bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Resonance Imaging of the Hand in Systemic Sclerosis
Authors: LOW ANDREA H.L. , LAX MATTHEW , JOHNSON SINDHU R. , LEE PETER
Published: March 2009

Objective.

To evaluate the utility of magnetic resonance imaging (MRI) in systemic sclerosis (SSc)-associated arthropathy.

Methods.

MRI of the hand was performed in patients presenting with joint pain/swelling in order (1) to determine the frequency of inflammation on MRI, and (2) to compare MRI with radiography.

Results.

Of 17 patients with SSc, 10 (59%) had inflammatory MRI findings with synovitis (n = 8), erosions (n = 7), joint effusion (n = 7), or tenosynovitis (n = 8). Bone edema was present in 9 patients. Of 7 patients with MRI erosions, only 2 had radiographic erosions.

Conclusion.

Our study illustrates the usefulness of MRI in the accurate diagnosis and characterization of SSc-associated arthropathy.
La folle du maquis, ou l’imagination en liberté
Authors: Breeur Roland
Published: March 2009

Para Sartre, una imagen no es una cosa, sino un acto de conciencia. Imaginar algo es una forma de ser consciente de algo, es decir, es intencional. En este sentido, la ima ginación nunca es una forma de percepción, ni siquiera una falsa: ella no percibe imágenes, sino que las forma. Está claro que Sartre desarrolló su noción fenomenológica de la imaginación como radicalización de ciertas intuiciones husserlianas. Pero en mi contribución quiero integrar su interpretación radical y estimulante en el contexto de la tradición filosófica francesa: Descartes, Malebranche, Alain. Reparar en las similitudes y diferencias de la concepción de Sartre con su propia tradición nos permite apreciar la originalidad y particularidad de su proyecto.
Hacia una fenomenología negativa de los sueños
Authors: Schutz Gabriel
Published: March 2009

En la primera parte del ensayo, describo fenomenológicamente la transición entre el soñar y la vigilia, a fin de determinar si de este umbral puede resultar un recuerdo-de-sueño fiable (pues no tenemos otra evidencia sobre los sueños sino nuestros recuerdos). La descripción muestra que sí y señala a la vez las condiciones requeridas para aprehender los sueños de modo de no inocularles determinaciones que les son ajenas. La “actitud” así sugerida encuentra su expresión teórica en una fenomenología negativa de los sueños, es decir, una fenomenología que sólo los describe por aquello que no son. Esta primera parte permite, además, explicar el olvido de los sueños y los casos en los que se tiene conciencia de estar soñando. La segunda parte es un esbozo de fenomenología negativa; muestra que aquellas atribuciones que consisten en calificar a los sueños, o adjudicarles sentidos ocultos y originarios que requieren ser descifrados (o interpretados), o una teleología propia, son, al igual que ciertas atribuciones positivas (i.e. que parten por decir: “Los sueños son así y así”), sinsentidos. Las conclusiones dejan ver la continuidad entre la “fenomenología del umbral” de la primera parte, y la fenomenología negativa de los sueños, de la segunda.
Variation in P2RX7 candidate gene (rs2230912) is not associated with bipolar I disorder and unipolar major depression in four European samples
Authors: Grigoroiu‐Serbanescu Maria , Herms Stefan , Mühleisen Thomas W. , Georgi Alexander , Diaconu Carmen C. , Strohmaier Jana , Czerski Piotr , Hauser Joanna , Leszczynska‐Rodziewicz Anna , Jamra Rami Abou , Babadjanova Gulia , Tiganov A. , Krasnov V. , Kapiletti Sofia , Neagu Ana Iulia , Vollmer Jennifer , Breuer René , Rietschel Marcella , Nöthen Markus M. , Cichon Sven , Propping Peter
Published: March 2009

Two recent studies reported evidence for association between genetic variation of the positional candidate gene P2RX7 on chromosome 12q24 and bipolar I disorder (BPI) [Barden et al. (2006); Am J Med Genet Part B 141B:374–382; McQuillin et al. (2008); Mol Psychiatry 13:1‐7] and one study found association with unipolar major depression (Mdd‐UP) [Lucae et al. (2006); Hum Mol Genet 15:2438–2445]. In the present work, we aimed to replicate the SNP that showed the strongest association in the above‐mentioned studies, namely rs2230912 (P2RX7‐E13A) resulting in a change of the amino acid glutamine to arginine at position 460 (Gln460Arg), in four European bipolar I disorder samples from Germany, Poland, Romania, and Russia totaling 1,445 patients, in a German sample of recurrent Mdd‐UP patients (N = 640), and a control sample of 2,006 subjects. We found no allelic or genotypic association between rs2230912 and BPI or Mdd‐UP both in the national samples and in the combined European patient sample. Additional studies are needed to clarify the potential involvement of P2RX7 and of SNP rs2230912 in the etiology of major affective disorders. © 2009 Wiley‐Liss, Inc.
Chirality Change of Chloronitrobenzene on Au(111) Induced by Inelastic Electron Tunneling
Authors: Simic‐Milosevic Violeta , Meyer Jörg , Morgenstern Karina
Published: March 2009

Chirality chameleon: Inelastic electron tunneling manipulation can be used to change a single chloronitrobenzene (ClNB) molecule, randomly adsorbed on Au(111), into its desired enantiomeric form (r or l, see STM images and ball‐and‐stick representation) and to vary its rotational orientation. The different threshold voltages for chirality change (260 mV) and rotation (380 mV) allow these processes to be induced separately.

magnified image
Preparation and characterization of poly(butylene terephthalate) nanocomposites with various organoclays
Authors: Nirukhe Ashwini B. , Shertukde V. V.
Published: March 2009

Layered‐silicate‐based polymer–clay nanocomposite materials were prepared depending on the surface modification of montmorillonite (MMT). Nanocomposites consisting of poly(butylene terephthalate) (PBT) as a matrix and dispersed inorganic clay modified with cetyl pyridinium chloride (CPC), benzyl dimethyl N‐hexadecyl ammonium chloride, and hexadecyl trimethyl ammonium bromide by direct melt intercalation were studied. The organoclay loading was varied from 1 to 5 wt %. The organoclays were characterized with X‐ray diffraction (XRD) to compute the crystallographic spacing and with thermogravimetric analysis to study the thermal stability. Detailed investigations of the mechanical and thermal properties as well as a dispersion study by XRD of the PBT/clay nanocomposites were conducted. X‐ray scattering showed that the layers of organoclay were intercalated with intercalating agents. According to the results of a differential scanning calorimetry analysis, clay acted as a nucleating agent, affecting the crystallization. The PBT nanocomposites containing clay treated with CPC showed good mechanical properties because of intercalation into the polymer matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The evolutionary context of robust and redundant cell biological mechanisms
Authors: Delattre Marie , Félix Marie‐Anne
Published: March 2009

The robustness of biological processes to perturbations has so far been mainly explored in unicellular organisms; multicellular organisms have been studied for developmental processes or in the special case of redundancy between gene duplicates. Here we explore the robustness of cell biological mechanisms of multicellular organisms in an evolutionary context. We propose that the reuse of similar cell biological mechanisms in different cell types of the same organism has evolutionary implications: (1) the maintenance of apparently redundant mechanisms over evolutionary time may in part be explained by their differential requirement in various cell types; (2) the relative requirement for two alternative mechanisms may evolve among homologous cells in different organisms. We present examples of cell biological processes, such as centrosome separation in prophase, spindle formation or cleavage furrow positioning, that support the first proposition. We propose experimental tests of these hypotheses.
Classification of sequence signatures: a guide to Hox protein function
Authors: Merabet Samir , Hudry Bruno , Saadaoui Mehdi , Graba Yacine
Published: March 2009

Hox proteins are part of the conserved superfamily of homeodomain‐containing transcription factors and play fundamental roles in shaping animal body plans in development and evolution. However, molecular mechanisms underlying their diverse and specific biological functions remain largely enigmatic. Here, we have analyzed Hox sequences from the main evolutionary branches of the Bilateria group. We have found that four classes of Hox protein signatures exist, which together provide sufficient support to explain how different Hox proteins differ in their control and function. The homeodomain and its surrounding sequences accumulate nearly all signatures, constituting an extended module where most of the information distinguishing Hox proteins is concentrated. Only a small fraction of these signatures has been investigated at the functional level, but these show that approaches relying on Hox protein alterations still have a large potential for deciphering molecular mechanisms of Hox differential control.
Analytical effectiveness calculations concerning the formation of an inhibitive fermentation product associated with growth of biomass films immobilized in or around carriers
Authors: Van Ede C. J. , Dijkman H. , Beenackers A. A. C. M.
Published: March 2009

A reaction engineering model is presented for the bioproduction of chemicals associated with the growth of immobilized biomass in or around carriers. The model describes multiple‐substrate diffusion limitations and first‐order growth inhibition by one of the products.

Analytical solutions are presented for intra‐biofilm substrate and product concentrations, active biofilm thickness, biocatalyst effectiveness factor and degree of catalyst utilization. Simple criteria for optimal catalyst design are derived. Where applicable, the presented explicit analytical solutions for the biocatalyst effectiveness factor are much more convenient to incorporate into a macro‐reactor model than the numerical alternatives.
An empirical mixing rule for estimating mean ionic activity coefficients in multielectrolyte solutions from binary data only
Authors: Haghtalab A. , Vera J. H.
Published: March 2009

An empirical mixing rule is proposed for mean ionic activity coefficient of electrolytes in multielectrolyte mixtures. The mean activity coefficients are calculated from data of the constituent binary single‐salt water solutions only. Using the mixing rule, the trace mean activity coefficients and the Harned's coefficients of electrolytes in ternary mixtures with and without a common ion are predicted and compared with literature data. The agreement of the calculated values with the experimental data is very good, particularly for systems which follow Brönsted ion interaction theory. Calculations for sea water are presented as example for multielectrolyte systems. The predictions agree well with experimental data.
Liquid holdup in gas‐liquid cocurrent downflow through packed beds
Authors: Venkata Ratnam G. S. , Varma Y. B. G.
Published: March 2009

The average in situ volume fraction of the liquid phase for gas‐liquid cocurrent downflow through packed beds is correlated to the input volume fraction of the liquid and the bed geometry. The range of operation is delineated into a high‐interaction regime and a low‐interaction regime based on the influence of the gas rate on the liquid holdup. Experimental data of the present investigation using air‐water and air‐CMC solutions, as well as that reported in literature covering a wide range in variables, are considered in the development of correlations for total and dynamic liquid holdup.
Fed‐batch digestion of insoluble solid‐state substrates
Authors: Huang Shih‐Yow , Chou Ming‐Shean
Published: March 2009

Performance equations for the fed‐batch digestion of insoluble solid‐state substrates were developed based on a verified interfacial kinetic model for microbial uptake of these substrates. Fed‐batch anaerobic digestions of a suspension of stearic acid with a mean particle size of 2 μm were conducted to verify the derived equations. Agreement between the experimental and calculated results indicated the validity of these equations. The performance equations should be useful for describing the time courses of cell growth, substrate consumption and product accumulation in a fed‐batch digestion system with insoluble solid‐state organics as substrate.
Distribution des temps de séjour en écoulement tourbillonnaire annulaire induit par une entrée tangentielle du liquide
Authors: Legentilhomme P. , Legrand J.
Published: March 2009

Ce travail est consacré à la modélisation globale, à partir de la détermination expérimentale de la distribution des temps de séjour, de l'écoulement dans une cellule annulaire équipée de différents systèmes d'alimentation, pour des nombres de Reynolds compris entre 100 et 5000. En utilisant le modèle piston avec dispersion axiale, puis par l'association en série de réacteurs piston et parafaitement agité, nous montrons que l'écoulement tourbillonnaire non‐entretenu produit par une entrée tangentielle présente un caractère piston très prononcé, associé à une zone agitée due au système d'entrée‐sortie du fluide dans la cellule. L'utilisation d'une entrée axiale ou perpendiculaire à la cellule diminue le pourcentage du volume total du réacteur siège d'un écoulement piston par rapport à celui déterminé en employant une entrée tangentielle.
Prediction of heat transfer to liquid‐solid fluidized beds
Authors: Jamialahmadi M. , Malayeri M. R. , Müller‐Steinhagen H.
Published: March 2009

Heat transfer coefficients to a liquid‐solid fluidized bed in a cylindrical tube have been measured using water as liquid phase and three types of cylindrical steel particles, as well as glass, nickel, copper and lead spheres of different sizes as solid phase. The independent varaibles included heat flux, liquid velocity and particle physical properties. The experimental results as well as a data bank containing a large number of measured heat transfer coefficients for solid‐liquid fluidization over a wide range of operational parameters have been compared with the predictions of most published correlations. A model for the prediction of heat transfer coefficients is proposed which predicts the present experimental data and the data of other investigators with good accuracy.
Isoelectric precipitation of sunflower protein in a tubular precipitator
Authors: Raphael M. , Rohani S. , Sosulski F.
Published: March 2009

Isoelectric precipitation of sunflower protein was carried out in a 10‐m long, 6‐mm internal diameter glass tubular precipitator. The effects of feed flow rate, protein concentration in the feed stream, and volumetric feed ratio of precipitant (HCl aqueous solution) to protein solution on solid protein recovery and particle size distribution were studied. The dispersion range of the tubular precipitator was modelled to predict the experimental results. Calculated initial growth rates of protein particles were found to: increase with increases in feed flow rate and protein concentration in the feed stream, and decrease with increases in volumetric feed ratio.
Determination of minimum fluidization velocity by pressure fluctuation measurement
Authors: Wilkinson Derek
Published: March 2009

Using the standard deviation of pressure fluctuations to find the minimum fluidization velocity, Umf, avoids the need to de‐fluidize the bed so Umf, can be found for operational bubbling fluidized beds without disrupting the process provided only that the superficial velocity may be altered and that the bed remains in the bubbling fluidized state.

This investigation has concentrated on two distinct aspects of the pressure fluctuation method for Umf determination: (1) the minimum number of pressure measurements required to obtain reliable estimates of standard deviation has been identified as about 10000 and (2) pressure fluctuation measurements in the plenum below the gas distributor are suitable for Umf determination so the problems of pressure probe clogging and erosion by bed particles may be avoided.
A two‐dimensional model for gas mixing in the upper dilute zone of a circulating fluidized bed
Authors: Kruse M. , Schoenfelder H. , Werther J.
Published: March 2009

Based on measurements in a circulating fluidized test unit with a riser of 0.4 m i.d., a two‐dimensional two‐phase model for gas mixing has been developed. Radial gas dispersion and gas backmixing caused by dense clusters falling countercurrently to the main flow of a lean gas/solid suspension are considered. The model has successfully been compared with experimental data over a wide range of operating conditions. The model accounts for the main mixing phenomena and may be applied to calculations of chemical reactions in CFB risers.
Cocurrent downflow circulating fluidized bed (downer) reactors — A state of the art review
Authors: Zhu J.‐X. , Yu Z.‐Q. , Jin Y. , Grace J. R. , Issangya A.
Published: March 2009

In the last decade, cocurrent downflow circulating fluidized bed reactors, called “downer” reactors, have been proposed as an alternative to upflow circulating fluidized bed, or “riser”, reactors. In this paper, published results on downer studies are summarized and future directions of research are recommended. Downer reactors are shown to have several distinct advantages over upflow circulating fluidized bed reactors and can potentially be used in many industrial processes, mainly due to a more uniform gas and solids flow structure compared with risers.
A generic algorithm for optimization of CFSTRs in series with any biokinetic equation
Authors: Baheri H. R. , Hill G. A. , Roesler W. J.
Published: March 2009

A simple generic code for optimization of CFSTRs in series with any biokinetic equation (structured, unstructured, segregated or distributed) has been developed. The program accepts biokinetic equations without any preliminary mathematical manipulation, does necessary material balances, solves material balance equations and optimizes the system under a given objective function. The program was tested with four different optimization problems (different biokinetics of unstructured, segregated and a structured model) and the results were compared to published data. In all cases, good agreement was found. Finally, the model has been applied to multiple CFSTRs with a cybernetic biokinetic model, and the effect of model parameters on the optimum total residence time is demonstrated.
Fine particle deposition in laminar and turbulent flows
Authors: Vašaacute;k F. , Kaštánek F. , Bowen B. D. , Chen C. Y. , Epstein N.
Published: March 2009

The deposition of fine silica and polystyrene spheres was measured for conditions of laminar and turbulent flow (960 ≤ Re ≤ 16040) in a rectangular channel using image analysis. The plate glass deposition surfaces were rendered positively charged by coating them with a cationic copolymer while, under the water chemistry conditions employed, both types of particles were negatively charged. It was found that, contrary to the results for laminar flow, the initial depositon rates in turbulent flow decreased with increasing Re, indicating that deposition was no longer mass‐transfer controlled and that particle attachment played an increasingly important role as Re was raised. Attachment was modelled as a rate process in series with mass transfer in which the attachment rate varies inversely as the square of the friction velocity. Under the conditions of the present experiments, no particle re‐entrainment was observed, so that the declining rate of particle accumulation on the wall recorded in each run could only be attributed to a declining deposition rate. Even where asymptotic accumulations were reached, particle coverages never exceeded 3.5%.
Permeate pressure build‐up in shellside‐fed hollow fiber pervaporation membranes
Authors: Feng Xianshe , Huang Robert Y. M.
Published: March 2009

Pervaporation of water, ethanol and isopropanol through polydimethylsiloxane hollow fiber membranes was studied, with emphasis on elucidating the significance of permeate pressure build‐up inside the fibers when the shell‐feed mode of operation was used. The differential form of the Hagen‐Poiseuille equation was used to describe the permeate pressure profile, and the theoretical predictions of permeate productivity were confirmed by experimental data. A parametric analysis showed that the dimensions of the hollow fiber (inside and outside diameters, and length) significantly affected the overall pervaporation performance of a hollow fiber membrane module, and the fiber dimensions must be optimized in order to achieve high productivity.
Kinetic study of fructose‐glucose isomerization in a recirculation reactor
Authors: Camacho‐Rubio F. , Jurado‐Alameda E. , González‐Tello P. , Luzón‐González G.
Published: March 2009

We have studied the equilibrium and kinetics of fructose‐to‐glucose isomerization using a commercial immobilized glucose isomerase, Sweetzyme T® (from NOVO), in a packed‐bed recirculation reactor which enabled us to eliminate the influence of external‐mass transfer and which could function as a differential reactor when a sufficient flow rate was used. The results obtained have also been corrected with regard to the influence of internal transport in the immobilized enzyme particles.

Isomerization kinetics is a pseudo first‐order reversible reaction in the ranges studied: 303–333 K, pH 7.5 and 0.5 to 2.0 mol/L hexose concentrations. We compare our results with those found in the literature, and propose equations for the influence of temperature on the equilibrium and on the kinetic constants.
Diffusion limitation effects in the washcoat of a catalytic monolith reactor
Authors: Leung D. , Hayes R. E. , Kolaczkowski S. T.
Published: March 2009

In monolith reactors with catalytic washcoat, intraphase diffusion effects have often been underestimated. This paper presents numerical simulations of diffusion/reaction in the washcoat of a catalytic monolith reactor. The problem is solved in two dimensions for the washcoat geometry obtained in a 1‐mm square monolith channel, as revealed by scanning electron microscopy. For the oxidation of carbon monoxide, propane or methane diffusion limitation can be substantial at typical operating conditions. The two‐dimensional solution is compared to a one‐dimensional approximation. The latter approximation for the real washcoat is valid provided that the characteristic length is selected carefully. This value is different from the characteristic length of the two‐dimensional washcoat. The characteristic length of a two‐dimensional geometry is not sufficient in itself to describe all washcoat geometries. It is predicted that the application of a diffusion barrier of 4–6 μm of inactive washcoat may be used to lower the rate of reaction in the inlet region of the monolith reactor.
The influence of temperature and the concentration of MNSO4 on the simultaneous absorption and reaction of mixtures of SO2 and O2
Authors: Bravo V. R. , Camacho F. R. , Moya M. V.
Published: March 2009

We have studied the simultaneous absorption of gaseous mixtures of SO2 and O2 in solutions of MnSO4 up to 0.75 mol/L and at temperatures between 10 and 40°C. The reactor used was operated continuously for the gas phase and batchwise for the liquid. The liquid phase was saturated in SO2 at the first sampling after one hour. The absorption of O2 was the controlling step in the process, with reaction order of 0 and 1 for SO2 and O2, respectively, and a fast reaction regime for MnSO4 at concentrations of more than 0.025 mol/L.

As far as manganese is concerned, our results show that the reaction order varies according to its concentration and we have obtained an equation which relates the kinetic constant to temperature and the concentration of the catalyst.
Using ultrafiltration to analyze the molar mass distribution of kraft lignin at ph 13
Authors: Li J. , O'Hagan T. , MacLeod J. M.
Published: March 2009

We used deliberately calibrated ultrafiltration membranes to analyze the molar mass distribution (MMD) of kraft lignin in alkaline solution. The membranes were first tested with probe macromolecules to obtain sieving curves at the same conditions as the lignin analysis. Using a restricted transport model, we calculated the average effective membrane pore sizes. The results were different from the nominal cut‐off values. The MMD of a lignin sample at pH 13 was analyzed by separating the lignin solution into five fractions; the MMD using the calibrated cut‐off values was confirmed by gel permeation chromatography.
Sequential identification: A procedure for insuring internal consistency of steady‐state gains for multivariable systems
Authors: Shen Shih‐Haur , Yu Cheng‐Ching
Published: March 2009

The importance of obtaining consistent steady‐state gains increases as the expected level of performance increases. A new consistency relationship is derived to ensure that the steady‐state gains identified are physically correct. In addition to the consistency relationship, an identification procedure is also proposed to achieve the internal consistency. Unlike the typical identification‐reconciliation procedure, the proposed approach meets the internal consisency via the identification procedure (no reconciliation is necessary). Two nonlinear distillation examples, a 2 × 2 system and a 3 × 3 system, are used to illustrate the effectiveness of the proposed approach. The results show that physically correct description of the columns can be achieved using the proposed approach for a range of changes in the manipulated variables.
Microfiltration of apple juice using inorganic membranes: Process optimization and juice stability
Authors: Alvarez V. , Andres L. J. , Riera F. A. , Alvarez R.
Published: March 2009

Crossflow membrane microfiltration of low‐pectine raw apple juice was studied using inorganic membranes (TECH SEP Carbosep®, Lyon, France) having a nominal pore size of 0.2 μm. Permeate flux was measured at different operation conditions (trans‐membrane pressure between 100 and 500 kPa, feed velocities between 1 and 6 m/s, and temperatures of 293, 298 and 323 K). Some concentration experiments were made in order to study the rejection of pectins and polyphenols at different VCR (volume concentration ratio) values. Final stabilization tests were carried out to analyze the long‐term clarified juice behaviour.
On the reported attempts to radically improve the performance of the steam methane reforming reactor
Authors: Adris A. M. , Pruden B. B. , Lim C. J. , Grace J. R.
Published: March 2009

Steam reforming of light hydrocarbons is a key step for producing hydrogen and syngas for important processes in the petroleum and petrochemical industries. Since the establishment of the SMR process in 1930, research and development have led to improved catalyst performance and improved reactor tube materials. Since about 1970, new reactor configurations have been considered. The authors critically review recent attempts to radically improve the SMR reactor performance, analyze the areas of improvement and the suitability of proposed configurations for different reforming applications.
Influence du dodecyl sulfate de sodium sur la tension interfaciale du système biphasé butanol‐eau
Authors: Mollet Céline , Touhami Youssef , Hornof Vladimir
Published: March 2009

Le présent article a pour objet l'étude expérimentale de la tension interfaciale entre les deux phases formées par le système partiellement miscible composé du butanol‐1 et de l'eau. En utilisant la méthode du volume de la goutte, l'effet d'un agent tensioactif, le dodécyl sulfate de sodium, sur la tension interfaciale fut étudié. On a trouvé que l'addition de l'agent tensioactif à la phase riche en butanol (la phase de goutte) cause une baisse légère de la tension dont la magnitude est influencée par le temps de contact. Lorsque l'agent tensioactif est mis dans la phase aqueuse (la phase externe), la baisse de la tension est plus importante et égale à celle observée quand ce dernier est présent dans les deux phases. On peut conclure que l'orientation des phases dans l'appareil de mesure produit un effet important sur la tension interfaciale apparente mesurée.
Absorption of sulfur dioxide in aqueous dispersions of dimethyl aniline
Authors: Bhattacharya Suman , Dutta Binay K. , Shyamal Manoranjan , Basu Ranjan K.
Published: March 2009

Absorption of sulfur dioxide in aqueous dispersions of dimethyl aniline has been carried out in a laboratory stirred cell with a flat gas—liquid interface. The effects of liquid loading, gas concentrations and other parameters have been studied. The absorption rate is linear in gas concentration, and increases with increasing dispersed phase concentration. Substantial enhancement of absorption compared to that in water occurs. Emulsification of the liquid by addition of a surfactant does not increase the absorption rate. The rate of desorption of sulfur dioxide from a loaded solution at 60°C remains essentially constant. A theoretical model for absorption has been developed assuming each droplet in the film to be enclosed by a spherical shell of the aqueous phase through which the solute diffuses at steady state. Comparison of the calculated enhancement factors with the experimental values confirms the validity of the model.
Dynamic modelling and performance optimization of an extractive fermentation
Authors: Arnold Sabine G. , McLellan P. James , Daugulis Andrew J.
Published: March 2009

A dynamic model for a continuous extractive fermentation process is proposed. Using this model and the Iterative Dynamic Programming algorithm, optimal operating profiles are identified for process start‐up from conventional fermentation operation. Under the optimal operating profile, profit during the transient operation accumulates at a rate approaching that of steady state operation. A sensitivity analysis investigating the effect of economic variations on the overall profit function shows that optimization of manipulated variable profiles primarily reduces the impact of substrate cost, so that the profit function approaches a linear function of the product value.
Scalar mixing in turbulent concentric round jets
Authors: Grandmaison E. W. , Becker H. A. , Zettler N. L.
Published: March 2009

The scalar mixing field of a free, turbulent concentric round jet has been examined using marker nephelometry. The flow conditions included velocity ratios between the centre and annular jet of 0.188, 0.519 and 0.911. The correlation function between the concentration fluctuations in the two jet streams increased from –1.0 near the nozzle to + 1.0 further downstream indicating a tendency to complete mixing between the jets. The initial mixing behaviour between the jets was better for the lower velocity ratio between the jets (Ui/Uo = 0.188) although further downstream there was better transverse mixing between the jets with the higher velocity ratio (Ui/Uo = 0.911).
Inertia Effects on the Flow of Bingham Plastics Through Sudden Contractions in a Pipe
Authors: Vradis George C. , Hammad Khaled J.
Published: March 2009

The present numerical study concentrates on the effects of moderate and high Reynolds numbers on the laminar flow of a non‐Newtonian rigid viscoplastic (Bingham) fluid through a sudden contraction in a pipe. The flow is assumed to be steady, incompressible, and isothermal. Results are presented for a wide range of the governing Reynolds and yield numbers and the significant effects of these two parameters both on the integral and local kinematic properties of the flow field are established. Low yield numbers result in the disappearance of the recirculating flow region at the corner replacing it with a region of very low rates of deformation. The evolution of the centerline velocity in the vicinity of the contraction plane is shown to be independent of the yield number and dependent on the Reynolds number, while the concavities in the streamwise velocity profiles appearing at high Reynolds numbers are independent of the yield number. The pressure losses through the contraction increase with yield number with the effect being more pronounced at lower Reynolds numbers.
The Effect Of the dust collection system on the flowpattern and separation efficiency of a gas cyclone
Authors: Hoffmann A. C. , Groot M. De , Hospers A.
Published: March 2009

The influence of the presence of a hopper section, consisting of a dust hopper and swirl attenuator, under gas–solid cyclones has been investigated by numerical simulation. Inclusion of this configuration in the simulations was found to have a significant influence on both flowpattern and separation efficiency. Moreover, predicted axial gas velocity profiles agreed better with independent experimental measurements. The cyclone separation was predicted to be better with the hopper section included than without, a physical reason is proposed. Comparison of simulated grade‐efficiency curves with experimental data indicates improved agreement, in some cases substantially so.
Solubility of N2O and CO2 in n‐Dodecane
Authors: Henni Amr , Jaffer Shaffiq , Mather Alan E.
Published: March 2009

The solubility of CO2 and N2O in a physical solvent, n‐dodecane [C.A. Registry N° 124–18–5], has been measured at 40, 80 and 120°C at pressures up to 9.6 MPa. The experimental results were correlated by the Peng‐Robinson (1976) equation of state, and the interaction parameters, the Henry's constants and the N2O analogy parameters were obtained.
Pulse experiments over catalyst beds: A window of measurable reaction rate coefficients
Authors: Huinink J. P. , Hoebink J. H. B. J. , Marin G. B.
Published: March 2009

The elimination of concentration profiles in porous catalyst pellets is not straightforward for transient kinetic experiments since profiles may arise from limited diffusion rates, but also from accumulation in the pellets. For TAP pulse experiments, dominated by Knudsen diffusion on the reactor scale, intrapellet diffusion is typically instantaneous for industrial catalysts. The Knudsen diffusivity for beds of porous pellets can be calculated from its value for non‐porous pellets by accounting for the intrapellet porosity. The window of measurable rate coefficients is governed by a Damköhler number of the first type. A criterion is derived for experimental conditions, that allow intrinsic kinetic measurements with porous catalysts. The size of the admitted pulse should be sufficiently large to avoid pulse depletion by adsorption.
Influence of various metal oxides in the bistability observed in the oxidative dehydrogenation of 2 — Propanol over copper catalysts
Authors: Gil A. , Ruiz P. , Delmon B.
Published: March 2009

This article presents new results concerning a bistability phenomenon observed recently in the oxidative dehydrogenation of 2 ‐ propanol over copper catalysts. In this system, an activity hysteresis loop is observed when the partial oxygen pressure is varied. This bistability has been explained by the oxidation of metallic copper when the partial oxygen pressure increases and copper oxide reduction when the partial oxygen pressure decreases. In the experiments reported here, an external second phase (α‐Sb2O4, SnO2, Cr2O3, CeO2, Co3O4, MoO3, PbO2, NiO, Bi2O3 and MnO2) has been mixed with the copper catalysts. This modifies the hysteresis loop. The possible role played by the oxygen spillover at low temperature (150°C) on this modification is discussed.
Synthesis gas production from natural gas in a fixed bed reactor with reversed flow
Authors: De Groote A. M. , Froment G. F. , Kobylinski Th.
Published: March 2009

The feasibility of producing synthesis gas by partial oxidation of natural gas on a Ni‐catalyst in a fixed bed reactor with reversed flow was investigated by means of simulation. A one dimensional reactor model of the non‐steady state heterogeneous type, accounting for internal diffusional limitations, was applied. A double temperature peak is observed just after flow reversal, influencing the selectivities at the exit through enhanced steam reforming reactions. The second peak gradually decreases in importance with time during the semi‐cycle. The influence of several operating conditions on the reactor performance was studied. Most of the coke deposited in a semi‐cycle can be removed after flow reversal. This observation opens new perspectives for the reversed flow operation.
Annular wall layer thickness in circulating fluidized bed risers
Authors: Bi H. T. , Zhou J. , Qin S.Z. , Grace J. R.
Published: March 2009

The thickness of downward‐flowing annular wall layers in circulating fluidized bed risers has been determined in the literature based on measured radial profiles of both local particle velocity and solids flux. The thickness of the wall layer is shown to be larger based on solids flux profiles than when based on particle velocity profiles, because fluctuations in local instantaneous particle velocity are correlated with fluctuations in local solids concentration. A new correlation is developed to predict the time‐average thickness of the downflowing particle streamer layer based on solids flux measurements as a function of the cross‐sectional average voidage. It successfully accounts for the variation of the wall layer thickness with axial location and solids circulation rate.
Contrôle hydrodynamique de l'evaporation d'un film liquide ruisselant sur une paroi isotherme à symétrie de révolution dans un courant d'air humide
Authors: Kaoua M. , Cherif A. Ali , Daïf A. , Daguenet M.
Published: March 2009

Les auteurs étudient numériquement, à l'aide d'une méthode aux différences finies associée à l'algorithme de Thomas, l'évaporation, dans un courant d'air humide, d'un film mince d'eau s'écoulant sur la paroi, supposée isotherme, de corps à symétrie de révolution, la variabilité des propriétés physiques des fluides étant prise en compte et le régime supposé laminaire et permanent. L'influence des principaux paramètres du système sur l'évaporation est précisée, notamment celle du profil de la paroi du corps axisymétrique. Les auteurs montrent que, pour des conditions de calcul fixées, il est possible de trouver un ellipsoïde de révolution aplati offrant une paroi uniformément accessible sur une grande étendue entre le pǒle et l'équateur.
Supercritical carbon dioxide extraction of spearmint oil from mint‐plant leaves
Authors: Özer Eli̇f Ö , İin Sevan Plat , Akman Uǧur , Hortaçsu Öner
Published: March 2009

Spearmint oil (essential oil of Mentha spicata) was extracted from Turkish mint‐plant leaves using supercritical CO2 in a basket‐type extractor. Effects of temperature, pressure, extraction time, amount of CO2, and entrainer (ethanol) concentration on composition of essential‐oil extracts and oil yield, relative to hydro‐distillation, were investigated. Relative yields were as high as 80%. Monoterpenes fraction in extracts was inversely correlated with relative oil yields. Monoterpenes were preferentially extracted by CO2 due to their high vapor pressure, low molar mass and low polarity. Supercritical extraction presented advantages over the conventional hydro‐distillation by yielding extracts lower in monoterpenes fraction and by enabling high yields at temperatures safe for the heat‐sensitive essential oil.
Prediction of the azeotropic behavior of binary mixtures from gas—Liquid P‐T‐x critical data with cubic equations of state
Authors: García‐Sánchez Fernando , Hernández‐Garduza Otilio , García‐Flores Blanca E. , Eliosa‐Jiménez Gaudencio
Published: March 2009

A computational procedure is described to predict homogeneous azeotropic loci of binary mixtures with cubic equations of state and gas—liquid P‐T‐x critical information. The performance of the method is demonstrated on three binary systems exhibiting either negative or positive azeotropic behavior which persists up to the critical region. The method of Heidemann and Khalil was used for correlating the critical data while that of Wang and Whiting was used to predict the azeotropic lines together with a stability test applied on each estimated point. Good agreement between calculated and measured azeotropic data was obtained for the systems studied.
Kinetics of the peracetic acid decomposition: Part II: pH effect and alkaline hydrolysis
Authors: Yuan Z. , Ni Y. , Van Heiningen A. R. P.
Published: March 2009

The effect of pH on the decomposition of peracetic acid in an aqueous solution was studied. It was found that three potential reactions, namely i) the spontaneous decomposition, ii) the hydrolysis and iii) the transition metal catalysed decomposition, are responsible for the consumption of peracetic acid. The spontaneous decomposition reaches its maximum at pH 8.2, while both the hydrolysis and metal ion catalysed decomposition increase as the pH increases. At pH 10.5 and higher, the hydrolysis becomes dominant when the metal ion catalysed decomposition is minimized by the addition of DTMPA. The kinetics of the peracetic acid hydrolysis was developed, which can very well predict the development of peracetic acid and hydrogen peroxide during the decomposition reaction.
Gas—liquid mass transfer in pulp suspension mixing operations
Authors: Bennington C. P. J. , Owusu G. , Francis D. W.
Published: March 2009

The rate of mass transfer from the gas to water phases was measured in a commercial, high‐shear, laboratory mixer under conditions typical of medium‐consistency bleaching. The gas—liquid volumetric mass transfer coefficient, kLa, was measured using the cobalt‐catalyzed sulfite oxidation technique. Suspensions of fully‐bleached kraft pulp and synthetic nylon fibres were used, with mass transfer rates measured over a range of suspension compositions and mixer operating conditions. In the presence of pulp fibre, mass transfer rates were significantly reduced over the comparable water cases. The same dramatic decrease in mass transfer was not observed for the nylon suspensions, although kLa did decrease with increasing suspension concentration. Comparison of this data with that obtained from ozone bleaching experiments confirmed that at medium‐consistency gas—liquid mass transfer controls ozone bleaching.
Removal of contaminants from recirculated white water by ultrafiltration and/or biological treatment
Authors: Elefsiniotis P. , Hall E. R. , Johnson R. M.
Published: March 2009

This study investigated the potential of ultrafiltration technology and/or biological treatment to remove contaminants such as total dissolved solids (TDS), chemical oxygen demand (COD), total organic carbon (TOC), and resin and fatty acids (RFAs) from recirculated white water. Batch ultrafiltration experiments indicated that TDS, soluble COD, and TOC removal efficiencies were affected by membrane molecular weight (molar mass) cut‐off, but were independent of the operating temperature, in the 20 to 60°C range. Except for fatty acids, where average removals exceeded 90%, the separation efficiency of the process for all other parameters (TDS, soluble COD, TOC, and resin acids) was moderate, ranging from 10 to 41%. Biological treatment using a sequencing batch reactor (SBR) unit was very effective in removing RFAs, TOC, total and soluble COD. Furthermore, ultrafiltration of the biologically treated process water resulted in significant additional TDS, soluble COD, and TOC removal.
Phenolic compounds from vacuum pyrolysis of wood wastes
Authors: Pakdel H. , Roy C. , Amen‐Chen C. , Roy C.
Published: March 2009

Various softwood and hardwood bark residues, primary sludges and softwood sawdust residues were processed by vacuum pyrolysis in a laboratory scale batch reactor. The pyrolysis oil, water, charcoal, and gas were recovered and analyzed. The pyrolysis oils were analyzed in details for their content in phenolic compounds after derivatization to their acetyl derivatives. The influence of temperature, heating rate, feedstock bed thickness, particle size and feedstock water pretreatment on the yield of phenols was investigated. The highest yield of phenols was obtained when hardwood bark was soaked in water for 48 hours and pyrolyzed at a temperature of 450°C and a heating rate of 10°C/min. Pyrolysis performance was evaluated in terms of total phenolic yield and composition.
Micro‐ and macroscopic aspects of polymer bonded paper
Authors: Jonasson R. G. , Henry D.
Published: March 2009

The bonding of polymers was examined using analogues of commercial adhesive which were selected so that they could be readily detected by surface microanalytical techniques including scanning electron microscopy, X‐ray photoelectron spectroscopy and secondary ion mass spectrometry. When reagents were added to the pulp prior to handsheet preparation, epoxides but not isocyanates, were found to adhere to cellulose and wood fibers by polymerizing with themselves. That is, epoxides polymerized to form gels, which then adhered to the fibers. To test this hypothesis, handsheets were treated subsequently with solutions of pre‐formed polymers. In the case of both polyvinylchloride and cellulose acetate, the tensile breaking length and burst index of treated handsheets increased significantly compared with the controls. No surface analytical, or bulk property data was found in this study to demonstrate covalent bonding of adhesives to cellulose or wood fibers. This means that adhesives should be readily extracted from recycled paper with appropriate organic solvents.1
Kinetics of the heterogeneous catalytic decomposition of methane
Authors: Kristyan Sandor
Published: March 2009

Experiments have clearly demonstrated that dissociation of CH4 on (supported) metal catalyst (e.g. Pt, Ru, Rh, Ir, Pd) occurs to give hydrogen, a small amount of ethane and surface carbonaceous species. For this catalytic decomposition of methane and its conversion into higher hydrocarbons (especially to ethane and surface carbon) model has been developed to investigate the kinetics. Rate constants of the elementary steps have been estimated. The problem with experimental data (especially for the surface species CHm‐s) is also treated for the sake of future improvement in the kinetics studies. A comparison with catalytic hydrogenolysis of ethane kinetics is also outlined.
Pressure drops in gas—liquid flow in a 15 cm reciprocating platecolumn
Authors: Baird M. H. I. , Rao N. V. Rama
Published: March 2009

Time‐averaged pressure drops have been measured in a 15 cm internal diameter reciprocating plate column, using the water/air system under conditions of cocurrent, countercurrent and single phase (water) flow. The reciprocation frequency was varied from 1 to 4 Hz, while the stroke (peak to trough amplitude) was set at 2.54 cm. Two types of perforated plate were used, having perforation diameters 14.3 and 6.35 mm.

Under single phase flow conditions, the pressure drops were in agreement with an earlier model due to Noh and Baird (1984). Under cocurrent conditions the gas flow had the effect of increasing the pressure drop, particularly at low reciprocation rates; this was interpreted in terms of enhanced circulation velocities in the liquid phase. In countercurrent flow the pressure drop was also affected by bubbles clustering at the plates.
Liquid circulation and mixing in an inclined bubble column
Authors: Lu George Z. , Bittorf Kevin , Thompson Brad G. , Gray Murray R.
Published: March 2009

Gas and liquid velocities were measured in an inclined rectangular column, at inclinations in the range 0−45° and superficial gas velocities of 0.002 to 0.12 cm/s. Liquid circulation was also characterized by measuring the time to mix a pulse of salt solution in the column. Inclining the column by up to 10° from the vertical induced a drastic change in behavior, from a bubble column with evenly distributed gas bubbles to a segregated system with rapid liquid circulation pumped by rising gas bubbles. The liquid velocities in the inclined column ranged from 10 to 50 times the superficial gas velocity. Further inclination of the column in the range of 10−45° had little effect on liquid velocity or mixing time. A compartmental model for the recirculating liquid flow matched the observed mixing times, but predicted oscillations in tracer concentration which were not detected in experiments.