bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting Temperature vs Time Behavior During the Freezing and Thawing of Rectangular Foods
Authors: Reinick Amelia Rubiolo De , Schwartzberg Henry 
Published: December 2008

AbstractBased on the effective heat capacity characteristics of biological materials during freezing we have derived a short‐cut equation for predicting their temperature vs time behavior during freezing and thawing. The equation can be used in the low Biot number range for rectangular bodies with similar or dissimilar heat‐transfer coefficients at their different surfaces. It has been experimentally and numerically tested for rectangular blocks of chopped beef with two or four exposed sides for Biot numbers ranging between 0 and 3. In this range it predicts temperature vs time behavior with errors of less than 5 to 10% in terms of overall processing time. By using numerical methods, the approach used can be extended to handle problems involving time‐varying boundary conditions and many types of non‐linear, physical‐property behavior.
Cellular Electrode for Antitumor Drug Screening
Authors: Liang Bernard S. , Li Xiang‐Ming , Wang Henry Y. 
Published: December 2008

AbstractMouse leukemia L1210, a well established tumor model, can be immobilized near the surface of a dissolved O2 probe and its O2 uptake can be monitored continuously following the addition of various chemicals such as Mechlorethamine HCl, an antitumor agent. The output current of the O2 electrode changed as a function of time under various experimental conditions. The dynamic response of the electrochemical sensor was determined as a function of antitumor agent concentration. A preliminary kinetic model was developed to describe the biosensor behavior.
Experimental Device and Methods for Studying Milk Deposit Formation on Heat Exchange Surfaces
Authors: Tissier J. P. , Lalande M. 
Published: December 2008

AbstractAn experimental mini‐heat‐exchanger was developed in our laboratory.It can be inserted between the heating and holding sections of a pilot milk pasteurizer without modifying its temperature gradient. Representative soil samples from both heating and holding sections were obtained. Changes in soil composition according to running time were studied over a range of 1 min to 4 hours. Previously cleaned 0.4 mm thick stainless steel plates (304L) had to be cut into pieces before analysis. Different kinds of results were obtained. Scanning electron microscopy showed that the deposit was composed of two different types of soil. A dense deposit could be observed near the metal surface after only 1 min of treatment; the thickness of this deposit increased to 15 μm during the process. Over this layer, a spongy deposit only slightly bound to the former, could be observed Lightly fouled plates were analyzed by “in situ techniques” (X.P.S.)Thick deposits were embedded and sectioned for transmission electron microscopy and histochemical analyses.A microanalytical method was applied to deposits after removal and resulted in detection ranges exceeding 10 mg/cm2.
Purification of Proteins and the Disruption of Microbial Cells
Authors: Kula Maria‐Regina , Schütte Horst 
Published: December 2008

AbstractIntracellular proteins with catalytic or biological activity are of growing importance for developments in enzyme technology, as well as for the production of mammalian proteins by recombinant‐DNA technology. The release of these proteins from microorganisms is an important unit operation, as it is the first step in their isolation.Gram‐scale disruption of microorganisms can be performed by a variety of established methods based on chemical, enzymatic, physical, or mechanical principles. For the large scale disruption of microorganisms, mechanical disintegrators, such as high‐speed agitator bead mills or high‐pressure industrial homogenizers, are commonly employed. Both types of equipment were designed originally for other tasks; in the paint industry or in the milk industry, respectively. Therefore, it appeared necessary and possible to improve design and performance for the application in cell disintegration. The goal is a uniform exposure of the microbial cells and a minimal exposure of solubilized protein to high shear forces, in order to obtain high yields and to avoid the generation of too small cell wall fragments, which are difficult to separate.Both types of machines have been investigated for the disintegration of different microbial cells and the influence of the operating parameters analyzed on protein solubilization and enzyme yield. We will summarize the state of the art and discuss new data to illustrate trends in process development.
Purification of Monoclonal Antibodies from Large‐Scale Mammalian Cell Culture Perfusion Systems
Authors: Scott Randy W. , Duffy Stephen A. , Moellering Bill J. , Prior Christopher 
Published: December 2008

AbstractMethodology for the purification of monoclonal antibodies from large‐scale mammalian cell culture systems has been investigated. The concentration of monoclonal antibodies in conditioned cell culture media was generally found to be in the milligram per liter range, requiring 100–1,000 liters for production of gram quantities. To reduce the volumes, several ultrafiltration systems, including hollow fiber, plate, and frame, and spiral cartridges were investigated and found to be effective for large‐scale work. Once a concentrated product was obtained, several methods including ammonium sulfate precipitation, ion exchange, protein. A agarose, and size exclusion chromatograhy were utilized and compared. The best results were obtained when concentrated conditioned medium was either diluted or diafiltered (to reduce the high ionic strength of conditioned medium) and fractionated by cation exchange chromatography. Variations in isoelectric points for different monoclonal antibodies require that specific pH and ionic strength parameters be determined to optimize binding and elution. Additional purification was achieved by further ion exchange steps or the use of ammonium sulfate precipitation. For particularly difficult purifications, protein A affinity chromatography was used. Once a purity of 90–95% was achieved, size exclusion chromatography was used as a final step to remove aggregates, process chemicals, contaminant proteins, and to exchange the antibody into the formulation buffer.
An Analysis of Intra‐Versus Extracapillary Growth In a Hollow Fiber Reactor
Authors: Adema E. , Sinskey A. J. 
Published: December 2008

AbstractMammalian cell culture in hollow fiber reactors is hampered by oxygen limitation. Diffusive oxygen transport from the fiber wall to the cells can be enhanced by increasing the surface area for oxygenation and/or decreasing the penetration depth. One strategy for improving of surface area to penetration depth ratio is to increase the number of fibers in the reactor. An alternative way to manipulate this ratio is to grow the cells inside the fibers rather than on the outside. The theoretical analysis presented indicates that this is favorable when the volume of the extracapillary space exceeds that of the fiber lumen by a factor four or more. The impact of growing the cells on the inside of the fibers on other aspects of mammalian cell culture in hollow fiber reactors, including mass transport from the bulk of the medium flowing through the reactor to the fiber wall, is discussed.
Analysis of Urea Hydrolysis by Immobilized Urease in Urea‐Sensing Electrodes
Authors: Moynihan H. J. , Wang N.‐H. L. 
Published: December 2008

AbstractUrea hydrolysis in an enzyme electrode that is sensitive to urea concentration has been analyzed with a theoretical model. The model incorporates nonlinear product‐inhibited, pH‐dependent kinetics, Nernst‐Planck diffusion, and ionic equilibria of product and buffer species. Simulation results indicate that film resistance can significantly reduce the detection range of the electrode and a Biot number (the ratio of characteristic internal to external mass transfer resistance) greater than 75 is necessary to minimize the film resistance. The electrode response depends on a balance between the reaction‐generated pH changes and the membrane diffusion resistances that sustain such pH shifts. The Damkohler number (the ratio of characteristic rate of reaction to that of diffusion) should be between one and five to maximize electrode sensitivity. The model has been used to demonstrate the effects of acetate, phosphate, and Tris buffers on electrode response. The carbonate concentration of dialysate solution is sufficient to shift the detection range of the electrode and reduce the sensitivity of the electrode by an order of magnitude. Tris buffer reduces the pH response of the electrode for buffer concentrations greater than 2 mM, because the pK of Tris falls within the range of the reaction‐generated pH shift.
Effective Diffusion Coefficients in Calcium Alginate Gel
Authors: Itamunoala G. F. 
Published: December 2008

AbstractThe effective diffusion coefficient of glucose, De in calcium alginate gel determined at 35°C by two different methods gave values which, on average, were at least 24% less than in water. Assessment of the effect of glucose concentration on De seems to indicate that De increased with decreasing glucose concentration at very low concentrations (i.e., < =100 mM) and increased with increasing glucose concentrations at high concentrations (i.e., > =200 mM). Increasing the concentration of either the calcium chloride or sodium alginate component used in calcium alginate formation substantially decreased De, but the effect of sodium alginate was the greater of the two.
The Effect of Detergent Level and Dispersion Rheology on the Olefin Yield from Fractionation of Tallow
Authors: Glassner David A. , Grulke Eric A. 
Published: December 2008

AbstractOptimization of the detergent fractionation of tallow to maximize olein yield depends on selecting the correct detergency and rheological properties of the aqueous dispersion. The efficiency of the separation is related to the apparent viscosity of the mixture. The apparent viscosity of the dispersion as determined in a paddle mixer viscometer decreased from .3 Pa‐s to .1 Pa‐s as the olein yield increased from 66% to 79%.
Improvements In Multi‐Turbine Mass Transfer Models
Authors: Bader Fredric G. 
Published: December 2008

AbstractMathematical modeling approaches are being developed to better understand and describe the overall performance of large‐scale agitated fermentors. These new approaches are based upon subdividing the fermentor into various mixing cells, or stages. The further development of these models requires information on the power input per stage, its effect on mass transfer within the stage, fluid mixing patterns between stages, and the distribution of gas in the fermentor stages. The following discussion presents data and comments related to these topics for aerobic fermentations of low to medium viscosity.
A Simulation of the Effects of Formula Variations on the Transient Output of Single Screw Food Extruders
Authors: Levine Leon , Symes Steven , Weimer John 
Published: December 2008

AbstractA simulation of the transient response of single screw extruders to fluctuations in formula of the extrudate is described. Any changes in extrudate composition, which result in changes in the viscous properties of the extrudate, result in transient behavior in the output of an extruder. Using existing extruder models, a simulation was used to study the transient behavior of an extruder in response to compositional variations in the extrudate. The results of the simulation suggest that for small variations in the composition of the material being extruded, large transient responses in extruder output will be observed. Depending on the relationship between the composition and viscosity of the extrudate, the change in output of the extruder can vary between insignificance and virtual stoppage of flow. The implications of these extruder transients on the design and operation of extrusion systems are discussed.
A Simulation of the Effect of Formula and Feed Rate Variations on the Transient Behavior of Starved Extrusion Screws
Authors: Levine Leon , Symes Steven , Weimer John 
Published: December 2008

AbstractUsing simulation, the steady state performance and transient behavior of starved extrusion screws are described. At steady state the filled length of the extruder is controlled by the relative resistance of the screw and die to flow, the flow index of the extrudate, and the feed rate to the extruder. For transient situations, small variations in the composition or feed rate of the material being extruded can significantly alter the extruder's output and filled length. Because of the broader residence time distribution of a twin screw extruder compared to a single screw extruder, the magnitude of the transient effects are seen to be smaller for twin screw extruders. The predicted output transients for extruders operated in the starved condition are of significantly lower magnitude than that for extruders operated in a filled condition. The implications of these effects on the design and operation of extrusion systems are discussed.
Use of Orthogonal Collocation Approximation for Parameter Identification and Control Optimization of a Distributed Parameter Biological Reactor
Authors: Isaacs S. , Thoma M. , Munack A. 
Published: December 2008

AbstractThe orthogonal collocation method of approximation is applied to the differential equations describing the oxygen concentration profiles in the liquid and gas phases of the tower loop airlift reactor. This provides a relatively quick simulation method that can be used for the parameter identification and control optimization tasks of the Open Loop Feedback Optimal (OLFO) adaptive control algorithm. Results of simulated cell mass fermentations are compared to that of a slower, more accurate finite difference simulation method showing the effects of collocation order on approximation accuracy and computation time. An example of parameter identification of the spatially dependent oxygen mass transfer coefficient and the overall growth rate is provided. Also, an example is included showing the optimization of air feed rate policy over the course of a fermentation.
Cooperative Binding of Sucrose in Xanthan Gum Solutions
Authors: Torrestiana Beatriz , Galindo Enrique , Brito Edmundo 
Published: December 2008

AbstractIn the xanthan gum fermentation mass transfer mechanisms are complex due to the high viscosity of the broth. Diffusional mass transfer becomes very important in transport of solutes such as oxygen and sucrose in the polysaccharide solution. Nevertheless, this process can be affected by interactions between macromolecule and solute. The present study was designed to determine if xanthan gum interacts with sucrose. The data show that xanthan gum in solution possesses two interaction sites for sucrose. These interactions are adequately described by a cooperative binding model. Changes in ionic strength and pH did not affect either the number of sites or type of interaction.
Review of Liquid Mixing in Packed Bed Biological Reactors
Authors: Swaine Donald E. , Daugulis Andrew J. 
Published: December 2008

AbstractThe use of residence time distribution analysis to characterize the liquid phase hydrodynamics in bioreactors is reviewed, with special emphasis on packed bed bioreactors. The importance of tracer selection, the method of data analysis and other uses for the data collected in RTD measurements are discussed.
Bioproduct Recovery From Unclarified Broths and Homogenates Using Immobilized Adsorbents
Authors: Nigam Somesh C. , Sakoda Akiyoshi , Wang Henry Y. 
Published: December 2008

AbstractThe use of reversibly “immobilized” (gel‐matrix entrapped or gel‐membrane encapsulated) adsorbents for the recovery of protein products from unclarified broths or cell homogenates containing difficult to remove solids was investigated. The hydrogel membrane or matrix acts as a protective non‐fouling barrier that allows the diffusion of the desired bioproduct, but it excludes colloidal solids such as whole cells, cell debris, and macromolecular precipitates. This feature not only prevents the fouling of the adsorbent, it also enhances product separation. The concept of kinetic selectivity, which depends on the differences in the diffusion rates of various adsorbing species is also introduced. The utility of hydrogel matrix or membrane in enhancing the kinetic selectivity of smaller proteins from a crude mixture was also investigated using model systems.
NMR Spectroscopy Studies of Hybridoma Metabolism in a Simple Membrane Reactor
Authors: Fernandez Erik J. , Mancuso Anthony , Clark Douglas S. 
Published: December 2008

AbstractNuclear magnetic resonance (NMR) was used to examine the metabolism of hybridoma cells in a simple immobilized‐cell membrane reactor. Although the reactor was not suitable for maintaining viable cells over extended periods, several types of experiments were performed. Phosphorylated and carbonaceous metabolites were observed on‐line with 31P and 13C NMR. Complementary information about glutamine metabolism was provided by 15N NMR spectra of concentrated supernatants. Extracellular contributions to NMR spectra were measured in a second vessel containing only medium. 3IP NMR measurements demonstrated that the perfused cells were stable to changes in the concentration of dissolved oxygen and to a brief interruption in medium recirculation. In tracer experiments utilizing [I‐13C]D‐glucose as a substrate, lactate and alanine were detected in vivo, along with some as of yet unassigned compounds. When cells were exposed to a high initial concentration of [I‐13C]D‐glucose, lactate and alanine appeared immediately and attained their maximum recorded levels at similar times. When cells were subjected to a step change in the glucose concentration from 2–10 mM, intracellular lactate and nucleoside triphosphates (NTP) increased sharply, but alanine formation was not evident until nearly five hours later. In both cases, the intracellular concentrations of labeled lactate and alanine were estimated directly from the 13C NMR spectra.
Formulation and Characterization of a Multiple Emulsion for Use as a Red Blood Cell Substitute
Authors: Borwanker C. M. , Pfeiffer S. B. , Zheng S. , Beissinger R. L. , Wasan D. T. , Sehgal L. R. , Rosen A. L. 
Published: December 2008

AbstractA new approach to the development of an oxygen‐carrying blood substitute is presented. The development of a viable blood substitute in the form of a multiple emulsion encapsulating hemoglobin solution was explored. Results indicated that the formulation ingredients and procedure affect the properties of the multiple emulsion. In order to evaluate the different formulations a quantitative method of assessing the encapsulation efficiency (yield) of the multiple emulsions was developed. The yield test measures the amount of hemoglobin released into the external phase. A model mutiple emulsion was formulated and characterized by yield, drop size distribution, oxygen‐carrying capacity, oxyhemoglobin dissociation, short‐term storage stability, and viscosity. The yield obtained for the model formulation was excellent (greater than 90%) giving high oxygen‐carrying capacity. The high yield was maintained over a four day storage period at 4d̀C.
Endothelial Volume and the Hydraulic Conductivity of Microvessels During Altered Pressure States
Authors: Easterbrook M. H. , Gross J. F. , Intaglietta M. 
Published: December 2008

AbstractLow perfusion states of the microcirculation are known to produce endothelial cell swelling. In our study, irreversible thermodynamic transport equations are used to model the exchange of fluid between endothelial cells and the blood and tissue compartments. Results indicate that changes in the capillary hydrostatic pressure result in negligible radius changes, due to the small contribution of this pressure to the total pressure when the osmotic pressures of all species present are taken into account. Alterations in osmotic pressure via adjustment of the NaCl concentration in the blood produce fast and substantial changes in radius and therefore hydraulic resistance.
Reaction Rates for the Production of Polyphenylalanine and Polyserine by Solid Phase Peptide Synthesis with Low Excesses of the Symmetrical Anhydride
Authors: Chen Wen‐Yih , Foutch Gary L. 
Published: December 2008

AbstractContinuous monitoring with UV‐absorbance was used to obtain coupling reaction rates between t‐Boc amino symmetrical anhydrides and the amino terminus of the peptide by solid phase synthesis. A kinetic model was established for the synthesis of polyserine and polyphenylalanine with rate constants determined over selected reaction temperatures, mixing rates, peptide chain lengths, and excess mole ratios of t‐Boc amino acid.
Effects of Growth Conditions on Carbon Utilization and Organic By‐Product Formation in B. subtilis
Authors: Snay J. , Jeong J. W. , Ataai M. M. 
Published: December 2008

AbstractThe effects of growth rate and substrate concentration on cellular metabolism of glucose was studied with cultures of B. subtilis 168. Application of chemostat culture techniques allowed for the observation of each growth condition independent of the other. The relative flux of carbon through biosynthetic and non‐biosynthetic pathways was determined by monitoring cell density and distribution of extracellular side products in active cultures. A metabolic shift of glucose utilization pathways was observed in cell cultures grown at dilution rates greater than 0.36 hr−1 or with glucose feed levels exceeding 10 gll. The predominant side products detected by HPLC analysis were acetic acid, formic acid, lactic acid, and acetoin. The patterns of side product formation were analyzed in relation to the applied growth conditions.
Adsorption Phenomena in Hydrophobic Interaction Chromatography
Authors: Roettger Belinda F. , Myers Julia A. , Ladisch Michael R. , Regnier Fred E. 
Published: December 2008

AbstractHydrophobic interaction chromatography (HIC) separates proteins on the basis of surface hydrophobicity while generally retaining the activity of proteins. Aqueous mobile phases with high salt concentrations are often used to adsorb the proteins onto a mildly hydrophobic support. HIC protein adsorption is modeled using the thermodynamic theory of linked functions (i.e., Wyman's linkage theory). This approach correlates adsorption to preferential interactions of the salts with supports and proteins. Two different methods were employed to study the salt interactions with the support: chromatography retention studies and densimetric techniques. Results of the salt chromatography trials indicate that chaotropic salts such as NaSCN and NaI have positive preferential interaction parameters that decrease with increasing concentration. Densimetric measurements show that the preferential interaction parameters of polar kosmotropic salts, such as ammonium sulfate are negative and become more negative with increasing concentration. The correlation of HIC adsorption to preferential interaction parameters was experimentally verified by retention studies of lysozyme in aqueous chaotropic and kosmotropic mobile phases, which also show a linear relation between the protein's capacity factor and the lyotropic series.