bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of anhydrous 1,4‐dioxane from ethylene oxide in the presence of amberlyst 15
Authors: Yamanis John , Garland Ronald W.
Published: March 2009

The fast and exothermic reaction of ethylene oxide with the sulfonic acid groups of Amberlyst 15 (H+), suspended in an inert solvent, leads to the formation of polymeric ester species whose length aproaches a limiting value.

The ester chains decompose to form cyclic ethers and this decomposition can be made selective for 1,4‐dioxane in a two‐step process by first esterifying the resin and then depolymerizing the esters. The resin can be used repeatedly with substantial capacity loss, but this loss can be removed by regeneration.

1,4‐Dioxnne formatios from the esters was fousd to be described by the phenomenological model.

with an apparent activation energy of 25.8 kcal/mol.
Surface and interfacial tension measurement by drainage methods
Authors: Baird M. H. I. , Nirdosh I.
Published: March 2009

The drainage of a liquid from a narrow vertical tube which is open at the bottom but closed at the top is prevented when the capillary forces exceed the gravitational forces acting on the liquid meniscus. The critical tube diameter for prevention of drainage is a function of surface or interfacial tension, and this effect forms the basis of three techniques for measuring surface or interfacial tension. Results are given for various liquid/air and liquid/liquid systems in (a) a tapered tube, (b) a rotating uniform tube and (c) a tilted uniform tube. Methods (a) and (b) appear capable of measuring surface or interfacial tension within about ± 1%.
A modified general dominant eigenvalue method for convergence acceleration of cyclic systems
Authors: Soliman M. A.
Published: March 2009

In this paper, a new derivation is presented for the General Dominant Eigenvalue Method (GDEM) for Convergence Acceleration of cyclic systems described by a set of non‐linear algebraic equations. Through the derivation a modification which improves the convergence of the GDEM is suggested. Two examples are used to show the kind of improvement, one might expect using the modified version.
Mechanical degradation of semi‐dilute polymer solutions in laminar flows
Authors: Ghoniem S. , Chauveteau G. , Moan M. , Wolff C.
Published: March 2009

Mechanical degradation of a semi‐dilute solution of non‐hydrolyzed polyacrylamide was studied under laminar flow conditions through fine capillary systems. Using a multi‐pass device and capillary tubes of the same diameter and of various lengths we have shown that mechanical degradation (i) occurs at a critical value of the wall shear rate, chosen as a reference deformation rate, which is slightly higher than that of the appearance of high pressure losses in the entrance region of the capillary tube; (ii) is independent of the capillary tube length; (iii) increases with the number of passes N up to a maximum value for a limiting number of passes Nlim which is a decreasing function of deformation rates but does not depend on capillary length.

The amount of degradation is expressed in terms of loss of viscous dissipation in shear and transient elongational flow. This last point is determined by studying the total end pressure loss through the capillary tube as a function of the pass number. The high pressure loss is related to viscous dissipation on macromolecules stretched by rapid converging flow. A comparison between a fresh and a fully degraded solution indicates that the degradation affects shear viscosity much less than viscous dissipation in rapid converging flow which is related to the properties of extended macromolecules. Both experimental results and theoretical interpretation suggest that, in our capillary system, the mechanical degradation occurs in the entrance region of the capillary where macromolecules are stretched and consequently submitted to extensional forces which can overcome the C–C bonds strength.
Theoretical studies on the gravity drainage of heavy oil during in‐situ steam heating
Authors: Butler R. M. , Mcnab G. S. , Lo H. Y.
Published: March 2009

One concept for the in‐situ production of oil from the tar sands involves the continuous injection of steam into a growing steam‐saturated volume or steam chamber. Steam flow to the boundary of the chamber, condenses and gives up its heat to the surrounding oil sands. The condensate and heated oil flow by gravity to a production well located at the bottom of a chamber and are removed continuously. The well may consist of a horizontal slotted pipe. This paper describes the theory of operation of such a process and an equation is derived which predicts the rate of drainage.
Local compositions and local surface area fractions: A theoretical discussion
Authors: Panayiotou C. , Vera J. H.
Published: March 2009

The basic constraint for any valid expression for local composition, derived by McDermott and Ashton, is shown to be equivalent to the conservation equation used in Flemr's analysis. A similar constraint for local surface fractions is derived. The applicability of quasi‐chemical expressions for local composition or local surface area fractions is extended to different existing (random) models of solutions. Chao's and Kehiaian's treatments appear as special cases. The statistical thermodynamic derivation of UNIQUAC is discussed in the framework of the generalized treatment. A method for solving the quasi‐chemical equations for quaternary systems is described.
Batch cultivation of kluyveromyces fragilis in cheese whey
Authors: Beausejour Denis , Leduy Anh , Ramalho Rubens S.
Published: March 2009

Kluyveromyces fragilis was cultivated batchwise in an open pond rectangular bioreactor at 30°C, 2vvm of aeration, under non‐sterile conditions and uncontrolled pH. The culture medium contained 7% cheese whey powder, 0.25% KH2PO4, 0.5% (NH4)2SO4 and was adjusted to an initial pH of 4.0 with phosphoric acid. The lactose was almost completely consumed after 16 h and COD reduction attained 80% after 64 h. The maximum suspended solids concentration obtained was 11.7 g/L. The cheese whey which had initially low protein and high lactose contents was converted by this system into a high protein and low lactose carbohydrate product.
Mathematical modelling of rotary cement kilns by the zone method
Authors: Guruz H. K. , Bac N.
Published: March 2009

A steady state mathematical model of rotary cement kilns based on the fundamental principles of the physical and chemical processes within the kiln was developed. The zone method of analysis was utilized together with the Monte Carlo method to simulate the radiative interchange within the kiln. Steady state energy balances including the chemical reaction terms for each zone were solved simultaneously to give temperature distributions in gas and solid charge, and composition distribution in solid charge. Predictions of the mathematical model were compared with dry process and wet process rotary cement kiln data.
Penetration model of gas absorption into slurry accompanied by an instantaneous irreversible chemical reaction
Authors: Uchida S. , Miyachi M. , Ariga O.
Published: March 2009

Recently, the problem of absorption of gases into nonhomogeneous solvents has drawn more attention than ever as it found in various fields such as flue gas scrubbing, hydroprocessing, coal conversion and medicine. Since the first treatment of this problem by Ramachandran and Sharma(1), several models based on the film concept have been proposed(2‐7). There is, however, no penetration theory for the evaluation of the rate of the absorption of a gas into a slurry containing suspended solid particles. In this paper, a penetration model is presented for the absorption of gas A into a slurry containing solid B with an instantaneous irreversible chemical reaction.
Void fraction and pressure drop in two phase stratified flow
Authors: Kadambi V.
Published: March 2009

A procedure for computing the void‐fraction and pressure drop in two‐phase stratified flow over the whole range of flows from turbulent‐turbulent to laminar‐laminar, has been put forth. The results are in excellent agreement with those of previous investigators in flow situations where data are available. Simple curve fits of the theoretical results have been developed to compute the required quantities, as functions of the Lockhart ‐ Martinelli parameters.
Intraparticle effects in char combustion. III transient studies
Authors: Srinivas B. , Amundson Neal R.
Published: March 2009

Unsteady state mass and energy balance equations along with a probabilistic model to predict the surface area evolution, constitute the model developed to study the dynamics of single particle char combustion. The transients and the ignition‐extinction phenomenon are analyzed with the aid of the pseudo‐steady state structure of the problem. There exists a critical particle size, ambient temperature, ambient oxygen concentration and boundary layer thickness above which the particle ignites. There is an optimum particle size for which the burning time is a minimum. Experimentally observed extinction phenomenon of artificially ignited particles is predicted by the model. Also, it is found that the extinction radius decreases with increase in ambient O2 concentration, which is in qualitative agreement with the experimental results. The model is compared with the simple shrinking core model.
Finite element solution of low peclet number fluid flow in a round pipe with the cauchy boundary condition
Authors: Lee S. L. , Hwang G. J.
Published: March 2009

This paper presents a finite element solution to the problem of low Peclet number fluid flow in the thermal entrance region of a round pipe. The velocity is assumed to be laminar and fully developed throughout the pipe and the fluid temperature is kept uniform atX = —∞. The pipe wall is adiabatic at X ≤ 0 and cooled convectively at X ≥ 0.

The solutions include temperature distributions and Nusselt numbers for the parameters, Bi = 0.04, 0.4, 4, 20 and Pe = 1, 3, 5, 10, 20, 30, which are in excellent agreement with the existing analytic solution except in the region near the singular point Δ A temperature discrepancy in the analytic solution at this point is physically impossible. The finite element method overcomes this mathematical difficulty and shows a greater value in the Nusselt number due to a higher wall temperature at X ≥ 0.
Preparation of high porosity catalysts
Authors: Ternan M. , Packwood R. H. , Buchanan R. M. , Parsons B. I.
Published: March 2009

Porous alumina catalyst supports have been prepared with pore volumes exceeding 1.0 mL/g, with most pores having diameters of the order of 3 μm and with surface areas exceeding 150 m2/g. They were obtained from dilute alumina gels having large concentrations of acid and very large concentrations of fluid. Attempts were made to dry the gel without collapsing the pore structure between the alumina particles. The catalysts were characterized by gravimetrical BET surface area, mercury porosimetry, X‐ray diffraction and scanning electron microscopy. Catalyst supports having these geometric properties should eliminate mass transfer restrictions during hydrocracking of petroleum residua, heavy oils and bitumen derived from oil sand deposits.
The effect of chromium exchange level on the cracking and dehydrocyclization of n‐Heptane on CrHNaY zeolite catalysts. Kinetic and spectroscopic study
Authors: Agudo A.L. , Asensio A. , Corma A.
Published: March 2009

The influence of the degree of chromium ion exchange on Y zeolites on the catalytic activity for cracking and dehydrocyclization of n‐heptane has been studied at 673, 723 and 748 K and atmospheric pressure in a continuous flow system. The kinetic rate constants and activation energy in absence of decay for the cracking of n‐heptane on the catalysts have been obtained. Measurements of the surface acidity of these catalysts by I.R. spectroscopy of adsorbed pyridine and by titration with n‐butylamine has been carried out. A good correlation between the activity cracking of n‐heptane and the concentration of stronger acid sites (pKa ≤ + 1.5) on the chromium‐exchanged Y zeolites has been found.
Modeling of flow nonuniformities in fissured porous media
Authors: Lyczkowski Robert W.
Published: March 2009

A review is performed to trace how fissured porous media arise in nature. It is found that packed beds resemble fissured porous media. The range of multiple flow time‐scales inherent in such media becomes larger as the particle size range becomes broader, resulting in flow nonuniformities. The status of experimental measurements of voidage and flow nonuniformities is assessed. Some of the difficulties associated with modeling of the multiple flow time‐scales are discussed, and a tentative model is proposed.
Use of gold tracer in the study of atmospheric oxidation of sulfur dioxide
Authors: Rowe Richard D. , Mohtadi Matt F. , Havlena Jan J. , Exall Douglas I. , Benjamin Stephen F.
Published: March 2009

A technique using gold particles as a conserved tracer has been developed in an effort to determine experimentally the oxidation of sulfur dioxide in sour gas plant plumes. A helicopter was used for plume sampling at distances up to 4 km downwind of the stack. The concentration of sulfur dioxide gas in the plume sample was determined by the West‐Gaeke method. Neutron activation analysis was used to determine the concentration of gold particles in the plume sample. Since gold particles do not react chemically with plume gases, any decrease in their concentration along the plume path was due to turbulent dispersion. This parameter allowed an accurate estimation to be made of the decrease in the sulfur dioxide concentration within the plume sample that had occured due to physical dilution alone. Any further decrease in concentration could therefore be attributed to loss by chemical reaction. The experimental results indicated that, within the range studied, there is no measurable oxidation of sulfur dioxide in sour gas plant plumes.
Liquefaction of coal by SRC‐II process: Part I: A new kinetic model
Authors: Singh C. P. P. , Shah Y. T. , Carr N. L. , Prudich M. E.
Published: March 2009

The kinetic experiments were carried out in a continuous stirred tank reactor. Practically important ranges of SRC‐II reactor temperature (444–466°C), pressure (10.4–20.8 MPa), nominal slurry residence time (0.54–1.62 h), coal concentration in the feed slurry (25–35 wt%), and inorganic mineral matter concentration (4.75–13.43 wt%) were covered in a total of 43 experimental runs. In each of the experimental runs, the feed slurry was formulated by using vacuum tower bottoms from SRC‐II pilot plants using the same feed coal (Powhatan No. 5), to obtain feed compositions similar to those obtained in SRC‐II pilot‐plant recycle operation.

The kinetic model considers the overall conversion to be achieved in two stages. The first stage is the instantaneous dissolution of coal and in the rate controlled second stage all the reactive organic components in the liquid phase are initially assumed to react, each yielding components lighter than itself. The distribution of products in each reaction stage is considered to be independent of the operating conditions. The best rate controlled (second stage) reaction scheme and values of the unknown parameters are obtained by minimizing the overall difference (i.e. for all the components over all the runs) between the measured and model predicted mass fractions of the various components in the reactor. This analysis identifies the reaction of solvent refined coal (pyridine soluble organic matter boiling above 482°C) to be the only significant reaction in the second stage and its rate is determined to be‐rSRC= 1.567 × 105exp (‐79.16/RT) ·p0.28·XASH, kg/L h. Overall error in this analysis yielding the reaction scheme, rSRCand values of product distribution coefficients for both the reaction stages is less than 8% absolute i.e. ±4%.
Liquefaction of coal by SRC‐II process: Part II: Simulation of an SRC‐II recycle system
Authors: Singh C. P. P. , Shah Y. T. , Carr N. L.
Published: March 2009

The kinetic model, described in the preceeding paper, is used in this work to obtain a general simulation of an SRC‐II recycle system. The present simulation considers the reactor to be isothermal and fully backmixed, reactions in the preheater to have insignificant influence on yields, and separation of the products into various fractions to be ideal. The concept of degrees of freedom is used to evaluate the number of independent variables for the complete (recycle) system. The model is validated against data from three different pilot plants on Powhatan, Kentucky, and Ireland Mine coals. The effects of various variables on yield behavior and distribution of solids throughout the system are illustrated. Operational difficulties encountered in increasing the recycle ratio of bottoms, containing solids, above 0.75 is explained.
A Chemical equilibrium model for interfacial activity of crude oil in aqueous alkaline solution: The effects of pH, alkali and salt
Authors: Chan Mankin , Yen Teh Fu
Published: March 2009

A chemical equilibrium model is proposed to describe the effects of acid content, pH and sodium ion concentration on the interfacial activity of crude oil in aqueous alkaline solutions. The model is based on an equilibrium among the dissociation of acids in the crude, the dissociation of the sodium salt containing the active species and the dissociation of water. It is shown that once the pH of the interface reaches the pKa of the acids, the interfacial tension (IFT) drops steeply and that further addition of sodium ions increases the IFT by shifting the equilibrium to form undissociated soap.
Pressure drop, solids concentration and mean holding time in multistage fluidisation
Authors: Krishnaiah K. , Varma Y. B. G.
Published: March 2009

Correlations for the pressure drop, solids concentration and mean holding time of the solids in multistage fluidisation have been presented based on the experimental data of the present study and that available in literature covering a wide range in process variables.
Study of the catalytic effects of impregnated metals in the pyrolysis of peat
Authors: Roy Christian , Chornet Esteban
Published: March 2009

A case study is presented and thoroughly discussed to show that through rigorous application of statistical criteria it is possible to: (a) unambiguously identity the effect of each catalyst tested upon overall yields; (b) determine the extent of the effect on individual product yields and (c) classify the catalysts on a performance basis.

The study focuses on the pyrolysis of naturally occuring peat doped with small amounts of finely dispersed metals (K. Fe, Co and Ni) introduced by impregnation with their nitrate salts. The pyrolysis has been conducted on the air‐dry material under reduced pressure conditions at a heating rate of 10°C/min up to a temperature of 925°C.

The statistical analysis resulted in rejection of the initial underlying hypothesis which considered that the metallic additives will exert an influence on the overall peat tar yield and composition. Presence of important amounts of silica (as ash) might have been responsible for the lack of catalytic effects observed. The work stresses the usefulness of repetitive runs to determine the inherent experimental error when conducting catalyst screening on real substrates.
Forced convection heat transfer in low prandtl number turbulent flows: Influence of axial conduction
Authors: Lee Shong‐Leih
Published: March 2009

The effect of axial conduction was investigated for turbulent heat transfer in a round pipe with uniform wall temperature. Exact solutions were obtained by using the method of separation of variables for the two cases with and without the axial conduction term.

The solutions show that the effect of axial conduction is important at low Peclet numbers, say Pe < 100, but negligible in the thermally fully‐developed region. Also, the fully developed Nusselt numbers depend only on Reynolds number at low Peclet numbers and the interpolation formula is proposed:

which fits the calculated data well in the liquid metal range 0.001 < Pr < 0.022 for Pe < 100.
Entrainment by a concentric jet with particles in the secondary stream
Authors: Subramanian Viswanath , Ganesh Raman
Published: March 2009

In a two‐phase concentric jet the second phase, consisting of solids, influences the development of the jet and the effect of its presence needs to be assessed quantitatively. An experimental study of such a jet with particles in the secondary stream was therefore undertaken. It is seen that particles enhance the mixing.
Biotraitement aerobie, en reacteur completement agite, d'une eau residuaire de laiterie
Authors: Mayer R. C. , Rouleau D. , Royer G.
Published: March 2009

Synthetic residual waters from dairies have been subjected to a laboratory‐scale treatment study.

A thoroughly‐stirred continuous‐flow reactor involving no recirculation of the biomass has been used. The operation‐control two parameters have been (a) the mean residence time of the biomass and (b) the bioreactor temperature. The variables have been (i) the substrate removal expressed in terms of the chemical demand in oxygen (D.C.O.) and (ii) the biomass production expressed in terms of volatile suspended matters.

The Monod model has adequately described the system behavior. The kinetic constants k, kd. Y, K, have been determined at 5, 15 and 25°C. The values of the substrate maximum rate of assimilation per biomass unit (k) and of the specific rate of the biomass deterioration rate (kd) have characterized the constants according to the Arrhenius Law in the range covered. The values of the half‐rate constant Ks have been high at the above‐mentioned three temperatures in comparison with the conventional values. The maximum coefficient of the yield (Y) has varied little with the temperature.
The flash pyrolysis of aspen‐poplar wood
Authors: Scott D. S. , Piskorz J.
Published: March 2009

A continuous fluidized bed bench scale flash pyrolysis unit operating at atmospheric pressure and feed rates of about 15 g/h has been successfully designed and operated. A unique solids feeder capable of delivering constant low rates of biomass has also been developed. Extensive pyrolysis tests with hybrid aspen‐popular sawdust (105–250 μm) have been carried out to investigate the effects of temperature, particle size, pyrolysis atmosphere and wood pretreatment on yields of tar, organic liquids, gases and char. At optimum pyrolysis conditions high tar yields of up to 65% of the dry wood weight fed are possible at residence times of less than one second.
Recovery of residual bitumen from oil sand sludges
Authors: Denis C. E. St. , Kessick M. A.
Published: March 2009

Factorial experiments were conducted to examine the effects of dilution, caustic addition and lime addition on the recovery of residual bitumen by flotation from oil sands tailings sludges. Dilution was found to be the most significant variable, and it was established that close to 100% recovery of the substantial quantity of residual bitumen could be achieved by flotation, after diluting 1 volume of sludge with 2 volumes of water. These results indicate that physical and chemical changes in the sludges may have occurred, during the storage period, to place the residual bitumen in a more accessible form. Atomic absorption analysis and infra‐red data on the sludge fractions indicate that the changes could have resulted from the interaction between calcium ion, present in the system in low concentrations, and surface active materials responsible for stabilizing the bitumen dispersed in the tailings.
Interfacial tension and phase behaviour characteristics of petroleum sulfonate/lignosulfonate mixtures
Authors: Son J. E. , Neale Graham H. , Hornof Vladimir
Published: March 2009

The interfacial tension and phase behaviour characteristics of mixed‐surfactant formulations containing petroleum sulfonate and lignosulfonate were investigated. Low interfacial tensions between oil and aqueous surfactant solutions were found to be closely related to the occurrence of a third phase, and hence to the general phase behaviour of the surfactant system. Ultralow interfacial tensions (>0.01 mN/m), which are well known between oil and pure petroleum sulfonate solutions, could still be achieved when using mixtures of petroleum sulfonate containing lignosulfonate. It is considered that these findings will have important economic implications in the recovery of oil from partially depleted oil fields.
Prediction of pressure behind a rising bubble accelerating from rest
Authors: Nilmani Madhukar
Published: March 2009

Numerical predictions are presented for pressure change left behind by an air bubble accelerating from rest in water. The computations are made with an implicit finite difference procedure for an axisymmetric system. The magnitude of pressure predicted compares well with the results of potential theory given by previous workers1.
The transfer of potassium chloride from n‐butanol to water
Authors: Sagert Norman H. , Lucy Charles A.
Published: March 2009

A rotating diffusion cell was used to study the transfer of potassium chloride from water to n‐butanol to water under conditions of known interfacial area and hydrodynamics. Experiments were conducted at 25°C using 1.0, 2.0, 3.0 and 4.0 mol/dm3 KCl in the first aqueous phase. The system displayed no measurable interfacial resistance to mass transfer. This is understandable since the primary solvation spheres of both potassium and chloride ions are composed almost exclusively of water molecules, so no solvation needs to occur when the ions cross the interface. Since this result is consistent with earlier studies of the same system by a different technique, confidence in the validity of the rotating diffusion cell technique is increased.

On a employé une cellule de diffusion rotative pour étudier le transfert de chlorure de potassium de l'eau au n‐butane, puis à l'eau, dans des conditions connues de surface interfaciale et d'hydrodynamique. On a fait ces expériences à 25°C, en employant 1.0, 2.0, 3.0 et 4.0 mol./dm3 de KCl dans la première phase aqueuse. Le système n'a présenté aucune résistance interfaciale mesurable au transfert de masse; ce fait est compréhensible, vu que les sphères de solvatation primaire des ions potassium et chlorure se composent presqu'exclusivement de molécules d'eau et qu'il n'est pas nécessaire qu'il se produise de solvatation lorsque les ions traversent l'interface. Etant donné que ce résultat concorde avec les résultats d'études antérieures du měme système par une méthode différente, il y a lieu d'avoir plus confiance en la validité de la méthode basée sur la cellule de diffusion rotative.
Stability of jets in liquid‐liquid systems
Authors: Kitamura Yoshiro , Mishima Hiroyuki , Takahashi Teruo
Published: March 2009

Experiments were carried out to study the stability of jets in immiscible liquid systems under conditions where the jet velocity relative to continuous phase was zero. The laminar breakup lengths and the diameter of drops formed from laminar jets are in good agreement with the stability analysis for stationary column while breakup data for jets injected into quiescent liquids disagree with it. An approximate solution for theoretical drop size is presented. The experiment also showed that the hydrodynamic resistance of continuous phase increases the growth rate of disturbances but does not affect the wave length.
Operating characteristics and energy distribution in a nitrogen transferred arc plasma
Authors: Tsantrizos P. , Gauvin W. H.
Published: March 2009

The electrical characteristics of a nitrogen transferred arc plasma were measured in a closed chamber, which simulated a plasma furnace. The total arc voltage depended strongly on the arc length and much less on current and plasma gas volumetric flow rate, with a voltage gradient of about 12 V/cm. The various mechanisms accounting for the transfer of the energy in the arc to the system were identified and measured. The two major components of the energy distribution were by electron transfer to the anode (whether water‐cooled solid copper or molten metal) and by radiation from the plasma column.

The significance of these measurements for the design and optimization of plasma furnaces is discussed.
Liquefaction of coal by SRC‐II process: Part IV: Steady‐state thermal behavior of the reactor
Authors: Singh Chandra P. P. , Carr Norman L.
Published: March 2009

An axial dispersion thermal model of an SRC‐II reactor is developed. The model is validated by simulation of steady‐state temperature profiles in the Fort Lewis (Tacoma, Washington) pilot‐plant SRC‐II reactor. The simulation shows that normal operations of the SRC‐II reactors are thermally unstable. Changes in the process conditions can be utilized to achieve thermal stability for the reactor at normal SRC‐II operating temperatures, i.e., reactor outlet temperature of less than 465°C and average reactor temperature of about 455°C. However, thermal stability of the reactor would always result in reduction in the rate of reaction. Regions of unstable steady‐state reactor temperature over large ranges of ash concentrations in the reactor and reactor feed temperatures are also illustrated.
Hydrolyse enzymatique du lactose dans un réacteur type réservoir agité
Authors: Ma Hung , Monsan P. , Mayer R. , Rouleau D.
Published: March 2009

L'étude cinétique de l'hydrolyse enzymatique du lactose a été réalisée dans un réacteur agité de type réservoir en écoulement continu, dans des conditions isothermes pour des températures comprises entre 30° et 50°C pour un pH égal à 4.5. L'utilisation d'un panier contenant l'enzyme immobilisée, permet de réduire considérablement les résistances de transfert externe. L'enzyme utilisée provenant d'une souche d'Aspergillus Niger a été immobilisée sur des billes de silice. Les caractéristiques de mixtion parfaite du réacteur ont été confirmées par une étude hydrodynamique pour les mémes conditions opératoires. Une analyse statistique a été effectuée afin de différencier les modèles possibles et celui qui s'ajuste le mieux aux données expérimentales correspond au modèle de Michaelis‐Menten avec inhibition compétitive par le produit, le galactose:
The stability of a steam‐water front in a porous medium
Authors: De La Cruz V. , Spanos T. J. T. , Sharma R. C.
Published: March 2009

We present a first order stability analysis of a steam‐water front moving through a porous medium. The interplay between gravity, mobility and phase change are investigated. Several new phasical effects are observed in this dynamic study (e.g. oscillatory solutions, multiple solutions, etc.) and a number of specific limiting solutions are also considered.
Carbon number distribution of fischer — Tropsch CO‐hydrogenation products from precipitated iron catalysts
Authors: Egiebor N. O. , Cooper W. C. , Wojciechowski B. W.
Published: March 2009

It is shown that in a series of precipitated iron catalysts, some show a break in the Anderson‐Schulz‐Flory (ASF) plot of the distribution of linear products and others do not. It is also shown that the above break is due solely to the change in slope of the linear paraffins and that no such break occurs in the distributions of α or β‐olefins.

Our conclusion is that the paraffins and olefins are all primary products and that each has a characteristic rate of termination, but all have a common rate of propagation. A growth scheme which explains our observations is presented.
Oxi‐ammoniation of pine‐bark particles
Authors: Coca J. , Alvarez R. , Fuertes A. B. , Alonso F. J.
Published: March 2009

Pine‐bark sawdust was oxidized with nitric acid (5‐20% by weight) and further ammoniated with NH3 or NH4OH. Ammoniation with NH3 was carried out in a fluidized bed reactor at 100 and 250°C and a NH, flow of 126 L/h (0°C; 101.3 kPa). Ammoniation with NH4OH was carried out in a batch reactor by reacting the oxidized sample with NH4OH (2 kmol/m3) at total reflux. Data on total nitrogen, ammonia nitrogen and KMnO4 soluble nitrogen content are reported for the resulting product.
A generalized solution method for the quasi‐chemical local composition equations
Authors: Abusleme J. A. , Vera J. H.
Published: March 2009

The work of Abusleme and Vera based on the Quasi‐Chemical Theory of Guggenheim in terms of groups is extended to multicomponent multigroup mixtures. The nonlinear equations arising from the theory are rearranged in a particular way that allows them to be solved using a generalized Newton‐Raphson method. Initial estimates of the values of the non‐random factors are obtained with a Taylor expansion around the random values. No more than five iterations are required for typical systems. Practical applications of the method are presented for ternary group systems.
Uniformity of fluidization on a multi‐orifice gas distributor
Authors: Baskakov A. P. , Tuponogov V. G. , Philippovsky N. F.
Published: March 2009

As the gas flow rate is increased through a bed of particles lying on a multi‐orifice gas distributor, several gas pressure maxima arise in the plenum chamber which correspond to the occurrence of fluidization in different sections of the bed. The gas pressure at the distributor orifices may considerably exceed the quantiy ρsg(1 − ϵ0)H. A formula has been derived for the complete‐fluidization index at which all caps come into play.
A stochastic model for the filtration of dilute suspensions using non‐woven cloths
Authors: Wilkinson E. T. , Davies G. A.
Published: March 2009

A model is described to simulate a non‐woven unneedled fibre filter which describes the basic random structure of these materials. Good agreement is obtained between the observed structure of non‐woven filter fabrics and the predictions of the model. Data on the pore structure, pore area, perimeter and hydraulic radius can be predicted from the model.

This description of a non‐woven filter is used in a stochastic trajectory model to calculate particle filtration. The analysis applies to filtration of dilute suspensions in the regime where particle screening is the predominant mechanism of filtration. The model predicts that the penetration into the filter decays exponentially with depth in the direction of flow. The interaction between the particle distribution on filter media (pore distribution) is taken fully into account in the analysis. The computational method allows the effect of particle size distribution on filtration efficiency, pore blockage and pore binding to be evaluated.
Study of complexing reactions causing the depletion of gadolinium ions from the moderator of CANDU‐PHW nuclear reactors
Authors: Gilbert Roland , Lépine Louis , Laurin Michel , Ouellet Lorenzo , Gauthier Rosanne
Published: March 2009

The addition of gadolinium nitrate solution in the moderator of Hydro‐Québec's Gentilly 2 reactor led to an unexpected depletion of gadolinium (Gd) by precipitation. Analysis of moderator samples revealed that bicarbonate (HCO3−) was the main anionic impurity. A study of the complexing reactions of Gd in concentrated solutions (0.0509M) of Gd(NO3)3 showed that in the absence of HCO3− and at pH < 6, the species in equilibrium are distributed as follows: predominant: Gd3+, NO3− and [GdNO3]2+; and traces: [GdOH]2+ and [Gd(NO3)2]+. An increase in pH over 6.4 led to the formation of the solid phase: Gd2(OH)5.1(NO3)0.9. In the presence of bicarbonate, the solid phase Gd2(OH)5.0(NO3)1.0 is visually detected at a pH as low as 5.8. In other respects, analysis of dilute solutions (0.00065M) of Gd(NO3)3 containing bicarbonate allows the solid phase precipitating between pH 5.5 and 6.6 to be ascribed to the formula Gd2(OH)4CO3·3H2O. In the absence of HCO3−, no precipitation occurred up to pH 6.8. Finally, the loss of Gd from the moderator was established as being due to the formation of a hydroxide carbonate salt.
Contacting modes and behaviour classification of gas—solid and other two‐phase suspensions
Authors: Grace John R.
Published: March 2009

An attempt is made to extend schemes for classifying the behaviour of gas—solid contacting modes and other two‐phase systems. The regime diagram approach of Reh (1971) is modified and extended to cover the operating regions of common reactors and contactors where a gas flows upwards through a bed of solids including fixed and moving packed beds, conventional fluidized beds, circulating beds, spouted beds, and pneumatically conveyed suspensions. New boundaries are proposed between groups A and B and between groups B and D of the Geldart (1972, 1973) powder classification scheme. These boundaries reflect more recent data and allow the classification scheme to be used for gases other than air and for temperatures and pressures other than atmospheric.
The permeability of fibrous porous media
Authors: Jackson Graham W. , James David F.
Published: March 2009

The literature was searched for experiments and theories related to low‐Reynolds‐number flow through fibrous porous media, particularly highly porous structures. Experimental data were found for a wide range of materials, from polymer chains to fiberglass, and the results collapse reasonably well when the appropriate dimensionless co‐ordinates are employed. Of the theories, accurate solutions of Stokes equation are available for regular arrays of parallel rods, either aligned with or normal to the flow. For irregular arrays and three‐dimensional media, approximate permeabilities can be calculated from several flow models.
The geometrical evaluation of effective diffusion coefficient in the liquid phase for porous bodies consisting of spherical elementary particles
Authors: Kobayashi Jun‐Ichi , Katsuzawa Hideo
Published: March 2009

To evaluate the intraparticle diffusion coefficient, De, of a component in a liquid, it was assumed that the pore structure of a porous catalyst was a space between an assembly of fine particles. This structure has been found for the metal oxide catalysts. The diffusivity ratio, δ (= De/D), was geometrically estimated in the direction normal to the representative plane (100), (110) or (111) of cubic closed, body centered cubic, simple cubic, or diamond packing of spherical elementary particles. The value δ was found to approximate the porosity ϵ. Larger pore constrictions gave smaller δ/ϵ values. Reaction rates were measured for the hydrogenation of nitrobenzene in ethanol. The efficiency of this evaluation of De was supported by the agreement of the experimental effectiveness factor with the theoretical factor.
Interconversion of light olefins—aromatics over zeolite catalysts
Authors: Mao Raymond Le Van , LÉVesque Pierre , Sjiariel Bernard , Nguyen Do Thi
Published: March 2009

Improved yield in light olefins and aromatics from methanol conversion was observed on Zn and Mn loaded ZSM‐5 zeolite—asbestos catalysts. The best results in terms of conversion into hydrocarbons were obtained with a Zn content not exceeding 0.6% wt/wt. The light olefins/aromatics ratio in the products varied with the Mn content in the catalyst, the cumulative light olefinic and aromatic production being kept constant at a high value.
Phase equilibria of oil, gas and water/brine mixtures from a cubic equation of state and henry's law
Authors: Li Yau‐Kun , Nghiem Long X.
Published: March 2009

This paper presents the predictions and calculations of the phase equilibria of oil, gas and water/brine mixtures where the oil and gas are modeled by a cubic equation of state and where the gas solubility in the aqueous phase is estimated from Henry's law. Henry's law constants for a variety of compounds of interest to the petroleum industry are correlated against pressure and temperature. The scaled‐particle theory is used to take into account the presence of salt in the aqueous phase. An extensive match of experimental data is presented, showing the adequacy of the proposed model for Henry's law constant.
Aortic Dissection in Childhood and Adolescence: An Analysis of Occurrences Over a 10‐Year Interval in New York State
Authors: Fikar Charles R. , Fikar Ronald
Published: March 2009

Background

Rarely occurring in the pediatric and adolescent population, aortic dissection is a condition with many predisposing factors. Previous studies have suggested that congenital cardiovascular disorders are the most common predisposing conditions. Trauma‐associated aortic dissection is considered a rare occurrence.

Methods

The Statewide Planning and Research Cooperative System database of New York State was used to retrieve cases of aortic dissection in persons ≤ 21 years old over a 10‐year period. A retrospective analysis for risk or associated conditions was undertaken.

Results

Forty‐five of a total of 12 142 cases of aortic dissection (0.37%) occurred in persons ≤ 21 years old. No patient was younger than 15 years of age. Six of the 45 died (13%). Most patients were male (37 of 45, or 82%). Contrary to previous reports, the most common associated condition was trauma (19 of 45, or 42%), with Marfan syndrome the second most common (11 of 45, or 24%). Ten of 45 adolescent and young adult patients (22%) had no apparent risk factors.

Conclusions

Traumatic aortic disruptions must be considered in children and adolescents who survive serious chest trauma. Family members of pediatric and young adult patients with trauma‐associated aortic dissection may need to be evaluated for possible risk of aortic dissection. Copyright © 2009 Wiley Periodicals, Inc.
3D QSAR Models Built on Structure‐Based Alignments of Abl Tyrosine Kinase Inhibitors
Authors: Falchi Federico , Manetti Fabrizio , Carraro Fabio , Naldini Antonella , Maga Giovanni , Crespan Emmanuele , Schenone Silvia , Bruno Olga , Brullo Chiara , Botta Maurizio
Published: March 2009

Quality QSAR: A combination of docking calculations and a statistical approach toward Abl inhibitors resulted in a 3D QSAR model, the analysis of which led to the identification of ligand portions important for affinity. New compounds designed on the basis of the model were found to have very good affinity for the target, providing further validation of the model itself.

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The X‐ray crystallographic coordinates of the Abl tyrosine kinase domain in its active, inactive, and Src‐like inactive conformations were used as targets to simulate the binding mode of a large series of pyrazolo[3,4‐d]pyrimidines (known Abl inhibitors) by means of GOLD software. Receptor‐based alignments provided by molecular docking calculations were submitted to a GRID‐GOLPE protocol to generate 3D QSAR models. Analysis of the results showed that the models based on the inactive and Src‐like inactive conformations had very poor statistical parameters, whereas the sole model based on the active conformation of Abl was characterized by significant internal and external predictive ability. Subsequent analysis of GOLPE PLS pseudo‐coefficient contour plots of this model gave us a better understanding of the relationships between structure and affinity, providing suggestions for the next optimization process. On the basis of these results, new compounds were designed according to the hydrophobic and hydrogen bond donor and acceptor contours, and were found to have improved enzymatic and cellular activity with respect to parent compounds. Additional biological assays confirmed the important role of the selected compounds as inhibitors of cell proliferation in leukemia cells.
Molecular Modeling and Molecular Dynamics Studies of Hydralazine with Human DNA Methyltransferase 1
Authors: Singh Narender , Dueñas‐González Alfonso , Lyko Frank , Medina‐Franco Jose L.
Published: March 2009

A series of DNA methyltransferase 1 (DNMT1) inhibitors were modeled by docking and molecular dynamics studies to rationalize their activity. Our findings will be valuable in guiding research efforts toward the rational design and virtual screening of novel DNMT inhibitors.

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DNA methyltransferases (DNMTs) are a family of enzymes that methylate DNA at the C5 position of cytosine residues, and their inhibition is a promising strategy for the treatment of various developmental and proliferative diseases, particularly cancers. In the present study, a binding model for hydralazine, with a validated homology model of human DNMT, was developed by the use of automated molecular docking and molecular dynamics simulations. The docking protocol was validated by predicting the binding mode of 2′‐deoxycytidine, 5‐azacytidine, and 5‐aza‐2′‐deoxycytidine. The inhibitory activity of hydralazine toward DNMT may be rationalized at the molecular level by similar interactions within the binding pocket (e.g., by a similar pharmacophore) as established by substrate‐like deoxycytidine analogues. These interactions involve a complex network of hydrogen bonds with arginine and glutamic acid residues that also play a major role in the mechanism of DNA methylation. Despite the different scaffolds of other non‐nucleoside DNMT inhibitors such as procaine and procainamide, the current modeling work reveals that these drugs exhibit similar interactions within the DNMT1 binding site. These findings are valuable in guiding the rational design and virtual screening of novel DNMT inhibitors.
Stathmin and tubulin expression and survival of ovarian cancer patients receiving platinum treatment with and without paclitaxel
Authors: Su Dan , Smith Stephanie M. , Preti Mario , Schwartz Peter , Rutherford Thomas J. , Menato Guido , Danese Saverio , Ma Shenglin , Yu Herbert , Katsaros Dionyssios
Published: March 2009

BACKGROUND:

Paclitaxel interacts with microtubules to exert therapeutic effects. Molecules that affect microtubule activity, such as βIII‐tubulin and stathmin, may interfere with the treatment. In this study, the authors analyzed βIII‐tubulin and stathmin expression in ovarian tumors and examined their associations with treatment response and patient survival.

METHODS:

The study included 178 patients with epithelial ovarian cancer who underwent cytoreductive surgery followed by platinum‐based chemotherapy; of these patients, 75 also received paclitaxel. Fresh tumor samples that were collected at surgery were analyzed for messenger RNA expression of βIII‐tubulin and stathmin using real‐time polymerase chain reaction analysis. Associations of these molecules with treatment response, disease progression, and overall survival were evaluated.

RESULTS:

High stathmin expression was associated with worse disease progression‐free and overall survival compared with low stathmin expression. This association was independent of patient age, disease stage, tumor grade, histology, and residual tumor size and was observed in patients who received platinum plus paclitaxel, but not in patients who received platinum without paclitaxel, suggesting that stathmin expression in tumor tissue may interfere with paclitaxel treatment. Similar effects were not observed for βIII‐tubulin, although high βIII‐tubulin expression was associated with disease progression among patients who received platinum without paclitaxel. No associations were observed between treatment response and tubulin or stathmin expression. Expression levels of βIII‐tubulin and stathmin were correlated significantly.

CONCLUSIONS:

High stathmin expression predicted an unfavorable prognosis in patients with ovarian cancer who received paclitaxel and platinum chemotherapy. This finding supports the possibility that stathmin may interfere with paclitaxel treatment, leading to a poor prognosis for patients with ovarian cancer. Cancer 2009. © 2009 American Cancer Society.