bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and electronic properties of thin fluorite‐structure NiSi2, CoSi2 and FeSi2 interfaces and precipitates in Si
Authors: Wardle M. G. , Goss J. P. , Briddon P. R. , Jones R. 
Published: March 2005

AbstractInterface geometry and electronic properties of fluorite‐structure NiSi2, CoSi2 and FeSi2 layers in {111} oriented silicon are studied using density functional methods. Of the atomically flat geometries studied, NiSi2 is found to preferentially form an interface where the transition‐metal atoms are 7‐fold coordinated, whereas CoSi2 and γ‐FeSi2 both adopt 8‐fold coordinations. Schottky‐barrier heights are detailed for the low energy interface structures of the three disilicides. The localisation of states introduced below the Si valence band and in the band‐gap are detailed for infinite systems, with preliminary results for finite layers simulated by dislocation dipoles also being discussed. Our calculations support the view that gap‐states for silicide precipitates are associated with bounding dislocations rather than the planar interfaces. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CO2 exchange in a temperate Japanese cypress forest compared with that in a cool‐temperate deciduous broad‐leaved forest
Authors: Takanashi Satoru , Kosugi Yoshiko , Tanaka Yumiko , Yano Masato , Katayama Tatsuya , Tanaka Hiroki , Tani Makoto 
Published: March 2005

AbstractTo examine the characteristics of carbon exchange in coniferous forests, we analysed the seasonal and diurnal patterns of CO2 exchange, as measured using the eddy covariance method, in a Japanese cypress forest in the Kiryu Experimental Watershed (KEW) in central Japan. The net CO2 exchange data during periods of low‐friction velocity conditions and during periods of missing data were interpolated. The daily CO2 uptake was observed throughout the year, with maximum values occurring in early summer. Periods of low carbon uptake were seen in late summer owing to high respiratory CO2 efflux. The diurnal and seasonal patterns of daytime CO2 exchange at KEW were compared with those in a cool‐temperate deciduous forest of the Tomakomai Experimental Forest (TOEF) in Japan. The environmental differences between evergreen and deciduous forests affected the seasonal patterns of carbon uptake. Although there were great differences in the mean monthly air temperatures between the sites, the mean monthly daytime carbon uptake was almost equal at both sites during the peak growing period. The carbon‐uptake values at the same PAR level were greater before noon than after noon, especially at TOEF, suggesting the stomatal regulation of carbon uptake.
GABAB receptor subunit mRNAs are differentially regulated in pituitary melanotropes during development and detection of functioning receptors coincides with completion of innervation
Authors: Purisai Maya Gadhvi , Sands Scott A. , Davis Tracy D. , Price Jeffrey L. , Chronwall Bibie M. 
Published: March 2005

AbstractThis study examines the developmental expression of GABAB receptor subunits (GABAB(1a), GABAB(1b), GABAB(2)) in the pituitary intermediate lobe using in situ hybridization, reverse transcriptase‐polymerase chain reaction, immunohistochemistry, and Western blots. Receptor functionality was studied by baclofen‐stimulated GTPγS binding.In the adult rat pituitary all three transcripts were detected in melanotropes, but not in glia, of the intermediate lobe. No transcripts of any subunit were detected in the neural lobe. Transcripts of GABAB(1a) and GABAB(1b), but not of GABAB(2), were detected in specific subpopulations of cells in the anterior lobe. All three transcripts were detected in melanotropes on gestational day 18 using in situ hybridization. Reverse transcriptase‐polymerase chain reactions comparing postnatal day 2 and adult transcript levels in the neurointermediate lobe support in situ hybridization data that GABAB(1a) mRNA levels do not change, GABAB(1b) levels increase, and GABAB(2) levels decrease as the rat matures. Thus, GABAB receptor subunit transcripts are differentially regulated in melanotropes during development. In the adult rat both GABAB(1) and GABAB(2) proteins were detected in the neurointermediate lobe using Western blotting and in melanotropes by immunohistochemistry. Developmentally, GABAB(1) protein was not detected until postnatal day 7, but was clearly expressed by postnatal day 15 while GABAB(2) protein could not be detected until postnatal day 15. Functional receptors were found in the intermediate lobe at postnatal day 15 and in the adult. The demonstration of transcripts for GABAB(1a), GABAB(1b) and GABAB(2) subunits at gestational day 18 contrasted with the failure to detect any protein before postnatal day 7, suggesting that the regulation of GABAB subunit isoforms occurs differentially at both the transcriptional and translational level as development progresses. The disparity in the regulation of the receptor subunits may suggest that GABAB(1) could have other functions besides being part of the GABAB receptor heterodimer.
Chemical Decomposition of Glutamine in Cell Culture Media: Effect of Media Type, pH, and Serum Concentration
Authors: Ozturk Sadettin S. , Palsson Bernhard O. 
Published: March 2005

AbstractThe chemical decomposition of glutamine to ammonia and pyrrolidonecarboxylic acid was studied at 37°C in a pH range of 6.8–7.8 in different media preparations containing various amounts of fetal bovine serum. The media type influenced the decomposition rate, and the first‐order rate constants increased with increasing pH values. The serum concentration had little or no effect on the decomposition rate. The importance of chemical decomposition of glutamine on the analysis of glutamine and ammonia metabolism was illustrated by an example of batch cultivation of a hybridoma cell line. The difference between the apparent uptake rate of glutamine and the actual uptake rate (which is corrected for the chemical decomposition) is shown to be as high as 200%. Similar discrepancy between the apparent and actual ammonia production rate is observed. Mathematical analysis was carried out to develop the relationship between the apparent and actual glutamine uptake and ammonia production rates. The analysis reveals that there are three important dimensionless parameter ratios that govern the difference between the apparent and actual glutamine uptake and ammonia production rates.
Structural Features of Nonionic Polyglycol Polymer Molecules Responsible for the Protective Effect in Sparged Animal Cell Bioreactors
Authors: Murhammer David W. , Goochee Charles F. 
Published: March 2005

AbstractThe nonionic surfactant Pluronic F‐68 polyol is commonly used to protect cultured animal cells from the detrimental effects of sparging. In this study we investigated the structural features of the Pluronic F‐68 molecule responsible for this protective behavior. Poly(oxyethylene)‐poly(oxypropylene) block copolymer polyols of various molecular weights and percentages of hydrophobe (poly(oxypropylene)), including both Pluronic and reverse Pluronic polyols, were considered. The potential toxicity of these agents was examined in the absence of sparging (i.e., in spinner flasks) by using the attachment‐independent Sf9 insect cell line as a model system. Each polyol resulted in one of three distinct types of behavior in these spinner flask experiments: (1) cells lysed at an exponential rate, (2) inhibition of cell growth (i.e., no net cell growth), or (3) uninhibited cell growth. It was then shown that all of the Pluronic and reverse Pluronic polyols that did not inhibit cell growth provided protection from sparging in the bioreactors used in this study; thus, finding a polyol that protected cells was synonymous with finding one that did not inhibit cell growth. The ability of these polyols to protect animal cells in sparged bioreactors was found to correlate well with the hydrophilic‐lipophilic balance (HLB). Those polyols with the largest HLB values were found to be protective agents. These poly(oxyethylene)‐poly(oxypropylene) polyols were also shown to be more effective protective agents than pure poly(oxyethylene); thus, the presence of the hydrophobe (poly(oxypropylene)) is important in their ability to serve as protective agents.
Physicochemical Changes and Rheological Properties of Starch during Extrusion (A Review)
Authors: Lai L. S. , Kokini J. L. 
Published: March 2005

AbstractAmong all flour components, starches play a key role during extrusion. Starch undergoes several significant structural changes, which include gelatinization, melting, and fragmentation. This review focuses on transformations in starch during extrusion and their effect on rheological properties. The effect of extrusion operating parameters, such as residence time distribution, thermal and mechanical energy input and pressure inside the die, and their effect on rheological properties are reviewed. The relationships between rheological properties and extrudate expansion and final extrudate texture are discussed. The dependence of starch viscosity on temperature, moisture content, time‐temperature history, shear rate, gelatinization, and fragmentation kinetics during extrusion are reviewed.
Production of Catechol by a Bacillus stearothermophilus Transpositional Mutant
Authors: Natarajan M. R. , Oriel P. 
Published: March 2005

AbstractThe phenol‐utilizing thermophile Bacillus stearothermophilus BR219 was mutagenized with transposon Tn916 introduced on a suicide plasmid using electroporation. The resulting mutant BR321 carried Tn916 integrated in the resident plasmid pGGO1 and accumulated catechol throughout the growth phase.
Kinetics of Adsorption of Globular Proteins at an Air‐Water Interface
Authors: Narsimhan Ganesan , Uraizee Farooq 
Published: March 2005

AbstractAdsorption of globular proteins at an air—water interface from an infinite stagnant medium was modeled as one‐dimensional diffusion in a potential field. The interaction potential experienced by an adsorbing molecule consisted of contributions from electrostatic interactions, work done against the surface pressure to clear area at the interface in order to anchor the adsorbed segments, and the change in the free energy due to exposure of penetrated surface hydrophobic functional groups to air. The assumption of irreversible adsorption is employed in the present analysis. The energy barrier to adsorption, present at sufficiently large surface pressures, was found to be higher for smaller surface hydrophobicities, larger surface pressures, larger size molecules, and oblate orientation of an ellipsoidal molecule. Consequently, more adsorption occurred at larger surface hydrophobicities, smaller size molecules, and for prolate orientation of ellipsoidal molecules. The subphase concentration has been shown to be zero at short times, increasing with time at larger times, and eventually becoming close to the bulk concentration as a result of increasing energy barrier to adsorption. The predicted evolution of surface concentration with time for adsorption of lysozyme at an air—water interface agreed well with the experimental data of Graham and Phillips (1979a).
Continuous Production of Cell‐Free Recombinant Proteins Using Escherichia coli
Authors: Yu Peng , San Ka‐Yiu 
Published: March 2005

AbstractContinuous production of extracellular recombinant protein using a previously reported periplasmic protein‐release system was successfully demonstrated. The performance of the protein‐releasing system was studied using two types of reactor configuration: a conventional chemostat and a chemostat with a cell‐recycle system. The constitutively expressed α ‐amylase was used as a model protein. In the chemostat experiments, the total α ‐amylase activity increases with decreasing dilution rate—from 135.5 units/mL at a dilution rate of 0.05 h−1 to 2.06 units/mL at a dilution rate of 0.491 h−1. However, the percentage release of α ‐amylase remained relatively constant, at approximately 29%, in the range of dilution rates investigated. The reactor productivity of the target protein reached a maximum of 8.14 units/mL/h at a dilution rate of 0.1 h−1. Application of the releasing system for the continuous production of cell‐free recombinant proteins in a cell‐recycle fermentor was also studied. The reactor performance is significantly better than that of either the chemostat or the batch mode. A total productivity of α ‐amylase at 13.2 units/mL/h with 42% recovery of proteins in the cell‐free form was obtained at a dilution rate of 0.397 h−1 and a bleeding rate of 9.8%.
Viable Cell Recycle with an Inclined Settler in the Perfusion Culture of Suspended Recombinant Chinese Hamster Ovary Cells
Authors: Searles James A. , Todd Paul , Kompala Dhinakar S. 
Published: March 2005

AbstractThe perfusion culture of suspended mammalian cells requires a cell retention device, the best of which will retain all viable cells and reject all nonviable cells and debris. The inclined settler is a passive, simple, inexpensive, and easy‐to‐maintain device that has been shown in the past to selectively remove single nonviable cells of hybridoma cultures. In this work, we have demonstrated the preferential return of viable recombinant Chinese hamster ovary (CHO) cells through the use of a three‐port settler maintained at lower temperatures and vibrated to reduce cell attachment and enhance cell return to the bioreactor. The residence time of CHO cells in the cooled, vibrated settler was determined by flow‐cytometric discrimination of tracer recombinant CHO cells. Cells returning to the bioreactor through the underflow had an average residence time of 1.46 h in the settler. During perfusion cultures with cell densities above 106 cells/mL, cells seen to be stalled within the settler were easily dislodged by periodic air bubbling using a simple back‐flushing procedure in which headspace gas was brought through the settler underflow port. The resuspended cells were returned to the bioreactor within an average of 32 min after bubbling. This study demonstrates that inclined sedimentation technology can be utilized to selectively recycle viable recombinant CHO cells with only a short retention time in an inclined settler.
Optimal Operation Derived by Green's Theorem for the Cell‐Recycle Filter Fermentation Focusing on the Efficient Use of the Medium
Authors: Shimizu Kazuyuki , Furuya Kouji , Taniguchi Masayuki 
Published: March 2005

AbstractOn the basis of the experimental results of Lactobacillus lactis cultivation with cross‐flow filtration, the optimal operation strategy was derived making use of the Green's theorem. It was shown by computer simulation and experiments that optimal operation is superior to the case where the lactate concentration was kept constant, particularly at high cell density cultivation. The performance evaluation was made with respect to the cell productivity for the specified medium.
Clonal Variation in the Spodoptera frugiperda IPLB‐SF21‐AE Insect Cell Population
Authors: Pasumarthy Murali K. , Murhammer David W. 
Published: March 2005

AbstractClones have been isolated from the heterogeneous Spodoptera frugiperda IPLB‐SF21‐AE insect cell population. Five of these clones, in addition to the parent cell line and the SF9 cell line (another clonal isolate of the parent cell line), have been compared in regards to morphology, growth, budded virus synthesis, and recombinant protein synthesis. No significant differences in cell morphology were found among these cell lines. There was, however, a significant difference in the average cell size, with diameters ranging from 9.30 ± 0.184 to 11.11 ± 0.22 μm and from 9.17 ± 0.05 to 11.25 ± 0.24 μm for cells growing in Excell 401 serum‐free medium in spinner flask cultures and in TNM‐FH medium supplemented with 10% FBS in tissue flask cultures, respectively. While no significant differences in the growth rates were found in TNM‐FH medium containing 10% calf serum, significant differences were found in Excell 401 serum‐free medium, with population doubling times ranging from 38.5 ± 6.6 to 64.5 ± 6.4 h in spinner flask studies. Significant differences in expression levels of Escherichia coli β‐galactosidase (β‐gal) were also found in both 12‐well plates and spinner flasks. In the 12‐well plate studies, the peak levels of β‐galactosidase obtained by these cell lines ranged from 0.332 ± 0.091 to 0.805 ± 0.117 mg/106 cells and from 0.580 ± 0.130 to 1.458 ± 0.132 mg/106 cells in Excell 401 and Hyclone Hy‐Q serum‐free media, respectively. In the spinner flask studies, peak expression levels ranged from 0.128 ± 0.053 to 0.573 ± 0.215 mg/106 cells in Excell 401 serum‐free medium. Significant differences were also found in the expression levels of budded virus, which ranged from 64 ± 29 to 1125 ± 521 plaque‐forming units (pfu)/cell and from 67 ± 31 to 233 ± 95 pfu/cell for the wildtype and recombinant (β‐gal) Autographa californica nuclear polyhedrosis viruses, respectively.
A Novel Ultrasonic Resonance Field Device for the Retention of Animal Cells
Authors: Doblhoff‐Dier O. , Gaida Th. , Katinger H. , Burger W. , Groschl M. , Benes E. 
Published: March 2005

AbstractThis article describes two types of flow‐through cell retention devices based on the concept of layered piezoelectric resonators. A single‐chamber device is compared to a novel optimized steam‐sterilizable prototype ultrasonic cell separator with improved acoustic design and an integrated cooling circuit, eliminating the problem of local temperature increase caused by the high amplitudes necessary to achieve the separation of animal cells with low acoustic contrast. This setup yields highly reproducible results and is ideal for studying the long‐term effects of ultrasonic sound fields and separation efficiency. The novel two‐chamber system has the potential for scaleability due to the reduction in thermal and acoustic flow, increased field stability, and separation efficiency. Finally, the effect of power input on separation and cell viability is reported. Such flow‐through cell retention systems could be used as systems to retain biomass within the fermentor or as a substitute for centrifugation, with the major advantage of eliminating high‐speed rotational motion.
Microbial Adaptation to Aluminum
Authors: Appanna Vasu D. , Huang John , Prusak‐Sochaczewski Elzbieta , Pierre Micheal St. 
Published: March 2005

AbstractThe presence of aluminum in a minimal mineral medium, with citrate as the sole source of carbon, elicited the production of an exocellular lipid‐rich residue in Pseudomonas fluorescens. Although aluminum affected the growth rate, no apparent diminution in cellular yield was observed in medium supplemented with up to 3 mM of the trivalent metal. While a 10% reduction in cellular yield was recorded in medium with 7.5 mM aluminum, a decrease of 69% was reported in medium supplemented with 50 mM aluminum at stationary phase of growth. The wet weight of the pellet ranged from 5.9 to 70.3 mg mL−1 of culture in medium supplemented with 1–30 mM aluminum. The trivalent metal was immobilized in this precipitate and associated with phosphate moieties. Both neutral lipids and phospholipids constituted the pellet. More than 90% of the weight of the wet pellet was lost following lyophilization. The percentage of aluminum immobilized increased with the concentration of trivalent metal in the medium. Preconditioned cells showed an improved growth rate, and the cellular yield was slightly higher than for unadapted cells.
Purification by Immobilized Metal Affinity Chromatography of Human Atrial Natriuretic Peptide Expressed in a Novel Thioredoxin Fusion Protein
Authors: Wilkinson David L. , Ma Nien ‐Tung , Haught Chris , Harrison Roger G. 
Published: March 2005

AbstractA fusion protein that contains human atrial natriuretic peptide (ANP) at its carboxy terminus has been genetically engineered with the objective of being able to produce the peptide in a process with a relatively simple purification procedure. The fusion protein also includes a (His)6 metal affinity binding site at the amino terminus, followed by Escherichia coli thioredoxin, a factor Xa protease recognition site, and ANP. With induction of the tac promoter at 30 °C, the expression level of the fusion protein was high (10% of total cell protein as measured by densitometry) and it was almost completely (92%) expressed as a soluble protein in the cytoplasm. A step gradient elution with imidazole of a column of Ni2+ chelated to iminodiacetic acid—agarose saturated with proteins in crude cell extract gave a very nearly pure fusion protein. After digestion of the purified fusion protein with factor Xa protease, ANP of exactly the correct size (to within 2 Da) was observed by coupled HPLC/mass spectrometry.
Issues in the Design of a Multirate Model‐Based Controller for a Nonlinear Drug Infusion System
Authors: Gopinath Ravi , Bequette B. Wayne , Roy R. J. , Kaufman H. , Yu Clem 
Published: March 2005

AbstractMultivariable controller design for the regulation of mean arterial pressure (MAP) and cardiac output (CO) in congestive heart failure patients is restricted by the limited frequency of CO sampling. Performance criteria for the controller specify maximum allowable transient settling times for both variables, and the design should account for the inherent multirate nature of the process in order to satisfy these criteria. We present a multirate model predictive control (MPC) design for MAP and CO regulation by combined infusion of sodium nitroprusside and dopamine, based on a comprehensive nonlinear model of the system. The multirate MPC algorithm is based on nonlinear quadratic dynamic matrix control. To reduce computation time, we introduce a selective linearization technique that linearizes the model on the basis of trends in the plant‐model mismatch. The problem is complicated by restrictions on initial dopamine infusion, prescribed to avoid extremely slow responses. We present a novel rule‐based override (RBO) to the MPC controller that uses a set of heuristics to initialize dopamine. The performance of the MPC/RBO controller is illustrated using simulation results.
Protein—Polyelectrolyte Phase Boundaries
Authors: Mattison Kevin W. , Brittain Isabelle J. , Dubin Paul L. 
Published: March 2005

AbstractThe separation of proteins by polyelectrolyte coacervation or precipitation is based on electrostatically‐driven complex formation. We have investigated complexation between the globular protein BSA and the polyelectrolyte poly(dimethyldiallylammonium chloride) (PDMDAAC) using light‐scattering techniques to monitor solution turbidity. Turbidimetric pH titrations were used to determine the specific pH values where soluble complex formation is initiated (pHc) and where phase separation occurs (pHφ). These values, collected at different ionic strengths, can be presented as phase boundaries. The effects of macromolecular concentration, protein:polymer concentration ratio (r), and polymer molecular weight upon the phase boundary are examined. The macromolecular concentration and polymer molecular weight have little or no effect on the phase boundary. While pHc is independent of r, pHφ varies inversely with r. The use of phase boundaries in the selection of optimal pH and ionic strength for maximum yield and purity in protein separations is discussed.