PRODUCTION AND OPERATIONS MANAGEMENT, Issue 4 2002
CHIEN-YU CHEN
The available-to-promise (atp) function is becoming increasingly important in supply chain management since it directly links production resources with customer orders. In this paper, a mixed integer programming (mip) ATP model is presented. This model can provide an order-promising and -fulfillment solution for a batch of orders that arrive within a predefined batching interval. A variety of constraints, such as raw material availability, production capacity, material compatibility, and customer preferences, are considered. Simulation experiments using the model investigate the sensitivity of supply chain performance to changes in certain parameters, such as batching interval size and customer order flexibility. [source]

Batch and fed-batch carotenoid production by Rhodotorula glutinis,Debaryomyces castellii co-cultures in corn syrup

JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001
P. BuzziniArticle first published online: 21 DEC 200
Aims: Investigations on the production of red pigments by Rhodotorula glutinis on raw substrates of agro-industrial origin may be considered of interest because they represent the first approach to the utilization of these raw materials for biotechnological purposes. Methods and Results:Rhodotorula glutinis DBVPG 3853 was batch and fed-batch co-cultured with Debaryomyces castellii DBVPG 3503 in a medium containing corn syrup as the sole carbon source. Fed-batch co-cultures gave a volumetric production of 8·2 mg total carotenoid l,1, about 150% of that observed in batch co-cultures. The different carotenoid pigments (,-carotene, torulene, torularhodin) were quantified. Conclusions: Oligosaccharides and dextrins of corn syrup could be used profitably for pigment production by R. glutinis DBVPG 3853,D. castellii DBVPG 3503 in co-culture. Significance and Impact of the Study: The above results suggest that the red yeasts belonging to the genus Rhodotorula may have industrial relevance as carotenoid producers. [source]

Batch and continuous studies on treatment of pulp mill wastewater by Aeromonas formicans

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2001
K Gupta
Abstract Batch and continuous studies have been conducted on the treatment of black liquor from a kraft pulp and paper mill by a bacterial strain, Aeromonas formicans. The results of batch studies revealed that the strain was able to remove 71% and 78% of COD and lignin respectively, while the colour removal efficiency was around 86% in 10 days of retention time. The analysis of lignin degradation products by gas chromatography after 20 days of incubation revealed the formation of some phenolic acids, which were responsible for the decrease in pH during batch studies. The removal efficiencies of COD, colour and lignin obtained in continuous reactor studies were 73, 88 and 77% respectively for an 8 day detention period and these efficiencies were almost the same as obtained in batch studies. © 2001 Society of Chemical Industry [source]

A collaborative study to establish the 7th International Standard for Factor VIII Concentrate

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 1 2005
S. Raut
Summary., A candidate concentrate, preparation N (99/678), was assayed and calibrated, as a potential replacement, against four established factor (F) VIII concentrate standards: the current WHO 6th International Standard (IS) (97/616), the previous 5th IS (88/640), the Mega 1 standard and Ph. Eur. BRP Batch 2 standard, in a collaborative study involving 38 laboratories. All laboratories were instructed to use the ISTH/SSC recommendations, including predilution of concentrates in FVIII-deficient plasma. Several laboratories performed more than one assay method and altogether there were 27 sets of assays with the one-stage method, 31 with the chromogenic method, and 18 with both methods. There was good agreement between laboratories using each of the two methods for comparison of preparation N against the four established standards, with overall potencies by one-stage and chromogenic methods differing only by less than 2%. However, there were significant differences in potencies relative to the different standards, ranging from 10.1 IU per ampoule against the Ph. Eur.BRP2 to 11.4 against the WHO 6th IS. Accelerated degradation studies showed that the proposed standard is very stable, with a predicted loss of activity per year of less than 0.001% at the recommended storage temperature of ,20 °C. Various options for potency of preparation N were considered by the participants and by members of the ISTH/SSC FVIII/FIX Subcommittee. In November 2003, preparation N (NIBSC 99/678) was proposed to and accepted by the Expert Committee on Biological Standardization of the World Health Organization to be the 7th International Standard for Factor VIII Concentrate with an assigned potency of 11.0 IU per ampoule. [source]

Atom-Transfer Radical Batch and Semibatch Polymerization of Styrene

MACROMOLECULAR REACTION ENGINEERING, Issue 4 2007
Yao Fu
Abstract Batch and semibatch styrene polymerizations are carried out using a heterogeneous ATRP catalyst system that provides excellent molecular-weight control. The observed initiator efficiency is lower for semibatch operation due to the high initiator concentrations required to make a low-MW polymer. Experiments verified that the insoluble metal complex does not participate in the polymerization and that Cu(I) solubility is an order of magnitude higher than that of Cu(II). A mechanistic model, using kinetic coefficients from literature and the solubility data from this study, provides a good representation of the experimental results. [source]

Engineering analysis of crosslinking polymerization of diallyl lsophthalate

POLYMER ENGINEERING & SCIENCE, Issue 3 2000
Bogdan Znoj
A kinetic model for crosslinking free radical polymerization of DAIM (monomer diallyl isophthalate) with initiator CHPC (dicyclohexyl peroxydicarbonate) is developed. An improved version of Batch and Macosko's model was used to describe the initiator efficiency (f) and the active radical fraction (Fact). The experimental data of allyl and carbonyl group consumption are used for the optimization of the model and calculating of f and Fact. From the developed kinetic model and experimental results, obtained by FT-IR measurements of monomer conversion, the introduction of the Fact was proved. Application of this model may be of use in process modeling of DAIM and other crosslinking polymerizations with CHPC as initiator. [source]

Local dynamic partial least squares approaches for the modelling of batch processes

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2008
N. M. Fletcher
Abstract The application of multivariate statistical projection based techniques has been recognized as one approach to contributing to an increased understanding of process behaviour. The key methodologies have included multi-way principal component analysis (PCA), multi-way partial least squares (PLS) and batch observation level analysis. Batch processes typically exhibit nonlinear, time variant behaviour and these characteristics challenge the aforementioned techniques. To address these challenges, dynamic PLS has been proposed to capture the process dynamics. Likewise approaches to removing the process nonlinearities have included the removal of the mean trajectory and the application of nonlinear PLS. An alternative approach is described whereby the batch trajectories are sub-divided into operating regions with a linear/linear dynamic model being fitted to each region. These individual models are spliced together to provide an overall nonlinear global model. Such a structure provides the potential for an alternative approach to batch process performance monitoring. In the paper a number of techniques are considered for developing the local model, including multi-way PLS and dynamic multi-way PLS. Utilising the most promising set of results from a simulation study of a batch process, the local model comprising individual linear dynamic PLS models was benchmarked against global nonlinear dynamic PLS using data from an industrial batch fermentation process. In conclusion the results for the local operating region techniques were comparable to the global model in terms of the residual sum of squares but for the global model structure was evident in the residuals. Consequently, the local modelling approach is statistically more robust. L'application de techniques basées sur la projection statistique multivariée est reconnue comme étant une approche qui contribue à une meilleure compréhension du comportement des procédés. Les méthodologies clés incluent l'analyse des composantes principales (PCA) à plusieurs critères de classification, les moindres carrés partiels (PLS) à plusieurs critères de classification et l'analyse des niveaux d'observation discontinus. Les procédés discontinus présentent typiquement un comportement non linéaire et variable dans le temps et ces caractéristiques mettent au défi les techniques mentionnées ci-dessus. Devant ces défis, la méthode PLS dynamique est proposée pour saisir la dynamique des procédés. Des approches semblables pour supprimer la non linéarité des procédés incluent le retrait de la trajectoire principale et l'application des PLS non linéaires. On décrit une autre approche où les trajectoires discontinues sont subdivisées en régions opératoires avec un modèle dynamique linéaire/linéaire adapté à chaque région. Ces modèles individuels sont raccordés pour obtenir un modèle non linéaire global. Une telle structure présente un potentiel pour une approche différente du suivi des performances des procédés discontinus. Dans cet article, plusieurs techniques sont considérées pour la mise au point du modèle local, incluant les PLS à plusieurs critères de classification et les PLS à plusieurs critères de classification dynamique. En utilisant la série de résultats les plus prometteurs d'une étude de simulation d'un procédé discontinu, le modèle local comprenant les modèles de PLS dynamiques linéaires individuels a été comparé à la méthode de PLS non linéaires dynamique globale utilisant des données d'un procédé de fermentation discontinu industriel. En conclusion, les résultats pour les techniques des régions opératoires locales sont comparables au modèle global en termes de somme des carrés des résidus mais pour le modèle global, la présence d'une structure dans les résidus est évidente. En conséquence, l'approche de modélisation locale est statistiquement plus robuste. [source]

Transition from Batch to Continuous Operation in Bio-Reactors: A Model Predictive Control Approach and Application

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2007
Prashant Mhaskar
Abstract This work considers the problem of determining the transition of ethanol-producing bio-reactors from batch to continuous operation and subsequent control subject to constraints and performance considerations. To this end, a Lyapunov-based non-linear model predictive controller is utilized that stabilizes the bio-reactor under continuous mode of operation. The key idea in the predictive controller is the formulation of appropriate stability constraints that allow an explicit characterization of the set of initial conditions from where feasibility of the optimization problem and hence closed-loop stability is guaranteed. Additional constraints are incorporated in the predictive control design to expand on the set of initial conditions that can be stabilized by control designs that only require the value of the Lyapunov function to decay. Then, the explicit characterization of the set of stabilizable initial conditions is used in determining the appropriate time for which the reactor must be run in batch mode. Specifically, the predictive control approach is utilized in determining the appropriate batch length that achieves stabilizable values of the state variables at the end of the batch. Application of the proposed method to the ethanol production process using Zymomonas mobilis as the ethanol producing micro-organism demonstrates the effectiveness of the proposed model predictive control strategy in stabilizing the bio-reactor. Ce travail porte sur le problème de la détermination de la transition entre le fonctionnement discontinu et continu pour des bioréacteurs produisant de l'éthanol et sur le contrôle subséquent lorsque ceux-ci sont soumis à des contraintes et des considérations de performance. À cette fin, on utilise un contrôleur prédictif par modèles non linéaires de type Lyapunov qui stabilise le bioréacteur lorsqu'il est en mode de fonctionnement continu. L'idée maîtresse dans le contrôleur prédictif est la formulation de contraintes de stabilité appropriées qui permettent une caractérisation explicite du jeu des conditions initiales à partir de laquelle la faisabilité du problème d'optimisation et donc la stabilité en boucle fermée sont garanties. Des contraintes additionnelles sont introduites dans la conception du contrôle prédictif pour étendre le jeu de conditions initiales qui peuvent être stabilisées par la conception du contrôle qui requiert seulement que la valeur de la fonction de Lyapunov diminue. Ensuite, la caractérisation explicite du jeu des conditions initiales stabilisables est utilisée dans la détermination de la durée de fonctionnement adéquate pour laquelle le réacteur doit fonctionner en mode discontinu. Spécifiquement, on utilise la méthode de contrôle prédictif dans la détermination de la longueur discontinue appropriée qui réalise les valeurs stabilisables des variables d'état à la fin du mode discontinu. L'application de la méthode proposée au procédé de production de l'éthanol utilisant Zymomonas mobilis comme microorganisme produisant de l'éthanol, démontre l'efficacité de la stratégie de contrôle prédictif de modèles proposée pour stabiliser le bioréacteur. [source]

Scaleable downstream recovery of nematodes used as biopesticides

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2001
J.A. Wilson
Abstract This study assesses the suitability of sieving as a scaleable technique for the separation of adult nematodes from infective juveniles, the latter is an effective bioinsecticide whereas the former is waste material resulting from the fermentation process. Batch and semibatch experiments using conventional flow-assisted wet sieving and a novel cross-flow sieving technique were used to study the separation of juveniles from adult nematodes. The experiments were carried out using small-scale devices and the data were analyzed in terms of the screen effectiveness factor. The results were used to identify the sieve size and operating conditions for optimum juvenile recovery. It was found that, for a given species of nematode, optimum recovery was achieved when sieving was carried out in the cross-flow mode, the maximum recovery being a function of the size of the screen. Industrial-scale self-cleaning equipment capable of large-scale continuous screening was used to confirm the capacity of the small-scale operation for scale-up. Experimental results with this unit showed that in continuous operation sieving time is an additional parameter that influences separation performance. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 733,740, 2001. [source]

Logistic Equations Effectively Model Mammalian Cell Batch and Fed-Batch Kinetics by Logically Constraining the Fit

BIOTECHNOLOGY PROGRESS, Issue 4 2005
Chetan T. Goudar
A four-parameter logistic equation was used to fit batch and fed-batch time profiles of viable cell density in order to estimate net growth rates from the inoculation through the cell death phase. Reduced three-parameter forms were used for nutrient uptake and metabolite/product formation rate calculations. These logistic equations constrained the fits to expected general concentration trends, either increasing followed by decreasing (four-parameter) or monotonic (three-parameter). The applicability of this approach was first verified for Chinese hamster ovary (CHO) cells cultivated in 15-L batch bioreactors. Cell density, metabolite, and nutrient concentrations were monitored over time and used to estimate the logistic parameters by nonlinear least squares. The logistic models fit the experimental data well, supporting the validity of this approach. Further evidence to this effect was obtained by applying the technique to three previously published batch studies for baby hamster kidney (BHK) and hybridoma cells in bioreactors ranging from 100 mL to 300 L. In 27 of the 30 batch data sets examined, the logistic models provided a statistically superior description of the experimental data than polynomial fitting. Two fed-batch experiments with hybridoma and CHO cells in benchtop bioreactors were also examined, and the logistic fits provided good representations of the experimental data in all 25 data sets. From a computational standpoint, this approach was simpler than classical approaches involving Monod-type kinetics. Since the logistic equations were analytically differentiable, specific rates could be readily estimated. Overall, the advantages of the logistic modeling approach should make it an attractive option for effectively estimating specific rates from batch and fed-batch cultures. [source]

Optimization of Cyclodextrin Glycosyltransferase Production from KlebsiellapneumoniaeAS-22 in Batch, Fed-Batch, and Continuous Cultures

BIOTECHNOLOGY PROGRESS, Issue 6 2003
Bharat N. Gawande
Production of a novel cyclodextrin glycosyltransferase (CGTase) from Klebsiella pneumoniaeAS-22 strain, which converts starch predominantly to ,-CD at high conversion yields, in batch, fed-batch, and continuous cultures, is presented. In batch fermentations, optimization of different operating parameters such as temperature, pH, agitation speed, and carbon-source concentration resulted in more than 6-fold increase in CGTase activity. The enzyme production was further improved by two fed-batch approaches. First, using glucose-based feed to increase cell density, followed by starch-based feed to induce enzyme production, resulted in high cell density of 76 g dry cell weight/L, although the CGTase production was low. Using the second approach of a single dextrin-based feed, 20-fold higher CGTase was produced compared to that in batch fermentations with media containing tapioca starch. In continuous operation, more than 8-fold increase in volumetric CGTase productivity was obtained using dextrin-based media compared to that in batch culture using starch-based media. [source]

Utilization of an Alternative Carbon Source for Efficient Production of Human ,1 -Antitrypsin by Genetically Engineered Rice Cell Culture

BIOTECHNOLOGY PROGRESS, Issue 3 2001
Masaaki Terashima
Human ,1 -antitrypsin was produced by genetically engineered rice cells using promoter and signal peptide of a rice ,-amylase isozyme. Batch and continuous cultures were employed to investigate the effects of alternative carbon sources on the ,1 -antitrypsin production. While this expression system is inducible by sugar depletion, we have found that the productivity of ,1 -antitrypsin increased 2.4- to 3.4-fold, compared with the control medium without carbon source, in medium containing an alternative carbon source, such as pyruvic acid and glyoxylic acid. The accumulated ,1 -antitrypsin in the medium containing pyruvic acid reached 18.2,24.2 mg/g-dry cell in 50,70 h by batch culture. [source]

Regioselective Enzymatic Diol Esterification in Batch and Fixed-Bed Adsorptive Reactors: Experiments and Modeling

BIOTECHNOLOGY PROGRESS, Issue 4 2000
Cristiano Migliorini
The dynamic behavior of batch and fixed-bed adsorptive reactors is studied for the enzyme-catalyzed regioselective esterification of propionic acid and 2-ethyl-1,3-hexanediol in hexane. The reaction is equilibrium-limited with an apparent equilibrium constant of 0.6 ± 0.1 at 22 °C. Moreover, accumulation of water produced in the reaction onto the biocatalyst causes a decrease in the catalytic activity. As a result, improvements in both reaction rate and final conversion can be achieved by operating in an adsorptive-reactor mode. Control of water in the reactor is achieved with a catalytically inert ion-exchange resin in Na-form. The resin prevents an excessive accumulation of water on the biocatalyst and reduces equilibrium limitations. The thermodynamic activity of water is identified as a key parameter for the design of such reactors. A mathematical model capable of predicting the water activity as a function of the varying concentrations of reactants and products is thus developed and found to successfully predict the experimental behavior observed in laboratory reactors. Substantial improvements in performance predicted by the model are seen experimentally in batch reactions and during the transient operation of continuous-flow fixed-bed reactors combining adsorptive and catalytic functions. [source]

Fast Batch to Continuous Transposition: Application to the Extraction of Andrographolide from Plants

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2006
L. Prat
Abstract A fast development method for batch to continuous process transposition is proposed. This method is based on transient regime experiment analyses and is applied to a solid-liquid extraction. The application under consideration is the extraction of an active principle from a plant in a non-sinusoidal pulsed column. Typically, the proposed signal is composed of two different periods: firstly, a classical sinusoidal pulsation step is used to mix the liquid and solid phases in the active part of the column and allow an optimal mass transfer and, secondly, an impulsion phase, used generally for the transport of solids. The extraction is carried out in a disc and doughnut column of 54,mm diameter and 3.5,m height. Liquid and solid are flowing co-currently and downwardly. This technological improvement has been implemented to solve the difficulties due to the significant heterogeneity of the matter: one part tends to float and other to sink, which always leads to a definitive flooding in classical operations. The effects of the solid flow rate and the solvent characteristics on the hydrodynamic behavior of the column are studied. The mean residence time and the total solid holdup are calculated by using a transient regime mass balance on the experimental results. These experiments allow the identification and quantification of opposite effects of the operating parameters. Mass transfer experiments have been performed and the results fit calculated values obtained by coupling the hydrodynamic and batch extraction results. Despite the simplifications made, this validates the fast development method proposed to help batch to continuous transposition. [source]

Optimierung und Steuerung von Zellkultur-Fed-Batch-Prozessen mittels einer Kollokationsmethode

CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 4 2005
B. Frahm Dr.-Ing.
Abstract Zellkultivierungen werden im industriellen Maßstab vorwiegend im Batch- oder Fed-Batch-Betrieb durchgeführt. Aufgrund diverser Eigenschaften von Zellkulturen werden beim Fed-Batch hohe Anforderungen an die Prozessführung gestellt, so dass sich durch eine optimierte Zudosierung von Nährstoffen die Raum-Zeit-Ausbeute und damit die Wirtschaftlichkeit der Prozesse erheblich steigern lassen. Vorgestellt wird eine adaptive, modellgestützte Strategie zur prozessbegleitenden Optimierung und Steuerung von Zellkultur-Fed-Batch-Prozessen. [source]

ChemInform Abstract: A Solid-Supported Organocatalyst for Highly Stereoselective, Batch, and Continuous-Flow Mannich Reactions.

CHEMINFORM, Issue 6 2010
Esther Alza
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Polymer-Supported Palladium Catalyzed Suzuki,Miyaura Reactions in Batch and a Mini-Continuous Flow Reactor System.

CHEMINFORM, Issue 15 2006
Nam T. S. Phan
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Distribution of genetic variation in farmed and natural stocks of european eel

JOURNAL OF FISH BIOLOGY, Issue 2004
J. M. Pujolar
European eel (Anguilla anguilla; Teleostei) is a valuable commercial species. However, over the past 25 years, the population of European eel has been declining to such a degree that major concerns have been raised for its long-term conservation. Since little information is available on the life-cycle and genetic structure of European eel, it has been difficult to evaluate the existence of any population substructuring. Molecular genetic methods contribute to a better knowledge of the demography and population structure in marine fish. In addition, management strategies and conservation goals must consider information on genetic substructuring as well as on life history patterns. The aim of the study is to provide more detailed knowledge on the genetic variability, demography and population substructuring of European eel by analysing and comparing natural and farmed individuals. Natural eel samples have been obtained in two geographical sites (Netherlands, France) including temporal samples in a short-scale (within years) and a long-scale (between years). Simultaneously, farmed glass eels have been grown in two separate batches during one year. Batches have been monitored and genetic samples have been obtained during the year. A combination of selection-sensitive (allozymes) and selection-neutral markers (microsatellites) has been used in the study since selection seems to play an important role in the determination of the quality of future eel spawners. Results suggest a positive correlation between growth and genetic variability since individuals attaining a large length and mass present significant higher heterozygosities. [source]

A pedagogical Web service-based interactive learning environment for a digital filter design course: An evolutionary approach

COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 3 2010
Wen-Hsiung Wu
Abstract The course of digital filter design in electronic/electrical engineering involves complicated mathematical equations and dynamic waveform variations. It is a consensus among educators that using simulation tools assist in improving students' learning experiences. Previous studies on system simulation seemed to lack an appropriate approach to design such a course. Few emphasized the design of an interactive learning environment by using an evolutionary approach. This study integrated the design concept of an evolutionary approach and Web service-based technology into a simulation system entitled Pedagogical Web Service-Based Interactive Learning Environment (PEWSILE) was introduced. The PEWSILE system contained two interactive learning environments,a simple system and an advanced system. It offered a total of six pedagogical Web services. The simple interactive learning environment included text/color-based services, and text/color/diagram-based services. The advanced interactive learning environment included batch-based, interval change-based, comparison-based, and scroll bar-based services. The study also assessed the students' performance in six pedagogical Web services covering interaction and overall use, usefulness, and intention to use through a questionnaire survey and subsequent interviews. Three significant findings were reported. For example, in the advanced interactive learning environment, the designs of interval change-based and comparison-based services make it easier to observe differences in the outcome of parameter change, while batch-based services lacks the element of waveform comparison. In sum, the findings in this study provide helpful implications in designing engineering educational software. © 2010 Wiley Periodicals, Inc. Comput Appl Eng Educ 18: 423,433, 2010; View this article online at wileyonlinelibrary.com; DOI 10.1002/cae.20163 [source]

Hybrid platform for vibration control of high-tech equipment in buildings subject to ground motion.

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2003
Part 1: experiment
Abstract This paper presents an experimental study, while a companion paper addresses an analytical study, to explore the possibility of using a hybrid platform to mitigate vibration of a batch of high-tech equipment installed in a building subject to nearby traffic-induced ground motion. A three-storey building model and a hybrid platform model are designed and manufactured. The hybrid platform is mounted on the building floor through passive mounts composed of leaf springs and oil dampers and controlled actively by an electromagnetic actuator with velocity feedback control strategy. The passive mounts are designed in such a way that the stiffness and damping ratio of the platform can be changed. A series of shaking table tests are then performed on the building model without the platform, with the passive platform of different parameters, and with the hybrid platform. The experimental results demonstrate that the hybrid platform is very effective in reducing the velocity response of a batch of high-tech equipment in the building subject to nearby traffic-induced ground motion if dynamic properties of the platform and control feedback gain are selected appropriately. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Hybrid platform for vibration control of high-tech equipment in buildings subject to ground motion.

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2003
Part 2: analysis
Abstract The experimental results of using a hybrid platform to mitigate vibration of a batch of high-tech equipment installed in a building subject to nearby traffic-induced ground motion have been presented and discussed in the companion paper. Based on the identified dynamic properties of both the building and the platform, this paper first establishes an analytical model for hybrid control of the building-platform system subject to ground motion in terms of the absolute co-ordinate to facilitate the absolute velocity feedback control strategy used in the experiment. The traffic-induced ground motion used in the experiment is then employed as input to the analytical model to compute the dynamic response of the building-platform system. The computed results are compared with the measured results, and the comparison is found to be satisfactory. Based on the verified analytical model, coupling effects between the building and platform are then investigated. A parametric study is finally conducted to further assess the performance of both passive and hybrid platforms at microvibration level. The analytical study shows that the dynamic interaction between the building and platform should be taken into consideration. The hybrid control is effective in reducing both velocity response and drift of the platform/high-tech equipment at microvibration level with reasonable control force. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Using the Aggregation of Latex Polymers in the Fabrication of Reproducible Enzyme Electrodes

ELECTROANALYSIS, Issue 17 2003
Wibowo Rahmat
Abstract An enzyme electrode for glucose is described as a model system to demonstrate a fabrication method using latex aggregation and entrapment of enzyme. Electrosterically-stabilized latex particles synthesized by emulsion polymerization in batch from acrylic acid, methyl methacrylate and butyl acrylate, and glucose oxidase were coagulated together at pH,5.5 with ethanol. A platinum disk electrode dipped in the solution becomes coated with latex/enzyme. The relative thickness of the film and relative amount of enzyme may be controlled by the time the electrode is in contact with the solution. The enzyme was then immobilized by covalent attachment of amine groups to carboxylic moieties in the polymer using 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride and N -hydroxysuccinimide. Five minutes contact with the latex/enzyme solution and subsequent amide coupling, gave electrodes with a reproducibility of 5.7% RSD, a wide dynamic range (0,100,mM) and good storage properties. [source]

Parameters governing reproducibility of flow properties of porous monoliths photopatterned within microfluidic channels

ELECTROPHORESIS, Issue 14 2010
Mei He
Abstract We report the patternability as well as the reproducibility and stability of flow resistance of polymer monolithic beds photopatterned within microfluidic channels as a function of initial reagent composition and preparation conditions. 2-Hydroxyethyl methacrylate and ethylene dimethacrylate-based polymer monoliths were selectively photopatterned within microchannels and their flow resistance was evaluated using a photobleaching, TOF linear flow rate measurement method developed in our lab. This measurement technique was found to be significantly more informative for columns formed in microfluidic channels compared with bulk monolith characterization by mercury intrusion porosimetry. 1-Octanol was determined to provide sharp bed edge formation and relatively low flow resistance by photopatterning relative to other porogenic solvents. Compared with literature formulations which did not achieve good flow stability and reproducibility from batch to batch, using 2-hydroxyethyl methacrylate, ethylene dimethacrylate and 1-octanol as porogenic solvents, less than 4% RSD was achieved in flow stability over 7 days for monoliths prepared with 60,80% crosslinker(monomer+crosslinker) ratio. Column-to-column variation of 5% RSD was obtained in this composition range. These results demonstrate that photopatterning of uniform polymer monolithic beds, which is critical for applications in multiplexed microfluidic systems, requires careful attention to the parameters that affect reproducibility, specifically the porogenic solvent choice and the crosslinker to monomer ratio. [source]

Biosensor online control of citric acid production from glucose by Yarrowia lipolytica using semicontinuous fermentation

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2010
Lucie Moeller
Abstract Our study aimed at the development of an effective method for citric acid production from glucose by use of the yeast Yarrowia lipolytica. The new method included an automated bioprocess control using a glucose biosensor. Several fermentation methodologies including batch, fed-batch, repeated batch and repeated fed-batch cultivation were tested. The best results were achieved during repeated fed-batch cultivation: Within 3 days of cycle duration, approximately 100,g/L citric acid were produced. The yields reached values between 0.51 and 0.65,g/g and the selectivity of the bioprocess for citric acid was as high as 94%. Due to the elongation of the production phase of the bioprocess with growth-decoupled citric acid production, and by operating the fermentation in cycles, an increase in citric acid production of 32% was achieved compared with simple batch fermentation. [source]

Dynamics of Benzene and Toluene Degradation in Pseudomonas putida F1 in the Presence of the Alternative Substrate Succinate

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2007
I. Rüegg
Abstract In batch and continuous culture, the regulation of benzene and toluene degradation by Pseudomonas putida,F1 was investigated in the presence of the alternative carbon and energy source succinate. In batch culture, benzene and toluene were used simultaneously, whereas succinate suppressed benzene consumption under carbon excess conditions resulting in diauxic growth. In carbon-limited continuous culture mixed substrate growth was observed. Since in nature low substrate concentrations and ever changing conditions prevail, this paper focuses on the dynamics of benzene/toluene degradation, biomass synthesis, and the regulation of benzene/toluene-degrading enzymes in cultures growing continuously at a dilution rate of 0.1,h,1, when shifting the supply of the carbon and energy source from succinate to various mixtures of succinate and benzene/toluene, or to benzene only. When the succinate concentration was kept constant (1.25,mM) and the medium was supplemented with benzene (2,mM), growth with benzene began already two hours after the shift. In contrast, replacing succinate with benzene only led to a wash out of biomass for more then ten hours, before biomass production from benzene started. A striking and reproducible transition pattern was observed for all shifts where the succinate concentration was reduced or succinate was omitted. After an initial period of biomass production from benzene, the culture collapsed and a wash-out of biomass was observed. However, this wash-out was not accompanied by an increase in benzene in the cultivation liquid, indicating a benzene uptake without conversion into biomass. Another possibility is that in phases of low biomass concentrations, cells were only able to use the low amounts of benzene/toluene dissolved in the cultivation liquid yielding low biomass concentrations whereas in phases of high biomass concentrations, they were able to rapidly utilize the aromatic solvents so that additional benzene from the gas phase diffused into the cultivation liquid resulting in more biomass production. In most cases, growth resumed again after 10 to 80,h. Currently, the reasons for the decrease in biomass after the first rise are unknown. However, several indications rule out intoxication of the cells by either the solvents benzene or toluene themselves, or by toxic degradation intermediates, or by-products. [source]

Subsurface addition emission model

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2005
Allen Hatfield PhD
Subsurface addition is commonly used in the chemical industry as a means of ensuring that the incoming reagent is distributed uniformly within a batch as the addition proceeds. The difference between subsurface addition and the typical above-surface addition is in how the inlet liquid stream enters the vessel. When calculating the process vent emissions for an above-surface addition one considers the partial pressure of the inlet stream components along with the batch components. This is because both mixtures have direct exposure to the vessel headspace during the addition process. For subsurface addition, volatile compounds that are contained in the inlet stream are exposed to the headspace only as they appear in the batch during the addition process. The purpose of this paper is to present a model for estimating the vent emissions for subsurface addition processes based on the integrated average liquid-phase composition. © 2004 American Institute of Chemical Engineers Environ Prog, 2004 [source]

A novel reactor for exploring the effect of water content on biofilter degradation rates

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2003
Milinda A. Ranasinghe
A novel batch recycle reactor was developed to investigate the effect of water content changes on the biological degradation rate of gas phase contaminants in low water content systems, such as biofilters. The reactor tightly controlled the water content of the unsaturated packing material using the principle of a suction cell. Matric potential in the compost was controlled between ,6 and ,36 cm H2O. A soil water retention curve relating matric potential to gravimetric water content was generated for the compost. Periodic dry weight analyses of reactor samples, together with the water retention curve, verified moisture content control. Runs were performed with toluene as the contaminant using unamended compost at a constant temperature of 30°C. Degradation results indicated a linear, biologically limited degradation region, followed by a non-linear region at lower concentrations. Elimination capacities were calculated for the linear region for different matric potentials along both the wetting and drying curves, and both changes in the water content and direction of approach affected the removal rates in the linear region. The elimination capacity ranged from 155 g/m3 hr to 24 g/m3 hr for toluene over the matric potential range investigated. Repeatability studies indicated that moisture content was most likely the parameter that influenced changes in performance. [source]

Comparison of biodegradation kinetic parameters for naphthalene in batch and sand column systems by pseudomonas putida

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2001
Jeong-Hun Park
Kinetic parameters for the degradation of naphthalene by Pseudomonas putida ( ATCC 17484) were estimated in both batch and column assays, in order to evaluate the role of flow and cell attachment on biodegradation rates. Suspended cells and cells attached to Ottawa sand were used under a variety of biomass levels, column flow-rates, and substrate concentrations. In batch systems, degradation followed zero order kinetics across the entire concentration range, while the columns exhibited decreased rates at concentrations less than 100 (,g/L), describable by Michaelis-Menten kinetics. This is reflected in elevated values of the half-saturation constant, Ks, in columns. We offer the explanation that this may have resulted from reactive heterogeneity within the porous media, imposing a distribution of length-scales for transfer of substrate to the cell surfaces. Well-mixed batch systems are expected to have both shorter and more uniform transfer distances. When kinetic parameters obtained in batch system are used for prediction of degradation in columns, at least two factors,exposed reduction of exposed cell surface are a and heterogeneity of cell distribution,will likely reduce overall column degradation rates. [source]

Alternatives to VOC and toxic solvents in batch loaded cold cleaning

ENVIRONMENTAL QUALITY MANAGEMENT, Issue 1 2002
Mike Morris
First page of article [source]

Characteristics of microcystin production in the cell cycle of Microcystis viridis

ENVIRONMENTAL TOXICOLOGY, Issue 1 2004
Keishi Kameyama
Abstract The correlation between the content of three microcystins (types LR, RR and YR) and the cell cycle of an axenic strain of Microcystis viridis, NIES-102, was investigated under conditions of high (16 mg L,1) and low (1.0 mg L,1) nitrate (NO3 -N) concentrations. Each phase of the cell cycle was identified using a flow cytometer equipped with a 488-nm argon laser using SYTOX Green dye, which binds specifically to nucleic acids and can be exited by the wavelength (Ex/Em: 504/523 nm on DNA). Microcystin concentration showed a positive linear correlation with DNA concentration. The microcystin content of the cells changed remarkably as the cell cycle process proceeded, with maximum content in the G2/M phase and minimum content in the G0/G1 phase. Under a condition of high NO3 -N concentration, the ratio of the total content in the G0/G1 phase to that in the G2/M phase was about 6:1. In contrast, for the two batch cultures the total content was 1.3-fold greater in the G2/M phase. The compositions of the three microcystins also changed along with the cell cycle process, although there was little difference in composition that was related to NO3 -N concentration. Therefore, there were distinctive compositions specific to each phase of the cycle, and the cell cycle of the M. viridis strain was more strongly responsible for both the quantity and the types of microcystin production than was the effect of NO3 -N concentration. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 20,25, 2004. [source]