethylene composites, with enhanced mechanical properties, were studied. Composites are prepared using the catalytic grafting technique of polyethylene on lignin particles. This technique improves wetting and dispersion of additives in the matrix as well as interactions between these two components. Mechanical properties (tensile and impact) and morphology of the composites were measured. The experimental results showed that highly filled HDPE/lignin composites (up to 73 vol%) could be produced by catalytic grafting. Tensile properties of the composites were quantitatively analysed using a micromechanical model for particulate composites based on an energy balance. Model predictions for Young's modulus are in excellent agreement with experimental results. The adjustable parameters of the model were varied from one composite to the other in a way which corresponds to the basic concepts related to particulate composites in general and to catalytic grafting in particular.
Modeling of approach processes for equal or unequal sized fluid particles
Authors: Svendsen Hallvard F. , Luo Hean
Published: March 2009

The approach of two unequal or equal sized fluid particles is modeled using a simple parallel film model, giving expressions for interaction time and maximum film area, disregarding all external forces. The interaction time is found independent of the initial approach velocity and it explains why the effective virtual mass coefficient changes with the radius ratio of particles in the model of Chesters and Hofman (1982). A more general parallel film model is also developed based on the balance of forces acting on the particles and shows how initial velocity, radius ratio and buoyancy affect the interaction time, approach velocity and film area. Both models are compared to the experimental data of Scheele and Leng (1971).
Electrooxidation of Diacetone ‐L‐Sorbose (DAS) into Diacetone‐2‐Keto‐L‐Gulonic acid (DAG) at nickel electrodes
Authors: Lyazidi H. Ait , Benabdallah M. Z. , Berlan J. , Kot C. , Fabre P.‐L. , Mestre M. , Fauvarque J.‐F.
Published: March 2009

The oxidation of diacetone‐L‐sorbose (DAS) into diacetone‐2‐keto‐L‐gulonic acid (DAG) is a step in the synthesis of vitamin C. This oxidation was carried out electrochemically in a stirred cell with the redox couple Ni (OH)2/β‐NiOOH as an electrochemical mediator. The anode was made of a current collector (nickel foam or platinized‐titanium) and of a suspension of Ni(OH)2 in KOH aqueous media. The mediated electrooxidation of DAS was achieved by the Ni(OH)2β‐NiOOH couple in solution which was regenerated at the current collector. This process required a two‐compartment reactor but afforded high yields of chemical conversion: we obtained 96% with a 48% faradaic yield. Previous works dealing with DAS electrooxidation to DAG on nickel anode are reviewed hereafter.
Mass transfer behaviour of a fixed bed electrochemical reactor with a gas evolving upstream counter electrode
Authors: Sedahmed G. H.
Published: March 2009

Mass transfer rates were determined at a horizontal screen cathode stirred by oxygen bubbles evolved at a horizontal anode placed below the screen by measuring the limiting current of the cathodic reduction of ferricyanide ion from alkaline solution. Variables studied were oxygen discharge rate, ferricyanide concentration and number of closely packed screens forming the cathode. For a single screen cathode the data were correlated by the equation:

J = 0.249 (Re Fr)‐0.25

The mass transfer coefficient was found to decrease with increasing the number of screens forming the cathode. Implications of the present work for improving the performance of the flow‐through packed bed electrochemical reactor were highlighted.
Simulation and optimization of cellulose and styrene graft copolymerization process
Authors: Bataille P. , Statioukha G. , Statioukha O.
Published: March 2009

Graft polymerization of styrene into cellulose was investigated using Ceric ions redox systems as initiator. A mathematical model with the D‐optimal design combined with the least squares method was applied to the system. The variables considered in the model are the reactant variables i.e. monomer and initiator concentrations and the processing variables i.e. reaction time, temperature and agitation rate. The optimal composition and processing conditions were determined using a three dimensional space analysis.
A predictive neural network model based on the karhunen‐loéave expansion for wall‐cooled fixed‐bed reactors
Authors: Zhou Xing‐Gui , Liu Liang‐Hong , Yuan Wei‐Kang , Hudson J. L.
Published: March 2009

Experiments were carried out with a pilot scale, wall cooled, fixed‐bed reactor for benzen oxidation. The inlet concentration of benzene was varied in three ways: periodically, with PRBS, and by means of a step change. A model for the reactor is developed with use of the Karhunen‐Loéve (K‐L) expansion and neural networks. The K‐L expansion procedure used here acts as a preprocessor to achieve good data compression while preserving as much information about the measurements as possible. A recurrent multilayer feedforward network is then used to relate the coefficients of the K‐L expansion to the operating conditions. The model developed is used for on‐line prediction of the axial temperatures in a fixed‐bed reactor and results show that the predictions are in good agreement with measurements.
Control of a nonadiabatic packed bed reactor under periodic flow reversal
Authors: Budman Hector , Kzyonsek Mark , Silveston Peter
Published: March 2009

A full parametric study of the open‐loop behavior of a packed bed reactor‐recuperator system operating under periodic flow reversal produced a series of parametric maps which slow regions of operating conditions for which the system exhibits runaway, stable operation or extinction of the reaction. The reaction is CO oxidation over a Pt/alumina catalyst. A set of optimal operating conditions in terms of cycle time and heat transfer coefficient can be directly extracted from the parametric maps.

A preliminary study on the control of periodic flow reversal tested and compared two strategies. 1) feedback PID control of the exit CO concentration and 2) model based feedforward control.
Bleach activation of thermomechanical pulp
Authors: Sain M. M. , Daneault C. , Parenteau M.
Published: March 2009

Under mild alkaline condition the bleaching activator tetraacetyl ethylenediamine (TAED) forms peroxyacetic acid with sodium perborate and improves the brightness of thermomechanical pulp. The activator makes it possible to bleach the pulp efficiently even without addition of sodium hydroxide at any temperature in the range 40 to 70°C. A mathematical model has been proposed to allow estimation of the total peroxy acid consumption during activated bleaching process. Using this model it is possible to calculate the extent of peroxy acid decomposition by predetermining the rate constant and activation energy. The effect of bleach activation was found to be maximum at temperatures below 60°C. The influences of bleaching time, pH, consistency, temperature and TAED charge on the bleach activation has been evaluated. The activator is effective enough to improve the brightness of sodium perborate bleached pulp at an average charge of about 50 mass% of sodium perborate. Apparently, high consistency dispersive bleaching without free alkali is a technological and economic advantage of the process.
Étude comparative de flux et de performances lors du traitement d'effluent papetiers par bioréacteur à membranes
Authors: Dufresne Robert , Lebrun R. E. , Lavallée H. C.
Published: March 2009

Le but de cette étude est d'évaluer le rôle des membranes à l'intérieur des bioréacteurs à membranes (BRM) et de mod‐éliser les flux. Deux modèles, développés pour les bioréacteurs à membranes externes, ont permis de quantifier l'importance de la concentration des solides en suspension de la liqueur mixte. L'effet des rétrolavages est également quantifié. Une comparaison des performances de BRM équipés de membranes avec des seuils de coupure différents, a permis de démontrer l'importance prédominante de la couche de boues (à la surface et à l'intérieur des pores des membranes) par rapport au seuil de coupure.
A new method to determine the composition of biomass by thermogravimetric analysis
Authors: Cozzani Valerio , Lucchesi Aldo , Stoppato Giusto , Maschio Giuseppe
Published: March 2009

A method for the direct determination of the cellulose and lignin content of biomass has been developed. The method assumes that negligible interactions exist between biomass macrocomponents and it is based on the analysis of thermogravimetric (TG) pyrolysis data. The TG‐weighed sum method seems to be reliable and less time consuming than conventional methods for the determination of the cellulose and lignin content. Some limitations of the macrocomponent approach in the description of biomass pyrolysis are also discussed. In particular, hemicellulose pyrolysis data are analyzed. The use of xylans as substitute materials for hemicellulose have been critically examined. The results obtained point out that the widely practiced use of xylans as substitute compounds for the simplified description of hemicellulose pyrolysis can lead to significant errors.
Performance assessment of multivariate control loops on a paper‐machine headbox
Authors: Huang Biao , Shah Sirish L. , Kwok K. Ezra , Zurcher Jim
Published: March 2009

A large number of control loops in the pulp and paper industry are multivariate in nature. The main control objective of these loops is to reduce process variation. The satisfactory performance of these loops is therefore important for maintaining product quality. This paper introduces a multivariate performance measure of such control loops. The multivariate minimum variance control performance which provides an absolute lower bound on process variance can be estimated from routine operating data, and serves as a good benchmark to assess control loop performance. The proposed measure of performance is evaluated by application to the multiloop control of a headbox machine.
Etude de l'oxydation du pentachlorophénol dans différentes géométries de réacteurs à ultrasons de haute fréquence
Authors: Gonze E. , Gonthier Y. , Boldo P. , Bernis A.
Published: March 2009

Nous avons entrepris de déterminer les paramétres géometriques fondamentaux intervenant dans la modélisation d'un réacteur à ultrasons de haute fréquence. Une méthodologie permettant de caractériser les différents réacteurs réalisés au laboratoire a été mise au point. Elle comprend: la mesure de la calorimétrie, la détermination de la distribution des temps de séjour, I'observation de la chimiluminescence du luminol et le suivi de la dégradation de solutions de penta‐chlorophénol. A I'issue de la caracténsation des réacteurs étudiés, il semble que la puissance volumique, à systéme émet‐teur équivalent, soit le paramétre qui conditionne le fonctionnement du réacteur.
Prediction of optimum operating conditions of liquid fluidized bed systems
Authors: Jamialahmadi M. , Malayeri M. R. , Müller‐Steinhagen H.
Published: March 2009

An important advantage of fluidized beds applied in various chemical and physical operations is the high rate of heat transfer between the bed and the heat transfer surfaces. However, the design of these systems for optimum conditions remains uncertain and essentially empirical. In this study a model for bed voidage and a model for heat transfer are presented which can be used to predict the maximum attainable heat transfer coefficient and the corresponding bed voidage of liquid fluidized bed systems with good accuracy.
Study of humic acid adsorption on nanofiltration membranes by contact angle measurements
Authors: Bouchard C. R. , Jolicoeur J. , Kouadio P. , Britten M.
Published: March 2009

Membrane fouling is a major problem, which extent depends on the respective natures of the solute and membrane material. Membrane surface characterization under different fouling conditions may help in understanding the fouling mechanism. Such characterization was performed for the case of humic substances filtered on two nanofiltration membranes, using special contact angles measurements. The measured contact angles allowed the calculation of polar and non‐polar contributions to the surface energy of dry, hydrated and fouled membranes. The results reveal significant differences in the two membrane behaviours and information about the way that fouling material may be adsorbed on membrane surface.
Modeling of multi gas—solid reactions: A transient model
Authors: Abba I. A. , Hastaoglu M. A.
Published: March 2009

A rigorous multicomponent multi gas‐solid reaction model is developed. It is based on the particle — pellet model and considers the transient nature of the system, inter‐ and intra‐particle heat and mass transfer and the variation of structural parameters with reaction. The model equations describing the structural changes along with property evaluation schemes are formulated for a general multicomponent system. Simulation results are compared with experimental data for carbon gasification and the reduction of a nickel oxide/hematite mixture. The match between model and experiment was found satisfactory. Both concentration and temperature profiles and other parameters are examined.
Optimal control of final state constrained systems
Authors: Mekarapiruk Wichaya , Luus Rein
Published: March 2009

In using penalty functions to handle final state equality constraints, we propose a systematic scheme for adjusting the penalty function factors, so that all the constraints are satisfied within a specified tolerance, and so that the performance index is minimized. Two typical engineering problems, which are used to test the procedure, show that the proposed method of adjusting the penalty function factors can be used for reasonably complex systems to yield reliable results.
Effect of catalyst loading on gasliquid mass transfer in a slurry reactor: A statistical experimental approach
Authors: Inga Juan R. , Morsi Badie I.
Published: March 2009

A statistical experimental design was employed to study the effects of pressure, temperature, catalyst loading, and mixing speed on the solubilities (C*) and volumetric gas/liquid mass transfer coefficients (kLa) for H2, N2, CO, CH4 and C2H4 in a liquid mixture of hexanes containing iron oxide catalyst in a 4‐litre agitated autoclave. Statistical correlations for kLa values for the gases used were developed. Mixing speed and solid concentration showed the strongest effects on kLa. At low catalyst concentrations, a maximum in kLa was observed and at concentrations > 37 mass%, kLa decreased by more than one order of magnitude.
Etude numérique et paramétrique de la combustion de particules d'aluminium
Authors: Basse T. , Daniel E. , Loraud J. C.
Published: March 2009

Dans le but de prendre en compte la réactivité des particules d'aluminium issues de la combustion des pains de prop ergol solide qui sont placés dans les lanceurs spatiaux, plusieurs modèles numériques ont été éprouvés. Notre choix s'est rapidement porté sur le modèle de Law puisqu'il permet de transiter continǔment d'une goutte d'aluminium à une goutte d'oxyde et de connaǐtre la taille du residu en fin de combustion ceci pouvant expliquer les dépǒts importants observés dans les moteurs fusée. En vue d'y étudiér les couplages écoulement / combustion, la combustion de gouttes d'aluminium a été largement analysée au travers de calculs 0D mettant en évidence les principaux rouages du processus de combustion.
The characterization of solid residues from PFBC boilers
Authors: Anthony Edward J. , Iribarne Agripina P. , Iribarne Julio V.
Published: March 2009

PFBC is one of the two important advanced fossil fuel technologies, now available. It permits the combustion of fossil fuels with extremely low emissions, while also achieving high electrical conversion efficiencies. However, relatively little is known about the ash characteristics, despite the existence of several demonstration units. This study looks at bed and cyclone ash from two of these boilers, the Spanish PFBC plant at Escatron in Spain, and the Tidd plant in Brilliant, Ohio. In particular, these ashes are examined using both conventional and some newly developed techniques in order to determine their chemical speciation. This work confirms the ashes have extremely low free lime contents (1% or less), and extremely low elemental carbon. More surprisingly, the existence of significant amounts of dolomite in the cyclone ashes from the Tidd plant has been demonstrated, and significant quantities of other calcium compounds (i.e. silicates, ferrites etc.) have also been shown in the bed ashes from the Spanish plant. One other interesting observation is the presence of low levels of sulphides in the ashes from the Escatrón unit, and its total absence from the Tidd unit which used dolomite rather than calcitic limestone. These results also clearly indicate that ashes from PFBC plants are likely to be significantly easier to dispose of in landfills than AFBC ashes, and should have considerably better potential for use in cemen‐titious applications.