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Molecular mechanisms and process kinetics of crystallizing concomitant polymorphs remain poorly understood. Solvent-mediated phase transformation is often mistaken as concomitant crystallization, mainly due to the two processes sharing similar kinetic profiles. Herein, we developed a population balance model to simulate a concomitant crystallization process of two polymorphs of tolfenamic acid (TFA). The kinetic modeling aims to better understand concomitant crystallization and help guide form selection of such a molecular system. Crystallization kinetics of ethanolic TFA solutions were uncovered from induction time measurements, as well as seeded and unseeded crystallization experiments. Both experimental and simulation results demonstrate that the stable form I crystallizes concomitantly with the metastable form II. The faster growing form II results in an intermediate decline in the kinetic profile of form I composition in crystallized samples, a characteristic feature of the concomitantly crystallized system. A four-quadrant scheme of attainable polymorph outcome was simulated under various crystallization conditions.

Over the years a significant amount of effort has been put into the development of rapid and reliable methods to monitor the aggregation dynamics of the β1-42 amyloid peptide in real time. We present an alternative approach based on a suitable reporter or spy molecule and three different NMR experiments: WaterLOGSY, 1 H selective T1 filter, and 19 F T2 filter, for monitoring the initial self-aggregation process kinetics of the β1-42 amyloid peptide and identifying molecules that retard or accelerate the self-aggregation process. Although the proposed method is not a high-throughput assay, it avoids problems associated with interference events that are sometimes observed in fluorescence-based assays.

Significant effort and resource expenditure is dedicated to enabling low-solubility oral drug delivery using solubilization technologies. Cyclodextrins (CD) are cyclic oligosaccharides which form inclusion complexes with many drugs and are often used as solubilizing agents. It is not clear prior to developing a drug delivery device with CD what level of absorption enhancement might be achieved; modeling can provide useful guidance in formulation and minimize resource intensive iterative formulation development. A model was developed to enable quantitative, dynamic prediction of the influence of CD on oral absorption of low solubility drug administered as a pre-formed complex. The predominant effects of CD considered were enhancement of dissolution and slowing of precipitation kinetics, as well as binding of free drug in solution. Simulation results with different parameter values reflective of typical drug and CD properties indicate a potential positive (up to five times increase in drug absorption), negative (up to 50% decrease in absorption) or lack of effect of CD. Comparison of model predictions with in vitro and in vivo experimental results indicate that a systems-based dynamic model incorporating CD complexation and key process kinetics may enable quantitative prediction of impact of CD delivered as a pre-formed complex on drug bioavailability. Biotechnol. Bioeng. 2013; 110:2536–2547. © 2013 Wiley Periodicals, Inc.

Large-scale algal culture remains an attractive concept primarily because of the enormous potential productivity that such systems offer. However, the problem of harvesting microalgae remains a major obstacle. This paper examines the usefulness of using brine shrimp culture as a technique for harvesting microalgae and converting to protein and lipid. Specifically a mathematical model which describes brine shrimp growth and conversion efficiency is presented. The usefulness of this model is illustrated by solving for the required brine shrimp biomass needed for conversion of a constant rate of production of single-celled marine diatoms. The model is further used to demonstrate that the most useful design of such a conversion system is that of a two-stage system in which the first stage consists of a reactor, or reactors, of young animals operating at low algal cell removal efficiencies followed by a number of reactors of increasing age groups operating in parallel flow arrangement. This arrangement permits a high overall rate of continuous cell removal.

The degradation of a non-inhibitory substrate (sucrose) in upflow anaerobic sludge bed (UASB) reactors with different superficial flow velocites (us) was performed to generate experimental data. Additionally, a kinetic model accounting for the mass fraction of methanogens (f) and granule size distribution in UASB reactors is also proposed. At the volumetric loadings of 2.65–21.16 g COD dm−3 day−1, both the COD removal efficiency and granule size of the UASB reactors increase with increasing us. The f values determined experimentally increase from 0.13–0.24 to 0.27–0.43 if the volumetric loading is increased from 2.65 to 5.29 g COD dm−3 day−1. With a further increase in volumetric loading, the f values decline because of the accumulation of volatile fatty acids (VFAs). The predicted residual concentrations of VFAs and COD are in fairly good agreement with the experimental data. From the calculated effectiveness-factor values, the influence of mass transfer resistance of the substrate sucrose on the overall substrate removal rate should not be neglected. From parametric sensitivity analyses together with the simulated concentration profiles, methanogenesis is the rate-limiting step. Copyright © 2003 Society of Chemical Industry

The clarification of grape juices produces a colored non-pomace residue that is continuously discarded. This study evaluated the drying kinetics of the non-pomace residue of organic and conventional grape juices (V. labrusca L.) and assessed the effect of drying process on the anthocyanins content and microstructure of this residue. Residue samples were subject to convective drying and the process kinetics was modeled using four semi-empirical models. The Page model was selected as the best-fit model obtaining the lowest chi-square values (χ2 < 0.000733). The effective diffusivity values ranged from 9.08 × 10−4 to 1.52 × 10−3 m2/s and the activation energies values were 23.06 and 20.89 kJ/mol for organic and conventional residues, respectively. The drying rate was augmented by increasing temperature with maximum values at 65 °C, for which the micrographs revealed the formation of smaller particles in samples when compared with drying at 45 and 55 °C. The conventional residue showed the highest levels of anthocyanins, which were consistently decreased with temperature as function of time, indicating that those are critical parameters for technological applications of this polyphenol-rich matrix. Practical applications The clarification process is an important technological stage for processing of fruit juices. Grape juices are widely appreciated worldwide and the accumulation of viticulture by-products is a current concern in many producing regions. There is a global demand for reducing organic waste in food industries and alternatives for reutilization of plant materials emerge as a rewarding alternative to produce food ingredients. The non-pomace residue of grape juices is a solid and highly-colored material rich in polyphenols that is continuously discarded and currently unexplored. The study of its chemical properties as well as the use of drying processes to allow its technological application provides an important solution in order to achieve waste reduction in viticulture and discovering new matrices as sources of bioactive polyphenols.

Oxidation of BaF2 single-crystals as a result of annealing in air in the temperature range 600° to 900 °C leads to mechanical strengthening. The process kinetics was investigated. It is shown that oxidation takes place in the bulk of crystals owing to oxygen diffusion by formation and growth of oxidation centres. These centres are precipitates of a BaO phase which were revealed by chemical etching. [Russian Text Ignored.]

A mathematical model of the batch acetone-butanol fermentation has been proposed which reflects the process kinetics and biochemistry. The degree of importance of the key kinetic parameters has been established by a parametric sensitivity analysis. The basic model was further extended by incorporating additional culture physiological parameters such as the number of active mass transport sites and the permeability of the cellular membrane as well as the intracellular and extracellular conditions. The model assisted in studying the role of the cellular membrane in the control of the culture performance and solvent biosynthesis. The theoretical predictions were confirmed by experimental results. On propose un modele mathematique de la fermentation discontinue en acetone-butanol, decrivant la cinetique et la biochimie du procede. L'importance des parametres cinetiques cles a ete etablie grǎce a une analyse de sensibilite parametrique. Le modele initial a ete ameliore par l'ajout d'autres parametres physiologiques de cultures comme le nombre de sites actifs de transfert de matiere, la permeabilite de la membrane cellulaire ainsi que les conditions intracellulaires ou extracellulaires. Le modele a servi a etudier le rǒle de la membrane cellulaire dans le contrǒle de la performance des cultures et de la biosynthese du solvant. Les predictions theoriques ont ete confirmees par des resultats experimentaux.

The role of vapor liquid equilibrium in the coal liquefaction process and its effect on the process kinetics were studied. Available experimental data were analyzed by inclusion of vapor-liquid equilibrium in an existing model to study its effect on the kinetics. The analysis showed that due to liquid vaporization, a significant increase in the slurry residence time occurs. In the range of operating variables investigated, the actual slurry residence time was observed to be higher by a factor of 1.14 to 1.41. Model simulations for some typical operating conditions (717-737 K, 13.8-20.7 MPa) showed the wt. fraction of liquid vaporized to be in the range of 0.1 to 0.3. This is seen to be in agreement with published data on the volatility of typical coal liquids. This study has shown that consideration of vapor-liquid equilibrium in the kinetics and design of coal liquefaction process can be of importance, especially at high temperatures, where vaporization would be significant. On a etudie le ro'le de l'equilibre liquide-vapeur dans le processus de liquefaction du charbon et son effet sur la cinetique de ce processus. On a etudie les donnees experimentales disponibles en introduisant l'equilibre liquide-vapeur dans un modele existant pour etudier son effet sur la cinetique. L'analyse a indique que, par suite de la vaporisation du liquide, un accroissement important du temps de sejour de la suspension se produit. On a observe que, dans le domaine des variables operatoires etudiees, le temps de sejour reel de la suspension etait accru d'un facteur de 1.14 a 1.41. Des simulations par modele, faites dans le cas de certaines conditions operatoires typiques (de 717 a 737 K et de 13.8 a 20.7 MPa), ont indique que la fraction ponderale des liquides vaporises variait entre 0.1 et 0.3; ces resultats concordent bien avec les donnees de la litterature technique relatives a la volatilite de liquides typiques provenant du charbon. Cette etude a indique que la prise en consideration de l'equilibre liquide-vapeur dans la cinetique et la conception d'un procede de liquefaction du charbon peut e'tre significative, surtout aux temperatures elevees, lorsque la vaporisation est importante.

Choosing the type of laboratory reactor for evaluating process kinetics may be the most crucial step in an industrial process development program. Not only would a wrong choice result in expensive delays, but data may be obtained which would scale-up erroneously, leading to a disastrous commercial design. Some of the pitfalls and limitations of various laboratory reactors are discussed for some typically complex industrial reaction systems. A modus operandi is suggested for choosing from among the potential reactors those that have the best chance of supplying the desired data. As is typical of many complex industrial reaction systems, no one reactor turns out to be ideal and many times the building of two or more types is advantageous.

The anaerobic fluidised bed system for methane recovery from liquid wastes is modelled as a continuous-flow, completely-mixed homogeneous microbial system, with the feed COD as the limiting substrate concentration. The average microbial residence time in the reactor is defined in terms of conventional sludge retention time. The experimental data obtained indicate that the Michaelis-Menten expression is applicable for description of substrate utilisation (i.e. COD removal) in the anaerobic fluidised bed system. The observed biomass yield in the reactor decreases with increasing sludge retention time which is consistent with the prediction of the biokinetic theory developed for suspended-growth systems. The specific methane production rate observed is a linear function of the specific substrate utilisation rate.

Variations in the dislocation density have been observed directly on annealing deformed copper monocrystals in an electron microscope. The process kinetics conforms to a second-order reaction. The recovery of the dislocation electrical resistance proportional to the mean dislocation density in the crystal was studied in massive monocrystals. Isochronous annealing, as well as annealing under isothermal conditions, were carried out. Two stages were observed on the isochronous annealing curves, one at temperatures below 250 °C, the other in the range from 250 to 450 °C. These two stages correspond to the two substages of the dislocation recovery. [Russian Text Ignored]