bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface characterization of hydrophilic coating obtained by low‐pressure CH4O2 plasma treatment on a polypropylene film
Authors: López R. , Sanchis R. , García D. , Fenollar O. , Balart R. 
Published: December 2008

AbstractThe use of surface treatments at industrial level is generalized as they allow obtaining a wide variety of properties such as soft in the touch, hydrophilic behavior, and biocompatibility. The use of low‐pressure plasma techniques with organic gases or organic mixtures is an easy way to obtain surface coatings very small in depth through plasma‐polymerization processes that can be assimilated to a plasma‐enhanced chemical vapor deposition (PECVD) process. In this work, we have carried out a plasma‐polymerization process on a polypropylene (PP) film to obtain a hydrophilic coating. To obtain this, the film surface has been treated on a low‐pressure plasma reactor with a methane–oxygen mixture gas with a volume ratio of 80 : 20, respectively. The chemistry changes in the outermost layers of the deposited coating have been investigated with X‐ray photoelectron spectroscopy (XPS). The different processes that take part as a consequence of the interaction between the plasma gas species and the PP film surface mainly drive to the deposition of an organic layer, which is functionalized with oxygen‐based species as XPS study reveals. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Isothermal crystallization kinetics of high‐flow nylon 6 by differential scanning calorimetry
Authors: Zhang Fan , Zhou Li , Xiong Yuanqin , Liu Guangpeng , Xu Weijian 
Published: December 2008

AbstractThe isothermal crystallization kinetics have been investigated with differential scanning calorimetry for high‐flow nylon 6, which was prepared with the mother salt of polyamidoamine dendrimers and p‐phthalic acid, an end‐capping agent, and ε‐caprolactam by in situ polymerization. The Avrami equation has been adopted to study the crystallization kinetics. In comparison with pure nylon 6, the high‐flow nylon 6 has a lower crystallization rate, which varies with the generation and content of polyamidoamine units in the nylon 6 matrix. The traditional analysis indicates that the values of the Avrami parameters calculated from the half‐time of crystallization might be more in agreement with the actual crystallization mechanism than the parameters determined from the Avrami plots. The Avrami exponents of the high‐flow nylon 6 range from 2.1 to 2.4, and this means that the crystallization of the high‐flow nylon 6 is a two‐dimensional growth process. The activation energies of the high‐flow nylon 6, which were determined by the Arrhenius method, range from −293 to −382 kJ/mol. The activation energies decrease with the increase in the generation of polyamidoamine units but increase with the increase in the content of polyamidoamine units in the nylon 6 matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Unsteady Cell Distributions in Capillary Networks
Authors: Furman M. B. , Olbricht W. L. 
Published: December 2008

AbstractA numerical simulation is used to study the distribution and flux of red blood cells in capillary networks. The relationship between the motion of an individual cell in a single capillary and the overall transport of cells throughout a network is investigated.Interpretation of results is greatly facilitated by the use of a computer graphics representation of the simulation. Steady‐state and certain time‐dependent cell distribution problems are studied, with a special focus on the sensitivity of the results to the presence of a small number of white cells.
Background Studies in the Modeling of Extrusion Cooking Processes for Soy Flour Doughs
Authors: Luxenburg L. A. , Baird D. G. , Joseph E. G. 
Published: December 2008

AbstractSoy flour is processed in single screw extruders to yield textured vegetable protein used as meat extenders and replacements. The fundamental processes which take place in extrusion cooking of soy doughs are poorly understood from an engineering point of view. This paper is concerned with gaining an understanding of extrusion cooking in order to develop a quantitative model of this process in single screw extruders. Rheological and thermodynamic data are obtained over a range of conditions found in the extrusion process and this data is used both in understanding and modeling the extrusion cooking process.In particular, differential scanning calorimetry (DSC) has been used to determine changes in the enthalpy of soy doughs at various moisture levels. It is observed that in general the enthalpy changes are small (e.g. of the order of 1.0 cal/g) and endothermic. However, if the dough is subjected to shear and thermal history, then the enthalpy changes become significant. The viscosity of the dough exhibits a mild increase in the temperature range where the endotherms are observed in the DSC data. Based on the results of this study, it is concluded that cooking does not involve cross‐linking of the proteins but more likely a conformation change of the molecules. Also, it is found that for the 40% to 60% added moisture soy flour dough systems, the rheological properties can be modeled using a Bingham model modified with a shear rate dependent viscosity.
Rate of Precipitation of Calcium Phosphate On Heated Surfaces
Authors: Barton Kathleen P. , Chapman Thomas W. , Lund Daryl 
Published: December 2008

AbstractFouling of a heated stainless steel surface by calcium phosphate precipitation has been studied in an annular flow apparatus, instrumented to provide a constant heat flux while measuring local metal‐surface temperatures. Models of the heat and mass‐transfer boundary layers are used to estimate interfacial temperatures and concentrations, from which the heterogeneous reaction rate is inferred. The analysis indicates that the reaction rate is a function of both chemical kinetics and mass transfer limitations.
Kinetics of Gel Forming in Enzyme Coagulated Milk
Authors: Carlson Alfred 
Published: December 2008

AbstractA semi‐empirical kinetic model has been developed to explain the observed kinetics of gel formation in enzyme coagulated milk. The kinetic model assumes that the actual system can be represented by a two‐step reaction in series model in which both reactions are first order.The initial reaction is the formation of potential cross‐link points corresponding to the hydrolysis of K‐casein which covers the surface of casein micelles. The second reaction is the formation of cross‐links between casein micelles as individual micelles interact with each other. The initial reaction is dependent on the concentration of enzyme in the solution, while the second reaction is enzyme independent. The formation of increasing numbers of cross‐links results in an increase in the shear modulus of the gel. The model correctly predicts the general shape of the shear modulus vs. time curve, and faithfully accounts for the influence of enzyme concentration of the rate of shear modulus increase. It is also consistent with the influence of pH and temperature, and denaturation on the activity of the enzyme for the range of these values tested.
Small‐Angle Neutron Scattering Studies of Protein‐Reversed Micelle Complexes
Authors: Sheu E. , Göklen K. E. , Hatton T. A. , Chen S.‐H. 
Published: December 2008

AbstractEnzymes solubilized in organic solvents, hosted within the polar cores of surfactant aggregates, known as reversed micelles, provide many unique opportunities for new biocatalytic synthesis and protein separation processes. Small‐angle neutron scattering (SANS) studies have shown that insertion of the protein cytochrome‐c in the reversed micelle polar core causes a significant reapportioning of the surfactants and water between the filled and unfilled micelles, leading to an increase in overall size of the filled micelles relative to their empty counterparts. The simple shell and core model assuming single occupancy of the reversed micelles has significant limitations in interpreting data for high protein loadings, and points to the need for more detailed characterization of the protein‐reversed micelle interactions.
Selective Removal of H2S from Biogas by a Packed Silica Gel Adsorber Tower
Authors: Chou Tse‐Chuan , Lin Thong Yueh , Hwang Bing Joe , Wang Chung Cheng 
Published: December 2008

AbstractThe removal of hydrogen sulfide from biogas by silica gel was systematically studied. The results indicate that H2S could be selectively and completely removed from the biogas until the silica gel became saturated. When it became saturated, the color of silica gel changed from blue to black. The used silica gel could easily be regenerated and reused. The factors that affected the purification of biogas by silica gel were found to be the flow rate of biogas, the regeneration temperature, the degree of saturation of the silica gel, and the water content of silica gel. A mathematical model describing the operation of the adsorber was developed. The breakthrough curves and mass transfer coefficients of H2S were also obtained.
A Theoretical Examination of Adsorption Processes in Preparative Liquid Chromatography of Proteins
Authors: Regnier Fred E. , Mazsaroff István 
Published: December 2008

AbstractThis article examines retention in preparative chromatography in terms of the stoichiometric displacement model. This model is based on an equilibrium in which proteins and small displacing agents compete for ligands on the surface of chromatographic sorbents. Both the equilibrium constant for this process and the three‐dimensional structure of the macromolecule being separated are shown to be major determinants of retention in the analytical (linear) mode.A theoretical application of this model to preparative (nonlinear) separations shows a high probability that there will be perturbations of the chromatographic distribution coefficient. The activity coefficients of proteins, molecular orientation of proteins toward the sorbent surface, and adsorption kinetics are both load and sample dependent. In addition, displacement effects by other macromolecular species are predicted at high proteins concentrations. This theoretical analysis concludes that mathematical modeling of the retention process under nonlinear conditions will be more sample specific and require significantly more data on column operating conditions, interfering sample components, sample load, and the chemical nature of the stationary phase.
Electrophoretic Elution from Monoclonal Antibody Immunoadsorbents: A Theoretical and Experimental Investigation of Controlling Parameters
Authors: Olson William C. , Yarmush Martin L. 
Published: December 2008

AbstractAn experimental and theoretical investigation of the mechanism of electrophoretic elution is described. The rate of elution of bovine serum albumin from monoclonal antibody immunoadsorbents was observed to increase with increasing electric field, increasing fractional saturation, and decreasing height of the immunoadsorbent column. Slower elution rates were observed from immunoadsorbents possessing higher affinities and capacities. A reaction‐migration mechanism is proposed in which the packed bed is modeled as a continuous hydrogel and in which the electrical field causes antigen that has spontaneously dissociated to migrate through the column under conditions of bound‐free equilibrium. Good qualitative and quantitative agreement is obtained between experiment and the predictions of a numerical model. A membrane device suitable for large‐scale application of this technique is discussed.
Techniques for Estimating the Vapor‐Liquid Equilibrium of Sugar Solutions
Authors: Leschke Rudolph J. 
Published: December 2008

AbstractA number of options for the mathematical prediction of sugar solution boiling points and corresponding equilibrium pressures and concentrations have been examined. Existing methods for this purpose have been found inadequate in that they can predict equilibrium conditions accurately only over a small concentration range, and usually only for pure sucrose solutions. Simple statistical techniques either fit such data poorly, or result in equations that are unreliable when extended beyond the concentrations or pressures over which the data were fit. In this work, general thermodynamically consistent equations have been applied to the prediction of boiling points of pure sucrose solutions, corn syrup, or mixtures of the two; valid over the entire concentration range of soluble solids, and at varying pressures.
Polymer Dosage Considerations in Polyelectrolyte Precipitation of Protein
Authors: Clark K. M. , Glatz C. E. 
Published: December 2008

AbstractThe properties of aggregates formed by the precipitation of egg white proteins by carboxymethyl cellulose (CMC) were examined. Both the final level and the number of incremental additions of the polyelectrolyte were varied. The protein and lysozyme recoveries, particle zeta potential, and protein composition of the precipitate were found to vary with only the final CMC level. Particle size and size distributions were dependent on both the polymer dosage and manner of addition. Overdosed systems, or systems in which the CMC dosage exceeded that required for optimal total protein removal, produced the smallest particles, with size increasing as the number of incremental polymer additions increased. Optimally dosed systems produced the largest particles.
Improving the Acetone‐Butanol Fermentation Process With Liquid‐Liquid Extraction
Authors: Dadgar Ali M. , Foutch Gary L. 
Published: December 2008

AbstractThe design of Marlatt and Datta [1] was used to compare the design and economics for acetone‐butanol‐ethanol facilities. The process and economics include liquid‐liquid extraction and the required downstream modifications.
Bioconversion of D‐Xylose and Pretreated Oak Sawdust to Ethanol Using Clostridium Thermosacchrolyticum by Batch and Continuous Up‐Flow Reactors
Authors: Liu Hwai‐Shen , Hsu Hsien‐Wen , Sayler Gary S. 
Published: December 2008

AbstractBioconversions of lignocellulosic biomass, in particular sawdusts, into ethanol were investigated, first, acid hydrolyses by dilute sulfuric acids using 0.5, 1.0, and 2.0 weight percent were performed. The optimum hydrolysis condition was found to be 1% acid at 124°C and hydrolysis time 50 min. The total yields of sacchrification, primarily xylose, is 23.7 g which is obtained from 100 grams of sawdusts with a liter of dilute at the optimum condition.Second, fermentations of xylose into ethanol were investigated using Clostridium thermosacchrolyticum (ATCC 31925) by a batch reactor and by a continuous up‐flow cylindrical reactor. In a continuous up‐flow reactor, two modes of operation are studied; namely, cells immobilized on polystyrene chips (size 2.79 × 3.78 × 2.64 mm) and cells freely suspended in the flowing substrate stream. The flow rates investigated were 17.5, 29.5, and 51.2 ml/hr for immobilized case and 27.3, 42.2, 66.1, and 109 ml/hr for free suspension case. The maximum concentration of ethanol yield obtained from the initial concentration of 6 g/l xylose was 1.8 g/l by a batch reactor, which is equivalent 60% of the theoretical conversion of xylose by weight. If the dilution rate is less than 0.3 hr−1, the concentration of ethanol by the continuous up‐flow reactor for both cases approach the maximum of that by a batch reactor.Modellings of bioconversion kinetic parameters in Monod and Luedeking‐Piret formulas were also obtained. The specific growth rate for the microorganism in CM‐4 medium is found to be 0.43 hr−1.
Chitosan‐Alginate Complex Coacervate Capsules: Effects of Calcium Chloride, Plasticizers, and Polyelectrolytes on Mechanical Stability
Authors: Daly Mary M. , Knorr Dietrich 
Published: December 2008

AbstractA method has been developed to form capsules with liquid cores where permeability can be modified without sacrificing membrane strength. The capsule is formed by dropwise addition of a 3% chitosan (polycation) solution into a 0.75% alignate (polyanion) solution. The resultant capsule consists of a liquid chitosan core with a hard alginate coating. The addition of CaCl2 to chitosan and glucose to alginate increased capsule strength. The membranes formed were strong enough to require up to 100 Newton during uniaxial compression to burst a 6.4 mm diameter capsule.
Shear Stress Effects on Human T Cell Function
Authors: Chittur K. K. , Mcintire L. V. , Rich R. R. 
Published: December 2008

AbstractA modified Couette viscometer was used to study the effect of shear stresses on human T lymphocyte functions. Cell suspensions containing T cells, B cells, and monocytes were subjected to uniform shear stresses of 100 and 200 dynes/cm2 for 10 minutes. After stress exposure, the T cell response to the lectin phytohemagglutinin‐P (PHA‐P) was a strong function of the total cell concentration in culture. Stressed cells cultured with 0.5 μg/ml PHA‐P at an initial concentration of 1 × 106 cells/ml did not incorporate significant amounts of tritium‐labelled thymidine into their DNA. This inability to incorporate thymidine could be related to insignificant amounts of interleukin‐2 (IL2) detected in cell culture supernatants. A size analysis revealed that exposure to stress interfered with the ability of PHA‐P to induce cellular enlargement characteristic of an activation response. Fluorescence flow cytometric studies showed that the membrane depolarization response of cell suspensions to PHA‐P was significantly affected after exposure to shear stresses. In contrast, when shear stressed cells were cultured at lower cell densities of 0.5 × 106 and 0.25 × 106 cells/ml, the functional responses to PHA‐P were similar to those of controls. The data obtained suggest that controlled exposure to sublytic shear stresses results in alterations that can affect the proliferative response of the T cell population, and that these alterations are cell‐density dependent.
Large‐Scale Purification of Tissue‐Type Plasminogen Activator from Cultured Human Cells
Authors: Harakas Nikos K. , Schaumann Jon P. , Connolly Daniel T. , Wittwer Arthur J. , Olander Jitka V. , Feder Joseph 
Published: December 2008

AbstractPlasminogen activators of both urokinase‐type (u‐PA) and tissue‐type (t‐PA) have been found in conditioned medium of cultured human fibroblasts. To purify t‐PA, the total PA activity from hectoliter quantities of conditioned medium was first concentrated with about 10‐fold increase in specific activity via zinc chelate‐sepharose affinity chromatography. Three different methods were employed in an attempt to separate t‐PA from u‐PA: (a) concanavalin A‐sepharose affinity chromatography; (b) fibrin‐celite affinity chromatography; and (c) immunoaffinity chromatography using anti‐tPA monoclonal antibody immobilized on sepharose. Of the three methods, only the monoclonal antibody procedure effected complete separation of the two enzymes. t‐PA was subsequently purified to homogeneity using size exclusion, high performance liquid chromatography followed by p‐aminobenzamidine‐agarose affinity chromatography.
Scaling‐Up of Affinity Chromatography By Radial‐Flow Cartridges
Authors: Huang Stanley H. , Roy Sujeta , Hou Kenneth C. , Tsao George T. 
Published: December 2008

AbstractAlthough affinity chromatography is an efficient separation method, impediments to its large scale applications include difficulty in predicting column behavior after scaling‐up and lack of suitable solid matrix support for fast flow operations. The introduction of radial‐flow chromatography and a modified cellulose support has overcome the impediments. Radial chromatography has advantages in low pressure drop at fast flow rate and in linear scaling‐up. The performances of the cellulose support is studied by attaching two bioaffine ligands to it and observing the efficiency in enzyme purification. Application of a radial‐flow affinity cartridge to remove proteases in human plasma shows 70% efficiency after one‐pass treatment.
Ethephon Enhancement of Secondary Metabolite Synthesis in Plant Cell Cultures
Authors: Cho G. H. , Kim D. I. , Pedersen H. , Chin C‐K. 
Published: December 2008

AbstractAddition of an ethylene precursor, ethephon, was studied in plant‐cell‐suspension cultures of Coffea arabica and Thalictrum rugosum as an enhancer of secondary metabolite production. In both cases the compound was able to stimulate alkaloid production, even though the biochemical pathways are widely different. This suggests that ethephon, or more directly ethylene, may be valuable in increasing secondary metabolite levels in a variety of cell‐suspension culture systems.
Construction and Characterization of a Temperature‐Sensitive Expression System in Recombinant Yeast
Authors: Silva Nancy Anderson Da , Bailey James E. 
Published: December 2008

AbstractA temperature‐regulated system for the expression of cloned genes has been developed and studied in recombinant yeast. A temperature‐sensitive (ts) strain of Saccharomyces cerevisiae was constructed which, in conjunction with plasmid promoters controlled by the yeast galactose regulatory circuit, allows induction of cloned gene product synthesis by temperature‐shift. Induction of cloned gene expression by temperature‐shift in the ts strain was compared with induction by galactose addition in a non‐ts, but otherwise identical, strain. In batch fermentations at 35°C, the levels of product protein produced by temperature‐shift induction were comparable or better than those produced by galactose induction. However, higher levels were formed by galactose induction at the preferred growth temperature of 30°C. At either temperature, β‐galactosidase synthesis was greatest when the ts strain was cultivated in galactose‐containing medium. Continuous culture experiments were performed to further characterize and compare the two induction methods. Induction by galactose addition at 30°C was superior, indicating the importance of temperature for cell growth and cloned gene expression.
The Solubility of Amino Acids in Mixtures of Water and Aliphatic Alcohols
Authors: Orella C. J. , Kirwan D. J. 
Published: December 2008

AbstractCrystallization is one of the most frequently utilized separation operations in the pharmaceutical industry as a purification step and for producing a solid product with a desired particle size distribution. This crystallization or precipitation is often effected by the addition of a miscible nonsolvent that drastically reduces the solubility of the solute in the mixture. In order to characterize the important phenomena in the crystallization of molecules that have biological significance, we have studied the fundamentals of the crystallization of biochemicals by nonsolvent addition using a model system: the crystallization of amino acids from mixtures of water and aliphatic alcohols.
Displacement Chromatography of Proteins Under Elevated Flow Rate and Crossing Isotherm Conditions
Authors: Subramanian Guhan , Cramer Steven M. 
Published: December 2008

AbstractDisplacement chromatography was employed for the preparative‐scale separation of four‐component protein mixtures. The feed components were both purified and concentrated during the separation process. Protein displacement was successfully carried out at elevated flow rates with minimal effect on bioproduct purity resulting in high bioproduct throughput. The effect of “crossing” adsorption isotherms on the displacement chromatographic process was investigated. Under adsorptive conditions where the protein isotherms cross, the displacement system was unable to separate the feed components. On the other hand, subtle changes in the adsorption conditions readily “separated” the protein isotherms, enabling the purification of the proteins of interest by displacement chromatography. This paper extends the scope of biopolymer displacement chromatography to more complex feed mixtures and elevated flow rates, and demonstrates how protein isotherms can be manipulated to effect the efficient purification of biopolymers by displacement chromatography.